Performance evaluation of a high-speed jetting dispenser actuated by a ring-type piezostack

Abstract

This article presents performance results of a new type of jetting dispenser driven by a ring-type piezostack actuator. The proposed dispenser can provide a very small dispensing dot size of a low viscous adhesive, from 50 to 500 cp, at a high dispensing flowrate in semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the system is derived by considering behaviours of the piezostack, the actuating spring, the dispensing needle, and the adhesive fluid dynamics. In the modelling, a lumped parameter method is applied to model the adhesive, for which the rheological property is approximately expressed by the Bingham model. The governing equation of the dispensing system is then derived by integrating the structural model with the fluid model. Based on the proposed model, the jetting dispenser is designed and manufactured. The dispensing performances such as dot size and dispensing flowrate are then evaluated from both the proposed model and experimental investigation. Subsequently, a method to control the dispensing flowrate is proposed and applied to the proposed dispenser to achieve the desired dispensing amount.