[sdiy] Tin Whiskers

[Scott Gravenhorst]

Glen <mclilith at charter.net> wrote:
>I've known about zinc and tin whiskers for a long time. They're common
>problems inside Hammond organs. The ironic part is, what was supposed to be
>a plating applied to a steel chassis to insure the longevity of the
>product, turns out to be what "kills" the circuitry mounted in or near the
>chassis. The problem seems much worse if you live in tropical areas, or
>very near the coast.
>
>Did NASA mention that these whiskers are known to become airborne and land
>on nearby circuitry, causing current leakage, short circuits, and generally
>weird circuit behavior? It happens in the Hammond organs all the time.
>
>I'm not sure what to do about whiskers on IC leads. Did NASA have any
>suggestions for suppressing whisker growth?

Heh, not that I saw, this was new to me and I was horrified.  After looking
at the images, I realized that I'd seen this occasionally as a frosted look
on a component lead.  I never thought much about it, but after seeing the
micrographs, I realized how this can easily cause weird circuit behavior. 
Then I thought, "what to do to fix a device that has whiskers".  I'd like to
hear discussion on this.  I'm sure that the vintage guys here either are
concerned or know some things.  What springs to mind is perhaps a wire brush
followed by a healthy blast of compressed air.  Perhaps reflowing solder? 
But then that may only deal with a current iteration of the problem, removal
of the whiskers that exist now doesn't prevent them from forming again. 
I've worked as a computer hardware engineer for DEC in years past and this
can explain at least some of the totally crazy things I saw in the field. 
And I wonder if potting a circuit would prevent the whiskers??  (not that I
want to pot everything...)



>At 05:07 PM 1/11/05 , Roman wrote:
>
>>that's scarry!
>>It's like we're all doomed, no matter what we do.
>>I have never imagined such a thing.
>>No wonder they make you replace the FCP every 2-3 years.
>>Otherwise it would get covered in whiskers anyway
>>
>>Roman
>>
>>----- Original Message ----- 
>>From: "Scott Gravenhorst" <music.maker at gte.net>
>>To: <synth-diy at dropmix.xs4all.nl>
>>Sent: Sunday, January 09, 2005 2:27 PM
>>Subject: [sdiy] Tin Whiskers
>>
>>
>>> http://nepp.nasa.gov/whisker/photos/index.html
>
>
>
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