Thank you for confirming my position on dppm and AQL.

We make a number of different rigid board part numbers using 0.0025 inch
core material with 1 or 2 ounce copper on both sides.  We use two plies
of prepreg (usually 106) between the cores.  We periodically have
manufacturing lots where there is very significant loss due ot high
resistance shorts.  Our success rate in locating the source of the short
is around 10% or less and it requires 8 to 16 hours of effort ... not
cost effective.    Those that we have found were either foreign material
in the core or laminate voids in the core.   We do hi pot testing of
these thin cores before we use them.

Is there any data, articles, research available on the root cause of
high resistance shorts and/or how to prevent their occurrence?

Marti Tully
Quality Manager
Sanmina-Phoenix

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