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Does IP67 box protect PCB from moisture?

If not, is it OK to have an outdoor air humidity sensor soldered on PCB in IP67 housing?

Also if it doesn't block moisture, is there any reason to use IP65/IP66/IP67 housing, if there isn't chance for water to directly come inside box?

Thank you.

Edit: It's a weight scale, it only works few seconds per day so there isn't heating inside the box.

SamGibson
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user3613833
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  • [Related question and answer](https://electronics.stackexchange.com/questions/388866/moisture-trapped-in-ip66-enclosure?rq=1). – Andy aka Dec 22 '18 at 10:03

2 Answers2

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If you are concerned about condensation and corrosion then IP67 will not prevent this. However it is possible for the reduce the issues with desiccants or back filling with dry nitrogen in a sealed case.

For your environment without force water ingress, your don't need IP6x yet it is possible to have thermal shifts that induce condensation.

It will be necessary to evaluate non corrosive exposed conductors and/or use a conformal coating or forced air circulation such that metal case temp matches the inside air temp or perhaps use a thermal insulative plastic coating on the interior to avoid the internal air temp gradient.

So some specifications for thermal shock and design work needs to be done on the enclosure to prevent corrosion from condensation and consider floor cleaning use of water.

Tony Stewart EE75
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    Hi, thank you for your answer. So nothing can stop outside moisture to go into sealed box. Still didn't decide should I go with IP6X + silica gel, or just regular box with drain on bottom and make a tilted PCB inside. I'm also worried how would moisture affect on my measured data. I'm trying to measure small voltage difference up to 500 nV, so I think that even small condensation can affect my measured data. Thanks – user3613833 Dec 23 '18 at 17:36
  • Thermal insulation prevents condensation. But also causes temp rise. – Tony Stewart EE75 Dec 23 '18 at 22:09
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IP 67 will keep minor floods out for half an hour.

condensation comes out of the air, it enters the box as water vapor, not as liquid water.

some capacitors emit a small amount of water vapour as they age, so you probably want to put a dessicant in a sealed box, or to vent the bottom end of a conduit to allow the box to breathe

Jasen Слава Україні
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    A vent/drain port is *definitely* recommended -- not only will it provide an exit path for condensation (vs. using a dessicant, which will lose effectiveness over time), it will allow pressures inside the enclosure to equalize with the ambient air pressure, which minimizes the pressure difference that drives water/contaminants across the enclosure seals. – ThreePhaseEel Dec 22 '18 at 17:24
  • Hi, thank you for your answer. So nothing can stop outside moisture to go into sealed box. Still didn't decide should I go with IP6X + silica gel, or just regular box with drain on bottom and make a tilted PCB inside. I'm also worried how would moisture affect on my measured data. I'm trying to measure small voltage difference up to 500 nV, so I think that even small condensation can affect my measured data. Thanks – user3613833 Dec 23 '18 at 17:39
  • a conformal coating can keep your circuit dry. warming the box can help drive condensation out too. if you can vent to somewhere dry that will also help. – Jasen Слава Україні Apr 21 '21 at 20:58