Hi Susan,
The degree of cure is certainly a concern. I am pretty certain that the
laminates are fully cured--to what degree the prepreg layers are depends on a lot
of variables, but they are hardly ever cured to the same degree as the
laminates.
So my issue is not so much with the laminators, but with the resin suppliers
[sometimes of course, they are the same]. The resin/prepreg suppliers need to
give valid data for the materials they supplied, when they are fully cured.
The PWB fab houses need to make sure that their PWBs are in the laminating
presses long enough and at sufficient temperature to achieve the necessary levels
of cure--what it will take will vary with resin, glass-cloths style, lay-up,
etc.
As to your question: "when will a fabricator know that the board they make is
to be assembled in a LF process?"-- the answer is that his customer needs to
tell him. For LF-PWBs, the customer had better spec'ed the PWBs properly in
the procurement RFQ, in terms materials, plating thickness, drill hits, etc.
Unless this is done it will be quoted for SnPb-soldering capability, which for
higher end PWBs is inadequate for LF-soldering.

Werner

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