Water damage can be a major setback for any smartphone, especially when it leads to issues like a non-functional display or inability to boot. If your HUAWEI Mate 40 Pro has encountered water exposure and now refuses to power on or shows display problems, don’t worry—there’s hope for repair. In this guide, we’ll walk you through diagnosing the root cause of water damage, replacing critical components like the display IC, and reflowing the PMIC to bring your device back to life. Whether you’re a technician or a DIY enthusiast, this tutorial will help you get your HUAWEI Mate 40 Pro back in working order.
Device Details
Model: HUAWEI Mate 40 Pro
Announced: 2020, October 22
Defect Phenomenon
The issue began when the phone was used for watching videos while taking a shower, causing water vapor to enter the device. The phone’s display became blurry, and after charging it overnight, it would not power on the next day.
Troubleshooting
The phone likely suffered from water vapor entering its internal components, leading to a short circuit. Here’s the process to identify the problem:
- Screen Test: Separate the motherboard and connect it to a different screen. The replacement screen displays abnormal behavior, indicating a deeper issue.
- Diode Measurement: Use a multimeter to measure the diode values on the display connector; all values are normal.
- Component Check: Inspect the small components around the display PMIC with a multimeter; the diode values appear normal as well.
Repair Process
Even though the diode values around the PMIC were normal, it’s possible the display IC could be faulty. The next step involves replacing the display IC:
- Remove the Original Display IC: Carefully desolder and remove the display IC.
- Clean the PCB Pads: Use a cleaning solution to ensure the PCB pads are free from residue.
- Reball and Solder: Apply fresh solder balls to the new display IC and reattach it to the motherboard.
After reassembling the phone and testing it again, the display issue persisted.
Additional Investigation
Upon further inspection under a microscope, water damage stains were found around the PMIC. It was possible that poor soldering of the PMIC caused the issue. To address this:
- Reflow the PMIC: Apply solder paste flux around the PMIC and reflow the chip.
- Test Again: Reassemble the phone, and this time, the display functions normally.
To ensure a permanent fix, the following steps were taken:
- Remove and Clean the PMIC: Remove the PMIC chip completely and clean the corrosive residue on the PCB pads.
- Reball and Resolder the PMIC: Apply fresh solder and reattach the PMIC.
- Final Testing: After reassembling the phone, all functions, including the display, worked perfectly.
Conclusion
The HUAWEI Mate 40 Pro’s display issue was ultimately caused by poor PMIC soldering due to water damage. By reballing and properly resoldering the PMIC, the phone’s display function was restored. This process ensured that the corrosive damage would not cause future problems. With careful diagnosis and repair, even water-damaged phones like the HUAWEI Mate 40 Pro can be brought back to life, saving time and money.
Tools & Parts List
- Replacement Display IC
- PMIC chip
- Soldering iron and hot air rework station
- Solder paste flux
- Cleaning solution (e.g., isopropyl alcohol)
- Multimeter for diode measurements
- Microscope for inspecting small components
- Reballing kit
