Structure characteristics and evolution at wedge bonding interface

A series of experiments was carried out on structure characteristics and evolution at the bond interface.Bond lift-off characteristics were studied by using scanning electron microscope with energy dispersive spectroscope.Power characteristics of piezoelectric transducer were analyzed by the driving electric signal measured.Results show that the pattern of partially bonded material at the Ni-Al interface of ultrasonic wedge bonds exposed by peeling underdeveloped bonds simulates a ridged torus with an unbonded central and external region rubbed along pulse direction.Bonding strength is located between the severely ridged torus and the non-adhering central and external area of the bond.For the same variables,ridge-peak and transforming ultrasonic energy of first wedge bonding are greater than that of second wedge bonding.For other variables constant,with increasing load,the total area of bond pattern increases in size,and minor axis of torus extends major axis;with increasing time,the ridged periphery spreads a whole torus,and the ridged location of the bonded region moves closer to the bond center;the sliding trace and the ridge-like of the bond pattern strengthen when more power applied.