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IEE REVIEW
Coppers for electrical purposesV.A. Calicut, C.Eng., F.I.M., M.I.Q.A.
Indexing terms: Components, Conductors and conductivity, Physical properties
Abstract: The development of electrical machines was facilitated by the availability of high conductivity copperconductors, and the nonferrous manufacturers are still meeting the requirements of the electrical and elec-tronics industry. Having shown that copper is still in plentiful supply, the review describes over 80 standardisedwrought coppers and copper alloys and 37 casting materials. Compositions are given together with basicmechanical and physical properties in the annealed, worked or heat-treated conditions as appropriate. Machin-ing and jointing techniques are described and the suitability of the materials for end use requirements is dis-cussed. Sources of further information are given.
1 Introduction
Electrical engineering applications account for the largestpercentage of usage of copper. In a very wide variety offorms it is found in nearly every item of electricalequipment. Most of the usage is of high conductivitycopper but when it is required that conductivity be com-bined with other properties such as strength, fabricabilityand resistance to elevated temperatures, alloying additionsare made. This review considers the wide variety ofcoppers, alloyed coppers and copper alloys available foruse in electrical engineering mentioning the appropriateBritish Standards to which they may be ordered.
The methods by which copper is produced haveimproved tremendously in recent years to give betterpurity, consistent quality and greater economy. High con-ductivity copper and the traditional copper alloys retainthe largest sector of the market but many new alloys havebeen developed for specific purposes.
Mention is made of the effect of working processes onproperties and of the preferred techniques for fabrication,machining and joining copper alloys.
The effect of recent developments on certain major enduse applications is described.
2 Recent literature
The situation in the 1960s was surveyed extensively, therehaving been significant progress in the methods of usage ofcoppers in the 15 years since 1945. A symposium on'Copper in the electrical industry' was organised by theCopper Development Association (CDA) in 1960 [1]where the economics of usage of copper in power trans-formers were described by Gee, the use of cooled conduc-tors by Cogle, Hartill and Tudge, the availability of copperalloys for conductivity applications by Richards and theuse of copper as a material for the construction of wave-guides by Hall and Meggs.
In 1962 there was a CDA symposium on the 'Effect ofresearch and design on the use of copper in the electricalindustry' [2] which dealt more with metallurgical develop-ments, with contributions from Bailey (BNFMRA, nowBNF Metals Technology Centre), Moore (InternationalCopper Research Association), Rutherford et al. (Thos.
Paper 4494A, received in final form 9th December 1985. Commissioned IEE ReviewThe author is Project Manager, Materials, Copper Development Association,Orchard House, Mutton Lane, Potters Bar, Herts EN6 3AP, United Kingdom
Boltons and Sons Ltd.) and Scholefield and Waters ofTelcon Metals Ltd. High speed commutators for tractionduties were covered by Law (Brush Electrical EngineeringCo. Ltd.). Much of this work remains valid.
A very useful review of 'Recent developments in proper-ties and protection of copper for electrical use' waspublished by Temple in 1966 [3].
A further CDA Symposium in 1968 [4] included anupdate of the metallurgical scene by Richards and Stam-ford, a review of developments in the forming of copper byBoxall and Mantle (BNFMTC), two papers on themachining of copper by Woollaston and Freudiger, andthree papers on joining procedures, these being on softsolders by Thwaites (International Tin ResearchAssociation), welding by Clews and Young (BritishWelding Research Association) and a general survey byGregory and Nelson (BICC).
At the autumn meeting of the Institute of Metals in1970 the technical programme included 57 useful papersdescribing recent developments in the manufacture andapplications of copper and copper alloys. Of particularinterest to electrical applications were the following, manyof which were subsequently published in the Journal of theInstitute of Metals.
Armstrong-Smith [5, 6] presented, from the refinersaspect, a review of the latest techniques for the productionof primary copper and the influence on the product and itsend uses, highlighting the higher purity of cathode beingproduced. New alloys described included 'A high strengthtin-bronze with improved electrical conductivity' by Ains-worth and Thwaites [7], 'Nickel silver as an engineeringmaterial' by Weldon, Towers and Potton [8], and 'Theproperties of copper-magnesium-zirconium and copper-chromium-zirconium-magnesium' by Opie, Hsu and Smith[9]-
The Southwire continuous rod system for the continu-ous production of wire rod from cathode was described byStevens [10]. This process is one of several which haveeliminated the need for wirebars as intermediate products,and now is believed to have a total installed capacityworld-wide of about 3.3 million tons of copper rod pro-duction per year in 29 plants.
In the early 1970s CIDEC (International Copper Devel-opment Council) published two large loose-leaf volumescompiling a summary of the known data on the manycoppers and copper alloys commonly standardised.Besides a comparison of various national standards, theseincluded comprehensive tables of mechanical and physicalproperties including room temperature tensile, proof stress,hardness, ductility and impact values, short and long term
174 IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
elevated temperature tensile and creep properties andproperties at temperatures below ambient. These were longout of print but the most relevant have been reprintedrecently [11, 12]. In 1974 T.B. Marsden produced a veryuseful review of 'Recent developments in metallurgy andapplications of low-alloy coppers [13] which covered mostof the coppers used for electrical purposes together withthose being developed, mostly in the USA, for special elec-tronic purposes connected with the space programme.
In the later 1970s there was less conference activity butnevertheless a steady stream of technical papers have beenpublished and are referred to elsewhere in this review orlisted in the current CDA Technical Note on 'High con-ductivity coppers — properties and applications' [14].Recent reviews on the state of the industry in India havebeen organised by the Indian Copper Information Centrewith a symposium on 'Copper in electrical industry' in1979 [15] and 'Copper and its alloys in the eighties' in1981 [16].
The last major review of advances in copper and copperalloy production and utilisation was the two-day 'Copper83' organised by the Metals Society (now incorporated inthe Institute of Metals) with the co-operation of others,including the Copper Development Association as part ofthe latters jubilee celebrations. Fifty papers were presentedduring three parallel sessions, many of these being relevantto electrical applications. An extensive summary is given inReference 17. Papers of particular electrical interest werethose on machinability of high-conductivity coppers [18],the usage of copper products in the manufacture of super-conductors [19], the use of shape memory brass in electri-cal and mechanical joints [20], and other applications[21], the properties of the copper-nickel-tin spinodal alloys[22], the development of a possible substitute for copper-silver [23], and the properties of special alloys developedfor the manufacture of semiconductor lead frames andsimilar applications [24], Self-fluxing brazing alloys weredescribed [25] and a design life of one million years wasclaimed for copper sealing techniques developed for thecontainment of radioactive waste [26].
Besides the review-symposia mentioned above, therehas, of course, been a continuous flow of papers relating tothe production, fabrication and usage of copper andcopper alloys in many technical journals which havecovered a very wide range of general and specialised fields.The main ways of gaining access to these is by the'Metadex' index to the Metals Society/American Societyfor Metals database and Metals Abstracts [27], or via theInternational Copper Information Bulletin*.
An overview of the literature mentioned shows that thecopper industry has modernised completely to producematerial of better and more consistent quality by the mosteconomic methods so as to meet the needs of its cus-tomers. The heavy investment required has mainly beenaimed at meeting the existing market demands for close-tolerance high-quality material. The wide variety of new orvaried compositions for copper alloys which have beendescribed have, however, resulted in few new materialswhich are commercially viable at present. Some are,however, filling vital market requirements, especially forthe electronics industry. These will be described later.
3 Copper supplies
Until recently the price of raw copper was subject to fre-quent variation which was very inconvenient to those
* Published three times a year by the Copper Development Association
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
wishing to forecast costs in the long term. Comparisonswere made with the price of aluminium which remainedsteady for a long period of time. The factors which con-trolled these events have now changed however. As theproduction and refining of aluminium is extremely energy-intensive, the cost is rising rapidly with recent rises in thecost of electricity. It is not easy to recycle high conduc-tivity aluminium economically and this makes it difficultto avoid these high energy costs.
Copper is now extracted and refined in many placesthroughout the world as the table of registered brandsshows (Table 1). The large worldwide distribution shown
Table 1 : World copper producers
Continent
Africa
Asia
Australia &Oceania
North America
South &Central America
Europe
Country
South AfricaZaireZambia
Japan
CanadaUSA
ChileMexicoPeru
AustriaBelgium
FinlandFrance
Germany (W)
ItalyNorway
PortugalSpainSwedenUK
Yugoslavia
Numbers ofcopper Brandsreg stered*
14
2
21
"11
5
11
1415
1
Percentage ofWestern Worldprimary coppefproduction
21
8
6
34
26
5
* On the London and/or US metal markets
indicates the large number of sources now being worked.Supplies of copper are therefore now more plentiful andless dependent on political events than was previously thecase.
There are over 160 known types of copper bearing min-erals, based mainly on sulphides. Copper ores are naturallyoccurring mixtures of these minerals with large amounts ofother material, gangue, from which the copper-rich com-pounds must be separated and refined. The copper contentof ores averages less than 1 % but some deposits may runat 2 to 3%. Frequently, other recoverable metals areassociated with copper deposits, notably gold, silver,nickel, lead, zinc and tin. The ores may be worked byunderground or open-cast mining techniques as required.The economics of working any deposit depend, of course,on the investment required, the production costs and theprices obtained for the copper and other by-products.
Traditionally, the extraction of copper starts with thecrushing of the ore to give a fine particle size suitable forbeneficiation by flotation. The copper concentrate is thenfiltered, dried and smelted to a mixture of copper and ironsulphides called 'matte'. By further pyrometallurgical pro-cesses the sulphide is removed from the matte to give'blister' copper which is then fire-refined. Most of thiscopper is cast as anodes for further purification by electro-lytic refining techniques. The cathodes produced are thenremelted and cast to conventional refinery shapes, gener-
175
ally as electrolytic tough-pitch high-conductivity copperwhen required for electrical purposes.
Further details of these and alternative processes areincluded in most standard textbooks on copper, of whichthat by West [18] is one of the most recent.
Besides this primary copper, an important source ofsupplies is secondary copper obtained from recycled scrap.The ease with which copper can be remelted ensures thatthe value of recovered copper remains high, an importantfactor in lifetime costings. Dependent on quality, coppermay be refined or used as the starting material for alloys.
Considerable attention is being given to improvementsin the extraction and refining techniques for copper withthe twin objectives of reducing production costs and givingconsistent improved quality. Many of the recent develop-ments were described during session two of the 'Copper 83'conference [29-33].
From Faraday's mid-19th century requirementsonwards, copper producers have ensured that copper hasbeen produced in quantity and quality suitable for theelectrical industry and developments continue to matchthe needs of modern technology.
3.1 Types of copper available
3.1.1 Electrolytic copper: When cast as refinery shapesfor further fabrication, the coppers are covered by the rela-tively new British Standard 6017: 1981 which has replacedthe BS 1035 series of individual standards for coppers. Asshown in Table 2, which summarises the main require-ments of BS 6017, the old methods of designating copperrefinery shapes have been replaced by the ISO system. Thedesignations for coppers in the wrought form, however,remain unchanged. The sequence of events leading to thenew standard is described in References 34 and 35. Thevast majority of copper used for electrical purposes is thatdesignated 'Cu-ETP' in refinery shape form or 'C101' whenwrought. The full description of the copper is 'Electrolytictough pitch high conductivity copper', usually shortenedto 'electrolytic copper' or even just 'electro'. Originally thecopper will have been refined by the electrolytic process togive cathode of high purity (Cu-Cath). As this cathode is
not suitable for fabrication for reasons of shape andbrittleness, it is remelted and cast to shapes suitable forfabrication: cakes for flat rolling, billets for extrusions andwirebar for rod and wire production. Recently it hasbecome common to cast all of these sections continuouslyrather than in individual moulds. This is especially true ofthe feedstock for production of wire rod which is cast toshape and hot rolled in a continuous process.
The brittleness of the cathod is mainly caused by hydro-gen content, the effects of which are removed by melting,followed by casting with a controlled oxygen content.During static casting the contraction of the metal duringsolidification was balanced by the microporosity caused bythe combination of dissolved hydrogen and oxygen to givesteam. This gave a level 'set' to the casting surface. When atest bar was broken in an elementary quality control test,it showed a 'tough' fracture.
The oxygen content also has a beneficial effect on theconductivity of the copper. When in solution the residualimpurities impair conductivity to a greater extent thanwhen combined with oxygen and present as insolubleoxides. Improvements in refining and melting techniqueshave had a beneficial effect on the conductivity of copper.When the 'International Annealed Copper Standard'(100% IACS) for conductivity of copper was standardisedby the IEC in 1913, it was common for an oxygen contentaround 0.06% to be present to control impurities and cast-ability. Currently the impurity contents are significantlylower so that around 0.02% or less oxygen is sufficient.
Good quality copper now typically has a conductivityof 101.5% IACS in wrought annealed form. As a result ofthe lower oxygen content, the density of copper is nowmore typically 8.91 grams per cubic centimetre (or higher),rather than the 8.89 figure standardised by the IEC.
3.1.2 High grade copper: Apart from the slight improve-ment in properties noted above, the main benefit of theready availability of copper of better purity has been in theability to use improved production techniques for the pro-duction of wire and to produce a consistently uniformproduct, especially enamelled wire.
Fig. 1 Threading the rotor of one of thesix 330 M VA generators at CEGB Dinorwigpumped-storage power stationThe windings are of high conductivity silverbearing half-hard copper to BS 1432 :1970(By permission of GEC Large Machines)
176 IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JVNE 1986
For coil winding the enamelled wire must not retainany 'springiness' but be fully annealed and lie as wound.Consistent good quality means that the annealing tem-perature of the copper is predictably low. The hard wiretherefore anneals uniformly at the temperatures used forbaking enamels, to the benefit of both wire producers andcoil winders.
Fig. 2 Some of the complex wiringbeing installed in Concorde at BritishAerospaceCopper is the only material suitable for theserequirements for power transmission(By permission of B1CC Ltd.)
The existence of this higher grade of copper has beenrecognised by the preparation of a BS Draft for Develop-ment DD78 :1981 for 'Cu-Cath 1', eventually to be incor-porated in BS 6017. This specifies a range of maximumimpurity levels in groups of elements known to havesimilar effects on conductivity. These are included inTable 2 for comparison purposes. Due to the fact thatsome of the impurity maxima specified are near the limitsof detection by conventional analytical techniques and
Fig. 3 Winding the high voltage coil for a 267 MVA, 23.5/432 kVgenerator/transformerThe multiple strip conductors of high conductivity copper are continuously trans-posed(By permission of BICC Ltd.)
Fig. 4 Stator winding for a 6 kV, 32 pole, 1120 kW motor fabricatedfrom annealed high-conductivity copper(By permission of Laurence Scott & Electromotors Ltd.)
1EE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986 177
that it is not easy to get international agreement on com-binations of inter-element effects on conductivity andannealability, it has not yet been possible to include thehigh grade cathode copper in BS 6017 nor to agree asimilar standard for the cast equivalent (Cu-ETP 1).However, a minimum conductivity equivalent to 101.0%IACS is expected to be quoted in a forthcoming BritishStandard for the wire rod used as redraw stock for themanufacture of copper wire and strip.
In the absence of a generally agreed standard methodfor measuring the annealing (or softening) temperature ofhigh purity coppers, a further British Standard Draft forDevelopment has been published: DD 79:1981 'Methodfor performing the spiral elongation test on high conduc-tivity copper'.
Following protracted discussions within the ISO Com-mittee TC/26, the International Wrought Copper Council(IWCC), the High Conductivity Copper Group of theBritish Non-Ferrous Metals Federation and the relevantBSI committees, two new drafts for development havebeen published. The first [36] deals with standard methodsto be used for sampling of cathode copper and the second[37] recommends methods for analysis for the very lowlevels of impurities found in the high grade copper, Cu-Cath-1.
By measuring the extension under load of a spiral ofcopper previously annealed under controlled conditions, agood assessment of annealability can be obtained. Thistype of technique has been in use for quality controlchecks on copper production for some years. By stan-dardising testing conditions, it should now be possible toimprove agreement in results between different labor-atories.
3.1.3 Electrolytic copper refinery shapes (Cu-ETP, CU-Cath 1, Cu-Cath 2): As has been mentioned, it is essentialto melt cathode copper and cast to a shape suitable forfabrication.
Wirebars were previously the usual starting point forthe hot rolling of wire rod. They were generally cast hori-zontally and therefore had an increased concentration ofoxide at and near the upper surface or 'set'. To manufac-ture the best qualities of copper wire, it was usual to scalpoff the set before rolling. It was also necessary to pickle orshave the oxide surface off the hot rolled rod before wire-drawing could start.
It is now possible to continuously cast wirebars verti-cally and cleanly with a flying saw being used to cut themto length. 'Wire rod' is the term used to describe coils ofcopper of 6 to 9 mm diameter which are the starting stockfor wiredrawing. At one time these were limited in weightto about 100 kg, the weight of the wirebars from whichthey were rolled. Flash-butt welding end-to-end wasnecessary before they could be fed into continuous wire-drawing machines.
It is now more general practice to melt cathodescontinuously in a shaft furnace and feed the molten copperat a carefully controlled oxygen content into a contin-uously formed mould which produces a feedstock leddirectly into a multistand hot rolling mill. The continuousoutput of this is cut to convenient coils of several tonsweight each. For subsequent wiredrawing, these go to highspeed rod breakdown machines which carry out interstageanneals by electric resistance heating of the wire at speedin line. This has superseded previous batch annealing tech-niques and shows considerable economies given the consis-tent quality of copper described previously. The mostpopular type of continuous casting and rolling technique is
by 'Southwire' process. Other processes producing goodquality copper rod include the General Electric, Properzi,Contirod, Outokumpu and other variants [39-41].
For the production of conductors of larger section thanwire, extrusion from billets is the usual production process.The billets, approximately 200 mm diameter, are cast forsubsequent extrusion to rod and bar. Normally these arecut to no more than 750 mm in length to fit the extrusionchamber and this controls the maximum pieceweight ofextrusion which may be made. Extrusions are usually sub-sequently drawn to the required finished sizes by one ormore passes through drawblocks. This is the process usedto produce many sizes of winding strips, busbars, rotorbars and commutator section. Good descriptions of extru-sion techniques have been given by Attrill [42] andWatson [43]. Extruded rod is frequently also the feedstockfor forgings and stampings. The fabrication of these inhigh conductivity copper and copper alloys has beendescribed by Woollaston and Stamford [44].
Cakes (or slabs) are used when flat plate, sheet, stripand foil are required. They are now also mostly cast con-tinuously which has given an improvement of pieceweight,yield and quality over the previous static casting methods.Copper is commonly hot rolled from 150 mm thicknessdown to about 9 mm and cold rolled thereafter. Modernproduction processes for copper and copper alloy sheetand strip have been described by Adlington [45].
3.2 Other refinery coppersBesides the cathode and electrolytic grades of copper listedin Table 1, other types of refinery coppers are available.
3.2.1 Fire refined high conductivity copper (Cu-FRHC):This process involves the oxidation of impurities frommolten copper and the subsequent reduction of the highoxygen content by 'poling': the insertion of green treetrunks into the melt.
With the demise of the majority of equipment for firerefining copper without subsequent electrolytic treatment,there is much less copper made to this specification. Themore common electrolytic tough pitch copper conforms tothis specification and is frequently supplied as such. Forapplications requiring some resistance to softening con-ferred by the higher impurity content but less than thatconferred by alloying additions, this material may proveadequate.
3.2.2 Fire refined tough pitch copper (Cu-FRTP): Iningot form, this copper provides the feedstock for castingsand is also suitable as the basis for certain alloys.
3.2.3 Phosphorus deoxidised copper (Cu-DHP): Con-ventional electrolytic tough pitch copper which containsoxygen is susceptible to embrittlement by 'gassing' ifheated in a reducing atmosphere. Hydrogen diffuses intothe copper, reduces the oxide and produces steam which,being not condensable above 314°C, expands, forming thecavities and cracks which disrupt the metal. Conditionsunder which tough pitch coppers can safely be annealed orused in hydrogen-cooled machines have been evaluated[46-47]. If, however, copper is to be heated in a fullyreducing atmosphere, the embrittlement effect can beavoided by the use of a deoxidised copper, and phos-phorus is the most common deoxidant used. In Cu-DHPthe phosphorus range is from 0.013 to 0.05%, this beingsufficient to guarantee freedom from the possibilities ofembrittlement. There is a deleterious effect on conductiv-ity, this being reduced to about 92% IACS at 0.013%
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
phosphorus and about 73% IACS at 0.05%. However, oneadvantage of this material is that, in sheet form, theabsence of oxide stringers gives it much improved deepdrawability.
By itself a phosphorus content lower than 0.013% is nota guarantee that oxygen is not present; if the metal has notbeen cast under very carefully controlled conditions, it isstill possible for there to be sufficient oxygen present forthe material to fail the hydrogen embrittlement test [48].Coppers with a phosphorus content lower than 0.013%have not, therefore, been included in British Standards.
3.2.4 Oxygen free coppers (Cu-OF and Cu-OFE):Copper can be melted under closely controlled inertatmosphere conditions and poured to give a metal sub-stantially free from oxygen and residual deoxidants, thuscombining good conductivity with resistance to embrit-tlement under reducing conditions. Without the alleviatingeffect of oxygen, any impurities present can have a dele-terious effect on conductivity and they are therefore keptto a minimum.
For electronic applications in high vacua where novolatiles can be tolerated the high purity 'certified' grade,Cu-OFE (wrought designation C110) is used [49]. Theoxide film on this copper is strongly adherent to the metal,which makes it a suitable base for glass-to-metal seals. Anexample of the use of this copper as the base for a semi-conductor device is shown in Fig. 5.
Fig. 5 Electrical components made from OFHC® oxygen-free high-conductivity copper and AMSIL® silver-bearing oxygen-free high conduc-tivity copper(By permission of Amax Copper Inc.)
3.3 Addition of other elements to copperThe effect of most impurities in, or intentional additionsto, copper is to increase the strength and softening resist-ance but to decrease the conductivity [50-51]. The effectson both electrical and thermal conductivity can usually betaken as proportional; the effect on electrical conductivitybeing, usually, easier to measure. The extent of the effectsdepends on the extent to which the addition is soluble incopper and the amount by which the copper crystal latticestructure is distorted and hardened by the solute. A verywide variety of possibilities exists for single and multipleadditions of elements to attain properties suitable for dif-ferent applications. These additions are generally aimed atgiving material of economic optimum strength, hardness,creep, fatigue or other properties. These coppers and cop-per alloys normally considered to be 'high conductivity'are listed in Table 7. This includes the common unal-loyed coppers, the 'free machining' coppers and the higher
strength coppers, some of which require heat treatment togain full strength.
3.3.1 Copper-silver (Cu-Ag): The addition of silver tocopper raises its softening temperature considerably withvery little effect on electrical conductivity. Silver alsoimproves the mechanical properties, especially the creep
Fig. 6 Complex commutator sections blanked from extruded and drawntapered strip of high conductivity copper and silver-bearing copper(By permission of Thomas Bolton & Johnson Ltd.)
resistance [52]. The material is therefore preferred whenresistance to softening is required, as in commutators, orwhen expected to sustain stresses for long times at elevatedworking temperatures, as in large alternators and motors.Because it is difficult to control the oxygen content ofsmall batches of copper, this product is normally producedby the additions of silver or copper-silver master alloy justbefore the pouring of refinery output of tough pitchcopper. It is therefore regarded as a refinery product ratherthan a copper alloy.
Previously, the silver addition was agreed between sup-plier and purchaser but it is now possible to select from arange of preferred minimum additions for suitable applica-tions. A minimum of 0.01% of silver facilitates the pro-duction of transformer and other winding strips with acontrolled proof stress. Where a significant increase increep properties is required with minimal additions ofsilver, the 0.03% minimum should be selected and this is
Fig. 7 Copper components
Formed from extruded and/or forged slock, Ihese busbar components, cable termi-nations, commutator sections and gas mixers may be machined from electrolytictough pitch, silver-bearing or free-machining grades (C101, C10I + Ag, or C l l l ) asrequired(By permission of Thomas Bollon & Johnson Ltd.)
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986 179
Table 2. Chemical composition requirements of coppers
Designation
As cast
BS6017
Cu-CATH-1*
Cu-CATH-2
Cu-ETP-1*
Cu-ETP-2
Cu-FRHC
Cu-FRTP
Cu-DHP
Cu-OFCu-OFECu-Ag-1
Cu-Ag-2
Cu-Ag-3
Cu-Ag-4
Cu-Ag-5
Cu-Ag-OF-2Cu-Ag-OF-4
PreviousBS
1035
1036
1037
1038
1172
18611954
Whenwrought
C100
C101
C102
C104
C106
C103C110C101
C101
C101
C101
C101
C103C103
CopperplusSilver
% min.
99.90
99.90
99.90
99.85
99.85
99.95
99.90
99.90
99.90
99.90
99.90
99.9599.95
Copper
% min.
99.99
Silver
% min.
0.0025
0.0025
0.01
0.03
0.06
0.09
0.14
0.030.09
o.cQ.
O
Q.
(2)
(2)
0.013/0.05
0.0003
'ca>
0.0005(2)
0.0005(2)
0.02
0.05
t
coSc
0.0004(2)
0.0004(2)
0.005
0.01
t
5Em
(D0.0010
0.0001(1)0.0010
0.0025
0.0030
0.0030§
0.00100.001 Of0.0010
0.0010
0.0010
0.0010
0.0010
0.00100.0010
£
•a
O
(2)
(2)
0.0001
* Provisional: see BS Draft for Developmentt Total of these seven elements not to exceed 0.004%•ft Analysis required, no limit established§ Should the copper be required to undergo severe fabrication in the temperature range 400°C to 700°C this fact should beindicated by the purchaser and in such cases the bismuth content shall not exceed 0.0015%
frequently specified for heat exchanger strip. For applica-tions requiring good softening resistance during soldering,such as commutators, 0.06% silver is required. The 0.14%grade gives very good resistance to creep, as has beenshown in the results of recent research work by the BNFMetals Technology Centre [53]. It is therefore suitable foruse as highly stressed rotor winding strips.
The additions are commonly made when required intough pitch copper. Where embrittlement resistance is alsorequired, without the loss of conductivity caused by deoxi-dants, they can be specified in oxygen-free coppers. Apartfrom a greater rate of work hardening and, of course, theneed for higher annealing temperatures, copper-silvers maybe worked and fabricated as for conventional tough pitchcopper.
Although silver additions are mostly made to toughpitch copper (C101), it can also be added to other copperssuch as C102 to C106. The BS designation is not changedso that on ordering the silver content is stated separately.
3.3.2 Free-machining coppers: While tough pitch, deoxi-dised and oxygen free coppers can all be machined withoutgreat difficulty [18], their machinability is less than that ofthe standard by which all metals are compared, free-machining brass. Being relatively soft, copper may tend tostick to and build up on the cutting edges of drills and
180
other tools. The addition of an insoluble second phase cangive much improved machinability without a greatly del-eterious effect on conductivity. Sulphur, tellurium, sele-nium and lead are examples of possible additions. Most of
2.1 rTi PCoFeAs Si Mn GeCrNbYSbAl Sn Mg
0 0.05 0.1 0.15 0.2 0.25concentration of impurity, "A, (by mass)
Fig. 8 Effect of added elements upon the electrical resistivity of copper
1EE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
All limits are maxima except where range shown Totalimpurities
0.0010 0.0005(4) (3)
0.005
0.0010 0.0005(4) (3)
0.005
0.005
0.01 0.010
0.030 0.010
0.005tt 0.0010
0.005
0.005
0.005
0.005
0.0050.0050.005
(2)
(2)
(4)
(4)
0.05 0.10
0.10
0.0002(1)
0.0002(1)
0.020
0.0015(5)
0.0010
0.0002(1)
0.0002(1)
0.010
(4)
(4)
0.01
0.01
(4)
(4)
0.001 0.0011 0.0018 0.0011 0.0001
0.00650
0.03 excl.O2 + Ag0.00650
0.03 excl.0 2 + Ag0.04 excl.O2 + Ag0.05 excl.O2,Ni,AgSe + Te 0.0200.060 excl.Ag,As,Ni,P0.03 excl. AgSee footnotet0.03 excl.O2
0.03 excl.O2
0.03 excl.020.03 excl.0 20.03 excl.020.030.03
0 For Cu-CATH-1 and Cu-ETP.1 impurity limits shall not exceed the following group totals:Group Number
(1) Bi + Se + Te 0.0002%(2) As + Cd + Cr + Mn + P + Sb 0.001 5%(3) Pb 0.0005%(4) Co + Fe + Ni + Si + Sn + Zn 0.0020%(5) S 0.0015%(6) Ag 0.0025%
these are otherwise undesirable impurities and give adegraded scrap value. The preferred addition is thereforesulphur, 0.3 to 0.6% being satisfactory for most purposesin a deoxidised copper with a low residual phosphorus.With this addition the hot and cold ductility of the copperis reduced to some extent, but the material is available ascast and in wrought form as rod, bar and forgings. Infor-mation on the machining of this and other coppers andcopper alloys is available in Reference 54.
3.3.3 Copper-cadmium: As can be seen from Fig. 8, theaddition of cadmium does not reduce the conductivity ofcopper as much as many other elements. Where the extraexpense of silver additions cannot be justified, it has been apreferred addition for many years where higher strengthand softening resistance is required. The alloy has rela-tively good cold ductility and can therefore be drawn towire or flat rolled without difficulty. Examples of typicalapplications are for the overhead collector wires in thecatenery systems of railways, for trolley wires, for tram-ways, telephone wires and, when rolled to thin strip, forthe fins of automotive radiators and other heat exchangers.
The usual level of cadmium is 0.5 to 1.2%. Whenmolten, copper cadmium alloys give off toxic fumes, andfume removal and cleaning equipment is essential for safefoundry operation. Where manufacturers are so equipped,
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
the continuity of supply of the material is assured.However, alternatives are being investigated which meetsome of the properties of copper-cadmium. These includeadditions of tin, magnesium, silver, iron and phosphorus inbinary, ternary or quaternary alloys.
3.3.4 Heat treatable alloys: Many of the high strength,good conductivity copper alloys owe their properties tothe fact that their composition is controlled to be justoutside the solid solubility limits of the added alloyingadditions. By a solution treatment typically at about1000°C dependent upon alloy and section size, followed bya water quench, the alloying elements are retained in solidinto solution. In this state the alloys can be most easilyfabricated but, because of high internal strain, the conduc-tivity is lowered. Precipitation treatment (aging) is effectedat about 500°C dependent upon the type of alloy, sectionsize and time at temperature. These heat treatments arecarried out generally in air furnaces, there being norequirement for close control of the atmosphere. Excessiveoxidation should, of course, be avoided.
The best conductivity values are obtained with thematerial after full solution and precipitation heat treat-ments. For optimum mechanical properties it is usual for10 to 30% of cold work to be required while the material
181
is in the solution treated state. For the highest tensileproperties further cold work can be carried out after aging.
For some applications a low beryllium alloy is pre-ferred. This contains around 2.5% cobalt (plus nickel) and
Fig. 9 Overhead catenary conductorwires are made from hard drawn high con-ductivity copper or copper-cadmium(By permission of British Rail)
Fig. 10 Resistance welding electrodes made from copper-chromium heattreated to give suitable hardness and heat resistance combined with ductilityand conductivity(By permission of Delta Enfield Metals)
Fabrication of these alloys by welding or brazing, attemperatures above that for aging, results in loss of mech-anical properties. The full cycle of solution for precipi-tation heat treatment will not restore original properties ifit is not possible to include the required deformation bycold work between treatments. Advice regarding the selec-tion and fabrication of these alloys can be obtained fromthe manufacturers or the CDA.
(a) Copper-beryllium alloys:The most important of the copper-beryllium alloys containfrom 1.5 to 2.7% beryllium. For the most extensivelywrought materials such as springs and pressure-sensitivedevices, the lower end of the range is preferred, but for diesthe extra hardness attained at the upper end of the range isexploited. To improve properties an addition of nickeland/or cobalt is also commonly made. These alloys areused because of their great strength and hardness which isattained by combinations of heat treatment and cold work.As can be seen in Table 2, the conductivity of the materialis reduced, but it is preferred for many specific applica-tions. Along with the strength at ambient and elevatedtemperatures, very good fatigue resistance, spring proper-ties and corrosion resistance were obtained.
only 0.4% beryllium. The strength obtained is not quite sohigh, but it remains a good compromise material for somepurposes requiring strength but greater ductility. As theprecipitation hardening temperature is about 100°Chigher, it can also be used at higher temperatures (up to350-400°C) without risk of over-aging. The electrical con-ductivity is also slightly better. These alloys propertieshave been described [55-57] and further information isavailable in manufacturers' literature.
The optimum heat treatment conditions for these alloysdepends upon the properties required, the size of the com-ponents and the extent of any cold work. Advice on thesematters should be sought from the manufacturers.
Beryllium vapour is known to be toxic, and suitableprecautions must be employed when it is likely to beencountered and especially during the melting or weldingof copper-beryllium alloys. Fabrication in the solid statemay not involve such a hazard and nor may machining inan adequate supply of lubricant which prevents overheat-ing. Where a hazard does exist, efficient fume removal andtreatment facilities must be employed.
(b) Copper-chromium:This type of alloy is the most frequently used highstrength, high conductivity material. The chromiumcontent is usually between 0.3 to 1.2%. Other elementssuch as silicon, sulphur and magnesium may be added tohelp to improve the properties further or to improvemachinability. Copper-chromium alloys can be made in allfabricated forms but are mostly available as rod, bar orforgings. In the molten state the added chromium, likemany other refractory metals, oxidises readily, increasingthe viscosity of the liquid and causing possible inclusionsin the casting, but the alloy can be readily cast by found-ries with the required expertise.
Copper-chromium alloys are commonly used in rodform for spot welding electrodes, as bar for high strengthconductors and as forgings for seam welding wheels andaircraft brake discs. As castings they find applications aselectrode holders and electrical termination equipmentwhere the shape required is more complex than can beeconomically machined. In rolled plate form copper-
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
chromium is recommended for the walls of the mouldsused for continuous casting of steels and coppers whichrequire good conductivity, strength, hardness, abrasionand corrosion resistance. In sheet and strip form it is suit-able for the finstock for heavy duty heat exchangers andhas also been considered for use in multiplate clutches. Foruse as rotor bars and rotor rings of heavy-duty electricmotors, where very high reliability is required, it is recom-mended that an addition of magnesium is used to over-come a loss of ductility at around 300°C [58].
(c) Copper-chromium-zirconium:Some improvement in the softening resistance and creepstrength of copper-chromium may be gained by the addi-tion of 0.02 to 0.2% zirconium. Although not generallyavailable cast to shape, the alloy is available in wroughtproduct forms similar to those of copper-chromium alloysand is used in similar applications.
Copper-zirconium is an alloy with slightly differentproperties [59]. It is not readily cast to cake or billet formwithout the use of a controlled atmosphere above the melt.It is therefore not generally available commercially. Formost purposes the properties of copper-chromium alloysare superior. Other developments in this type of alloy arebeing reported [60] and materials may soon be availablewith improved strengths without further loss of conduc-tivity. These are initially aimed at special applications inthe electronics and avionics industries, such as brazablebases for solid state devices, high reliability solderlesswrapped connectors and critical switch and commutatorrequirements.
(d) Copper-nickel alloys:The usual 90/10 and 70/30 copper-nickel alloys with theircombination of strength, corrosion and biofouling resist-ance are in considerable use in heat exchangers. Their usefor electrical purposes is limited however, but two special-ised copper-nickel alloys can be described. Both are heattreatable. /
(i) Copper-nickel-silicon with a nominal composition of2.5% nickel, 0.5% silicon is available as castings, forgings,rod and bar with good strength and reasonable conduc-tivity. Applications exploit wear resistance of this alloy andinclude electrode holders, seam welding wheel shafts, flashor butt welding dies and ball and roller bearing cages.
(ii) Copper-nickel-phosphorus alloys with a nominal 1%nickel and 0.2% phosphorus, are not so strong as thecopper-nickel-silicon alloy but have better conductivityand ductility. They are used for electrode holders, clampsand terminations in cast and wrought forms.
(iii) Copper-nickel-aluminium-silicon is a proprietaryalloy containing about 5% of nickel and 0.8% each of alu-minium and silicon available as strip for electrical springapplications in a range of tempers intermediate betweenthose of the phosphor bronzes and beryllium copper.
(iv) Copper-nickel-tin: A range of five proprietary alloyshas been developed containing from 3.5 to 15% nickel and3.5 to 8.5% tin. After solution treatment they are aged togive an internal structure of spinodally decomposed mar-tensite which can give properties as high as those of beryl-lium copper (tensile strength up to 1400 N/mm2). They arenot yet commonly available in European markets.
3.4 Other copper alloysAlthough not specifically designated for electrical pur-poses, many other wrought copper alloys are commonly inuse in electrical equipment. These include the brasses,phosphor bronzes, nickel silvers and aluminium bronzes,
the designations and available forms of these materials inwrought forms being shown in Table 4a. Although not of'high conductivity' their electrical properties are neverthe-less very useful, being better than most other metals. Theiruse is controlled by their wide variety of properties such asformability, machinability, strength, springiness, corrosionresistance and cost. The versatility of the large number ofbrasses available for electrical applications is described inReference 61.
Cast copper and copper alloys are also frequently usedin items of electrical equipment where the process can beused to provide components of complex shape at competi-tive costs. These can range in size from die castings weigh-ing a few grams to large components of several tons.
The conductivity of cast pure copper is generally notquite as high as that of wrought copper of similar com-position. As components are normally cast in relativelymassive form for inclusion in large assemblies, theirstrength is frequently of more importance. For excellentstrength and conductivity the heat treatable copper-chromium alloy is available. For other purposes whereother properties are equally important, such as bearings,other alloys are used. Compositions standardised inBS 1400:1985 [62] are summarised in Table 4b. Rec-ommendations for usage are included in the appendices toBS 1400. These are given in greater detail in the pub-lication 'Copper alloy casting design' [63] which alsoemphasises the important need for good liaison betweendesigners and foundries during the creative stages for com-ponents.
4 British Standards for copper andcopper alloys
Used as the main basis for commerce, the British Stan-dards are generally suitable for use as published. Forspecial purposes they may be used as the basis for a stan-dard which also includes other requirements suited to par-ticular end uses.
Following active British participation in the discussionswithin the International Standards Organisation (ISO) ourstandards are, where practicable, being harmonised withISO standards for compositions, properties and tolerances.This has the advantage of ensuring closer agreement withother standards, for example, the German (DIN), French(AFNOR), Swedish (SIS) and, to some extent, the Amer-ican (ASTM).
BSI committee NFM/34 is responsible for the standardsfor the coppers and copper alloys suitable for both generalpurposes and electrical purposes. Revision of many ofthese is being undertaken at present with the intention ofintroducing a loose-leaf format to permit the easy presen-tation of common clauses and economic, efficient updat-ing. As mentioned previously, the main compositionalstandard for coppers is now BS 6017 'Copper refineryshapes'. For general purposes, the BS 287x series is usedfor various wrought product forms for the coppers andcopper alloys.
BS 2870: sheet, strip & foilBS 2871: tubes (in three parts)BS 2872: forging stock & forgingsBS 2873: wireBS 2874: rod (other than forging stock)BS 2875: plate
To a certain extent the electrical material standardsinclude the relevant requirements for general purpose
1EE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
materials but add necessary extra clauses relating to con-ductivity and other details. These are listed in Table 3.
Table 3: Some British Standards for coppers for electricalpurposes
BS Subject
23 Copper and copper cadmium trolley and contact wire for elec-tric traction
125 Hard drawn copper and copper-cadmium conductors for over-head power transmission purposes
159 Busbars and busbar connections174 Hard drawn copper and copper-cadmium wire for telegraph
and telephone purposes176 Copper binding and jointing wires for telegraph and telephone
purposes1432 Copper for electrical purposes, strip with drawn or rolled
edges1433 Copper for electrical purposes, rod and bar1434 Copper for electrical purposes: commutator bar1977 High conductivity copper tubes for electrical purposes3839 Oxygen-free high conductivity copper for electronic applica-
tions4109 Copper for electrical purposes: wire for general electrical pur-
poses and for insulated cables and cards4393 Tin or lead-tin coated copper wire (for electronic purposes)4577 Materials for resistance welding electrodes and ancillary
equipment4608 Copper for electrical purposes: rolled sheet, strip and foil
The above are the main material standards. Many otherproduct standards call for the types of wrought or castcoppers designated in Table 4 which summarises the exist-ing designated coppers and copper alloys either includedat present or likely to be included in the near future. Allmaterials have been tabled including those for which noelectrical properties have yet been specified, as many ofthese find use in electrical applications requiring the suit-able combination of strength, ductility, corrosion resist-ance and conductivity obtainable in copper alloys.
In the near future, work will be started within ISO onstandardising coppers for electrical purposes. Followingdiscussions with the International Electrotechnical Com-mission, the scope of this work has been agreed. Broadly, itwill be confined to compositions, mechanical propertiesand tolerances in a similar fashion to the existing stan-dards for coppers for general purposes, but with attentionpaid to meeting the special requirements of the electricalindustries and with good liaison with the IEC and itsmany national member bodies including the British Elec-trotechnical Commission.
The chemical compositions and code numbers of thosealloys, which are included in the above standards, arelisted in Table 4. To quote a material to a British Standardit is first necessary to quote the British Standard Numberand to follow this by the appropriate Code Number. Thiselectrolytic high conductivity sheet would be ordered toBS 2870-C101 or, for electrical purposes, to BS 4608. Nor-mally a temper designation, selected from the standard,would be added to specify the required mechanical proper-ties. Table 4, derived from BS 2870-BS 2875, is repro-duced by permission of the British Standards Institution, 2Park Street, London W1A 2BS, from whom completecopies of the individual standards may be purchased.
The 'nearest ISO designation' is derived from thedesignation system described in ISO 1190 Part 1. It doesnot necessarily imply that such an alloy is included in ISOstandards but facilitates comparison with other nationalstandards which use the ISO designation system. Com-positions and product forms other than those shown maybe available from manufacturers to special order.
British Standards 2871 to 2875 are currently in theprocess of revision. In the relevant columns, alloys which
184
are likely to be proposed for inclusion have been addedand alloys either not now being made in significant ton-nages or being superseded by other materials, have beendeleted.
Table 4 shows the coppers and copper alloys allocatedBritish Standard designations. The products available assemi-finished wrought products are shown in Table Aawhich lists the wrought forms available in the BS 2870-2875 series of standards. These are for general engineeringpurposes and, except when the highest of conductivities arerequired, are those normally used for materials for electri-cal components.
C101 and other high conductivity coppers are thoseusually called up in the main standards for coppers forelectrical purposes. While the conductivity of C101 isaffected only slightly by severe cold working (a loss ofabout 3%), retained internal stresses have a greater effecton the alloys and typical conductivity figures are thereforenot valid. Manufacturers will be pleased to quote typicalvalues for given alloy compositions at specified hardnesstempers. Such data is also contained in the CDA TechnicalData Publications [11, 12].
For the available casting alloys in Table 4b, typicalconductivities are quoted from BS 1400.
Actual compositions and mandatory properties are con-tained in the quoted British Standards. Product rangesand typical properties are detailed in CDA Technical NoteTN 10 'Coppers and copper alloys: compositions andproperties' [64].
5 Availability
Table 4 shows the forms in which each of the high conduc-tivity coppers and copper alloys are usually available frommanufacturers. Smaller quantities can best be obtainedfrom stockists who hold the popular compositions andsizes. General guidance on common availability is:sheet C101, C106 in width and length modules of
300 mm (or 1 ft.) up to1800x900 mm (6 ft. x 3 ft.)in a variety of mm (or SWG)thicknessesSheared to width as requiredin a variety of mm (or SWG)thicknesses. Maximum coilweights in kg per mm width byarrangementby arrangementin OD and wall thicknesses sel-ected from the appropriate sec-tions of BS 2871straight lengths in a variety ofmm sizes up to 100 mmin preferred sizes as shown inBS 1432 and 1433 with orwithout radiused edgesin a variety of sizes up to75 mm across flatsplain or tinned in a large num-ber of superfine, fine and largermm sizes selected fromBS 4109
All other materials are available from specialist stock-holders or directly from the manufacturers. When a manu-facturer is unable to supply quantities from stock, he maybe able to recommend stockists known to hold stocks ofspecified or equivalent products. Note that C101 (Cu-ETP)
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
strip andfoil
platetube
rod
rectangularbaror strip
hexagonalbar
C101,
C106C106
C101,
C101
C101,
C106
cm
cmC101
may be commonly referred to as 'electro' copper and C106(Cu-DHP) as 'deox' or 'DONA'.
6 Physical and mechanical properties of coppers
6.1 Physical propertiesThe basic physical properties of electrolytic tough pitchhigh conductivity copper are shown in Table 5.
6.2 Electrical properties of refinery coppers (Table 6)Because it can be most accurately measured, the manda-tory electrical property for high conductivity copper isnow mass resistivity, for which the unit ohm g/m2 is used.It is shown in BS 5714 that the error in measurement ofmass of small sections, such as wire or strip, is likely to beless than that for volume. The use of volume measure-ments quoted in IEC publication 28 assumes a standarddensity for copper in the wrought form used for the test of8.89 grams per cubic centimetre. This was valid when orig-inally published in 1913 when oxygen contents were typi-cally 0.06%. With modern coppers containing around0.02% oxygen, the density is nearer to 8.91 grams percubic centimetre [65]. For oxygen free coppers, 8.94 gramsper cubic centimetre is more realistic.
The equivalent values given for volume resistivity andfor conductivity are interpreted using the IEC standarddensity value of 8.89 grams per cubic centimetre whichmay be subject to revision. Conductivity values are shownin both SI units of Siemens per metre and '% IACS(International Annealed Copper Standard)', the traditionalway of comparing the conductivity of other metals andcopper alloys with high conductivity copper. With theimprovements in purity previously mentioned, most com-mercial high conductivity copper has a conductivityaround 101.5% IACS in the annealed state. Work hard-ened material will have a lower value due to internal straineffects. Cast material also has a lower value due to grainboundary and porosity effects.
6.2.1 Effect of temperature on resistivity and resistance:As with all metallic materials, the resistivity of copperincreases with increasing temperature. Thermal changes ofresistivity can be found from the usual formula:
P2 = Pi(l+p9) (1)
where
Pi = resistivity at temperature 1p2 = resistivity at temperature 2/? = temperature coefficient of resistivity
for the relevant temperature range9 = change of temperature
The temperature coefficient of resistivity, /?, itself changeswith temperature. For copper its value at any temperatureabove — 200°C can be taken as
1233.54 + T
(2)
where T is expressed in °C.When calculating thermal changes of resistivity for
small temperature ranges, the value of jl at the lower tem-perature is often assumed to be constant over the range.
Typical values at 20°C for copper of p and ft are:
p2o — 1.707 piSl cm/?20 = 0.003947/°C
Thermal changes of resistance for a particular copper con-ductor can be similarly calculated from
R2 = ^ ( 1 + a0) (3)
where a at any temperature above — 200°C can be taken
1234.45 + T
Hence at 20°C, a = O.OO393/°C
(4)
6.2.2 Effect of cold work on resistivity: The effect ofretained stresses on resistivity is noticeable but not toogreat. Hard temper high conductivity coppers show a 3%increase in resistivity compared with annealed copper.
6.2.3 Thermal conductivity: The effects of all variables onelectrical conductivity may usually be assumed to havesimilar effects on thermal conductivity properties.
6.2.4 Effect of impurities and minor alloying additionson conductivity: The effect of some added elements onelectrical conductivity of copper is shown in Fig. 8. This isonly approximate as the actual effects are varied bythermal and mechanical history of the copper, by oxygencontent and by other inter-element effects. Most of the ele-ments shown have some solubility in copper and their pro-portionate effect is a function of difference in atomic size aswell as other factors. Elements largely insoluble in copperhave little effect on conductivity. As they are present asdiscrete particles, they can confer better machinability inhigh conductivity copper.
The effect of oxygen can be beneficial as some impu-rities may then be present as insoluble complex oxidesrather than being in solid solution in the metal.
At lower concentrations than those shown, the effect ofindividual impurities on conductivity is less easily mea-sured because of the difficulty of eliminating inter-elementeffects and an increased effect of prior mechanical andthermal treatment on the extent to which elements may bein solution. The curves shown should not, therefore, beextrapolated backwards towards 'parts-per-million' figures.
6.3 Mechanical propertiesTypical mechanical properties of wrought coppers andhigh conductivity copper alloys are shown in Table 7.These figures can only be taken as an approximate guide,as they vary with the product form and the previousmechanical and thermal history. For actual minimumvalues to be specified the appropriate British Standardsshould be consulted regarding the product form andtemper designation required. Shear strength may beapproximately taken as two thirds of the tensile strengthfor many of these materials.
The 'softening temperature' as defined in BS 4577 isquoted to give an indication of performance at elevatedtemperatures.
For more detailed information on the mechanicalproperties of coppers and copper alloys there are manysources available. In the early 1970s the InternationalCopper Development Council (CIDEC) of Genevapublished a two-volume loose-leaf handbook summarisingall known data for the commonly specified coppers andcopper alloys. This has been unavailable for some time butthe relevant sheets for the high conductivity coppers andcopper alloys have been reprinted by the CDA [11], ashave those for the brasses [12]. These give a compendium
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986 185
Ta
ble
4.
Bri
tis
h S
tan
da
rd c
op
pe
rs a
nd
co
pp
er
allo
ys,
de
sig
na
tio
ns
an
d f
orm
s c
om
mo
nly
av
ail
ab
le
a W
roug
ht m
ater
ials
BS
des
ig-
Mat
eria
l des
crip
tion
natio
n IS
0 d
esig
natio
nt
Nom
inal
com
posi
tion
28
70
S
peci
fied
in B
S
2871
2
87
2
2873
2
87
4
2875
P
t 1
Pt 2
P
t 3
Cl 0
0
Cl 0
1
C10
2 C
103
ClO
4
C10
5 C
lO6
C
lO7
C
l 08
C
10
9
Cll
O
C11
1 C
11
2
C11
3
CA
I 02
C
AI 0
4
CA
I 05
C
AI 0
6
CA
I 07
CB
l 01
CC
l 01
C
C10
2
CN
lOl
CN
102
CN
lO4
C
N1
05
C
N10
7 C
NlO
8
CS
l 01
CZ
l 01
CZ
102
CZ
103
CZ
104
CZ
105
CZ
106
CZ
107
CZ
108
Cop
pers
E
lect
roly
tical
ly r
efin
ed h
ighe
r pu
rity
cop
per
Ele
ctro
lytic
, to
ug
h p
itch
hig
h c
ondu
ctiv
ity c
oppe
r F
ire re
fined
, to
ug
h p
itch
hig
h c
ondu
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ity c
oppe
r O
xyge
n fre
e, h
igh
co
nd
uct
ivit
y co
pper
T
ou
gh
pit
ch n
on-a
rsen
ical
cop
per
To
ug
h p
itch
ars
enic
al c
oppe
r P
hosp
horu
s de
oxid
ized
, no
n-ar
seni
cal c
oppe
r P
hosp
horu
s de
oxid
ized
, ar
seni
cal c
oppe
r .
Cop
per-
cadm
ium
C
oppe
r-te
lluri
um
Oxy
gen-
free
cop
per,
ele
ctro
nic
grad
e C
oppe
r-su
lphu
r C
oppe
r-co
balt-
bery
llium
C
oppe
r-ni
ckel
-pho
spho
rus
Alu
min
ium
bro
nzes
7
% a
lum
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m b
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e (C
U-A
I)
10
% a
lum
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m b
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e (C
u-A
l-F
e-N
i)
10
% a
lum
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m b
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e (C
u-A
l-N
i-F
e-M
n)
7%
alu
min
ium
bro
nze
Cu
-Al-
Fe
) 6
% a
lum
iniu
m-s
ilico
n br
onze
(C
u-A
l-S
i)
Co
pp
er- b
eryl
lium
C
oppe
r-be
rylli
um
Co
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m
Cop
per-
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miu
m
Cop
per-
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miu
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nium
C
op
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kel
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co
me
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l-ir
on
96
/10
cbbp
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l-ir
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6012
0 co
pper
-nic
kel
75
/25
cop
per-
nick
el
7013
0 co
pper
-nic
kel
66/3
0/2/
2 co
pper
-nic
kel-
iron
-man
gane
se
Co
pp
er-s
ilico
n
Cop
per-
silic
on (
silic
on b
ronz
e)
Bra
sses
90
11 0
bra
ss
8511
5 b
rass
80
120
bras
s Le
aded
801
20 b
rass
70
130
arse
nica
l bra
ss
7013
0 br
ass
211
bras
s C
omm
on b
rass
CU
-ET
P
CU
-FR
HC
C
u-O
F
CU
-FR
TP
C
uAs
CU
-DH
P
CuA
sP
Cu
Cd
l C
uTe
CuO
FE
c
us
C
uCo2
8e
CuN
iP
CuA
17
CuA
I1 O
Ni5
Fe4
C
uAIlO
Fe3
C
uA18
Fe3
C
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Si2
Cu
Be
l.7
Cu
Crl
C
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rl Z
r
CuN
i5F
e C
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il O
Fel
Mn
C
uN
i20
C
uNi2
5 C
uN
i30
Mn
l Fe
CuN
i30F
e2M
n2
Cu
Si3
Mn
l
Cu
Zn
lO
Cu
Zn
l5
CuZ
n2O
C
uZn2
0Pb
CuZ
n30A
s
99.9
0% m
ln. C
u *
99.9
0% m
in. C
u *
99.9
5% m
in. C
u *
99.8
5% m
in. C
u t
99.2
0% m
in. C
u, 0
.4%
As
99.8
5% m
in.
Cu,
0.0
4% P
99
.20%
min
. C
u, 0
.4%
As.
0.0
4% P
C
u-0
.8%
Cd
Cu
-0.5
% T
e 99
.99%
min
. C
u (X
) C
u-0
.4%
S
Cu
-2.4
% C
o. 0
.5%
Be
Cu
-1 .O
% N
i. 0.
2% P
Cu
-7%
Al
(x)
Cu
-10
% A
l. 5%
Fe,
5%
Ni
* C
u-9
.5%
Al,
5% N
i, 2
% F
e, 1
% M
n
(x)
Cu
-7%
Al,
2%
Fe
(x)
Cu
-6%
Al,
2%
Si,
0.6%
Fe
(x)
Cu
-1 O/O
Cr
Cu
-l %
Cr,
0.1
Oh
Zr
Cu
-5%
Ni.
1.1
Oh
Fe,
0.5
% M
n
Cr-
10
% N
i. 1
.5%
Fe,
0.7
% M
n
Cu
-20
% N
i, 0.
3% M
n
Cu
-25
% N
i, 0.
3% M
n
Cu
-30
% N
i, 1 %
Mn,
0.7
% F
e C
u-3
0%
Ni,
2%
Fe,
2%
Mn
Cu
-3%
Si,
1 %
Mn
90
% C
u, r
emai
nder
Zn
85
% C
u, r
emai
nder
Zn
80
% C
u, r
emai
nder
Zn
8
0%
Cu,
0.5
% P
b, r
emai
nder
Zn
7
1 %
Cu.
0.0
4% A
s. r
emai
nder
Zn
CuZ
n30
70
% C
u, r
emai
nder
Zn
CuZ
n35
66
% C
u, r
emai
nder
Zn
CuZ
n37
63
% C
u, r
emai
nder
Zn
Cl 0
0
* C
lOl
* C
102
* C
103
[*]
C10
4 [*I
C
105
* C
106
* C
107
[*I
C10
8 C
109
Cll
O
C11
1 C
112
C11
3
* C
AI0
2
(x)
CA
I04
t
CA
I05
*
CA
I06
C
AI 0
7
CB
lOl
CC
lOl
CC
102
CN
lOl
* C
N10
2 C
N10
4 C
N10
5 *
CN
107
CN
10
8
[*I
CS
lOl
cz1
01
C
Z10
2 C
Z10
3 C
Z10
4 *
CZ
105
* C
Z10
6 C
Z10
7 cz
10
8
Lead
free
601
40 b
rass
A
lum
iniu
m b
rass
A
dmira
lty b
rass
N
aval
bra
ss
Hig
h t
ensi
le b
rass
Hig
h te
nsile
bra
ss (
rest
ricte
d a
lum
iniu
m)
Hig
h te
nsile
bra
ss
Lead
ed b
rass
, 64
% c
oppe
r, 1
% le
ad
Lead
ed b
rass
, 62
% c
oppe
r. 2
% le
ad
Lead
ed b
rass
, 59
% c
op
pd
, 2%
lead
Le
aded
bra
ss, 5
8X
cop
per.
3%
lead
Le
aded
bra
ss,
58
% c
oppe
r, 4
% l
ead
Lead
ed b
rass
, 5
8%
cop
per,
2%
lead
Le
aded
bra
ss, 6
0%
cop
per,
0.5
% le
ad
Lead
ed b
rass
, 62
% c
oppe
r, 3
% l
ead
Cap
co
pp
er
Soe
cial
701
30 a
rsen
ical
bra
ss
Alu
min
ium
-nic
kel-
silic
on
-bra
ss
'Lea
ded
bras
s, 6
0%
cop
per.
2%
lead
Le
aded
bra
ss, 6
0%
cop
per.
1 X le
ad
Lead
ed b
rass
for
sect
ions
Le
aded
bra
ss, 6
2%
cop
per.
2%
lead
D
ezi
nci
fica
tion
resi
stan
t bra
ss
Nav
al b
rass
(u
nin
hib
ited
) N
aval
bra
ss (
hig
h le
aded
) H
igh
tens
ile b
rass
wit
h s
ilico
n
Man
gane
se b
rass
Le
aded
bra
ss, 6
0%
cop
per,
0.5
% le
ad
Nic
kel s
ilver
Le
aded
. 10
% n
icke
l bra
ss
10
% n
icke
l silv
er
12
% n
icke
l silv
er
15
% n
icke
l silv
er
18
% n
icke
l silv
er
18
% n
icke
l silv
er (
low
cop
per)
2
0%
nic
kel s
ilver
2
5%
nic
kel s
ilver
Le
aded
10
% n
icke
l silv
er
Pho
spho
r br
onze
4
% p
hosp
hor
bron
ze
5% p
hosp
hor
bron
ze
7%
pho
spho
r br
onze
8
% ~
ho
so
ho
r bro
nze
CuZ
n4O
C
uZn2
0A12
C
uZ
n2
8S
nl
Cu
Zn
38
Sn
l C
uZ
n3
9A
IFe
Mn
CuZ
n39A
IFeM
n
CuZ
n28A
15F
eMn
Cu
Zn
35
Pb
l C
uZn3
7Pb2
C
uZn3
8Pb2
C
uZn3
9Pb3
C
uZn3
8Pb4
C
uZn4
0Pb2
C
uZn4
0Pb
CuZ
n36P
b3
CuZ
n5
CuZ
n3O
As
Cu
Zn
l4A
INiS
i C
uZn3
8Pb2
C
uZ
n3
9P
bl
CuZ
n43P
b2
CuZ
n37P
b2
CuZ
n36P
b2A
s C
uZn3
9Sn
CuZ
n37P
b2S
n C
uZn3
7Mn3
A12
Si
Cu
Zn
40
Pb
ZM
n
CuZ
n40P
b
Cu
Nil
OZ
n42P
b2
Cu
Nil
OZ
n27
Cu
Ni1
2Z
n2
4
Cu
Nil5
Zn
21
C
uN
il B
Zn2
0 C
uN
il8Z
n2
7
Cu
Ni2
0Z
nl7
C
uN
i25
Zn
18
C
uN
il O
Zn2
8Pbl
CuS
n4
CuS
n5
CuS
n7
60
% C
u, r
emai
nder
Zn
77
% C
u, 2
% A
l, 0
.04
% A
s, r
emai
nder
Zn
71
% C
u, 1
.2%
Sn,
0.0
4% A
s, r
emai
nder
Zn
6
2%
Cu,
1.2
% S
n, r
emai
nder
Zn
5
8%
Cu,
1 %
Pb,
1 %
Mn
, 1
% A
l, 0
.7%
Fe,
0
.5%
Sn,
rem
aind
er Z
n 5
8%
Cu,
1%
Pb,
1%
Mn
, 0.7
% F
e, 0
.5%
Sn,
re
mai
nder
Zn
65
% C
u, 4
.5%
Al,
1 %
Mn
, 1
% F
e, r
emai
nder
Zn
6
4%
Cu.
1 %
Pb,
rem
aind
er Z
n
62
% C
u, 2
% P
b, r
emai
nder
Zn
5
9%
Cu.
2%
Pb,
rem
aind
er Z
n
58
% C
u, 3
% P
b, r
emai
nder
Zn
5
8%
Cu.
4%
Pb.
rem
aind
er Z
n
58
% C
U;
2%
~b
;
rem
aind
er Z
n
60
% C
u. 0
.5%
Pb,
rem
aind
er Z
n 6
2%
Cu,
3%
Pb,
rem
aind
er Z
n 9
6%
Cu,
rem
aind
er Z
n 7
0%
Cu,
0.0
4%
As,
rem
aind
er Z
n 8
3%
Cu,
1 Oh
Al,
1 %
Ni,
1 %
Si,
rem
aind
er Z
n 6
0%
Cu.
2%
Pb,
rem
aind
er Z
n 6
0%
Cu.
1 %
Pb,
rem
aind
er Z
n 5
6%
Cu.
3%
Pb,
0.3
% A
l. re
mai
nder
Zn
62
% C
u. 2
% P
b, r
emai
nder
Zn
62
% C
u. 2O
' P
b, 0
.1 %
As,
rem
aind
er Z
n
60
% C
u. 0
.7%
Sn,
rem
aind
er Z
n
60
% C
u. 2
% P
b. 0
.7"/.
S
n, r
emai
nder
Zn
5
8%
Cu,
2%
Mn
. 1
.5%
Al,
1 %
Si,
rem
a~nd
er Zn
5
7%
Cu.
2%
Pb,
1 %
Mn
, re
mam
der
Zn
60
% C
u. 0
.5%
Pb,
rem
aind
er Z
n
45%
Cu,
10
% N
i, 2%
Pb,
0.3
% M
n,
rem
aind
er Z
n 6
3%
Cu,
10
% N
i, 0.
2% M
n,
rem
aind
er Z
n 6
3%
Cu,
12
% N
i, 0.
2% M
n, r
emai
nder
Zn
63
% C
u, 1
5%
Ni,
0.2%
Mn,
rem
aind
er Z
n 6
3%
Cu,
18
% N
i. 0.
2% M
n, r
emai
nder
Zn
5
5%
Cu,
18
% N
i, 0.
2% M
n, r
emai
nder
Zn
6
3%
Cu,
20
% N
i, 0.
3% M
n, r
emai
nder
Zn
57%
Cu,
25%
Ni.
0.5%
Mn
, re
mai
nder
Zn
60
% C
u, 1
0%
Ni.
1.5
% P
b, 0
.3%
Mn,
rem
aind
er Z
n
Cu
-4%
Sn.
0.2
% P
C
u-5?
4" s
n.
0.2
% P
C
u-7
% S
n. 0
.2%
P
CuS
n8
Cu
-8%
Sn,
0.2
% P
(x)
CZ
109
* C
Z11
0 C
Zl 1
1
* cz
11
2
CZ
114
NS
lOl
n5103
n5104
n5
10
5
n5
10
6
n5
10
7
n5
10
8
n5
10
9
NS
lll
. .
t D
esig
natio
ns a
ccor
ding
to
the
prin
cipl
es o
f IS
0 1
1 9
0 P
art
1
incl
ud
ed
in s
tand
ard
(r) p
ropo
sed
for
incl
usi
on
in s
tand
ard
[*]
prop
osed
for
de
letio
n fr
om s
tand
ard
(x)
no
t in
clu
de
d in
sta
ndar
d b
ut m
ay b
e av
aila
ble
in th
is p
rod
uct
form
Tab
le 4
co
nti
nu
ed
b
Cas
t mat
eria
ls'"
Des
crip
tion
Des
igna
tion
Ca
teg
~ry
'~'
App
roxi
mat
e co
mp
osi
tion
X
Oth
ers
spec
ified
A
pp
rox.
B
S 1
40
0
BS
45
77
IS
O'2
) T
in
Zin
c Le
ad
Pho
spho
rus
Nic
kel
Alu
min
ium
Ir
on
M
anga
nese
(o
the
rth
an
co
nd
uct
ivity
im
purit
ies)
74 I
AC
S
Cop
pers
H
igh
co
nd
uct
ivity
cop
per
Co
p~
er-
chro
miu
m
cop
pe
r-n
icke
l-p
ho
sph
oru
s C
op
pe
r-n
icke
l-si
lico
n
Co
pp
er-
cob
alt-
be
rylli
um
C
op
pe
r-b
ery
lliu
m
Bra
sses
B
rass
for
sand
cas
tings
Bra
ss fo
r sa
nd c
astin
gs
Nav
al b
rass
for
sand
cas
ting
Bra
ss fo
r br
azab
le c
astin
gs
Bra
ss fo
r d
ie c
astin
gs
Bra
ss fo
r d
ie c
astin
gs
De
zin
cific
atio
n re
sist
ant b
rass
fo
r di
ecas
tings
B
rass
for
pres
sure
die
cas
tings
H
igh
tens
ile b
rass
Hig
h te
nsile
bet
a br
ass
Bro
nzes
Le
aded
bro
nze
Lead
ed b
ronz
e
Lead
ed b
ronz
e Le
aded
bro
nze
Pho
spho
r-br
onze
P
hosp
hor-
bron
ze
Pho
spho
r-br
onze
Le
aded
ph
osp
ho
r-b
ron
ze
Co
pp
er-
tin
Co
pp
er-
tin
Gun
met
als
Lead
ed g
unm
etal
Le
aded
gun
met
al
8717
1313
lead
ed g
unm
etal
G
unm
etal
Nic
kel g
unm
etal
C
op
pe
r-a
lum
iniu
m a
lloys
A
lum
iniu
m b
ronz
e A
lum
iniu
m b
ronz
e A
lum
iniu
m s
ilico
n b
ronz
e C
oppe
r-m
anga
nese
-alu
min
ium
Co
pp
er-
nic
kel a
lloys
C
op
pe
r-n
icke
l-ch
rom
ium
C
op
pe
r-n
icke
l-n
iob
ium
HC
C1
All
1
CC
1-T
F
A21
1 A
411
A31
2 A
311
A41
2
SC
Bl
SC
B2"
' S
CB
3 S
CB
4 S
CB
~I"
~
SC
B6
DC
Bl
DC
B2'
" D
CB
3
151
PC
B1
HT
Bl
HT
BI*
' H
TB
3
LB1
LB
2
LB3(
'' L
B4
L
B5
P
B1
PB
2 P
B3'
"' P
B4
LP
Bl
CT
l C
T2
LG1
LG2
LG3'
'' LG
4 G
I ~
21
'' G
3
AB
1
AB
2
AB
3
CM
Al
CM
A2"
'
CN
1 C
N2
G-C
uZ
n3
3P
b2
G
-Cu
Zn
36
Sn
G
-Cu
Zn
l OS
n G
-Cu
Zn
l 5A
s G
-Cu
Zn
40
G
-Cu
Zn
37
Sn
G
-Cu
Zn
40
Pb
G
-CuZ
n34P
b2A
IAs
G-C
uS
nlO
P
G-C
uS
nll
P
G-C
uS
n9
P
G-C
uS
nl O
PbP
G
-Cu
Sn
7P
bP
G
-Cu
Sn
lO
G-C
uS
nl 2
Ni
Crl
Si 0
.5
Co
2.5,
Be
0.5
B
e 2
"' F
or a
ctua
l com
posi
tions
, m
echa
nica
l an
d p
hysi
cal p
rope
rtie
s o
f ca
stin
gs a
nd c
om
po
sitio
n o
f in
go
ts s
ee B
S 1
40
0 : 1
985,
Bri
tish
Sta
ndar
ds In
stitu
tion
"'
Del
eted
fro
m B
S 1
40
0
For
su
itab
ility
of
thes
e al
loys
for
cast
ing
tech
niqu
es s
ee B
S 1
40
0 :
19
85
App
endi
x G
, T
able
15
. BS
45
77
giv
es o
nly
no
min
al c
om
po
sitio
ns
Is' P
ropo
sed
for
incl
usi
on
in B
S 1
40
0
''' IS
0 d
esig
natio
n de
rived
fro
m I
S0
11
90
/1.
Ma
ny
of
thes
e al
loys
are
equ
ival
ent
to th
ose
spec
ified
in
IS
0 1
338.
see
BS
14
00
: 1
98
5 A
ppen
dix
H
13'
BS
14
00
Cla
ssifi
catio
ns:
Cat
egor
y A
- al
loys
in
co
mm
on
use
C
ateg
ory
B - all
oys
in u
se fo
r sp
ecia
l pur
pose
s C
ateg
ory
C - al
loys
in
lim
ited
pro
du
ctio
n
Table 5: Physical properties of copper
Atomic numberAtomic weightLattice structure: face centred cubicDensity: standard value
at 1083°C (solid)at1083°C (liquid)
Melting pointBoiling pointLinear coefficient of thermal expansion at:
-253°C-183°C-191°C to 16°C25°C to 100°C20°C to 200°C20°C to 300°C
Specific heat (thermal capacity) at:-253°C-150°C-50°C20°C100°C200°C
Thermal conductivity at:-253X-200°C-183X-100°C20°C100°C200°C300°C
Electrical conductivity (volume) at:20°C (annealed)20°C (annealed)20°C (fully cold worked)20"C (fully cold worked)
Electrical resistivity (volume) at:20°C (annealed)20°C (annealed)20°C (fully cold worked)20°C (fully cold worked)
Temperature coefficient of electricalresistance at 20°C:
annealed copper of 100% IACS(applicable from -100°C to 200°C)
fully cold worked copper of 97% IACS(applicable from 0°C to 100cC)
Modulus of elasticity (tension) at 20°C:annealedcold worked
Modulus of rigidity (torsion) at 20°C:annealedcold worked
Latent heat of fusionElectro chemical equivalent for:
Cu + +
Cu +
Normal electrode potential (hydrogen electrode) for:Cu + +
Cu +
Value
2963.54
8.898.327.9910832595
0.3 * 1 0 - 6
9.5 x 1 0 " 6
14.1 x 1 0 - 6
16.8 x i O " 6
17.3 x i O " 6
17.7 x i o - 6
0.0130.2820.3610.3860.3930.403
12.985.744.734.353.943.853.813.77
58.0-58.9100.0-101.5
56.397.0
0.017241-0.01701.7241-1.700.01781.78
0.00393
0.00381
118000118000-132000
4400044000-49000205
0.3290.659
-0.344-0.470
Units
g/cm3
g/cm3
g/cm3
°C°C
/•cfC/°c/°c/°c/°c
J/g°CJ/g°CJ/g°CJ/g°cJ/g°CJ/g °C
Wcm/cm2 °CWcm/cm2 °CWcm/cm2 °CWcm/cm2 °CWcm/cm2 °CWcm/cm2 °CWcm/cm2 °CWcm/cm2 °C
MS/m (m/ohm mm3)% IACSMS/m (m/ohm mm3)% IACS
ohm mm2/mfjCl cmohm mm2/m/jCi cm
per °C
per °C
N/mm2
N/mm2
N/mm2
N/mm2
J/g
mg/Cmg/C
VV
Note: The values shown are typical for electrolytic tough pitch high conductivity copper (C101).Values for other grades of copper may differ from those quoted.
of information comparing national and international com-positional specifications and detailing the typical physicaland mechanical properties of the wrought materialsincluding tensile, ductility and hardness properties at low,ambient and elevated temperatures, together with creep,fatigue and impact data.
Sponsored by a contract placed by the InternationalCopper Research Association (INCRA), the BNF MetalsTechnology Centre has recently completed a critical surveyof available high temperature mechanical property data forcopper and copper alloys [66]. This is available as anINCRA Monograph.
Murphy [67] has recently published a review, supple-mented by original data, of the engineering fatigue proper-ties of high conductivity tough pitch copper.
On-line access to much of this type of information canbe gained through the Metals Information Datafile ofAlloys and Specifications (MIDAS) established jointly bythe Metals Society in the UK and the American Societyfor Metals. Searches may be carried out either by directreference to an individual alloy or by the use of other vari-ables such as alloy class, specification equivalents, countryof origin, or for particular property values or productforms.
1EE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986 189
Table 6: Electrical properties of wrought and annealed coppers
Designation BS 6017 Equivalent Values (for guidance only)Mandatory Value
wrought original cast mass resistivity, volume resistivity, Conductivityrefinery shape ohm g/m2 ohm mm2/m MS/m % IACS
max. max. min. min.
C110
C101C102C103
C101C102
Cu-Cath-1Cu-ETP-1Cu-OFE
Cu-Cath-2Cu-ETP-2*Cu-FRHC*Cu-OFCu-Ag (all)Cu-Ag-OF (all)
Cu-ETP-2**Cu-FRHC**
0.15176
0.15328
0.15593
0.01707
0.01724
0.017538
58.38 101.0
58.00 100.0
57.00 98.3
* when copper is for electrical purposes•* when copper is for nonelectrical purposes (not quoted in specifications for material forgeneral engineering purposes)
Table 7: Typical mechanical properties of wrought coppers and high conductivity copper alloys
Typicalmechanicalproperties
Designations: ISO and BS
wrought coppers and copper alloys heat treatable alloys
Condition Cu-ETPCu-FRHCCu-FRTPCuAgC101, C102,C104
Cu-DHPCu-OFCu-OFE
C106C103, C110
CuSCuTe
CuCd Condition CuBe2 CuCo2Be CuCri CuNi2Si CuNiPCuCMZr
C111,C109 C108CC101
CB101 A3/1 CC102 A3/2 A4/1
Tensile strength,N/mm2
0.1 % Proofstress, N/mm2
Elongation, %
Hardness, HV
Softeningtemperature, °C
a
ha
ha
ha
h
220
38560
32555
445
115150f
220
38560
32560
445
115
230
31060
26540
850
100
280
70060
46045
460
140250
" bcdbcdbcdbcdc
50011601400
185930
108050
52
100370400300
310740850
650770
32151080
220240500
230400510
45265430
50222065
125160500|t
310635740
80480650
50151060
170210500
230450495
60340420
45252060
140175475
Condition: a = annealed; h = hard; b = solution heat treated; c = solution heat treated and aged; d = solution heat treated, cold worked and agedSoftening temperature = the lowest temperature that, if maintained for 2 hours, will give a reduction in hardness of 20% of the differencebetween the hardest as received condition and the softest possible condition of that material,f for Cu-ETPft f CuCrZr 525°C
7 Oxidation and corrosion
Copper forms two oxides, both of which are conductors.Cuprous oxide (Cu2O) is red in colour and the first toform on the surface of polished copper exposed to theatmosphere. At room temperature this will slowly darkento a thicker black layer containing cupric oxide (CuO).The darkening will be faster in the presence of sulphurcompounds due to the formation of black copper sulphide.Once formed the black oxide film is tightly adherent;further growth is very slow provided that the temperaturedoes not exceed 200°C and that other deleterious chemi-cals are not present.
Although cuprous oxide was at one time in use on theplates of low-voltage rectifiers, its low breakdown potentialof 20 peak volts means that this is unlikely to be a seriousconsideration of bolted conductor joints. This is especiallytrue if the joints have been made, as frequently recom-mended, between faces of clean copper lightly protectedwith a film of petroleum jelly.
In outdoor conditions the exposed surfaces of copperare subject to rainwater containing dissolved carbondioxide and oxides of sulphur which form a weak acid sol-ution and help to form the well known attractive green'patina' which is also adherent and protective [68].
At elevated temperatures such as those used for anneal-ing coppers, the oxide formed is mainly cupric oxide.Excess oxide tends to exfoliate and this removal may beassisted, if required, after an anneal by a water quench.
None of the alloying additions described has a dele-terious effect on the good oxidation resistance of copper.In general, the effect is an improvement and this facilitatesthe use of some of these materials at temperatures higherthan 200°C where creep resistance is also required [69].
Many of the applications of coppers rely on known cor-rosion resistance together with their other properties.Besides the good resistance to the atmosphere (includingmarine environments), coppers have a good resistance toorganic acids and also to alkalis (with the exception of
190 IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
ammonia). Coppers can be buried underground in mostsoils without the risk of corrosion, although there can beproblems in certain acid soils and clays. The wide use ofcopper for heat exchanger purposes is indicative of itsgood resistance to corrosion by potable waters, both hotand cold, and to domestic wastes and sewage. In certain ofthese applications the strong resistance of coppers to bio-fouling is also a great advantage.
As with all except the noble metals, the corrosionbehaviour of copper is a function of the oxides and willvary depending on the exposure conditions such as turbu-lence and velocity of the media, the presence of traces ofcontaminants and, of course, any bimetallic effects intro-duced in mixed metal systems in corrosive environments.
8 Fabrication
As can be seen from Table 8, coppers and most of the highconductivity copper alloys can be worked both hot andcold very readily.
8.1 Hot workingThe ranges of hot working temperatures quoted formaterials are those which are used commonly, the part ofthe range selected depending on the size of the material,the type of operation and the extent of working required.It will generally be possible to continue working belowthese temperatures, but the resultant product, having beenworked 'warm' rather than 'hot', will retain a distortedinternal structure giving higher strength and hardness.
A controlled atmosphere can be used in preheating fur-naces to reduce oxidation, but care must be taken whenheating coppers containing oxygen so that they are notembrittled by hydrogen or other reducing gases. Followinghot working, a water quench may be used with mostmaterials to help remove excess oxide scale.
8.2 Cold workingAll the materials show some degree of cold ductility. Nat-urally, the extent of any deformation achieved will dependupon the material, the form in which it is supplied and thetype of cold working process used. The elongation valuesquoted in Table 7 give a guide to ductility in tension asrequired for drawing operations. For cold rolling orsimilar processes involving compression, greater strain canbe achieved. Fig. 11 shows the rate of change of strength,
* 50 -
0 10 20 30 40 50 60reduction of thickness by rolling. 7.
Fig. 11 Effect of cold rolling on mechanical properties and hardness ofhigh conductivity copper strip
LEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
hardness and elongation of electrolytic high conductivitycopper strip with the extent of cold work. Note that therelationship between tensile strength and hardness is notlinear.
If the extent of cold work required is severe, interstageannealing may be required. Generally this should becarried out for the shortest time at the minimum tem-perature needed to achieve the required softening to avoidexcessive grain growth which can lead to surface rough-ness 'orange peel' effects or even embrittlement.
For the best deep drawing properties of the materialsshown, phosphorus deoxidised copper is normally recom-mended. If this or any other material is required in sheetform for this purpose, it should be ordered to 'deepdrawing quality'. During the manufacture of this type ofmaterial the composition, working and annealing is closelycontrolled to give the required highly ductile, non-directional properties. The problem of uneven drawingcausing 'ears' at the edges of pressings is therefore reduced.
8.3 Effect of temperature on coppersAlthough the high conductivity coppers are extremelyductile and can be cold worked considerably, an annealmay be required to resoften the metal. The temperature tobe used depends on the composition of the copper, theextent to which it has been cold worked and the time spentwithin the annealing temperature range. The metal sectionsize and the type of furnace used also affect time and tem-perature relationships.
In Fig. 12 the effect that various amounts of prior cold
100 200 300 400annealing temperature, °C
500
Fig. 12 Typical effect of the extent of previous cold work on the anneal-ing behaviour of tough pitch copper Cu-ETPThe annealing time in each case is I hour
work have on the annealability of electrolytic high conduc-tivity tough pitch copper is shown. It will be noted that themore cold work present the more readily is the copperannealed. Similar effects will be found with the othermaterials. For any given material, the lower the tem-perature the longer it will take to soften, as is shown inFig. 13.
The results of annealability tests on four differentmaterials are shown in Fig. 14 which emphasises the effectof alloying on elevated temperature behaviour. The inter-relationship of temperature with time is shown in Fig. 15for both electrolytic tough pitch copper and for a similarcopper with 0.08% silver added. The very beneficial effectof sliver on creep strength is evident.
The results of the work by Benson, McKeown andMends [70] on the creep and softening propertiesof copper for alternator windings, showed that coppermay be satisfactorily used at operating temperatures well
191
above ambient. Depending on operating stresses, tem-peratures up to 150°C can be used with electrolytic copperand up to 200cC with silver bearing high conductivitycopper. Because of its high melting point and high specific
100
90
> 8 0r
c
§60c
50
v \375\35c\ V \
'400VV°c \ \
1 1 1 1 1
PC \325°C
\
\300°C
\
\275°C
\
0.1 Q5 1 5 10 1 2 A 8 24 48minutes hours
annealing time
Fig. 13 Typical effect of annealing temperature on the annealing behav-iour of tough pitch copper Cu-ETP
100 200 300 400 500 600 700annealing temperature, °C
Fig. 14 Change of hardness of various metals after 30 minutes at tem-perature
2.6
S2.0-Oo
IQ.a 1.8
1.6
tough-pitch
0-1 102 103 10* 105 10s
time, h
Fig. 15 Relationship between time and reciprocal absolute annealingtemperature to produce 50% softening of cold-worked Cu-ETP and CuAg0.08
heat compared with aluminium, copper is better able tostand short circuit overload conditions producing shorttime overheating.
In Table 8, temperature ranges are shown for each com-position for both stress relieving and full annealing. Theformer treatment may be employed if components arelikely to be used in an aggressive environment to reducesusceptibility to stress corrosion or corrosion fatique. Thispractice is, however, not frequent. The wide range of tem-peratures quoted for annealing is caused by the factorsmentioned previously, all of which must be taken intoaccount when specifying an annealing treatment. Gener-ally, it is good practice to use moderate temperatures andtimes to restrict oxidation and also the grain growthcaused by over-annealing. Normally it is not practicable to'temper anneal' high conductivity copper reproducibly to ahardness intermediate between hard and annealed. Suchintermediate tempers are produced by cold work from thesoft condition. This does not apply though to the heattreatable alloys where prolonged heating at or above theprecipitation hardening temperature will result in pro-gressive 'overaging' and a gradual loss of hardness and,incidentally, conductivity.
The principles upon which the solution and precipi-tation treatments for the heat treatable alloys depend havebeen briefly described previously. The recommendations ofthe manufacturers of these alloys regarding times and tem-peratures suitable to particular products should be soughtand followed to obtain optimum properties.
For most annealing operations, closely controlledatmospheres are not essential because any oxide film pro-duced may usually be removed during a water quench orsubsequent pickle in dilute sulphuric acid.
'Bright' annealing in a controlled atmosphere is possiblebut, as mentioned elsewhere, care should be taken whenannealing any tough pitch copper that there is not avail-able sufficient hydrogen to reduce the oxides in the copperto steam and thus embrittle it by 'gassing'. A study of thefactors affecting the possible embrittlement of tough pitchcopper during annealing has been published by Harper,Calicut, Townsend and Eborall [46] showing the atmo-spheres and temperatures which may be safely used. Thesame authors also studied the possibilities of embrit-tlement occurring during slightly elevated temperatureusage under conditions of hydrogen cooling such as inheavy electrical generators [47]. It was concluded thatalthough there might be slight pickup of hydrogen by thecopper, no embrittlement would occur unless there wassubsequent substantial heating, as in the event of repair bybrazing or welding.
8.4 MachiningAs Table 8 shows, the easiest of the coppers to machineare the special free machining grades which approach theease of machining of the standard brass. The machiningproperties of all the materials vary and it is suggested thatfor best results the tool angles, cutting speeds and lubri-cants should be selected from those recommended byWoollaston [54]. Very recent work by Wise, sponsored bythe International Copper Research Association, has shownthat by improving the design of cutting tools with respectto their chipbreaking ability the machinability of electro-lytic tough pitch copper can be as good as the free machin-ing grades machined conventionally [18].
8.5 Joining8.5.1 Soldering: Copper is one of the easiest metals tosolder and for this reason, combined with its conductivity,
192 IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
Ta
ble
8:
Fa
bri
ca
tio
n p
rop
ert
ies
of
co
pp
ers
an
d h
igh
co
nd
uc
tiv
ity
co
pp
er
all
oys
CU
-ET
P
CU
-DH
P
CU
-OF
C
uS
Cu
Ag
C
uCd
CuB
e2
CuC
o2B
e C
uC
rl
CuN
i2S
i C
uNiP
C
U-F
RH
C
CU
-OF
E
CuT
e C
uC
rlZ
r C
U-F
RT
P
Cas
ting
tem
pera
ture
H
eat t
reat
men
t te
mpe
ratu
res
stre
ss r
elie
ving
an
neal
ing
solu
tio
n tr
eatm
ent
prec
ipita
tion
trea
tmen
t H
ot f
orm
abili
ty
Ho
t wo
rkin
g te
mpe
ratu
res
Col
d fo
rmab
ility
an
neal
ed
max
. co
ld re
duct
ion
betw
een
anne
als
solu
tio
n tr
eate
d pr
ecip
itatio
n ha
rden
ed
max
. co
ld re
duct
ion
Ma
chin
ab
ility
(fre
e m
/c b
rass
= 1
00)
as m
anuf
actu
red
solu
tio
n tr
eate
d pr
ecip
itatio
n ha
rden
ed
Join
ing
met
hods
so
lder
ing
braz
ing
oxya
cety
lene
we
ldin
g
carb
on-a
rc w
eld
ing
ga
s sh
ield
ed a
rc w
eld
ing
co
ated
met
al a
rc w
eld
ing
re
sist
ance
we
ldin
g:
spot
an
d s
eam
b
utt
1 1 20
-1 2
00
150-
225
200-
650
go
od
75
0-95
0
exce
llent
95
20
exce
llent
g
oo
d
X fair
fair
X
X
X
1 140
-1 2
00
200-
250
250-
650
go
od
75
0-90
0
exce
llent
95
20
exce
llent
ex
celle
nt
go
od
g
oo
d
exce
llent
X
fair
1 12
0-1
200
150-
200
200-
600
go
od
75
0-90
0
exce
llent
95
20
exce
llent
ex
celle
nt
fair
fair
go
od
X
X
X
225-
275
400-
650
go
od
75
0-85
0
go
od
70
80
exce
llent
g
oo
d
X
X
X
X
X
X
225-
275
350-
650
go
od
75
0-95
0
exce
llent
90
20
exce
llent
g
oo
d
X fair
fair
X
X
X
250-
350
500-
700
go
od
75
0-87
0
exce
llent
9
0
25
exce
llent
g
oo
d
fair
X fair
X fair
fair
600-
750
740-
800
300-
360
go
od
62
5-80
0
40
go
od
lim
ited
10
30
20
go
od
g
oo
d
X X go
od
fa
ir g
oo
d
fair
750-
825
900-
960
450-
490
go
od
70
0-90
0
50
g
oo
d
fair
30
30
30
go
od
g
oo
d
X
X fair
fair
go
od
fa
ir
700-
850
650-
725
950-
1 00
0 75
0-85
0 42
5-50
0 42
5-49
0 g
oo
d
exce
llent
75
0-90
0 80
0-90
0
75
75
go
od
g
oo
d
fair
fair
35
20
go
od
g
oo
d
fair
go
od
x
go
od
X
X
fa
ir g
oo
d
x fa
ir fa
ir g
oo
d
fair
ao
od
1 130
-1 2
00
750-
825
900-
980
400-
500
go
od
70
0-90
0
75
go
od
g
oo
d
60
30
30
go
od
g
oo
d
go
od
g
oo
d
go
od
X g
oo
d
qo
od
g
oo
d
The
info
rma
tio
n g
ive
n in
this
tab
le is
for
gene
ral g
uida
nce
on
ly s
ince
ma
ny
fact
ors
influ
ence
fabr
icat
ion
tech
niqu
es
For
clos
er in
form
atio
n re
gard
ing
spec
ific
appl
icat
ions
con
sult
the
man
ufac
ture
rs o
r th
e C
DA
it finds many applications where good joint integrity isessential. This applies not only in the electrical industriesbut also in plumbing and heat exchangers where jointsmust be easy to make and permanent.
Fluxes are used to prevent oxidation during soldering.Their compositions vary according to the expected clean-liness of the joint and the type of application. 'Protective'fluxes will maintain copper in an oxide-free condition forsoldering under gentle heating conditions. For dealingwith conditions where the copper may be slightly tarnishedinitially and when using direct blow torch heating, an'active' flux is required [71]. The residues from this fluxshould be removed as recommended by the manufacturerto eliminate any danger of subsequent corrosion. Many ofthese fluxes are now easily washed off in water.
8.5.2 Brazing: Carried out at a higher temperature thansoldering, brazing similarly entails 'wetting' the materialsto be joined with a filler metal, albeit with a much greaterstrength. The techniques involve the use of a fluid metalwith good capillary penetration between close joint clear-ances. Alternatively, a fillet jointing operation 'bronzewelding' can be carried out generally on heavier sectionsthan for the former methods.
'Silver solders' are a family of alloys based on copper-silver alloys. They require the use of a suitable flux and thesilver content makes them initially expensive, but thelimited quantity of filler used and the good integrity of fillof well designed joints frequently keeps this material eco-nomic.
A self fluxing action is found in the copper-phosphorusalloys which also contain some silver. At brazing tem-peratures the phosphorus reduces any oxides formedduring heating and a good joint can therefore be made[25].
A full description of the processes, joint design andtechniques recommended is contained in Reference 72.
8.5.3 Welding of copper: Until recent years, the weldingof copper for electrical applications was not widely practi-cal for several reasons. The very high conductivity of purecopper, normally regarded as an advantage, means thatheat is very rapidly conducted away from the area of thejoint and that a very high rate of heat input is required tocounter this effect and give well-fused joints.
While the welding of deoxidised copper by conventionaltechniques presents few other problems, the welding of theoxygen-bearing conventional high conductivity coppermust not be undertaken in conditions where a reducingatmosphere is present or there will be severe danger ofcombination of hydrogen with the dissolved oxygen givinghydrogen embrittlement or 'gassing'. With flux shielding orthe use of flux-coated electrodes, successful joints can bemade, provided reasonable precautions are used duringoxyacetylene welding.
The advent of gas shielded arc welding process hasintroduced welds with an improved appearance, whichmeans no residual corrosive flux residue and better controlof welding procedures. With such improvements TIG orMIG welding is now normal practice. Nitrogen shieldingcan be used for deoxidised copper but not for the highconductivity grade. Argon is used very successfully butbetter still is helium, either pure or mixed with argon.Helium has a much greater ionisation potential thanargon, and gives greater penetration and a much widerpenetration profile. Recommendations for joint design,filler materials, preheating and welding techniques are con-tained in Reference 73. As they contain deoxidants the
194
filler metals do not have such a good conductivity as purecopper, but as their volume is usually very small comparedwith the rest of the conductor, the effect can usually beignored.
For the jointing of fairly small conductors, resistancewelding or flash-butt welding can be used. Frictionwelding and induction welding are not generally successfulwith high conductivity copper being welded to similarmetal, although these methods may be used for joints tosome metals of lower conductivity.
9 Some electrical applications of copperand copper alloys
Some of the vast range of applications for coppers andcopper alloys have already been mentioned. In practicethese range from busbars of massive cross-section to thesmallest of components for micro-electronics applications.
Some products, such as printed circuit boards, representa very different technology and it is not possible to dojustice to such components in this review. A few remarkscan be made regarding typical products fabricated by tra-ditional techniques. With most of these there is a gradualimprovement in manufacturing processes to meet customerrequirements for improved tolerances and product per-formance.
9.1 Copper in cablesThe use of copper in electrical cables has been establishedfor many years. For domestic cables it was at one timetinned in order to prevent a reaction between the copperand the rubber insulation. However, with the universal useof plastics such as PVC for insulation, tinning of copperwire is no longer essential.
For uninsulated overhead power distribution, copper isnow little used because of the cheaper price of aluminium.For domestic cables there was at one time a tendencytowards the use of aluminium, but the larger cross sectionspecified for any given amperage raised the cost of the sur-rounding insulation. Because of the fire safety risks causedby the difficulty in making terminations, aluminium is notnow used for domestic insulated cables.
Recent developments in glass fibre technology haveshown that it has good prospects in the expanding infor-mation technology message transfer market as a linkbetween terminals. However, it is not possible to transfersignificant power through glass fibre message links,whereas it is possible to superimpose messages on power-carrying copper conductors. The future for further uses forthe existing copper power conductors entering premiseslooks interesting with several systems of mains-carriedmessages under consideration.
The manufacture and use of heavy duty insulated powertransmission and distribution cables is a very complexsubject in its own right, involving as it does the technologyof a great variety of insulating materials.
There are strong and growing objections to the prolifer-ation of overhead transmission lines. Over many decadesthere has been much development work to reduce theprime cost of underground electrical power transmissionby evolution of the conventional cables and by the intro-duction of forced cooled systems. Recently, very substan-tial effort and expenditure, particularly in the USA, hasbeen devoted to seeking means to drastically reduce theunderground cable to overhead line prime cost ratio.
These investigations have included:(a) low dielectric loss insulations for conventional oil
pressure cables, with natural and forced cooling
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
(b) cables with extruded and lapped film plastic insula-tions
(c) spacer cable where the tubular inner and outer con-ductors are separated almost totally by compressed elec-tronegative gas, particularly sulphur hexafluoride
(d) cables in which superconducting elements based onniobium are maintained at liquid helium temperatures, i.e.a few degrees above absolute zero
(e) cables with conductors cryogenically cooled to liquidnitrogen temperature
(/) waveguides for transmitting large electrical powersat microwave frequencies, i.e. millimetric and centrimetric
(g) cables with solid glass insulationall for both DC and AC applications.
Associated with the above have been investigations intocable installation techniques, covering, trenching, tunnel-ling and a range of cable trench backfills.
Banks [75] reports that, with some work to be com-pleted, the USA electrical utilities have reached much thesame conclusions as had been reached in the UK over adecade before:
(a) that none of these constructions or techniques cansubstantially reduce the underground cable to overheadline prime cost ratio
(b) that the novel constructions, such as superconduc-ting cables, have no prospect of becoming cost competitivewith conventional cables at transmission powers belowabout 5000 MW per circuit, i.e. about twice the maximumcircuit power installed in the world at this time.
An interesting development in the quality of connectingcables for audio equipment is the use of 'linear crystal' or'monocrystal' copper wire. The former term is used by theJapanese manufacturers and the latter by the Dutch [75].Both materials are believed to be wire of low oxygencontent drawn from feedstock of large grain size and pre-sumably annealed. The resultant reduction in grain bound-aries across the path of the signal results in lessattenuation.
9.2 Copper in electrical contacts, springs andsemiconductor lead frames
Copper and copper alloys are widely used in electrical con-tacts of almost every type. With the very wide range ofcompositions and properties available there is a materialto suit almost every requirement of electrical rating. Mostof the alloys described previously are used for various pur-poses (especially those included in BS 4577, 'Copper alloysfor resistance welding applications'), but there is also arange of special materials designed and used specificallyfor contact operations. These materials may be produced
conventionally or by powder metallurgy sintering tech-niques. Typical materials and their applications have beendescribed by Turner and Turner [76].
In the manufacture of contacts for mass markets suchas the automation or domestic appliance fields, the pro-duction techniques in use are in a constant state ofimprovement in the interests of reliability and economy.The accuracy and abilities of progression tooling makespossible the production of ever more complex componentsfrom copper, copper alloy or bimetallic strip feedstock.The relatively recent processes of contour profiling thestrip before component manufacture and of selectiveprecious metal plating, have also helped to improve theproducts made to a considerable extent. However, thecommercial success of these processes has meant that littlehas been published on the subject.
The special requirements of semiconductor lead frameshave lead to the development of even more materials witha variety of properties to suit individual requirement forconductivity, springiness and heat resistance (Table 9 andFig. 16). Table 10 shows a comparison of American andJapanese alloys [24]. German production favours modifiedcopper-iron alloys Cu Fe2 P (K65) and Cu Fe 2.4 Zr 0.02as described recently by Puckert [77].
For springy contacts the traditional materials arespring-hard brass nickel silver, phosphor bronze and beryl-lium copper, but there are many others from which tochoose. The combination of properties such as conduc-tivity, formability, fatigue resistance and elevated tem-perature performance are critical to a greater or lesserdegree. Design criteria are described in Reference 78.
Highest strengths are obtained with the copper-beryllium alloys, including the 2% beryllium alloy(CB 101) and alloys containing only about 0.5% berylliumand 2% total cobalt plus nickel. Some alternatives to theseare now being offered such as 'Delcan', a heat treatableproprietary alloy containing about 4% nickel and addi-tions of aluminium, silicon and chromium [79]. Manyother alternatives have recently been described [80].
9.3 Electric motors of improved efficiencyManufacturers of electric motors have, for many years,had design aims of improved output/weight and output/volume ratios for minimum first cost. This has inevitablyresulted in a compromise on other attributes such as effi-ciency and power factor. With the increases now occurringin energy costs and the attention now being paid toreducing the energy content of products, a reconsiderationof these design values is appropriate. Considerable efforthas been spent on these considerations at ERA Tech-nology and a very useful report has been produced byKnights [82]. This considers the design alternatives for
Table 9: Properties of some 'traditional' and 'new' high strength copper alloys spring materials [18]
ISO description
CuSn8CuNi18Zn20CuNi9Sn2CuZn23AI3.5CoCuBe2
CuNi15Sn8CuNi20Mn20CuNi18Mn18BeCuNi20AI4.5Mn3CrCuTi2.5CuTi4.5CuNi5Ti2.5CuAI10Ni4CrSi
BSdesignation
PB103NS106
CB101
ASTMUNS. number
C52100C76400C72500C68800C17200
C72900
0.2% Proof Stress,N/mm2
540560620920
1200
1200135013501350
9001150
630850
Elastic limit.N/mm2
440510540800
1050
1000130013001300
7501000
Young's Modulus,k N/mm2
115140132117135
127150150160125127130135
Conductivity,MS/m
83.56.49.6
12
4.51.71.7296
3212
IEE PROCEEDINGS, Vol. 133, Pi. A, No. 4, JUNE 1986 195
Table 10: Properties of electronic mType
Highconductivity
Highstrength
Highconductivity
Highstrength
42 alloy
DesignationCopper No(ASTM-UNS)
KFC(C19210)KLF-2OF(C10200)Cu-Zr(C15000)Cu-SnCu-Ag(C15500Cu-CoKLF-1CDA194(C19400)CDA194(C19400)Cu-Fe-SnKLF-5CAC92(C72500)Cu-Si-Sn(C65400)Cu-Sn(C51900)Fe-Ni(F30)
laterials for semiconductor leadframes
Nominal Composition (%)
Cu
bal.
bal.99.96
bal.
bal.bal.bal.bal.bal.bal.
bal.
bal.bal.bal.
bal.
bal.
Sn
0.1
0.15
0.6
1.22.02.3
1.5
6
Fe
0.1
0.1
2.3
1.5
0.80.1
bal.
Ni Zn P
0.03
0.03
0.010.06
0.073.2 0.3
0.1 0.03
0.1
0.030.03
9
0.03
42
otherelement
Zr.0.18
Ag.0.18Mg.0.1Co.0.22Si.0.7
Co.0.8
Si.3.05Cr.0.07
General
T.S.
kg/mm2
41
4738
48
4245
506246
63
526059
60
70
68
Properties
EL.
%
7
86
10
44
495
3
49
19
18
7
7
Electricalconductivity% IACS
92
82101
90
9086
885565
50
403512
7
14
3
SofteningTemp.X
450
425225
480
375400
450570425
475
415430500
375
720
Coefficient ofThermal Expansion2 5 - 3 0 0 ° C X 1 0 - 6 / ° C
17.0
17.017.6
17.5
17.317.6
17.117.016.3
16.9
16.516.6
17.5
17.8
4.3
many types of motors and the considerable running costbenefits to be gained from efficiency improvements.
For most motors, the conductors in both rotor andstator windings are still made of conventional high con-ductivity copper. Where extra strength is required, particu-larly creep resistance for long reliable life at elevatedtemperatures, then alternative materials are the copper-silver, copper-chromium and copper-chromium-zirconiumhigh-strength, high-conductivity alloys. These are particu-larly useful for rotating components not restrained bylaminations such as commutators, slip rings, rotor stalksand rotor rings.
The commercial benefits of the use of energy-efficientelectric motors have been described by Brook [83] andGreenwood [84]. After considerable design improvementsin the rotor, stator, case and cooling system, the result canbe a 25-33% reduction in losses. This is achieved by
designation description
increasing the active material used, so reducing the fluxdensity and improving electrical efficiency. The reductionin internal heat developed means that less power is neededfor the fan cooling system. There is an initial extra con-struction cost incurred, but the energy efficiency improve-ments can give a payback period as short as six months fora motor in continuous use at standard industrial electricitytariff rates.
For applications involving intermittent operation withhigh starting torques, the same company have designed adevelopment of the squirrel cage motor, the rotor bars ofwhich are extended with a pipe cage. The electrical andthermal characteristics of this design give torque character-istics similar to slip-ring motors but without the main-tenance costs of the slip rings and brushgear. Abnormalvoltage drops and overload conditions can be absorbed, ascan frequent start/stop/reverse operating cycles.
CZ 108 common brass
PB 102 5°/. phosphor bronze3B 103 7V. phosphor bronze
NS 106 18'/. nickel silver
copper-2% beryllium(age hardened)
33101 copper 1.7% beryllium(age hardened)
copper 2*/. cobalt-beryllium
copper 2*i nickel-beryllium
iage hordened)
Y//////A HV150-180Y//////A. HV 160-190Y7/////AW11BO-710
V77777\ HV19O-22O
V////A, HV160-190
U777777\ HV 180-210
v//////^ HV350-400y//////>^ HV360-410
%>////f*. HV370-430TZ/ /7 / /X HV38O-450
E2Z22JHV330-380\77777K HV340-390
Y//77K HV35O-AOOV///\. H V36O-A20
I22Z22iHV195-24.5
V77777\W<I 220-270
EZZ2>HV24O-290
300 400 500 600 700 800 900 1000elastic limit, N/mm2
Fig. 16 Typical elastic limits and hardnesses for some spring materialsfor electrical purposes [79]
Fig. 17 Rotor of a 'pipe cage' electric motorThe design of the high conductivity copper rotor bars allows absorptionof abnormal voltage drops and overload conditions(By permission of Brook Crompton Parkinson Motors)
196 IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
Fig. 18 Stator and case of a high-efficiency electric motor designed touse 20% less electricity than conventional motors(By permission of Brook Crompcon, Parkinson Motors)
9.4 Copper for busbarsFor many years the standard work on the design ofbusbars has been CDA Publication 22 [85] which com-bines a useful presentation of basic design formulas withdetails of good practice. Basic DC current ratings, allowingfor heat losses by radiation and convection, are based onthe Melsom and Booth work at the NPL [86] and sub-sequent modifications. AC current ratings, allowing forskin effects of various frequencies are given, together witha detailed consideration of busbar forms and the spacingsof multiple bars. Design to meet the mechanical require-ments of fault conditions and the effects of workingenvironments are also considered. This book was out ofprint for some time and a redraft has been published,having been prepared with the assistance of members ofthe British Non-Ferrous Metals Federation High Conduc-tivity Copper Technical Committee and Balfour-BeattyPower Construction Ltd. It includes reference to improve-ments in design and construction techniques. The weld-ability of high conductivity copper by inert gas shieldedarc welding now makes such fabricated joints an easierproposition than when oxyacetylene was used.
Recently, a number of papers have been published byBurns in Australia as a result of work on variousaspects of the practicable ratings of busbars. Initial work[87] describes the results of experimental work on multiplebar three-phase systems. Much of this was done to showthat a normal maximum working temperature of 105°C ismore realistic than the existing BS 159 rather conservativelimit of a 50°C rise over an average ambient not exceeding35°C in a 24 hour period nor a peak value of 40°C. Thereis an extensive survey of the literature on the slightly ele-vated temperature, long time annealing behaviour of highconductivity coppers which is used to confirm that 105°Cis an acceptable normal maximum operating temperature.In considering heat losses from multiple bars, the usefulthermal bridging effect of high conductivity bar spacers isemphasised, as also is the benefit of increasing the emiss-ivity of the surface of copper by aging or pretreatmentwith suitable paint.
A second article [88] considers the need to extend theexisting Melsom and Booth formula for busbar ratings toinclude multiple bar installations. Factors are given for usewith up to five parallel bars per phase.
In a third paper [89] Burns determines a method of
Fig. 19 Complex heavy-duty busbar system installed to carry the highcurrents needed in a refinery(By permission of BICC Balfour Beatty Power Construction Ltd.)
Fig. 20 Copper busbar assemblythick copper plate designed to carry a load of 28Constructed throughout of 25
750 A at 12 MVA(By permission of Clark Industries Ltd.)
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986 197
calculation of multiple busbars which reconciles with thetest results previously observed. This is a slight modifi-cation to the Melsom and Booth formula and may beapplied for up to four bars in parallel carrying a total ofup to 6000 amps.
The effect of a 105°C working temperature on boltedjoints is considered to be negligible provided that thejoints were initially made using recommended practice.There is a useful tabular comparison of the weighting to beapplied to various design attributes for busbars to be usedeither in power switchgear applications or in the longerlength transmissions in bus ways. The effect of type ofpigment on the emissivity of painted busbars is also furtherconsidered, titanium dioxide being preferred both for itseffect on emissivity and as an arc quenchant, reducing thetravel of arcs initiated during fault conditions. There isalso a discussion of the various types of shape of busbarsavailable from the simple rectangular sections throughangles and channels to tubes. It is concluded that, for mostpurposes, rectangular bars are adequate whether usedsingly or in multiple.
The alternative method of calculating busbar ratingsfrom individual radiation and convection losses, aspublished by Wright [90] is considered and found to showno advantages over the single Melsom and Booth type offormula.
Other articles include consideration of electrical andthermal loading effects on both the busbars and joints [91]and a more detailed discussion of the effect of surfaceemissivity on current ratings [92].
Burns also prepared a summary paper [93] which wasincluded in a South African symposium on busbars. Muchof this work has been taken into consideration in theredrafting of the text of the book 'Copper for busbars'.
From the work of Bowers and Mantle [94] at the BNFMetals Technology Centre and others, and also from theresults of tests on busbar material recovered after manyyears service, it can be shown that 105°C is a safe oper-ating temperature so far as retention of mechanicalstrength is concerned. It is therefore possible to increasethe ratings of busbars with resultant improvements ineconomies. Many of the items of equipment to whichbusbars are connected are already operating at such tem-peratures and may at present tend to cause local nominal'overheating'. This problem would be reduced by suitableuprating of the busbars to the equipment working tem-perature.
The caution of BS 159 is probably caused more by aconcern for joint integrity than for the busbar material asthe American Standard ANSI C37, 1974 (IEEE Std 271974) recognises. This makes provision for silver surfaced(or equivalent) connecting joints. The use of silver, nickelor tin coated copper is frequent practice in the making ofbolted joints, but it is also held to be possible to makesound joints with plain copper provided care is exercisedin joint design.
It has been proposed that BS 159 be revised. If so, thenit is probable that the recommendations for joint operatingtemperatures contained in IEC Publication 694 would beimplemented or uprated. For bare copper bolted joints themaximum operating temperature is 90°C or 100°C in oil.Silver or nickel coated copper joints may operate at up to115°C (or 75°C over an ambient not exceeding 40°C).Apart from the joints, however, there is no known IECrecommendation for maximum operating temperatures forbusbars themselves.
Assembly of joints is undertaken after the application ofa light coating of petroleum jelly, and care is taken to
Fig. 21 Close up of fillet weld made in assembling high conductivitycopper busbar system(By permission of Clark Industries Ltd.)
ensure that bolting torques conform to recommendations.After considering the reduced bolt head sizes of metric fas-teners when compared with imperial sizes and similarreductions in washer diameters, it is recommended thatholes for bolts should be only 1 mm clearance above thebolt diameter instead of the approximate 2 mm previouslyused. If ever required, these joints may be dismantled formaintenance or modification.
Where it is unlikely that configuration changes willoccur after installation, it is possible to use welded joints.These may be butt or overlap joints and, given the recom-mended welding procedures now available, the risk ofembrittlement can be avoided. Due to the fusion process,of course, the copper in the heat affected zone is annealed,and due recognition of this loss of strength of cold workedcopper is required.
Copper retains advantages over aluminium of having ahigher conductivity, an oxide which is conductive ratherthan refractory, a higher strength and rigidity, especially atelevated temperatures, and, eventually, a significant resalevalue. Table 11, using data from Smithells [95] shows acomparison of the main properties of copper relative tothose of aluminium. Besides the higher conductivity, thehigher strength should be noted. This can mean that sup-ports can be placed at greater distances from each other,reducing installation expenses.
To obtain self-extinguishing characteristics under arcingconditions it has been shown [96] that copper busbars,may be spaced at half the separation distance of equivalentaluminium assemblies.
9.5 Copper foil for printed circuitsThe copper on printed circuit boards (PCBs) may be typi-cally from 5 to 35 microns thick. There are two main tech-niques used for the preparation of PCBs. The original
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
Table 11: Typical relative properties of copper and aluminium
Electrical conductivity(annealed)
Electrical resistivity(annealed)
Temperature coefficientof resistance (annealed)
Thermal conductivityat 20°C
Coefficient of expansionTensile strength
(annealed)Tensile strength
(half-hard)0.2% proof stress
(annealed)0.2% proof stress
(half-hard)Elastic modulusSpecific heatDensityMelting point
Copper(C101)
101
1.72
0.0039
3971 7 X 1 0 - 6
200-250
260-300
50-55
170-200118-1303858911083
Aluminium(1350)
61
2.83
0.004
23023 x i o - 6
50-60
85-100
20-30
60-65709002.70660
Units
% IACS
fjQ cm
/°C
W/mK/°C
N/mm2
N/mm2
N/mm2
N/mm2
kN/mm2
J/kgKg/cm3
°C
concept was to prepare a laminate copper foil on a strong,rigid insulating base. While it is possible to roll copper foilas thin as required, a satisfactory product may equally wellbe made by electrodepositing copper to the required thick-ness on a re-usable cathode. Frequently this is a stainlesssteel drum rotating slowly in the plating bath to permit acontinuous foil-stripping process. From the copper-cladlaminate the required circuit is produced by applying aninert coating where copper is required and etching awayunwanted material. It is important to achieve a good etchwithout undercutting the etch-resistant coating. Tech-niques for this had been in use for many years in the prep-aration of copper printing plates for the best qualities ofreproduction, but have been developed significantly forPCB requirements.
Instead of making PCBs by removing unwanted copper,it is now also common to electrodeposit copper only whereit is required on the finished board, an additive rather thansubtractive process. The initial coating is of electrolesscopper, and on to the required areas copper is subse-quently electrodeposited to the required thickness.
A useful summary of etching processes has recentlybeen published [97].
The practices of preparation of printed circuits are nowvery well developed and controlled. Those interested inrecent developments are recommended to contact thePrinted Circuit Group of the Institute of Metal Finishing*.
9.6 TransformersBecause of requirements for low losses and high effi-ciencies, copper remains the preferred metal for trans-former windings. Normally electrolytic high-conductivitycopper (C101) is specified but for heavy duties sometimes acontrolled proof stress material is required. For smalltransformers wound with fine enamelled wire the softnessof the standard modern high-purity copper is appreciated.
10 Conclusions
This review has described recent trends and improvementsin the production and fabrication of high conductivitycoppers and copper alloys. The complete modernisation ofthe copper industry has meant a substantial investment in
* Exeter House, 48 Holloway Head, Birmingham Bl 1NQ, United Kingdom
IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
improved refineries and new plant, especially that for theproduction of high conductivity copper. The producersremain confident that they will be able to serve the needsof the electrical engineering industry for the foreseeablefuture.
Extensive references have been made to the wide rangeof materials available with a wide selection of productforms and tempers from which to choose. It has beenimpossible to cover all possible end uses and the factors tobe considered in selecting the correct combination ofproperties for optimum efficient materials selection pro-cedures. If further technical advice is required, potentialusers should consult the manufacturers or the InformationDepartment of the Copper Development Association.
11 Acknowledgments
The author is grateful to the organisations supplying theillustrations and for constructive comments from membersof the High Conductivity Copper Technical Committee ofthe British Non-Ferrous Metals Federation.
12 References1 'Copper in the electrical industry' Symposium organised by the Cop-
per Development Association (CDA), Orchard House, Mutton Lane,Potters Bar, Herts. EN6 3AP, UK
2 'The effect of research and design on the use of copper in electricalindustry' CDA Symposium, 1962
3 TEMPLE, S.G.: 'Recent developments in properties and protection ofcopper for electrical uses', Met. Rev., 1966 2, pp. 47-60
4 'Modern aspects of copper in electrical engineering', CDA Sympo-sium, 1968
5 ARMSTRONG-SMITH, G.: 'A review of the latest techniques for theproduction of primary copper and the influence on the product andits end uses', in 'Copper and its alloys Conference', Institute of Metals,1970, paper 1
6 ARMSTRONG-SMITH, G.: 'The spiral elongation test for copperannealability: an examination of some of the controlling factors', J.Inst. Met., 1971, 99, pp. 325-334
7 A1NSWORTH, P.A., and THWAITES, C.J.: 'A high strength tin-bronze with improved electrical conductivity' International TinResearch Institute Publ. 411, 1970
8 WELDON, B.A., TOWERS, J.A., and POTTON, A.M.: 'Nickel silveras an engineering material', Metals & Materials, 1970, 4, pp. 299-303
9 OPIE, W.R., HSU, Y.T., and SMITH, R.J.: The properties of copper-magnesium-zirconium and copper-chromium-zirconium-magnesium',J. Inst. Metals, 1970,99, pp. 204-207
10 STEVENS, R.J.: 'Production of copper rod directly from cathodes byway of the Asarco furnace and Southwire continuous casting system'in 'Copper and its alloys conference', Institute of Metals, 1970, paper 8
11 'High conductivity coppers — technical data' CDA Technical NoteTN27, 1981
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Technologist, 1984, 16, (4), pp. 185-19118 STALEY, M.A., SMART, E.F., and WISE, M.L.H.: 'Machinability of
high conductivity coppers', in 'Copper 83 conference', Metals Society,1983, paper 30
19 NOGUCHI, K., ISHIGAUM, Y., and SAKAI, S.: 'The roles ofcopper products manufacturers in the production of super-conductors', ibid., paper 33
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199
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25 WILL1NGHAM, J.A.: 'Copper-phosphorus based (self fluxing)brazing alloys used for joining copper and its alloys', ibid., paper 48
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28 WEST, E.G.: 'Copper and its alloys' (Ellis Horwood Ltd., Chichester1982)
29 CROSSON, C.C.: 'The evolutionary development of Palabara MiningCo. Ltd.' in 'Copper 83 conference', Metals Society, 1983, paper 6
30 COLEMAN, R.L.: 'Developments in status and trends in mineralbeneficiation of copper ores', ibid., paper 8
31 HONKSATO, J., TUOMINEN, T., and JUUSELA, J.: 'Outokumpaflash smelting — a modern and advanced copper smelting process',ibid., paper 10
32 SUSUKI, T., and GOTO, M.: The Mitsubishi process after eightyears improvement', ibid., paper 13
33 JACOBI, J.S.: 'How to modernise existing copper smelters and refin-eries', ibid., paper 14
34 CALLCUT, V.A.: 'New British Standards publications relating tocopper refinery shapes', Metallurgist & Materials Technologist, 1984,11,(10), pp. 504-506
35 CALLCUT, V.A.: 'Raw and wrought copper', BSI News, 1982, pp.7-8
36 BSDD 96:1984. 'Methods for sampling higher purity coppercathodes and preparing analytical samples'
37 BSDD 95: 1984-86. 'Analysis of higher purity copper cathode (Cu-CATH-1)'
38 HIRSCHFELDER, H.D.: 'Comparing copper rod casting and rollingprocedures', Wire, 1978, 27, (2), pp. 48-54
39 PERLMAN, L.M.: 'Copper wire rod — the changing industryenvironment', Wire Int., 1980, pp. 66-69 (paper 6 from conference'Present and future markets for Copper', 1979, CDA)
40 DOMPAS, J.M.: 'Contirod, a special method for producirtg highquality wire', Erzmetall, 1975, 28, (7-8), pp. 322-330 (also ATB Metall,1976,16, (2), pp. 92-100)
41 RANTANEN, M.: 'The Upcast method of producing copper wire',Wire Ind., 1976, 43, (511), pp. 565-567
42 ATTRILL, W.H.: 'The extrusion of copper-based alloys', Metallurgia,1978, 45, (5), pp. 258, 260 and 262
43 WATSON, M.I.M.: 'Copper and copper alloy extrusions', Metallur-gist & Materials Technologist, 1980,12, (11), pp. 611-614
44 WOOLLASTON, A.K., and STAMFORD, M.S.: 'High conductivitycopper alloy forgings and stampings', Metallurgia, 1977, pp. 100-104
45 ADLINGTON, A.G.: 'Modern production processes for copper andcopper-alloy sheet and strip', Sheet Metal Industries, 1976, 53, (2), pp.79-84 and 98
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47 HARPER, S., CALLCUT, V.A., TOWNSEND, D.W., andEBORALL, R.: 'The embrittlement of tough pitch copper windings inhydrogen cooled generators', J. Inst. Metals, 1961-2, 90, (11), pp.414-423
48 BS 5899: 1980 (ISO 2626) 'Hydrogen embrittlement test for copper'49 ' ' O F H C Oxygen-free high conductivity coppers' (Amax Copper Inc.,
New York, USA)50 ARCHBUTT, S.L., and PRYTHERCH, W.E.: BNFMRA (Now BNF
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York 1968)53 BOWERS, J.E., and LUSHEY, R.D.S.: 'The creep and tensile proper-
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55 GOHN, G.R., HERBERT, G.J., and KUHN, J.B.: 'The mechanicalproperties of copper-beryllium alloy strip', ASTM STP 367, 1964
56 'Creep behaviour of copper — 2% beryllium wire at slightly elevatedtemperatures', Trans. ASM, 1964, 57, pp. 362-364
57 'The fatigue properties of beryllium-copper strip and their relation toother physical properties', Proc. ASTM, 1946, 9, pp. 471-474
58 SARGENT, R.M.: 'Cavity formation in copper-chromium alloys', J.Inst. Metals, 1961-2,96, pp. 197-201
59 "Amzirc' copper-zirconium alloy' (Amax Copper Co., New York,
USA, 1977)60 TAUBENBLAT, P.W., MARINO, V.J., and BATRA, R.: 'High
strength high conductivity 'Amzirc' copper and Amax-MZC copperalloy (Cu-Zr and Cu-Cr-Zr-Mg)', Wire J. Int., 1979, 12, (4), pp.114-118
61 CALLCUT, V.A.: "Versatile brass', Metallurgist & Materials Tech-nologist, 1984, 16, (9), pp. 471-474
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197064 'Coppers and copper alloys—composition and properties' CDA Tech-
nical Note TN 10, 198665 'The density of annealed (wrought) tough Pitch high conductivity
copper' British Non-Ferrous Metals Federation Paper HC 72/611,March 1972
66 THORNTON, C.H., HARPER, S., and BOWERS, J.E.: 'A criticalsurvey of high temperature mechanical property data for copper andcopper alloys' INCRA Monograph XII, 1983, International CopperResearch Association, New York and Potters Bar
67 MURPHY, M.C.: 'The engineering fatigue properties of wroughtcopper', Fatigue Eng. Mater. & Struct., 1981,4, (3), pp. 199-234
68 'The weathering of copper' CDA Information Sheet IS25, 198169 LEIDHE1SER, H.: 'The corrosion of copper, tin and their alloys'
(John Wiley & Sons Inc., New York, 1971)70 BENSON, N.D., MCKEOWN, J., and MENDS, D.N.: 'The creep
and softening properties of copper for alternator windings', J. Inst.Metals, 1951-2,80, pp. 131-142
71 THWAITES, C.J.: 'Soft soldering handbook' (International TinResearch Institute, 1972)
72 DAWSON, R.J.: 'Brazing copper and copper alloys' CDA TechnicalNote 4, 1970
73 'The joining of copper and copper alloys' CDA Technical Note 25,1980
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75 COLLOMS, M.: 'Crystal clear answer to cable 'sound' problems',Electronics Times, 1984, p. 279
76 TURNER, H.W. and TURNER, C : 'Copper in electrical contacts'CDA Technical Note TN 23, 1980,13 pp.
77 PUCKERT, F.: 'Werkstoffe und halbzeug fur systemtrager — eigen-schaften und anforderungen', Symposium — Kupfer-Werkstoffee,Deutscher Gesellschaft fur Metallkunde e V, April 1985, paper 4
78 WOOLLASTON, A.K. (Ed.): 'Copper alloy spring materials' CDATechnical Note TN12, 1972
79 'Delcan alloy brochure' (Barker and Allen Ltd, Birmingham 1980)80 LANGER, J.: 'Eigenschaften und anwendung von Kupferlegierungen
als Federwerkstoffe fur die Electoidustrie', Symposium Kupfer-Werkstoffe 1985, paper 3
81 HAUSCH, G.: 'Hochfeste Kupferwerkstoffe — neuer Werkstoffent-wicklung, ibid., paper 14
82 KNIGHTS, D.E.: 'The benefits to industry of improved efficiencymotors', ERA Technology Ltd. Report 80-8, 1981
83 BROOK, B.: 'Energy efficient electric motors', Electr. Rev., 1982, 210,(11), Electr. Times, 1982, p. 14, and Eng. Mater. & Des., 1981, Septem-ber, pp. 37-39
84 GREENWOD, P.B.: 'Energy efficiency', BCPM Rev., 1982, Electrexissue, p. 4
85 'Copper for busbars' CDA Publication 22, 198486 MELSOM, S.W., and BOOTH, H.C.: 'The current carrying capacities
of solid bare copper and aluminium conductors', J. IEE, 1924, 62, pp.909-915
87 BURNS, R.L.: 'Current rating of open type three-phase rectangularbusbars by actual test', Electr. Eng. Sept. Oct. Nov. & Dec. 1976 &Feb. 1977 (reprinted by Copper Development Association of Aus-tralia, Publication 219/76)
88 BURNS, R.L.: 'AC current rating of open rectangular copper busbarsby calculation' ibid. June 1977 (reprinted by Copper DevelopmentAssociation of Australia, Publication 221/77)
89 BURNS, R.L.: 'Determination of current carrying capacity of rec-tangular copper busbars using a method of calculation which recon-ciles with test results' Copper Development Association of Australia,Publication 224/77
90 WRIGHT, E.G.: 'AC current ratings of rectangular conductors',Electr. Rev., 1976, 199, (5)
91 BURNS, R.L.: 'Factors affecting the use of copper and copper alloyelectrical conductors due to electromagnetic thermal loading' in '1977AEMA conference', Copper Development Association of Australia,Publication 255/78
92 BURNS, R.L.: 'The effect of surface emissivity on the current rating ofbare copper conductors' (McKechnie Brothers, South Africa (Pty)Ltd., 1978)
93 BURNS, R.L.: 'Determination of current carrying capacity of rec-tangular copper busbars' Electr. Eng., March & April 1978, Copper
200 IEE PROCEEDINGS, Vol. 133, Pt. A, No. 4, JUNE 1986
Development Association of Australia reprint, also Paper 1 in 'Copperfor Busbars' Symposium, Johannesburg, Nov. 1978 (McKechnieBrothers, South Africa (Pty) Ltd.)
94 BOWERS, J.E., and MANTLE, E.C.: 'Copper for transformer wind-ings', J. Inst. Metals, 1961-2, 91, pp. 142-146
95 SM1THELLS, C.J. in BRANDES, E. (Ed.): 'Metals reference book'(Butterworths, 1983)
96 RUSKIN, A.M.: 'On the safety of copper and aluminium busbars',Metallurgist & Materials Technologist, 1983, IS, (7), p. 358 (also pre-sented at 1975 IEEE Technical Conference on Industrial and Com-mercial Power Systems, Toronto)
97 FITZPATRICK-BROWN, A.J.: 'Printed circuits: etching processes'.Electronic Production, 1985, August, p. 28
Abstracts of IEE Reviews published in other Parts of the IEE PRO-CEEDINGS
Optical-fibre sensorsG.D. PITT, P. EXTANCE, R.C. NEAT, D.N.BATCHELDER, RE. JONES, J.A. BARNETT and R.H.PRATT
IEE Proc. J, Optoelectron., 1985,132, (4), pp. 214-248Optical-fibre development to date has concentrated ontheir use in systems for telecommunications and datatransfer. The realisation that optical fibres could also beused for sensors and sensing systems has increased rapidlyin recently years. Judged by the large number of pub-lications in this area the research effort is extensive, butfew systems have yet been put to practical use. A criticalreview of recent developments is therefore useful at thisstage. Several examples of fibre-optic sensors are given,where their selection has been dependent on the systemshowing practical viability, and data having been obtainedrelevant to operation in a real (as distinct from purelylaboratory) environment. Devices ranging from simplefibre-optic switches and pollution monitoring equipment,to highly sensitive acoustic, magnetic and rotation sensingsystems are emerging, where an understanding of modaland polarisation effects in single-mode fibres is necessary.At present each sensor system tends to be aimed at specificapplication areas, where the form of acceptance by the userwill vary. It is emphasised that such developments requireengineering inputs at the earliest possible stage. The use ofoptical fibres for direct actuation of valves and sensors hasnow closed the optical control loop.
'Light' electronics, myth or reality?PROF. J.E. MIDWINTER
IEE Proc. J, Optoelectron., 1985,132, (6), pp. 371-383The paper examines the scope for digital optoelectroniccircuits to penetrate or replace electronic ones and dis-cusses the motivations for so doing. It is based upon anInaugural Lecture delivered at University College Londonin June 1985.
Semiconductor memoriesJ.N. BARRY and R.G. GEORGE
IEE Proc. E, Comput. & Digital Tech., 1986, 133, (1), pp.8-30The paper reviews the evolution of semiconductor memor-ies from the early 1960s to the present day. It includesdescriptions and comparisons of the principal types ofmemory presently available, followed by a survey of themain semiconductor technologies used in the fabrication ofVLSI memories. Typical cell designs are first presented,starting with basic electrical designs and proceeding toshow how these may be implemented as layouts for a prac-tical chip. The fabrication steps required to realise suchcells within a memory chip are described. The design andorganisation of complete memories is then discussed; thedesign of principal types of read-only memories, read/writememories, content-addressable memories and serial mem-ories being included. The remainder of the paper dealswith the important topic of specification and timingrequirements of memories; followed by a general review ofdifferent types of semiconductor memory, both from theapplications point of view and as a comparison of theirprincipal characteristics with those using alternative fabri-cation technologies. Finally, there is brief projection offuture developments. The paper is written throughout pri-marily from the technological rather than the applicationviewpoint.
Correlation algorithms, circuits and measurement applica-tionsJ.R. JORDAN
IEE Proc. G, Electron. Circuits & Syst., 1986, 133, (1), pp.58-74The theory, implementation and industrial measurementapplications of the correlation functions are described. Theimplementation methods discussed have been restricted tothose using electronic circuits and software techniques.Sufficient background theory has been presented to enablemeasured functions to be interpreted and sources of errorlocated. The industrial importance of the correlation func-tion is reflected in the wide range of applications described.
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