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December 2009

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Subject:
From:
Steve Kelly <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Kelly <[log in to unmask]>
Date:
Tue, 22 Dec 2009 12:50:17 -0500
Content-Type:
text/plain
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text/plain (105 lines)
Hi Joe,
3 pieces of AP 8525 - DuPont. Bondply - polyimide adhesive 35 micron,
apical- 12 micron, polyimide adhesive- 15 micron. Cracks start in the 15
micron polyimide adhesive- no total failures yet - drill size 10 mils -
aspect ratio - nothing special. About 200 vias per part.  Thermal - +200c-
-60C as fast as they can cycle the chamber. This is one end of the flex -
the other end is a rigid flex - same flex build then added 2 layers of
polyimide rigid either side - this end shows none of the cracking so I
assume somehow the GI is stopping the polyimide adhesive from expanding as
much. Regards Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Fjelstad
Sent: December-22-09 11:58 AM
To: [log in to unmask]
Subject: Re: [TN] Via fill on flex

Hi Steve
 
Are all vias impacted or just some? If the latter, any common  
characteristics? (i.e aspect ratio, stack up, location in stack, etc.) For
shared 
edification, what are the materials in the set and  what are the cycling 
conditions and requirements? (at least so we can all  get a sense of what
kind of 
unreasonable requirements might be out there looming  on the horizon) 
 
Season's best, 
Joe
 
 
 
 
 
 
In a message dated 12/22/2009 8:26:57 A.M. Pacific Standard Time,  
[log in to unmask] writes:

Hi  All,

We have a 6 layer flex that my customer has to thermal cycle at  
temperatures beyond the rated Tg's of the material- the end use environment
is  about 
as bad as it gets. After repeated thermal cycles we start to see cracks  
develop in the glue layer used to bond the adhesiveless layers together.
Will  
some kind of via fill help this issue?

Thanks in  advance.

Regards 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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