STM32G070CBT6 IC pins shorted internally

[patrick-reddesigns]

Hi,

I have made up six boards and three of them had an unusually high standby current (35mA instead of 1mA).

Eventually, when the IC was removed, we found Pins 5 & 6 of the removed IC were shorted internally (0.3R)
They were also shorted to pin 45 with 3.7R. The other two boards are showing similar shorts.

The board worked fine with a new MCU.

Does anyone know what might cause this short?

TIA,

Patrick.

[TDK]

> STM32G070CB76 

Not a chip. Probably STM32G070CBT6?

Pins shorted indicates hardware damage. Probably due to overvoltage at one point. Does L3 cause VREF+ to spike at powerup? What is attached to LED_WHITE?

[patrick-reddesigns]

Thanks, typo in chip code corrected to STM32G070CBT6.

LED_WHITE connects through a resistor to a led.

VREF+.. I don't know - some kind of intermittent event? These are the second batch of boards - the first 10 had no issues with hundreds/thousands of power-ups.

Could ESD be an issue?

[CTapp.1]

Yep, it could be ESD.

[TDK]

ESD could always be a cause of a hardware failure, but in my experience it's typically something else. These chips aren't particularly sensitive to ESD.

[patrick-reddesigns]

Thanks TDK,

Thats good to know before I get on to the assembly house about their ESD prevention measures - they tend to be very touchy (pun intended) about that :)

I suppose I was hoping that someone from ST with an intimate knowledge of the inner workings of the IC could come back with a "This failure can only be caused by a spike on pin X" type reply.

Regards,

Patrick.

[Andreas Schweigstill]

We are using the STM32G070CBT6 in several products and have never experienced any problems. But in out most recent production lot 7 out of 100 boards have failed the production test. Two STM32 have a far too high current (30 mA of ~9 mA), and on five boards VREF (pin 5) in shorted to GND (pin 7) with a resistance of 1,5 ohms.

The boards have been assembled at JLCPCB, the production test (including electrical test and firmware programming) has been performed at our location.

This is the fifth production lot of this board, so any problems with the board should have occured earlier.

The +3.3 V supply for the STM32 is generated by HT7533-1 and has an RC filter (33 ohms, 10 µF) at its input stage and pi filter (100 nF, 1 ohms, 10 µF) at its output, so there isn't any chance of ringing or similar events which can generate voltage spikes. Of course I have checked all relevant signals on our board for ringing and oscillations.

[TDK]

@Andreas Schweigstill Please make a new thread if this is a separate issue. Your board does not match OPs.