Vibration and bondability analysis of fine-pitch Cu wire bonding

In this paper a novel simulation procedure combining die-level vibration analysis and transient simulation of free air ball (FAB) and multi-layer pad structure subjected to impact and ultrasonic load from capillary are developed. In transient wire bonding simulation, substrate, dies and die adhesive of package are modeled using support springs in which the corresponding spring coefficients represented deformable characteristics of die stacking structure are obtained from die-level vibration analysis. Natural frequencies and stiffness matrixes of stacked dies structure with different overhang lengths as well as plastic works of wedding surfaces of FAB and pad are carried out numerically to evaluate their bondabilities. Experimental tests are also carried out. The results show that stiffness of stacked dies structure and plastic work of pad structure have significant effects to copper (Cu) wire bondability.