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May 2006

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From:
- Bogert <[log in to unmask]>
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TechNet E-Mail Forum <[log in to unmask]>, - Bogert <[log in to unmask]>
Date:
Wed, 24 May 2006 18:49:20 -0400
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May 24, 2006

One Pb-free part lead/termination finish often used by part manufacturers is a 100% pure matte-tin plating process followed by annealing at 150C as a tin-whisker mitigation method.

My understanding is that folks should be able to solder any part with such a finish using a Pb solder alloy like Sn63Pb37.

However, we have an OEM who recently received a batch of axial lead diodes finished with what was indicated to be a 100% pure matte tin finish with annealing as a method to reduce the risk for growing tin-whiskers.  

The OEM receipt inspection of the parts in question noted gray appearing surface finish and that the parts were identified on the package as being Pb-free.  The OEM did a dip solderability test and noted that only about 5% of the lead surface was wetted with Sn63 solder.  They then tried to hand solder some of the parts with the same type results.

It appears to me, the problem lies with a poor tin-plating process by the part manufacturer, and not with use of annealed matte tin as the finish.

What experience with soldering matte-tin parts with Sn63 solder do folks 
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