Doug Pauls is one of the experts in conformal coating and I have no doubt that he knows how to use conformal coatings to protect against liquid water. He probably knows some tricks with conformal coating that I don't. I know some things he doesn't.

  On the TV programs where experts pick up poisonous snakes they always warn viewers "don't try this at home". The viewers who can ignore that warning know who they are.
  Alcohol clouds the judgment of some others. "I thought they were talking about live snakes and I thought this one was dead......".

  I know for a fact that some conformal coatings don't cure properly in cross sections greater than is recommended. I know of a few that will cure. There are some I'm not sure about including some silicone coatings. I worked with conformal coating every work day for 12 years.

  MIL, IPC and UL tests for conformal coatings are all done in moist chambers, not with liquid water. If the original purpose of conformal coatings was to protect against liquid water the  specs would include tests with liquid water.

  There's a need for water proofing coatings for PC boards. An industry wide committee should decide what properties are necessary, develop a qualifying test and maintain a QPL. Companies that don't have in-house conformal coating experts will benefit. Those that do might benefit from new materials developed to meet he spec.

  If some conformal coatings are good for water proofing they will pass the test and be sold as conformal coating and water proofing materials. Manufacturers might even tweak formulas to make a better material.

  I have witnessed 100s of instances where coaters "did their own thing" with had unexpected and undesirable consequences. It was partially the manufacturers fault for not demanding that customers follow their instructions.

  Doug's confident "he can do his own thing" with conformal coatings. I am too. The majority of engineers are not expert with conformal coating and should err on the side of caution.

  Edward Mines


Edward Mines BEChE, MEChE
238 Willard Dr.
Hewlett, NY  11557
516 205-6523

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