It's unlikely that you will find a board house that will accept to do
this... Tolerance could be easily exceeded when you take in consideration
plating of copper and lay-up. Typical fabhouse are more unlikely to accept
anything below +/- 0.13 mm (0.005").

A couple of questions:

Are you measuring over laminates, holes or fingers?
What kind of finish? (HASL, OSP, Au, .....)

Here is a bad way around it: EVALUATE ordering a bunch of boards, with as
tight as possible requirements, measuring and selecting the ones that are
within tolerances, add the disposal of the unused boards. When you suggest a
higher tolerance,  when you suggest relaxing the design a bit, the client
might reconsider.

"No matter how great a design is, it is useless unless it can be
manufactured."

Alain Savard, B.Sc.
Chemical Process Analyst
CAE Electronics Ltd.
e-mail: [log in to unmask]

-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: July 5, 2000 11:56 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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