Au-Sn bonding metallurgy of TAB contacts and its influence on the Kirkendall effect in the ternary Cu-Au-Sn

Works done on different Au-Sn-Cu and Au-Cu metallurgies in the inner lead bond (ILB) area is summarized. The influence of Kirkendall pore formation in the Cu-Au-Sn system as a degradation mechanism is shown. This effect, together with the formation of new types of ternary intermetallic compounds, is observed during thermal aging in contacts with a direct interface between the eutectic 80/20 Au-Sn alloy and Cu. The zeta-phase (Au/Sn 90/10) acts like a diffusion barrier, which inhibits the pore formation associated with Cu diffusion. The composition of the ternary intermetallic compounds, their growth constant, and activation energy is determined. The possibilities to increase the contact reliability by producing a reliable Au-Sn metallurgy during the ILB process are shown