Is it the same pads consistently pulling off and are the pads connected to
traces?

Toby
On Mar 27, 2012 2:19 PM, "Leland Woodall" <[log in to unmask]> wrote:

> 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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