Gaming enthusiasts often rely on their devices to deliver an uninterrupted experience, but what happens when your OPPO Find X3 Pro unexpectedly displays a black screen mid-game? This frustrating scenario can signal a serious issue, and for one user, it led to a diagnosis of CPU pseudo-soldering and a recommendation to replace the motherboard. With important data at stake, the decision was made to seek repair services elsewhere rather than opt for costly replacements. In this blog post, we’ll explore the common causes of screen failures in Oppo Find X3 Pro and troubleshoot.
Phone Details
Model: Oppo Find X3 Pro
Announced: 2021, March 11
Defect Phenomenon
The phone screen went black while I was gaming, and now it won’t turn on. I sent it to the official repair center, and they diagnosed it as having a CPU pseudo-soldering issue. Luckily, the phone is still under warranty so they can replace the motherboard with a new one. However, important things are stored on the phone, so I’m thinking carefully about whether to send it to their repair shop for a fix.
Troubleshooting Process
Disassemble and Inspect:
- Disassemble the phone and carefully inspect the internals for any signs of water or drop damage. None were found.
- The issue is likely due to CPU pseudo soldering, as initially diagnosed by the official repair center.
Initial Checks:
- Ensure there is no short on the positive power supply side.
- Connect the phone to a DC power supply and trigger the boot process. The boot current is fixed at 100mA, indicating an issue with the CPU.
Note: This kind of fix at 100mA indicates that defects are likely caused by the CPU. Find X3 Pro with Snapdragon 888 CPU gets very hot and causes poor soldering. It is also a common problem with Android phones.
Resolder the CPU:
- Fix the motherboard on a PCB holder.
- Heat the motherboard with a hot air gun to remove the shielding cover.
- Remove the thermal grease on the CPU.
- Clean the black glue around the CPU chip.
- Continue heating until a blade knife can be inserted into the gap. Pry up the upper layer (RAM).
Remove and Clean the CPU:
- Remove the glue and tin on the surface of the core CPU with a soldering iron, solder wick, and solder paste.
- Continue heating the lower layer core CPU and remove the chip when the tin is melted.
- Clean the glue and tin on the PCB pads.
Neutralize Tin Pads:
- Neutralize the tin pads on the PCB with medium-temperature solder paste.
- Clean off the solder paste with a solder wick and soldering iron.
Reball the CPU and RAM Chip:
- Clean the residual glue and tin on the chip.
- Reball the chips using a stencil.
Resolder the CPU and RAM:
- Heat with a hot air gun to solder the core CPU, and then solder the RAM layer using the same process.
- Apply a little solder paste flux on the PCB board.
- Align the chip to the proper location.
Cool down the motherboard, then connect with the DC power supply and trigger the boot process with tweezers, the boot current came back to normal.
Final Assembly and Testing:
- Allow the motherboard to cool down.
- Connect the motherboard to the DC power supply and trigger the boot process with tweezers. The boot current should return to normal.
- Assemble the phone and test all functions to ensure they are working correctly.
Summary
The black screen issue on the OPPO Find X3 Pro was caused by pseudo soldering of the CPU. By carefully resoldering the CPU and RAM chips, the phone was successfully repaired without losing any important data.
