Technetters,
I have an issue with the Mil spec MIL PRF 55110 F, which states that if you
see lifted lands in the microsection, that you then inspect the lot 100%
visually for seperation at 4X mag. and if not seen then the boards should
be acceptable.
I have to requalify using the 10 layer multilayer pattern of the MIL spec.,
but have not been able to do so due to minute cracking of the resin under
the pad, at the resin/glass interface, seen only at microsection at 200X.
It is not visible to the naked eye, or at 4 X. (I have a photo if required,
but have not attached it here due to bandwidth. besides, I don't want
spammed!- mail me if you need a copy please)but the requalification people
are insistent that as it is pad lift, although only seen under
microsection, it must fail. So when is pad lift not pad lift according to
the specification, or vice versa ?????
The PCB's are "as received", having only been HASL'd. Several "fixes" have
been tried, including reduction of copper plate thickness in the holes,
change of bonding prepregs from 1080 to 2113/2116 to reduce the resin
content, electroless copper instead of direct plate, higher Tg materials
instead of standard FR4, change of HASL temperature and dwell, ductility of
copper etc. (not all at once of course)
I am at a loss to explain this, especially on the requalification issue,
and am sure that several other fabricators have experienced this issue before.
What was the outcome, and what was the answer?
Hope someone can shed some light.
Colin William
"Opinions expressed above, are just that, and are my own, and do not
reflect those of my employer"
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