Application of Ag-Pd-Mg new contact material to micro relays

The contact resistance characteristic is very important for twin contacts in down sized relays since the contact force is very small, only 0.01 N and the sticking behavior is another key parameter since break force is also reduced. Since the increase of contact resistance can be easily caused by contaminant films such as oxides film, thin Au or Au-Ag alloy has been overlaid to prevent this resistance degradation happening. However, sticking occurs for the overlaid contacts due to the super cleanliness. Therefore, the resistance and sticking are two sides of opposite problem. In order to solve this problem, the authors developed Ag-Pd-Mg alloy. In previous studies, low contact resistance has been obtained under both static and dynamic conditions with this alloy contacts covered with contaminant films. Furthermore, an excellent sticking resistance property has also been achieved. In this paper, the characteristics of Ag-Pd-Mg contacts installed into down sized relays are discussed. Sticking property, initial contact resistance, and static & dynamic contact resistance are also examined. The later part of this paper presents surface contamination behaviors for organic gases and related arc behaviors. The results are compared with Ag-Pd and Ag-Pd with Au alloy overlay and they show that Ag-Pd-Mg not only has low contact resistance under both static and dynamic operation conditions but also strong sticking resistance property. Moreover, non activation was found for Ag-Pd-Mg alloy and, therefore, arc duration was the shortest in all tested materials.