It is FR-4 in molded polycarbonate housing.

________________________________

From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Wednesday, August 09, 2006 7:44 PM
To: James Verrette; [log in to unmask]
Subject: Re: [TN] Routed edge tolerance


Hi Jim,
I do not know what kind of housing you are putting your PCB in, but from
your outline description I am guessing some cast housing. You are also
not giving us a clue about your application. You are also talking about
punching instead of routing, so i am guessing CEM-3 instead of FR-4 as
the PCB material.
In that case, your routing tolerances are your least problem; much more
worrisome are likely the different thermal expansions of the PCB and the
housing as well as swelling of the CEM-3 with moisture absorption.
GM ran into this with their windshield wiper controls: single-sided
CEM-3 PCBs in some combination of routing and housing tolerances
requiring press-fitting the PCBs. The result: windshield wiper failures
for some of the more high-end [read: high-powered=running hotter] SUVs
within as little as 1 year after sale due to solder joint failures
caused by PCB warping-over 4 million vehicles were ordered by NHSTA to
be recalled. 

Werner


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