Surface Roughness Effects on Contact Resistance in High Frequency Test Sockets
Surface roughness forces high-frequency current through isolated micro-asperities, increasing contact resistance and insertion loss as skin depth shrinks.
Normal Force
Meaning
Perpendicular contact force exerted by a connector spring against a mating pin ensures a secure and low-resistance electrical connection. Adequate normal force is required to break through residual surface films and maintain mechanical stability under vibration. This physical parameter defines the operational limit of most board-to-board and wire-to-board connectors.
It dictates both the mechanical wear of the plating and the insertion force required to mate the housing.
Mechanical Limitation
Designing the spring contact involves balancing the insertion force with the required retention force of the system. Excessive normal force causes premature wear on the thin metal plating, exposing the base metal to oxidation. This trade-off requires engineers to model the spring rate and the pin deflection carefully.
Measurement Procedure
Testing requires specialized equipment to measure these forces at the contact point. A normal force profile is generated by recording resistance during pin insertion. This curve identifies deviation from the nominal design.
System Reliability
Long-term contact stability depends on the connector retaining its mechanical properties throughout the lifespan of the equipment. Over time, high temperatures and continuous stress can cause stress relaxation in the metal spring, which decreases the normal force and increases electrical resistance. This decrease can lead to signal loss or localized overheating in power pins, making the choice of spring alloy a major factor in hardware durability.