Hi Rick,
I would suggest you check out Appendix B of IPC-D-279, Design Guidelines for
Reliable Surface Mount Technology Printed Board Assemblies. What you have is
innerlayer separation (ILS) of which post separation is a subset. In all
likelihood, the affected layers are 2, 3, N-1, and N-2. The failures are
caused by a combination of land rotation and hydrostatic pressures on the
PTH/PTV barrel during the resin thermal expansion during soldering processes.
Depending on where the separations occur you need to check your wet processing
(Failure modes: foil/e-less Cu interface & e-less Cu/electrolytic Cu
interface) or use a better grade of copper foil (Failure mode: Foil cracking).
In any case, also chech maximum temperatures during soldering processes,
especially manual ones.

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]

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