We do a lot of rigid-flex here,
but nothing like that.

You are already beyond my
experience. Sorry for the blurt.

Jack






             "Steve Kelly"
             <[log in to unmask]>

             01/10/2005 01:01                                           To
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                                       "'TechNet E-Mail Forum'"
                                       <[log in to unmask]>
                                       "'Jack C. Olson'"
                                       <[log in to unmask]>
                                                                        cc





                                                                   Subject
                                       RE: [TN] Flexible vs. rigid
                                       substrates









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Hi Jack,
There are many instances of flex circuits that are loaded with components
both sides and then the unit is rolled up into a circle (no stiffeners). In
some cases these are for high end military and they work even though they
violate all recommended design principals. Regards Steve Kelly

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack C. Olson
Sent: Monday, January 10, 2005 1:52 PM
To: [log in to unmask]
Subject: Re: [TN] Flexible vs. rigid substrates

I'm not sure if I understand your question,
(or if anyone else has answered already),
but I don't think the component area of ANY
type of assembly is intended to flex.

That's why the rigid areas are there under the
components, so no stress on solder joints.
Even pure flex circuits have stiffeners under
the component areas, from my experience.

So I wouldn't ever flex the rigid part of an assembly.

If that wasn't what you meant, write back, ok?

Jack






   Date:         Fri, 7 Jan 2005 16:22:28 -0600
   Reply-To:     TechNet E-Mail Forum <[log in to unmask]>,
                 "Simms, Michael" <[log in to unmask]>
   Sender:       TechNet <[log in to unmask]>
   From:         "Simms, Michael" <[log in to unmask]>
   Subject:      FW: Flexible vs. rigid substrates
   X-To:         "[log in to unmask]" <[log in to unmask]>
   Content-Type: text/plain; charset="iso-8859-1"



   > Hello T'Netters,
   > Recently, the issue of the use of rigid printed wiring boards in an
   > application
   > which demands that printed wiring boards be pressed into an outer
   shell
   > with some
   > degree of curvature has surfaced.
   > I'm accustomed to the use of flexible substrates for applications
   which
   > demand
   > any form of application in which the board does not stay flat.
   > However, I don't see any IPC document which mandates the use of rigid
   > boards
   > for 180-degree assembly applications and flex boards (or rigid-flex)
   for
   > anything else.
   > Are there any guidelines for the selection of one type over another?
   > Are there any reliability issues with the use of surface mount devices
   on
   > flex boards which don't also apply to rigid boards?
   > Why would a manufacturer opt for a rigid board over a flex board for
   > assemblies which
   > are subsequently flexed?  Is this a choice based on cost?

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