Possible reasons for sim card disconnection

                                                   Possible reasons for sim card disconnection

After a period of normal use, if the sim card is disconnected, the system will prompt that the card cannot be found or the card is damaged. 

It may not be a problem with the sim card connector.

1. Situation Description

The device is disconnected, and it is found through the system connection that the module is normal, but the SIM card cannot be found;

Restart the power of the device, but still cannot go online and cannot find the SIM card;

Plug and unplug the SIM card, re-power on, you can find the SIM card;

Continue to use for a period of time (for example, about 2 weeks), but the connection is dropped again, and the SIM card cannot be found;

The on-site inspection found that the sim card connector contacts are in good condition, and the shrapnel and plastic structural parts have no deformation;

Check the SIM card and find that the gold fingers on its surface are seriously oxidized, which affects the contact, as shown in the following figure:


After removing the oxide layer on the surface of the SIM gold finger, it is normal after being loaded into the device.

2. Summary

To sum up, it can be judged that the SIM card gold finger is oxidized and causes poor contact, so that the control card cannot go online normally. When encountering a similar situation, the temporary solution is to use an eraser or alcohol to clean the gold finger (if you use alcohol to wipe, please ensure that the alcohol The basic solution is to use an industrial-grade SIM card with better performance.

3. Recommendations for SIM card selection

Choose industrial-grade MP2 standard SIM card with better plating, with gold-plated thickness of 15u contacts, the contacts are not easy to be oxidized, and the reliability is higher.