Author Topic: Waterproofing a controller board with marine sealant  (Read 500 times)

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Offline georgeecollinsTopic starter

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Waterproofing a controller board with marine sealant
« on: May 02, 2014, 11:14:21 AM »
I have been going through a lot of trouble to make an enclosure for a controller board waterproof.  I am using more and more marine sealant, a rubbery silicon goup that turns into something like solid rubber. 

I am wondering, if my board has all the connections needed for power, control and sensors attached to it via soldered wires, could I just cover the board with marine sealant?  In other words, just cover the whole thing in a rubbery substance?   I don't think the board gets very hot, but the voltage regulators may get a little hot.  Are there any other problems I am not thinking through? 

Thoughts?

Offline Billy

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Re: Waterproofing a controller board with marine sealant
« Reply #1 on: May 02, 2014, 11:44:04 AM »
You've already realized that heat dissipation will suffer, that is a large part of it.
Using something not intended for sealing electronics seems risky from a corrosion point of view.

Google conformal coating and potting compounds. There are plenty of materials intended to do what you're trying to do.

Offline jwatte

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Re: Waterproofing a controller board with marine sealant
« Reply #2 on: May 02, 2014, 07:58:08 PM »
How to seal electronics against water, according to my long-ago sailing experience:

1) Spray conformal coating on it.
2) Drench it in potting compound.
3) Put it in a clamshell with tight rubber gaskets.
4) Drill a hole in it for the water to come out through.

Really, water will get EVERYWHERE. Even if you think your cables are tightly sealed by the epoxy and sealant, water will work its way in the cracks through capillary action.

The best way to work it is to use multiple layers of boxing, that have enough gaps to let the water out, but are boxed such that a spray won't let the water in past the first box.

If you need to fully submerse it, build a submarine :-)

(Actually there are some people building battle ships in balsa that use steel balls for ammo, and they just pot all their electronics in similar silicone sealant, and it works for shorter periods of submersion just fine.)

Offline georgeecollinsTopic starter

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Re: Waterproofing a controller board with marine sealant
« Reply #3 on: May 09, 2014, 06:19:52 PM »
Thank you both, this is great advice to try conformal coating which I had actually never heard of.   

Offline Admin

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Re: Waterproofing a controller board with marine sealant
« Reply #4 on: May 16, 2014, 12:44:22 PM »
Some compounds corrode electronics. Look for 'electronics grade' RTV (or goop or whatever).

The advantage of using RTV is that it is removable if you change your mind about the circuit wiring.

Offline ootbrobo

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Re: Waterproofing a controller board with marine sealant
« Reply #5 on: June 19, 2014, 11:59:42 PM »
I'm Late to the party, but some other info to consider when potting electronics.

Potting electronics can be a bad idea if your electronics undergo significant temperature swings during operation.  As was said above heat dissipation is an issue, but you additionally need to consider thermal expansion.  Your electronics can cyclicly fatigue as a result.

Something I've learned the hard way is that electronic signals are not just dependent on the copper of your circuit board but the substrate.  When you pour compounds like potting materials, and hot glue onto electronics you mess with the E-fields.  If your circuit contains any higher speed signals (USB as an example) you can actually alter these signals enough to make them unusable.  The dielectric properties of your potting material should be a consideration.

 


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