Xiaomi Mi 9 mainboard repair guide

1. Turn off your device by holding down the power button until the “Power off” option appears.
2. Use your finger to confirm that you want to shut down your device and wait until the screen goes blank.

1. The back cover’s heavily glued to the chassis. Heat the device evenly with hot air to soften the glue. A temperature of 60 - 80°C should be sufficient. As a rule of thumb, you should still be able to touch your device without it being uncomfortably hot.
2. The easiest way to loosen the back cover is to use a flat and flexible tool such as the iPlastix or iFlex. You will also need several picks to unstick the back cover all around.
3. Heat the spot where you start and place a flat tool between the back cover and the frame.
4. Use a suction cup to lift the glass if you can't find a place to insert your tool.
5. With the iSclack, you can easily lift the back cover and then use a flat tool to loosen the glue. Put both suction cups on the display and the backcover and press the lever of the tool together like a pair of pliers.

The iPlastix is made of plastic, so it won't scratch the device. On the other hand, it's very soft and tricky to insert. The iFlex makes it easier to get into the gap between the glass and the frame because it's made of very thin, stable metal. But it also makes it easier to scratch the frame of your device.

Be extra careful, the back cover can break very easily. If necessary, apply the heat several times and try again. Removing the back cover might take half an hour. Take a little more time and work carefully to make sure you don't break anything.

1. Once the tool is inserted, stick a pick into the gap to keep it open. Then run the tool around the entire edge to gradually loosen the glue.
2. Then heat the next part and insert the picks one by one.
3. Once the rear glass is unglued, you can lift it off.

The covers of the cameras remain in the device and are not permanently attached to the back cover. Loosen the adhesive there as well and take care not to damage the flex cable of the covers.

• 10 × 3,1 mm Phillips

1. Loosen the Phillips screws that secure the cover. The wireless charging coil and NFC antenna are attached to the plastic cover.

One or more screws may be covered with a sticker. Remove the stickers or pierce them with a screwdriver.

1. The cover is hooked into the housing. Lever with a tool under the plastic frame and lift the frame upwards.
2. Now you can remove the plastic cover together with the coil.

• Battery connector

1. Using the spudger, carefully disconnect the battery contact from the motherboard.

Always lever from a side where there are no small components on the motherboard. This avoids unintentional damage to capacitors or ICs.

• Antenna connector
• USB connector
• 1 × 2,6 mm Phillips
• Display connector

1. Using the spudger, carefully disconnect the marked contacts from the motherboard.

The safest way to release the antenna connectors is to grip the cable with a pair of tweezers and release the contact with a twisting motion. This way you don't risk damaging the circuit board by levering too much.

1. Remove the Phillips screw.
2. Take the SIM card holder out.
3. Now you can carefully lever the mainboard with a spudger and then remove the mainboard. Make sure it doesn’t get caught on the connectors you already disconnected.
4. Then set the board aside in a safe place.

• Antenna connector
• Display connector
• USB connector
• 1 × 2,6 mm Phillips

1. Then you can put the mainboard back into the case. Take care not to pinch any cables or connectors under the board.
2. Insert the SIM card holder. If it gets stuck, don't push it in with force. Then check whether the main board is correctly seated.
3. Fasten the board with the marked screw.
4. Now reconnect all marked connectors and antennas to the board.

Loosen the glued USB flex cable again if it is not yet exactly right and reposition it.

1. Use a pair of tweezers to connect the antennas.

• Battery Connector

Reconnect the battery.

1. Position the connector over its socket on the main board and press it down carefully.

• 10 × 3,1 mm Phillips

1. Put the cover with the antenna back in the enclosure after hooking it onto the top of the enclosure.
2. Then press the cover with your fingers until it clicks gently into place.
3. Fasten the phillips screws.

1. Turn on your device and test it before you finally close it.
2. Drag any app across the entire screen. Drag the app once around the entire border and then in a zigzag across the screen. The app should always follow your finger.
3. Then test the display brightness by dragging the brightness slider to minimum and maximum.

Test especially all functions of the part you replaced.

1. Check the adhesive on the edges of the back cover. If it's mostly intact, you can use it again and don't need any new glue.
2. Make sure that the adhesive lies flat and does not wrinkle. If this is the case, warm it up a little and correct it with tweezers.

Also check the adhesive around the camera cover and correct it if necessary.

1. If the adhesive frame is too loose or does not stick properly, use new adhesive.
2. To do this, first remove all old adhesive residues from the back cover. Use hot air again to loosen the glue more easily.
3. Then apply the new adhesive frame or thin double-sided tape to reglue the backcover.
4. Position the back cover over the device and press it down when it is exactly in the center.
5. Heat the glue one last time and press the backcover on. You can weigh the device down with books or use clamps to compress the glue as long as it cools down (about 10-20min).