Abstract
Abstract
The studied Electrical contacts of switches are actuated with metallic domes or with elastomers membranes. The two contacts are plated one against the other with a recall force established by a mechanism with abrupt or continuous rupture. This force generates the mechanical contact between the mobile contact fixed on dome or the piston and the fixed contact printed tracks of PCB. This mechanical contact causes the closing of the electric circuit via an electric resistance of contact whose initial value and stability are essential for the reliability of the electric system. In this study, we investigate the law governing the initial resistance versus contact force Rc = Kc Fc -n in the range of 1mN-10N and for coating usual coating Au, Sn or novel coating , AgC, C. The obtained results show that the fundamental law of contact resistance is confirmed with however different constants considering complexity from technologies. As for the stability of the contact resistance submitted to the climatic an mechanical constraints, new coatings appear to ensure better performance. Finally we found that these technologies commutations must be used with the current lower than 50mA, in order to avoid any phenomenon of short arc to avoid degradations of the layers.