Hello, all.

I'm having to critique a board that is a very large flex circuit. It's kind
of funky in that it isn't a conventional board, but rather an array of 22
resistive sensors spread over a (roughly) 18x24 inch area. The board looks
like like six 1/2 inch fingers extending, vertically,  24 inches from a 2
inch, horizontal, section. The connector comes off the 2 inch part and each
sensor is mounted on the 1/2 inch stripes (either 3 or 4 sensors per strip.)

The current version of the board appears to have fairly wide traces
(eye-balling, they appear to be 10-15 mils), This sensor array will be in a
constant state of movement (it will sit on a dense foam pad which will be in
a regular state of "flex" as heavy items are laid on the pad), there fore,
the flex circuit will be flexed, a lot, over time.

Here are my questions:

1) How narrow can I make the traces on flex circuit?

Currently, the 2 inch horizontal part is full of 48 traces (2 per sensor)
and I'd like to re-spec that section to be narrower.

2) How much flex board material is needed to support the traces?

The current design has about 1/4 (maybe 3/16) inch of flex material on the
board edge. That is, the routing outline is 1/4 inch inside the board edge.
Can this be reduced to 1/8 or 1/16 inch, or less? If I can go to 8 mil
traces (with 8 mil space) and use 1/16 inch between the board edge and the
routing outline, then the portion of the board that has only 2 traces would
be .149 inches wide ((.0625 X 2) + (.008 x 3)).


Thanks,
David R

-----------------------------------
David M. Ransier
Senior Consultant
Intercept Technology Inc.
[log in to unmask]
503-692-0111  www.intercept.com
503-691-9535 - Fax
404-352-0111 - ITI Headquarters

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