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February 2010

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Subject:
From:
Lee Whiteman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Mon, 1 Feb 2010 15:47:56 -0500
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First, thanks for all the inputs.

Second, Russell made an excellent point concerning the board material. I
just found out that the boards in question are polyimide, that has a Tg
~ 250C. I doubt that going to 125C would make a difference - am I wrong
on this assumption?

When I get my copy of IPC-7721, I'll read it. I am curious if you have
to bake a polyimide board above the Tg (~ 250C), what temperature do you
go to and for how long? What is the heating rate and cooling rate? Or is
this a case of On The Job Learning (OTJL) better known as trial and
error?

Lee Whiteman, PMP
Senior Member Engineering Staff
L-3 Communications East
Telephone: (856) 338-3508
FAX: (856) 338-2906
E-Mail: [log in to unmask]
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Nowland, Russell
Howard (Russell)
Sent: Monday, February 01, 2010 3:41 PM
To: [log in to unmask]
Subject: Re: [TN] IPC-7721 LESSONS LEARNED

After reading the original question I had to pull the spec and read it.
I could see doing this for bare boards but the spec eludes that you can
also do this on a populated board.  Since you are forcing a board flat
with components on it is anyone concerned about cracking components or
solder joints here?

The spec also states the bake temperature is 125 C but what if you are
using material with a Tg of 170C?

I have never tried this and I am a little curious.

Russell Nowland
Alcatel-Lucent
Advanced Manufacturing Engineer
Address: 14000 Quail Spring Parkway, Suite 300
Oklahoma City, OK 73134
email: [log in to unmask]
Desk: 405-302-1660
Cell: 405-203-0034
Fax: 405-302-1622
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