A model to describe intermittency phenomena in electrical connectors

Fretting is known to be a major cause of contact deterioration and failure, particularly in tin-plated contacts. During fretting the contact resistance generally increases slowly with time. Superimposed to this slow increase in contact resistance are rapid changes in contact resistance within fractions of a second, called intermittences or short duration discontinuities. High-speed measurements of contact voltage-drop and contact current have been carried out and the results are evaluated using general contact theory. It is shown that sudden changes in contact resistance can be caused by a surface film and by melting of current carrying asperities.