Abstract
Solid–liquid interdiffusion bonding of Cu was carried out at 573 K with deposited Sn and Cu films. The effect of Zn addition to the faying surfaces was investigated to reduce Kirkendall voids. At the beginning of the reaction, molten Sn reacted with Cu to form Cu6Sn5, and Cu3Sn successively formed between the Cu6Sn5 and the Cu. Many voids formed in the Cu3Sn phase, especially close to the Cu3Sn/Cu interface. When Zn was added in the faying surfaces, Zn was segregated near the interface of Cu/Cu3Sn and the grain boundaries of Cu3Sn. The Zn segregation inhibited diffusion of Cu due to the effect of solute drag, which also delayed growth of the Cu3Sn layer. As a result, the fluxes of Cu and Sn via the Cu3Sn phase were balanced out, which reduced the Kirkendall void formation.
