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Introduzione

This is a real-life repair case from REWA chip-level motherboard repair service. The iPhone X motherboard was severely damaged with a hole in the upper layer during the reassembling process, resulted in an iPhone X won’t turn on issue. Follow our guidance in the guide today and learn how to diagnose and troubleshoot the double-stacked motherboard step by step.

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  1. Connect the battery connector with the DC Power Supply. The boot current reading is larger than normal value.
    • Connect the battery connector with the DC Power Supply. The boot current reading is larger than normal value.

    • Run diode mode measurement of the battery connector. The measured value of Pin 1 is 11, which is abnormal. The measured value of Pin 35 of the display connector J5700 is also abnormal.

    • We can confirm now that the main power supply circuits of the motherboard have shorted or the motherboard is leaking electricity.

  2. Next, we need to separate the motherboard to confirm whether the fault is related to the upper layer or the lower layer.
    • Next, we need to separate the motherboard to confirm whether the fault is related to the upper layer or the lower layer.

    • Check the upper layer under the microscope. We can see clearly that the charging IC U3300 is damaged.

    • Remove the charging IC. We can see that the PCB has also been severely damaged. There is a large hole in the upper layer.

  3. The upper layer has been badly damaged and cannot be repaired anymore. We need to transplant CPU, EEPROM, and NAND on the upper layer onto a new upper layer.
    • The upper layer has been badly damaged and cannot be repaired anymore. We need to transplant CPU, EEPROM, and NAND on the upper layer onto a new upper layer.

    • Here we recommend using a specialized upper layer with CPU, EEPROM, and NAND previously removed.

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  5. Remove NAND first, then CPU, and then EEPROM. Once done, clean CPU, then NAND, and then EEPROM.
    • Remove NAND first, then CPU, and then EEPROM.

    • Once done, clean CPU, then NAND, and then EEPROM.

  6. Now we need to reball CPU, NAND, and EEPROM one by one.
    • Now we need to reball CPU, NAND, and EEPROM one by one.

    • Once done, clean corresponding bonding pads on the new upper layer.

  7. Now we need to solder the reballing finished CPU, EEPROM and NAND to the new upper layer one by one.
    • Now we need to solder the reballing finished CPU, EEPROM and NAND to the new upper layer one by one.

  8. Attach the upper layer and the lower layer to the Test Fixture. Connect the upper layer and the lower layer with the display assembly.
    • Attach the upper layer and the lower layer to the Test Fixture. Connect the upper layer and the lower layer with the display assembly.

    • Connect the battery connector with the DC Power Supply. Get the motherboard powered on with tweezers. The phone turns on normally and can get access to the home screen.

  9. Next thing we do is to solder the two layers together. First, we need to reball the lower layer.
    • Next thing we do is to solder the two layers together. First, we need to reball the lower layer.

    • Continue to apply some BGA paste flux to the third space PCB. Get the upper layer in position. Turn on the power switch of the heating platform.

    • Now we can assemble the phone and test.

Un'altra persona ha completato questa guida.

Phryne

Membro da: 17/11/2019

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