Richard,
I am assuming you are talking about traditional FR-4.  We have not had
to preheat PCBs since 1990, when we were dealing with a particular far
eastern supplier.  Since then that company has pulled up its socks and
manufactures a better product, stores the boards properly, maintains a
minimal stock, packs them properly and gets them to us faster than the
proverbial slow boat.  We have never had problems in my eight years in
the industry with suppliers like Via Systems, Hadco, etc.

Its been so long ago I can't remember the conditions we used, and I
don't want to!  I would change suppliers before I went back to heating
boards.

Bev Christian
Nortel
613-967-5407

>----------
>From:  Blanchet,Richard[SMTP:[log in to unmask]]
>Sent:  Thursday, November 27, 1997 2:03 PM
>To:    [log in to unmask]
>Subject:       [TN] Assy: Pre-heating of PCBs
>
>Hi,
>
>I'd like to get your input on pre-heating PCBs in an oven before wave
>soldering. Do you do it ?  On all your PCBs or only on multilayer ones ?
> For how long and at what temperature ?
>Aside from humidity that can be entraped and suddenly released, thus
>creating delamination, what other problems may some one face if they don't
>pre-heat their PCBs in an oven before wave soldering ?
>
>Thank you.
>
>Richard Blanchet
>Manufacturing Engineer
>Canadian Marconi Company
>
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