Operation at cold temperatures and YIG performance 2

[Tunalover]

Can anyone shed some light on this subject? We have a customer that wants to operate our product at -35C but it was designed only for 0C. I suspect the weak point will be the YIG performance but can't seem to find anything on this! Would there be any other concerns, for example, parts with plastic cases or CTE mismatches?
TIA for your help!



Tunalover

 

[itsmoked]

Man u got to cough up a little more info... YIG?? What is designed for 0C normal operation that would possibly care about warm room temperature?? CTE?? What KIND of product a toaster? MRI?

 

[VEBill]

YIG is usually intended to mean Yttrium Iron Garnet (YIG), this material is often used in microwave oscillators.

 

[buzzp]

There are two philosophys on electronics in general concerning cold temps. One (I dont agree with), it to assume you know more than the mfg and test the completed product at the coldest temp you will operate (-35) and leave it there for a couple hours then apply power and see if it works - if it does, put that temp rating on the device. Second (the right way), is to use parts rated for this temp.
Just because it works one time at whatever temp does not mean it will next time. I have seen many mfg's go with route one and to me, this is not the correct way. You would be surprised how many choose this route. I suppose if the product is generating enough heat, it may never get this cold (if power left on).
Chances are, most of your electronics are rated 0-70C or maybe -20 - 70. Mil spec parts are probably what you need.

 

[logbook]

"Old fashioned" transistorised circuitry used to fail at low temperatures because the gain of bipolar transistors drops by tens of percent when the temperature gets that low. Thus anything with bipolar transistors in it may no longer function.

Electrolytic capacitors may have a problem with the electrolyte.
Batteries in memory backup applications may not work to full spec.
Timing on high speed logic circuits may change enough to cause failures.
Resistors, NP0 ceramic capacitors, diodes, X7R capacitors should be ok.

 

[Tunalover]

Sorry guys. I assumed these were industry-standard abbreviations. A YIG(Ytrium Iron Garnet) oscillator (sometimes just called a YIG) is part of a microwave radio. Also, CTE=Coefficient of Thermal Expansion.

itsmoked-
You said "What is designed for 0C normal operation that would possibly care about warm room temperature??" Who said anything about warm room temperature?


Tunalover

 

[itsmoked]

Yeah sorry tunalover, I never saw the minus sign in front of the 35.. oops. Thanks for the clarifications.

Yes the YIG won't be happy.. However most makers will qualify their crystals at lower temps if requested. I have gotten xtals rated at -40C. Yes, the plastics may have a problem. They may get a lot more brittle too. Everything logbook mentions is right on. Coming back from those temps is nastly as a ton of condensation can occur, especially if the product is like a service tool in and out of buildings.

Label adhesives my fail.

 

[buzzp]

Condensation can be overcome by spraying conformal coating over the completed board (still not 100% humidity proof but way better than no coating). Definately needed if temp fluctuations are such that condensation can occur.

You can find standard micro crystals with this temp range pretty easily. Not sure what the availability will be with the crystal your looking for.