Cast Leads for Surface Attachment

The attachment of leadless integrated circuit packages to printed circuit (PC) substrates is receiving growing attention as surface mounting technology advances to meet the demands of present and future product designs. The reliability issues associated with surface attachment of these packages continue to be addressed and characterized with respect to package configuration, material properties, and interconnection methods. A novel technique is introduced for reliable and economical attachment of leadless integrated circuit (IC) packages to circuit substrates. Known as the cast lead process, it is based on a concept for controlling solder joint geometry in order to improve the stress and strain distributions within the joints. The basic sequence of operations established for cast lead fabrication and for surface mounting of processed packages will be presented and results for several reliability studies will be discussed.