Thank you for answering this... At least I know I'm not losing my mind
trying to find it in IPC, (I'd rather lose my mind for other reasons, eh?)

The problem was that the vendor says its not their fault if the board came
in too thick, because the callout was ".093 nominal" with no tolerance
callout. I say if there is no callout then they have to use the one in the
title block "all three-place dimensions shall be .xxx unless otherwise
noted", right?

Anyway, thanks for all the responses....!

Jack

                -----Original Message-----
                From:   Cosentino, A. T. (Tony)
[mailto:[log in to unmask]]
                Sent:   Thursday, February 18, 1999 5:56 AM
                To:     [log in to unmask]
                Subject:        Re: PCB thickness & tolerance

                Jack,
                The old MIL-STD-275 had a design guideline which stated
+/-10% or 7mils
                whichever is greater. IPC-D-275 and  IPC-2221, which are
both design
                standards, do not specifically call out board thickness
tolerances nor
                do they publish any guidelines. I would stick with the
+/-10% rule for
                anything 70 mils or greater and +/-7mils for all other
boards unless you
                have a specific application which requires a controlled
thickness under
                these limits. I would then work closing with a board vendor
to achieve
                my desired results.
                Anthony T. Cosentino
                Lockheed Martin
                (703)367-1144
                [log in to unmask]



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