How To Fix iPhone 8 Plus WiFi Not Working In Three Steps

REWA 04/23/2020

In most cases, iPhone grayed-out WiFi switch issue is caused by damage of the WiFi module. And we need to replace the WiFi module to fix the problem. What’s more, the WiFi module is bound up with WiFi address stored in the NAND flash chip. When replacing the WiFi module, there is one indispensable step as WiFi unbinding. How to successfully replace the WiFi module and complete WiFi unbinding in four steps? Follow our repair guide now!

Problem 

Press the power button to turn on the phone. The phone turns on normally. Go to Settings>WiFi. The WiFi switch cannot be toggled.Press the power button to turn on the phone. The phone turns on normally. Go to Settings>WiFi. The WiFi switch cannot be toggled.

Take apart the phone and remove the display assembly. Disconnect the battery and take out the logic board. Then tear off the shielding sticker.

Diagnosis

The first thing we do is to check working conditions of the WiFi module. Run diode mode measurement of the three rails of power supply. Nothing goes wrong. Judging by this, WiFi relevant circuits have not open-circuited or short-circuited.The first thing we do is to check working conditions of the WiFi module. Run diode mode measurement of the three rails of power supply. Nothing goes wrong. Judging by this, WiFi relevant circuits have not open-circuited or short-circuited.

Continue to measure the working voltage of the WiFi module. Connect the battery connector with the DC Power Supply and short Pin 8 of J4300 to the ground with tweezers. The system will then detect power button press. Switch the Multimeter to the voltage mode and run voltage measurement of the three rails of power supply. The measured voltage value of SR_LVX_W is 1.22V, which is abnormal. Normal voltage value should be 1.35V.Continue to measure the working voltage of the WiFi module. Connect the battery connector with the DC Power Supply and short Pin 8 of J4300 to the ground with tweezers. The system will then detect power button press. Switch the Multimeter to the voltage mode and run voltage measurement of the three rails of power supply. The measured voltage value of SR_LVX_W is 1.22V, which is abnormal. Normal voltage value should be 1.35V.

SR_LVX_W is the internal power supply circuit of the WiFi module. The abnormal voltage value indicates that the WiFi module has malfunctioned. So we need to replace with a new WiFi module.

Troubleshooting

Attach the logic board to the PCB Holder. Remove black adhesive around the WiFi module. Then heat with the Hot Air Gun and pry up the WiFi module with the Sculpture Knife.

Continue to apply some Paste Flux to the bonding pad. And then some middle-temperature solder paste. Heat with the Soldering Iron to neutralize the melting temperature on the bonding pad and clean the bonding pad with rosin soaked Solder Wick. Clean with PCB Cleaner afterwards.Continue to apply some Paste Flux to the bonding pad. And then some middle-temperature solder paste. Heat with the Soldering Iron to neutralize the melting temperature on the bonding pad and clean the bonding pad with rosin soaked Solder Wick. Clean with PCB Cleaner afterwards.

Note 

The WiFi module is bound up with WiFi address stored in the NAND flash chip. When replacing the WiFi module, here we have one indispensable step as WiFi unbinding. A PCIE programmer is needed in this step.PCIE NAND Flash Memory Chip Programmer For iPhone8/8 Plus/XThe WiFi module is bound up with WiFi address stored in the NAND flash chip. When replacing the WiFi module, here we have one indispensable step as WiFi unbinding. A PCIE programmer is needed in this step.PCIE NAND Flash Memory Chip Programmer For iPhone8/8 Plus/X

WiFi Unbinding

Heat with the QUICK 990AD Hot Air Gun to remove black adhesive around the NAND flash chip. Since there are multiple components around the NAND flash chip, to protect these components from high-temperature damage, we need to provide heat insulation by placing a coin.Heat with the QUICK 990AD Hot Air Gun to remove black adhesive around the NAND flash chip. Since there are multiple components around the NAND flash chip, to protect these components from high-temperature damage, we need to provide heat insulation by placing a coin.

Once the NAND flash chip has been removed, continue to apply some Paste Flux to the bonding pad and then some middle-temperature solder paste. Heat with the Soldering Iron to neutralize the melting temperature on the bonding pad.

Continue to apply Paste Flux to the detached NAND flash chip and clean the NAND flash chip with the Soldering Iron. Place the NAND flash chip into the PCIE Programmer and run the software to complete WiFi unbinding. Once done, take out the NAND flash chip.Continue to apply Paste Flux to the detached NAND flash chip and clean the NAND flash chip with the Soldering Iron. Place the NAND flash chip into the PCIE Programmer and run the software to complete WiFi unbinding. Once done, take out the NAND flash chip.

NAND Reballing

Next, we need to reball the NAND flash chip. Get the BGA Reballing Stencil well aligned with the chip. Smear Soldering Paste evenly on the BGA reballing stencil and then heat evenly with the QUICK 990AD Hot Air Gun so that all solder balls can solidify completely.Next, we need to reball the NAND flash chip. Get the BGA Reballing Stencil well aligned with the chip. Smear Soldering Paste evenly on the BGA reballing stencil and then heat evenly with the QUICK 990AD Hot Air Gun so that all solder balls can solidify completely.

Once done, separate the chip from the BGA reballing stencil and clean the NAND flash chip with PCB Cleaner afterwards.

Chip Soldering

Now we can solder the NAND flash chip and a new WiFi module onto the board.

Apply some Paste Flux to the bonding pad. Get the NAND flash chip in position. Make sure you put it in the right direction. Solder with the QUICK 990AD Hot Air Gun.Now we can solder the NAND flash chip and a new WiFi module onto the board.Apply some Paste Flux to the bonding pad. Get the NAND flash chip in position. Make sure you put it in the right direction. Solder with the QUICK 990AD Hot Air Gun.

Continue to apply Paste Flux to the bonding pad of the WiFi module and get a new WiFi module in position. Solder with the QUICK 990AD Hot Air Gun afterwards.

Reassemble And Test

Now we can assemble the phone and test. Get the logic board and display assembly installed. Connect the battery and press the power button .

The phone turns on normally.

Now we can assemble the phone and test. Get the logic board and display assembly installed. Connect the battery and press the power button . The phone turns on normally.

Go to Settings>WiFi. The WiFi switch is back to normal. Networks in range can be picked normally. Fault cleared.

Tools Used

Hot Air Gun Rework Station – 990AD

Integrated Repair Platform

Digital Multimeter

Communication Maintenance Power Supply

Electron Microscope 

PCIE NAND Flash Memory Chip Programmer For iPhone8/8 Plus/X

Free Schematic Software: Refox

Visit our online shop for more parts and tools.

You can also visit REWA YouTube Channel to check our video and learn how to repair the iPhone 8 plus wifi not working issue step by step.

 


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