Dale,
How high is "up"?
What you're asking for is somewhat subjective, as your responses will most
likely be. I don't know of any written standard regarding "moisture
entrapment", what you will most likely receive are guidelines and
recommendations.
Our customers have a diverse range of criteria they follow. While some
pre-bake boards only weeks old, others don't bake at all, some store theirs
in controlled environments thus minimizing the need for baking, others
unwrap them from the packaging we ship them in, and allow them to remain
unprotected in cardboard containers until use...whenever that may be...
So to answer your question, perhaps you should ask the end users out there,
what they recommend in regards to pre-baking boards that are packaged as
your board shop provides them, and how you store them...this might provide
more meaningful information...
If all else fails, take a few boards and perform your own experiment, take a
few boards home with you and leave it in your bathroom where you shower, for
a few days, then bake 1 around 200F for an hour, another at 1.5 - 2.0 hours,
3.0 -4.0 hours, etc etc soldering the boards as you move along until you
reach a time and temperature you're satisfied with...just one method...
Good luck,
Franklin
----- Original Message -----
From: "Dale Ritzen" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, February 11, 2003 1:51 PM
Subject: [TN] Moisture in Raw Boards
> I, and our board suppliers, have looked through IPC-6011, 6012, 600, 610
and
> most of the other pertinent standards and cannot find an answer to this
> question:
>
> How long should multi-layer printed circuit boards be left out in a
> controlled ambient environment (standard factory temp/humidity) before
> pre-baking the boards becomes necessary to dry out any accumulated
moisture
> in them? We would like to minimize potential board delamination due to
> trapped moisture in the FR4 or polyamide layers (which can expand rapidly
> when the board is placed through a reflow oven or solder wave).
>
> Does anyone want to wade in on this one? We have identified a standard for
> pre-baking IC components before use in this type of high-heat environment,
> but cannot find any standard or specification pertaining directly to PCBs
> themselves. I suspect it will have to take into account the material used,
> number of layers, the definition of "standard factory temp/humidity" and
> other things related to the board and the environment it is stored in
prior
> to use.
>
> Any help in this regard would be appreciated.
>
> Thanks!
> Dale Ritzen
> Quality Manager
> Austin Manufacturing Services
> 9715A Burnet Road, Suite 500
> Austin, TX 78758
>
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