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April 1999

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Subject:
From:
Bill Davis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 8 Apr 1999 15:25:22 -0700
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Bill-
I agree with Steve Gregory. If you had a history of moisture absorption
problems then I would. Bear in mind that polyimide generally saturates
at 3-5% water vapor at STP. Thus, even a factory floor at 50% RH will
allow for the poly-i to saturate eventually. Hopefully, your are getting
the boards dry-packed, and they are not opened from the dry pack until
just prior to stuffing. If you have the boards opened for any
appreciable time before stuffing (say 3-4 hours) then you may want to
orchestrate an experiment to see what, if any, difference there is in
defectivity between a newly opened package and one that's been sitting
out for a couple of hours. ANything longer than 8 hours I would
definitely bake.

> Bill Davis, Ph.D.
> Diamond Multimedia Systems
> Senior Scientist
> Tel. 408.325.7868
> Cell. 408.888.5650
> e-mail: [log in to unmask]
>
>


-----Original Message-----
From: Mengers, William D. [mailto:[log in to unmask]]
Sent: Thursday, April 08, 1999 1:02 PM
To: [log in to unmask]
Subject: [TN] Baking of polyimide boards


Guys (and girls),

Can anyone tell me whether or not polyimide boards need to be pre-baked
before processing thru nitrogen reflow for solder melt?  We are doing
it,
which of course means added expense.  Is it really necessary?  We bake
at
110 C for four hours.  Is there evidence which suggests that it is
necessary.

Thanks for any replies,

Bill Mengers
Northrop Grumman Corp.
Baltimore, Md.

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