Interfacial reactions of Sn/Ag/Cu tri-layer on a deformed polyimide substrate

Sn/Ag/Cu tri-layer structure was frequently encountered in microelectronic solder joints. In flexible microelectronics, the Sn/Ag/Cu tri-layer structure was usually subjected to strain when the plastic substrate was deformed. This study investigated the Sn/Ag/Cu interfacial reactions on a polyimide substrate subjected to compressive and tensile strain. Under both strain conditions, the Sn/Ag/Cu tri-layer structure was replaced by the multi-layer structure of Sn/Ag 3Sn/Cu 6Sn 5/Cu 3Sn/Cu after 150 and 200 °C of aging. However, blocky Cu 6Sn 5 was formed at the Sn/Ag 3Sn interface subjected to compressive strain but rarely observed at that subjected to tensile strain, revealing that strain was an influential factor to the Sn/Ag/Cu interfacial reactions.