> Is it really just the PCB itself initiating the burn? In my experience it is always a component failure that initiates a burn - but having said that I have had a backplane PCB that had an intermittent short in it, on a minicomputer. But that short caused something else to give up, not the backplane.
I've not seen any cases where the PCB itself failed, it was always
initiated by a component failure.
The thing is that surprisingly low energy levels (<0.5W average) can
cause the component package to degrade, then to arc, and once that
happens, the arc easily transfers to the PCB.