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WP4 update

This article discusses the issues and solutions regarding glue assembly in mechanical/thermal assembly processes. It covers topics such as conducting glue bias connection, glue effects on wafer passivation, resistance aging, and temperature cycling.

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WP4 update

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Presentation Transcript

  1. WP4 update • WP4 aims: look at Mechanical/Thermal/ Assembly issues • effort weighted to latter end of period • Glue • Assembly Ray Thompson Calice meeting UCL 6 Mar 06

  2. Glue - About as sexy as insurance But too late to start worrying when production faults start - Are small no of faults the thin end of a long wedge? Atlas Barrel - Peek module mounting Brackets glued to Carbon Fibre cylinder CMS Tracker modules - Conducting Glue Bias connection to backplane Ray Thompson Calice meeting UCL 6 Mar 06

  3. CMS tracker module glue problems Tony Affolder, UCSB • Of 51 TOB modules built, we found 29 sensors with 1K to over 40M ohms higher than normal resistance in the bias connection. • Added strictly defined mixing procedures for the Tra-Duct 2902. • Applied epoxy immediately before sensor placement. • Switched to using Epotek 129-4 silver epoxy. Evidence problem is glue to sensor interface, not glue to gold pad No effect - eventually decided to wire bond as well

  4. Literature search Electronics industry experience Other Experiments - small no of tried glues Conducting Glues Silver filled 2 part epoxy ( no mass loss no voids) Ag has high conductivity, Silver oxide conducts realise conductivity ~1/1000 solid Ag -interconecting particles choose particle size , viscosity,,cure temp EPO-tek 4110 Areas of interest - resistance aging Interface problems oxide layer at Al/Ag interface Production wafers old CTE mismatch Si /PCB - glue flexible Glass transition temp CTE change 50 x10-6 to 150 x10-6 Corrosion/electro chemistry – Ok for N2 atmosphere Glue effects on wafer passivisation

  5. Glue test set up Programmable Environmental chamber Resistance measurements either Keithley 2000 DVM Keithley 236 SMU Labview Ray Thompson Calice meeting UCL 6 Mar 06

  6. Glue robot Resistance snake Tests Silicon / al Pc board / gold DR 0.1 ohm/50 dots 50 dots continuous monitoring Ray Thompson Calice meeting UCL 6 Mar 06

  7. Temperature cycling Temperature cycling 20-70 1 deg/ min Upwards resistance rise Consistent with silver temperature coefficent On contraction Interfaces become loose? Ray Thompson Calice meeting UCL 6 Mar 06

  8. Further stages Silicon wafer Talking to Prague people about availability of wafer samples Duff wafers, Mechanicals, Test structures at edges Double sided Pc Measure lots of pairs after cycling Real stresses – info from steve on likely temperature distributions Automated assembly 85/85 tests standard 85C /85RH aimed mainly at corrosion problems Ray Thompson Calice meeting UCL 6 Mar 06

  9. Finish off writeup of literature search Test set Up taking data . Continuing with Prague samples etc Interface stuff only meaningful with final objects - Test Beam prototype – known dead channels? Electronics – at what point does glue resistance become noticable? Ray Thompson Calice meeting UCL 6 Mar 06

  10. Assembly concepts • Start thinking about on pick and place techniques for assembling detector planks • Don’t reinvent the wheel • Look at/ exploit existing stuff CMS/Atlas experience • Generalised concept of a gantry with interchangable tools • pattern recognition software Ray Thompson Calice meeting UCL 6 Mar 06

  11. CMS tracker module assembly gantry Ray Thompson Calice meeting UCL 6 Mar 06

  12. Interchangeable Vacuum pickup tool Ray Thompson Calice meeting UCL 6 Mar 06

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