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Reply To: | TechNet E-Mail Forum. |
Date: | Wed, 2 Jul 2003 13:51:09 -0400 |
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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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