Investigation on the influence of thermal ultrasonic bonding process on the mechanical property of bonding weld by molecular dynamics simulation

With the constant development and improvement of wire bonding technology, thermal ultrasonic bonding technology has a widely application in wire bonding process. However, the mechanism of wire bonding has not been fully explained yet. In this paper, molecular dynamics simulation is employed to establish an Au-Cu wire bonding model and the mechanism of thermal ultrasonic bonding is investigated at the atomic scale. The study focuses on the bonding weld formation during the bonding process, and the wire-pad separation behavior during tensile testing. The results of molecular dynamics simulation indicate that during the wire bonding process, intermetallic compounds (IMC) are unavoidably generated between the wire and pad because of atomic interdiffusion, and a strong adhesion generated at the bonding weld creates robust wire-pad bonding. Subsequently, the dominant factor affecting the bonding attractive force is identified and the degree of influence of process parameters on the index is defined through experimental design method. Thus, it provides theoretical guidance for the design and optimization of thermal ultrasonic bonding process parameters in engineering applications.