Finite Element Modeling of Simultaneous Ultrasonic Bumping With Au Balls

Bumping of microcircuits and substrates establishes interconnect points required for subsequent bonding of microelectronic components, allowing for power and data distribution. Simultaneous ultrasonic bonding of individual Au balls promises to accelerate bumping processes and is studied using a finite element model. The model covers the static forces at the end of a successful bonding operation and analyzes the interfacial stresses between bumps and substrate. The modeling shows the vertical forces acting on the bumps when a lateral displacement of the bonding tool is applied. When designing a practical bonding application, the control of such vertical forces is recommended. A sensitivity analysis is conducted to study the effect of the main factors on the model responses. This analysis reveals that variations in bump height and bonding tool elastic modulus are the major factors affecting the forces on the bumps.