short pp_gpu after cheng ic u4000

Are you certain PP_GPU is shorted? It’s a very low resistance line and will cause all multimeters to beep when checking in continuity mode. You have to look at the measurements and insure it is truly a ~0 Ohm short.

As for the PMIC, it is rarely the problem and should only be removed once all other possibilities have been examined and eliminated. When shorts are on the main lines like GPU/CPU/SDRAM, you can always remove the coils to determine if the short is on the PMIC side or downstream.

As a side note, I feel that your air temperature is too low at 260C. You should be operating at around 340 -380C. The reason is that most hot air stations are not properly calibrated and are usually running much lower than what is displayed. In addition, the distance you have between the nozzle and the pcb causes the air to cool. So you have to leave the hot air on the IC much longer when using a low temperature than when using a higher temperature. That means that most of the board will have time to heat up and this could cause shorts or bridges elsewhere.