How to Fix iPhone XS Unresponsive Touch Screen

Initiating the repair process with step one.Begin by inspecting the motherboard meticulously; confirm its physical integrity, verifying the absence of any warping or signs of water exposure.

• Proceed with mounting the motherboard for a preliminary test; establish a display connection and attach the battery, then power on the device. The touchscreen functionality is currently unresponsive.
• Subsequently, evaluate the touch connector's electrical characteristics; a measurement reveals an open circuit on pin 21, signifying a malfunction within the circuit associated with that pin.

Proceed to step 2.Access the bitmap; observe that pin 21 is linked to resistor R5842. This safety resistor has both terminals joined together.

• It is essential to evaluate the resistor's condition through measurement to determine if it has failed.

Secure the motherboard within the holding fixture, then apply heat using a Hot Air Gun, maintaining a temperature of 260 °C and an airflow setting of 2, to eliminate the black adhesive.

• Utilize a multimeter to perform the measurement; since the resistor exhibits a functional state, we can conclude that the resistor is not the source of the problem, indicating a potential fault within the circuit located on the internal layer.

Procedure 3:Following this, detach the motherboard and position it on a 160 °C heating platform for approximately one minute of exposure to heat.

• Utilizing tweezers, carefully extract the logic board and signal board, noting the prior separation of the motherboard.

Access the bitmap to observe that the resistor's opposing terminal is linked to the power IC via an internal layer.

• Consequently, it is essential to initially assess the electrical circuit on the logic board, verifying that the resistance value is within the expected range.

Subsequently, evaluate the circuit connecting the signal board and the touch connector, confirming a resistance value of 1.

Proceed to step four.An interruption exists within the electrical pathway; restore continuity by creating a direct connection with a wire.

• To facilitate soldering, apply a flux agent to the resistor's surface. Utilize a soldering iron, heated to 360 degrees Celsius, to securely attach the copper wire to the resistor.

Given the significant distance between the connection points, initially secure the copper wire in place.

• Subsequently, apply a protective coating of solder mask to the remaining copper wire.

Trim the excess copper wire and then solder one end to the signal board. Verify the connection using a multimeter; a resistance reading of zero confirms electrical continuity between the touch connector and the signal board.

• Apply a layer of solder mask to protect the signal board's pads, allowing them to harden; then, carefully remove the excess material to expose the pads, and finally, cleanse the bonding pads with a specialized PCB cleaning solution.

Procedure 5:Reattach the signal board to the logic board, ensuring precise alignment.

• Position the signal board onto the160 °C Heating Platformfor thermal processing.
• Apply a thin layer of Paste Flux to the bonding area.
• Secure the logic board in its correct location and use tweezers to apply light pressure while the heating process continues; after approximately one minute, remove the motherboard from the platform.

Once the motherboard has completely cooled, verify the resistance value at pin 21 of the connector; it should return to its expected level.
Reinstall the motherboard and perform a functional test to confirm proper touch screen operation.