When the datasheet says: Operatning and junction and storage temperature range -55 to +150 degres C.
Does this mean that the transistor can be operated (safely)up to 150 degres C.?
Does this mean that the transistor can be operated (safely)up to 150 degres C.?
The 150C is the maximum junction temperature, allowing for the thermal drop from the junction/case,
the case/sink, and the sink/ambient. There will be some drop across the insulator also.
Long term operation at the maximum (estimated) junction temperature will likely decrease the useful life,
partly due to the large thermal cycling.
the case/sink, and the sink/ambient. There will be some drop across the insulator also.
Long term operation at the maximum (estimated) junction temperature will likely decrease the useful life,
partly due to the large thermal cycling.
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150 degrees C is common rating for Silicon.
I have seen a high-power low-gain transistor working for many minutes at 190 degree LEG temperature. (It had melted its solder.) The junction must have been much hotter.
Device life falls off very badly with high temperature. Unless you are building missiles or deep-well instrumentation, heat is BAD.
I have seen a high-power low-gain transistor working for many minutes at 190 degree LEG temperature. (It had melted its solder.) The junction must have been much hotter.
Device life falls off very badly with high temperature. Unless you are building missiles or deep-well instrumentation, heat is BAD.
In theory, if the junction temperature is <150°C, yes, but as already mentioned, the junction temperature is generally not the same as ambient.
You have to keep in mind that semiconductor devices tend to obey the general Arrhenius law, meaning a failure rate ~doubling for every 10°K (or C) increase.
The 150°C limit generally applies to plastic-encapsulated devices, not because of the Si limit but because the molding compound undergoes a phase transition at higher temperatures (Tg), causing dilatation stress.
All metal types can normally operate at up to 200°C, but the die-attach solder rarely likes cycling at these levels.
Keeping the device permanently hot is thus probably the best option if you really need to operate at very high temperatures.
Some devices intended for oil-well and other extreme environments are specified for 220°C, and even to 250°C, but they are very rare.
That said, I have seen a video digital-effect memory fail not from overheating per se, but because the chips were falling off from the horizontally installed memory boards, due to a fan failure.
The temperature of the chips was certainly well exceeding 200°C, yet the only symptom was the increasing loss of pixels blocks due to the chips progressively desoldering themselves.
After the fan issue was sorted and the fallen chips were resoldered, the Quantel machine worked as if nothing had happened... These are not recommended operating conditions though
The current and voltage levels also play a significant role in all long-term degradation effects and failure modes I have heard of. I guess those oil-well devices are designed for much lower current densities and field strengths than normal silicon semiconductor devices.
I'm not so sure about that permanently hot advise; temperature cycling and a permanently high temperature both reduce reliability.
I'm not so sure about that permanently hot advise; temperature cycling and a permanently high temperature both reduce reliability.
Individual transistor junctions can withstand 200C+ for a while. The 150C storage limit is a packaging limitation.
Thanks, I was under the belief of 150/170 a limit from the semiconductor material.
Good to know metal case transistor can stand higher temperatures as ultimate maximum rating.
It is a dangerous game because the junction itself has very little thermal inertia; When things,go wrong, it can only take 10mS to junction melt down.
Silicium transistors are far more resilient than Germaniums that were prone to thermal troubles, very easy to fry at the slightest mistake.
Good to know metal case transistor can stand higher temperatures as ultimate maximum rating.
It is a dangerous game because the junction itself has very little thermal inertia; When things,go wrong, it can only take 10mS to junction melt down.
Silicium transistors are far more resilient than Germaniums that were prone to thermal troubles, very easy to fry at the slightest mistake.