Clustering and the spatial distribution of contact spots at a real un-dismantled electrical contact interface

Contact maps of an electrical interface are acquired using an x-ray computer tomography technique without the need for dismantling the specimens. These maps consist of approximately 1500 × 1500 pixels with each pixel relating to an 8.0 µm by 8.0 µm by 8.0 µm volume at the interface. The specimens consist of a cable lug bolted to a printed circuit board at various contact normal forces of between 0.8 and 3.2 kN. The contact maps reveal a complex network of contacting 'islands' with meandering perimeters consisting of contacting 'peninsulas' and non-contacting 'fjords'. The fractal characteristics of the spot spatial distribution show similar behaviour to the fractal characteristics of the spot size distribution.