Improvement of moisture resistance in plastic encapsulated MOS-IC by surface finishing copper leadframe

In recent years, the demand for copper alloy lead-frame materials has been rising. This is due to deterioration of the reliability of plastic-encapsulated ICs because of larger chip size and increased heat generation from more densely integrated chips. However, copper alloys may form a thick, brittle oxide film on the surface as a result of heating during packaging, thus reducing moisture resistance. The surface finishing process for copper alloy lead-frame materials was studied to overcome this problem. It became evident that the improvement of adhesion to resin is effective in preventing the penetration of moisture into the package. This resulted in the development of an Sn-Ni-plated copper lead frame that enhances the moisture resistance