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For my project i would like to waterproof (or at least moistureproof) a PCB. The PCB is to be used without housing and during operation/handling there will be some skin contact (mainly hands).

Now i have read about different kinds of conformal coating like silicone or acrylic. I would like to go with silicone because most other coatings (including nail polish) tend to become brittle and chip off. Also i don't want to use things like resin because it is more difficult to apply and i may need to rework the PCB at some point.

The silicone conformal coatings i have found seem to do exactly what i need but i am concerned about the health of the users of the coated PCB (as well as my own health). I had a look at the safety data sheets of two silicone conformal coatings:

They seem to list quite some health risks (especially the 422B one).

  1. Are these risks mainly due to the solvents?
  2. Will the dangers go away/become negligible once the coating is cured?
  3. Are there any alternatives that i don't know about?
  4. Is there a better place to ask this question? If yes, where?
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    \$\begingroup\$ I'd find a contact for the manufacturers and ask them. I always advise against taking health advice from random people on the internet. Also, this is kind of off-topic for this site, though likely it is the solvents that are the toxic components. \$\endgroup\$
    – John D
    Dec 5, 2020 at 0:31
  • \$\begingroup\$ 422B : All the "Ingredients" listed in section 3.2 are called "Flammable liquid Category 2 or 3" and indeed like acetone, if there's any identifiable left, curing isn't complete. You need to take reasonable care using them : if I'm using acetone it'll be outdoors, using epoxy resin on my boat. So ... end product should be safe. But double check with the mfg's support to be sure. \$\endgroup\$ Dec 5, 2020 at 12:09

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Lukas, congrats on being thoughtful about safety. There is a family of silicone products that are safe for human contact -- they are 'platinum cure' formulations. It's not the only source, but I like Smooth-On products because they freely provide extensive technical information.

Some of their platinum-cure silicone products are used in theatrical prosthetics and adhesives that are painted directly onto the skin, while others are specifically for encapsulating electronic devices. Your options include "painting" on a coating, but you could also consider making a mold and encapsulating your PCB. In any case I don't think these will harm your PCB functionality as long as you're not using RF or wireless.

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I contacted both manufacturers (MG Chemicals and Electrolube).

Electrolube did not respond.

The response from MG Chemicals was as follows:

[...] Cured, the coating would not likely present a health concern for contact with the skin.

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  • \$\begingroup\$ Not accepting this as the answer because the response from MG Chemicals is, in my eyes, not satisfactory. It sounds like they don't expect it to be dangerous but don't want to be held responsible in case it turns out to be bad anyways... \$\endgroup\$
    – Lukas
    Jun 17, 2021 at 9:05

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