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Xiaomi Mi 11 CPU (Snapdragon 888) Repair – Solution to Common Problems

Snapdragon 888 is one of the most popular processers in recent years. However, from phones under the rule of Snapdragon 888, there has been so much criticism on the overheating problem. The Xiaomi Mi 11 is one of the first devices powered by a Snapdragon 888 processor. Today we will share how to fix common problems of Snapdragon 888 with a Mi 11 repair case.

Press the power button and the phone won’t turn on. Plug in the power cable and the phone is still dead.

The next step is to take out the motherboard for further testing. Place the phone back down on the heating pad at 90 °C for 2 minutes. Insert a plastic card and slide it through. Apply some alcohol to facilitate separation.

As the back cover is separated, remove the camera and motherboard shielding covers.

Disconnect the flex cables and then remove the motherboard. Detach the back camera module.

Hook the motherboard to a direct current supply and prompt a boot-up with tweezers. The boot current jumps between around 100 mA and 200 mA.

According to the current jump and our experience, devices powered by Snapdragon 888 tend to have problems like no power, no wifi, no sound, etc. due to the pseudo soldering of the CPU. The general repair solution is to reball the CPU.

In order to remove the CPU, we need to cut a gap first. Remove adhesive with a hot air gun at 300 °C and airflow 80.

Then heat the RAM with a hot air gun at 380 °C and airflow at 120. While heating, try to pry up the RAM with a pry blade. You can remove the RAM once it becomes loose.

Keep heating to remove the CPU. Then we apply some middle-temperature solder paste to the bonding pads. Neutralize the temperature of the bonding pads with soldering iron at 380 °C.

Clean tin on the bonding pads with solder wick. Remove underfill adhesive with a hot air gun at 300 °C. Clean the bonding pads with PCB cleaner.

Use the same method to clean tin and adhesive on the CPU. During cleaning, some capacitors will be erased. Please note that these are filter capacitors and do not influence the use of the phone.

Clean tin and adhesive on the RAM with desoldering braid. Remove residual adhesive with a hot air gun at 300 °C.

Reball the CPU. Apply some middle-temperature solder paste. Heat with a hot air gun to form the solder balls. Then recall the RAM.

The next step is to solder the CPU. Apply some paste flux. Align the CPU. Solder the CPU with a hot air gun at 350 °C and airflow at 100. Touch the CPU gently with tweezers. If the CPU returns to position, the CPU is soldered well.

Then we solder the RAM. Clean with PCB cleaner. After the motherboard cools, connect the motherboard with the direct current supply and trigger the boot-up with tweezers. The current jump becomes normal.

Then we put back the camera module to the motherboard.  Apply thermal paste to the CPU. Install the motherboard. The phone turns on and other functions work well.

How to Open a Phone Safely and Efficiently - REFOX Mobile Phone Opening Solution

In daily repair work, whether it's a simple screen & battery replacement or high-temperature soldering, we all need to open the phone. How to open the phone safely and efficiently has always been a hot topic.

The traditional way of opening a phone is to use a hot air gun for pre-heating, which is time-consuming and hard to achieve even heating.  After heating, the strength of lifting the screen by the suction cup is tough to control. If you are not skilled enough, you can easily break the flex cables.

Apple has recently launched its self-service opening tools, including a heated display removal fixture. The tool is not only big and hefty but also expensive. 

Today we will introduce the latest REFOX phone opening solution.

In the first place, we use the heat mat to heat the phone. Set the temperature to 80 °C. We measure that it only takes about five minutes to heat up to 80 °C.

The temperature variation between the front and back of the heating area is about 20 °C, so there is no need to worry about burning to the working table. Compared with the hot air gun, the heat mat heats up fast with even heating to soften the adhesive quickly.

Next, we place the phone back down on the heating mat for 5 minutes. After heating, we use the opening tool to open the phone. For starters, we turn the dial on the right to the top.

Then lift the upper body of the opener and place the phone on the suction cup. The suction is strong and the phone is firmly attached.

We can see that the opening area is covered with protective foam padding and there is even a camera groove. It can keep your phone safe and scratch-free during operation.

The next step is to place the back down on the opening area. For different sizes of phones, we can adjust the left dial to attach the phone.

As the phone is attached, lower the upper body and suction cup on the phone.

Then we fasten the suction up and rotate the right dial to lift the display.

To prevent breaking the flex cable. Please stop rotating when the angle between the screen and back housing is 15 degrees. 

Compared to the suction cup, the strength of the opening tool is easier to control for lifting the display, thus lowering the risk of breaking the display or flex cable. Other than the opening area, the tool features a pressing area. After the repair is complete, turn the dial to keep the screen or back cover firmly in place with the adhesive.  

To sum up, the latest REFOX phone opening solution boasts high efficiency and safety. It is suitable for opening both android phones and Apple’s iPhone, keeping your daily repairs safe and efficient.  Currently, there is free shipping for the opening tool kit on REWA Shop. Please feel free to leave a comment or contact our account managers if you are interested.