On the TV there was just a thing about fighting terrorists and particularly nuclear devices.
One of the things in it was that a team had liquid nitrogen. They said they didn't have info about what it was for, but sources said that it was cold enough to freeze electronic devices.
So, is there any truth in that? I could see that batteries at that temp might stop, but does really cold affect silicon circuits. Everything I have heard makes me think silicon likes cold if it doesn't break wire connections or such.
It is standard operating procedure to design MIL devices for -55°C operation.
And storage temperature is really of function of the packaging, not the silicon.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Nonsense as stated, but practically sensible. While individual chips may be designed for -55C operation (and I wouldn't count on it for devices targeted at consumer devices) electronic _assemblies_ often fail at cold. Digital circuits fail because CMOS tends to speed up at cold, and each device speeds up differently. As a result a circuit which has perfectly safe timing at 0 degrees or even -40 may fail at -55. Analog circuits fail because everything changes; they usually try to operate but fall out of tolerance in one way or another.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
My comments on Jim Thompson's post notwithstanding there are devices which are routinely designed to operate at 77K.
77K is a _very_ popular temperature for cooled infrared detectors, the modern versions of which involve a focal plane of exotic semiconductor diodes (like InSb, HgCdTe or GaAs with multiple quantum well diodes) laminated to a fairly ordinary read-out circuit made of silicon. The whole assembly is built into a dewar and cooled to 77K where the electronics perk along quite happily.
The IR detecting diodes have such low bandgaps that at room temperature they tend to go ohmic. The read-out electronics may or may not operate at room temperature -- some are rated for room temperature, some have to be cryogenic before you are allowed to turn them on. At any rate the image tends to be really crappy unless you're quite close to the correct operating temperature.
So you can design a chip, or even a system, that will operate from room temperature down to 77K -- but you can't expect a consumer device to be happy much below 0C, and even military devices must be carefully designed to make it down to -55C without problems.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
"...a circuit which has perfectly safe timing at 0 degrees or even -40 may fail at -55" sounds like bad design to me ;-)
Of course any temperature below ~70°F is too damn cold... it's cold this morning in Phoenix, but it'll be 100°F by noon ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I read in sci.electronics.design that xray wrote (in ) about 'cold enough', on Wed, 12 Oct 2005:
LN2 temperature would upset the working of many electronic devices. But if one were deigning a device to go bang, and one knew that LN2 might be used to disable it, it would be quite easy to arrange that the LN2 made it go bang immediately.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
We routinely blast our prototype circuits with freeze spray, especially FPGAs and other fast logic that may have timing margin issues. That gets them down to about -55C, and we've never seen a part quit working down there. We heat them, too, to see what margins are... all logic families I know of slow down when it gets hot. We usually go to 120C or timing failure, whichever comes first.
I guess some linear parts may crash cold... bias networks or whatever. Jim may know.
I'm eager to get a real, big, LN2-boosted enviro chamber for serious system testing, but currently we don't have space for it.
I've been doing accurate temperature compensation since the early '60's, so much so that my nickname at Motorola was "vbe Thompson" ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
formatting link
| 1962 | I love to cook with wine. Sometimes I even put it in the food.
Beta certainly increases, but speed changes with temperature will depend on logic type... properly designed PECL is pretty flat.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Most silicon devices will stop working (reliably) at -40 degrees Celsius or below, many wont even go that far. Storage temperatures should often not be lower than -65 degrees Celsius. So yes, temperature is an issue.
The silicon devices which rely on thermal excitation of charge carriers to the conduction band tend to stop functioning at low temperatures, including depletion-type MOS- and J-FETs. Even though enhancement-type FETs keep functioning there may be too weakly doped regions in the current path (like ohmic contacts) that they stop functioning also. Typically the freeze-out temperature is lower than 77K, though.
A complete circuit, including an integrated one, is typically driven off its design margins (biases, offset voltages, timing...) when cooled to 77K. Even though every active device in the circuit may keep functioning, they no longer co-operate as designed.
The last time I had free access to an enviromental testing chamber with a decent sized port for running cables in and out, was at George Kent, from 1973-76.
EMI Central Research must have had one somewhere, but we got by with freezing spray and hot-air guns. Cambridge Instruments never bothered to get one - and on one occasion I found myself relying on the way the building heated up during the day to get a handle on the temperature sensitivity of a crucial circuit.
Haffmans BV had two big enviromental test chambers, but they were used for everything - including roasting silica gel to get it dry - so they weren't all that accessible. We mostly used temperature controlled baths when we wanted to look at the temperature behaviour of our circuits. Wouldn't have worked for big boards.
10K ecl and EclipsLite, on real boards, slow down a bit with increasing temp, usually a ps or two per K per package. Some of that may be pcb prop delay, I guess, but I always wind up compensating for drift in that direction.
The place where I got my experience with cryo-cooled circuits has a couple of such chambers. One of their suppliers is small and got some covert snickers when they admitted to testing parts with dry ice dumped in a styrofoam cooler.
Now they've moved and Engineering no longer has access to the chambers, so they're thinking of going down to the local Baskin & Robbins for some dry ice...
My point being that you can do some amazing things with a cheap cooler, some nichrome wire and various frozen substances.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
formatting link
| 1962 | I love to cook with wine. Sometimes I even put it in the food.
The real pain with going cold on the cheap is condensation. What I'd really like is a LN2-cooled chamber, full of nice dry nitrogen. NOT walk-in size, of course.
I would expect that sublimating dry ice would have the same effect as boiling LN2: the gas generated would displace any water in the air (as well as the air for that matter).
You want to be careful around LN2 it in a closed room because it'll displace oxygen along with water and everything else. I don't _know_ if the effects of CO2 would be worse but I suspect it would because your body regulates breathing by measuring the CO2 in your blood rather than oxygen; presumably lots of CO2 in a room would mess you up worse than an equal amount of excess nitrogen.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
I'll disagree. IBM's ECL was pretty well designed[*] and was significantly faster at its design temperature (85C) than cooler. Enough so that thermal insulators were put on the cooler chips to get the temperature *up*.
[*] unless you're begging the question and "well designed" == flat.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.