What goes into making something hardened

[lordulrich]

I have a pretty general question as to what goes into making an electronic device hardened for temperature?  At work (Civil Engineer) we buy lots of electronics that cost upwards of 10x of a comparable device that does not meet the temperature spec.  I know that this spec is important, but I am curious what is the difference? Is it just higher temperature spec chips? is there a different spec in the circuit boards?

Thanks

[Phaedrus]

Devices that meet automotive or military temperature specifications undergo much more thorough testing and validation to ensure that they operate in the temperatures required. For instance, a batch of chips might be "burned in" at 125 degrees Celsius for a number of hours, and if one chip fails the entire batch is deemed unfit for that specification. Likewise for low temperature tests. And by fail, I don't mean burn. I mean violate any important electrical spec, even by a fraction of a percent.

The testing varies depending on the component in question, and on the company performing the test. But generally there is a lot more testing and QA involved.

[tszaboo]

For example ICs usually have ceramic packages, or other hermetically sealed packages. There are less components to chose from, so you cannot just put there your favorite amplifier, you have to chose from something which is actually made for it. Electronics is temperature dependent, so offsets are bigger, errors are bigger, you need more parts to get rid of the errors.
Power dissipation must be lower than in normal operation, as it would overheat itself. For this you need more efficiency or more parts. And this is only the component level. There is testing, sourcing, hard to repair (because coating), for assembly you have extra steps, and it is harder to find someone that has the brains to put it together.