AU-SN BONDING METALLURGY OF TAB CONTACTS AND ITS INFLUENCE ON THE KIRKENDALL EFFECT IN THE TERNARY CU-AU-SN

This paper summarizes the works done on different Au-Sn-Cu and Au-Cu m etallurgies in the inner lead bond area. The influence of Kirkendall p ore formation in the Cu-Au-Sn system as a degradation mechanism is sho wn. This effect, together with the formation of new types of ternary i ntermetallic compounds, is observed during thermal aging in contacts w ith a direct interface between the eutectic 80/20 Au-Sn alloy and copp er. The Zeta-phase (Au/Sn 90/10) acts like a diffusion barrier, which inhibits the pore formation associated with copper diffusion. The comp osition of the ternary intermetallic compounds, their growth constant, and activation energy was determined. The possibilities to increase t he contact reliability by producing a reliable Au-Sn metallurgy during the ILB process are shown.