Silver-coated copper particles as a new raw material for manufacturing electrical contacts

Electrical contacts were prepared from copper, silver, and silver-coated copper (Cu@Ag) powders by cold-press and sintering. Then, they were used in an electrical circuit and evaluated their performance under AC (7 A, 6000 switchings) and DC (10 A, 20 A, 200 switchings) currents. The microstructure, phase structure, thermal stability, and electrical resistance of the contacts were studied using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), and two-point electrical resistance measurement techniques. Results showed that the electrical resistance of copper contacts after 6000 switchings under AC current reaches from the initial value of 0.1 to 0.7 Omega. However, the electrical resistance of the silver and Cu@Ag contacts remained unchanged close to 0.1 Omega under the same conditions. The electrical resistance of copper contacts under 10 A-DC current increased from 0.11 Omega to 18 k Omega after 200 switchings, while the electrical resistance of the air and argon-sintered Cu@Ag contactsafter 200 switchings in the same conditions increased from 0.11 to 0.14 and 0.18 Omega, respectively. Increasing the DC current from 10 to 20 A increased the final electrical resistance of the copper contact from 18 k Omega to 35 k Omega and increased the electrical resistance of the Cu@Ag contact (sintered in air) from 0.18 Omega to 0.93 Omega after 200 switchings. Increasing the DC current from 10 A to 20 A did not affect the electrical resistance of the Cu@Ag contact sintered in argon. The study of microstructure of the contacts showed that surface of the copper contact oxidizes and cavities and micro-cracks appear on it during switchings. The Cu@Ag contacts sintered in argon were more resistant against oxidation than other contacts under switching.