Eric,

Why are you baking stuffed boards?  To remove moisture prior to conformal
coating?  We have been talking about baking bare PWBs here in order to
remove the moisture prior to processing (wave/reflow, in particular) as the
moisture in the board can cause the problem mentioned during a thermal
excursion.

-Steve


Steven K. Lustig
Process Engineer
EMS Technologies, Inc.
Norcross, GA
(770) 263-9200 x4714
[log in to unmask]


-----Original Message-----
From: Eric Kalgren [mailto:[log in to unmask]]
Sent: Thursday, October 14, 1999 11:46 AM
To: [log in to unmask]
Subject: Re: [TN] Board Delamination . . . Boards too old?!


Is everyone baking their boards with components stuffed or are you all
baking bare PCBs?  We currently bake stuffed PCAs for 6 hrs in a 150F
vaccuum oven.  If it sounds like a long time, well, it probably is.  We have
some experiments planned to see how long is long enough.  If anyone wants
results, contact me directly.  If anyone has suggestions as to how long
should be long enough, please don't hesitate to let me know [as if anyone
out there would!! :-)  ]

Eric Kalgren
BFGoodrich Aerospace
Data Systems Division
[log in to unmask]
(505) 938-5139

>>> Werner  Engelmaier <[log in to unmask]> 10/14/99 07:57AM >>>
Hi Steve,
Your root cause for the delaminations is moisture absorption, that is why
baking works. Boards subjected to high air humidity for a sufficient time
will fully saturate (at local ambient equilibrium). The time necessary will
primarily depend on the polymer involved and on the location of the P/G
planes.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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