The OfficialTitanium Pro SeriesICT Test Report

Spring Contact Probes are compliant components that provide anelectrical contact path between a testpoint on a PCB and the automated testequipment (ATE). Probes are installedin a fixture, a customized interfacebetween the PCB and ATE. Probesallow multiple test points with varyingheights and configurations to beaccessed simultaneously as the PCBcontacts the test fixture and the probescompress. Circuit path integrity is crit-ical for accurate testing. The perform-

ance of the probe is vital. It is thephysical connection to the PCB testpoint and the only part of the systemthat is mechanically dynamic andelectrically indispensable.

The primary current path of aprobe is from the plunger to the barreland then to the receptacle. The cur-rent then transfers from the receptaclewire termination through the fixturewiring to the tester. Accurate currenttransfer within the probe is dependenton the physical contact of the probe'scomponents. They must contact eachother in a repeatable fashion.

Mechanical obstructions cancause poor electrical functioning ofthe probe and even cause completeelectrical failure. If the plunger doesnot contact the barrel, the currentmust flow through the relatively highresistance spring, causing elevatedresistance readings and false opens.

This phenomenon occurs in twoways. First, when the plunger is com-pressed on the spring in such a man-ner that the plunger does not contactthe barrel (centering) and second,when contaminants become trappedinside the barrel and insulate theplunger from the barrel. The resist-ance of the probe will also vary fromactuation to actuation, in relation tothe plunger/barrel contact point andcleanliness of this point. Variations inresistance will occur when smallamounts of contamination are trappedbetween the plunger and barrel orwhen the plunger or barrel plating isworn to the degree that the base mate-rial is exposed and oxidized.

IntroductionThe original ICT probe design

was created to address the probe-

related challenges of In-Circuit

Testing. The introduction of the

ICT Probe Series was the first fun-

damentally new probe technology

in over 30 years, benefiting test

personnel by surpassing perform-

ance levels obtained from the

previous industry standard probe

designs. The Titanium Pro ICT

Series continues the revolution of

high performance probe design by

refining the ICT concept to achieve

an even greater performance

threshold. Previously unattainable

results are realized through a

stronger, more robust design and

new plating options that are more

equipped to handle and excel in

the typical rigors of today's In-

Circuit Test environment. This

report documents the extensive

internal testing program for the

Ti-Pro ICT Series. The test results

validate our claim that test person-

nel will realize significant fixture

performance gains using the

Ti-Pro ICT Probe Series.

Spring Probe Function in In-Circuit Test

TypicalCurrentFlow

Historically, probe design hasfocused on biasing techniques toensure internal contact between theplunger and barrel, attempting to prevent elevated resistance and largevariations in resistance. This perform-ance aspect is important because

relatively small varia-tion in resistance, volt-age, and current must bemeasured on the PCBby the test equipment. Ifthe variation in theprobe’s resistance isgreater than the allow-able signal variationbeing measured, the testequipment will rejectthe PCB. This falseopen causes a goodboard to be rejected.

In addition to elec-trical performance,pointing accuracy anddurability are crucialaspects of probe per-formance. Correct regis-tration of the fixture tothe target is essential forsuccessful contact. Theinherent accuracy of theprobe plays a consider-able role in the totalaccuracy of the systemand has implications forprobe life. Poor fixtureto target registration cancause increased sideloadforces on the probe, pre-maturely wearing com-ponents and increasingstress on the spring.Specifically, the plungerto barrel contact surfaceplating will wear quick-er and plunger tips andedges can prematurelywear or otherwise be compromised.

Durability is the probe's capacityto resist contaminated environmentsby functioning properly in a consistentmanner. Contamination can take theform of flux residues and particulatematter from the board productionprocesses or the environment.Contamination can work its way intothe internal portion of the probe, creat-ing an insulating effect by lining theplunger and barrel contact points. Theprobe then suffers from variable orvery high resistance. In addition, theinternal contamination trapped in thespring cavity becomes an abrasive gritthat wears the internal platings of theprobe and barrel, and causes prematurespring failure.

The inherent flaws of conven-tional probe designs arise fromtradeoffs taken to improve one per-formance aspect to the detriment ofanother. These designs incorporatesome form of internal biasing mech-anism to ensure electrical contact.Biasing mechanisms force theplunger tail to one side of the barrelby use of a bias ball with a bias cutplunger tail, a bias cut plunger tailonly, or a biased spring design.Forcing the plunger tail to one sidetilts the plunger within the barrel,creating the worst case geometry forpointing accuracy. In addition, byforcing the plunger to one side, bias-ing opens a larger gap between theplunger and barrel at the barrel topallowing contamination easier entryinto the internal portion of the probe.In bias designs, pointing accuracyand durability are sacrificed for elec-trical performance.

The ICT design features a barrelmodification process that machinesthe barrel top into four bifurcatedbeams of precise length and profile.The beams are then formed to perfectcenter by a special manufacturingprocess that provides a compliant

pressure fit between the beams andplunger resulting in a zero workingclearance between the plunger andbarrel. This seemingly simple innova-tion, adapted and refined from provenpin and socket connection technology,is exceedingly effective at providingsubstantial performance gains.

In contrast to bias designs thathave only one small and highly variable contact point, the bifurcatedbeams provide full radial contact(360°) to the plunger shaft, providingthe most stable current path possible.This enlarged contact area neverchanges as the probe is compressed.It is always the plunger shaft to barrel beams, which results in thelowest, most consistent resistance of any probe.

Since the four bifurcated beamsare formed to perfect center, theplunger shaft is positioned in axialand radial alignment with the barrelproviding the best possible pointingaccuracy. In contrast, bias designsintentionally force the plunger offaxis to achieve acceptable electricalperformance.

ICT Design

The ICT design is the first fundamentalnew probe technology offered since bias-ing was first introduced. This new designaddresses the three primary aspects ofperformance important for In-CircuitTesting: electrical resistance, pointingaccuracy, and durability.

Probe Design and Performance

The Titanium Pro ICT Series fea-tures an improved plunger design anda corresponding new beam design.During the manufacturing process, thebifurcated beams are customized foreach plunger, eliminating any manu-facturing tolerance between theplunger’s outside diameter and theinside diameter of the beams. In thenew design, the retained length of theplunger is reduced by .100" (2.54mm),allowing for a longer spring. Thus,higher forces are obtainable whileeliminating the tendency for prematuremechanical failure, specifically whenover stroking occurs.

The Ti-Pro ICT Probes featureour new G2 proprietary barrel materialand plating. Our G2 barrel was de-signed to increase the friction forcebetween the inside of the receptacleand the outside of the barrel. Inessence, it has a "less slick" fit. The Ti-Pro Series probes are less likely to"walk out" during test and have anextraction force – 25% greater than

probes manufactured with an unplatedsurface on the outside of the barrel.

The Ti-Pro Series probes also feature our new revolutionary plungerplating, with a plating hardness of400 knoop, over TWICE as hard as the standard cobalt gold (180knoop) commonly used on probes. As with all platings, it is the additivesof the plating bath that determine thehardness of the electro-deposit.Through detailed design experiments,we believe we have developed thehardest electro-deposited gold obtain-able. As a result, the Tri-Pro ICTSeries is less susceptible to wear fromside loading and is more equipped towithstand the harshness of today's In-Circuit Test environments.

These new design features makethe Ti-Pro Series by far the mostrobust in-circuit test probe. The compliant fit between the plungerand barrel, the gentle wiping of theplunger shaft during deflection, andthe harder gold plating vastly reduce

wear commonly seen as ablack surface on the shaft of the plunger, resulting inlonger probe life. The longerspring volume, correspondinghigher spring forces, andabsence of grit in the internalportion of the probe all contribute to increasingmechanical spring life.

The Ti-Pro ICT designoffers In-Circuit Test perform-ance potential not possiblewith conventional designs.The results of our comparativetest program demonstrate anddocument the performancecapabilities the Titanium ProICT Series Probes comparedto conventional technology.

Test ProgramThe complete test pro-

gram included exhaustive laboratory testing of IDI Ti-Pro ICT probes against topIn-Circuit Test product offer-ings from the various primaryprobe vendors. Tests weredesigned to address the mostrelevant performance criteria,mimicking the variety of conditions found in typicalinstallations. The various elec-trical, pointing accuracy, anddurability tests are describedhere with documented resultsand stated conclusions in thefinal section.

The Titanium Pro Advantage

The zero working clearancebetween the plunger and barrelcloses the pathway for contami-nation to enter the internal por-tion of the probe. This has a dra-matic impact on long-term electri-cal performance and durability ofprobes in contaminated environ-ments. The beams apply a lightforce to the plunger shaft, wipingcontamination from the shaft asthe plunger is stroked.

Tests measuringaverage probe resistance(Graph 1) and resistancevariation per probe(Graph 2) over 200kcycles were conducted.As shown on Graph 1,the average resistance ofthe Ti-Pro ICT probes isless than the competitorprobes. The Ti-Pro ICTprobes will more likelyremain within the allow-able tolerance rangewhen measuring sensi-tive components duringIn-Circuit Test, over thelifetime of the probe.Graph 2 uses the sametest data, but demon-strates the total resist-ance variation of eachprobe over 200k testcycles. The smaller thespread of resistance val-ues, the more consistentthe resistance. The ICTprobes exhibit a tightrange of resistance com-pared with competitorprobes resulting from theconstant circuit paththrough the probe.

Electrical Characteristics

Resistance ComparisonMilliohms

100.0

90.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0

10.0

0.0

MAXAVEMIN

QA ECT INGUN IDI ICT SERIES

Probe Manufacturer

100.0

95.0

90.0

85.0

80.0

75.0

70.0

65.0

60.0

55.0

50.0

45.0

40.0

35.0

30.0

25.0

20.0

15.0

10.0

5.0

0.0 QA ECT INGUN IDI ICT SERIES

Probe Manufacturer

Milliohms

Graph 1 – Minimum, Average, and Maximum Resistance100 mil center, .250” travel probes over 200,000 cycles

Graph 2 – Minimum, Average, and Maximum Resistance Variation100 mil center, .250” travel probes over 200,000 cycles

Pointing accuracy was deter-mined by measuring sixteen pieces of each probe series before and after200,000 cycles. The cumulativeeffects of test usage are thus factoredinto this measurement, giving a truerpicture of the probes' typical pointingaccuracy. Probes were placed in a 3-wheel concentricity gage, then rotatedto measure the plunger tips' maximumdistance from center by an opticalcomparator. The test setup is shown inFigure 1. The value produced by thismeasurement, total indicator runout(TIR), is halved and expressed aspointing accuracy, or deviation fromtrue center.

Graph 3 is a radar plot of eachprobe's pointing accuracy depicted as

a data point located a distance fromthe graph's center (true center). Thedata points are connected and colorfilled to illustrate the scatter of strikestypical for each probe type. Graph 4overlays the results for comparisonand displays the before cycling andafter 200,000 cycles.

It is seen that the Ti-Pro ICTSeries displays the tightest scatterpattern of any probe type. Conse-quently, the Ti-Pro ICT probe is morelikely to hit targets on center result-ing in highly reliable contact andoverall fixture performance. The likelihood of glancing off, misalign-ment or completely missing targets issubstantially diminished resulting inimproved yields.

Pointing Accuracy

0.0050

0.0045

0.0040

0.0035

0.0030

0.0025

0.0020

0.0015

0.0010

0.0005

0.0000

1

QA PRP Series

2

3

4

5

6

7

89

10

11

12

13

14

15

16

0.0050

0.0045

0.0040

0.0035

0.0030

0.0025

0.0020

0.0015

0.0010

0.0005

0.0000

1

INGUN

2

3

4

5

6

7

89

10

11

12

13

14

15

160.0050

0.0045

0.0040

0.0035

0.0030

0.0025

0.0020

0.0015

0.0010

0.0005

0.0000

1

IDI ICT Series

2

3

4

5

6

7

89

10

11

12

13

14

15

16

0.0050

0.0045

0.0040

0.0035

0.0030

0.0025

0.0020

0.0015

0.0010

0.0005

0.0000

1

ECT POGO PLUS

2

3

4

5

6

7

89

10

11

12

13

14

15

16

Graph 3 – Individual Pointing Accuracy

Graph 4 – Combined PointingAccuracy 100 mil Center,

.250” Travel Probes

Figure 1 – TIR Setup

Difference between true center and tip position

3 wheels center probe

Rotate

QA PRP Series

ECT PogoPlus

INGUN

IDI Ti-Pro ICT0.0050

0.0045

0.0040

0.0035

0.0030

0.0025

0.0020

0.0015

0.0010

0.0005

0.0000

1

Pointing Accuracy

2

3

4

5

6

7

89

10

11

12

13

14

15

16

The durability test consisted of anelectrical test similar to that performedfor electrical characterization. The fix-ture receptacle holes were drilled witha 2.5° angle from vertical to induceside-load. In addition, contaminationwas applied directly to the probes atintervals throughout the test. The con-

taminationconsistedof solderflux; steel,plastic andaluminumfilings;

various grades of abrasive compounds;and ordinary dirt.

Graphs 5 and 6 show results ofthe contaminated electrical test. Notethe resistance level of the Ti-Pro ICTprobes as compared to competitors.Even under severe contamination, theICT exhibits significantly lower resist-ance than competitor probes. Thisindicates contamination was blockedfrom entering the internal probe cavitythus preventing contact issues andconsequent high resistance.

250

200

150

100

50

0

Milliohms

IDI Ti-Pro Series QA INGUN

Probe Manufacturer

Probe Variation - Graph 6

ECT

Milliohms

250

200

150

100

50

0IDI Ti-Pro Series QA INGUN

Probe Manufacturer

ECT

Contamination Test Resistance - Graph 5

MAXAVEMIN

Graphs 5 and 6 – Contaminated Environment Test

The tested probes were dissected to revealthe degree of internal contamination. As predicted, the ICT internal spring/plunger cavity was free from contamina-tion. Competitor probes allowed contami-nation to enter the cavity, allowing thepossibility of internal contact problems.

ECT QA

INGUN ICT Ti-Pro ICT

Durability

The Ti-Pro ICT Probes outper-form all other probes in every criticalaspect of In-Circuit Test; pointingaccuracy, consistent resistance, lowresistance and durability. As a result,test yields increase as false openscaused by probe failures are dramati-cally decreased, if not eliminated.

Consider the following: What impact would an increase

of yields from 92% to 97% have onyour company if you tested 5000boards in a week?

The Matrix shows a difference of 250 boards (4850 - 4600 = 250).

1. The 250 boards must be re-tested to determine if they are in fact, bad.

2. The cost of retest is expensive. Cost of Retest = Machine Time + Labor + Opportunity Cost of not TestingGood Boards Accurately (lost through-put)

3. Assume 50% of first pass rejected boards are actually good.

4. $50/hr labor; $250/hr machine time; $300/hr opportunity cost; Test time = 5 minutes; then $600/hr x 5/60 hrs = $50 Cost per Test

5. 0.50 x 250 x $50 = $6,250

6. If 5000 boards are tested weekly: 52 x $6250 = $325,000

7. In this example a 5% increase in yields results in an annual savings of $325,000.

Conclusions

Titanium-Pro ICT Series improvesyields and saves money!

Number of Boards TestedFirst Pass Yield (%) 50 100 500 1000 5000 10000 25000

98 49 98 490 980 4900 9800 24500

97 49 97 485 970 4850 9700 24250

95 48 95 475 950 4750 9500 23750

94 47 94 470 940 4700 9400 23500

93 47 93 465 930 4650 9300 23250

92 46 92 460 920 4600 9200 23000

91 46 91 455 910 4550 9100 22750

90 45 90 450 900 4500 9000 22500

89 45 89 445 890 4450 8900 22250

88 44 88 440 880 4400 8800 22000

87 44 87 435 870 4350 8700 21750

86 43 86 430 860 4300 8600 21500

85 43 85 425 850 4250 8500 21250

80 40 80 400 800 4000 8000 20000

75 38 75 375 750 3750 7500 18750

IDI's Life Cycle Testers use a modified 4-wire Kelvintest. Two wires are soldered to the receptacle and twowires are soldered to a contact plate, typically sterling silver. During measurements, two wires inject a constantcurrent into and out of each probe/receptacle, and a sepa-rate pair of wires convey the consequent voltage drop.

The voltage drop includes:

1. The resistance of the contact plate.

2. The constriction resistance between the probe and thecontact plate.

3. The resistance between the probe and the receptacle.

4. The resistance of the solder joints.

The current source forces a constant 25 milliamps of current during setup and testing with a precision shunt.

The standard contact plate for a life cycle test is sterlingsilver. This material is economical, low in resistance, andhas good corrosion resistance properties. Contact platesmay also be fabricated from either half hard berylliumcopper plated with .000050" gold (50 micro inches) over.005" silver, or hardened steel. The type of plate we usedis determined by the test. For white paper testing, the sterling silver plate is used.

There were two separate life cycle tests run on probes forthis paper.

Standard TestThirty-two (32) receptacles are mounted in a manner simi-lar to actual field use ¾ vertical, point up orientation,press fit to specifications ¾ into a G-10 fiberglass matrixblock. The receptacles are populated with probes.

A machine tool slide guided sinusoidally-oscillated sterlingsilver contact plate compresses the probes within .001" ofthe rated stoke. At setup, the rated stroke is verified with abuilt in dial indicator. A precision 25,000 step per revolu-

tion micro-stepping motor cycles, stops and registers thecontact plate within .001" of the rated stroke. Resistancemeasurements on each probe are taken every 1,000 cycles.

In addition to testing resistance, the life cycle tester deter-mines loss of stroke (resulting from spring failures or other-wise). The slide guided contact plate incrementally releasesprobe stroke at 10% length intervals from the rated stroke.Continuity is checked at every interval, on every probe. Anerror message similar to "Probe 4 has lost 10% of its ratedstroke" is printed on the report should a failure be detected.Every 20,000 cycles, loss of stroke is checked.

2.5° Side Load TestThe mounting holes in the G-10 fiberglass block aredrilled at a 2.5° angle. The receptacles and probes are theninstalled in the block. The tip of the plunger is offset0.0144" from true center.

tan 2.5° = Horizontal OffsetPlunger Extension

0.04366 = x.330

x = 0.0144"

This test simulates wear from side loading. Resistancereadings are taken every 1000 cycles for the entire200,000 cycles of the test. Stroke loss is tested every5,000 cycles throughout the 200,000 test.

Contaminated Environment TestA contamination mixture is created of equal parts surfacegrinder dust, bench grinder shavings, cast iron drill shav-ings, and Kansas City road dirt mixed in a rosin core flux.The mixture is applied to the plunger tips and shaftspretest. Resistance is measured every 1,000 cycles for theentire 100,000 cycles of the test. Loss of travel and springforce are analyzed every 5,000 for the length of the test.

Appendix 1: Life Cycle Test Methodology

Measurement:IDI uses a 3-wheel concentricity gage to hold the probe atthe top of the barrel. The center point of the plunger tip ismeasured at the minimum and maximum location througha 360° rotation using an optical comparator at 20x magni-fication. This result is the TIR (Total Indicator Runout).One half of the TIR is the pointing accuracy. A probeexhibiting TIR of .003" will exhibit hit range within ±.0015" of its center.

The pointing accuracy of a probe is defined as the varia-tion in actual location of the probe tip from test to test andis internal to the probe.

There are three primary factors that determine pointingaccuracy:

1. Working clearance between the plunger and barrel.

2. Retained length of the plunger in the barrel.

3. Extended length of the plunger.

In all previous designs, the plunger sits at an angle in thebarrel due to the working clearance. It is this angle andthe base location of the angle that determine pointingaccuracy.

Pointing Accuracy Calculation – Standard DesignIn a standard probe design, the clearance between theplunger and the barrel is exactly the same at the top of the barrel as it is at the bottom or tail of the plunger insidethe barrel. Therefore, the centerline of the plunger and thecenterline of the barrel will cross at 1/2 the retained lengthof the plunger.

The nominal working clearance on a Size 25 (100-mil cen-ter, .250" max. travel) probe is .002". The retained lengthis nominally .335", and extended length is .330". Pointing

accuracy is calculated by two similar triangles. The firsttriangle has a y-axis length of .335/2 = .1675 (1/2 theretained length), and an x-axis length of .002/2 = .001 (1/2the working clearance). This allows the maximum angle(q) calculation at which the plunger sits in the barrel.

Tan q = .001/.1675Tan q = .00597

q = .342°

The nominal pointing accuracy is calculated as follows.The y-axis of the triangle is equal to 1/2 the retainedlength of the plunger plus the extended length of theplunger (.335/2 + .330) or .4975". The angle of theplunger is .342°.

Tan .342 = x /.4975.00597 = x /.4975.00297 = x = Pointing Accuracy

The pointing accuracy for a Size 25 probe is .003". Thismeans that the tip of the plunger will hit within a radius of.003" from the centerline of the probe barrel. The formu-las above may be simplified to:

e = ± c (a/b + .5) where e = pointing accuracy

c = working clearance = .002

a = extended length = .330

b = retained length = .335

e = ± .002 (.330/.335 + 1/2)

e = ± .002 (.985 + .5)

e = ± .002 (1.485)

e = ± .00297

e = ± .003

Appendix 2: Pointing Accuracy Measurement & Calculation

Pointing Accuracy Calculation:SX DesignWith the addition of the SX crimp tothe barrel, the point at which the centerline of the probeintersects the centerlineof the barrel is shiftedcloser to the top of thebarrel. The centerlineintersection shift occursbecause the clearance atthe top of the barrel istighter than the clear-ance at the end of theretained length. Thisshortens the length ofthe y-axis improving thepointing accuracy. Thetotal working clearance

Appendix 2 (continued)

in an SX probe is .00125" (.001" atthe plunger tail and .00025" at the top of the barrel). Consequently, the centerline of the plunger crosses

the centerline of the barrel at 4/5 or(.00025/.00125) from the top of thebarrel. The pointing accuracy of anSX probe is calculated as follows:

Tan q = c/(4/5*b) center line crosses at 4/5 of retained lengthTan q = .00125/(4*.335/5) b = retained length - .335Tan q = .00466 c = working clearance - .00125

q = .267°

Tan .267 = e / (a + b/5) where e = pointing accuracye = Tan .267 (.330 + .335/5) a = extended length of plungere = Tan .267 (.397) b = retained length of plungere = .0019"

Most competitors' designs (QA roll top, ECT Pogo Plus) can be calculated accordingly.

Pointing Accuracy Calculation:Titanium Pro Series ICT Design

The ICT technology eliminates theworking clearance between plunger

and barrel at the barrel top. The fourbifurcated beams at the barrel top

center the plunger inthe barrel resulting inthe barrel centerlineand plunger centerlinecrossing at the barreltop. The plunger seatangle in the barrel isdetermined by theretained length and theworking clearance atthe retained length.

Tan q = c/b center line crosses at top of the barrelTan q = .0008/.235 b = retained length - .235

q = .195° c = working clearance - .0008

Tan .195 = e / a where e = pointing accuracye = Tan .195(.330)a = extended length of plunger - .330e = .0011"