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Numerical Simulation of Epoxy Dispensing in LED Encapsulation
1Faculty of Bioengineering and Technology, Universiti Malaysia Kelantan, Jeli Campus, 17600 Jeli, Kelantan, Malaysia
2Energy Commission, No. 12, Jalan Tun Hussein Precinct 2, 62100, Putrajaya, Malaysia
3Mechanical Engineering Studies, College of Engineering, Universiti Teknologi MARA, Cawangan Pulau Pinang, Kampus Permatang Pauh, Permatang Pauh, Penang, Malaysia
4School of Mechanical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Seberang Perai Selatan, Penang, Malaysia
*Email Address : iqbal.a@umk.edu.my
Abstract : In LED encapsulation, the formation of microvoids within the protective layer poses a significant threat to optical performance, long-term reliability, and luminous efficiency. This technical analysis aims to investigate the critical relationship between the dispenser needle height during the epoxy encapsulation process and the prevalence of these detrimental microvoids by using computational fluid dynamics (CFD) numerical simulation, supported by experimental research. The results showed that the occurrence of microvoids within the epoxy resins is quantified at the LED walls (sharp edges), and additional microvoids appeared on the top of the LED chip. Through varying the dispenser height, it is experimentally found that the volume of fluid (VOF), velocity, diaphragm pressure, and time taken to complete an LED encapsulation increase monotonically with increasing epoxy dispenser height, while microvoid formation shows an opposite trend. This effect can be explained by the fact that the lower dispenser generates a high velocity and turbulent impact of the epoxy encapsulant fluid onto the LED chip. This turbulence folds ambient air into the material, creating trapped microvoids. In contrast, increasing the dispenser height reduces the epoxy fluid’s kinetic energy upon contact and promotes a transition to a gentler regime. The gentler flow front fills the LED chip in a controlled, effectively evacuating air ahead of it rather than entraining it. Therefore, optimizing dispenser height is established as a fundamental and effective control parameter in LED encapsulation. This research directly addresses the root cause of microvoids formation by mitigating initial turbulence, thereby enabling the production of high-quality, optical transparent, and reliable LED encapsulant essential for superior performance and lifespan.
Keywords : LED packaging, encapsulation, epoxy resin, computational fluid dynamics (CFD), micro voids