Homebrew PCBs

Hi list,
I need advice about conformal coating materials to protect the board 
from harsh environments.
I like a matte finish on my boards, not  the  brilliant  stuff.
Any advice please ?

Thanks in advance

Joaquim

Hi Joaquim:
  
  It depends on how you want the board to look. I've used 'Tool Dip', in  the spray can, on some boards that spent a summer underground in an  irrigated field. They were in non waterproof cases. We had no problems  with moisture.
  
  Tool Dip is like the material on insolated pliers. You can get it at hardware stores.
  
  Chuck

Joaquim Boavida <jboavida@multidigital.com> wrote:  Hi list,
I need advice about conformal coating materials to protect the board 
from harsh environments.
I like a matte finish on my boards, not  the  brilliant  stuff.
Any advice please ?

Thanks in advance

Joaquim


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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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