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For a usual silicon semiconductor, the junction temperature is rated at 150 degree C. That said, for lifespan reasons, the usual limit for junction temperature is around 100 degree C.

My question is whether a SiC device, say a diode, can allow us to run at a higher temperature?

Or is the advantage of SiC just limited to higher efficiency, small leakage current, etc.

Voltage Spike
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HYQ
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3 Answers3

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SiC devices in theory can operate at extremely high temperatures, however there are mechanisms such as thermal runaway and factors such as packaging that limit the operating temperature. Reliability can be greatly affected by temperature and temperature cycling due to packaging limitations, for example.

Most currently available devices I have looked at are limited to 175°C absolute maximum Tj, which is the same as, or similar to, many silicon and Schottky diodes.

There are applications such as military where cost is deemed to be not of great importance and more exotic packaging can be used and they can operate at 200-300°C. Here for example are some parts rated for >200°C.

Spehro Pefhany
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  • I know even for 150/175 C temperature limit, people usually don't go that high because it will fail early. Does military just always go near the limit and do 200 C? – HYQ Oct 03 '22 at 23:29
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    @HYQ I think it very much depends on the application. Some devices only have to work for a short period of time. – Spehro Pefhany Oct 04 '22 at 09:19
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    @HyQ, as Spehro said, more than temperature, sometimes it is temp *cycling* that is important. But military specs are "unusual" sometimes. For example, the electronics in a missile warhead is supposed to be armed and fired just once, so the problem of temp cycling is marginal. – LorenzoDonati4Ukraine-OnStrike Oct 04 '22 at 15:58
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SiC devices have better thermal conductivity (~3x better than silicon) and a higher junction temperature rating. So they are better than silicon in being able to remove heat from the device and operating at higher temperatures. But it is not just these parameters that will determine a devices operating temperature, epoxy and package conductivity also determine package operating temp.

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Source: https://www.digikey.com/en/articles/how-to-make-energy-infrastructure-more-efficient-and-reliable-while-reducing-cost

Voltage Spike
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7

SiC itself will work out to very high temperatures, but the rest of the device might not. It's not that far beyond normal working temperatures (maybe 250 °C or so) that aluminum contacts (the bits that let you connect to the semiconductor, inside the package) can delaminate, breaking the connection between the semiconductor and the outside world.

That said, typical SiC devices can function at much higher temperatures than silicon ones. That is, in fact, one of the advantages of SiC over silicon (though not the main one).

It's difficult to test devices out to high temperatures, though. Many ovens for reliability testing don't go higher than 180 °C, so it's quite possible that a part may work well past 200 °C, but the manufacturer doesn't feel the need to invest in new test equipment to test them past 175 °C.

You should also bear in mind that the reverse leakage of a diode is exponential in temperature, meaning it goes up rapidly as the part heats up. That may limit the usable temperature range for your purposes.

Hearth
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