Are you struggling with a Black Shark 3 that just won’t turn on? You’re not alone. Many users experience the frustration of pressing the power button only to face a lifeless screen. Even plugging in the power cable fails to revive the device, leaving you feeling stuck and helpless. But don’t despair; we’ll guide you through some effective troubleshooting steps and repair techniques to bring your phone back to life.
Teléfono
Modelo: Xiaomi Black Shark 3
Anunciado: 2020, March 03
Fenómeno del defecto
The phone won’t turn on when pressing the power button. Plugging in the power cable does not help, and the phone remains dead.
Proceso de resolución de problemas
Desmontaje:
- Place the phone on a heating pad set to 100℃ for 2 minutes to soften the adhesive.
- Insert a plastic card to separate the rear housing, adding alcohol periodically to assist with the separation.
- Be careful not to damage the flex cable when lifting the back cover.
Accessing the Motherboard:
- Remove the shielding cover and screws, and disconnect the flex cable.
- Since the motherboard is fixed to the screen with a screw, heat the screen at 100℃ for about 5 minutes.
- Use a razor blade and plastic card to carefully separate the screen, then disconnect the flex cable to remove the motherboard.
Testing the Motherboard:
- Connect the motherboard to a DC power supply and trigger the boot process with tweezers.
- Observe the boot current, which jumps between 120mA and 240mA, indicating a potential CPU soldering issue.
Reballing the CPU:
- Remove the shielding cover and scrape off the thermal paste.
- Cut a gap in the shielding cover to access the CPU.
- Fix the motherboard on a PCB holder and protect the NAND flash memory chip with high-temperature resistant tape and a coin.
- Remove the black adhesive around the CPU with a specified knife and hot air gun set to 300℃.
- Heat the RAM (upper layer) at 380℃ and gently pry it up when loose. Continue heating to remove the CPU.
Cleaning and Preparing for Reballing:
- Apply medium-temperature solder paste to the PCB pads and neutralize with the original pads using a soldering iron set to 380℃.
- Clean the tin on the bonding pads with solder wick until they are clean and flat.
- Remove any remaining adhesive on the PCB with a specified sculpture knife.
- Clean the CPU core chip and RAM chip using the same method: neutralize the tin, clean with solder wick and hot air gun, and remove adhesive.
Reballing the CPU and RAM:
- Use a stencil and medium-temperature solder paste to form solder balls on the CPU and RAM.
- Apply solder paste flux on the PCB and align the CPU to its proper location.
- Solder the CPU with a hot air gun set to 350℃ and airflow at 100. Gently touch the CPU with tweezers to ensure it is properly positioned.
- Repeat the process to resolder the RAM.
Montaje final y pruebas:
- Apply thermal paste on the CPU surface and reattach the shielding cover.
- Reassemble the motherboard, install a good screen, and press the power button to boot the phone.
- Confirm that the phone turns on and functions normally.
Resumen:
The Black Shark 3’s inability to turn on was resolved by reballing the CPU. After the process, the phone was successfully booted, and all functions were tested to be working correctly.
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