Dewey,

Here at Space Systems in Florida, we have an in-house soldering process
spec. that requires vacuum bake at least 4 days (96 hrs) prior to wave
soldering.  It is intended for Polyimide boards.  The time window was
established from test data that showed how fast moisture is re-absorbed
after bake-out.  We have not had problems with using this relatively large
window.

R. G. Blomberg
Honeywell - Space Systems
Staff Production Engineer
(727) 539-5534 voice
727-539-4469 Fax
[log in to unmask]

-----Original Message-----
From: Dewey Whittaker [mailto:[log in to unmask]]
Sent: Tuesday, March 21, 2000 5:09 PM
To: [log in to unmask]
Subject: Re: [TN] Baking FR4 boards


Alain Savard wrote:

Isn't the 72 hours before bake a requirement for polyimide instead of FR4?

Alain Savard, B.Sc.
Chemical Process Analyst
CAE Electronics Ltd.
e-mail: [log in to unmask]


-----Original Message-----
From: Dewey Whittaker
1. Typically, for multi-layer (6-8 layers), FR4, SMT boards stored in an air



conditioned environment at about 50+/- 10% RH, how many months would you
allow
to pass before you would recommend baking them prior to reflow?
2. What would be your bake cycle?
Thanks,
Charlie B.
####################################
Without knowing any other variables and being conservative,72 hours is your
window for the Aerospace Industry.
Dewey
--
Dewey Whittaker


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If it were Polyimide,it would be 24 hours(realistically 8 hours).Through
testing and proper storage conditions,each design could have a much greater
processing window.4 hours at 100 degrees C. is the bake.
Dewey
--

Dewey Whittaker

Honeywell -- Air Transport Systems Division

US Mail: P.O. Box 21111 MS: M16A2 Phoenix AZ 85036

Phone: +1 602 436 436-2766

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