Spreading behaviors of silicone droplet impact on flat solid surface: Experiments and VOF simulations

Silicone, as the carrier of phosphor powder in the phosphor coating process of white light emitting diode (LED) packaging, its spreading behaviors will influence the morphology of phosphor layer and thus affect the optical and thermal performances of light emitting diodes (LEDs). In this paper, the spreading behaviors of a silicone droplet impact on a flat silicon surface was experimentally and computationally studied. Droplets with the same volume (R=1.1±1%mm) were deposited on a flat silicon substrate at a range of weber number from 5 to 20, morphology change of silicone droplets was captured using a high-speed digital camera. A computational fluid dynamics (CFD) model, based on the volume of fluid (VOF) approach, was used to simulate spreading behaviors of a silicone droplet using the same boundary condition getting from experiments. Time evolution of dynamic radius R(t) and dynamic contact angel θ(t) were analyzed. The CFD simulation results were compared with the experiment results, and the simulation results showed good agreement with the experimental data which indicated that a VOF-based computational model was able to capture key features of the interaction of a silicone droplet with flat solid surfaces.