MicroStructural Study of Fretting Contact Caused by the Difference of the Tin Plating Thickness

IEICE Transactions on Electronics (Impact Factor: 0.28). 08/2008; DOI: 10.1093/ietele/e91-c.8.1199


In recent years, there has been increasing demand to miniaturize wiring harness connectors in automobiles due to the increasing volume of electronic equipment and the reduction of the installation space allocated for the electronic equipment in automobiles for the comfort of the passengers. With this demand, contact failure caused by the fretting corrosion is expected to become a serious problem. In this report, we examined micro-structural observations of fretting contacts of two different tin plating thicknesses using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) and so on. Based on the results, we compared the microstructure difference of fretting contact caused by the difference of the tin plating thickness.

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    ABSTRACT: The authors have developed the mechanism which gives real vibration to electrical contacts by hammering oscillation in the vertical direction and also a sliding contact mechanism by a magnetostrictive actuator. By using both mechanisms, the influences of a micro-oscillating on contact resistance are examined. Further, 3D oscillation mechanism has been designed to simulate real vibrations that expanded 1D oscillation mechanism (that is to say hammering oscillation mechanism and sliding contact mechanism) into 3D. And the fundamental characteristics of the mechanism are obtained, such as acceleration and displacement at various frequencies, output wave forms to sinusoidal inputs, and mechanical interferences in the X, Y, and Z-directions of the stage. Experimental results suggested that the mechanism could detect more real degradation phenomenon on contacts by the influences of micro-vibration. However, it is necessary that the mechanism should be improved, for instance, in precision mechanism and in feedback control.
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    ABSTRACT: Due to the recent increase in electronic devices mounted on automobiles, a large number of connectors, especially low-cost tin plated connectors are being used. As a result, their contact reliability has become problematic. Furthermore, for the connectors which are subjected to fretting wear caused by heat cycle and vibrations, the contact resistance increases because of wear of tin and deposition of oxides, which generates problems of poor contact. This study is intended to analyze the change in contact resistance of tin plated connectors from the start of fretting wear to the end of their lifetime from the viewpoint of practical reliability, and to observe the trace and the characteristics of fretting wear microscopically. This study found that wear and oxidation of tin plated connectors start immediately with fretting wear, and thus accumulation of abrasion powder on fretting areas causes connectors to reach to the end of their useful lifetime quickly. Especially, it was demonstrated that amplitude of fretting has a considerable influence on a connector's lifetime. It is made clear that air-tightness, so-called ``gas-tight'' of tin in a fretting area influences fretting wear considerably.
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