Owners of smartphones Xiaomi, Redmi and Poco often face the need to replace or install a new smartphone. SIM-Despite the apparent simplicity of the procedure, improper installation of the chip can cause it to damage or the device to fail to read the network. The question of which side to insert the sim card in the shaomi remains one of the most frequent in technical support, as the location of contacts and trays varies from model to model.
Modern smartphones use trays of different formats, and trying to insert a card forcefully or without orientation can be fatal for contacts. In this article, we will discuss in detail the physics of trays, how to determine the right side without instructions and how to solve problems if the phone stopped seeing the operator. You do not need to be an engineer to understand this, you need to study the design of the slot carefully enough.
Before you start removing the tray, it’s important to understand that the orientation of the chip depends on the type of slot used. Xiaomi devices have both combined slots (SIM + microSD) and separate, as well as hybrid variants. A mistake in determining the side can cause the gold pins to not touch the pins inside the phone, and you will receive a message “No network” or “SIM not detected”.
Definition of tray type and design
The first step before installing a card is to visually view the end of your smartphone. Xiaomi devices of recent years are most often equipped with trays that are removed with a special clip (or needle). The design of the tray dictates how the map should lie. There are two main types of trays: one-way and two-way (sandwich type), although the latter are increasingly rare.
The one-way tray is a flat frame where the card is placed flat. In such models, the question of which side is solved simply: you look at the drawing squeezed on the tray itself or on the phone frame next to the slot. If the tray is bilateral, then one side is for the SIM, and the reverse side is for the memory card or the second SIM. In this case, it is important not to confuse the sides, since inserting two cards on one side will lead to a jam mechanism.
Notice the shape of the cutout in the tray. The cut corner of the card must always match the ledge in the tray recess. It's the main mechanical key that prevents you from mounting the card upside down unless you use force. However, even when the angle matches, the map can be flipped up or down by the contacts, which is the most common user error.
Visual hints on the body and tray
Xiaomi engineers have devised several ways to help users avoid confusing the installation side. Carefully examine the extracted tray. Many models, such as the Redmi Note or Poco X, have micro-schematic images on the metal frame, showing the map outline and the location of the gold contacts relative to the frame.
If there are no obvious markings on the tray, look at the hole in the end of the case. Often, there is a small stencil next to the slot that depicts the card in terms of contacts. If you see the image of the chip, you need to insert the card with contacts upwards (to the screen), if you have the back of the card, then with contacts downwards (to the back cover), which is a universal rule for most gadgets.
It is also worth considering that some flagship models use eSIM technology or trays without mechanical contacts (rare, but it happens in industrial versions), but for a mass market the rule is one: gold contacts should look in the direction indicated by the scheme. If there is no scheme, rely on the coincidence of the angle slice and the logic of the location of pins inside the slot.
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If there is no marking on the tray, put the card on the table with the contacts up. The tray is usually placed in the phone so that its “facing” side (where you look when you install) corresponds to the side of the smartphone screen.
Step-by-step: how to insert the SIM correctly
The installation process requires care and good lighting. Take your time to avoid damaging fragile contacts. First make sure the phone is turned off, although modern Xiaomi smartphones support hot replacement, but for initial network setup, it is better to restart the device after installation.
Use the original paper clip or a thin needle. Press the slot hole perpendicular to the body until the characteristic click and extract the tray. Place the tray on a flat surface. Now compare the shape of your tray. SIM-Nano-SIM with a cutout, the cut corner should match perfectly.
Now the most important thing is the orientation of contacts. 90% of the time in Xiaomi smartphones with combined slots. SIM-The card is placed upwards (gold to the phone screen), and the microSD card is placed downwards (to the back cover), or vice versa, but they always look in different directions in combined slots. In individual slots, the direction depends on the model, but most often the contacts are also pointed upwards.
☑️ Checklist of correct installation
Once you've laid the map, gently push the tray back into the case. It should go easy, without creaking or jamming. If you feel resistance, don't push! Take out the tray and check orientation again. The force here is the enemy, it can break the reader's inner pins.
Differences in Redmi, Poco and Mi models
Xiaomi’s smartphone lines have their own design features, for example, in the Redmi Note series (especially older models like the Note 8, 9, 10), there was often a combined slot where the two were used to play the game. SIM And the microSD was on either side of the tray, and it was confusing for many users who were trying to shove two of them together. SIM-cards in one compartment, breaking plastic.
In the Poco series (e.g. Poco) F3, X3 NFC) Manufacturers often use separate slots for two. SIM-cards located next to each other, or the classic combined. In the flagships of the Xiaomi Mi and Xiaomi series 11/12/13 It is common to support two Nano-SIMs without the possibility of expanding memory, where both slots are on the same tray plate on different sides or on the same side next to each other.
Below is a table to help you navigate the device series, but always check the model as revisions may differ.
| Device series | Slot type | SIM 1 orientation | SIM 2/microSD orientation |
|---|---|---|---|
| Redmi Note (8-12) | Combined | Contact up. | MicroSD contacts upwards (on the other hand) |
| Poco X3 / F3 | Combined | Contact up. | MicroSD contacts down |
| Xiaomi Mi 11 / 12 | Two SIMs (Nano) | Contact up. | Contacts up (nearby) |
| Redmi 9 / 10 / 11 | Triple slot | Contact up. | 2 SIM + microSD (all on one side) |
What if the tray doesn't fit?
Typical errors and problems with definition
One of the most common mistakes is trying to insert a Micro-SIM card into a Nano-SIM slot without using an adapter or using a homemade adapter that is thicker than normal.This leads to a tray getting stuck.Never use Scotch to glue the card to the adapter, if glue gets on the contacts or inside the slot, the phone may fail.
Another common problem is contact contamination. If you put the card in the right side but the phone can't see it, wipe the gold chip with a soft cloth or a pin, oxidation or fat from your fingers can prevent contact, and check if the card is upside down (contacts to the plastic tray), this happens in poor light.
⚠️ Note: If after installing the card correctly, the phone says "No" SIM» or "Infidel." SIM-Try to move the tray gently (without taking it out completely) sometimes the contacts inside the phone are a little bit overlaid and don't reach the chip. If that helps, maybe repair the connector needs to be done.
And you can't ignore software failures, sometimes after you've been replaced. SIM It doesn't just need to reboot, it needs to reset the network settings. → Connection and sharing → Resetting Wi-Fi, mobile networks and Bluetooth.This won't delete your personal data, but will update network configurations.
Diagnostics and Solving Reading Problems
If you're sure you know which side to put the Sim card in your shaomi, but the device is still silent, go to the diagnostics. SIM-If it doesn't work there, the operator has a problem, and you have to go to the communications room to replace the plastic.
If everything works on another phone, it means the problem is in the slot or settings of Xiaomi. SIM-Make sure the slot is activated. MIUI When the system is first installed, it may ask if the new card is SIM, If you accidentally select Data Only or cancel the setting, the slot may remain inactive.
Also worth checking for system updates. In older versions of MIUI, there were bugs with the communication module that were patched. Go to Settings → About the phone and click on the MIUI version to check for updates.
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90% of SIM card “non-vision” problems are solved by properly cleaning the contacts and restarting the device after installation.
Safety and care SIM-tray
Tray SIM-The regular removal and insertion of cards (for example, when transferring data between phones) shatters the spring mechanism. Try to minimize such actions. SIM, Consider using eSIM if your model and carrier support this technology.
Dust and moisture are the main enemies of contacts. Although many modern Xiaomi have spray protection, the open tray is a very powerful tool. SIM-Always make sure the tray is closed tightly and until you click before you go outside or in a wet room.
⚠️ Warning: Do not use metal paper clips of the stationery type if they are too thick. They can damage the latch mechanism inside the case. It is better to use the original paper clip from the box or buy a special tool to open the trays.
Compliance with these simple rules will prolong the life of your device and ensure a stable connection. SIM-Cards are a basic skill that will save you from unnecessary trips to the service center.