Cleaning of thin passivation layers on Ag contact material by vacuum outgassing

Metallic silver is a relatively soft material and a good electric conductor . Therefore, it is a very suitable material for electrical contacts. Howeve r, because silver is not resistant to an atmosphere containing H-2 S, SO2 a nd Cl-2, the surface of the silver contact material must be protected. The well-known surface protection method using a thin gold layer is too expensi ve to be economical. In our study we considered some cheaper passivation th in layers which could prevent the corrosive effects of the environment and, at the same time, assure good electric contact. We chose three different t ypes of passivation thin layers. The first one was deposited by waxing in S ilverbrite solution, for the second layer chromizing was used while the tit anium nitride layer was deposited by sputtering. The contact material used was AgNi0.15. Besides the electrical properties of the material, its clean surface is very important to achieve good electric contact and low level of contact resistance. In the high-vacuum outgassing equipment designed and d eveloped in our laboratory samples of silver contact material were outgasse d for 48 h in high vacuum (1 x 10(-7) mbar) at 200 degreesC. Analysis of th e outgassed substances with a quadrupole mass spectrometer showed that the outgassing rates of all the three passivation layers were low while the com position depended on the type of the layer. The resulting thin layers were analyzed with the Auger electron spectroscopy. (C) 2001 Elsevier Science Lt d. All rights reserved.