Performance Characteristics of a Jetting Dispenser Featuring Piezostack and Flexible Beam Mechanism

Abstract:

This paper presents a new type of jetting dispenser driven by a piezostack. Via a flexible beam mechanism, the amplitude of a needle motion is amplified to such a value that can make a dispensing of medium and high viscosity adhesive. By designing the flexible beam with high resonant frequency, the dispenser can operate at a frequency much higher than that of conventional dispensers. Therefore, it is expected that the dispenser can provide very small dispensing dot size at high dispensing flow rate, which is imperatively required in modern semiconductor packaging processes. Furthermore, the dispensing flow rate and dot size can be effectively controlled by driving voltage applied to the piezostack. After describing the mechanism and operational principle of the dispenser, a mathematical model of the system is derived by considering dynamic behaviors of structural parts such as the piezostack, the flexible beam and the needle structure, and the adhesive fluid dynamics. In the modeling, a lumped parameter method is applied to model the adhesive dynamics and the governing equation of the whole dispenser is then derived by integrating the structural model with the fluid model. Based on the proposed model, the dispenser is designed and manufactured. Subsequently, dispensing performances such as a dot size and dispensing flow rate are experimentally evaluated.