TeardownVivo Phone Repair

Vivo X21 Teardown

As we all know, the vivo X21 with the under-display fingerprint scanner will start the pre-orders on March 28. Except for under-display fingerprint technology, the X21 also adopts Face Wake. Today, we will start the teardown of this phone to explore its internal structure and the secret of the under-display fingerprint reader.

First of all, remove the SIM card tray.
remove SIM card tray
The top part of the SIM card tray uses rubber ring to prevent vapor and dust from entering inside of the phone body, and that’s the design that most water-resistant phones have adopted. It is not much surprising for me to see the X21 adopts such design since we have found that vivo attaches much importance to phone’s sealing effect.
SIM card tray
Take out two screws at the bottom.
Take out two screws
The back cover uses lots of graphite sticker and its surface is covered with foam framework.
internal structure
After removing the key cap from the phone body, we find that this part hasn’t adopted rubber ring like iPhone does. Its edge parts become thickened via injection process which can to some extent cushion clash the phone receives.
removing keycap
The vivo X21’s internal design is quietly different from that its predecessors adopt. The motherboard occupies less area and modules at the bottom increase area they occupy, which results from the SIM card tray’s removing from top to the bottom. Remaining the 3.5mm earphone jack, the phone inherited powerful HiFi capability from vivo family.
internal design
We find that all the connectors on the motherboard are fixed by the metal plate to avoid getting disconnected by fall down except coaxial line connection. Besides, basically, all the visible capacitors are processed with black glue to avoid short circuit caused by vapor. The earphone port is sealed by a black rubber ring, which shows the phone’s excellent sealing.
Next, we need to disconnect ribbon cable of the motherboard. Firstly, we need to uncover the graphite sticker on the shield cover. There is heat dissipation copper sheet under the graphite sticker. Such heat dissipation design is not common since most phones usually chose either graphite sticker or heat dissipation copper pipe or even don’t adopt any of them.
disconnect wire ribbon
There is a screw hidden under the graphite sticker. This screw and other two screws are used to fix connectors at the bottom to protect the cover plate. We remove these screws.
remove screw
After uncovering the cover plate, we find five connectors of ribbon cable at the bottom. So we need to use an insulating pry to disconnect battery connector on the right to power off the system in case of short circuit.
uncovering the cover plate
With all the screws and ribbon cable removed, we can easily take out the motherboard.
take out the motherboard
Both motherboard’s front and back parts have high space utilization, two shield covers are placed extremely close. If not taking the camera into consideration, the area that the phone’s motherboard occupies is basically the same as iPhone X’s dual-layer motherboard. But the motherboard of the iPhone X contains the single SIM card slot while the vivo X21 remains the 3.5mm earphone port.
The phone comes with a 12MP camera with F/1.8 aperture and secondary 5M camera with a F/2.4 aperture on the back. It also features a 12MP front camera which has F/2.0 aperture. The model focuses on AI function.
The orange part is octa-core Qualcomm Snapdragon 660AIE processor which has four cores up to 2.2GHz and four cores up to 1.8GHz. Memory and flash are placed in the green area. There is no information on them, but official party announces that the memory has a capacity of 6GB and flash has a capacity of 128GB. The blue area is skyworks77643-31. The red part is Qualcomm frequency transceiver SDR660.
Uncover the heat dissipation copper sheet on the shield cover of the front of the motherboard, and we find that shield cover is weld on the motherboard, which means that it can’t be removed. Considering that the device’s internal component can’t be destroyed, we stop removing the shield.
Uncover the heat dissipation copper pipe
The X21 sports a Li-Polymer battery. The battery’s normal voltage is 3.85V and its limited charge voltage is 4.4V. It has the capacity of 3200mAh, 11.85Wh.
Then, take out the loudspeaker module. From the front of the module, we know that the loudspeaker is from ACC which has been a supplier of Apple. The similar design like the white particle in the blue dot has appeared on loudspeaker module of many high-end models. We infer that is a new patent of technology ACC to make sound clearer.
Later, take out PCB. The front connector and visible circuit adopt rigid sealing design as the motherboard does. Besides, the charge port is protected by a black rubber ring. The back of the PCB is basically occupied by SIM card slot. It is not common to see that the phone features the PCB with its back part utilized.
take out PCB
Now, we will unveil secrete of the under-display fingerprint scanner. Heat screen edges, and then insert a pick along the slot into the screen plate to separate the screen from the roll cage.
remove the screen
The screen’s verge is less than 1mm away from the verge of the glass plate. And the little space needs to be covered with the double-sided adhesive which is used to fix the screen tightly with the phone body. Such a small space has been left for the super narrow bezel.
The under-display fingerprint reader is placed right under the middle of the screen. This fingerprint doesn’t look quietly different from other fingerprint readers, but it needs to identify fingerprint through screen and glass plate. That’s the difference between it and other fingerprint readers since common fingerprint reader can only identify fingerprint through thin glass.
under-display fingerprint reader
Besides, we find that the phone applies COG sealing technology to the bottom of the screen. This technology is to curl ribbon cable of the screen under the screen to make it much more convenient to make the screen chin occupy less space. From the picture, we can see that the chin is extremely narrow, but it still is thicker than the bezels on two sides since it needs to leave space for the ribbon cable.

The vivo X21
We have removed 17 screws from the phone body in total. The vivo X21 has left a deep impression on me with its rigid sealing design, compact internal structure, and high space utilization. Besides, the phone’s CFM process has improved a lot compared with its predecessor. We are looking forward to seeing its performance in the market.



I love all digital products, mobile phones, laptops, cameras, headsets, etc. Writing news about these products is also my specialty.

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