Abstract :
Conventional flip-chip solder bumping, utilizing masks, evaporation, and plating equipment, is ideally suited for the mass production of components. Large batches of wafers can be deposited with multilayer solder at a single time. However, this process can be excessively costly, time consuming, and unnecessary for small, specialized applications. A process has been developed to solder bump individual pads, one at a time, without the need for expensive masks, evaporation chambers, or die layout information. This information, critical for solder bump placement, is typically not available to sources outside the design house. Using a standard ball wirebonder and specialized bonding wire, solder bumps can be formed on both Al and Au bond pads of integrated circuits (IC) using thermosonic bonding in a forming gas (hydrogen-argon) atmosphere. The bonding effectively wets the solder bump to the pad without the use of special intermetallic adhesion layers. This process can cut prototyping time and cost by eliminating the need for elaborate equipment and complex solder compositions without sacrificing electrical or thermal performance
