So - could a combination of these things cause failure? It was working normally all evening after the heat incident.
Sorry it took so long to reply. I couldn't find any info on what temp the Pixel will shut down due to heat. However: Most CPUs will at least throttle at 100 degrees C. This is a built in safety so the CPU won't fry itself to death. Common electrical solder will melt between 90 and 450 C
<link>. I'd guess a lot has to do with what makes up the solder. Softer metals like lead lower the melting point.
Thermal throttling (of desktop CPUs at least) happens just above the low point in the range I listed. Ambient temperatures don't help really, and keep in mind, these are basically pocket computers we are carrying, and every computer CPU needs a way to disperse heat. In a laptop/desktop, there are fans. A phone has to passively cool itself. Glass backs and cases don't really help (glass is a very good insulator, and plastic/rubber is no slouch either).
It's possible all these things combined made for the perfect storm for this to happen. The downside is, until the phone is cracked open, we won't really know what happened. This could be the result of many things. Other variables we haven't even considered yet. I've seen a fried desktop CPU go, Nothing was wrong with the cooling or manufacturing....it just went.
Overall....I'd say just be careful as to what the phone is going through. Some games can put a phone through the ringer.
Sorry for the long winded post. Hope it wasn't too boring?