The Effect of Ultrasonic Power in Aluminum Wire Bonding Hardness Profiles

Ultrasonic wire bonding is a critical process used widely across the microelectronics industry. Despite its ubiquity, there is a breadth of literature and ongoing active research into the basic principles of wire bonding. In particular, the effects of ultrasonic bonding on material properties are not fully understood. This thesis presents the effects of different ultrasonic bond powers on material properties. The changes in mechanical properties were measured by collecting Vickers microhardness data and nanoindentation data. The hardness in the bonded wire varied with two parameters: the distance from the bond interface, and the applied ultrasonic power. The hardness varied 5 HV across the profile of a bond and a 5 HV difference was also measured due to change in bond power. In addition, the measured hardness of the bonds was lower by up to 10 HV than calculated hardness values based on strain hardening only. These trends were found with the microhardness data and corroborated by nanoindentation results. This work provides a method to further study the effects of additional bonding parameters on mechanical properties