iPhone 12 Pro Max no boot issue fixed by CPU repair.
Model: iPhone 12 Pro Max
Announced: 2020, October 13
Repair Process
Disassemble the phone and find the motherboard has been separated already. It was repaired by another repair technician and the no boot issue cannot be fixed.
As per the customer’s feedback, the CPU with some pads missing problem.
Remove the CPU and check under the microscope.
As we can see, there do have some repair traces on the CPU pads.
So the previous repair technician might have tried his best, but cannot get the issue fixed.
Let’s fix these pads again!
And among the missing pads, the marked 3 pads are the most difficult to repair
- they are useful pads
- they are too close to each other, later when jumping wire requires very skillful handwork and great patient
First, remove the solidified UV mask on the pads carefully.
After removing the UV mask, the root of the pads cannot be found. (This might be the reason why the previous repair technician give up repairing)
keep slightly scratching with the sculpture knife till we can see a little pad as marked below
Finish the job of “Root” searching patiently
Then apply a little bit of solder flux and solidify the roots and the pads first, then cure with the UV lamp
After that, scratch out the roots.
Then apply a very little bit of tin paste to each root
Don’t underestimate these little roots, they are the new connections between the CPU and the motherboard
Then let’s jump wires like what we do on the motherboard
- Solder one side of the wire with the root
- Make a little circle with the tweezer on the other side
- Apply with the UV mask then cure with the UV lamp
- Scratch out the pads slightly
Also, jump wires on the other missing pads
When all the missing pads on the CPU are fixed by jumping wire, then reball the CPU and solder it back to the motherboard. (you can visit REWA Academy to learn the handwork skills)
The last step, recombine the two layers of the motherboard with the heating platform and assemble the phone to test. The phone can be booted normally, and all the functions are OK.
Summary
The issue finally gets fixed by CPU pads jump wire repair. As mentioned, CPU chip missing pad repair requires rich experienced, excellent stable handwork, and great patience.
Do more practice and then you can repair similar issues like this with confidence.