Experimental and Modeling Study of Breakup Behavior in Silicone Jet Dispensing for Light-Emitting Diode Packaging

Silicone jet dispensing has grown increasingly common in light-emitting diode (LED) packaging owing to its high speed and low cost. However, differences in breakup behavior result in different silicone jetting volumes that create challenges in maintaining dispensing volume consistency during silicone jet dispensing process; this severely affects the performance of LED packaging. To reveal the breakup behavior during the jet dispensing process, the experimental and modeling studies were conducted. First, the ultrafast breakup process was experimentally observed using a high-speed camera, which shows that this process only requires approximately 50 ms. Then, an analytical model was developed and verified through an experiment. Using this analytical model, the effects of initial disturbance amplitude, initial disturbance wavelength, and thread length on the thread breakup were studied. The simulation demonstrated that it is necessary to control the disturbance amplitude under 0.005 for volume consistency in jet dispensing; thus, a moving work piece rather than a moving nozzle is recommended in jet dispensing. A disturbance wavelength between 0.3 and 0.6 mm is beneficial for both thread breakup and high-volume consistency. Thread length has little effect on the breakup position but significant effects on the volume consistency and breakup time. A low substrate increases the volume and the consistency of thread breakup. This paper will provide a useful guide for dispenser designs of modern LED packages.