[tinwhiskers] Re: Tin Whiskering on PCBA Capacitors in Storage
- From: Daicheng_Fu@xxxxxxxxxx
- To: tinwhiskers@xxxxxxxxxxxxx
- Date: Wed, 16 Feb 2011 12:10:48 -0800
I would like to add my two cents here. We happened to have multiple field
failures that looked very similar to the photos in Terry Munson's article,
but we determined these to be silver-sulfide rather than tin whiskers.
All the field failures were from high sulfide environment, one of them is
a dairy farm. The needle shape crystals grew from two areas, the primary
area is along the tin plating edge, and a few of them grew right from the
center of endcap surface. These crystals looked different from tin
whiskers I grew in my experiments,
they were darker, shorter and much thicker. We think that along the tin
plating edge, some silver were exposed and it started the following
reaction.
2H(+) + 2e(-) -> H2
2Ag + S(2-) -> Ag2S + 2e(-)
We think the silver sulfide whiskers in the middle area were caused by
think tin plating. The actual failures in our case were not bridging, the
product failed because of value change and complete open due to silver
depletion.
We have since added conformal coating for those customers that we know are
in high sulfide environment, and this process change proved to be quite
effective.
Regards
Daicheng Fu
Pullman, WA
From:
Rod <rod.dalitz@xxxxxxxxxxxxxxxx>
To:
tinwhiskers@xxxxxxxxxxxxx
Date:
02/16/2011 10:06 AM
Subject:
[tinwhiskers] Re: Tin Whiskering on PCBA Capacitors in Storage
Sent by:
tinwhiskers-bounce@xxxxxxxxxxxxx
On 16 Feb 2011, at 16:11, Pedro Tort wrote:
> An article on SMT Magazine about how and when whiskers grow on
capacitors inside an ESD bag.
>
> http://www.ems007.com/pages/zone.cgi?artcatid=&a=74567&artid=74567&pg=1
FAscinating, but I hate the format, so much more useful as a PDF.
Figure 7 seems to show curvy whiskers, almost wooly, not what I expect to
see.
regards, Rod
rod.dalitz@xxxxxxxxxxxxxxxx
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