>From your description of the failures I can not form a very accurate picture.
If I understand you correctly, your problem may be more related to thermal
expansion differences. This subject is complex enough, that I give one- and
two day workshops on the issue of thermal expansion mismatches and solder
joint reliability.

Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ  07945  USA
Phone & Fax: 201-543-2747
E-Mail: [log in to unmask]

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