Studies of microstructure characteristics and evolutions at the bond interface in bonding technology

To enhance thermosonic bond development, an improved understanding is needed of the processes taking place at the bond interface. In this paper, lift-off and section characteristics at the interface of thermosonic bond were observed by using scanning electron microscope with EDS-test. It is obvious that the peeling underdeveloped bonds simulate a torus (or doughnut) with an unbonded central region and ridged peripheral region is bonded hardly. Bond strength is located between the severely ridged periphery and the non-adhering central area of the bond. For constant force and time, the ridged area of the bond pattern increases when more power is applied. For constant force and power, the ridged location of the bonded region moves closer to the bond center with time. Au-Al and Au-Ag microstructures were identified by EDS-tests, and 'Kirkendall' diffusibility in Au-Ag interface and inter-metallic compounds in Au-Al interface were confirmed. And these would be helpful for further research about thermosonic bonding.