Acceleration Factor for Tarnish Testing of Silver Contact Surface

Terutaka TAMAI, Yasuhiro KURANAGA

Summary :

Silver is a fundamental material for electrical contact application. In spite of high electrical conductivity and economical advantage, silver surface is corroded easily by environment contained sulfide. A corrosion product as Ag₂S deteriorates the property of contact reliability. In order to examine contact reliability, the acceleration tests have been accepted widely in industries. In the present study, the acceleration factor of the contact reliability for the sulfide film on the surface of silver contact which was subject to the tarnish acceleration test was clarified in comparison with the film grown in a normal office environment. The accelerated environment based on the Japan Electric Industry Development Association (JEIDA) standard No.25 was adopted. This environment is consisted of air contained 3 ppm H₂S gas under 40, 85-95% RH. The growth rate of the sulfide film (Ag₂S) was evaluated by applying the ellipsometry analysis. In the results, it was found that growth of Ag₂S film of 500 in thickness in the normal office environment required corrosion time of 310³ h. This thickness of 500 caused increase in contact resistance of 0.1-1.0 (Ω). However, in the accelerated environment, corrosion time decreased to 1.7 h for same thickness. Therefore, the acceleration factor was obtained by comparison of these time as 1.810³ for the standard test of JEIDA.

• Publication: IEICE TRANSACTIONS on Electronics Vol.E78-C No.9 pp.1273-1278
• Publication Date: 1995/09/25
• Type of Manuscript: PAPER
• Category: Electronic Circuits

Authors

Terutaka TAMAI
Yasuhiro KURANAGA

Keyword

acceleration factor,  tarnish,  silver,  electrical contact,  Ag₂S film