Hi Bev! We have been using immersion tin surface finish for about 1 year
and have had no issues with whisker growth. During our qualification
testing the whisker issue was a very important test matrix question and we
requested the all of the immersion tin suppliers furnish their tin whisker
data. The immersion tin chemistry suppliers (well, at least one for
certain!) appear to have successfully engineered chemistries which do not
permit whisker growth. My recommendation would be to work closely with the
pwb fabricator and/or the chemistry supplier to understand what they are
doing to eliminate whisker growth. Now if you want to really get nervous
just think about the component fabricators who are choosing to use matte
tin as a component lead finish - let's hope they have done their
homework/testing.

Dave Hillman
Rockwell Collins
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Bev Christian <[log in to unmask]>@ipc.org> on 04/02/2002 05:40:04 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
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Subject:    [TN] Tin whiskers and immersion tin coatings


Technetters,
To a certain extent I am aware of the work the NEMI tin whisker task force
and various connector/component manufacturers are doing about 100% tin
coatings.  But I am still left with several questions whose answers I have
missed or questions that have not been addressed.  So... here goes - the
immersion tin coating are for SMT pads that are going to be soldered.  What
are people doing about test points? Are there stencil openings to put
solder
on these pads as well?  Or are these pads left unsoldered?  Has anyone
carried out any testing with regards to the tendency of these materials to
grow/not grow whiskers? Or do the organics in the coating completely kill
that possibility?

regards,
Bev Christian
Research in Motion

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