How to fix an iPhone 11 flashing problem that doesn't progress past 80%?

During Apple phone repairs, an iPhone 11 flashing problem that doesn't progress past 80% is a common yet often overlooked issue. Users often encounter the iPhone 11 repeatedly rebooting after the Apple logo appears during daily use. When attempting to restore the device, they find the progress stuck at 80%, unable to complete. This can be frustrating. In this article, Phonefix will use a real-world repair case as an example, explaining the problem, analysis, and repair process.

I. Description of the Problem

This iPhone 11 was sent in for repair by a customer. The customer reported that the device automatically rebooted after the white Apple logo appeared during normal use. Attempts to flash the device using iTunes or 3uTools via a computer were consistently stuck at approximately 80%, with the system stating that the flashing failed and the restore could not be completed.

This problem occurs on multiple devices, with the common denominator being that the baseband firmware failed to load during the flashing process, preventing the device from being written to and activated.

II. Preliminary Diagnosis and Analysis

After receiving the device, we first performed a standard flashing test to replicate the issue and obtain more detailed error information. The flashing result again stopped at 80%. Based on experience and the software prompts, we determined that the iPhone baseband firmware flashing had failed.

Assuming the device had not been exposed to water or dropped, the likelihood of hardware damage was relatively low. Therefore, we primarily suspected a cold solder joint in the middle layer of the iPhone motherboard. 

This means that the solder joints between the upper and lower layers of the motherboard had slightly fallen off or had poor contact, preventing the baseband circuit from fully connecting, making it impossible for the device to recognize the baseband during the flashing process.

In this case, even if the baseband chip itself is intact, the circuit disconnection would prevent it from functioning, resulting in a flashing failure.

III. Detailed Repair Steps

1. Disassembly and Motherboard Separation

First, power off the device and disassemble it, removing the motherboard and preparing to separate the upper and lower layers. The iPhone 11 uses a stacked dual-layer motherboard design, with key chips such as the baseband, power supply, and storage located on the upper and lower layers, connected by solder points in the middle for signal and power.

Use a heating platform to evenly heat the motherboard to the appropriate temperature, typically between 150-170°C, to ensure that the chips and solder joints on the motherboard are not damaged.

Next, use a HD trinocular microscope blade and plastic opening pick to carefully separate the upper and lower layers of the motherboard. Be careful to control force throughout this process to avoid breaking the cables or scratching the motherboard surface. After separation, focus on inspecting the middle layer for loose solder joints, cold solder joints, or any other signs of solder joints.

2. Cleaning the Solder Pads and Re-Laminating

After confirming any solder joint abnormalities, clean the motherboard pads with flux and perform light repairs with a soldering iron or heat gun. Then, re-align the upper and lower motherboard layers on a clean lamination platform. This process is crucial; the lamination must be precise and all solder joints must be properly fused. Even the slightest deviation can result in a short circuit or malfunction on the motherboard.

Use a hot air gun to evenly heat the assembled motherboard to re-melt the solder joints and form a secure connection. This entire operation should be performed under a HD trinocular microscope to ensure that all solder joints are properly aligned. After lamination, allow the motherboard to cool naturally to room temperature.

3. Re-Flash Test

After the assembly is complete and the initial inspection is complete, connect the motherboard to the computer and re-flash the device.

This time, the flashing process successfully passed 80%, and the system was successfully written and activated, indicating that the baseband recognition issue has been resolved and the device can enter the normal system boot process.

IV. Comprehensive Functional Testing

To ensure a thorough repair, all core functions of the device must be tested one by one:

· WiFi and Bluetooth: Can search and connect to the network normally, indicating that the baseband and wireless circuits are connected normally;

· Camera: The front and rear cameras can take photos and record videos normally;

· Audio: The earpiece, speaker, and microphone test normally, with no noise or no sound;

· Charging and Port Functions: The iPhone Charging Port is recognized normally, and charging and data transmission are normal;

· Call Functions: Can make and receive calls, and the signal is stable;

· Fingerprint or Face ID: If configured, recognition is normal;

· Sensor and Vibration Module: Auto-brightness, gravity sensor, and vibration feedback are all normal. 

After testing, the motherboard was reinstalled into the case, the screws were secured, and the screen was closed, completing the repair.

V. Summary and Recommendations

In this case, by disassembling the device, separating the parts, cleaning the solder joints, and reattaching the motherboard, we effectively resolved the issue of failed flashing due to poor soldering. This not only preserved the original motherboard but also saved repair costs and time. If you're looking for professional iPhone repair tools, visit the official China Phonefix website. We'll continue to provide you with updates on mobile phone repairs.