Technetters, I have just come across a problem that maybe someone in more
tropical climes is familiar with.  A circuit board has been returned to us
from a client in Florida.   This board was spray coated with M.G. Chemicals
422A Silicone Conformal Coating and packaged in a die cast housing, with an
apparently leaky O-ring, and a small drain hole in the bottom and mounted on
the roof of a truck. Sometime in the last four months water got into the
housing, and with the heat, it must have been like a steam bath in there.
The conformal coating seems to have become spongy and absorbed the moisture.
Now the board appears white and under magnification the coating looks foamy.
It is also soft and flakes off the board very easily. Any idea why this
should happen? Shouldn't silicone be waterproof? What do I tell my customer?

     Regards Rod Lafond
     Manufacturing Engineering
     Aimtronics Corporation

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