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July 2003

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Subject:
From:
Steve kelly <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 2 Jul 2003 13:51:09 -0400
Content-Type:
text/plain
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text/plain (74 lines)
Unless the circuit is really long what they are asking is very
excessive. If the part is a reasonable size the covercoats can be cut
into sections to maximize lay-up (this is normal in the industry). If it
is long they can measure the movement in the panel before covercoat
lay-up and compensate the drill program. .15 is standard in my world and
.1 can be done with care and some $. Good luck.

Steve Kelly

PFC Flexible Circuits Limited

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger
Stoops
Sent: Wednesday, July 02, 2003 1:16 PM
To: [log in to unmask]
Subject: [TN] Flex Circuit specifications

Hiya folks!

We are having some difficulty getting a flex supplier to build a circuit
to our specs.  The issue has to do with coverlay tolerance.  They are
requesting we open the coverlay openings so that they can use +/-0.50mm
location tolerance.  This allows for exposed copper between pads/lands
to be soldered during installation.  We have asked for +/-0.20mm
tolerance, but might live with +/-0.25mm to +/-0.30mm.  They **keep**
coming back asking for the loose tolerance each time we say no.  We have
already taken into consideration the annular ring and adhesive
squeeze-out, and cannot enlarge the openings by more than .10 or .15mm.

These are typically 2 to 4 layer flex circuits with plated holes,
polyimide lam with thermoset acrylic adhesive.

Am I just being to picky? hardnosed? stiff-necked? all the above?
What tolerances can I expect or ask for?
Any alternatives or other details I may not be aware of?  (Don't assume
I know a lot about flex.. thanks.)

Looking forward to your assistance,
Sincerely,

Roger M. Stoops, CID
Trimble Navigation Ltd., Dayton, OH, USA
Ph: +01 937.245.5288
Fax: +01 937.233.7511

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