Composition characteristics of bronze coating systems and their influence on contact properties in electrical applications

Noble metal coating systems are typically used in electrical contacts to provide a reliable and robust functional capability. Due to high and volatile costs of noble metals, it is an ongoing demand to reduce noble metal consumption in contact applications by utilizing a resource-conserving process. The present study addresses the development of alternative bronze coating systems with contact characteristics similar to silver. The new bronze coating systems do not only excel by their contact characteristics, but also emerge due to their improved wear and corrosion resistance. Standard pin and socket contacts were used to determine the tribological and electrical properties of different bronze coating systems. A systematic variation of the electroplating conditions and the electrolyte composition was used to determine the influences on the layer composition as well as the mechanical and electrical properties. Contact resistance measurements, mating cycles and storage under different climatic conditions were carried out to ascertain the main coating characteristics for separable connector applications. Finally, SEM and EDX measurements were used to characterize the wear tracks as well as the corrosion performance in more detail. During all tests stable and low contact resistances are measured. Therefore bronze coating systems can enable the reduction or replacement of standard noble metal coating systems in certain applications.