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Reading through What's the best way to protect a board from corrosion in a hot/moist environment? it has specific advice for a board/project that will be used in a harsh environment.

How important is sealing a board for use in a normal or even a kind environment?

Do people assembling DYI kits generally worry about it?

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Do hobbyists worry about it? Heck no. At best I might put a clearcoat on a homemade PCB to keep the copper from oxidizing (looks bad, but that's it). Some people at large companies don't even worry about it. I've put unsealed professionally made boards in test equipment that's being used in a factory floor environment. In fact I'd say boards aren't typically sealed or protected at all unless they're going into an environment that's known to be difficult. This might include engine controllers (grease, carbon deposits), anything going on a ship (salt spray, salt fog), any overly dusty area - particularly metal particles I'd imagine.

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    \$\begingroup\$ and it will be coated if the board specifically is very sensitive to changes in electrical properties. For example, the grease from your hand over time will oxidize to form a mildly conductive coating, if your board is sensitive to leakage current or is doing coulomb counting this can cause an increases error from someone touching it. \$\endgroup\$ – Kortuk May 15 '11 at 0:43
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    \$\begingroup\$ Any medical devices that touch the patient will also usually be coated, for much the same reasons Kortuk mentioned - you really don't want your leakage current to change over time on an EEG monitor! \$\endgroup\$ – Michael Kohne May 15 '11 at 1:18
  • \$\begingroup\$ Depends on the case as well. If you're certain your case is completely IP67 rated and tested, it may seem unnecessary to protect your boards. \$\endgroup\$ – Hans May 15 '11 at 8:11
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Here are some reasons NOT to coat your board:

  • the coating will thermally insulate the board. Components that need to dissipate heat, like voltage regulators and PTC's, won't work as well, or may fail sooner.
  • The coated board is harder to modify. If this is a prototype, or other DIY project, you probably do want to have the option of making changes later.
  • The kind of coatings that will actually protect the board from a harsh environment without running the risk of trapping undesirable material against the board (doing more harm than good) aren't terribly cheap. A good coating may represent a substantial fraction of the total cost.
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  • \$\begingroup\$ The coating process is expensive. But most of the cost comes from the labour of masking the connectors rather than the coating material itself. \$\endgroup\$ – Martin May 17 '11 at 8:09

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