Cold testing

Put the board in a Ziploc bag?

A small CO2 fire extinguisher will do a good job for $12 or so.

Cheers

Phil Hobbs

How big is the part and how many parts do you need to test? Ordinary freeze spray does a pretty good job going down to -55C.

DUT

poor

for LN

case

Tenney makes some small chambers that go to -75C using compressor refrigeration. Art

I would like to have a reasonably inexpensive system to test parts from about -55C to +30C; higher temps already accounted for. I got down to -10C by using chunks of dry ice on trays above and below the DUT inside of an EuroPro toaster oven (only fan on). Major objection is all of that accumulated water; the outgassed CO2 did a poor job of displacing moist air (45-55 RH at start).

I cannot afford one of those small industrial test ovens that is outfitted for LN or for CO2. Maybe the oven by itself, but the source of the liquid in either case is a no-no.

Ideas?

low

r134a is used in most refrigerators and I think also most freezers it is -26C at 1 bar

some use R404a it is -46C at 1 bar

it is generally not recommended to run the low side at vacuum but you can do it, as long as there is no leaks, you can keep the compressor cool and you don't to high pressure on the high side etc.. etc..

r404a would be -55C at ~0.6bar

peltier need a crazy amount of cooling to do anything, maybe if you bolt them to the freezer element and isolate everything but the cold side. Your average freezer doesn't have whole lot of cooling power its is mostly meant to remove what heat that leaks through the insulation if you put something inside that adds heat it'll be hard pressed to keep it cold

On the clima test box I use the compressor is probably 10 times bigger that the one in my refrigerator/freezer

-Lasse

That's correct but since Robert was ruling out industrial gases I assume he wants to or has to do it "on the cheap". Then a freezer might be all that's in the cards. It is like with the proverbial toaster oven for SMT board soldering. It works to some extent but is a very slow process.

Go to ebay and search for "refrigerated cold trap". These are vacuum traps with a refrigeration system that cools a coil down to about -60C at best (single stage, two stage ones go to about -100C) to freeze out anything between whatever you are pumping on and a regular two stage mechanical vacuum pump (best if it bases out at

the DUT

poor

outfitted for

case

driven

This one has 2 compressors which are run in series to get a 2 step drop in temp.

That chest freezer may well the way to go for my needs, do not really need -55 but i was going for broke (most extreme temp fantasy is -70C). I consider that half of the problem; its that hard rocky stuff that grows on sublimating CO2 that needs to be removed before it can grow there.. How good is that air-drier gunk anyway, 'spose it will not like cold.

Well, if all i cared was "it got cold" and "maybe went to mumble see" that would be OK. But i would like to capture at least 5 digit voltage data and at least 3 digit temp data. Better: capture going down, then back up to send mind hysterical

Each part is about 0.6 by 1.6; so that is a maybe possible solution. But..the frozen H2O is not tolerable. Not necessary,but would be nice to test up to 10 unis at a time.

DUT

poor

for LN

case

Thems the ones used in the Semi industry, all of those i saw were low temp driven either from liquid CO2 or LN2 (LN2 FAR more efficient and cannot get cheated).

DUT

poor

for LN

case

Ahhhh..dream on.. Lowest price one is prolly the TJR. A bit big compared with those i had used, an i bet way beyond budget of Socially Insecure.

Thanks.

Bingo! Major reasons for no industrial gases: no transportation, no storage space, major handling probs for me, and expense. Now..if i could make dry air (or nitrogen) on a continuous basis, cool it to desired temp, then it would purge the small volume of interest (maybe 2x2x3) and cool the DUD (err..DUT). Order not set in stone, result is what counts.

Reminds me of the far gone daze when i helped a friend build a working 2MEV pulsed KR accelerator..

the easiest way to to set the the hardware RTC to UTC and then tell your OS to use that, that way there's no confusion at DST boundaries or other timezone changes.

The one dimmie uses for his flights of fantasy.

Move to Delta Junction Alaska. The offical record low at ft Ft. Greely was -69F, and zero humidity.