Thanks Werner,
 
If I solve this problem, I may have time to attend one of your seminars here
in the UK!
 
Neil

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: 09 May 2008 16:16
To: [log in to unmask]; [log in to unmask]
Subject: Re: [TN] Fw: [TN] Brittle FPC Tracks


Hi Neil,
No such standard exists or can exist, because [drum roll]-'It depends!'
It depends on thicknees of the layers [each one individually], the modulus
of elasticity [of each layer-from this the location of the neutral plane is
determined], and the ductility of each metallic layer [use IPC-TM-650,
2.4.2.1 "Flexural Fatigue and Ductility, Foil," or ASTM  E 796 "Standard
Test Method for Ductility Testing of Metallic Foil"].
Having all of this, you can determine the minimum sustainable bend radius.
You can find the methodology in IPC-D-330, Section 6.2.1.2 "Flexibility
Considerations in the Design of Flexible Printed Wiring"  [most likely
out-of-print] or in the upcoming book by Joseph Fjelstad Flexible Circuit
Technology, 4th edition.

Werner
Future workshops:
Reliability Issues with Lead-Free Soldering Processes, June 17, London
Interconnect Failures and Design for Reliability for PCB PTHs, June 17,
London
Pb-Free Soldering Processes-Survival, Quality, Reliability, August 18,
Orlando
Reliability Issues with Lead-Free Soldering Processes, September 22,
Schaumburg
Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture,
ENIG), September 22, Schaumburg



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