Abstract
The electromigration effect upon the γ-InSn 4 /Cu interfacial reactions have been studied by examining the γ-InSn 4 /Cu/γ-InSn 4 couples annealed at 160 °C with and without current stressing. Scallop-type η-Cu 6 (Sn,In) 5 phase layers are formed in the couples without current stressing and at the γ-InSn 4 /Cu interface where electrons are flowing from the γ-InSn 4 to the Cu. The reaction path is Cu/η-Cu 6 (Sn,In) 5 /γ-InSn 4 . However, very large η-Cu 6 (Sn,In) 5 compounds are found at the Cu/γ-InSn 4 interface where electrons are from Cu to the γ-InSn 4 . Although the melting points of both γ-InSn 4 and Cu are higher than 160 °C, the liquid phase is formed at 160 °C in the electrified couple at the downstream γ-InSn 4 phase near the Cu/γ-InSn 4 interface. The reaction path is Cu/η-Cu 6 (Sn,In) 5 /liquid/γ-InSn 4 . The liquid phase propagates along the grain boundaries of the γ-InSn 4 matrix. The very large η-Cu 6 (Sn,In) 5 compounds are the coupling results of the liquid phase penetration and the Cu transport enhancement due to electromigration. © 2006 Materials Research Society.