Temperature chamber for PCB thermal testing - Page 1
Forum section: electronics / projects

author: lutkeveld
author_rank: Regular Contributor
timestamp: January 05, 2024, 02:13:58 pm
content: Hi all. For some customer projects I would like to get an easy way of validating a PCB over a certain temperature range, usually -20 to +85 *C.Does anyone here have a recommendation for a product which could help out?Lots of chambers I can find only offer heating, not cooling. Or they are too big/expensive. Looking for something under a 1000 USD preferably.Maybe this is not even possible, and I would need seperate chambers for heating/cooling testing.Some also offer controlled humidity, which would add another level of validiation, which would be great.

author: CaptDon
author_rank: Super Contributor
timestamp: January 05, 2024, 02:58:39 pm
content: Your best and probably cheapest solution is to look online for used industrial equipment resellers. The smallest chamber I ever used that could go -20C to +150C had a freon loop cooling system and an electric heating element for heat. It was still the size of an apartment refrigerator. These units all have one flaw...In the cooling mode they accumulate internal moisture no matter how well sealed you try to make them. Only the ones that use dry nitrogen as the cooling agent as well as the purge will stay 100% moisture free. The hot boxes are easy to find and not as expensive but remember there has to be an access hole for all of the test cables going to your measurement equipment and a high density closed cell sponge to jam into the opening. There are hot and cold boxes using Peltier cooling devices but they have a poor ramp rate and that hurts if you want to do 6 hot and cold cycles between -20C and +85C. The ramp rate becomes even slower if your unit under test has a lot of physical weight / mass. I don't think there is a 'cheap' solution and you need to look at the specs very carefully to be sure the unit can do what you want it to. We had huge 'Thermotron' units at work and I can tell you their field service reps are clueless. Scout the used industrial equipment sellers and see what you can find. Shipping may also cost a fortune as these units have lots of size and weight. After all, you may want a chamber of at least 15" X 15" X 15". And of course the unit will need some sort of P.I.D. temperature controller, maybe even one of the auto-learning type. 'Good' and 'Cheap' are rarely in the same sentence!! Cheers mate!! Best wishes in your search!!

author: kuon
author_rank: Regular Contributor
timestamp: January 06, 2024, 02:56:31 pm
content: Quote from: lutkeveld on January 05, 2024, 02:13:58 pmI do low cost testing with a freezer and an oven, regular kitchen appliances, from -20 to °90, but you get no humidity control and not temperature ramp control. I just move the boards between freezer, shelf, oven and vice versa.

author: berke
author_rank: Frequent Contributor
timestamp: January 08, 2024, 08:17:48 pm
content: Quote from: kuon on January 06, 2024, 02:56:31 pmInteresting please do tell.- Do you just rely on the built-in temperature controls?- How do you deal with condensation if at all?- Are your boards coated?- You must have opened holes in the appliances to get the cables in/out, anything special for plugging the holes? Kitchen sponges maybe?

author: lutkeveld
author_rank: Regular Contributor
timestamp: January 09, 2024, 09:00:59 pm
content: @CaptonInteresting ideas, but size is indeed a big consideration. A huge industrial chamber does not fit and also would take excessive effort to heat up / cool down quickly. My PCBs are almost never larger than 20cm. A bit bigger is okay and maybe unavoidable, but am looking for something 'desktop size' if possible@KuonThat is indeed how I have been doing it now. Used my reflow oven set to a constant temperature for the heat part.It is okay, but am now looking for something that is a bit more professional and can also cycle tempature from hot to cold and vice versa.@BerkeExactly the problems I am running into. Do not know how profesional HALT/HASS chambers do it, but if I were to get something cheap I would probably need to mount (something resembling) cable glands to get some power and I/O cables in and out.

author: selcuk
author_rank: Frequent Contributor
timestamp: January 09, 2024, 09:37:14 pm
content: As suggested, cheapest option is already owned oven + refrigerator for temperature testing. And big enough IP65 enclosure + calcium oxide (warning!) + damp towel for humidity testing.I hope to see someone do a reliable, open source, peltier based test chamber so we can build for ourselves.

author: kuon
author_rank: Regular Contributor
timestamp: January 12, 2024, 04:08:49 am
content: Quote from: berke on January 08, 2024, 08:17:48 pm- I have some thermometer within both appliance. I also check board temp with thermal camera when I take them out.- For condensation, I put the board in a IP68 electrical box with a bag of silicate gel and one of those paper that turn pink with humidity.- No, the board are not coated. My boxes are airtight with cable glands for cables.- Just drill some holes and put some cable glands, this way you get something airtight and you can change the cables depending on what you need. In the freezer I had to screw an aluminum plate on the inner wall because the plastic was too thin to screw the cable gland in. Also the electrical boxes I use have many configurations of cable gland possible.Boxes I use are like this, they are easy to open/close, you can see inside, and you can easily mount the boards inside with perforated metal plate:

author: Smokey
author_rank: Super Contributor
timestamp: January 12, 2024, 05:49:31 am
content: Just as a data point, I've been involved in refurbished two Tenney Jr. thermal chambers from the 1980s now. If they need any work it's a pretty decent pain in the ass, so heads up.Just because you can pick one up cheap expect some issues like coolant not being manufactured anymore, non-existent modern control interface, wacky mechanical/electrical systems, etc.The first one we didn't know what we were getting into and probably spent more retrofitting it than we would have just buying something less old a crusty to start with. The second one... that's on me. I should have known better.

author: Jeroen3
author_rank: Super Contributor
timestamp: January 12, 2024, 06:41:08 am
content: I have also used an auctioned industrial chest freezer. Goes to -35C iirc. (just make sure there is some thermal mass in it, scrap metal or something)If you turn it on with your board in it, and then don't open it when cold, there will not be an accumulation moisture.Drawback, it takes 6 hours for it to get cold, and your board tests must be compatible with the constraint to not open the lid during tests.For thermal cycle testing you often need an test certificate as well, so then I rent an actual temperature chamber.

author: ch_scr
author_rank: Frequent Contributor
timestamp: January 12, 2024, 09:13:14 am
content: The hobbyist desktop option is a peltier chamber + controller. For the "cheapest option" peltier controller, look for "TCB-NE" on Aliex. I have one, it works fine and seems quite well made.To get a cheap pre-made peltier chamber, a reptile incubator or a car cooler box can be used. That won't do -20 to 85°C though.You'd have to get a "high-temperature-type" peltier element(s) and insulation material which can withstand that, for the high end.Since the "heat to be transported away" limits the lowest reachable temp in peltier systems, to get below -10°C,you'd need a very well insulated chamber and nothing that produces much wast heat in it.The speed of the (downward) temperature swing will be limited by the same effect.With all those caveats in mind, it's still the cheapest, smallest desktop option!

author: srb1954
author_rank: Super Contributor
timestamp: January 12, 2024, 11:33:41 am
content: Quote from: CaptDon on January 05, 2024, 02:58:39 pmOne firm I used to work for used to put all their product through a couple of rapid temperature cycles in a large temperature chamber to weed out poor quality parts.Due to poor sealing of the chamber the moisture ingress was often a major problem. When the weather was very humid so much moisture could accumulate in the chamber that it sometimesrained insidethe chamber at commencement of the rapid cooling cycle!

author: jonpaul
author_rank: Super Contributor
timestamp: January 12, 2024, 01:46:06 pm
content: Easy fast zero cost:1/ Idinitfy temp sensitive parts eg ICs2/ soldering iron, or heat gun, hold at low temp on top of part 30 sec, observe ckt performance3/ Freeze mist spray or cool with ice cube in plastic bag, dry iceObserve ckt performancej

author: berke
author_rank: Frequent Contributor
timestamp: January 12, 2024, 02:27:40 pm
content: Quote from: jonpaul on January 12, 2024, 01:46:06 pmThat's a good starting point but very rough and not always practical. Case in point I had a stack of four PCBs, I did the heating gun/spray thing where I could, but some parts (between boards, behind connectors) are hard to access. And with only two hands you can't simultaneously heat/cool the boards and run the tests.Actually I just had an idea. Someone could make a heating blanket for PCBs. Put some resistors in a silicone pouch. Is silicone ESD safe?

author: kuon
author_rank: Regular Contributor
timestamp: January 18, 2024, 09:13:17 pm
content: You can use a heating bed for 3d printer.Keenovo makes a lot of them:https://keenovo.store/collections/standard-keenovo-silicone-heaters/products/keenovo-silicone-heater-pad-with-digital-controller-for-3d-printer-pyrex-evaporating-dish-vacuum-purging-chamber-etc?variant=12891467579447