By the way, when you're snooping around with a thermal cam or IR point-and-click thingymabob, look for the highest temperature you can find. Shiny is the reason: a shiny surface, with low emissivity, largely looks like its surroundings. A mirror. But even a mirror can give up its secrets, under conditions. What you're looking for are acute inside corners: even if made of mirrors, such shapes reflect light down to the root, where it's eventually absorbed. Thus making a pretty good black body.
Example: you might have a silvery aluminum heatsink with shiny chromed screws in it. Most of the heatsink is useless because it's shiny and metallic. But you can pick up a glint of strong emission from the cross on the head of the screw, and in the gaps around it, where it touches the heatsink. Aha, interior reflection, black body emission!
The temperature may still be hotter than this reading yet, but it's at least a good start.
Lesson #1: a black (i.e., not glowing) object might not look hot, but you still don't want to go and grab it. (Ouch!)
Lesson #2: a black (i.e., not emissive) object might not look hot, but if you can see some spots on, or connected to it, that look hot, you can at least guess what the rest of it is doing. Maybe.
As for semiconductors, what they're rated for depends, but it's quite common to run heatsinks over 100C. Semiconductors usually die above 150 to 200C, depending on packaging and design. The internal junction temperature is necessarily hotter than the case, which is, in turn, hotter than the heatsink. Calculating how much of each requires knowing only the power dissipation and thermal resistance between each pairing.
So do be careful -- 150C isn't that much hotter than 100C, and transistors may be near or into the failure range under that condition. But the other point is, if it's a responsible design, it is absolutely possible to operate like that, without it being dangerous.
Tim