Effect of Humidity on Growth of Oxide Film on Surface of Copper Contacts

Terutaka TAMAI  

IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.7   pp.1391-1397
Publication Date: 2007/07/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.7.1391
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Development of Electromechanical Devices (Selected Papers from ICEC2006))
Category: Contact Phenomena
humidity,  electrical contacts,  copper oxide,  adsorbed H2O film,  contact failure,  

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Contact surfaces are exposed to the atmosphere in general applications. Therefore, gases in the atmosphere such as oxygen and H2O are adsorbed on and react with the contact surface. Products formed on the surface such as copper oxide films degrade contact resistance characteristics. This surface contamination is an important problem for electrical contact applications. The author has studied the effect of humidification on contact resistance characteristics. In this paper, the effect of humidity on the growth of an oxide film on a copper surface was clarified. An increase in the humidity results in a decrease in the thickness, in contrast, a decrease in the humidity increases the thickness linearly. Changes in the oxide film thickness based on the level of humidity were measured by ellipsometry. Surface state changes influenced by humidification were analyzed topographically using a scanning tunneling microscope. The mechanism of the effect of humidity on the film thickness was discussed on the basis of the deduction of the copper oxide film by H2 from the adsorbed H2O. Moreover, the changes in contact resistance levels for both static and sliding contacts due to humidity were measured, and a dependence on humidity was found.