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August 2010

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Subject:
From:
Brad Saunders <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brad Saunders <[log in to unmask]>
Date:
Mon, 16 Aug 2010 08:32:41 -0400
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Hello Gerry,
And everyone, thanks for the input.

It was a nice sanity check for me; the Customer clarified all thermal bakes are after soldering and related to assembly procedures such as BGA underfill and the like.  
Gerry, speaking of heat, I'll give you a buzz and we'll get coffee and talk PCBirds

Best regards, Brad
  ----- Original Message ----- 
  From: Gerald Gagnon<mailto:[log in to unmask]> 
  To: [log in to unmask]<mailto:[log in to unmask]> 
  Sent: Saturday, August 07, 2010 3:25 PM
  Subject: Re: [TN] Baking CCA's for hours


  Hey Brad,
   
  Good to hear you're back on the technet!
   
  Answer to this one is easy assuming we're talking FR4 and 125C is an appreciable way to the Tg of the material.
   
  Luckily because your customer specifies it, you are off the hook as long as you follow their specification.
   
  Save one CCA to "look at" as an "as received" control.
   
  Bake them for this bake cycle under the minimally controlled conditions you mention.
   
  Then after the bake, you pull out the as received sample (nice yellow-green color) and ask them what happened to the baked ones (kinda dark yellow-brown) and why (betcha none of them will know).
   
  For polyimide and the other dark laminates, it is harder to see the oxidative effects of the near Tg bake cycle but it does happen.....usually a color change and a reduction in mechanical strength. This is the basis for UL's direct support of live parts reliance on the MOT. 
   
  See you around!
   
  Gerry
   

   
  > Date: Thu, 5 Aug 2010 19:07:55 -0400
  > From: [log in to unmask]<mailto:[log in to unmask]>
  > Subject: [TN] Baking CCA's for hours
  > To: [log in to unmask]<mailto:[log in to unmask]>
  > 
  > Howdy folks,
  > I have an application where Circuit Card Assemblies are baked at 125 degree Celsius for 48 continuous hours (2 days), this is repeated a few times. No vibe or operating, etc just on a shelf, any thoughts?
  > Thanks Brad
  > 
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