iPhone 12 issue repair, a small issue caused the more serious issue, it’s just like a headache boom for the repair technician.
Defect Phenomenon
After the drop damage, the flash function stop working.
Send to a repair shop to fix, the previous repair technician first replaced another flash flex cable to test, the issue still remains unresolved. Then preliminary judge it’s the motherboard problem, so tried to desolder and separate the two layers of the motherboard to test. After separation find both the Baseband and Wi-Fi function were failed.
Troubleshooting
Received the phone with the motherboard separated.
Is it possible the issues are caused by the poor connection of the two layers of the motherboard?
Let’s get the two layers of the motherboard well aligned on the heating platform, then set the proper temperature and turn on to heat to recombine the two layers of the motherboard.
After recombination, assemble the phone to have a test, and the flash LED function back to normal.
But the Wi-Fi and Baseband function still not working, it seems that the issue is not so easy to be fixed.
Separate the motherboard again and check the motherboard, since it’s the Wi-Fi and the Baseband function abnormal, let’s carefully check the signal board first. The Wi-Fi and Baseband chip have not been fixed before
When we continue to check the lower part of the motherboard, find some abnormal
Zoom in to have a check, there are a lot of tin balls
The issue should be caused by the tin pads causing some bridge connection.
Repair Process
Remove the chips at the bottom part one by one.
Then the tins under the chips can be cleaned thoroughly and easily.
After cleaning the pads on the PCB, let’s solder back the chips
Test the function on the test fixture to see if the Wi-Fi and Baseband Function back to normal or not
Type *#06#, we can see the device information, Wi-Fi button also back to normal.
The issue gets fixed by resoldering the chips at the bottom side of the logic board.
Lesson learned
Form a good repair habit, and avoid “polluting” the motherboard with extra tin balls, paste, or flux.