We are seeing some failures in our chip at higher, but not max temperatures.
We are using an external 16MHz crystal and operating at 72MHz.
We are using the 85C rated chips.
There are two sets of firmware that we have been testing, one works just fine, and the other fails on power cycle at the higher temperatures. For both cases if they are already running while being heated up in a test chamber they continue to run fine without failing, the failure only occurs when power cycling.
Our first set of firmware includes a custom boot loader in the beginning of the memory space, which is immediately followed by our main application firmware. When we power cycle this first case at 65C the bootloader fails
to boot properly and only toggles a pin controlled by the watchdog. In our second set of firmware we only program the chip with our main application firmware. When we power cycle this second case at 65 C, the firmware
runs just fine with no issue. So my question is, what is to be affected at higher temperatures that would allow some firmware to run and not others. What are common failures at boot at higher temperatures?
Any thoughts would be much appreciated!