O.K. Doug and Ron, I'm going to put you an the spot.

        Two weeks ago, I set up an experiment to see how long I would have
to vacuum to get some PBGA's dry.  The vacuum drying was run in parallel
with 125?C bake and just air drying (20% RH here in the high desert).  The
vacuum drying didn't do much better than air drying.

        The part were supersaturated with water, and the experiment only ran
for 24 hours.  But projecting the desorption of the moisture, it would have
taken a week to dry them, compared to 24 hours with the bake.

        The vacuum was done with our plasma etcher at 0.5 torr (no plasma),
so I fear that I may have frozen the moisture in the component.  Any ideas
as to why the moisture didn't come out?  In theory, vacuum should work!

Thanks

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Dieselberg, Ron [SMTP:[log in to unmask]]
> Sent: Thursday, June 01, 2000 7:44 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Baking of boards
>
> I agree with that, Doug. For many years we have vacuum baked all of our
> boards. It helps even more if you back-fill with dry Nitrogen as we do.
> Ron Dieselberg
> BAE SYSTEMS
> Cincinnati Electronics Corp.
>
> -----Original Message-----
> From: Douglas Pauls [mailto:[log in to unmask]]
> Sent: Thursday, June 01, 2000 09:05
> To: [log in to unmask]
> Subject: Re: [TN] Baking of boards
>
>
> If you are really concerned about the effects of heat on the polymer
> qualities or the oxidation of the surfaces, consider using a vacuum or
> vacuum-make operation.  Gets the water out with less heat.
>
> Doug Pauls
>
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