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I plan on building and installing a small computer in my car for multimedia purposes. Since the only space I have for it is under the passenger seat and since the temperatures vary between -20 to 35+ over the year, I am worried about condensation and any damage it might cause.

My first thought was to use a sealed case but not only they're expensive, they're physically too large as well. Since I can't prevent condensation, my only option is to decrease the likelihood of it causing any damage. I noticed that other electrical components in the car (radio, amp, etc) are conformally coated and I thought I might do the same. Hence, my question.

I read that such a coating could change the impedance of the PCB tracks or that it would hurt heat dissipation. As such, I am interested in knowing what components on a motherboard are safe to coat and how bad can these effects actually be?

For reference, the board I will use is an ASRock Fatal1ty B450 Gaming-ITX/ac, which, as far as I can tell, uses heatsinks for the chipset and the VRM.

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You can use a high viscosity liquid coating and selectively pour it on.
You can also use a low viscosity spray coating and spray it on like paint.
Most of the coatings have an UV tracer to check coverage.

Things to avoid are obvious, the socket and connectors. Less obvious are heatsinks, since painting those would be insulating them.

Also when you remove heatinsks you shouldn't coat thermal interface surfaces.

And do not underestimate the capillary action of the coating! Under the socket/dimm slots for example.

It it unclear what you want to do with the system, but I'd recommend looking for a passive cooled sealed unit, this ibase ags100 for example.
I think, in overall price, you'll be in the same range.

The coating has a small effect on package to ambient thermals for normal components or traces. Poor (too thick) spray application may change the impedance or even fail in high voltage tests due to poor dying/capturing moisture. Spray coatings protect against high humidity, pour coatings also provide mechanical rigidity.

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  • \$\begingroup\$ So removing heatsinks, masking all thermal interfaces, ports, pins and sockets/slots. Should I leave the ram and CPU in and mask them? \$\endgroup\$
    – user1969903
    Commented Aug 17, 2020 at 8:47
  • \$\begingroup\$ The idea being that if the coating reaches those areas through capillary action, the pads/pins of the CPU and RAM are already making contact so hopefully they will themselves act as masks at the contact points and prevent electrical discontinuity. Also, what about transistors or other such SMD devices, as well as the tracks? I'm not sure how the coating would affect the tracks since they are already masked by the soldermask, but what of the SMD pads? \$\endgroup\$
    – user1969903
    Commented Aug 17, 2020 at 9:04
  • \$\begingroup\$ @user1969903 in terms of application, disconnect and mask all connectors with mold putty or tape. Seal the edges of pci and dimms with electronics compatible silicone kit from a syringe. And apply spray very thin, multiple times with drying in between. Overall effectiveness may be limited due to non gold plated connectors. Don't forget the bottom. \$\endgroup\$
    – Jeroen3
    Commented Aug 17, 2020 at 11:52
  • \$\begingroup\$ I ended up masking everything that was physically feasible (caps, inductors and the top of all SMD components larger than a few mm, including the power mosfets). I used a conformal coating which can be removed with acetone, just in case, and I am happy to say that after applying four layers, rotating the board 90 degrees after each coat, not only is my motherboard very funky looking under UV light, but the temps are normal both under idle and full load conditions and it's been running for a few days now. \$\endgroup\$
    – user1969903
    Commented Aug 29, 2020 at 19:02
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you can look at the nanocoatings available on the market. You may need to apply more layers for longer lasting IP68 effect. Once applied it should be submersible in water without problems (depending on the voltage used I guess ask advice from the supplier). Good luck !

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  • \$\begingroup\$ Thanks for the suggestion, but the coating you mention isn't readily available in my region, whereas conformal coatings can be picked up at local electronics store. \$\endgroup\$
    – user1969903
    Commented Aug 29, 2020 at 19:03

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