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From: chen xiao bo <[log in to unmask]>
Subject: PCMCIA Dimensional Stabilty
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Has anyone had any experience in controlling ultrathins (0.004 in 0.5/0.5) 
dimensional stabibity?
What are the factors that effect the ultrathins misregistration and how to
reduce the misregistration to the minmum.

Appreciate if anyone can provide an answer.

Thanks in advance

Chen Xiao bo


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======== Fwd by: Tony King / N ========
Chen,

Thin core can be difficult to control, but there are several things that
will improve registration:

1. Be sure that copper is solid around the tooling holes. This is important
for all core thicknesses, but critical for thin core.

2. Thin core material does not always lay flat at post etch punch (I assume
your process includes this operation) Signal over signal thin core is
especially sensitive to this, it tends to sag if not supported completely.

3. Proper venting is important, leave as much copper on the inner layer
borders as possible yet providing good venting.

4. Be very careful at layup of the cores, do not damage the tooling holes
when placing cores over the pins.  Cross section the outer layer tooling
holes if misregistration is noticed at drill. To build good boards you must
first build good tooling holes.

5. It goes without saying that scale factors at CAM must be optimized for
thin core movement.

NOTE:  Some people will say that scrub prior to image of cores is critical
and will cause distortion. If this is true, I have not found it significant.
I think the above 5 issues represent at least 90% of the causes for
misregistration, scrub may be a small portion of the last 10% but should be
the last place to look...

Tony King
Elexsys International Inc.
Nashua N.H.
Phone:  603-886-0066
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