No surprise. *ALL* conformal coatings are somewhat penetrable by
water (except maybe Parylene):
<
http://en.wikipedia.org/wiki/Conformal_coating>
<
http://www.conformalcoating.com> (Yech. The tech bull requires
registration)
<
http://www.conformalcoating.co.uk>
There are a mess of bulletins describing various failure mechanisms
under:
<
http://www.conformalcoating.co.uk/technicalbulletins.php>
<
http://www.conformalcoating.co.uk/FAQs.php>
However, they don't describe anything like you're experiencing. My
guess(tm) is that you have a wax coating, not acrylic, silicon, or
urethane. The wax has literally dissolved into mush from airborne
solvent attack. It may also have melted due to overheating. Difficult
to tell for sure without knowing the type of coating.
I used wax in the 1970's for marine radios. It worked well enough and
was easy to apply. The best part was that I could solder right
through the coating. If you want to remove the wax mess, just hit it
with a hot air gun and watch the wax drip off the board. Solvents
will also remove it. Then, just apply a new layer of wax and it's as
good as new.
Do you have a long wave UV lamp (i.e. black light or UV LED
flashlight)? Most PCB coatings have a phosphorescent die mixed in to
make it easy to inspect for gaps. Light it up and see if there's a
pattern. If you have large blank areas missing, it's a solvent
problem.
(Duz anyone know what happened to Dr. Barry L. Ornitz, who would
usually answer such chemistry questions? The last usenet posting I
could find was Nov 26, 2009).
--
Jeff Liebermann
[email protected]
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558