Droplet formation study of a liquid micro-dispenser driven by a piezoelectric actuator

The piezoelectric-driven noncontact jetting dispenser with the characteristics of high accuracy, efficiency and applicability has been widely applied in the microelectronics packaging field to produce small droplets. The process of droplet formation and separation is the key to successful jetting. In order to study the process and show the roles of system parameters in droplet formation, the paper runs some numerical simulations and analyzes the comprehensive effects of the system parameters on the morphological change of droplets by using two dimensionless parameters Weber and Reynolds. The simulation and experiment results show that the scale of system parameters is confirmed by the lower and upper limits of Weber according to different Reynolds. If Weber is bigger than the upper limit value or smaller than the lower limit value, the jetting failure like sputtering, satellite dots jetting or adhesion will occur. During the experiments, the system parameters should be adjusted to keep the values of Weber and Reynolds in the proposed scale. The findings in this paper can be used to guide the design and control of these piezoelectric driven dispensers.