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December 2001

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Subject:
From:
David Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 18 Dec 2001 15:57:06 -0600
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Hi Kathie! Sorry for a silly question but why are you baking the boards?
Material reason, process reason, etc. ?

Dave Hillman
Rockwell Collins
[log in to unmask]




"Lambert, Katherine A." <[log in to unmask]>@ipc.org> on
12/18/2001 09:35:58 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>

Sent by:  TechNet <[log in to unmask]>


To:   [log in to unmask]
cc:

Subject:  [TN] Board baking & sealable bags


Hi folks,

Currently we bake our boards and store them in nitrogen cabinets until we
are ready to use the boards on our automated line.  Typically, turn around
is fairly quick - within a week - but occasionally is more than a month due
to other part shortages.

We are trying to streamline the process a bit and get rid of the nitrogen
cabinets as they take up a lot of space, and the boards become separated
from the rest of the kit, etc.

We are looking at a bake & bag process.  We would bake the boards, seal
them
in appropriate bags with a humidity indicator card, and send them to the
assembly area with the rest of the kit.  Desiccants are not an option as
they typically have caused our panelized boards to break.  We have a
variety
of board types - polyimide, epoxy-glass, etc.  Since the folks around here
like a one-size-fits-all process, we need to develop the process around the
most sensitive board type.

Now for the questions:
1. Where is a good source for information regarding sealable or resealable
bags that are reasonably impermeable to ambient humidity?  Our relative
humidity levels typically run between 30% & 50%
2. We have a bag sealer, but will a zip-lock type bag work just as well?
3. Where is a good source for information regarding humidity indicator
cards?
4. Is there any reliable information regarding how long a baked board can
be
exposed to ambient humidity before it has to be rebaked?

Thanks for any insight you can provide.

Kathie Lambert
Process Engineer
Northrop Grumman
Baltimore, MD
410-765-9746

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