Pogo pin

Exploded diagram showing components of a standard pogo pin

A basic spring-loaded pin consists of 3 main parts: a plunger, barrel, and spring.[2] When force is applied to the pin, the spring is compressed and the plunger moves inside the barrel. The shape of the barrel retains the plunger, stopping the spring from pushing it out when the pin is not locked in place.

In the design of electrical contacts, a certain amount of friction is required to hold a connector in place and retain the contact finish. However, high friction is undesirable because it increases stress and wear on the contact springs and housings. Thus, a precise normal force, typically around 1 newton, is required to generate this friction.[3] Since a spring-loaded pin needs to have a slight gap between the plunger and barrel so that it can slide easily, momentary disconnections can happen when there is vibration or movement. In order to counter this, the plunger usually has a small tilt to ensure a continuous connection.

Many manufacturers have created their own proprietary variations on this design, most commonly by varying the interface between the plunger and spring. For example, a ball may be added between the two components, or the plunger may have an angled or countersunk tip.[4][5]

Various pogo pin designs

The plunger and barrel of pogo pins usually use brass or copper as a base material on which a thin layer of nickel is applied. [6]

As common in electrical connectors, manufacturers often apply a gold plating that improves the durability and contact resistance.[7]

The springs are usually made of copper alloys or spring steel.[8][4]

Spring-loaded connectors are used for a wide variety of applications, in both industrial and consumer electronics:

• Board-to-board connectors (usually permanent)
• Ingress-protected connectors in consumer devices, e.g. smart watches, rugged computers
• Battery terminals on laptops
• Magnetic charging or signal connectors, e.g. laptop docks and chargers (see § Combination with magnets)
• High-frequency connectors, e.g. antennas, monitor connectors
• Printed circuit board testing
• Integrated circuit testing[9]
• In-circuit testing[10]
• Battery testing
• Other electronics testing

Connector arrangement

See also: Electrical connector

When pogo pins are used in a connector, they are usually arranged in a dense array, connecting many individual nodes of two electrical circuits. They are commonly found in automatic test equipment in the form of a bed of nails, where they facilitate the rapid, reliable connection of the devices under test (DUTs).[10] In one extremely high-density configuration, the array takes the form of a ring containing hundreds or thousands of individual pogo pins; this device is sometimes referred to as a pogo tower.

They can also be used for more permanent connections, for example, in the Cray-2 supercomputer.[11]

When used in the highest-performance applications, pogo pins must be very carefully designed to allow not only high reliability across many mating/unmating cycles but also high-fidelity transmission of the electrical signals. The pins themselves must be hard, yet plated with a substance (such as gold) that provides for reliable contact. Within the body of the pin, the plunger must make good electrical contact with the body lest the higher-resistance spring carry the signal (along with the undesirable inductance that the spring represents). The design of pogo pins to be used in matched-impedance circuits is especially challenging; to maintain the correct characteristic impedance, the pins are sometimes arranged with one signal-carrying pin surrounded by four, five, or six grounded pins.

Pogo pins connecting logic modules of the Cray-2 supercomputer

• Electrical connector, in which pogo pins are sometimes used
• Jumper (computing), performs a similar function but bridges a circuit between two pins
• In-circuit test, a common application of pogo pins
• Fuzz Button, a high performance electrical connection