Dynamic finite element analysis on underlay microstructure of Cu/low-K wafer during bonding process

In the present paper, the tensile mechanical properties of thin gold wire before/after electric flame-off (EFO) process have been investigated by self-design pull test fixture. Microstructure characteristics of free air ball (FAB) and heat affected zone (HAZ) are also carefully investigated. The accurate experimental material data should be reflected as input for precise finite element analysis. Numerical model based on explicit time integration scheme software ANSYS/LS-DYNA is developed to simulate the ball bond of wire bonding process. Because the crack of low-K layer and delamination of copper via are observed, dynamic transient analysis is performed to inspect the overall stress/strain distributions on the microstructure of Cu/Low-K wafer. Special emphasizes are focused on the copper via layout and optimal design of Cu/Low-K microstructure. A series of comprehensive parametric studies were conducted in this research.