Thanks for your insights Tom.

Some of our EE's here thought they could save money by incorporating all the
interconnections between the main board and a group of panel mounted
connectors and any other groups of connections that would go between boards
and other remotely mounted cards in the unit with rigid-flex technology that
otherwise could be solved with a standard ribbon cable with connectors.
There really isn't a tight constraint on the room in the enclosure... the
only thing we would be eliminating is the cables and connectors...

I stacked up the cost of the single rigid-flex assembly verses a group of
rigid boards and cables and connectors... the latter was much less
expensive.

The quantities projected for the product are in the range of a 1000 units a
year give or take a few hundred...

Let's say I can build the bare board in rigid form without the flex for 100
dollars, if I used the rigid flex approach it cost me 1,000. Granted I save
the cost of a couple cables and connectors but they amount to about 20
dollars cost... Somehow that just doesn't make economic sense... In this
case anyway... and I got multiple quotes, but yes they were all in the U.S.

I'm pondering 'what if' we used flex jumpers and stiffeners that solder to
the pins on the panel mounted connectors on the back panel and then use FFC
connectors on the rigid board... Do you suppose there are better cost breaks
going that way as opposed to incorporating the whole mess into a single
rigid-flex board?

http://www.imperial-connect.com/products/ffcconn/05A02.pdf


Also are we need to ask 'are we using techniques that make the board too
expensive?' 'Is cable replacement a bad application for rigid flex?' I can't
envision going to China for a 1000 units a year...

It seems from your comments that 10:1 costs are inherent in the technology.
I'm a little frustrated with this at the moment...

Thanks though very much for your insights... :) Perhaps there are others
with more points to add that I can consider in approaching this problem as
well...

Best regards,

Bill Brooks
PCB Design Engineer, C.I.D.+
Tel: (760)597-1500 Fax: (760)597-1510
Datron World Communications, Inc.
Vista, California


-----Original Message-----
From: Tom Stearns [mailto:[log in to unmask]]
Sent: Wednesday, November 01, 2006 10:11 AM
To: (Designers Council Forum); Brooks,Bill
Subject: Re: [DC] Flex Circuit costs... sticker shock?

Bill:

Flex is a custom designed and custom produced product so it will always cost
more than a catalog item. You pay for the high engineering content which is
always needed  when something new is in the works. Compared with PCB's, flex
is far more compex because the substrate is less stable dimensionally which
means you need much more elegant tooling and tool concepts. All this hits at
the startup which means small orders can be really costly.  Ever order a
scustom automobile?  duPont charges well over $150 per pound for  typical
flex dielectric compared with maybe $15 or so for PWB materials. ----begin
to see the picture?

When you buy a piece of flex you are buying both an interconnections device
and a  piece of assembly tooling. Not at all fair to compare wire cost with
flex cost---remember that wire is cheap, but takes a great deal of ghand
labor to convert into an interconnection. Flex sharply reduces the assembly
labrto---wire sharply increases it.

Rigid flex is the most complex and difficult flex product to built. It
contains mixed dielectrics and requires a greatdeal of in-process tooling.
Compared with PCB's, rigid-flex takes at least 3X the manufacturing steps.
When you factor in ridiculous MIL spec  testing (which is primarily based on
the concept of a guaranteed loss of 20% of production)  you begin to sense
why rigid-flex is costly. But rigid-flex makes all sorts of high density,
high-rel packages possible; without rigid flex we would not have  any of our
high-tech  weapons systems, smart bombs, etc. If it's a matter of bringing
the pilot back alive after a successful mission, would you carp about a few
dollars?

Can't understand your application----I don't see how you could replace a
rigid-flex board with a piece of ribbon cable and a connector. I think you
are in need of a good applications engineer.


Tom Stearns
3 Brander Court
Nashua NH 03063
603 889 2522

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