Subject: FAB: Moisture content Inner Layers

         An inner layer engineer would like to ask technetters the following:

1) Has anyone determined the % moisture content in inner layers, presumably
after oxide, that relates to potential delamination problems after lamination?
2) How is this moisture content measured and/or monitored?
3) What resin types (ie multifunctional, polyimide etc) are applicable?

>>>>>>>>>>Dave, we have not baked FR4 inner layers after oxide (and
reduction) for at least 8 years, if not longer, and do not have a
delamination problem. We did try some experimental work on BT epoxy
without baking, and found in this case that it did make a (big) difference.
The problem with baking of reduced oxide layers, is to bake long enough
to remove moisture, but at a time/temperature that does not reoxidise the
copper.

Dougal Stewart
Exacta Circuits
Scotland

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