Use screwdriver to remove the screws next the iPhone lightning port, and then use CPB screen separator to heat the iPhone XS display screen. After a while, we can open the iPhone display screen easily.
Use Rigol DP832 Oscilloscope to measure the iPhone current, when press the iPhone power button, the current instantly reaches more than 800mA, and then drops to 0mA immediately.
Use digital multimeter to measure the circuit of the power supply, we found the PP1V1_S2 is short circuited.
After checking the iPhone XS schematic diagram via ZXW online account, we need to measure the capacitors on the PP1V1_S2 circuit. After measurement, we know that those capacitors are normal. Therefore, we suspect the problem is between the iPhone CPU and the iPhone motherboard, the iPhone CPU tin balls may have broken, and then cause the PP1V1_S2 short circuit.
Attach the iPhone XS motherboard upper layer to the SS-601K Tinning Fixture, apply some solder paste around the iPhone CPU, and then use BGA removal blade and hot air gun to remove the iPhone CPU.
Next, put MJ 3D BGA reballing stencil on the iPhone CPU; apply some Mechanic solder paste to the BGA reballing stencil, and then use hot air gun to reball it.
After reballing, apply some solder paste on the iPhone motherboard, and then put iPhone CPU on the right position, use DES H95 Soldering Station to solder it back the iPhone motherboard.
Install the iPhone motherboard upper layer and lower layer, and then assemble the iPhone XS. Press the iPhone power button, the iPhone XS boots successfully. After entering the iOS system, test the iPhone functions, all works well, the iPhone XS boot failure has been fixed.
Hope the above repair methods are helpful to you. If you have other questions about the iPhone, please leave a comment in the comments.