Urethane and parylene have the best long term humidity resistance of the conformal coatings. Since yer not hep about urethane, try the parylene [http://www.paratronix.com/apps/, http://www.paryleneinc.com/, http://www.parylene.com/, http://www.scscookson.com/parylene/, etc]. It will absorb less than 0.1%. And since they are vapor deposited, parylenes are noted for their ability to penetrate small spaces, probably overcoming the voiding limitation you see in urethanes. On the other hand, the process will give you incentive to get it correct the first time. [Ummm, now that sounds scary!!!] Yer gunna need a chain saw to cut through the stuff!!!
What�s your thinking on encapsulation as an alternative to parylene and still attaining a less-hermetic conformal coating? [It�s something to consider, because in real life, it�s going tough to distinguish a parylene from encapsulation.] Master Bond [and probably others] has a reworkable encapsulant. Beyond that, I know nothing about it. [Just got the flyer tonight.]
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