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July 2010

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Werner Engelmaier <[log in to unmask]>
Date:
Fri, 2 Jul 2010 11:22:05 -0400
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 Hi Eric,
Incomplete cure of the prepreg layers could be part of the cause, but the commercially available hot bars, particularly longer ones, have uneven temperature as well as contact pressure distributions.  
Werner

 


 

 

-----Original Message-----
From: Eric Christison <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Jul 2, 2010 11:12 am
Subject: [TN] Question about FR4 Curing


I'm wondering about an issue we have with the dimensional stability of a substrate made of FR4. 
 
We're finding it's deforming during a flex attach operation, not by much but enough to cause us a problem. We use ACF and a hot bar. The substrate sees a temperature of 155 deg C for about 10 seconds. Someone suggested that the movement may be due to incomplete curing of the substrate. 
 
I'm wondering if a temperature of 150 deg C for 10 seconds is likley to have any effect at all on the matrix. 
 
If it did, would the volume of the matrix increase, decrease or stay much the same? 
 
I realise that we'll see deformation due the application of pressure as well but in some instances the substrate seems to be moving in the wrong direction. 
 
Thanks, 
 
-- Eric Christison 
Consumer&  Micro group 
Imaging Division 
 
STMicroelectronics (R&D) Ltd 
33 Pinkhill 
Edinburgh EH12 7BF 
United Kingdom 
 
Tel:    +44 (0)131 336 6165 
Fax:    + 44 (0)131 336 6001 
 
 
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