Richard,

What you are saying is true, but the moisture that is quickly absorbed back into the
board is initially near the surface of the board, and not likely to create
delamination.  It is the moisture which is deep in the board that can become trapped
and build up the required pressure to cause a delam.  This is also true to some degree
for components.  Your concerns about baking are also true.  You can bake a board or
component and cause/increase a solder joint problem.

Conformal coat:  Most conformal coats do not form a barrier to water vapor.  They do
not "seal" the moisture in or out.

How much advantage there is in baking parts is probably related to the Relative
Humidity of the enviroment the parts are stored in, and come into equilibrium with.  I
would expect differing results between southern California and Florida.

George Franck
" my Opinions are Just that."

Richard Tilbrook wrote:

> Steve,
> If you vacuum oven your boards (boiling off and evacuating any moisture),
> then open them into an environment, perhaps 22deg.C and 60%RH, won't the
> boards quickly absorb the moisture in that environment? If you then
> manufacture the boards, then ATE and inspect them, then conformal coat /
> dip them, you'll be sealing moisture in.
>
> I only ask because I am researching into moisture sensitive components,
> and one of the options is to put the components into a vacuum (oven /
> chamber).
>
> I am concerned that putting non-hermetically sealed electronics
> components (boards or devices) into a vacuum oven leads to little or no
> advantage, and only the acceleration of intermetallic formations between
> copper and tinned layer as a result.
>
> My question (finally) is would this be the case? Or would the rate of
> absorption be so slow that it wouldn't really matter?
>
> Regards,
>
> Richard Tilbrook
>
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