Effects of Gold-aluminum Intermetallic Compounds on Chip Wire Bonding Interconnections Reliability

Intermetallic compounds formation is well-known problem for gold wire to aluminum pads bonds. The causes are in high fragility and low conductivity of some Au-Al system intermetallic phases. However, gold wire bonds to aluminum bond pads continue to be activity used. The reliability of these bonds depends on many factors. Introduction of other materials in Au-Al system, mounting process parameters, type of mounting tool and structure of the formed bonds are some of these factors. This article considers effects of aluminum pads structure on gold wire bonding reliability. Two types of pads were studied in this paper. It is pad with 1,5-2,5 um aluminum thick and pad with 5-10 um aluminum thick. As shown the results pads with 5-10 um thick allow to achieve greater reliability compared to pads with 1,5-2,5 um thick. As a result, it was found that under equal conditions the bonds on pads with greater thickness show acceptable mechanical strength (9.5 centinewton in pull test), while the bonds with thinner pads are destroyed.