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Tin Whiskers Grown on PCBA Detail Presentation Terry Munson Foresite Inc www.Residues.com [email protected]

Tin Whiskers Grown on PCBA Detail Presentation

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Tin Whiskers Grown on PCBA Detail Presentation. Terry Munson Foresite Inc www.Residues.com [email protected]. 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. - PowerPoint PPT Presentation

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Page 1: Tin Whiskers Grown on PCBA  Detail Presentation

Tin Whiskers Grown on PCBA Detail PresentationTerry Munson Foresite [email protected]

Page 2: Tin Whiskers Grown on PCBA  Detail Presentation

PCBA Capacitor area of Interest

Page 3: Tin Whiskers Grown on PCBA  Detail Presentation

Battery Battery voltage

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

Page 4: Tin Whiskers Grown on PCBA  Detail Presentation

203-0071-001 – Murata (MPN:GRM155R61A104KA01D) – C685203-0075-001 -  Yageo (MPN:CC0402KRX7R7BB103) – C683,C684

C685

C684

C683

GND

GNDVCC_BAT

VCC_BAT

Page 5: Tin Whiskers Grown on PCBA  Detail Presentation

Tin Whisker only on the Power Input Side

Page 6: Tin Whiskers Grown on PCBA  Detail Presentation

Tin Whisker on capacitor #2

Page 7: Tin Whiskers Grown on PCBA  Detail Presentation

Tin Whiskers on Capacitor #5

Page 8: Tin Whiskers Grown on PCBA  Detail Presentation

Typical Electrochemical Migration

Page 9: Tin Whiskers Grown on PCBA  Detail Presentation

Long Tin Whisker 5.16 mm

Page 10: Tin Whiskers Grown on PCBA  Detail Presentation

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

Page 11: Tin Whiskers Grown on PCBA  Detail Presentation

Tin Whiskers on Cap #2

Page 12: Tin Whiskers Grown on PCBA  Detail Presentation

Corrosion and Initial Whisker on Cap #8

Page 13: Tin Whiskers Grown on PCBA  Detail Presentation

PCBA with ESD Bag over caps

Page 14: Tin Whiskers Grown on PCBA  Detail Presentation

SEM of the Whisker Removed from Cap

Page 15: Tin Whiskers Grown on PCBA  Detail Presentation

SEM of Tin Whiskers

Page 16: Tin Whiskers Grown on PCBA  Detail Presentation

SEM of Tin Whiskers

Page 17: Tin Whiskers Grown on PCBA  Detail Presentation

Inside ESD Bag over area of Cap

Page 18: Tin Whiskers Grown on PCBA  Detail Presentation

Inside ESD Bag 1 inch from Cap Area

Page 19: Tin Whiskers Grown on PCBA  Detail Presentation

Foresite Tin Plated Electrode

Page 20: Tin Whiskers Grown on PCBA  Detail Presentation

Foresite Test Samples

Page 21: Tin Whiskers Grown on PCBA  Detail Presentation

C3 extraction /Ion Chromatography Results

all values in ug/in2Board # Location Chloride Sulfate WOA Sodium AmmoniumBrd #1 1. Cap with whiskers and ESD Bag 15.98 9.85 18.05 3.23 22.36Brd #1 2. Cap without whisker and ESD Bag 1.36 0.33 19.34 1.26 2.04Brd #1 3. Cap without whisker no ESD Bag 1.59 0.54 18.47 2.05 1.69Brd #1 4. ESD Bag above whiskered cap 44.84 17.95 0 0 36.96Brd #1 5. ESD Bag 1 inch away from cap 41.05 16.36 0 0 51.27

Brd #2 1. Cap with whiskers and ESD Bag 18.95 8.04 15.24 1.69 16.11Brd #2 2. Cap without whisker and ESD Bag 1.05 0.61 16.94 2.66 1.25Brd #2 3. Cap without whisker no ESD Bag 0.95 0.52 15.47 1.65 1.05Brd #2 4. ESD Bag above whiskered cap 29.44 12.33 0 0 22.96Brd #2 5. ESD Bag 1 inch away from cap 31.05 14.26 0 0 35.05

Brd #3 1. Cap with whiskers and ESD Bag 16.69 8.24 16.55 2.36 9.65Brd #3 2. Cap without whisker and ESD Bag 1.14 1.22 17.41 2.15 1.69Brd #3 3. Cap without whisker no ESD Bag 1.62 1.06 16.53 2.63 1.52Brd #3 4. ESD Bag above whiskered cap 35.98 15.36 0 0 16.96Brd #3 5. ESD Bag 1 inch away from cap 38.54 16.27 0 0 21.25

C3 localized Extraction and Ion Chromatography

Page 22: Tin Whiskers Grown on PCBA  Detail Presentation

Some Other Current Tin Whisker Work

Page 23: Tin Whiskers Grown on PCBA  Detail Presentation

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.