vH&S, Apr. 2011 ASTRA 2011, 12-14 Apr. 2011

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Comparative tests on Electronic Technologies Comparative tests on Electronic Technologies to be compatible with thermal cycling over to be compatible with thermal cycling over

extreme temperature rangeextreme temperature range

Dr. Sabine Klinknerklinkner@vh-s.devon Hoerner & Sulger GmbHSchlossplatz 8, D-68723 Schwetzingen

11th ESA Workshop on Advanced Space Technologies for Robotics and Automation

ASTRA 2011

Co-authors: Nghiem Bao Duy Nguyen, Uwe Dose, Dr. Chris Gee-Yin Lee, and Dr. Josef Dalcolmo

vH&S, Apr. 2011 ASTRA 2011, 12-14 Apr. 2011

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Presentation OutlinePresentation Outline

Introduction

Test objectives

Test items

Overall test flow

Test results

Conclusion

vH&S, Apr. 2011 ASTRA 2011, 12-14 Apr. 2011

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ExoMarsExoMars BogieBogie Motor Controller (BMC)Motor Controller (BMC)

Basic requirements– BMC outside of thermally

controlled warm body– Electronics subject to extreme

non-operational temperatures for ~ 180 temperature cycles

– Operational range: -50°C to +40°C

– Non-operational range:-125°C to +40°C

– PP Sterilisation: 125°C

Qualification (test) temperature must exceed op & non-op limits by 10K

Non-redundant BMC consists of one controller and one power board

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Test objectivesTest objectives

Testing PCB-component level NOT the components themselves

5 populated boards – Four different configuration of

materials– One additional test item for

vibration test of ceramic substrate

Same schematic design, same layout as far as possible

Component types/packages representative of FM unit

Different track/via/pad geometries

Tested simultaneously

vH&S, Apr. 2011 ASTRA 2011, 12-14 Apr. 2011

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PCB materialsPCB materials

Thickfilm Hybrid PCBs– Matching CTE, good thermal conductivity– Required dimensions/configuration not space qualified

Polyimide board– High thermal resistance, CTE higher than ceramic – Fully space qualified

Solder– Indium-alloy solder remains ductile at low temperatures– Not space qualified

Parylene C Coating– Parylene is not ESA qualified Space applications MIL-I-46058C– Coating thickness with 1-20µm

Rigid-flex PCB– Light and compact solution– I/F to Ceramic boards

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Test itemsTest items

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TestboardTestboard layoutlayout

Ceramic test items Polyimide Test item

Flexboard with Wirebonds

Printed resistors

vH&S, Apr. 2011 ASTRA 2011, 12-14 Apr. 2011

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Overall test flowOverall test flow

1. Design of test items.

2. Manufacture/Population of test items.

3. Application of Parylene Coating.

4. Empty board tests.Application of Parylene Coating.Simulation of Dry Heat Microbial Reduction.Thermal cycling tests.

5. Simulation of Dry Heat Microbial Reduction.

6. Vibration test before thermal cycling.

7. Thermal cycling tests.

8. Vibration after thermal tests.

vH&S, Apr. 2011 ASTRA 2011, 12-14 Apr. 2011

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Test results of empty board cyclingTest results of empty board cycling

Application of DHMR process– 3 periods of 6h at 125°C

Visual inspection: All fine

10 thermal cycles with same test procedure as for populated boards

– Starting from ambient temperature– Heating to +50°C– Cooling to –135°C– Heating to ambient temperature

Visual inspection: Small patches of coating de-lamination on ceramic board

vH&S, Apr. 2011 ASTRA 2011, 12-14 Apr. 2011

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DHMR and Vibration Test resultsDHMR and Vibration Test results

Populated items use same DHMR simulation process as empty boards

The visual inspection did not reveal any change of board or coating properties.

DHMR simulation had no effect on functionality of test items

Ceramic boards withstand vibration test

Approval of Mounting method for ceramic boards

All five test items fully functional after test

No visual effect of vibration

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Thermal cycling test resultsThermal cycling test results

Three major failure types:Failures on transformer solder joints on ceramic boards, caused by glueing method.Loose solder pads on ceramic boards with indium solder.Loose Parylene C coating on all test items.

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Failure type 1Failure type 1

Failure of transformers on ceramic boards likely caused by glueinglocation, allowing tilt movement.Vibration may have damaged the solder joints.

Glue on Polyimide substrate Glue on Ceramic substrate

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Failure type 2Failure type 2

Pads on indium solder ceramic board come off.Effect increased with additional hand soldering process.Indium ceramic boards have different layer material configuration than tin-lead solder boards.Gold pad with indium solder delaminates easily from track layers below.

MOSFET pads on ceramic board Thermistor pads

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Failure type 3Failure type 3

Parylene C does not stick well to ceramic / glassivated surfaces.Parylene C is tested to survive temperatures down –160°C. Upper limit is given between 125°C and 220°C.Higher temperature and oxygen atmosphere shorten use life of Parylene C.

Backside of ceramicboard

Coating around MOSEFTson ceramic boards

Coating on polyimide item

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ConclusionsConclusions

Test provided various information on considered technologies– Polyimide board shows the best results with no broken solder joint.– Ceramic with tin-lead solder performed well few broken solder joints. – Ceramic with Indium solder most failures mainly lift-off of solder pads.

Test results do show a clear difference BUT none of the technologies can be clearly favoured/completely discarded

Three main error types– Gluing method of transformers Apply same gluing method as for

Polyimide board– Ceramic boards with indium solder Review material combination– Parylene C Alternative coating/ reviewing DHMR process

Limited number of samples no statistical conclusion

Further tests required