The Relationship Between Surface Wear and Contact Resistance During the Fretting of In-Vivo Electrical Contacts

A study of the high frequency intermittency events occurring during the fretting of contact surfaces used for in-vivo electronic systems, is presented. The emphasis of the study is to determine and the relationship between the contact resistance during the fretting process and to relate this to surface wear, as a function of the applied force. The emphasis is on fretting experiments in the crossed rod configuration with a range of contact forces, between 1.75 and 0.05 N. An established test system and test methodology are used for the study, but in the paper the additional control of the contact force and the measurement of the surface wear using a 3-D surface scanning system is introduced. The level of the applied voltage and current are critical in defining the intermittency events; in this study a dry circuit test, with 20 mV and 100 mA supply is used. The results show that for the materials used, intermittency events occur during every fretting cycle after an initial settling period; that the contact force level is directly coupled to the wear in-line with established theory; and that the minimum contact resistance is linked to the established relationship with force.