I normally specify +/- .003 in. (or .07mm) for the thickness tolerance on
our boards...That's as tight as I dare go... they (the board manufacturer)
would rather it be looser...

We don't just use anyone to do our boards though... Quality matters and
since we use a mounting system that is sensitive to the board thickness we
have to require it.

Might it be that you need to control the thickness in one specific area of
the board due to some special mechanical constraint? Why not talk with your
Mechanical Engineer and see if he can design the fixture to be more tolerant
of variations in the board thickness?

You will save money in the long run... the tighter tolerances get, the more
you pay....


Bill Brooks
Senior PCB Designer - [log in to unmask] <mailto:[log in to unmask]>

Zoneworx, Inc.
40925 County Center Drive, STE 200
Temecula, CA 92591
http://www.zoneworx.com    <http://www.zoneworx.com>
Tel: (909) 296-1226 x 1037
Co-Director / Education Officer / Webmaster
for the San Diego Chapter of the IPC Designers Council
http://www.ipc.org/SanDiego/index.html
<http://www.ipc.org/SanDiego/index.html>





-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Wednesday, July 05, 2000 8:56 AM
To: [log in to unmask]
Subject: [TN] Tolerance on board thickness


Hi Technet,

It's quiet on Technet. Or is it just me ? Problems with the server again ?
Compensation for all the double messages from a few weeks ago ?
Anyway, I've got a small question :
We've ordered a 4 layer FR4 board with a thickness specification of 1.6 +/-
0.05 mm. The supplier says he can't build it with such narrow tolarances.
The customer won't accept anything worse than this.
What do you think, should the average fabhouse be able to build a board like
this or is it completely unrealistic ?
Hope to hear from you.

Kind Regards,

Daan Terstegge
SMT Centre
Signaal Communications
Unclassified mail
Personal Website: http://surf.to/smtinfo

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