A really good reason for using adhesiveless is to reduce Z axis expansion in
multiple layer boards.  In your case it probably has less benefits.  You do
not say if your application gets hot or not so I can not judge if softening
of the adhesive and delamination of the circuit from the carrier polyimide
affects you..

The acrylic glass transition temperature (Tg) is just above room temperature
and once you are past the Tg the material  expands much more than below the
Tg and you will find a lot of previous discussions on thing like cracked
barrels, post separation lifted lands and other interesting things like
voids in the acrylic, etc. on multilayer boards in the TechNet archives.

----- Original Message -----
From: "Roger Stoops" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, April 22, 2003 1:26 PM
Subject: [TN] Cost Comparison of Flex Circuit Mat'l


Dear all,

  I guess there are two basic types of Cu-clad polyimide: Cu-clad polyimide
with adhesive and adhesiveless Cu-clad polyimide.  I am curious as to the
relative cost of each, and the advantages or limitations of using either
one.  The end use is Class 2, Type 5A (flex to install), in a (fairly)
sealed enclosure that will see temps of -20C to +85C.  Only two copper
layers, no plated holes.

  In the past our FPCs have always been of the Cu-adhesive-polyimide type.
I want to know if there would be any advantage to using the adhesiveless
stuff, besides thinner circuits.

Cordially,

Roger M. Stoops, CID
Trimble Navigation Ltd., Dayton, OH, USA
Ph: 937.233.8921  or  937.233.4574  ext 288
Fax: 937.233.7511

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