Dear Technettors,

Have you ever heard that term?

We have been baking the Immersion/Flash gold PCB
because of the following theory:

During PCB making process, moisture, somehow, get
trapped underneath the solder mask.  Thus, in order to
get them out, the Immersion/Flash gold PCB need to be
baked for 2-3 hours at 200 degree C before SMT
process.  If PCB is not baked, during reflow in SMT
process, the moisture would find way to outgas at the
least resistance area.  If it is at the solderpaste
location, it would splash the solder paste and as it
drop down, there will be solder on gold-finger.

However, after they bake it, they use to leave the PCB
to open air environment (CA area) sometime for 1-2
days before SMT process.

Here are my questions:

1. Moisture trapped underneath the solder mask will
eventually outgas during reflow if it did not get
baked: IS THAT A MYTH OR FACT?

2. Does baking the PCB at 200C for 2-3 hours help to
reduce the outgassing problem (if it is fact).

3. After baking, by leaving the PCB to open air
environment, for about 24 hours, is it enough for the
moisture get back to where it was?

4. If there is really moisture trapped underneath the
solder mask, what are your reccommended solution?

Your help is greatly appreciated.

Stacy



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