Complete guide for selecting board to board connectors

Multiple types of board to board connectors
Board to board connectors come in various shapes and sizes, providing a modular feel for multi board PCB systems. There are many common types of board connectors, and different suppliers have their own product lines, which are usually classified into the following categories:
Pin connectors: Most designers are familiar with the arrangement of 1-row or 2-row pin connectors, with a spacing of 1 millimeter. This style has variants, including stacked pin joints. Pin connectors can have a cover and keys (even multiple keys) to ensure correct pin correspondence when connecting the board.
1）Relay connector: This type of board to board connector connects two parallel printed circuit boards in a stacked configuration. There are many styles of relay connectors. Note that pin connectors can be used as relay connectors.
2）Edge card connectors: The most common use of this style of connector is in RAM bars and COMs/SoMs. In fact, it can be used for any board to board connection along the edge of the board, whether using custom or standardized pin arrangements.
3）Backboard connectors: This type of connector is worth classifying separately because it needs to adapt to high data rates and a very sturdy structure.
4）Standardized connectors: Some connectors may be developed to meet very specific industry standards, beyond the edge connector styles used for card insertion. The standard organizations that define specific connector styles include VITA (for backplanes), PCI-SIG (PCIe cards), IEEE (e.g. 1386 standard for relays), JTAG, PC/104 (square pin connectors), etc.