This is another responce to the outgassing problem. You could also buy an
outgassing test kit if you would like. It is L39.95.

There is a time for fibre glass boards but this is only a guide which is based
on material. All boards are different sizes, different shapes and have different
builds. Using one baking rule for all board will inevitably cause some boards to
be baked for to long a time. The more you bake boards or components at elevated
temperatures the more it effects solderability on the surface of the plating. It
will also effect the intermetalic layer if the solder coating is thin and cause
dewetting. Care should be taken with both duroids and polyamide if a
electroplated tin lead is being used as this will not normally be fused and more
likely to degrade during baking. In cases where gold over nickel is used if the
gold is thin the nickel will oxidise and become unsolderable. What you need to
do is obtain samples of each of you board families made from the different
materials. They need to be baked to remove all the moisture after first
accurately weighing them. They are then left in a normal environment constantly
monitoring the change in weight (g's) for each material say every couple of
hours. The weight will then stabilise close to the original reading. A further
consideration would be to place the sample boards in a known environment of RH
and temperature and conduct the test. This would allow you to establish the
correct temperature and bake times for any product. This basic draft procedure
will also provide you with the time for moisture to be reabsorbed. As I have
said in the past there is only one reason a professional company, like your own,
to be baking and that is to stop delamination. Remember that moisture in the
board will produce the energy during soldering to cause board failure but it is
not always the root cause. In most cases there are voids in the board to start
with and that is where the moisture can accumulate. Boards which tend to out gas
during soldering is controlled by your specification and supplier not by
moisture content. After first establishing the bake time and temperature you
should also consider the oven you are going to use. What is the effect of the
board loading on time to temperature and air circulation. I have worked in some
companies that the oven never got to the true temperature due to loading and
circulation effects. I hope this is helpful. If you need some one to conduct the
tests for you and produce the time temperature graphs for different materials
then let me know.

Bob Willis UK
Tel 01245 351502
Fax 01245 496123