The Effect of Lubrication on Fretting Corrosion at Dissimilar Metal Interfaces in Socketed IC Device Applications

Abstract

The early failure rate of socketed dual in-line package (DIP) devices that used dissimilar metal interfaces (Sn/Au and SnPb-solder/ Au) have been previously reported by the authors. These high resistance failures (both in field systems and in the laboratory) were attributed to the formation of tin oxide fretting corrosion at the device/socket interface. Lubrication of metal contacts has been shown to reduce or eliminate fretting corrosion in various contact configurations. In this study, the effect of a thixotropic synthetic lubricant, composed of a mixture of an oil and a wax, on the production of fretting corrosion at dissimilar metal interfaces under conditions of very mild vibration is evaluated. The static resistance behavior of these samples was studied for 18 months. The samples were then disassembled and the contact surfaces examined using scanning electron microscopic (SEM) and scanning Auger microprobe (SAM) techniques. The resistance data obtained indicated that all dissimilar metal interfaces failed repeatedly. Only the SnPb/SnPb and Au/Au interfaces showed no significant increases in resistance over the test period. Subsequent SEM and SAM investigations showed that all of the dissimilar interfaces failed due to build-up of tin oxide fretting corrosion resulting in high contact resistances (> 100 \Omega ). It was observed that lubrication was effective in reducing both the amount of and the rate of fretting corrosion, as well as dispersing the corrosion that formed. The greatest reduction of fretting corrosion occurred in the SnPb/SnPb systems such that no resistance failures occurred during the 18 month study.