February 13, 2004
I have no info on solder joint reliability when using pure tin. However, we had an application where we had a metal box holding several high precision resistors used in a circuit with very low current. The box was plated with pure tin. We saw numerous tin whiskers growing at right angles to the sides of the box. However, since they were very small in length, they did not cause any problems. Normally, even if the whiskers short to an adjacent conductor, they will quickly burn open. We cleaned off the whiskers then coated the box sides with conformal coating which prevented subsequent whiskers/
----- Original Message -----
From: David Douthit<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Friday, February 13, 2004 12:08 PM
Subject: Re: [TN] Pure Tin Component Finish
Scott,
Go to: http://www.nepp.nasa.gov/whisker/index.html<http://www.nepp.nasa.gov/whisker/index.html>
For the latest and greatest on tin whiskers.
David A. Douthit
Manager
LoCan LLC
Newland, Scott wrote:
>During our resent lead free evaluation it was discovered that several of our
>component vendors are changing their finishes from tin- lead to pure tin. Quite
>often this change is being made with no part number change, so these part are
>getting to our manufacturing floor without anyone knowing they have a different
>finish. This has lots of people's attention due to the Hi Rel nature of most of
>our products. We have narrowed our concerns to two: tin whiskers and solder
>joint reliability. There is a lot of work being performed on tin whiskers. Do
>you see the pure tin component finish impacting the tin- lead solder joint
>metallurgy to the point of impacting high or low cycle fatigue?? Typical I
>would think the component finish would be a small percentage of the total volume
>of the solder joint, resulting in minimal impact. But I'm afraid the
>inter-metallic layers maybe impacted, resulting in changed reliability.
>
>The opinions of this group would be valued.
>
>
>Scott Newland
>Harris GSCD
>321 727 6472
>Pager 321 690 4131
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