Steve,

I would (with great caution) aquestion if polyimide would be the ideal 
material for such extrem handling. Polyimide (Kapton) has some properties 
that most people avoid to talk about. Many years ago, I warned my collegues 
to blindly use this material for our fighters (we make military aircrafts). 
The reason is  that I got the result from the investigation of a deadly 
flight close to Nova Scotia. Without going into details, polyimide simply 
can change its mechanical/electrical characteristics when exposed to harsh 
environment a longer time. There are many PI makers, so there ought to be 
some difference. If PI still got the said disadvantage, I can't tell you. As 
I said, one needs to be very careful with what to say in this forum. The 
conclusion is that FR-4 might be as good as polyimide. You must not use my 
comment for any decision, but do your own research. As I said, the crash 
investigation was done many years ago. I feel a little uncomfortable 
announcing this, but your choice may be important.
/Inge

http://www.usatoday.com/money/biztravel/wiring/w002.htm


----- Original Message ----- 
From: "Steve Kelly" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, July 14, 2009 9:11 PM
Subject: [TN] Storage life for rigid flex


Good Afternoon,

We have a program for some reasonably simple rigid flex (4-8 layer) where 
the requirement is a 20 year life in storage conditions from -40C to +125C. 
Is there any evidence that polyimide rigid material and pre-pregs would be 
better than a good FR-4 (170C) for long term reliability. Thanks. Steve 
Kelly



Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS)

(416) 750-8433 (work)

(416) 750-0016 (fax)

(416) 577-8433 (cell)




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