Use screwdrivers and other phone opening tools to disassemble the iPhone XS Max, remove the iPhone XS Max display screen and iPhone battery, and then take out the iPhone XS Max motherboard.
Use SS-T12A heating station to separate the iPhone XS Max motherboard, and then put it on the iSocket test fixture.
Use digital multimeter to measure the resistance value for iPhone XS Max Face ID connector, when we measured the 17 Pin of the infrared camera, we found it had no resistance value, but the value for the 15 Pin was normal, which is why the iPhone XS Face ID doesn't works. The circuit between the iPhone CPU and iPhone infrared camera 17 Pin are virtual-welded or disconnected.
Now we need to remove the glue for iPhone CPU, put iPhone motherboard under a microscope, and then use BGA graver blade to remove the glue around the CPU.
Apply some solder paste around the CPU, and then use hot air gun and BGA graver blade to remove the iPhone CPU. After the iPhone CPU is removed, use soldering iron to handle the residual glue on the solder pad, and then use JBC CD-2SHE soldering iron to solder a jump wire from 17 Pin to test if the circuit between iPhone CPU and iPhone infrared camera 17 Pin are disconnected.
After soldering, measure it with digital multimeter, the data tested is normal, now we confirm that the iPhone CPU is virtually welded, we need to re-install the iPhone CPU.
Reballing the iPhone CPU, and then install the iPhone CPU back to the motherboard. After the motherboard is cooled, use digital multimeter to measure the 17 Pin, now the resistance value is back to normal.
Next, use iSocket test fixture to test it, the iPhone XS Max Face ID tested is normal. Assemble the iPhone XS Max layers, and then install the iPhone XS Max, turn it on, all function tested are normal.