Conformal Coating a Gen3 Device

For those that use conformal coating… is there any tips/tricks on conformal Coating a Gen3 device such as a Boron? I had a few specific questions. There are several different mentions of conformal Coating in old topics but typically was a side comment. Rather than replying to several of them I thought I’d start a new topic:

  1. Is it easier/better to spray on or brush on? If one or the other, what product have you used?
  2. Can I conformally coat the reset/mode pushbutton and have the buttons still function or does that need to be masked out somehow?
  3. Do I need to try and get conformal coating under the “tin”? The one on the top I’d assume no, but the tin on the underside of the Boron has a decent gap all the way around it. Should I use some sort of electronics RTV Silicon to try and fill the larger gap in the tin or don’t worry about it?
  4. Are there any tips/tricks to applying conformal coating?

As of now, I plan on the following steps:

  1. Use spare headers to plug the Boron into and protect the pins
  2. Use a spare USB cable OR possibly a micro USB dust cover to protect the USB port
  3. Use a dap of Hot Glue over the JTAG/SWD connector. Should be removeable if I ever need to in the future.
  4. I do not use an external SIM so I’d likely spray right over that.
  5. I’d insert a spare JST-PH connector into the battery connector. Although the battery connector is on the carrier board, you never know in the future.
  6. Mask the Cellular Antenna connector with tape or just clip on the final antenna with the intent to not remove it again after conformal coating.
  7. Spray MG Chemicals Modified Conformal Coating on via Aerosol can. Let dry, Flip it over and repeat.

As of now, these boards go into a weatherproof Polycase enclosure with connectors being IP67. These enclosures are then in the outdoors and so I have some concerns of condensation and humidity entering. I’ve used the Goretex vent in the past with pretty good success but still would like the added protection of Conformal Coating to maximize longevity.

For anyone who’s conformally coated a Gen3 Device your guidance is appreciated!
Tagging a few community members who made reference to conformal coating in prior posts:
@Rftop
@mikemoy
@hwestbrook

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The only product that I have experience with is:

Think of it as a bottle of nail polish.
I don’t attempt to be very precise when applying with the little brush.

I cant recommend the liquid over the spay because I’ve never used the spray.
But I don’t mask off any parts when using the liquid.

My theory was “Anything metal that’s not coated will corrode and try to kill the device”, so I’m very liberal with the application.

I have Electrons still in outdoor service after many years with no apparent problems (haven’t seen them, but they are still operating). A few are still on 0.8 firmware.

As for your Gen3 question specifically, I haven’t deployed any Borons for long-term/permanent outdoor service due to the firmware issues. Maybe it’s time for another Validation Trial attempt ?

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I’ve used clear nail polish when needed, I live on the Florida gulf coast so corrosion is a big issue. If you need to do a lot of them I don’t think I would use it, but it’s been perfect for my use.

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Thanks @Rftop and @Mjones I have both the MG Chemicals brush on as well as the spray on. I also have two dead borons due to early firmware issues causing them to brick (Particle was nice enough to send me replacements). So I’ll use these two as my test dummies one for each method. I’ll try and take some pictures on the process I use and report back here on my observations, recommendation and any tricks I learn along the way.

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