Xiaomi Mi 9 - Replacing the fingerprint sensor

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.

• 1 × 2,6 mm Phillips
• 4 × 3,1 mm Phillips
• 2 × 3,8 mm Phillips
• Antenna connector

1. Loosen the Phillips screws that secure the speaker.
2. One of the screws is covered with a sticker. Remove the sticker first or pierce it with your screwdriver.

The screws have different lengths. Be careful not to mix them up. The easiest way to do this is with an iDoc magnet mat. You can place the screws on it the way they are in the device and due to the magnetic adhesion the screws will not get lost.

1. Then lever one side of the speaker with a spudger until it comes out of the device.
2. There is one antenna connected on the back of the speaker.
3. Loosen the antenna with a pair of tweezers by inserting them under the cable and then carefully lever it.

In the following steps, the motherboard and battery are removed. However, this is not necessary for this repair.

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

The USB-C socket and a microphone are attached to the smaller circuit board at the bottom of the device. There are also antennas and the fingerprint sensor connected.

1. First disconnect all connectors and the white antenna. Loosen the antenna by twisting the tweezers and then remove the antenna from its guide.
2. Remove the single black screw that fixes the board.
3. The board is glued into the device. Heat it evenly to loosen the adhesive more easily.
4. Then you can lever it up a little on the upper side until you can remove it.

The fingerprint sensor in the Xiaomi Mi 9 consists of a very small camera that is mounted directly under the screen.

Be especially careful not to damage the sensitive flex cable when loosening the fingerprint sensor.

1. Heat the flex cable evenly with hot air to make it easier to loosen.
2. Then use a thin tool such as a steel spatula to carefully slide it under the cable and loosen it by levering it slightly.
3. Also lever the camera module until it comes loose.
4. When everything is loose, you can remove the fingerprint sensor from the device.

1. Reinsert the fingerprint sensor module into the device.
2. Remove all adhesive around the camera opening if your replacement display has a new adhesive surface for the module.

Make sure that there is no dust or dirt on the camera lens and inside the unit. This may cause the unlocking via fingerprint to not work correctly.

1. Also position the flex cable underneath the camera correctly. A small nose in the device helps to position it there.

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

1. Insert the board with the USB socket back into the device.

Make sure that you do not pinch any cables under the board.

1. Slide it down so that the jack and microphone are properly seated in the lower edge of the housing.
2. Reconnect the two connectors and the white antenna cable.
3. The easiest way to connect the antenna is to position it over its contact with a pair of tweezers and then press it down with a spudger. Also push the antenna into its guide on the board.
4. Screw the USB board in place with the single Phillips screw.

• Antenna connector
• 1 × 2,6 mm Phillips
• 4 × 3,1 mm Phillips
• 2 × 3,8 mm Phillips

At the back of the loudspeaker an antenna has to be connected first.

1. Put the speaker in position and connect the black antenna cable with a pair of tweezers and a spudger.
2. Then reinsert the speaker over the USB port, press it tight and screw it into place.

Make sure it sits flush at the bottom of the device.

• 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).