Optimized contact erosion by using electronegative gases in telecom relays

Abstract

Although telecom or signal relays are mainly used to switch low level signals, they frequently must handle higher DC as well as AC loads. Depending on the voltage or current applied, significant contact erosion and/or material transfer can cause sticking. The investigations were performed at typical loads for the most commonly used contact material, AgPd60, in a nitrogen (N/sub 2/) switching ambient, compared with the new erosion resistant PdRu10 material, in nitrogen and in sulfur hexafluoride (SF/sub 6/) atmospheres with 30 and 100% SF/sub 6/. The investigations showed higher material transfer on contact makes than on contact breaks. The reason for the higher contact erosion during make operation is due to bouncing, because a make operation consists of several make and break operations in sequence. PdRu10 and AgPd60 in N/sub 2/ ambient showed by far the highest material transfer with craters and spikes in the range of up to 120 /spl mu/m and 75 /spl mu/m respectively. PdRu10 in SF/sub 6/ showed significantly less material transfer (factor of 3) and therefore also no sticking. Replacing the most commonly used combination of AgPd60 operating in N/sub 2/ with PdRu10 in SF/sub 6/ results in a significant performance increase. Considering all the other advantages, especially the excellent dielectric performance of SF/sub 6/, PdRu10 working in an SF/sub 6/ ambient results in a very good switching performance.