Thanks for the reference
Ryan Grant
> -----Original Message-----
> From: Kelly M. Schriver [SMTP:[log in to unmask]]
> Sent: Monday, January 04, 1999 7:50 PM
> To: [log in to unmask]
> Subject: Re: [TN] Baking of boards
>
> Ryan -
>
> An additional note - Charles S. (Stu) Leech can be reached at
> [log in to unmask] - they have done a considerable amount of additional
> work since the publication that Dave refers to.
>
>
> Regards - Kelly
>
> -----Original Message-----
> From: David Hillman <[log in to unmask]>
> To: [log in to unmask] <[log in to unmask]>
> Date: Friday, June 02, 2000 8:58 AM
> Subject: Re: [TN] Baking of boards
>
>
> >Hi Ryan! Get a copy of the following article: "Removing Moisture from
> >Electronic Components and Assemblies", authored by Charles S. Leech, JR.
> ,
> >Circuits Assembly May 1994, it covers some of the basic physics of water
> >loss in detail - especially the issue of vacuum moisture removal. In the
> >article the vaporization of water via vacuum is discussed as not being
> the
> >most effective moisture removal method in all instances - the change of
> >physical states (liquid to vapor) can result in the formation of ice (the
> >article describes a neat demonstration of this reaction) which impedes
> the
> >removal of water from a board. I participated in a DOE in which we showed
> >that a standard baking procedure in a convection oven was more effective
> >than a vacuum bake process. However, you don't get anything for free -
> the
> >convection bake process degraded the board solderability much more the
> >vacuum bake process . Good Luck.
> >
> >Dave Hillman
> >Rockwell Collins
> >[log in to unmask]
> >
> >
> >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]
> >
> >
> >
> >>
> >> 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.
> >>
> >
> >>
> >>
> >> 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
> >
> >##############################################################
> >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> >##############################################################
> >To subscribe/unsubscribe, send a message to [log in to unmask] with
> following
> text in
> >the body:
> >To subscribe: SUBSCRIBE TECHNET <your full name>
> >To unsubscribe: SIGNOFF TECHNET
> >##############################################################
> >Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> >information.
> >If you need assistance - contact Keach Sasamori at [log in to unmask] or
> >847-509-9700 ext.5315
> >##############################################################
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in
> the body:
> To subscribe: SUBSCRIBE TECHNET <your full name>
> To unsubscribe: SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> information.
> If you need assistance - contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
> ##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
|
