Connector designers understand that many variables impact contact area and how adequately the contacts do their job. This next article in the “Connector Basics” series explains why even minor increases in contact resistance matter.

grid-300x300When a contact is mated, only a relatively small area is actually touching. All of the current must flow through this small area – the actual contact interface. Because the current is constricted to flow through this zone of contact, the resistance associated with this current constriction is called “constriction resistance.” Connector designers understand that many variables impact contact area (normal force, materials, surface finish, environment, etc.) and affect how adequately the contacts do their job.

The overall resistance of a contact system includes elements of bulk resistance and the separable contact interface. This discussion will be targeted toward the separable interface – that portion which is subject to degradation. Bulk resistance will remain unchanged, while the resistance associated with the separable interface (constriction resistance) is subject to change – and increases with degradation.

Connector verification programs are designed to access the reliability of the contact interface – quality of the interconnection is generally based upon overall resistance measurements. The difference between the initial and final resistance measurements – the change in resistance – is generally specified