The simulation of micro droplet behavior of molten lead-free solder in inkjet printing process and its experimental validation

Micro droplets of molten lead-free solder were ejected at 230 °C using a piezoelectric inkjet printing process. The effect of the micro droplet formation of molten lead-free solder was investigated on the pulse time of the waveform. In this study, a numerical system for simulating the shape evolution of micro droplet of molten lead-free solder in the inkjet printing process was developed based on a solution algorithm (SOLA) scheme for the solution of velocity and pressure fields. It is coupled with the volume-of-fluid (VOF) and piecewise-linear interface construction (PLIC) techniques for the transport of mass and construction of the interface. For the treatment of surface tension effects, a CSF (continuum surface force) model is employed. The simulation results were validated with experimental observations. The numerical result was used to understand the mechanisms of the extrusion of the liquid column, the contraction of the liquid thread, and the pinch-off of the liquid thread at the nozzle exit.