Aml catalogue 13

Catalogue

Arun Microelectronics LimitedArun Microelectronics LimitedArun Microelectronics Limited

Vacuum Mechatronics

www.arunmicro.com

Arun Microelectronics Ltd

www.arunmicro.com

TSP2 Titanium Sublimation Pump Power Supply

Features

Sublimation pump controller

Sublimation current settable over the range 30 to 55A in increments of 0.1A

Self-timed delay between getter renewal adjustable from 1 minute to 9.9 hours

Suitable for a wide range of cartridges with up to 4 filaments, 85% Ti, 15% Mo filaments from 1.8 to 2.1mm diameter

Sublimation inhibit / trigger function by external switch or relay

Filaments are warmed and cooled gently to avoid thermal shocks. The sublimation current containsminimal harmonics to reduce the risk of early filament failure due to magnetostrictive stress ormechanical resonance

Pump current is accurately regulated in order to automatically compensate for mains variations and pump cable warming

Filaments may be run for degassing at currents between 5 and 25A to prevent overloading the ion pump. Filaments can be kept warm at the end of a system bake

Indicates open-circuit filament, shorted cable / filament, inhibit and overtemperature

Thermal overload protection

No in-service adjustment is required

2U (88mm) high full-width, steel cased instrument for easy rack-mounting

The TSP2 titanium sublimation pump power supply will controll most pump cartridges withup to 4 filaments. It regulates the quantity of material sublimated from the filaments, compensating for changing conditions and eliminating the need for operator attendance or adjustment.

Arun Microelectronics Ltd.

www.arunmicro.com

10 to 40°C for rated performance. Operation up to 50°C is possible at longer sublimation intervals

i.e. below 10-6 mbarOperating Temperature

Supply Voltage

Power Consumption

Output Current

220 / 240V (Option H) OR 100 / 110V (Option L), 50Hz or 60Hz, to order

SPECIFICATIONS:

SPECIFICATIONS:

Less than 20 watts when idling, less than 700 watts when sublimating at 55A with a maximum-length cable.

Regulated at 30 to 55A RMS x 0.1A in sublimation, 5 to 25A RMS x 5A in degass.

The output voltage is determined by the cable and cartridge resistance. Maximum output voltage is 9.5V RMS at 45AOutput Voltage

Sublimation period 0.1 to 3 minutes x 0.1 min.. Delay interval 1 to 59 minutes, 1 to 9.9 hours.

Degas time 1 to 99 minutes. All timing is derived from mains supply frequency.Timing

100% at 300w output power and less than 30°C ambient temperature.Output Duty Cycle

Dimensions

Weight

2U high (88mm), full width (483mm) x 366mm deep.

11kg

Order Code

Accessories

TSP2-H Ti. Sublimation pump power supply. 220/240V

Ti. Sublimation pump power supply. 100/110V

6 metre non-bakeable pump lead

6 metre pump lead with 1 metre 200°C

bakeable section

TSP2-L

TSP2L6

TSP2BL6

Fitzalan Road

Arundel

West Sussex BN18 9JS

England.

Tel: +44 (0)1903 884141

Fax: +44 (0)1903 884119

Email: [email protected]

AML pursues a policy of continuous product improvement and reserves the right to make detail changes to specifications without consultation. Unless otherwise stated all specifications are typical and at 25º Celsius, after 1 hour operation. E and OE.

TSP2

Vacuum Gauges


Vacuum Mechatronics

www.arunmicro.com


www.arunmicro.com

NGC2D Process Controller

Features

UHV Dual Bayard-Alpert Ion Gauge Controller

Continuous measurement range: 1000 mBar to 3 x 10-11 mBar range.

Controls 2 Ion gauges (sequentially), 2 Pirani gauges and 1 Capacitance Manometer.

Bright green LED display shows bar-graph or numeric pressure, trend, diagnostics, etc.. Display in mBar, Torr or Pascal. Permanent bar-graph of Pirani pressures.

Simple, guided setup is re-entrant and can be password protected.

Reduced emission current. Instrument can advise optimum current or may be set manually. Variable Ion gauge sensitivity. Filament in use selectable from front panel

Automatic start of Ion gauge in pump-down and can be interlocked by Pirani or external signal.

Manual and automatic electron-bombardment degas programs.

Integral, variable sensitivity leak detector with audio output on Pirani 1 or Ion gauge.

4 power relays for process control (5A, 240V) flexibly assignable to gauges.

System bakeout program with control of temperature, time & over-pressure limit. Integral K-thermocouple amplifier.

Automatic control of titanium sublimation pump controller with optional countdown / cancellation of imminent firing.

RS-232C interface for data-logging and control

Recorder output 1.0 volt/decade.

1U high full-width, steel cased instrument for easy rack-mounting.

Operates from 100V to 240V, 50/60Hz supply.

The NGC2D is a high-accuracy Ion Gauge controller that offers integrated pressure measurement and process control; with a large, clear display, an intuitive user interface and serial communications.


www.arunmicro.com

Ionization Gauge

AML AIG1xG are recommended. Bayard-Alpert gauges from many other manufacturers are suitable without

adjustment other than sensitivityGauge Type

Range

Accuracy and

Repeatability

Gauge Supplies

From 1 x 10-3 to below 3 x 10-11 mB with a UHV gaugehead with tungsten filaments. The low limit is dependent on

gaugehead, cable construction and length and conditions of use. The upper limit is determined by the acceptable

life of the filament and may be extended by the use of thoria or yttria-coated iridium filaments.

SPECIFICATIONS:

SPECIFICATIONS:

Determined principally by the gaugehead: controller errors are much smaller. Emission at 0.5mA is recommended.

Electrometer logarithmic conformance <1% within any decade from 0.1 mA to 10 pA, <5% to 1 mA and <20% to

2 pA at 25ºC incoming air temperature. Slope temperature compensation <0.02% per degree Celsius. Differential

linearity of the 12- bit A to D converter is less than 0.1 LSB. Emission current initial accuracy <2%, stability <1%.

Grid: +200 volts in emission, +500 volts at £60 mA in degas.

Filament: +50 volt bias, 12 volts at ≤4.2 A (Tungsten) ≤2.6 A (Yttria) with filament power limited at > 30 watts.

Pirani Gauge

AML types PVU and PVB.

A constant-voltage bridge circuit reduces contamination at high pressures. AML Pirani gaugeheads may be

exchanged or extension leads may be connected without adjustments being necessary.

Gauge Type

Capacitance Manometer

Capacitance Manometers of any manufacture having a +10 volt full-scale output at 1, 10, 100 or 1000 mBar or Torr

and which are self-powered are suitable. Pressure indication can be in units different to the full-scale units defined

for the Capacitance Manometer.

Gauge Type

General Specifications

Scientific notation or bar-graph displays in mBar, Torr or PascalPressure Display

Operating Temperature

Supply Voltage

Power Consumption

5º to 35º Celsius for specified performance. Incoming air temperature is measured and displayed and operation

is inhibited at >40°C.

100 V to 240 V nominal at 48 to 65 Hz, without adjustment.

<20 watts idling, <75watts in emission.

Dimensions 1U high, full width x 270mm Deep

Order Code

SPECIFICATIONS:

Accessories

NGC2D Dual (Sequential) Ion Gauge Controller

UHV Ion Gauge. 2 x Tungsten filaments

UHV Ion Gauge. 2 x Thoria coated filaments

UHV Ion Gauge. 2 x Yttria coated filaments

3, 6 or 9 metre bakeable Ion gauge cable

Pirani Gauge. Non-bakeable with 3m cable

Pirani Gauge. Bakeable with 3m cable

Pirani 10 metre extension cable, non-bakeable

AIG17G

AIG18G

AIG19G

AIGL3 (6) or (9)

PVU3

PVB3

PVX10

Fitzalan Road

Arundel


England.

Tel: +44 (0)1903 884141

Fax: +44 (0)1903 884119



AIG Ionisation Gauge & Lead UHV Bayard-Alpert Ion Gaugeheads, leads & filaments

Arun Microelectronics Limited

www.arunmicro.com

AML AIG Issue K

The AML AIG nude ionization gauge is a high-sensitivity UHV Bayard-Alpert gauge covering the vacuum range of 1x10-3 to 3x10-11 mbar and is intended for electron-bombardment degas. It has an NW35CF flange with individual glass compression seals, closed-end grid and a choice of fila-ment materials.

Individual glass compression seal around each feedthrough pin are more economical and robust than ceramic, resulting in a less expensive and more rugged gaugehead, with the central collector pin inherently guarded against leakage currents by the grounded bulk of the flange. Replaceable twin Tungsten filaments are fitted as standard with Thoria or Yttria-coated Iridium as an option. The molybdenum grid has a closed-end, light, rigid structure, resulting in high sensitivity. The X-Ray-induced electron desorption current at the collector is minimised by geometry and screening. Connector pins are gold-plated, shrouded and polarized. Gold plating ensures that oxida-tion on the air-side cannot occur even after repeated bakeouts. Maximum bakeout temperature 250°C. Sensitivity 19 per millibar for nitrogen. X-Ray as-ymptote 3x10-11 millibar.

Emission Degas

Collector +0V +0V

Grid +200V +500V

Filament bias +50V +0V

Max. emission 10mA 10mA W,

60mA Ir

Recommended Operating Conditions

H2O 19 N2

O2 19 CO

H2 9 CO2

He 3 Ne

Ar 24 CH4

Sensitivity, S mbar-1

19

20

27

6

27

Divide S by 100 for Pa-1. Multiply S by 1.33 for Torr-1


www.arunmicro.com

AML AIG Issue K

AIG17G UHV Bayard-Alpert gauge. Twin tungsten fila-ments

AIG18G UHV Bayard-Alpert gauge. Twin thoria-coated iridium filaments

AIG19G UHV Bayard-Alpert gauge. Twin yttria-coated iridium filaments

AIGL3, (6), (9) 3, (6), (9) metre, screened, bakeable Ion Gauge Cable.

FIL17 Replacement filament assembly. Twin tungsten

Ordering Information:

FIL18 Replacement filament assembly. Twin thoria-coated iridium

FIL19 Replacement filament assembly Twin yttria –coated iridium

Arun Microelectronics Ltd. Fitzalan Road Arundel West Sussex BN18 9JS England.

Tel: +44 (0)1903 884141 Fax: +44 (0)1903 884119 Email: [email protected]


AIGL Gauge Lead. The AIGL is a 250°C-bakeable lead for use with AIG and similar ionisation gauges connected to AML controllers. They are available in 3, 6 and 9 metre versions or custom lengths to order. AML use gold-plated connectors ex-clusively: these are essential for reliable long-term measurement of the ion current after baking. The cable is rated for the worst-case operating conditions of 50 watt degas with a new tungsten filament during a 200°C bake. This product incorporates a fully screened and guarded collector with >1x1015 insulation. The con-nector housing is machined from PEEK and the cable clamp is anodized aluminium.

Filament Types. Filament power varies over the useful life of a filament, due to gradual erosion of bare tungsten or loss of the oxide coating. In general, Thoria-coated iridium filaments require about one quarter the power of tungsten at mid-life. Yt-tria has similar properties and runs less than 50°C hotter in normal emission. Yttria also has better adhesion and consequently longer life. Oxide-coated filaments absorb water in storage and may require more power initially to evaporate it.

The filament power supply must be capable of providing high currents to develop adequate power in the low resis-tance of a cold filament and sufficient voltage to compensate for drops in a long, hot cable. A power-limited supply of 40 watts capable of providing up to 12 volts and up to 4 amps will drive any AIG17G gauge operating under any conditions, (including degassing during bakeout at 250°C) with an AIGL9 lead. AML BA gauge controllers exceed these requirements and include comprehensive filament protection features.

Replacement Filaments Replacement filament assemblies are available in tungsten, thoria and Yttria-coated iridium. The assembly is held by Allen set screws in socket receptacles and a key and replacement screws are provided.

PVU3 & PVB3 Pirani Gaugeheads Pirani Gaugeheads for use with AML Ion Gauge Controllers


www.arunmicro.com

AML PVU Issue D

Pirani gauges detect the cooling effect of residual gas molecules on a heated filament. The rate of heat transfer to the gas is related to pressure and causes a change in the electrical resistance of the filament or the amount of power required to maintain it at constant temperature. The filament is normally connected in a bridge circuit.

PVU3 is a low-cost non-bakeable gaugehead with an integral 3-metre lead and connector. The feedthroughs use matched glass-to-metal seals which have better life and leak performance than the epoxy or compression seals used on other low-cost Pirani gaugeheads. The standard flange is NW16KF.

PVB3 is a UHV-compatible stainless-steel Pirani gauge with an integral 3-metre lead and connector which can be baked at 200ºC. The standard flange is NW16CF.

PVX10 is a 10 metre extension cable for use with PVU or PVB. These cables extend the Kelvin sensing of AML controllers, so that the extension does not affect the calibration.

AML Pirani gaugeheads are intended for use in constant-voltage bridge circuits, which reduces the filament temperature and the rate of filament corrosion or contamination at high pressures.

Range: 200 mbar to 1 x 10-3 millibars.

May be interchanged between any AML NGC / PGC series or equivalent controllers without re-calibration. Extension cables do not affect the calibration.

Supplied calibrated for vertical installation in dry nitrogen. Internal calibration adjustments enable them to be used with other orientations and gases.

Materials exposed to the vacuum are stainless steel, nickel-cobalt-iron, glass and tungsten.


www.arunmicro.com

AML PVU Issue D

Ordering Information: PVU3 Pirani Gauge, non-bakeable, 3m lead. NW16KF

PVB3 Pirani Gauge, bakeable, 3m lead. NW16CF

PVX10 Pirani extension lead, non bakeable, 10 metres

Arun Microelectronics Ltd. Fitzalan Road ArundelWest Sussex BN18 9JP England.

Tel: +44 (0)1903 884141 Fax: +44 (0)1903 884119 Email: [email protected]


Gauges are supplied calibrated for dry nitrogen. Calibration instructions are supplied with all gauges. AML Pirani gauges are intended for use with AML Pressure gauge controllers and 1U-high controllers manufactured by AML for other vendors. Such controllers may be identified by the AML copyright marks on the printed circuit boards.

PVU2

3000

PVB2

3000

UHV Stepper Motors


Vacuum Mechatronics

www.arunmicro.com


• 1.8° Step angle• Suitable for use below 1 x 10-10 mBar• Bakeable to 200°C• Embedded K type thermocouple• Operational range -65°C to +175°C• Custom options available

Model Holding Torque

mNm

Detent Torque

mNm

Rotor Inertia

gcm2

Max.Axial Force

kgf

Max. Radial

Force (1)

kgf

Mass

g

Current Per Phase

A

Phase Resistance

at 20°C

Phase In-ductance

mH

D35.1 70 8 10 9 15 190 1.0 4.7 3.8

D42.1 180 8 35 9 15 350 1.0 5.3 6.6

D42.2 360 14 68 9 15 470 1.0 6.8 10.5

D42.3 450 20 102 9 15 610 1.0 8.5 19.5

D57.1 800 30 300 20 60 700 1.0 10.5 27.0

Operating temperature -65°C to +175°CBakeout temperature 200°CStep angle 1.8°Step angle tolerance 5%Lead length 1.5m (1) Refer to application note 27 for details

AML stepper motors are speci cally designed for use in UHV environments making them ideally suited for low speed precision in-vacuum manipulation without the use of particle generating motion feed-throughs. The consid-erable reduction in mechanical complexity, absence of metal to metal sliding surfaces and low outgassing charac-teristics make these motors especially suitable for sensitive handling applications

The model D motors are two phase hybrid stepper motors, available in a range of standard sizes and torque rat-ings. Standard motors provide 200 full steps per revolution and are suitable for use between -65°C to +175°C. Extended low temperature range (-196°C) versions, radiation hard versions (1 x 107 Gy), shaft modi cations and hybrid bearings are all available options.

All motors are designed, cleaned and hand assembled to UHV standards in an ISO Class 7 cleanroom.

Fourth Generation Hybrid UHV Stepper Motors

Technical Data

www.arunmicro.com

Ultra High Vacuum Stepper Motors

Version 1.7

Speed vs torque characteristics

The performance shown on these graphs was obtained using an SMD210 drive operating with standard settings for step division.

SMD210 is a switch-mode, bipolar, current-regulating drive with a nominal source of 67volts, optimised for use with vacuum motors. At low speed where step division is active the RSS (root sum of squares) of phase current is set to the nominal current. Over most of the speed range the drive operates in wave mode with nominal set current in only one energised phase.

Different drives will produce different speed / torque curves. Drives capable of producing a total phase current of more than 1A RSS may damage the insulation. Drives with signi cantly lower source voltages may result in poor high speed performance. Use of the embedded thermocouple is essential for motor protection.

3 30 300 3000

200

250

300

350

400

450

500

Speed (rpm)

orqu

e (m

Nm

)

D42.2

1.0A

0.8A

0.6A

0

50

100

150

200

10 100 1000 10000

To

Step Frequency (Hz)

SMD210 Drive, nominal source of 67 Volts.

0.4A

3 30 300 3000

100

150

200

250

Speed (rpm)

orqu

e (m

Nm

)

D42.1

1.0A

0.8A

0.6A

0

50

100

10 100 1000 10000

To

Step Frequency (Hz)


0.4A

100

150

orqu

e (m

Nm)

D35.1

1.0A

0.8A

0.6A

0

50

10 100 1000 10000

To

Step Frequency (Hz)


0.4A

3 30 300 3000

250300350400450500550600650700750800850900

Speed (rpm)

Torq

ue (m

Nm

)

D57.1

1.0A

0.8A

0.6A

0.4A

050

100150200250300

10 100 1000 10000

T

Step Frequency (Hz)


3 30 300 3000

200

250

300

350

400

450

500

Speed (rpm)

orqu

e (m

Nm)

D42.3

1.0A

0.8A

0.6A

0.4A

0

50

100

150

200

10 100 1000 10000

To

Step Frequency (Hz)


www.arunmicro.com

Dimensions

D35.1

Leads terminated with 1.5mm Crimp socketsITT Cannon P/N 192990-0090

6.35

1.6

6.34

55±1 20

38.1338.07

5.4

47

56

56

47

1.35mLead length

5.2 X 4Mounting Holes

8-off Ø3.3 Pumping portson 44.0 PCD. Both Ends.

31

42

42

31

1.35mLead length

8 x Ø3.2 Pumpingports on 31.0 PCD.Both ends

Motor Length LD42.1 35D42.2 49D42.3 61

2.0

L

21.9

123.0

22.0

5.004.98

M3 thread x 8.5

Leads terminated with1.5mm crimp sockets

ITT Cannon P/N 192990-0090

D57.1

D42.X

www.arunmicro.com

4 x Ø3.2 Pumpingports on 26.0 PCD.Both ends.

26 35

26

1.5mLead length

35

Leads terminated with1.5mm crimp sockets

ITT Cannon P/N 192990-0090

27±1 20

5.004.98

2.0

22.021.9

M3 thread x 6.5

Fitzalan RoadArundelWest SussexBN18 9JSTel: +44 (0)1903 884141Fax: +44 (0)1903 884119email: [email protected]

Ordering information

Order Code

D35.1 70mNm UHV Stepper Motor





Related products

SMD210 Stepper motor drive

MLF18F 18-way electrical feedthrough

MLF18NBL 3-metre lead, SMD210 to MLF18F

www.arunmicro.com

Bearings:-Standard motors are tted with open stainless steel bearings lubricated with NyeTorr® 6300 UHV grease.Option ‘H’ motors have hybrid bearings with silicon nitride ceramic balls, dry lubricated with molybdenum disul de.

Options:-H. Hybrid ceramic bearingsR. Radiation hardened to 1 x 107 GyX. Shaft modi cation. Please provide a sketch of your requirementC. Cryogenic. Extended operating temperature range. -196°C to +175°C

Order code format

D42.1 R

Order Code

Option

AML pursues a policy of continuous improvement and reserves the right to make detail changes to speci cations without consultation. E and OE.


www.arunmicro.com

SMD210 Stepper Motor Drive

Features

Dual sequential stepper motor controller

• Drives 2 UHV stepper motors sequentially.

• Advanced low-power drive techniques for minimum motor temperature rise and outgassing and maximum operating time.

• Phase currents can be set from 0.1 to 1A in increments of 0.1A.

• Holding torque can be controlled independently of dynamic torque under program control, to reduce power.

• Full, half, ÷4, ÷8 step drive modes with automatic transition at user selectable speeds. (Stops on full step positions only. Micro-stepping used for control of resonance and smoother step transition.)

• Thermocouple amplifiers (type K) for motor temperature indication, protection and control of motor bakeout.

• RS232C interface for host computer control. Drive programs can be developed and run from the computer console (Remote Program Control) or downloaded for stand-alone operation (Internal Program Control).

• Motors may be operated manually with the front panel 'STEP' switches or with a joystick. Single-step or multiple-step operation with smooth acceleration to the selected speed.

• 3 user inputs for interaction with program execution, in addition to two "End of travel" inputs for each motor.

• 3 user outputs for switching under program control.

• Simple control language has many powerful commands which allow control of all aspects of motion or position. Conditional operation, loops and jumps are possible.

• 1U high full-width, steel-cased instrument for easy rack-mounting.

• Operates from 100 to 240V, 50/60 Hz supply.

The SMD210 Vacuum-Compatible Stepper Motor Drive is designed to match AML motors. Two motors may be driven sequentially under host computer control or by an internally stored program. Manual operation is also available from the front panel switches or a hand-held joystick.


www.arunmicro.com

Command Summary

Ax Set user output x

Bx Select motor x

b Bakeout selected motor. (175°C)

Cx Clear user output x

Dx Delay x milliseconds, where x is 1 to 65535

E Start execution of a resident program

F Status request. (Busy, ready or error condition)

fx Preset position counter to x. (Sets a reference location at x=0)

G+/-x Go to a defined location x steps from a reference location

g+/- Rotate at preset speed indefinitely in the specified direction

H+/- Go to a location 8 steps inside the specified (EOT+ or EOT-) limit switch

hx,y Set the power reduction parameters (time and phase current after hold time)

In Initialise user output or position counter, as defined by n

J,j Jump to another part of the program

K Abort program execution

Ln Loop through a sequence n times, where n is 1 to 255

M Set the step rates for automatic ministep mode transition

P Enter or exit the programming mode of operation

Q Read the program resident in memory back via RS232C

Tx Define the current slew speed in steps per second, where x is between 10 and the maximum rate

defined by the x command (<6000)

Ux Until. Continue executing the resident program until user input x is “low”

Vx Status request. (Position, user inputs, temperature, software version, dynamic parameters)

Wp Wait for user input p to go “low” before executing the next instruction

Xx,y,z Define the acceleration / retardation parameters, where x is the start speed, y is the maximum

slew speed and z is the number of steps in the acceleration or retardation ramp

Z Reduce speed to zero with the defined retardation

+/-x Rotate x steps in the defined direction, where x is between 1 and 10E+6

SPECIFICATIONS:

Order Code

SPECIFICATIONS:

Related products

SMD210 Dual UHV-Compatible Stepper Motor Drive

UHV Compatible Stepper Motors

18-way Feedthrough (CF70)

Lead. SMD210 to MLF18F

C14.1, C17.1, C17.2

MLF18F

MLF18NBL

Fitzalan Road

Arundel


England.

Tel: +44 (0)1903 884141

Fax: +44 (0)1903 884119


AML pursues a policy of continuous product improvement and reserves the right to make detail changes to specifications without consultation. E and OE.

The above is given for information purposes only and is not intended to be a rigorous specification for programming purposes

SMDJOY SMD210 Joystick

Switch-mode current-regulating power stage with a nominal source of 67volts, for bipolar control of 2-phase vacuum stepper motors.

ARUN MICROELECTRONICS LTD. AML DATA SHEET: MLF Issue G

AML produce a range of wiring accessories to complement their UHV compatible Stepper motors. Thesecomponents make installation of motors and other electrical items in vacuum much easier.

MLF18VCF is a 18-way electrical female connector for use in UHV and is bakeable to 250 C. It mates with theMLF18F feedthrough and the MLF18VCM male connector. The insulated body is PEEK, which has exceptionaloutgassing performance. All internal spaces are well-ventilated. The gold-plated, barbed crimp-contacts are attachedto wires before insertion into the body and removed with a standard pin extraction tool, if required. Individual contactscan be inserted or removed without disturbing others. All AML motors are supplied with this type of crimp-contacts.

MLF18F 18-way feedthrough on a NW35CF (70mm OD) flange which mates with the MLF18VCF UHV connector,MLF18L lead or MLF18AC air-side connector. It has individual glass compression seals which are much more robustthan ceramic seals and is bakeable to 250 C. The 1.5mm diameter pins are gold-plated. For non-motor applicationsobserve the maximum ratings of 200V, 5A maximum per pin and 15A maximum per feedthrough.

MLF18NBL is a 3 metre non-bakeable lead for use with AML stepper motor drives and up to 3 motors installed inone vacuum chamber. It mates with the MLF18F feedthrough.

MLF18AC is the bakeable air side connector which mates with the MLF18F feedthrough. Use this for non-motorapplications or for connecting to other manufacturer’s drives.

MLF18VCM is the male counterpart of MLF18VCF. It is useful forextension cables or on de-mountable sub assemblies. This item may beordered pre-wired to one, two or three vacuum stepper motors.

This document and the designs depicted are the copyright of Arun Microelectronics Ltd. Specifications are subject to change, confirm before ordering. E & OEAML acknowledges the rights of the owners of all trademarks and registered names.

MLF18VCF

MLF18VCM

CONNECTORS, LEADS, FEEDTHROUGHS AND WIRING ACCESSORIESFOR UHV STEPPER MOTORS AND OTHER ELECTRICAL VACUUM DEVICES

MLF18VCF MLF18F MLF18L

ARUN MICROELECTRONICS LTD. AML DATA SHEET: MLF Issue G

PWB is a set of 4 PEEK wiring bushesand M3 x 10mm vented screws. Thefour phase wires and thermocouplefrom a single motor are a light fit in thehole in the bush. Use one in situationswhere a 'P' clip would be used in air. The wiring hole may be reamed outwith hand tools for other wiringapplications. Bakeable to 250 C.

Arun Microelectronics Ltd.Fitzalan Road, Arundel,

West Sussex BN18 9JP, England.Tel: 01903 884141 Fax: 01903 884119

International Tel: +44 1903 884141www.arunmicro.com

Mechanisms


Vacuum Mechatronics

www.arunmicro.com


Ultra High Vacuum Translation Stage

• Resolution 5 m or 1 m per full step• Suitable for use below 1 x 10-10 mBar• Bakeable to 200°C• Directly stackable for XYZ• Gamma radiation hard to 1x107 Gy

Speci cation Unit LTVL LTVH

Travel mm 50 / 100 / 150 / 200 / 250 50 / 100 / 150 / 200 / 250

Resolution in full step m 5 1

Max. Speed mm/s 15 5

Repeatability m 1 0.2

Load Capacity (Horizontal) kg 20 20

Backlash m Negligible Negligible

Roll, Pitch & Yaw rad <25 <25

Roll, Pitch & Yaw Compliance rad/Nm 33 33

Straightness of Travel m <1.3 m / 100mm <1.3 m / 100mm

Stepper Motor D35.1 D35.1

Vacuum mBar 1 x 10-10 1 x 10-10

Max. Temperature °C 200 200

MTBF (5kg load and 30% duty cycle) hrs 15,000 10,000

AML ultra high vacuum compatible linear translation stages provide long travel with minimum height for loads of up to several kilograms They have widely spaced ‘V’ roller guides and are useful in simpler compound mechanisms where torsional loads are small. They are manufactured with UHV compatible material and construction methods and utilize AML UHV stepper motors.

Smooth motion is provided by a diamond corrected lead screw and a matched, precision lapped nut to ensure good positional stability and incorporate a preloaded leadscrew nut to eliminate backlash.

LTV UHV Translation Stages

Technical Data

www.arunmicro.comV1.1

Fitzalan RoadArundelWest SussexBN18 9JS

Tel: +44 (0)1903 884141Fax: +44 (0)1903 884119email: [email protected]

Dimensions


Order Code

LTVLxxx Translation stage, 5 m (xxx = travel in mm)

LTVHxxx Translation stage, 1 m (xxx = travel in mm)

Related products




www.arunmicro.com


AML pursues a policy of continuous improvement and reserves the right to make detail changes to speci cations without con-sultation. E and OE.

LTVL

LTVH


Ultra High Vacuum Rotation Stage

• Resolution from 0.036° to 0.003° per full step

• Suitable for use below 1 x 10-10 mBar• Bakeable to 200°C• Directly stackable to AML linear stages• Open construction

Model CRS10K CRS20K CRS30K CRS60K CRS90K CRS120K

Rotation range 360°

Resolution in full steps 0.036° 0.018° 0.012° 0.006° 0.004° 0.003°

Steps per revolution 10,000 20,000 30,000 60,000 90,000 120,000

Maximum loaded speed 1kHz10sec/rev

1kHz20sec/rev

1kHz30sec/rev

2kHz30sec/rev

2kHz45sec/rev

2kHz60sec/rev

Load capacity Vertical 1kg

Load capacity Horizontal 10kg

Backlash (Unloaded) Less than resolution

Vacuum 1 x 10-10

Max.Temperature 200°C

Motor D35.1

Weight, including motor 640g 710g 710g 940g 940g 940g

AML ultra high vacuum compatible rotation stages are intended for intermittent rotation of balanced loads or as a precision gearbox. They are manufactured with UHV compatible material and construction methods and utilize AML D35.1 UHV stepper motors. The CRS10K/20K/30K can be mounted directly on AML LTV translation stages or stacked on another CRS without additional hardware. Standard xing - hole patterns are provided on the side “B”, base “A” and rotating table “C”

CRS UHV Rotation Stages

Technical Data

www.arunmicro.comV7.0

As standard CRS rotational stages are supplied lubricated with Nyetorr® 6300 low-vapour pressure (6 x 10-12 mbar) grease. Dry lubrication with molybdenum disul de is available as an alternative option but this will reduce the expected life of the worm wheel to <500 hours of motion.

Fitzalan RoadArundelWest SussexBN18 9JS

Tel: +44 (0)1903 884141Fax: +44 (0)1903 884119email: [email protected]

Dimensions


Order Code

CRSxxK Rotation stage

Related products




LTVxxL Translation stage, 1 m (xxx = travel in mm)

www.arunmicro.com


AML pursues a policy of continuous improvement and reserves the right to make detail changes to speci cations without con-sultation. E and OE.

CRS10K CRS20K CRS30K

CRS60K CRS90K CRS120K

Application Notes


Vacuum Mechatronics

www.arunmicro.com

Page | 1

ARUN MICROELECTRONICS Ltd. Application notes for Vacuum Compatible Stepper Motors V4.2

Page

1 Index 2 Operation of stepper motors in vacuum 2 The vacuum environment 2 Temperature rise 3 Outgassing 3 Baking vacuum systems containing motors 3 Corona discharges 3 Low-temperature operation 3 The magnetic environment 4 Adverse chemical environments 4 Care and maintenance 4 Bearing damage 4 Debris inside the motor 4 Overheating 5 Design of mechanisms for use with vacuum compatible stepper motors

5 Rotation (position control) 5 Rotation (speed control) 5 Translation 6 Linear guides 6 Reduction gearing 6 Bearings 7 Resonances

7 The effect of load inertia, friction and drive characteristics 7 Control of resonance

Page | 2

OPERATION OF STEPPER MOTORS IN VACUUM It is assumed that the reader is familiar with the production of UHV and the handling of UHV components. This note does not attempt to describe the theory of operation of hybrid stepper motors. The vacuum environment. The successful application of vacuum stepper motors requires an appreciation of their thermal as well as their mechanical properties. Compared to motors operated in air the available cooling means for motors in vacuum are much less effective, and until development of the B-series motors continuous operation was difficult to achieve. Operation at low temperature improves the outgassing performance of motors. For this reason minimum running times and motor currents should always be pursued. Selection of the largest motor possible for the application will result in longer running times, lower motor temperature and lowest outgassing. This is because of the larger mass and higher efficiency of larger motors. Stepping motors only perform useful work while the load is moving. This may only be for a period of a few milliseconds for each step. Users of the SMD210 drive will find the 'h' command may be used to reduce the phase currents after each step and produce a holding torque which is intermediate between the pullout torque and the detent torque, with a consequential reduction of power. At low speeds the torque of a motor is roughly proportional to the phase current but the motor power is proportional to the square of the current. Where the load inertia dominates the dynamics of the system it is often possible to reduce the phase current, provided the motor is accelerated more slowly. Many applications that appear to require continuous running, for example substrate rotation for ensuring uniformity of deposition or implantation, can be equally well performed by intermittent short periods of stepping at low duty cycle. This will reduce the temperature rise. Where intermittent motion is required design mechanisms with balanced loads whenever possible, to eliminate the torque required to hold them stationary. Alternatively, increase the static friction in the system or add reduction gearing so that the motor detent torque will hold position without power. Maximum efficiency of AML motors is achieved between 500Hz and 1 kHz full-step rate using the SMD210 drive. Temperature rise. The maximum recommended running temperature of AML motors is 175 Celsius, as measured by the embedded type K thermocouple. Take care to ensure that any measuring equipment connected to the thermocouple is not affected by the high electrical noise environment within the motor under drive Irreversible deterioration of the winding insulation will begin to occur above 230 and the motor may subsequently produce larger amounts of gas, even at lower temperatures. The temperature rise at step frequencies above 1kHz will progressively reduce with a typical drive, which will be unable to establish the set phase current during the step period. Continuous running with low outgassing can readily be achieved at medium phase currents. Run times at higher currents can be increased by additional heatsinking at the flanged end of the motor. The predicted temperature rise will be increased if radiation from other sources within the vacuum chamber is incident on the motor. Screening may be necessary.

Page | 3

Outgassing.Newly-installed motors will outgas, mainly due to water-vapour retention in polyimide. As this material is microporous the water is released rapidly and the rate will subside after a few hours. The rate may be accelerated by running the motor to self-heat it.

Baking vacuum systems containing motors. Vacuum-baking of AML Motors at up to 200 Celsius is permissible, and a 24-hour bake at this temperature will normally reduce the outgassing to its minimum, provided there is pumping capacity of 100 litres at the site of the motor. Outgassing test-chambers with limited conductance between measuring points will require baking for several days or weeks to fully outgas a motor. Motors are typically operated at some distance from the chamber walls, which is where heat is applied and the bakeout temperature is most often controlled. If the thermal conductance from the chamber to the motor is low the motor may not reach the desired temperature. Fortunately, the motor thermocouple allows its temperature to be monitored and controlled to ensure adequate degassing. If the temperature indicated by the motor thermocouple during bakeout is not high enough when the bakeout period is well advanced it may be increased to 175 by applying drive power. The preferred method of doing this is by using the SMD210 "b" command. This energises both phases and keeps the motor stationary in a half-step position. Power is supplied until the indicated temperature reaches 175 C and is then removed. Power will be re-applied if the temperature falls to 165 C during execution of the "b" command. Keeping the motor hot by this means while the rest of the vacuum system cools is recommended, as this will prevent condensation on the motor. This is important, since the motor is likely to run hotter than the chamber in most applications. Where internal infra-red heaters are used for bakeout it is advisable to shield the motor from direct radiation and to achieve the desired temperature during bakeout by running the motor.

Corona discharges Switchmode stepper motor drives have source voltages of up to 100 volts which may be sufficient to produce a discharge at high pressure. This is most likely to occur on adjacent pins of the feedthrough but un-insulated joins in the motor wiring or small holes in the insulation are other possible sites. The drive may not be protected against this type of discharge and may be damaged. The insulation material near a persistent discharge will progressively deteriorate. Low-temperature operation Standard AML motors are suitable for operation at -65°C. Low temperature versions are available suitable for use at -196°C. The leads of the motor will be very brittle at low temperatures and should not be allowed to flex. The normal mechanical and electrical properties of all materials are recovered on return to room temperature. Because the resistance of the windings at low temperatures is small the efficiency of the motor is much greater than at normal temperatures. A resistance of a few ohms should be connected in series with each winding, in order to present a normal load to the SMD210. Drives which are voltage sources and which rely solely on the resistance of the motor to define the phase current should not be used for low-temperature applications. The magnetic environment Motors should not be operated in fields of greater than 50 millitesla (500 gauss), as this will affect the performance while the field is present. Fields significantly greater than this may cause partial de-magnetisation of the rotor, reducing the torque. Demagnetised motors can be restored by AML. The leakage field of a motor is of the order of 1 microtesla (10 milligauss) at 10 cm from the centre of the motor in an axial direction and is present when the motor is not powered. Under drive an alternating component is added at the step frequency and its harmonics up to a few kHz. The field is easy to screen with Mumetal or similar high-permeability foil at the sides of the motor, but is more difficult around the projection of the shaft. Early consideration of the interaction of stray fields on nearby equipment is recommended.

Page | 4

Adverse chemical environments AML stepper motors are specified for use in clean UHV although they are often used in deposition systems. Where it is possible to screen the motor from the line of sight of the deposition source this should be done. Where chemical vapours are being used careful consideration of the effect on the motor materials will be required. AML are generally unable to answer on the effect of exotic chemicals but may be able to provide sample materials for test. The materials used, in approximate descending order of exposed surface area are:

Polyimide

Diamond-like carbon Stainless steel 440, 304, 316, 303 Silicon steel Samarium Cobalt Poly ether ether ketone (PEEK) 450G Alumina ceramic Silicon nitride ceramic

Silver Fluorinated ethylene polymer (FEP). (Not used on radiation-hard motors.) Copper Chromel/Alumel (Chromel and Alumel are registered trade marks of Hoskins Manufacturing Co..)

Care and Maintenance of VCSMs. VCSMs are inherently robust and have only a single moving component consisting of a simple rotor assembly, supported on ball bearings. The maximum speed of this type of motor is very low so that the bearings have an extremely long predicted service life in vacuum. There are no commutators, slip rings or any other components having sliding contact between surfaces. Given reasonable care in handling there will be no need for any maintenance. Stepper motors should not be disassembled as this partially demagnetises the permanent magnet in the rotor and permanently reduces the torque. Vacuum motors must be de-magnetised before dis-assembly and re-magnetised and cleaned after repair. For these reasons motors with faults will need to be returned to AML for repair. The notes below offer guidance on the avoidance of the most common problems and diagnostic advice. Debris inside the motor. Foreign material can enter the motor via the pumping holes and gaps in the bearings. Particles of magnetic materials are particularly likely to be attracted through the pumping holes and they eventually migrate into the gap between the rotor and stator. They usually cause the rotor to stick at one or more points per revolution and can often only be felt when rotating in a specific direction. Fortunately, the larger motors have enough torque to grind them into a dust. Overheating Motors which have been heated to 230 C will produce a much greater gas load thereafter, although their electromechanical performance may not be affected. Rewinding is practical provided the windings are not discoloured and the vacuum performance will be subsequently improved. If the windings are darker than a golden-brown colour the motor will not be repairable. In extreme cases the insulating material will ablate and deposit itself as a yellow powder inside the motor case and on any cool surfaces in line with the pumping holes. Motors can overheat extremely quickly in vacuum. This is very unlikely to happen with a properly-connected SMD210 drive. Never use a drive capable of providing more than 1 amp of phase current and ensure that the drive current is removed as soon as the indicated temperature exceeds 175 C.

Page | 5

DESIGN OF MECHANISMS FOR USE WITH VACUUM COMPATIBLE STEPPER MOTORS (VCSMs) The following section is an introduction to this topic and is intended to indicate the major mechanical and vacuum considerations for various types of mechanisms. A working knowledge of mechanics and vacuum construction techniques is assumed. AML supply a range of standard mechanisms which can be customised and also design special mechanisms and components. Rotation ( Position Control ). The load inertia coupled to the motor shaft should ideally be small compared to the rotor inertia of the motor. Load inertia up to two or three times that of the motor can be driven, without significant difference to the maximum start speed and acceleration which is achieved by the unloaded motor. Load inertia of around ten times that of the motor can be driven with absolute synchronism, provided care is taken over specifying the ministep and acceleration parameters. Larger inertia loads should be driven through reduction gearing. Significant loads should have their centre of gravity on their axis of rotation, unless they are rotating in a horizontal plane. Angular resolution at the motor shaft is limited to a single step of 1.8 . The actual rest position within the step is determined mainly by the load friction and any torque imposed by the load on the motor at rest. If the rotor position is displaced from the nominal step position the restoring torque increases approximately in proportion to sin(100 x ) . The maximum torque at the half step position is either the detent torque or the holding torque, depending on whether the motor is powered at rest. If the static friction and any torque due to an unbalanced load are known, this allows the rest position error to be estimated using the above approximation. The friction within the motor bearings is very low, so that a completely unloaded D42.2 motor will normally settle within 0.2 of the desired position if brought suddenly to rest from full stepping at 300Hz. Angular resolution may be improved by reduction gearing: this is discussed below. Increasing angular resolution by step division is not recommended for vacuum applications, since the motor must be continually powered to maintain the ministep position. The absolute improvement which could be gained by this method is small because of the increased significance of the uncertainty in the rest position.

Rotation ( Speed Control ). In some applications the precise position of a rotating load is not important or can be deduced by other means but the speed of rotation may need to be controlled very precisely. Beam choppers and sample rotators for control of deposition uniformity are applications of this type. An increased load inertia may be desirable to smooth out the stepping action of the motor. Loads of up to about 1000 times the inertia of the motor can be controlled by using long acceleration ramps. Some steps may be lost during acceleration and retardation of such loads, but precise synchronism at constant stepping frequency is easily achieved and recognised. Significant rotating loads should be balanced, at least to the extent that the torque presented to the motor shaft is less than the detent torque of the motor. The motor torque requirement will then be dominated by that required to accelerate the load. Translation. Translation may be produced by a leadscrew and nut, wire-and-drum or rack-and-pinion mechanisms. The choice depends on the precision, length of travel, force and speed required.

Page | 6

Leadscrew-based translators are capable of exerting forces of kilograms with resolutions of a few microns per step. Accurate leadscrews are practical up to 300 mm long. With anti-backlash gearing between the motor and leadscrew, a resolution of one micron is practical. Anti-backlash nuts are not normally necessary for vertical motions. If a conventional nut is used with the leadscrew the load will be dominated by friction, especially if there is a reduction gear between the lead screw and the motor shaft which reduces the reflected load inertia. Because of the lubrication restrictions and the slow speeds of UHV mechanisms the static friction is usually much more significant than dynamic friction. The optimum material for nuts is phosphor bronze and for lead screws is stainless steel with a diamond-like coating (DLC). DLC has a very low coefficient of friction in vacuum. Burnishing or sputtering a layer of pure Molybdenum Disulphide on the leadscrew may be useful in reducing friction and wear. The typical coefficient of friction between these materials is 0.1 and typical efficiencies are 40% with ground trapezoidal threads. The gas load generated by frictional heating of the leadscrew is usually somewhat less than that of the motor. This may be reduced by changing to either a Molybdenum Disilicide or Tungsten Disilicide leadscrew coating. For short translators with resolutions of a few microns AML can supply motors with integral leadscrews formed on an extended motor shaft. This eliminates the need for a coupling arrangement and for the additional bearings which would be required to support a separate leadscrew. Recirculating ball nuts for vacuum use are available. These offer much higher efficiencies but at very high cost. They produce a very low gas load due to their low friction and can be used to exert forces of tens of kilograms. They can be loaded with selected balls to reduce backlash to an extremely low level. The form of the associated lead screw is special and longer lengths are available. The frictional losses in drum or rack drives are lower than in conventional leadscrew drives and considerations of inertia usually dominate. Rack and pinion drives are suitable for travel up to a few hundred millimetres and wire-and drum mechanisms may be made several metres long. The repeatability and backlash of all these alternative translation drives are much worse than with screw-driven schemes.

Linear guides. Low-cost translation mechanisms can use simple bushes running on ground stainless-steel rods. A variety of carbon-reinforced polymer materials, such as PEEK, are suitable for the bushes, although these are more expensive than phosphor bronze. 'V' groove rollers and tracks and crossed-roller guides are suitable for more accurate translators. The former have the advantage of being practical to 1 metre and have minimal overall length for a given travel. Crossed-roller slides are more rigid and can support larger loads, but at higher cost. Both types have preload adjustments. 'V' rollers have smaller load-bearing surfaces and only have a rolling contact at a single point and are consequently liable to greater wear if heavily loaded. Reduction Gearing. The inertia of loads coupled by reduction gearing is reduced at the motor in proportion to the square of the reduction ratio. Where reduction gearing is used for load matching, the spur gear meshing with the motor pinion will normally dominate the load inertia and it is important to keep its diameter small. Anti-backlash gears and standard pinions should be used in the gear train to damp any resonances in the mechanism. Gears for use in UHV should be designed for low friction without lubrication and with dissimilar materials in contact to avoid cold-welding. Nitrogen ion-implantation of the rolling surfaces or complete Titanium Nitride coating of gears are effective means of achieving this and other desirable properties in all-stainless-steel gear trains. Bearings. Bearings for use in UHV should be unshielded and have a stainless steel cage and race. The balls should be either stainless steel coated with some other material or solid ceramic. As an alternative, all-stainless bearings having a PTFE composite component in the race (which is designed to transfer to the balls) are also suitable.

Page | 7

RESONANCES The most common application problems with Stepper motors are concerned with resonances. Stepper motors are classic second-order systems and have one or more natural resonant frequencies. These are normally in the 50 - 100Hz region for unloaded motors. Operation at step rates around these frequencies will excite the resonances, resulting in very low output torques and erratic stepping. Another set of resonances can occur in the 1 - 2kHz region, but these do not normally present any practical problems. The effects of load inertia, friction and drive characteristics. The primary (lower) resonant frequency cannot be stated with any precision, since it is modified by the friction and inertia of the load, the temperature of the motor and by the characteristics of the drive. Coupling a load inertia reduces the resonant frequency and decreases the damping factor. Load friction increases damping. Because the drive circuits of the SMD210 produce a controlled phase current this produces heavy damping. Drives which are voltage sources and which rely on the motor winding and other resistance to define the current have a lower damping factor. The effect of changing the damping on the single step response of the motor is shown in the diagram. Control of Resonance. The simplest method of controlling resonances is to avoid operation of the motor close to the resonant frequencies. It is usually possible to start a motor at rates in excess of 300Hz if the load inertia is small, thereby completely avoiding the primary resonance. Resonances are not usually a problem when the motor speed is accelerating or retarding through the resonance frequency region. The SMD210 allows independent selection of the starting speed and the number of steps in an acceleration profile. If it is necessary to operate at slow speeds or with large load inertia the step division feature of the SMD210 (ministep) helps. It effectively increases the stepping rate by the step division factor and reduces the amplitude of the transients that excite the resonances. This is shown in the diagram below. Because both phases are energised in ministepping there are some other processes of interchange of energy between the windings which do not occur in the single step mode and these increase the damping factor. In particularly difficult cases modifying the step frequencies at which transitions of the step divisions (ministep modes) occur can be useful. Be careful not to specify step division at excessive frequency, as this reduces the available torque. The frequency of step division is the product of the step frequency and the number of ministeps in a full step. As a general guide, 500Hz is the maximum useful limit. A typical motor response to a single step and to a single step subdivided into eight ministeps is shown in the diagram.

ARUN MICROELECTRONICS Ltd.

APPLICATION NOTE No 11, Issue D, March 2004

C-SERIES MOTOR VACUUM PERFORMANCE

Some remarkable improvements in the outgassing performance of AML vacuum-compatible stepper motors have been achieved in the last year. Most of these have resulted from a reduction in the temperature rise of the windings, although the outgassing from most of the metal surfaces has also been reduced by new surface treatments.

Experimental determination.The motor was suspended in a 400 litre sec-1 (nominal) ion-pumped UHV system equipped with a Hiden (HAL1000) RGA and AML Bayard-Alpert ( AIG17 + PGC2) and Inverted Magnetron ( AMG10 + PGC4D ) ionisation gauges and controllers. The motor was driven by an AML SMD2 drive. The system was pumped down and baked at 200 C for 24 hours. During the period in which the system cooled close to ambient temperature the motor was run at 1 Amp phase current using the SMD2 'Bake' program. This program controls the motor winding temperature with a setpoint of 175 C, and a hysteresis of around 20 , using drive current to self-heat both windings. The motor was then switched off to allow the system to attain its base pressure of 4 x 10-10 millibar.

In order to ensure that the motor was adequately degassed the SMD2 'Bake' program was run again. After an initial rapid rise in temperature this produced a temperature oscillation with an initial period of about 40 seconds, with a synchronous oscillation in the system pressure as the drive power was switched on and off. The excursions in pressure and the steady pressure on which they were superposed reduced to a steady minimum over a few hours, showing that the motor was substantially outgassed.

The motor was then run continuously for long periods at various smaller phase currents, in order to allow its temperature to stabilise at a number of points in the range between 50 and 175 C. The total and partial pressures were then measured.

Results.The only significant outgassing products were Hydrogen (90%) and Carbon Monoxide (10%). All other peaks in the spectrum were below 1% of the Hydrogen peak height and were characteristic of the system and independent of the motor temperature.

The derived outgassing rates for the C17.1 motor with respect to temperature are shown in the graph opposite.

The outgassing rates of the three sizes of motors were found to be very similar, with a 2:1 spread. Since this variation is well within the measurement errors and the variation from unit-to-unit, the curve may be used for all types.

From the outgassing rate curve it can readily be seen that operation of a motor at the lowest possible temperature will be beneficial in reducing the gas load it produces. For example, operation at 100 C will produce about 10% of the gas compared to operation at 140 C. Selection of the largest possible motor for a given power requirement will result in the lowest temperature rise.

Estimating the gas load and pump capacity.

A simple application of the rate data will give a very conservative estimate of either the required pumping rate, S, or the ultimate pressure, Pu, for a given pump.

1. Select the minimum motor phase current which will provide the required motor torque and speed.

2. Use the winding temperature graph on the last page of this note to predict the approximate temperature rise.

3. Use the outgassing rate curve to estimate the gas load, Q.

4. Derive the result required from Q = S. Pu

Improving the vacuum performance.In practical situations the temperature rise is somewhat smaller than predicted, giving a substantially smaller gas load. An appreciation of the factors affecting temperature rise allows users to tailor their applications for minimum outgassing. The relative importance of these factors depends on the type of application: those which require continuous operation of the motor being the most challenging.

Since the curves of motor temperature were derived with minimal heatsinking, they are conservative in predicting temperature rise in real applications. It is very easy to reduce equilibrium temperatures of 100 C and over by 30 to 40 by relatively simple means, such as mounting the motor on a plate or mechanism. Additional heatsinking has little effect on the curves before sometens of minutes heating, because the transient thermal impedance of the motor is not reduced.

The temperature curves were obtained with both motor phases being driven with a steady direct current, which is only representative of low-frequency stepping. Since the motor windings are inductive, it takes a finite time to establish a current in them and this delay begins to become significant at stepping rates of a few hundred Hertz. The effect is that the average winding current is progressively less than the set current at increasing speeds. This means that a motor running at faster than a few hundred steps per second reaches a lower final temperature than predicted. Beyond about 2kHz the reduction is dramatic, however, the available torque is much reduced.

Wherever possible applications should be designed so that the load may be held in position by the detent torque of the motor, so that power may be removed between periods of motion.

The power output of the motor is proportional to the product of the output torque and the step frequency. At low step frequencies each step is taken in a few milliseconds, after which no useful work is done, although power continues to be dissipated. The effect of this is that the electromechanical efficiency of the motor increases with speed until other factors reduce it, reaching a peak between about 500Hz to 1kHz. Operation in this range of speeds will, therefore, minimise the temperature rise for a given power output. Where gearing is involved, as in most mechanisms, this is in any case the optimum range of speeds for mechanical reasons.

For slow speed applications the SMD2 drive allows the phase current to be reduced after each step. This increases the efficiency at low speeds.

For many applications motion is intermittent, with relatively short periods of motion and long periods of rest (low duty-cycle ). Provided the temperature rise during each cycle is small it is valid to multiply the phase current by the duty-cycle to estimate an effective phase current. If interpolation between the curves is required, it should be remembered that the heat dissipated in the motor is proportional to the square of the phase current.

C14.1 Motor

Arun Microelectronics Ltd APPLICATION NOTE No 28, Issue 2 , February 2011

Magnetic leakage fields of AML stepper motors.

AML stepper motors are hybrid types and contain an axially-magnetised permanent magnet in the rotor. D-series motors are magnetised with the north-seeking pole at the flanged end of the motor. A small proportion of the total magnetic flux leaks out of the motor, which behaves as a very weak bar magnet. The leakage fields of typical samples are shown below. These were measured inside a cylindrical magnetic shield with its axis at right angles to the horizontal component of the earth's magnetic field, which was 0.75μT at the test location. The screening became ineffective at displacements of 150mm along the motor axis.

D35.1 D42.1 D57.1 Flux density μT Flux density μT Flux density μT

Disp. mm On axis On side

Disp. mm On axis On side Disp. mm On axis On side

40 50 15 40 40 20 40 n/a 10060 16 5.5 60 13 8 60 90 4080 6 2.2 80 5 3 80 30 16

100 2.8 1.1 100 3 1.5 100 16 8120 1.8 0.6 120 2 0.8 120 11 4140 1.2 0.3 140 1.4 0.4 140 6 2

Under drive conditions the magnetic field is modulated by an alternating field at the stepping frequency. This is not usually as significant as the steady field, for a combination of reasons. The amplitude of the stepping-frequency field reduces with increasing step frequency and is only comparable to the steady field below a few hundred Hz. At low step rates it is normal (for mechanical reasons) to use ministepping, which produces a sinusoidal flux waveform. Above a few hundred Hz it is normal to use full-step drive, which attempts to produce a rectangular flux waveform. However, the filtering action of the winding inductance progressively reduces the amplitudes of all frequency-components of the field above a few hundred Hz so that the alternating component of the leakage field at stepping frequency can be considered sinusoidal for all practical purposes. Most modern stepper motor drives achieve current-regulation in the windings with a switching action, which also modulates the magnetic leakage field. For SMD210 the switching frequency is 22kHz. The amplitude of this is usually very small compared to the steady and step-frequency components of the field, typically less than 10%. In most situations the switching is disabled for the first few milliseconds after each step and is therefore not present at all above step rates of 500Hz. Stepping motors achieve their greatest electromechanical efficiency between 500Hz and 1kHz step rates and it is standard practice to design motorised vacuum mechanisms to slew at these rates, in order to minimise the total energy input and hence the outgassing. It is fortunate that this also reduces the alternating components of the leakage flux.

Vacuum motorised mechanisms should be designed to hold their rest position without the need for the motors to be powered. This is desirable for a number of reasons, including the reduction of outgassing. If the analysis or process within the vacuum system is only active when the mechanism is stationary then the alternating components of leakage fields need not be considered.

The axial fields of motors are about three times greater than the radial fields at a given displacement. This, and the presence of the shaft means that the fields can be screened more easily at the sides of the motors. Where possible, the optimum orientation for the motor is with the shaft at right angles to the line between the motor and the point where the field is to be minimised and at the maximum displacement. If there are several motors in the mechanism some field-cancellation can be achieved by mounting them in pairs, aligning their axes in opposing directions. Where motors are to be screened using Mumetal or other material it is more effective to place the screens much closer to the motors than to the volume where the field is to be minimised. Where significant torques and minimal leakage flux are required in the same installation it is better to use D35 or D42 motors and reduction gears than D57 motors.

END.

Arun Microelectronics Ltd APPLICATION NOTE No 27, Issue 2 , July 2010

Axial and Radial loads on AML stepper motor bearings.

AML stepper motors are fitted with two bearings, which support the rotor at each end of the housing. They are extremely reliable in clean vacuum situations and have useful service lives of decades with low imposed loading. The two principal causes of failure are both due to misuse: break-up of the ball cage due to ingress of contaminants or damage due to extreme shock loads such as are caused by dropping the motor on its shaft end.

Axial and radial loads imposed on the motor should be avoided where possible by the design of the mechanism to which the motor is applied. Loads comparable to the bearing ratings will shorten their lives in unpredictable ways. It will usually be more convenient to replace bearings in a mechanism than in a motor, which has to be de-magnetised, cleaned, re-magnetised and baked during any service.

Axial loads.

The bearing at the opposite end to the principal mounting face of the motor is preloaded against the motor end cap by a spring. The free travel of the spring is about 0.3mm and is fully exercised by a force of 2½kg against the shaft end. It is important to design linear mechanisms so that this free travel is not added to the backlash in the mechanism. This can be achieved by preload springs, gravity or by decoupling the motor from the load by gearing.

Linear mechanisms with leadscrews can exert considerable axial forces if they are stalled against rigid end stops. All AML mechanisms are designed with vernier stops, which stall the motor directly, avoiding this potential problem. If there is any possibility of a linear mechanism crashing into rigid obstructions it may be necessary to use torque- limiting to reduce the resulting force. If a linear mechanism stalls due to excessive friction no additional axial load is imposed on the leadscrew.

For all AML motors direct axial loads of greater than 10kg are not recommended.

Radial loads.

Radial loads on motors arise in two main ways. The first is a simple cantilever extension on the shaft, where the forces on the bearings can be easily calculated by reference to drawing Q47015, which is appended. Note that the radial forces on the bearings are magnified by the extension acting as a lever. The second arises in linear mechanisms where the leadscrew or other extension is directly coupled to the motor shaft and supported or constrained by a nut or bearing. Any misalignments will give rise to significant radial forces on the motor bearings.

For all AML motors direct radial loads of greater than 10kg are not recommended.

Vacuum Mechanisms from AML

Arun Microelectronics Ltd. (AML) design and manufacture automated precision mechanisms for use in UHV, using well-proven vacuum-compatible stepper motors.

AML motors have been manufactured and applied since 1986 and are a mature and accepted UHV technology. Thousands of motors are in regular use. AML have unrivalled experience in the application of VCSMs to mechanisms, with several hundred succesful designs completed. There are standard ranges of linear mechanisms and rotation stages, although most mechanisms supplied are customised to some extent.

Application areas.Stepper motor–based mechanisms should not be regarded merely as replacements for those based on other techniques, since they offer specific advantages and are suitable for applications not addressable by other means. The advantages of internally motorised mechanisms are that the number and range of motions, rigidity, accuracy, repeatability, speed, reliability and crosstalk between motions are much better than is possible

with motion feedthroughs. Where there are several axes, or if the range of linear motion exceeds a few centimetres, or if the sample is large or heavy then stepper motors offer price as well as performance advantages. The main application areas are in clean vacuum systems, where the magnetic leakage fields of motors (a few microtesla) are not significant. These include sample transfer and sample scanning for surface analysis, mass analysis, ellipsometry, radioisotope dating, MBE, electron channelling, Rutherford Backscattering, deposition uniformity control, beam chopping, cluster-processing and VUV/X-ray monochromators.

AML vacuum mechanisms are not economic in non-vacuum applications.

Position control.When driven correctly, stepper motors are inherently self-encoding digital devices. Provided the recommended speeds and accelerations are not exceeded then desired and actual positions remain exactly synchronised. There is no need for expensive encoders, other feedback devices or limit switches or the inconvenient wiring and feedthroughs that they need. A convenient reference location is provided for each axis so that any location on each axis can be achieved by execution of a single command by an SMD2 controller. Position information is maintained in the SMD2, even in the absence of power, and there is normally no need to re-establish the reference locations after an initial setup.

Speed Control. The speed of rotation of a stepping motor is precisely controlled by the frequency of its drive: there is no slip or other uncertainty and no feedback devices are necessary. Above a few hundred Hz the stepping action of an unloaded motor is smoothed by the low-pass filtering of the kinetic energy stored in its rotor. The use of step division at lower speeds smooths the motion further and increases the damping factor.

Vernier stops. Stepper motors may be stalled indefinitely without damage. AML mechanisms are designed so that they can be driven into their mechanical end-stops without affecting their performance in any way. The range of uncertainty in the position of an end-stop may be reduced by fitting a vernier stop. These are arranged so that a pin attached to the output plate of the mechanism moves into the plane of a radial arm attached to the motor shaft. The position at which this stalls the motor has a range of uncertainty of three steps, which can often be reduced to a single step. The repeatability of positions is usually more important than absolute position and this is typically less than a single step. Usually it will not be necessary to re-establish the end-stop position after installation and commissioning is complete. Vernier stops are inexpensive and effective.

Range of motion. A practical maximum length of travel for linear mechanisms using leadscrews is 300mm. For longer travels, belt or wire drives are appropriate, but these have lower resolution. For rotation mechanisms with position-control, the maximum range may be restricted to slightly more than 360°. This limitation is necessary to ensure that the wiring from any sample-connection, heating device or other motorised stage mounted on the rotation stage can be brought out. Most rotation stages in stacked multi-axis mechanisms will require much less than 360° range: it is important not to over-specify range of rotation as this increases cost.

1μm / step

1.8º / step

ResolutionResolutions of 1 micron or 1 millidegree per step are easily achieved. For linear mechanisms, specifying 4 micron resolution minimises the cost. For rotation stages the optimum resolution is determined by the available space and load-matching considerations. Specifying the coarsest resolution acceptable will reduce the cost but better-than-specified resolution may be offered because of loading. Because a stepping motor is a digital device, the motion resulting from a single step has a defined tolerance, usually about 5% of a single step at the shaft of an unloaded motor. The motion resulting from any number of steps still has an overall tolerance of a fraction of a single step. Step division is not a satisfactory way of increasing resolution.

RepeatabilityRepeatability of any position at constant temperature and approached in a consistent way is normally better than the resolution. Wherever possible, thermal expansion of the mechanism is equalised about the centre of travel. Thermal expansion of leadscrews of linear mechanisms due to self-heating may need to be considered where there is a very high duty-cycle motion. Thermally decoupling the motor from the leadscrew will reduce this effect by a large factor in low-resolution applications. AML will advise in specific cases.

Backlash.Most motorised mechanisms are supplied with active backlash-control means fitted. Backlash is usually negligible, compared to resolution. The orientation of all axes with respect to gravity is significant in controlling backlash. In some cases gravity alone may be used to control backlash, reducing complexity and mechanical loading, although in other cases it may present challenges. For example, rotation of loads whose center of gravity is offset from the axis may result in a reversal of static torque: such cases can usually be avoided by careful analysis and design.

Crosstalk.Multi-axis mechanisms based on multiple motion feedthroughs through the chamber wall incorporate universal and sliding joints to couple to compound mechanisms. This inevitably leads to crosstalk between motions and large backlash, both of which are negligible in mechanisms with internal motors.

Stability.Hybrid stepper motors have a detent torque (without drive current) of about 10% of their rated torque. AML design mechanisms so that the combination of detent torque, static friction and gearing is sufficent to maintain the position of each axis with no movement when the phase current is removed. Position information is maintained in the SMD2 drive in the absence of power. Where the best stability is required all sources of vibration must be decoupled from the chamber: this is particularly important in the case of turbomolecular pumps.

Stacking order. The stacking order of motions using vacuum motors is relatively unconstrained and this can lead to considerable advantages and operational convenience. Together with negligible backlash and crosstalk this makes accurate eucentric goniometers for large samples practical. Stacking order is an important concept, which is best illustrated by a typical example. Consider the requirement to illuminate any spot on a sample with a focused beam, which is fixed with respect to the vacuum chamber. The angle of incidence of the beam is to be varied over a cone or square pyramid, whose axis is normal to the sample surface, with its vertex on the incidence point.

Using an edge-welded bellows approach, the X and Y axes of linear motion usually have to be fixed with respect to the mounting port. This means that the location of the incidence point is convolved with the axes of rotation XR and YR, which define the angle of incidence. The motion of the point of incidence across the sample is not the same as that of the X Y stage and it moves if the angle of incidence is changed. Because of the convolution of rotation and translation it will be necessary to have a Z motion along the axis of the port to restore the point of incidence to the focus of the beam. If the axis of the mounting port is not accurately aligned to the axis of the beam then it may be necessary to have a port-aligner.

Using vacuum motors the XY axes are fixed on the sample surface and the rotation axes are the same. Therefore, if the angle of incidence is changed the point of incidence does not change. The incidence

point moves across the sample surface by exactly the same amount as the XY motion, regardless of the angle of incidence. Normal incidence and the centre point of the sample are defined by four numeric addresses (which may be zero) set into the SMD2 controllers. There is no need for a Z motion or port aligner.

Maximum Speed.The speed of the output plate of the mechanism is the product of the stepping rate and the resolution. The maximum slewing speed of a mechanism is dependent on the load imposed, and the gearing between the motor and the output. The load is dominated in most cases by the weight of other mechanisms stacked on the output plate. Lightly loaded mechanisms can slew at >2kHz and the most heavily loaded will slew at 500Hz stepping rate. Because of the absence of the high loads due to atmospheric pressure, internally motorised mechanisms can be ten times faster than those based on edge-welded bellows and motorised externally. With high-resolution mechanisms translations of a few mm per second and rotations of a few degrees per second are practical.

FOCUSED BEAM

CONE OF INCIDENCE

SAMPLE

AXES ON PORT

FOCUSED BEAM

CONE OF INCIDENCE

SAMPLE

AXES ON SAMPLE SURFACE

Orthogonality and concentricity. Orthogonality of linear axes will be set to ±0.5° and concentricity of rotations within 0.2mm. If finer settings are required then micrometer adjustment screws can be provided together with metrology attachments for adjustment after installation.

Loads and Forces. Standard translation mechanisms can exert forces of about 10kg, which is limited by the leadscrew and nut combination. The rolling resistance of a translation mechanism is usually a few hundred grams. Mechanisms will usually support much larger masses than 10kg, depending on the guidance system. The effect of static torques exerted by offset loads must be considered. Standard rotation mechanisms are not designed to produce large output torques, so if the axis of rotation is not vertical it is important to keep the centre of gravity of the load close to the axis. Custom-designed large-force mechanisms and high-torque reduction gears can be provided.

Sample heating and cooling.AML will supply and fit heaters, thermocouples and cooling braids for attachment to cryostats, as required.

Outgassing and bakeout. AML motors and mechanisms are designed specifically for UHV, using appropriate materials, handling and construction techniques. For use in UHV, baking at 175° to 200°C is essential, after which outgassing rates of the order of 10-8 millibar litre per motor will be achieved. The actual gas load depends on the duty cycle of the motions and the phase current of the motors. Mechanisms are designed so that the motors can be switched off when the load is stationary and most motions can be swept over their entire range in less than a minute. As a ‘rule of thumb’, 100 litres sec-1 of additional pumping capacity per motor will be necessary to achieve ultimate UHV.

Sample holders and Sample changing. De-mountable sample holders can be provided. They can be insulated and have pluggable electrical connections. Mechanised sample entry via a load-lock is performed either with a magnetically coupled linear feedthrough or with a passive mechanism activated by one of the motorised axes or an additional motorised mechanism. Typical situations are illustrated and discussed in AML Application Note 30.

ReliabilityThe only components in UHV stepper motors subject to wear are the bearings, which have a life of decades in normal service. Where there are moving parts in rolling contact dissimilar materials and surface treatments are selected to avoid galling or wear. Aluminium-bronze nuts (used in conjunction with leadscrews) have a life of several thousand hours of full-speed motion and are easy to replace. Worm drives are used only when necessary because of space constraints and are arranged to have low speeds and loadings and to be accessible for easy replacement. Linear guidance systems are designed to avoid sliding contacts.

Lubrication.Sliding surfaces in leadscrews and worm drives are lubricated with NyeTorr TM

5200 synthetic lubricating gel for mechanisms which are not intended to be baked. Lubrication increases the life of these components. Various dry-film lubricants and low-friction surface treatments can be used, according to the requirements of the application.

Space Requirements. It is very important to consider the realistic space requirements of mechanismsbefore designing the chamber to accommodate them. Single axis mechanisms with light loads can usually be made with an output plate height of 30mm. They are designed for direct stacking, but where more than three mechanisms are stacked additional space for increasing the rigidity of the lower stages may be necessary.

Where space is very restricted, the design costs quickly escalate. For example, the additional cost of designing a six–axis goniometer to fit a minimal space can easily exceed the cost of a larger chamber.

Controls, cables and feedthroughs. Mechanisms are designed for use with, and are normally supplied with SMD2 drives cables and feedthroughs. Usually one MLF18 feedthrough and cable per three motors and one SMD2 drive per two motors are required. All internal and external cables are are pluggable onto the electrical feedthroughs. Motors are wired to intermediate VTB6 terminal blocks fitted near the motors, where appropriate.

Specification of multi-axis mechanisms

Describe or define:- 1. the application 2. the axes with respect to either the mounting plane or the sample surface, as

appropriate3. the orientation of the axes and the sample surface at centre-travel with respect

to gravity. 4. the stacking order of motions, if critical 5. the sample size, weight and position of centre of gravity, including any sample

holder6. the resolution and limits of motion for each axis 7. the maximum duty-cycle of motion for each axis 8. whether there is a requirement for a clear view through the sample or any

cones or other volumes in front of the sample which must remain clear9. heating, cooling, electric insulation or electric connection to the sample to be

supplied or accommodated 10. the method of sample changing, if any 11. acceptable lubricants 12. the space available 13. the chamber wall temperature in normal operation and in bakeout. 14. any electromagnetic or ionising radiation, electric or magnetic fields or

materials being deposited 15. the base pressure

Technology

Aml catalogue 13