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Conformal Coating Recommendation for Radio Board

Conformal Coating Recommendation for Radio Board

Conformal Coating Recommendation for Radio Board

(OP)
Hello,

I'm looking to increase moisture resistance in a radio circuit board and have been tasked with finding a suitable conformal coating. Initial research/design parameters say that I need to find something with a high dielectric strength so I don't impede the radio signal once coated. Does anyone here have experience with such a use case? I'm looking at Loctite 3900 as it has "high" dielectric strength but would like to compare to some other coatings/get advice.

Thanks!

RE: Conformal Coating Recommendation for Radio Board

Dowsil 734 is a flowable silicone if you want a more flexible option.

RE: Conformal Coating Recommendation for Radio Board

Perhaps you mean low dielectric constant. Dielectric strength means something else entirely and should not really affect a radio signal.

RE: Conformal Coating Recommendation for Radio Board

What is the frequency of said radio? At higher frequencies (say, 5GHz+), coatings can/will have a major effect on power output, noise levels, etc. Even the PCB's soldermask has an effect, which only increases with frequency.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Conformal Coating Recommendation for Radio Board

Of multiple available conformal coatings we have looked at, the gold standard for moisture resistance is parylene. Not sure how it stacks up to radio frequency devices, but it has the best (lowest) permeability and moisture absorbtion, compared to silicone, acrylic, epoxy and urethane coatings. It is typically applied as an out-of-house operation unless you want to spend a lot more money compared to the others, but you get what you pay for. Oh, and of all of them, silicone is the worst at providing moisture protection.

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