Sockets: considerations as an alternative to direct surface mounting of components

Abstract

Because the surface mounting process results in plastic package cracking, it has been suggested that sockets be used to avoid the problem. The authors examine the reliability of plastic leaded chip carriers (PLCCs) in two commonly used sockets. Components are found to have different planarity problems than are commonly found in surface-mount assembly. The engineering factors considered in choosing the appropriate leadframe material must change when sockets are used. There are also serious vibration-induced problems which limit the number of manufacturing application areas in which sockets may be of reliable use. Restraining clips placed over the devices were examined to determine if simple modifications could be implemented to improve the vibration-induced problems. Dissimilar coatings between the package leads and the socket contacts are examined and discussed, as is the environmental stress range over which these sockets are of practical use in a manufacturing environment.<>