Fine pitch copper wire bonding on copper bond pad process optimization

Abstract

The development of a new copper wire bonding process for fine pitch applications is currently in progress. The bond pad cleanliness and oxidation levels are important for the ball bond (first bond). By applying an organic coating layer it is possible to protect the copper bond pad from oxidation. Copper wire in an unopened sealed spool already has a thin layer of copper oxide on the surface and does not readily weld (stitch bond) to silver spot plated lead frames and BGA substrates with Au metallization. The intent of this study is to establish the effects of the process parameters for a wire bond process with copper wire with an initial bond pad of 70 /spl mu/m. The copper ball bond on copper bond pad and copper wire stitch bond on silver spot plated lead frame and BGA substrate as well the materials were studied.