Embedded SIM cards (MFF2) in IoT Projects

Embedded SIM cards are common on larger IoT projects where you want to save space or want to ensure that a SIM card does not get removed from the device. A lot of industry players use the eSIM and the Embedded SIM card synonymously, but we disagree with that terminology. Our terminology of eSIM refers to the “Remote SIM Provisioning” technologies and is not related to the Form Factor of the SIM card.

Please note that having eSIM capabilities does not correlate to the Form Factor of the SIM card. An eSIM enabled SIM card can be a plugin SIM card (2FF,3FF,4FF) or Embedded (MFF2, DFN, BGA, WLSCP).

In this article we’ll focus on things to take into consideration when working on a project with Embedded SIM cards.

Why utilize an Embedded SIM card vs plugin SIM

When a SIM card is embedded or soldered into the circuit board it brings complications to the project, but it also brings some benefits as well

• Environmental resistances. When a SIM card is soldered in the PBC it is less prone to failures due to environmental factors such as tremors or temperature changes. Soldering points are together and stay together keeping the contact points solid.
• Tamper resistant. When a SIM card is soldered in it is more difficult to remove and put into another device. It is not impossible to move embedded SIM cards around but it is significantly more difficult.
• Size considerations. An embedded SIM card is much smaller than even the smallest plugin SIM card and additionally not having to put the card reader on the device saves a lot of space on the device that can be used for other components such as enhanced GPU or more memory.

Form Factors

In general, an embedded SIM card is something that gets soldered into the PCB. The only standardized Form Factor is the MFF2 (Miniaturized Form Factor 2) packaging which is 5mm x 6mm x 1mm. In some cases, even that is too big and there are proprietary Form Factors released by the EUMs (SIM card manufacturers). As an example Thales provides MFFxs which are smaller size of the SIM card than MFF2s and Giesecke+Devrient has smaller Form Factors such as DFN (Dual Flat No-lead), BGA (Ball Grid Array) and WLCSP (Wafer Level Chip Scale Packaging).

If you do not have a pressing need you will have the easiest time utilizing the MFF2 SIM card as it will be best supported across the industry.

Installation and Testing

The installation of the MFF2 SIM card requires more advanced techniques than just a soldering iron and solder. Lucky the OEMs are well equipped for installing the SIM cards into the boards at their manufacturing site. It is common practice for the MFF2 SIM cards to be shipped to the OEMs so they can embed the SIM cards prior to shipping them out.

One consideration point that you need to take into account is that the SIM card will need to have service at the manufacturing site for testing purposes. For example, if your OEM is in Shenzhen, China and your device is a CAT-M type device ensure that the SIM card you are embedding into the device has this support. Simplex Wireless SIM card supports CAT-M Networks in China for this purpose.

eSIM support

One of the main reasons eSIM was brough to the marketing in 2011 was the need to be able to change the Service Provider (Mobile Operator) remotely Over-The-Air. Changing a SIM card in a device can cost more than $500 and is very cost prohibitive since having eSIM support is a no brainer.

If you plan to change Mobile Service Providers for any reason during the lifetime of your device having eSIM service such as the Simplex xoSIM.  

MoQ and Cost considerations

Embedded SIM cards add complexity to the project and are often delivered in reels vs individually packaged. Commonly a Minimum Order Quantity (MoQ) for an embedded project is 3,000 SIM cards, however it varies by Service Provider.

From cost size an embedded SIM card is typically 2-3x the price of a Plugin SIM card.

Conclusion

In conclusion, embedded SIM cards (MFF2) offer substantial benefits for IoT projects, particularly where durability, security, and space-saving are paramount. Their integration directly into the PCB creates a more resilient device structure, offering resistance to environmental factors and increased tamper resistance—key for IoT devices that may operate in remote or challenging conditions. Though smaller and streamlined, embedded SIM cards demand precise installation techniques and often require higher initial costs and larger minimum order quantities.

Furthermore, understanding the distinction between embedded SIM cards and eSIM technology is crucial. While embedded SIM cards primarily refer to form factors like MFF2 that are physically soldered to the device, eSIM capability allows for remote provisioning and is compatible across various form factors, including plug-in options. This capability can be particularly advantageous for long-term device management, where remote updates or provider changes are necessary, minimizing physical maintenance and downtime.

For projects requiring both embedded security and flexible connectivity, considering eSIM-enabled embedded SIM cards, like Simplex Wireless’ options that support global networks, can offer a balanced solution. By integrating these technologies thoughtfully, companies can deploy IoT devices with enhanced reliability, adaptability, and efficiency, setting the foundation for scalable IoT applications in diverse sectors.

This article was written by Jan Lattunen, CCO Simplex Wireless

About the Author: Jan Lattunen manages Sales and Marketing for Simplex Wireless. Jan has 20 years’ experience in working with SIM card technology and was involved in launching the eSIM in North America with major carriers and OEMs. His expertise in telecommunications is around SIM cards. On a personal note, Jan is a family man and avid cyclist with advocacy for safety in the roads. You can connect with Jan on https://linkedin.com/in/JanLattunen