Effects of organic gases (1, 4-butanediol, n-hexane, phenol, and benzene) on the contact resistance (the electrical life and the mechanical life) and the sticking were evaluated. These effects were evaluated by using telecommunication relays from which the cases were removed. Contact materials were Au90Ag10(clad)/Ag40Pd60 (base). Test conditions were as follows: In the cases of the electrical life test and the mechanical life test: Load conditions: DC28 V, 100 mA and 0 V, 0 mA. Temperature: 85. Frequency: 5 Hz. Number of operations: 2,500,000 times. In the case of the sticking test: Load condition: DC96 V, 140 mA. Temperature: 50. Frequency: 5 Hz. Number of operations: 2,000,000 times. It was found that the electrical life was more than 2,500,000 times, the mechanical life was more than 2,500,000 times, and the sticking didnt occur in the case of 1, 4-butanediol. The electrical life was improved by adding 1, 4-butanediol to phenol and benzene, respectively.

Arc discharge between electrodes of relays and switches often causes contact surface damage through material transfer and arc erosion. Especially, material transfer sometimes occurs and brings serious failure even under lower load that is quite smaller than the minimum arc current value of contact material. In this paper, contact surface configuration, material transfer, and arc erosion characteristics of Ag and AgPd 60 contacts were experimentally studied after 0.5 or 1 million switching operations at various load levels. The followings can be made clear. Firstly, it was confirmed that the arcs and material transfer occurred even under such current that was lower than the minimum arc current. Therefore, the definition of the arc occurrence boundary current was newly determined. Secondly, the relation between load conditions (current and power supply voltage) and contact surface configuration (craters and pips) caused by material transfer was studied. The arc erosion behaviors of tested samples could be classified into two types: material transfer type and wear-out type. As one of the primary factors of transition from the former type to the latter one, contact activation was considered. The influences of load conditions and organic gas emitted from relay structure on arc characteristics was experimentally examined. The results indicated that load current greatly influenced the amount of material transfer and that power supply voltage affected the occurrence of the wear-out type significantly. The activation behavior of the contact surface could be found through observing the bridge voltage waveform.