Here is an iPhone XR with 4G netowrk problem, 4G signal on the iPhone XR is not stable, it always turns to 2G. How to solve tihs problem?
Use phone opening toosl to disassemble the iPhone XR to remove the iPhone XR motherboard. Observing the iPhone motherboard, we can see that the iPhone baseband part, the medium frequency part and the amplifier IC has been repaired.
Fixed the iPhone XR motherboard by a MJ A22+ PCB fixture, and then remove the iPhone NAND flash. Put it under the Black Trinocular Microscope, use BGA scraper blade to remove the black glue, and then remove the iPhone Nand flash, and then remove the iPhone baseband CPU.
Next we're going to remove the iPhone main CPU. Put iPhone motherboard under a microscope, and then use BGA scraper blade and hot air gun to remove the glue for A12 CPU, and then use medical cotton to clean it. Now use hot air gun to heat the main CPU, after a while, carefully insert a blade, and slide the blade gently to both sides, and then remove the main CPU.
Next we need to remove the logic eeprom IC, as we know, since the iPhone X and later models, the logic eeprom IC is multi-pin, if the logic eeprom IC doesn't been installed, then it will report unknown error 9. Use hot air gun and BGA scraper to remove the logic eeprom IC.
Because the baseband eeprom IC is too small, so we can remove it later. Now we need to install those IC that has been removed previously to the new motherboard.
First install the iPhone Nand flash. Check iPhone Nand flash solder pins, there are 3 solder pins that are grounded, so we can leave them. Remove the glue from the Nand flash, place it to the MJ 3D BGA reballing stencil, apply some solder paste, and then soldering the tin balls on the Nand flash.
After reballing, we need to unbind the WIFI. Use JC PCIE-XR programmer to unbind the WIFI, and then we can install it to the new iPhone motherboard. Apply some solder paste to the solder pad, use DES H95 rework station to install the iPhone XR nand flash to the new motherboard.
Now we need to reballing iPhone basebande CPU and iPhone logic eeprom IC. After reballing, we need to handle the iPhone main CPU. Use hot air gun to solder the tin, clean it, and then reball it.
Install the A12 CPU on the new motherboard. Put main CPU on the right position by tweezers, and then use hot air gun to heat it. When the solder oil overflows, gently push the CPU with a Titanium Alloy Tweezers to see if it is reset, if it can reset, then we can stop heating.
Next install the iPhone logic eeprom IC and iPhone baseband CPU on the new motherboard.
Now we need to remove the iPhone baseband eeprom IC from the old motherboard, and then install it to the new motherboard.
At last, test the iPhone XR 4G network, it's working perfectly.
Use phone opening toosl to disassemble the iPhone XR to remove the iPhone XR motherboard. Observing the iPhone motherboard, we can see that the iPhone baseband part, the medium frequency part and the amplifier IC has been repaired.
Fixed the iPhone XR motherboard by a MJ A22+ PCB fixture, and then remove the iPhone NAND flash. Put it under the Black Trinocular Microscope, use BGA scraper blade to remove the black glue, and then remove the iPhone Nand flash, and then remove the iPhone baseband CPU.
Next we're going to remove the iPhone main CPU. Put iPhone motherboard under a microscope, and then use BGA scraper blade and hot air gun to remove the glue for A12 CPU, and then use medical cotton to clean it. Now use hot air gun to heat the main CPU, after a while, carefully insert a blade, and slide the blade gently to both sides, and then remove the main CPU.
Next we need to remove the logic eeprom IC, as we know, since the iPhone X and later models, the logic eeprom IC is multi-pin, if the logic eeprom IC doesn't been installed, then it will report unknown error 9. Use hot air gun and BGA scraper to remove the logic eeprom IC.
Because the baseband eeprom IC is too small, so we can remove it later. Now we need to install those IC that has been removed previously to the new motherboard.
First install the iPhone Nand flash. Check iPhone Nand flash solder pins, there are 3 solder pins that are grounded, so we can leave them. Remove the glue from the Nand flash, place it to the MJ 3D BGA reballing stencil, apply some solder paste, and then soldering the tin balls on the Nand flash.
After reballing, we need to unbind the WIFI. Use JC PCIE-XR programmer to unbind the WIFI, and then we can install it to the new iPhone motherboard. Apply some solder paste to the solder pad, use DES H95 rework station to install the iPhone XR nand flash to the new motherboard.
Now we need to reballing iPhone basebande CPU and iPhone logic eeprom IC. After reballing, we need to handle the iPhone main CPU. Use hot air gun to solder the tin, clean it, and then reball it.
Install the A12 CPU on the new motherboard. Put main CPU on the right position by tweezers, and then use hot air gun to heat it. When the solder oil overflows, gently push the CPU with a Titanium Alloy Tweezers to see if it is reset, if it can reset, then we can stop heating.
Next install the iPhone logic eeprom IC and iPhone baseband CPU on the new motherboard.
Now we need to remove the iPhone baseband eeprom IC from the old motherboard, and then install it to the new motherboard.
At last, test the iPhone XR 4G network, it's working perfectly.
