Cu wire bonding on Cu-Ni-Pd bond pad and leads: From development to robust production

Abstract

Summary form only given. This paper will describe copper wirebonding on Cu-Ni-Pd bond-pad and leadframe in QFN packages using thicker wires, i.e 1.3 & 2.0mil wires. The paper introduces bonding and reliability challenges with Copper wire on Al bond pads as experienced by many Process Development Engineers. TI analog devices which mainly used BOAC dies using Cu-Ni-Pd bond-pads and copper-wire combination have reduced these challenges tremendously. Description of equipment copper kits used in development from both K&S and ASM bonders will be covered. Free-Air-Ball, Bonded Ball, and Stitch bond characterization, Intermetallics and also reliability data will be discussed. Comparison and selections of the best copper wire, capillary design features and special bonding parameters to ensure robust bonding process for seamless production will be shared including bondability and reliability tests results. These success factors will be explained in detail including methodology used during ramp that have enabled TI to build billion units to-date with Copper wires.