ZIF

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ZIF is an acronym for zero insertion force, a concept used in the design of IC sockets, invented to avoid problems caused by applying force upon insertion and extraction.

A normal integrated circuit (IC) socket requires the IC to be pushed into sprung contacts which then grip by friction. For an IC with hundreds of pins, the total insertion force can be very large (tens of newtons), leading to a danger of damage to the device. Also even with relatively small pin counts each extraction was fairly awkward and carried a significant risk of bending pins (particularly if the person performing the extraction hadn't had much practice or the board was crowded). Low insertion force (LIF) sockets reduced the issues of insertion and extraction but the lower the insertion force of a conventional socket, the less reliable the connection is likely to be.

With a ZIF socket, before the IC is inserted, a lever or slider on the side of the socket is moved, pushing all the sprung contacts apart so that the IC can be inserted with very little force (generally the weight of the IC itself is sufficient with no external downward force required). The lever is then moved back, allowing the contacts to close and grip the pins of the IC. ZIF sockets are much more expensive than standard IC sockets and also tend to take up a larger board area. Therefore they are only used when there is a good reason to do so.

At least some force should remain so that the contacts are freed from dirt and an oxyde layer and polished to better fit to each other, while the lever allows a very high pressure and therefore a large contact area.

Large ZIF sockets are mainly used for PC processors (from about the mid 1990s forward) as these are likely to be upgraded or replaced several times during the lifetime of the socket, and are among the few chips expensive enough to make such elaborate package/socket systems worthwhile (most chips nowadays are simply soldered directly to the surface of the PCB). Smaller ZIF socket are often used in chip-testing and programming equipment, when the same socket will be used to test or program hundreds of chips.

[edit] Universal test sockets

Standard DIL packages come in two widths (measured between pin centers), 0.3 in (skinny dip) for smaller devices (8-28 pin) and 0.6 in for larger devices (24-40 pin). To allow design of programmers and similar devices that supported a range of devices some in skinny dip and some in full width dip universal test sockets are produced. These have wide slots into which the pins drop allowing both 0.3 in and 0.6 in devices to be inserted.

[edit] ZIF wire-to-board connectors

ZIF wire-to-board connectors are used for attaching wires to printed circuit boards inside electronic equipment. The wires, often formed into a ribbon cable, are pre-stripped and the bare ends placed inside the connector. The two sliding parts of the connector are then pushed together, causing it to grip the wires. The most important advantage of this system is that it does not require a mating half to be fitted to the wire ends, therefore saving space and cost inside miniaturised equipment.