Contact resistance characteristics of Ag-SnO₂ contact materials with high SnO₂ content

The contact resistance and surface morphologies characteristics of Ag-SnO₂ contact materials with high SnO₂ content was investigated in make-and-break operations. The microstructure and arc eroded surface morphologies of Ag-SnO₂ samples were researched by Scanning Electron Microscopy (SEM). The surface profiles and average surface roughness S_a of arc eroded Ag-SnO₂ samples were also analyzed by Scanning Laser Microscope (SLM) 3D surface technique. With the SnO₂ content increase from 15 wt.% to 30 wt.%, it was found that contact resistance of Ag-SnO₂ materials increased by 33% and stabilize in 5 mΩ when contact force over than 70 N. The surface morphologies of arc eroded Ag-SnO₂ samples were stable and uniform compared with the original samples. The theoretical analysis and experimental results of contact resistance characteristic indicated that contact force is the predominant factor for the contact resistances of Ag-SnO₂ materials with high SnO₂ content and contact resistance of high SnO₂ content Ag-SnO₂ materials can be reduced significantly by increasing the contact force.