This is from an AMD video card design book. Shows the max case temp, and breakdown temp for the silicon junction.
Parameter | Minimum | Nominal | Maximum | Unit | Note |
OperatingCase Temperature | 0 | — | 105 | °C | 1 |
AbsoluteRatedJunction Temperature | — | — | 125 | °C | 2 |
StorageTemperature | –40 | — | 60 | °C |
|
AmbientTemperature | 0 | — | 45 | °C | 3 |
ThermalDesignPower | — | SeeTable59 | — | W | 4 |
Notes:
1. The maximum operating case temperature is the die geometric top-center temperature
measured through proper thermal contact to the back side of the die. This is the temperature
at which the functionality of the chip is qualified.
This is a Quote from Intel and their thermal design as to their "breakdown" temperature.
“If the external thermal sensor detects a catastrophic processor temperature of 125°C (maximum), or if the THERMTRIP# signal is asserted, the VCC supply to the processor must be turned off within 500 ms to prevent permanent silicon damage due to thermal runaway of the processor,” says the January 2008 edition of the datasheet for Intel’s Core 2 Duo Processor."
So as you can see, you are absolutely right. There is a physical limit to the temperature a pnp, npn, or other silicon junction can handle. It is reaasonable that there would be a temperature where these little 20nm junctions would burn up, or melt together or just plain quit working.
So it looks like the "operating" die temperature that most companies want you to design to is around 40C with peaks of 70C. at least from the tech sheets i read. So if you run over that, you are shortening the life of your product. Results May Vary. 🙂
TeB