Mark,

A rule of thumb is that the greater the resin content the worse the
dimensional stability.  Lighter glass will also have different thread counts
in each direction.

Chuck Brummer


-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Tuesday, March 26, 2002 10:05 PM
To: [log in to unmask]
Subject: [TN] another materials question


I'm learning about laminate materials and read with interest several recent
tecnet emails on the subject.
I'd like to submit a question about a particular construction that is a
challenge with respect to registration.

The construction is all 2 core and 3 core.  The prepregs are 1-106 and
1-1080, which I have learned are described as resin rich.   The construction
is balanced with respect to copper weights, glass styles, core thicknesses,
and prepreg openings.

What I am observing with this part is variation in how much certain cores
shrink, lot to lot,
and variation that I would describe as a shift or possibly a rotation in
some of the internal layers.

Am I correct in assuming that these thin cores and these particular prepregs
will contribute to lower yields due to misregistration?   If anyone would
care to offer up ideas on how to tackle the registration challenge that I am
observing on this kind of construction, I would appreciate hearing your
ideas.

Mark J.