A study of switching time and light emission during carbon contact separation

In the field of electrical contacts, carbon has been rarely investigated but carbon is more and more used in the automotive field. This is especially true in membrane switching technology, which is commonly used in the control field such as in remote controls, automotive switches, mobile phones, etc. This technology is based on a mobile contact, mounted on flexible elastomeric parts which are pressed onto a static contact of the PCB (printed circuit board). The contact material is made of a carbon-loaded polymer or a metallic contact pill whereas the PCB is copper-coated with a layer of gold on top. The trend today is to use this technology in more applications requiring higher powers such as relay energizing or direct motor control. As reported in our previous work for such currents <;1A, during break and make, nano-arcs and micro-arcs occur for metallic and rigid contacts. Their duration and subsequent damage highly depends on material and mechanical separation. On the other hand, due to flexibility, the contact resistance of a carbon-loaded polymer pill with metallic PCBs is expected to modify the arc ignition or glowing and induce complex opening voltage characteristics. For these reasons, we present in this paper the electrical and optical characterization of arcing and glowing phenomena which can occur at low voltage and low current on carbon contacts. Considering the possibility of the existence of both phenomena at opening, the main work was focused on establishing correlations between contact voltages and emitted light characteristics. This complex characteristic analysis has provided accurate measurements of minimum currents and voltages and has shown that glowing phenomena take place below the arcing limit and persist at currents and voltages as low as a few milliamps and a few volts. It is clearly demon