Hi Ed,
I have do agree with you that none of the responses you have received explain
your solder joint failures. I did not respond, because I have never seen
anything like this. The only thing that comes to mind is that there are some
trace impurities in the copper and/or solder that migrated towards the
interface between the copper and the IMC layer. So the only advice I can give
you is to run an elemental analysis on both fracture surfaces and see if
there is anything there that should not be.
I would appreciate hearing about the outcome of this.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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