Properties And Behaviors Of Cu-Al Intermetallic Compounds On Copper Wire Bonding In IC Packaging

Recent years, as the wide use of 45nm even 32nm technology, IC structures have become more and more complicated. The bottleneck of IC chip’s performance is no longer fabrication but packaging. In all kinds of assembly technologies, as the most traditional and mature one, wire bonding (WB) occupies 90% of IC packaging market. Among them, Au ball bonding is the main one, holding over 95% of all WB technology. But with continuous rising of gold price, packaging cost has become a heavy burden. IC industry is seeking for a new metal material with low cost and excellent performance. Cu is considered to take place of Au and be widely used. However, copper wire bonding has its own limitations and few results are reported on the research of Cu-Al intermetallic compounds (IMC) in bonding process. In the paper, the study is focused on Cu-Al IMC’s properties and behaviors in copper wire bonding, combining theories related with many analysis means such as SEM, TEM and EDS. The research studies Cu-Al IMC’s growing process, its micro-structure, and mechanical performance. Moreover, as the application of copper wire coated with Palladium is a solution to prevent copper oxidation during the bonding process, the paper also gives a systematic study on behaviors of Palladium in Palladium coated copper wire during the bonding process.