Abstract
Wire bonding technology has been utilized in semiconductor packaging industry for electrical connections. Due to low cost, good conductivity, softness and the ability to be bonded under room temperature, Al wire bonding has been considered as a potential candidate to replace the Au and Cu. This study investigates microstructural evolution and failure mechanisms of 2 mil Al wedge-wedge bonding bonded on Cu pad under current density of 2 and 7×10^4 A/cm^2 at 150 ℃. During electromigration tests, resistance decreased first and then increased till wires failed. Though the growth of intermetallic compounds (IMC) at the bonded interface change insignificantly after electromigration tests, the thickness of IMCs at the bonding interface where electron flowed form Cu to Al is usually larger than that at the interface where electron flowed in the opposite direction. Furthermore, considerable grain growth, bamboo structure and bamboo nodes were observed in Al wires. The corresponding mechanism of IMC growth at the interface, resistance change and as well as the formation of bamboo nodes were discussed.