Electronic – Electronics in high temperature environments


I'm relatively (ok, very) new to electronics. I'm trying to find where to buy parts (or even just more information on what sort of materials I should be looking for) to build a circuit board with a micro controller and RF transmitter that can withstand being exposed to a hot, dry environment. The upper end of the temperature range would be 200C (~392F), and would be need to be able to operate under constant exposure to this temperature for 8-12 hours. Ultimately, it would need to be fairly small (we're hoping to keep it smaller than the size of a couple 9V batteries stacked together)

Not being a traditionally educated EE or material scientist, I'm very much out of my element here – referrals to other sources of information, web sites, etc., so that I can at least get an idea of direction would be tremendously helpful.

I would also be interested to hear more information about thermal protection methods – would there be a way that I could build an enclosure to protect the internal electronics from the same environment. I would think that no matter the sort of "housing" I could build, without an active cooling system (which is all but prohibited given the target form factor), then the electronics themselves would need to be able to tolerate the temperature – but I would certainly love it if someone could correct my naive assumptions here.

Thanks for any advice/help.

Best Answer

This is well into the territory of "hire a specialist design firm". It's going to be expensive, so you might as well do it properly and hire people who know where all the pitfalls are and where to get all the parts.

TI have some high temperature microcontrollers, and a design guide linked from that page. The SM320F28335GBS is good up to 210 degrees (which is cutting it a bit close). While you can buy from Digikey in single quantities, they cost $300.

The other approach you could take if the operating time is limited to a few hours in that environment and the box can be sealed with no wires in or out, is to insulate it very heavily. Add some thermal mass, preferably with a phase change. Do not exceed the stated cooking time.

You'll end up with a something like a meter cube of fiberglass or foam insulation containing a sealed shoebox of methanol with the electronics floating in it, which will stay below 70C until it boils dry, hopefully for long enough for whatever your heating cycle is. At which point you need to cool it down again equally slowly. I think that's the only viable strategy for normal temperature electronics which doesn't involve active cooling.

Edit: normal batteries do not like high temperatures either, although there are special high-temperature molten-salt ones used in some missiles.