You seem to thinking about shorting from where they grow to the neighboring
parts. But what if they break off and start traveling? 
Murphy says they go to the location where they can do most damage and in
today's SMT world a very short whisker is enough to cause a bad short.

Regards,
Ahne 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Thursday, 12 June, 2008 12:13
To: [log in to unmask]
Subject: [TN] Tin Whiskers - how long? Size matters!

Good day TechNet
A tin whisker question.  

If (hypothetically, as this thankfully hasn't been built yet) a pure tin
finish part is used, what sort of length whisker could happen?

What we are looking at is this: a part we want to use is only available with
a pure tin finish on copper.  Matte tin, not bright.  So if we use it, and a
tin whisker grows, how long might it grow?  If the part is (for example)
10mm away from adjacent parts, and a realistic maximum whisker length is
less than that, it obviously mitigates (YES, but does not entirely remove)
the risk.

The only value I've seen is in a Dave Hillman/Doug Pauls presentation from
Apex 05, wherein it is stated that they "can be 9.5mm long".  Dave /  Doug,
any comment on this?  Can you cite a source?  Does matte vs bright tin make
a difference?

regards,
 
Graham Collins
Halifax Production Engineering
(902) 873-2000 ext. 6215


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