The reason I say they are probably large vias is we had seen that once in
the past. Customer spec'd a 28 mil via with silver epoxy fill. They placed a
heavy BGA component right over those filled 28 mil pads/vias...the larged,
silver-filled vias acted as a heat-sink drawing too much heat into them
causing delamination only around those vias. We reduced the hole size, the
problem went away. We also did another job for them where we could not
reduce the hole size, we used ceramic fill instead of epoxy, no problems at
all... Just one persons experience, hope this helps...
Franklin
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