Edge connector

44 pin edge connector sockets (blue objects) and matching circuit board. Edge connector is 3.5" (9 cm) with 22 contacts on each side

An edge connector is the portion of a printed circuit board (PCB) consisting of traces leading to the edge of the board that are intended to plug into a matching socket. The edge connector is a money-saving device because it only requires a single discrete female connector (the male connector is formed out of the edge of the PCB), and they also tend to be fairly robust and durable. They are commonly used in computers for expansion slots for peripheral cards, such as PCI, PCI Express, and AGP cards.

Socket design

Edge connector sockets consist of a plastic "box" open on one side, with pins on one or both side(s) of the longer edges, sprung to push into the middle of the open center. Connectors are often keyed to ensure the correct polarity, and may contain bumps or notches both for polarity and to ensure that the wrong type of device is not inserted. Recommended PCB thickness found in datasheets of the manufacturers is to be considered for new designs. The edge connector socket needs fit to the thickness of the edge-connector-carrying PCB.

The opposite side of the socket is often an insulation-piercing connector which is clamped onto a ribbon cable. This can be seen inside a personal computer as the connection to a floppy drive. (5.25" floppy drives actually used an edge connector, while 3.5" drives use a pin connector instead, but both typically use the same insulation-piercing connector to the ribbon cable on the back of the connector.) The other side may also be soldered to a motherboard or daughtercard. This is seen inside every PC for connecting expansion cards and computer memory to the system bus. Slot 1 and Slot A were also commonly-used at one point, the processor being mounted on a card with an edge connector, instead of directly to the motherboard as before and since.