I do not remember the posting but:
        7628 will bond to the copper fine and give better dimensional
stability compared to a resin   pregpreg, but glass weave may impair your
ability to produce fine line circuits.

        resin rich prepreg against the copper gives you a flatter surface
for fine line geometry.

Chuck Brummer
Siemens AIM

-----Original Message-----
From: Tom Burek [mailto:[log in to unmask]]
Sent: Thursday, April 08, 2004 1:34 PM
To: [log in to unmask]
Subject: [TN] PCB Laminate/Stackup question


Hello Technetters,
I have a question about layer stack-ups.  Some time ago a respected
contributor to this forum presented us with some valuable information in
the form of a specification he developed.  In this specification, under
the title, MASTER DRAWING NOTES 1.0 Laminate, Core and Prepreg Material,
section 1.9 states,"There shall be no 7628 glass style prepreg used facing
copper. If
required, single ply or multi-ply 7628 core material may be used.  If used
as prepreg, 7628 only may be used between two other more resin rich glass
styles."
My question is what does this mean to the stack-up? Why should you not use
7628 facing copper?  Does it have to do with the amount of resin not
present in 7628 and may not bond to the copper sufficiently?  What should
be used? and Why?

I hope this question is not too imposing.

Thank you in advance.

Tom Burek, CID+


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