M.2 Module Interface Connector

M.2 Module Interface Connector

2022-02-05. Category & Tags: Edge-and-Hardware M.2, Key, NGFF, NVME, PCIe, Connector

Concepts #

def m.2 (now) #

M.2 (pronounced “M dot two”) is a compact card or module form factor supporting multiple protocols and applications. It was developed by PCI-SIG and SATA-IO. The M.2 comes in two main formats:

  • Connectorized, which includes a “card” (with pins) and a motherboard “socket (a.k.a. slot)” (with contacts)
  • Soldered down

m.2 vs. ngff (old) #

M.2 was originally called the Next Generation Form Factor (NGFF).
It was formally renamed to M.2 in 2013.
Most people refer to M.2-SATA as NGFF, however, some consider NGFF as the old name of M.2 (thus the same thing) which includes 3 common SSD protocols: NVMe vs. SATA vs. AHCI (by Intel).

m.2 module targeted applications #

M.2 is commonly used as solid state drives (SSDs) but can also be used for the following applications:

  • Wi-Fi
  • Bluetooth
  • Global Navigation Satellite Systems (GNSS)
  • Near Field Communication (NFC)
  • WiGig
  • WWAN (2G, 3G, and 4G)
  • Other and Future Solutions (e.g., Hybrid Digital Radio (HDR)
  • Hardware Accelerator

Most Common Usages #


【Example】 The WIFI card’s socket in a Lenovo desktop PC is E keyed only:

The socket on the left is M.2 E keyed WIFI socket.
The socket on the right is M.2 M keyed SSD socket (the SSD card is B+M keyed NVME).

[Example] Lenovo L490 laptop B keyed SSD socket (PCIe NVMe, PCIe 3.0 x2, seq. read 1489.1MB/s):

ssd etc. #

ref (bak)

Common Socket Keys:

Key supports
Key A PCIe (x2) and USB
Key E PCIe (x2) and USB
Key A+E PCIe (x2) and USB *
Key M PCIe ( x2 / x4 )
Key B+M SATA or PCIe *

* Depending each on the internal connection.


Note:[2021] Theoretically and / or in future, the Keys listed here are able to support also other kinds of signals. Furthermore, Keys that are not listed here are reserved for coming variants or interfaces. The table depicted above is valid for Delock products.

Sunny note:

  • M.2 SATA card may be B keyed or B+M keyed.
  • M.2 NVMe card may be M keyed or B+M keyed.
  • M.2 NVMe socket may be M keyed or B keyed.

Details #

【example】 b keyed socket (i.e. 2199230-3) #

photoPCB Footprints
ref TE Connectivity


Key ID Pin Location Interface
A 8-15 2x PCIe x1 / USB 2.0 / I2C / DP x4
B 12-19 PCIe x2 / SATA /USB 2.0 / USB 3.0 / HSIC / SSIC / Audio / UIM / I2C
C 16-23 Reserved for Future Use
D 20-27 Reserved for Future Use
E 24-31 2x PCIe x1 / USB 2.0 / I2C / SDIO / UART / PCM
F 28-35 Future Memory Interface (FMI)
G 39-46 Not Used for M.2; for Custom/Non-Standard Apps
H 43-50 Reserved for Future Use
J 47-54 Reserved for Future Use
K 51-58 Reserved for Future Use
L 55-62 Reserved for Future Use
M 59-66 PCIe x4 / SATA

M.2 Card Type Naming Convention (Module Nomenclature) #

ref: PCI Express M.2 Specification Revision 4.0 Version 1.0.

E.g.: 2242-D2-B-M



  1. Use ONLY when a double slot is being specified.
  2. Label included in height dimension.
  3. This dimension is 11.5 mm but is written as 11 in Type name (i.e., BGA Type 1113).
  4. For BGA SSD, maximum height is measured with the solder balls collapsed and is valid whether the BGA is located directly on a platform or mounted on a module board.
  5. Insulating label allowed on connector-based design.
  6. Key G is intended for customer use. Devices with this key will not be M.2-compliant. To be used at customer’s risk.
  7. Use only when specifying the top surface as planar.