Unless there is a special requirement or there is something known, wrong
with the board (it got wet, stored improperly, etc) I have never baked
boards prior to wave soldering, including multilayer boards.   This is an
extra step in your process and only adds cost to the product.

You should specifiy to your board vendor that boards are to be shipped in
sealed packages (25 bds seems to be a common number among my vendors).
Adding a dessicant to the carton, or within each package is an option.  We
require a dessicant if the boards come from overseas.  When the boards are
stored at your facility, always re-seal packages if the entire pack is not
used.   Some companies have a controlled storage area for bare PCB's.   At
our facility, we issue the production lots in quantities that match the
package size (i.e. 500, 1000, etc.).  Sealed packages are distributed to
the production floor, and the pack is not opened until loaded on the
machine.





[log in to unmask] on 11/27/97 02:03:00 PM

Please respond to [log in to unmask]; Please respond to
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To:   [log in to unmask]
cc:    (bcc: Ed Holton/Hella North America Inc.)
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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