iPhone 12 Serious Crack Damage Cannot Boot
Model: iPhone 12
Announced: 2020, October 13
Defect Phenomenon
iPhone gets seriously drop damage, both the screen and back cover glass have cracked into pieces.
Disassemble the phone and take out the motherboard
Then try to boot with the DC power supply connected, but the boot current is fixed at around 70mA.
Troubleshooting
Heat the motherboard on the heating platform to separate the two layers.
After separating, we can see there are some pads missing. Besides this, everything looks fine.
When checking the NAND chip under the microscope we can see there is a little crack on the edge
For no boot issue and the trigger to boot current fixed at around 70mA, normally is caused by the NAND chip or the CPU. Is that possible it’s the NAND chip damage that caused the no boot issue?
Anyway, let’s remove the NAND chip from the motherboard first.
- Remove the black glue around the NAND chip with a sculpture knife and hot air gun slightly
- Heat the whole NAND on the surface evenly, when tins get melt insert the blade knife to pry it up
After removing the NAND we can see the board get deformed seriously, just like a seesaw…
Normally, the motherboard without NAND can still connect with iTunes or 3UTools successfully. But this phone cannot connect with the PC? Is it the CPU problem…
Let’s continue to remove the CPU chip carefully, it’s lucky the CPU looks very good, with no crack, no pad missing, etc.
We can continue to clean the glue on the CPU pads and resolder the CPU.
Repair Process
Since the phone drop damaged very seriously, the board also get deformed. So it might be the inner rail broken issue, we’ll try to swap the CPU, NAND, and logic EEPROM to a new board.
Swap the NAND, CPU, and logic EEPROM one by one, then the upper layer (logic board) chip swapping is finished. Connect with the DC power supply and trigger to boot, it can be booted normally.
The logic board repair is finished.
Then we will also need to swap the Baseband CPU and Wi-Fi chip to the new signal board in the same way.
Then connect the two layers of the board with the motherboard layered temporary test fixture to test. The phone can boot normally.
In the last step, we just need to recombine the two layers of the motherboard, then assemble the whole cellphone and test the functions again. Every function works fine, and the iPhone 12 cannot boot issue finally gets fixed by the encrypted chip swapping.