Influence of Sputtering Conditions to Photoresist Profiles and Bump Shapes after Plating

Gold bumps are conventionally used for interconnection of TAB (Tape Automated Bonding), COF (Chip on Film), or COG (Chip on Glass) in the driver LSIs of liquid crystal displays for mobile devices. These bumps are generally formed using cyanide-free gold electro-plating, since electrolytes containing cyanide tend to damage organic photoresist. However, a cyanide gold-plating bath for printed writing boards is also sometimes used to make gold bumps. This study investigated the gold sputtering influence on photoresist profiles and bump shapes after gold deposition.