New Developments in Wire Bonding for Future Packages

摘要

In recent years the bonding wire market has been moving to ultra fine wires below 23μm. The world wide average diameter has moved from 26.5μm in 2002 to 25.2μm in 2006. Leading edge applications are now using 18μm in mass production. Driving forces are the decreasing package size and the trend to multifunctional,highly integrated packages like SiP or SoP. Also cost reduction programs have a serious influence on wire diameter reduction. In terms of bonding wires the diameter must be reduced while keeping high tensile strength and good bondability. Also reliability must be ensured. Consequently the wire properties must be adjusted for all the new application. rnThis paper will focus on the recent development of new bonding wire types for high reliability as well as for fine pad pitch (50-60 μm) application. The influence of dopants to adjust material properties will be shown for different gold wire types of various grades from 99 to 99.99 % gold content. State of the art analytical investigation methods are used to determine high resolution cross sections of interconnections in order to obtain a better understanding of intermetallic phase growth phenomena. Results for typical tests like high temperature storage test will be shown. The technological barrier of bonding wires as well as future challenges will be discussed. This includes mechanical as well as materials points of view. An outlook for future potential emerging technologies e.g. room temperature bonding of gold wire,use of aluminum ribbons will be given.