This is exactly why the rating system that I proposed earlier is needed.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Tuesday, December 13, 2005 10:11 AM
To: [log in to unmask]
Subject: Re: [TN] Qualification of the Pb-free capable manufacturers
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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