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Wire bonding is a key technique for electrical interconnections between integrated circuit (IC) and the metal frame or printed circuit board (PCB). One of the most common wire bonding system is bonding of the Au wire to Al metallization, however, Cu wire is being considered as replacement for Au wire due to surge of Au price. This research focuses on the formation and growth behavior of Cu/Al intermetallic compounds (IMCs). In order to investigate IMC growth after 30, 60 and 120 min of aging at 270, 300 and 330°C, cross-section of Al, Cu and Cu/Al IMCs were examined by scanning electron microscopy (SEM). The results showed that the consumption of the Al layer is more rapid than that of Cu layer, and that after 120 min at 330°C the Al layer is entirely consumed. The formation of three distinct Cu/Al IMC layers was observed. Scanning transmission electron microscopy (STEM)/energy-dispersive X-ray spectroscopy (EDS) was used to identify the three IMC layers formed at the interface. In addition, the IMC compositions were identified by selected-area diffraction pattern (SAD). These were CuAl, Cu 3 Al 2 and Cu 9 Al 4 . Also, the activation energies of Cu/Al IMC growth were obtained from an Arrhenius plot.

This research focuses on the formation and growth behavior of Cu/Al intermetallic compounds (IMCs). In order to investigate IMC growth after 30, 60 and 120 min of aging at 270, 300 and 330 ˚C, cross-section of Al, Cu and Cu/Al IMCs were examined by scanning electron microscopy (SEM). The results showed that the consumption of the Al layer is more rapid than that of Cu layer, and that after 120 min at 330 ˚C the Al layer is entirely consumed. The formation of three distinct Cu/Al IMC layers was observed. Scanning transmission electron microscopy (STEM)/energy-dispersive X-ray spectroscopy (EDS) was used to identify the three IMC layers formed at the interface. These were CuAl, Cu 3 Al 2 and Cu 9 Al 4 . Also, the activation energies of Cu/Al IMC growth were obtained from an Arrhenius plot.