Abstract:

The performance of a bare metal electrical contact may be seriously impaired by the formation of surface films in the contact area.  The growth of surface films is influenced by the anion diffusion process in the contacts.  The present paper examines the effects of mechanical contact stress, electrical voltage drop across the contact area and environmental temperature on the film growth in a single contact spot.  The electrical resistance of a contact spot is examined for some common contact metals, such as aluminum, copper, and nickel, subjected to corrosive environments.  An equation, based on the fundamental diffusion mechanism is derived for the life cycle resistance in a contact material as a function of environmental temperature, contact stress and voltage drop across the contact area.  Resulting curves of resistance versus time are similar in trend and shape to curves measured experimentally by other researchers.  This approach also provides a means to gain insight into the correlation between the lifecycle, electrical contact resistance and such key design variables such as contact normal force, applied electrical voltage, and environmental temperature.

Index Terms:

Electrical Contacts, Lifetime Resistance, Surface film, Diffusion, Asperity, Voltage Drop, Stress

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