Hello, our production line detected that the power supply pin 9 and pin 42 (1.1V power supply pin) of the chip 947 had very small ground resistance (as shown in the figure below) during the automatic test of the PCBA board. Re energize, and the short circuit will return to normal (multiple PCBAs have verified this problem).
Process troubleshooting:
Remove the 947 chip, and measure the resistance to ground of the 9-pin network on the PCB board to 78.8K Ω. At the same time, test the resistance to ground of the 9-pin network of the removed 947 chip to 76.4 Ω (it is still in the short circuit state, because the resistance of the normal chip is generally about 2K Ω), as shown in the following figure;
Please analyze and confirm the following problems in combination with the above assistance:
1. Why does a short circuit occur and why does it return to normal after being powered on again after a short circuit?
2. How to prevent and avoid such problems?
3. Will the subsequent use that has been restored after a short circuit is energized reappear?
4. Is there any potential quality hazard in case of short circuit power on recovery and how to identify it?
