How canted coil springs work and how they are tested

A canted coil spring is a circular wire spring whose coils are elliptical and inclined. When the spring is compressed, each coil deforms independently, but the entire spring reacts as a single unit, so the load is consistent at every contact point. In connectors, the two ends of the spring wire are welded together to form a complete ring, and the ring is seated in recesses machined into the receptacle and plug.

How the ring holds in the groove

When the connector halves are joined, the ring is pushed into its groove and the coils deform under continuous spring force, building up resistance until each coil is fully seated. The load of the spring coils and the shape of the groove then maintain a steady spring force, so a corresponding extraction force is required to separate the two parts. The radial canted coil spring provides two key functions for miniature connections — latching and electrical contact — and helps reduce the number of components in the system.

Two functions in one ring

The canted coil spring serves a dual purpose: it can act as a mechanical joint, or it can maintain the electrical circuit between the male and female fittings. Its use reduces radio-frequency disturbance and simplifies the interconnection design of electronic equipment.

Meeting the demands of denser connectors

Connectors must process more signals in less space at higher speeds, and as the number of contacts rises the connector body grows smaller. The canted coil spring suits these requirements because of its unique force-deflection curve and wide operating range, with up to 35% compression. Its relatively stable spring force reduces wear caused by temperature differences, tolerances and other deviations, and each coil works independently.

How spring contacts are tested

Because of the special nature of the spring contact, the usual stiffness check is replaced by a test of the insertion and extraction force (or stress-strain behaviour) of the contact. The test is carried out in a simulated operating state: a force is applied to the spring finger and its deformation is measured to judge how soft or hard the spring is. This behaviour is directly related to whether a high-voltage switch opens and closes smoothly.