Investigation on friction coefficient evolution for thin-gold layer contacts

The long service duration functioning of semi permanent contacts throughout their lifetime relies on having a stable contact force. This stability leads to reliable mechanical and electrical performance of the connector. In a previous study, the contact force was evaluated using the insertion force and the friction coefficient. This usual friction coefficient of the contact material (gold coating for HE9 connectors) is first assumed constant. However, the thin gold layer deposit can be seriously impacted after several matings of the PCB (Printed Circuit Board) into the connector. Indeed, when the contact area is not sufficiently lubricated and is subjected to a tangential stress, this modifies the friction coefficient which can no longer be considered as a constant. In this article, a new method for the direct measurement of the contact force, applied to the semipermanent connector, is presented by using an ultra thin piezoresistive sensor. Associated with the insertion force measurements, the contact force measurements yield the friction coefficient which is then calculated in order to identify its evolution during long-time experiments. This new technique makes it possible to learn more about the kinetics of the connector aging and provide answers to identify a possible contact failure.