Theoretical Investigation of Oxide Fracture during Ultrasonic Wedge Bonding

This research investigates the fracture of the native oxide layer on an aluminum bonding pad and aluminum wire during ultrasonic wedge bonding. Three different models are used in the approach: a 2D global finite element method (FEM) model, a separate micromechanical oxide film breakage model, and a FEM unit cell model. The 2D global FEM model provides stress data to be input into the other two models while the micromechanical oxide film breakage model predicts the level of oxide fracture and the unit cell model investigates the underlying assumptions of the oxide film breakage model. The oxide film breakage model shows slightly more breakup in peripheral regions for the pad’s oxide layer initially before achieving an even aspect ratio throughout the contacting area. The wire’s oxide layer approaches its final, even aspect ratio more quickly. The oxide film breakage model needs to be improved by taking into account the level of plastic deformation in the base material