Homebrew PCBs

Joaquim:  my experience with conformal coatings
in an industrial environment has led me to feel that
they are -worse- than bare board, unless you are
positive that they'll be totally sealed, and -stay-
that way.  I.e. only top-notch coatings designed
for the purpose.

I have had generic spray clear-coats not seal well
to the board because invisible flux-residue prevented
adhesion.  I've also had unpleasant surprises which
films cracking/crazing after a few years, or lift at the
edges, etc. etc..

When any of those things happen, moisture not only
enters under the film, but then wicks along the board;
lifting more film and leaving tracks of contamination
all over the place.

So choose a known-good compound, and be sure
your boards are -totally- clean prior to coating.

A lot of the coated commercial boards you see are
coated with Parylene, which is amazing stuff; but
must be applied in a vacuum chamber.  Not an easy
process to basement-adapt, unfortunately.

fyi, info on Parylene...

http://www.vp-scientific.com/parylene_properties.htm

Richard
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