Effect of Au, Pd and Pt addition in Cu on the growth of intermetallic compounds and the Kirkendall voids in the Cu–Sn system

Abstract

The growth rates of the product phases Cu3Sn and Cu6Sn5 in the Cu–Sn system are affected differently by the addition of Au, Pd and Pt in Cu. The addition of 8 at.% of Au and Pd in Cu produce different (and additional) phases in the interdiffusion zone of ternary Cu(Au)/Sn and Cu(Pd)/Sn diffusion couples, respectively, when compared to the binary Cu/Sn diffusion couple. The addition of Au has very little effect; however, the addition of Pd and Pt significantly increases (both size and number) the formation of the Kirkendall voids. This study clearly indicates that addition of these components (i.e., inorganic impurities) have similar detrimental role like organic impurities in Cu on the growth of the Kirkendall voids, which leads to the degradation of flip–chip bonding in an electronic component.