TechNet,

What are the most likely causes for delamination in a multilayer rigid PWB?
Particulars of the assembly include --  boards are 8 layer Mil-P-13949/5
material, PTH, most components are wave soldered in place followed by hand
soldering of "selected components" including one power FET which is mounted
in a heat sink.  The delaminations are noticed (unfortunately) after the
boards come out of final test, just prior to conformal coating.  The
delaminations are always in the area at &  near where the leads of the FET
are soldered into the PTHs on the back side of the board.  I suspect
excessive heat somewhere in the process, but according to Production,
nothing has changed in the manufacturing processes for these boards & we've
made 30 or 40 sucessfully to date.  The delaminations appear to be
originating in the interior layers rather than the surface layers and are
bridging leads of the FET in several cases.  Thanks in advance for any advice.

S. Smith, Tracor AES

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