Is it possible to electrically damage a microcontroller (or any chip) in such a way that it becomes very sensitive to mechanical stress?
Some background:
We are developing a board with 7 identical microcontrollers, each running the same motor control firmware. After running without incident for dozens (sometimes hundreds) of hours, the 7th microcontroller starts behaving oddly. Specifically, the output of its internal core voltage regulator begins drifting away from its 1.8v target. Even more strangely, this output voltage now seems sensitive to mechanical stress. Giving the board a slight twist reliably causes this voltage to fluctuate (usually upwards), and become quite choppy.
Extensive probing and measurement has failed to detect any fault in the PCB itself. The decoupling capacitors were removed, measured (with no problems found) and replaced. As far as we can tell, the microcontroller is receiving correct and stable voltages to its power pins, which do not fluctuate when the board is stressed. Fluxing and reflowing the faulty chip does not fix the problem, but replacing the chip does fix it until, after some hours of use, the problems appears in the new chip.
This behaviour has been seen on twice on two boards, always on that 7th same microcontroller.
It looks like there is some kind of problem inside the chip. One hypothesis we are pursuing is a high voltage spike from the motor driver is somehow making its way to that chip and causing subtle damage.
Is it possible to electrically damage a microcontroller (or any chip) in such a way that it becomes very sensitive to mechanical stress?