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In order to completely waterproof some basic electronic circuits, I've often used potting epoxy to stop anything getting to the internals.

However, this has mainly been with stuff using PDIP, which is must more robust than the smaller packages the chips on the Pi use.

Can I safely use this approach with the Pi, or will it likely destroy it? Has anyone tried?

ACarter
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berry120
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    Given the number of RPis in existence I highly doubt anyone dared try :D –  Jun 12 '12 at 22:55
  • I'd be most worried about ventilation. – Jivings Jun 12 '12 at 22:55
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    http://raspberrypi.stackexchange.com/questions/105/can-the-raspberry-pi-run-in-an-airtight-case answers that there are no ventilation requirements. –  Jun 12 '12 at 22:56
  • @Tibor That's a good point, but you can always guarantee someone at some point might be crazy enough...! – berry120 Jun 12 '12 at 22:56
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    @Tibor if you read the link it says allow 2mm around the components. – Jivings Jun 12 '12 at 23:00
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    Mea culpa, I didn't. –  Jun 12 '12 at 23:02
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    What makes you think the BGAs and so on are going to like epoxy any less than DIPs? The only problems I would consider are thermal (what are the properties of potting compound?) and gumming up the connectors. – blueshift Jun 13 '12 at 03:56
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    @blueshift Becuase epoxy can shrink slightly when it cures, which wouldn't apply enough force to displace a DIP connection but might do so with a BGA / similar (at least that's my logic.) – berry120 Jun 13 '12 at 14:08
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    You would need a thermally conductive, non-shrinking inner epoxy. Once that cures, you can use any outer epoxy, though thermal conductivity would be important if you plan a thick coat. You will want expoxy that cures at 130F or less. I believe that a 1mm coating of 3M TC-2810 would do it. – David Schwartz Jun 20 '12 at 03:54
  • What if you just spray paint it with clear coat (or other colour) and enclose it in a box. Surely the spray paint will protect from dampness and the box from bad weather? – Piotr Kula Apr 11 '13 at 13:05
  • Instead of using Epoxy, you could use Raytech Magic Power Gel, or their normal Magic Gel. The PowerGel version stays sticky and is reusable, while the Magic Gel cures, but stays soft. Both will protect from water (IP68), but not from vandalism. – Louis Somers Jan 05 '15 at 22:29
  • Alternatively you could spray isolating paint over it like M3 Scotch 1601. – Louis Somers Nov 16 '15 at 23:34
  • Aside from potting the whole Pi, does anyone know whether a microSD card inserted in a slot will survive being completely potted with epoxy resin (including contacts) and continue working? – Kozuch Jul 08 '18 at 10:17

4 Answers4

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What I would consider when doing this is the ventilation and heat dissipation.

Although I've already specified in another answer that there are no ventilation requirements for the unit, it is encouraged that at least 2mm be left from the surface of the board and the housing.

I would assume that this precaution is primarily for the GPU, as that is the component that reaches the highest temperatures during high intensity tasks.

Community
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Jivings
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    Of course if you're worried about the heat from the CPU or GPU, you could attach a heatsink and epoxy up to that. – Graham Wager Jun 13 '12 at 12:08
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You can do this but I see the following problems you will face: - The connectors on RaPi are not water proof and can not be waterproof in an easy way - You can solve the heat problem by gluing a small heatsink to the CPU, and use an epoxy that has good thermal dissipation characteristics

But this is going to be a VERY difficult task and you may need a lot of units before you'll get this to work properly.

Your best bet is to find a water proof box and then use small cables between the RaPi and the box something similar to this: http://factory.dhgate.com/computer-cases-towers/fanless-waterproof-industrial-single-board-3.5-sbc-car-pc-case-ip67-p39010795.html

berry120
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FarhadA
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3

Yes it's possible. Cooling will not be a problem, in fact, most potting compounds have higher thermal conductivity than air (e.g. this special compound outperforms air by a factor of 30, 10 being more common for cheap compounds such as silicone or butalene rubber). There are however a few things to watch out:

  1. Curing by-products. Compounds which are not designed specifically for use with electronics can emit water (bad), volatile acids (even worse) or other polar solvents as they cure, which will quickly destroy the electronics you potted.

  2. Curing / thermal expansion. Most compounds will expand/shrink as they solidify. This is mostly harmless for soldered boards, but if they get into connectors such as USB socket or SD card slot, they can lift the connector pins away from the pads. You should prevent the compound from getting into connectors, otherwise you may end up with connectivity issues later on. In most cases, putting adhesive tape around the gaps before potting is enough.

In the end, getting a waterproof case may be a better solution than potting.

Dmitry Grigoryev
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2

You can buy small aluminium plates and glue them carefully with a super-conductive glue to the chips. Then you can plug cables to all the connectors and glue the whole device into epoxy. Epoxy itself is dielectric so you should be safe. However, you can still encounter several problems:

  • The heat/cooling and stabilisation of epoxy can damage some parts of the device. The pressure changes in that material can be very high. (This can be solved by covering it in epoxy in several steps, lowering the heat produced and the pressures involved.)

  • The epoxy can get between the cable pins and the plug pins, making them disconnect. (This can be solved by using some super-conductive sprays that exist and that are used in extreme conditions, I would as well invest money into expensive gold-covered cables)

  • If you seek for waterproofness, epoxy might not be the best option, it is hard but fragile and can leak water though the crack. I would go for some sort of rubber, e.g. fluid latex, which should work well and stays slightly elastic. Either way (epoxy/latex) you'll struggle with problems of water leakage along the cables.

yo'
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