| A kind of low power connector used e.g. in household appliances was failed in routine experiment. One housing was partly burned; the other was burned out and melted completely. The heat sources were four paralleled contacts constructed by springs (Sn/Cu) in socket and a plug sheet (Ni/Steel) while mating. The contact interfaces were detected by scanning electronic microscope (SEM) and X-ray energy dispersive spectroscopy (XEDS), obvious wear tracks and various contaminants, involved in element Si, Al, Na, K, S, Cl, O etc., were found in the partly burned connector. The contamination degrees on four paralleled contacts were different, so that the ratio of average contact resistance on four contacts was about 5:8:3:1. By measurement, the maximum contact resistance on contacts of the plug sheet attained to 28Ω. The main failure reasons of the partly burned connector were fretting and contamination between the contact interfaces. For the completely burned connector, one of the four springs was distorted badly, so the resistances of four contacts were different.Fretting simulation showed that connection resistance of connectors was raised up, even to ohms level. In fretting simulation under high current, the connection resistance depressed as the current increased and attains to a balanced value which is formed by the integrated effects of both fretting, fritting and intenerating of current.The heat generated by contacts increased as the current increased. The ANSYS model analysis showed that the contact material melted when the current increased to 4.22A. By the thermal analysis, it was estimated that the connector would be burned under the lower current if the current was not evenly distributed on four paralleled contacts caused by uneven contamination. In this paper, improvement methods for connector failure were also discussed, including the redesign of connector's structure, the change of the plating on contacts, and the limitation of contamination.
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