In computing, an expansion card is a printed circuit board that can be inserted into an electrical connector, or expansion slot on a computer's motherboard to add functionality to a computer system. Sometimes the design of the computer's case and motherboard involves placing most of these slots onto a separate, removable card. Typically such cards are referred to as a riser card in part because they project upward from the board and allow expansion cards to be placed above and parallel to the motherboard.
Example of a PCI digital I/O expansion card using a large square chip from PLX Technology to handle the PCI bus interface
Altair 8800b from March 1976 with an 18-slot S-100 backplane which housed both the Intel 8080 mainboard and many expansion boards
Rack of IBM Standard Modular System expansion cards in an IBM 1401 computer using a 16-pin gold plated edge connector first introduced in 1959
Configuration DIP switches in a 16-pin through-hole package as often found in ISA expansion cards from the 1980s
A printed circuit board (PCB), also called printed wiring board (PWB), is a medium used to connect or "wire" components to one another in a circuit. It takes the form of a laminated sandwich structure of conductive and insulating layers: each of the conductive layers is designed with a pattern of traces, planes and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Electrical components may be fixed to conductive pads on the outer layers in the shape designed to accept the component's terminals, generally by means of soldering, to both electrically connect and mechanically fasten them to it. Another manufacturing process adds vias, plated-through holes that allow interconnections between layers.
Printed circuit board of a DVD player
Part of a 1984 Sinclair ZX Spectrum computer board, a printed circuit board, showing the conductive traces, the through-hole paths to the other surface, and some electronic components mounted using through-hole mounting
Proximity fuze Mark 53 production line 1944
Through-hole (leaded) resistors