Did you ever experiance a situation in which once the controller is powered, it look like there is some short inside the chip and I get a samll hole in the case and the controlle is dead and it is a short to the board ?

[FSHAI.1]

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[S.Ma]

Not so far. If you apply wrong voltages/ground to the package pinout, you may be able to destroy any electronic chip. To check if a pin is still connected to the chip, you may use a multimeter in diod check mode between a pin and ground for example.

[Tesla DeLorean]

If you create a conduction path through the chip, the bond wires can typically carry quite a lot of current, certainly enough to burn holes and melt plastic.

If this is happening a lot, I'd look carefully at the design.

[FSHAI.1]

Hi Tesla,

Thnaks, the thing is that I've assembled already 10 boards in which everything was fine, then somthing happend while bring up with one of the boards and I've notices the controller is not working so I've replaced it with a new one and when powering it up it blowed. If for some reason one of the controller inputs is connected directly to 5V (one of the buffres become a "short") Can it cause the ST to "burn" ?

Thnaks Shai

[Bob S]

Which CPU are you using?

Depends on which pin and which STM32 part. Most pins are 5V tolerant, though NOT with 5V applied before the CPU has 3.3V power (typically the max voltage spec is VCC+4V, or something like that).

But is the pin is shorted to 5V and then configured as an output - that might damage the chip. But that assumes you were able to load firmware. On an un-programmed part, the internal bootloader will run, but that doesn't typically enable output pins and drive them low. It DOES enable output pins and drive them high (UART pins, for example). So if those pins were shorted to GND it might damage the part. See AN2606 for the pins used by the bootloader for your CPU.

Pull the 2nd blown CPU then check all the connections to the CPU for suspicious voltages or hard shorts to GND.

[Bob S]

Could the CPUs (or some other component) have been installed in the wrong orientation? No tlikely if buid on pick-n-place equipment, unless someone hand-loaded the parts into the tape.