It's this really the case though? That bottom plate would be far too hot to hold if it got that hot down there, wouldn't it?
Can you elaborate on your testing procedure that lead you to conclude the temperature of the circuit board under normal conditions?
I don't know what the temp inside the TM2 is. It's a concern that I have based on the testing
@WhyWhyWhy? did and the temp range specified by TinyMight. I don't know how well the zirconia ceramic insulates the PCB ambient temp.. this is something TM would have to characterize during their design/test phase. The leads themselves will also conduct temp, so it becomes a full PCB Monte Carlo style simulation, which I doubt they do.
My concern is mostly for session mode where the heat builds up in the unit. I'm also not sure how much thought TM put into the thermal design. I would think at a minimum the critical components should be placed on the PCB so that fresh air is pulled over them during an inhale. It seems like the air intake consists of the openings surrounding the stem. Maybe fresh air cools the outer shell of the zirconia ceramic and PCB, the question is that enough especially during no inhale (session mode). I have to guess what makes sense, because I'm not taking apart my brand new PH. So, I'm a bit blind here. Maybe
@gangababa or someone that has taken apart a TM can share the intake air path.
For me, I'll stick to on-demand mode and I prefer lower temp settings anyway. If I was a user who used "10" on session mode, I would be nervous. Keep in mind Abs Max ratings are process and architecture based and tend to be conservative. However, something like solder melting is likely catastrophic. My guess is the usage model most people use limit the chance of reaching temps high enough to reflow solder. WhyWhyWhy was illustrating a worse case example by longer than usual inhales. His data and what I know about the PCB so far suggests there is no temperature regulation only control over the heater drive. I may not have the full picture because the device seems to compensate for load conditions (inhale). Again I don't have a teardown or schematic, so I have to guess they are using an ADC channel for the heater setting (temp dial) and another one with a thermistor to compensate for load (inhale). I don't see why with the MSP430 they don't also control for overtemp conditions. You never know what sort of issues they were dealing with behind the scenes... or didn't consider. (I would also have to take a closer look at the ADC arch used in the MSP430).
At this point it doesn't really make sense for me to go any further. I'm willing to assume the TM2 PH will work fine with my personal use case, since there doesn't seem to be temp related failures reported on here. I am retired after all.... I don't want to do this stuff anymore even when I'm getting paid for it.