Abstract
The inkjet printing technology and injection molding technology have been widely explored by the electronic industry in developing new manufacture processes. To shorten the design cycle, the numerical simulation of two-phase flow is the required tool. The three-dimensional simulations of two-phase flow based on a numerical scheme comprised of a finite volume formulation for discretizing governing equations of the flow field and a volume-of-fluid method to predict the fluid interface are presented. Non-staggered grid system is used. An interpolation practice of second order accuracy is adopted to calculate the physical quantities at cell-face centers. The deferred correction approach is used to compute the convection and diffusion terms by blending the upwind and central difference scheme. An implicit three-time-level scheme with second-order accuracy is adopted. The SIMPLE algorithm is adopted to treat the velocity and pressure coupling. In the study of the two-phase flow on inkjet printing technology, the surface tension is calculated by a continuum surface force model. The contact angle between the fluid and the solid wall is explicitly enforced at the fluid interface. The numerical predictions of meniscus shape are similar to measurement results which published by other researchers. And then, micro flow visualization and computational results are complementarily presented of the extrusion, detachment, recoil, and free flight of the inkjet droplet column ejected from a commercial piezo-electrically driven inkjet printhead. Subsequently, the verified numerical code is applied to study the influences of surface tension, fluid viscosity, contact angle θs between the droplet and cavity walls and droplet impinging velocity on the deposition process of a microfabrication based on inkjet printing technique. The effects of the surface tension on the deposition process are examined by varying the drop’s surface tension, i.e. σ = 10 dyne s/cm, 28 dyne s/cm, 50 dyne s/cm and 70 dyne s/cm, while the viscosity of the droplet is fixed at μl = 5 cp. The effects of the viscosity on the deposition process are examined by varying the drop’s viscosity, i.e. μl = 2.5 cp, 5 cp and 10 cp, while the surface tension of the droplet is fixed at σ = 28 dyne s/cm. It is found that there exist a critical Reynolds number and a critical Weber number beyond and below which the ink droplet fails to form a layer, respectively. Furthermore, the hydrophilic effects are explored by choosing θs at 10°, 30°, 50°, 70°, 90°, and 120°, whereas the contact angle between the fluid and bottom wall is fixed at θb = 30°. The influences of droplet impinging velocity are examined by increasing its value from 1.0 m/s to 7.0 m/s identifications of a critical contact angle (θs)c, = 70o and a critical range of impact velocities, 5 m/s to 7 m/s. At these critical values the formation of an intact flat film in the cavity is fulfilled. In the study of the two phase flow on injection molding technology, the full Navier-Stokes equations are solved. The rheological property of polymer melt flows is calculated by the modified Cross-WLF model. The first case is the gas-assistant injection molding process of the rectangular plane with half cylinder. The predicted distributions of gas core thickness are compared with the corresponding experimental observation. In the other cases, several three-dimensional characteristics are demonstrated. The numerical results depict important three-dimensional phenomena, such as the jetting effect, race-tracking effect, corner effect, and the flow asymmetry after the gas is injected, which can not be described by any two-and-half dimensional model or Stokes-type three-dimensional methods commonly used in the current commercial CAE simulations for melt flows.