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March 2012

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Subject:
From:
Leland Woodall <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Leland Woodall <[log in to unmask]>
Date:
Tue, 27 Mar 2012 18:18:20 +0000
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Folks,

We've ran across a strange incident and I'd like a little advice from the group.

We recently underwent a component vendor change, and part of the first group of boards were misbuilt due to incorrect polarity (the part marking was misinterpreted by the vision operator).

Anyway, an attempt to remove the part by our Repair group resulted in lifted pads on 10 of the first 12 boards.  We've analyzed the lead material beneath the SEM and it returns 98% tin and 2% silicone.  The old style component comes off quite easily (within 3 seconds), and an analysis of its leads shows to be 100% tin.  It's a 6 pin diode with very little mass.

What's going on here?  Does a 2% silicone mix raise the melting point of solder by 200 degrees C?

Please help me understand.

Thanks,

Leland

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