What is SIM (Subscriber Identification Module) card?

What is SIM card (Subscriber Identification Module)?

SIM card: A subscriber identity module is a removable smart card for mobile phones. SIM cards store the required information to identify the mobile device. It identifies not only the users’ identification, but also the service provider’s network.

SIM cards also serve as storage for SMS messages and the user's contacts. Current SIM cards can store up to 250 name / number pairs and up to 50 SMS text messages. The capacity of SIM card has 8K, 16K, 32K, 64K, the card above 512K is collectively called STK card.

Standard sizes of SIM card

Currently, the SIM cards come in four standard sizes: full-size SIM card, Mini SIM card, Micro SIM card, Nano SIM card, and eSIM card.

Full-size SIM card: (or 1FF, 1st form factor) was the first form factor to appear. It is the most common standard SIM card, is also called big card. Size: 85.6 x 54 x 0.8mm.

Mini SIM (2FF) card: As the phone develops smaller and smaller, the original full-size SIM card can no longer demand the needs of development, so the Mini SIM card appears. Size:25 x 15 x 0.8mm.

Micro SIM (3FF) card: It is commonly known as small card, or USIM card. The iPhone 4 was the first smartphone to use a Micro SIM card in June 2010, followed by many others. Size: 12 x 15 x 0.8mm.

Nano SIM (4FF) card: It was first introduced by Apple corporation in October 2012. The Nano SIM measures 12.3 x 8.8 x 0.7 mm and reduces the previous format to the contact area while maintaining the existing contact arrangements.

eSIM ( Embedded-SIM) card: The concept of the eSIM card is to directly embed the traditional SIM card on the device chip instead of adding it as a separate removable component of the device. The user does not need to insert a physical SIM card. This approach will allow users more flexibility in selecting carrier packages or changing carriers at any time without having to unlock equipment or purchase new equipment.

Mini SIM card  VS  Micro SIM card

Mini SIM card and Micro SIM card have no essential difference from the aspect of technology. The only difference is just their surface area, a kind of meaningless plastic surface area. So Micro SIM card is not what so-called technical innovation. In fact, the metal contact area of the Micro SIM card is a bit smaller than that of Mini SIM card, which has no any influence on its function.