Wire-wrap

Wire-wrap was once a popular technology for production of electronics, especially computers. The basic concept is that a series of 'pins' (generally about 2 cm tall, and usually plated in either tin or gold) are connected by wires (usually insulated with Teflon, and stripped about 1 inch at each end) which are wound around the pin, usually by a powered 'gun' (although manual wire-wrap tools do exist). A single pin can usually hold several wires; the exact number depends on the height of the pin, the gauge of the wire, etc.

It was widely used for production, primarily of backplanes, during the late 1950's to early 1980's, with much of the wrapping being done by automated machines driven by a pre-recorded program (although in the early machines this would have been from a tape, not an computer). Wire-wrap finally fell out of use for production when multi-layer PCB technology allowed use of PCB's in backplanes.

One advantage of wire-wrap in this application is that it is easy to make repairs and changes, even in the field; the old wire(s) are removed, and replacements added. This ability to produce assemblies by automated machinery, but also easily make repairs and changes, is still fairly unique.

It was also popular in prototyping applications, since it made it easy to wire a custom board. (In fact, boards filled with chip sockets with wire-wrap pins were available for major busses, such as UNIBUS and QBUS, precisely for prototyping and very-low-volume production.)

In this application, it has been superceded by the close integration between new, advanced CAD tools (which can do PCB layout) and PCB fabrication houses, which makes fast bespoke production of PCB's in low volume cost-effective.