In addition to the comments of our venerable colleagues, the IPC has some
interesting formulas for determining minimum bend radii.  The specification
in IPC-2223, Sectional Design Standard for Flexible Printed Boards.  In
section 5.2.3.4, formulas for single- and double-sided circuits (with
coverlay) are given.  I made a rough Excel spreadsheet that helped me
determine the min radius for a "Flex to Install" application.

My first design didn't work too well because the circuit was too thick for
the required bend radius.  Using the IPC guideline really helped (gratuitous
pitch for the IPC), likewise with having nice, understanding engineers
(blatant gratuitous compliment) !

I have sent the file to you; if anyone else wants to get a copy, please give
me an e-jingle.
 <<Flex_radius.xls>>
Regards,
Roger M. Stoops, C.I.D.         [log in to unmask]
TRIMBLE NAVIGATION LLC
Engineering and Construction Division
5475 Kellenburger Rd.
Dayton, OH   45424-1099      USA
Telephone:  937 233 8921      800 538 7800      ext. 288
Facsimile:  937 233 7511

http://www.trimble.com


 -----Original Message-----
From:   Doug Pogatetz [mailto:[log in to unmask]]
Sent:   Tuesday, January 29, 2002 4:00 PM
To:     [log in to unmask]
Subject:        [TN] Minimum bend radius calculation in a flex circuit

I am on project that requires that I determine the minimum bend radius of a
flex circuit. I have not been able to find out any formulas or calculations
to help out.

I am a mechanical design engineer, so I am not up on all the terminology.
It will of the class "Flex to Install", and will be of the adhesiveless
type. Can anyone help out?

Thanks.

Doug

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