Evolution of the bond interface during ultrasonic Al–Si wire wedge bonding process

Ultrasonic wedge bonding is one of the most important interconnection techniques for IC dies inner circuits with the outer world for the power and signal transportation. There is a significant effect of the bonding parameters to the joint quality and reliability. Via the chemical etching method, the bond configuration and interface characteristics were observed. It was found that the bond interface outline changed from the shell-nut to the circular pie shape with the increase of the ultrasonic power, furthermore, the actual joining position developed from the bond peripheral to the central, then to the whole bond interface. From the point of view of the stress distribution and the deformation energy, the essence of the bond interface formation was given.