The user experience of high-end phones, such as the iPhone 12 Pro, depends on wireless features like WiFi and Bluetooth operating properly. A problem in the middle layer of the logic board is probably the cause if your iPhone 12 Pro is unable to connect to WiFi and the WiFi switch is grayed out. According to our repair expertise, this issue frequently results from loose or badly soldered solder connections in the middle layer, which hinders the WiFi module's ability to communicate with the logic board. Phonefix will describe expert repair techniques for resolving an iPhone 12 Pro No WiFi problem brought on by a malfunctioning middle layer.
I. Faulty Device and Symptom
· [Faulty Model]: Apple iPhone 12 Pro;
· [System Version]: iOS 17 (the system version has little impact on the problem);
· [Symptom]: The Wi-Fi switch is grayed out and cannot be turned on, and the Wi-Fi address cannot be recognized in the device settings.
Users report that their phone boots up and uses the cellular network normally, but cannot connect to any wireless network. Restarting and restoring the factory settings have been ineffective. This type of problem typically indicates a hardware fault or signal loss.
II. Initial Diagnosis and Basic Troubleshooting
Before officially performing a iPhone motherboard repair, you should first perform basic troubleshooting on the software and external hardware to rule out system anomalies or external factors.
1. Software Check
· First, go to Settings → General → Transfer or Restore iPhone → Restore → Reset Network Settings.
This step will clear all WiFi passwords and network configurations. If the problem is caused by a system cache or configuration error, a reset will usually restore the problem. However, if the WiFi switch remains gray after performing this operation locally, it indicates that the problem is not with the system software.
2. Verify the Router and Environment
Test the router and environment by connecting other devices to the same WiFi network to confirm that the router is functioning properly. If the other devices connect normally, the problem lies with the phone itself.
3. Determine if it is a hardware fault
When the WiFi address is unrecognizable, the system is actually unable to detect the WiFi module. Since the iPhone 12 Pro's WiFi module is located on the lower layer of the motherboard and connected to the middle layer solder joints, it can be preliminarily diagnosed as a hardware failure caused by a missing or poorly soldered joint on the middle layer.
III. Professional Hardware Repair Steps
This section involves in-depth motherboard repair and is only suitable for professionals with micromanipulation and soldering skills. Always wear an anti-static wrist strap and use an anti-static workbench before proceeding.
1. Disassembly Preparation
a. Required Tools:
· Pentalobe screwdriver, Y000 triangular screwdriver;
· Prying pick, suction cup, plastic pick;
· Heating table (temperature controllable);
· Microscope, hot air gun, motherboard layered test fixture;
· Ball placement template, flux, solder balls, tweezers, solder wick;
· Cleaning fluid (such as anhydrous alcohol), anti-static brush;
b. Key Points:
· First remove the bottom screws. Use the suction cup to gently lift the bottom edge of the display, and then use a plastic opening pick to slowly separate along the edge.
· Be sure to disconnect the battery cable before removing the display cable to prevent short circuits.
· Before removing the motherboard, disconnect all connecting cables, including those for the camera, Face ID, display, charging port, and antenna.
2. Motherboard Inspection and Delamination
a. Use a microscope to inspect the back of the motherboard and the connection area between the middle layer. The iPhone 12 Pro motherboard is a stacked structure with numerous micro-solder points (BGA) in the middle connecting the data and power signals.
b. The WiFi module is located on the lower motherboard, near the RF shield. If there are breakages, oxidation, or poor soldering on the middle layer, the WiFi module will not communicate properly, resulting in a gray WiFi display in the system.
c. Inspection Process:
· Test the motherboard with a DC power supply. If the standby current is normal but there is no WiFi, the power supply chip is likely damaged.
· Use a HD trinocular microscope to inspect the middle layer's connection solder points for signs of chipping, dents, or oxidation.
· If missing or broken solder points are confirmed, a layer-by-layer repair is necessary.
The motherboard is now exposed and ready for further inspection.
3. Motherboard Delamination
Key Points:
· Secure the motherboard on the delamination jig and evenly heat it using a heating plate at a temperature of 180-200°C.
· Use a heat gun (approximately 350°C, moderate air speed) to slowly heat the motherboard from the edge. Once the solder softens, gently separate the upper and lower layers with a thin sheet of paper.
· After delamination, do not rush to clean the layers; wait until they cool before working on the solder joints.
At this point, the distribution of the middle solder joints can be clearly seen. Dropped joints are typically concentrated in the signal transmission area, near the WiFi module connector.
4. Dropped joint repair and solder pad treatment
This is the most critical step in the entire repair.
a. Tool Preparation:
· HD trinocular microscope;
· Tweezers, scraper, and flux;
· Solder balls (0.25mm diameter), ball placement template;
· Hot air rework station;
b. Repair Procedure:
Step 1: Cleaning the Pads
· Use a scraper to gently scrape away the oxide layer and old solder residue, exposing the clean copper layer on the pad surface.
· Be careful not to apply excessive force to avoid damaging the circuit.
Step 2: Re-Tinning
· Apply a small amount of flux evenly to the missing solder joints. Use a fine solder wire and soldering iron tips to re-tin the pads, ensuring each solder joint is full and shiny.
· If some pads are severely chipped, use wire leads to re-tin the pads to ensure signal integrity.
Step 3: Re-Bumping
· Place the motherboard under the ball placement template and evenly apply solder balls. Heat until the solder balls melt and adhere to the pads.
· After completion, check that the solder balls are uniform in height to avoid uneven pressure during assembly.
5. Motherboard Assembly and Reassembly
After repairing the middle solder joints, clean any residual flux and re-align the upper and lower motherboards.
Assembly Tips:
· After aligning the registration holes, slowly press the boards together under a microscope.
· Use a hot air gun to heat at medium temperature to help the solder balls re-fuse and ensure a complete and seamless fit between the upper and lower boards.
· After cooling, use a digital multimeter to check the continuity of key signal points to confirm there are no shorts or opens.
Once completed, install the motherboard into the device and reconnect all cables and the battery.
6. Power-on Test
After powering on the device, go to System Settings and check the WiFi switch. If it turns on normally and displays the WiFi address, the repair is successful.
Test Results:
WiFi turns on normally, searching for over a dozen networks, with a stable signal and normal strength. Further testing of Bluetooth, baseband signal, camera, charging, earpiece, microphone, and other functions revealed normal operation.
IV. Precautions and Repair Results
1. Temperature Control:
The temperature must be strictly controlled during the lamination and bonding process. Excessive temperatures can cause the motherboard to warp or chips to detach. It is recommended to keep the temperature below 350°C and heat evenly.
2. Protective Measures:
During repair, use high-temperature resistant tape to protect surrounding sensitive components, such as the Face ID module and RF chip, to prevent damage from heat.
3. Operating Environment:
Operate in an anti-static environment to prevent static electricity from damaging the chip.
4. Testing and Retesting:
After bonding, check the continuity several times to ensure there are no short circuits. Test to see if both WiFi and Bluetooth are restored simultaneously, as they share some signal paths.
5. Repair Conclusion:
The cause of the problem was confirmed to be a loose solder joint in the middle layer of the motherboard, which caused a signal loss in the WiFi module. After lamination, re-spotting, and re-bonding, the device returned to normal operation.
Despite its seeming simplicity, the iPhone 12 Pro Wi-Fi failure is actually a common sign of an issue with the connection between the motherboard layers. It takes professionals with strong soldering abilities, advanced equipment, and stringent operating procedures to fix this kind of issue. Investing in China Phonefix's professional repair tools will enable you to successfully restore gadget functioning without having to pay for a full replacement.
This video demonstrates the iPhone 12 Pro logic board re-balling process:
