We still use humiseal. I put the board in the upper steering column of a machine that should be safe from spray but pressure washing ruined that illusion. Yes, next rev will have it in a nice sealed box, but I need to ship out some PCBs to current users to prevent any accidents. So we are trying different coatings. I think we may use some UV cure stuff. It doesn’t heat, one of the reasons I went with MOSFETs. So airflow is probably not a consideration.
Best Regards, Chuck McCown McCown Technology Corporation 8401 N Commerce Dr Lake Point, Utah 84074 801-250-9503 Office 435-830-4306 Cell www.mccowntech.com www.microtrench.pro www.terabitnetworks.com From: Ken Hohhof Sent: Monday, September 9, 2024 4:53 PM To: [email protected] Subject: Re: [AFMUG] OT question for the borg Wow, I haven't dealt with conformal coating for almost 50 years. I remember using a product called HumiSeal. There's spray, dip, air cure, other curing methods. Thin, thick. Hard to makw a universal statement. My impression though it was intended for humidity or condensation, not spray or submersion. My personal preference would be to put the circuit board in a NEMA4 enclosure and use conformal coating for belt and suspenders. Is there a reason like airflow you can't put it in a waterproof box? ---- Original Message ---- From: [email protected] Sent: 9/9/2024 5:22:44 PM To: [email protected] Subject: [AFMUG] OT question for the borg I have a motion control PCB that runs some hydraulic valves via pwm in one of my products. We discovered that a drop of water on the right place on the PCB will turn on a MOSFET causing uncommanded movement of the system. The argument around here is potting vs conformal coating. The boards that were exposed to water via pressure washing operations DID have conformal coating on them but some how the water still turned on the transistors. I had the P channel depletion MOSFETS pulled up with a 10K resistor. We changed that to a 680 ohm and it made it much less likely to get turned on with water droplets. But it is not perfect. Needs physical protection too. I am of the opinion that a good thick layer of conformal coating is just as good as potting and much less work. Opinions? -------------------------------------------------------------------------------- -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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