The Formation of Insulating Organic Films on Palladium-Silver Contact Alloys

The formation of insulating organic films on palladium and various palladium-silver alloy contacts at low voltages in the presence of organic atmospheric contaminants during slide has been investigated on a specially developed equipment, and the performance of the various materials in terms of contact resistance measurements have been compared. The pollutant (iso-propyl alcohol) and its concentration (20 parts per million) were chosen to simulate conditions in an electromechanical relay in which the plastic materials had been carefully chosen for their low organic evolutions. Diagrams summarizing the contact resistance measurements and comparing deposits formed over 5 X 10⁶operations are given. These show that under the test conditions some organic deposits form on all the materials studied except pure silver. However, there is a very large decrease in both the maximum contact resistance measured and the amount of deposit formed when 70% palladium-silver is compared with palladium, and there is a further significant steady improvement when the lower palladium alloys are examined.