Contact resistance increase in palladium material as a result of mechanochemical reaction.

In small-size relays used under low current, mechanical actions of contacts at make-break, such as impact and wipe, can affect contact deterioration more than electric factors such as arcing and Joule heat. In this article, the effects of vertical impact and horizontal wipe were studied in separate experiments in order to clarify the mechanism by which a palladium oxide film is formed on the contact area and the contact resistance is rapidly increased by make-break operations under no load in air. The experiments show that the main factor of contact resistance increase is the formation of an accumulated layer made of insulation powders by wipe action. Based on this fact, models of contact surface condition during operations are suggested to explain the variation of contact resistance. In addition, the effect of passing current through the contacts is also explained by the models. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 2, 80(2): 33–44, 1997 [ABSTRACT FROM AUTHOR]