I recently designed custom hardware with PSoC as the main processor. Until the latest iteration I had no problems whatsoever. However, in this iteration, the hardware was perfectly working for a week and then 4 out of 5 boards randomly stopped working. The issue I found was that the PSoC was shorting Vcc and GND. I did a lot of debugging and analysis and then arrived at this conclusion. Initially I thought it was an issue with soldering. I ruled that out by removing all the components one by one and I was only left with the PSoC on the PCB and the short still existed. Once I removed the PSoC the short was no longer there. All the 4 boards had the exact same issue. Given below are my tests and observations
1. I took the bad IC and put it on a new PCB. Vcc and GND started shorting there as well. That confirmed it was the PSoC causing the issue.
2. I took a new IC and put in the old board which was initially shorting. There was no shorting anymore and the PCB started working again. This also confirmed that PSoC was causing the issue.
3. I put the working PCB through a 24 hour test where it was continuously ON. The PCB draws about 140mA when fully functional. I wanted to see if the board gets overheated and the shorts were being caused due to that. But that wasn't the case. It successfully passed the test. The board was barely warm and it was properly working after that.
4. I put the same PCB through a power cycling test. I switched on the supply for 30 seconds and then switched it off for 15 seconds. This pattern was continued for 24 hours. I was expecting some power surge or the frequent power discontinuities to have killed the PSoC. But it passed this test as well and the board is still working.
5. I put it through an intense power cycling test for 1 hour. Here, I turned the supply on for 500ms and off for 500ms. This pattern was continued for 1 hour. The board was fully functional after this test too!
6. I put the PCB through some violent motion to see if the mechanical stress and shock created the shorts. But that wasn't the case either. The PCB was fully functional after this test too!
So in conclusion, I think I have ruled out thermal, power and mechanical stress/shock issues. What is the most likely reason for an issue like this where everything is fine for a week or so and then suddenly stops working?
Please help me debug this issue. I am clueless at this point.