Hi Ken,
You have to be more descriptive about where you find those cracks. Are the
cracks in the foil of layer #5, are they innerlayer separations at the
interface between the foil and the electroless flash, or are they innerlayer
separations at the interface between the  electroless flash  and the
electroplated copper. The loading conditions are the same in each case
(severe thermal expansion mismatch most likely in an area the has seen manual
soldering operations/rework), but the root cause/solution options are
different. From your incomplete description, the cracks may even be in the
PTH via barrel.

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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