Electromechanical investigation into the influence of MWCNT height on the performance of Au/MWCNT composites for electrical contacts

Au/MWCNT composites have been shown to be a useful contact material for electrical contacts. In this work we have investigated the influence of the MWCNT forest height on both the electrical and mechanical properties. Three heights of MWCNT forest have been investigated (30, 50 and 80 μm, all a sputtered 500 nm Au layer). It is shown that the electrical and mechanical behavior of the 30 and 50 μm composites is quite comparable, whereas there is a large change in the performance where the height is increased to 80 μm. As the MWCNT height is increased the effective hardness of the composite reduces which means that for a given contact pressure, the resultant contact area will be larger for taller MWCNT forests. A larger area combined with a higher resilience to impact is expected to result in larger lifetimes. A consequence of the softer composite with larger contact area is that the molten-metal bridge phenomenon has been shown to increase with MWCNT height. Experimental data is discussed to identify the optimum MWCNT height where the sputtered Au thickness is 500 nm. By analyzing the Au:MWCNT thickness ratio, it is possible to infer the optimum value for other thickness of Au. Combining this data with our model, it is also possible to estimate optimum thicknesses with other contact materials.