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Tin Whiskers Grown on PCBA Detail Presentation

Tin Whiskers Grown on PCBA Detail Presentation . Terry Munson Foresite Inc www.Residues.com Terrym@residues.com. PCBA Capacitor area of Interest. Battery. Battery voltage. Output from IC which supply to 3 capacitors (C683, C684 & C685). VCC_BAT. GND. C685. C684. C683. GND.

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Tin Whiskers Grown on PCBA Detail Presentation

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  1. Tin Whiskers Grown on PCBA Detail Presentation Terry Munson Foresite Inc www.Residues.com Terrym@residues.com

  2. PCBA Capacitor area of Interest

  3. Battery Battery voltage Output from IC which supply to 3 capacitors (C683, C684 & C685)

  4. VCC_BAT GND C685 C684 C683 GND VCC_BAT 203-0071-001 – Murata (MPN:GRM155R61A104KA01D) – C685 203-0075-001 -  Yageo (MPN:CC0402KRX7R7BB103) – C683,C684

  5. Tin Whisker only on the Power Input Side

  6. Tin Whisker on capacitor #2

  7. Tin Whiskers on Capacitor #5

  8. Typical Electrochemical Migration

  9. Long Tin Whisker 5.16 mm

  10. Tin completely used up to make the Tin Whiskers on the capacitor #1

  11. Tin Whiskers on Cap #2

  12. Corrosion and Initial Whisker on Cap #8

  13. PCBA with ESD Bag over caps

  14. SEM of the Whisker Removed from Cap

  15. SEM of Tin Whiskers

  16. SEM of Tin Whiskers

  17. Inside ESD Bag over area of Cap

  18. Inside ESD Bag 1 inch from Cap Area

  19. Foresite Tin Plated Electrode

  20. Foresite Test Samples

  21. C3 extraction /Ion Chromatography Results

  22. Some Other Current Tin Whisker Work

  23. Conclusions • The whiskers that formed on the powered side of the capacitor were not the result electromigraiton but localized heating of the capacitor power side and this released contaminants from the ESD dissipative bag waxy surface. This contamination was the driving force of the formation of the tin whiskers. No other areas of the PCBA show any sign of tin whisker or creep corrosion or even dendrite corrosion. The surface of the capacitor that grew the whiskers shows high chloride, sulfate, and ammonium which also was present inside the ESD bag (this is the dissipative elements inside the bag). The residues area not transferable to the board surface unless there heating or steam extracting. • Under similar conditions Foresite was able to get growth on the surface of the tin plated electrode of a tin whisker with the ESD bag and the 3.3 volt battery in a sealed bag in 5 days indicates that the mechanism is reproducible.

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