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I'm designing a PCB that will be installed in an IP65 plastic case. The device will be installed in multiple scenarios and regions (indoors, outdoors, high/lo temperatures, high/lo humidity etc). The device is a BLE SoC with a relay and is is directly connected to the mains (the device has a 3W power supply on the PCB). The device will be installed in a fixed place and should last for at leat 10 years without maintenance.

I would like to know if it is necessary to apply conformal coating, potting or any type of resin to protect the device from possible condensation or, as the PCB is inside a plastic IP65 case, it is not necessary.

In case it is necessary, which conformal coating, potting or resin would be suitable for this application?

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  • \$\begingroup\$ Conformal coating should be minimum protection for condensation I would say. Just make sure you do testing to verify that the coating do not crack under the worst case humidity condition to be expected after several worst case thermal cycling. \$\endgroup\$ Jan 7 '21 at 10:59
  • \$\begingroup\$ @AntonIngemarson Thank you. The question here is if, by placing the PCB inside an IP65 case, it is necessary to apply any type of conformal coating or similar or not \$\endgroup\$
    – LazyTurtle
    Jan 7 '21 at 11:06
  • \$\begingroup\$ Quite relevant. \$\endgroup\$
    – Andy aka
    Jan 7 '21 at 11:49
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If the enclosure has any penetration or mating surface, it will ‘breathe’ due to the change of temperature and pressure. IP65 is not hermetically sealed. Depending on your application, you could use a breather, desiccant or conformal coating. Also consider corrosion of metal items in the enclosure. Also consider the effects of the conformal coating to your RF sections in terms of dielectric and the possibility of shrinkage putting stress upon components - especially with RF.

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  • \$\begingroup\$ Thank you. Regarding this answer...even if the inside of the device is always several degrees (3 or 5 ºC) above outside temperatue, would it be necessary? How can condensation be created if the internal temperature is always above the exterior? \$\endgroup\$
    – LazyTurtle
    Jan 7 '21 at 13:09
  • \$\begingroup\$ Heaters are another technique to minimise condensation. I used this in an instrumentation enclosure that had a LCD and glass window. \$\endgroup\$
    – Kartman
    Jan 7 '21 at 13:13
  • \$\begingroup\$ So, if we confirm the inside of the enclosure is always several degrees celsius over the outside temperature, can we confirm there will be no condensation? \$\endgroup\$
    – LazyTurtle
    Jan 7 '21 at 14:26
  • \$\begingroup\$ Condensation happens if the relative humidity raises above a certain level, which in turn can happen when the temperature drops and the absolute humidity stays the same. So expect condensation when temperatures drops at night. \$\endgroup\$
    – Codo
    Jan 7 '21 at 17:07
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If there is no vibration It is not necessary, the box will protect! In addition, is there a possibility of generating heat? It should be considered as the resin will isolate and not dissipate.

If there is harmful vibration and you have no problem copying your circuit, use epoxy resins suitable for electronics with SHORE A <50 hardness it is easy to open to fix it in case of any problem.

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  • \$\begingroup\$ No vibration expected. No poissibility of generating heat. With an IP65 enclosure ther's no need of adding conformal coating or similar to protect from condensation moisture? \$\endgroup\$
    – LazyTurtle
    Jan 7 '21 at 11:27
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    \$\begingroup\$ No the box won't protect! \$\endgroup\$
    – Andy aka
    Jan 7 '21 at 11:50
  • \$\begingroup\$ If it can be guaranteed that the enclosure seals hermetically considering all environmental conditions you still need potting material, laquer the PCB or conformal coating because condensation also happens inside a sealed enclosure. Again if you can guarantee that the housing is completely sealed it may also suffice to put silica gel inside the housing or assemble the component in controlled environment with low humidty. \$\endgroup\$
    – Jogitech
    Jan 7 '21 at 11:56

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