Effectively Electrically Insulating TX2 Module

Hey guys

I’m getting a demo product ready to show off, and am in the process of creating a case for it. It’s based on a TX2 with a carrier board and a few peripherals. I’m working on creating a CAD of a custom case and 3D-printing it (and am learning what a pain in the behind 3d printers can be), but in the meantime I need something as a quick a dirty prototype case.

So what I’m thinking is I wrap the module in thermomorph as a stop gap, but I want to wrap the electronics up for safety. I’m thinking Kapton tape, but this is not an area I know much about. Any recommendations? Then end goal is to have the case (which is going to be plastic first, then eventually aluminum) be designed to keep the electronics suspended, but for the quick and dirty shell I need some measure of safety to protect the components.

Kapton tape is pretty good for many things electrical or as thermal insulation (sometimes when I do hot air rework I put kapton tape around the area not needing direct heat).

FYI, the form factor of the dev board is mini-ITX…is it the dev carrier board?

For chemical and environment sealing before any kind of liquid cooling immersion (or before exposure to cold or moist environemnts where condensation may hit) you’d coat everything which isn’t used as an external connector with “conformal coating” (you’d also leave it off of surfaces needing to dissipate heat). This is a rubbery sealer…not unlike gelatin. It can be peeled off later.

Conformal coating is what a factory would use, especially if “ruggedized” for harsh environments…you can mask off certain places with your kapton tape (or most anything), and then simply coat it with a brush…it’s easy to use and forgiving. You don’t need kapton for the conformal coating process…it doesn’t generate heat, it doesn’t stick permanently (though it does stick well enough all by itself), it doesn’t get completely hard (it does “toughen up”), and curing does not produce any by-products harmful to the circuit board. Conformal coating is immune to most chemical solvents which you might end up using for liquid immersion.

linuxdev, I hoped to hear from you :)

The carrier is an Orbitty. So the form factor is the TX2 module’s X, Y dimensions, plus the depth of a carrier and heat sink.

As an aside, I’ve figured out a use-case for this thing that’s getting more positive feedback than the rifle-mounted approach, so I’m no longer needing to absorb serious shocks. It’s just handheld.

Any opinion on which kind of conformal coat? Polyurethane, silicon,etc?

Another aside: I see that some Kapton tapes ignite when touching a flame (the tape I have does) - I’ve read it may be the silicon coating used as an adhesive. Does that sound right?

What kind of temperature range are you expecting? If kapton bursts into flame it’s a seriously hot environment. Can you say more about the environment and especially about anything related to temperature and mount points?

I don’t have any specific advice which type of conformal coat to use. Most of the vendors will have detailed information on what their product will survive. I wouldn’t expect ordinary silicone to be a good choice since it produces acetic acid during cure. If you needed this, then what I’d do is cover it with a more conventional conformal coat, and then add silicone on top of that without it touching the board itself (I am betting silicone sealer and conformal coating have a very good bond to each other). Conformal coating could be considered a weak adhesive…it won’t just fall off, but you could peel it off with a fingernail or putty knife.

The temperature range / environment is outdoors, anywhere in the world. So Winter cold to summer desert hot. The electronics won’t be exposed, so I can’t think of any reason there should be a flame or a spark - but I know there are always situations I don’t think of. now that I think about it, I have kapton on the hot end of my 3d printer and it’s fine, and I’m not forseeing any use nearly that hot.

Mount points are on standoffs for now, plastic for now. Nothing special; they’re mounted to the plastic, eventually aluminum case.

It sounds like ordinary conformal coating of anything not needing electrical contact or thermal dissipation is all that is needed for protection against moisture and condensation. I don’t know if you would need extra cooling or heating for the more extreme temperatures, but it seems likely to need this for some of the extremes. Most of the carrier boards out there have a slightly narrower temperature range than the module has, and although the operating range for the module is fairly wide (I couldn’t tell you exactly what it is), I don’t think it would survive something like winter in Alaska or running with all cores maxed out in a desert.