Packaging Light Extraction Efficiency Enhancement Of LED Array Packaging With Various Micro-structures

Light-emitting Diode (LED) due to increasing luminous and other advantages such as energy efficiency as well as environmental friendly has more and more applications in daily lives. One LED module integrated with several or hundreds of high power LED chips is the developing trend of LED packaging. However, lower level packaging light extraction efficiency (PLEE) hinders broad application of LED array packaging. This paper presents a new method through which PLEE can be increased by adding micro-structures on top surface of packaging silicone.With the help of numerical simulation, this paper analyzes the efficacy and possibility of adding micro-structures on top surface of packaging silicone. After the analysis and simplification of actual problem, precise numerical model is built. Comparison between PLEE of LED array packaging with flat surface packaging silicone and that of LED array packaging with micro-structured surface LED array packaging is made. Within the paper, structural parameters of diameter, depth of seven kinds of micro-structures as well as the area ratio of flat surface on the packaging silicone are discussed in details. Simulation results show that micro-structures which can break TIR from two dimensions have better performances than those which can break TIR from one dimension. Among them, the inversed spherical cap structures demonstrate their abilities in enhancing the PLEE to 47.04% for conventional chips LED array and 36.07% for vertical thin film chips LED array. Inversed cone structures and inversed pyramid structures have similar ability in enhancing the PLEE. They can increase the conventional chips LED array to 44.71% and 45.26% and can enhance the vertical thin film chips LED array to 31.73% and 31.93% respectively. Moreover, adding flat surface within the micro-structures such as inversed rectangular frustum of prism and inversed frustum of cone can increase the PLEE to 45.77% and 46.18% for conventional chips LED array and 34.01% and 33.71% for vertical thin film chips LED array each.Based on the simulation result, the experiments of LED array packaging fabricated with micro-structures are conducted. The experiment results show that with the structural parameters presented by the paper, the inversed spherical cap structures, cylinder-grooves and V-grooves can increase the PLEE of conventional chips LED array to 12.13%,10.23%, and 7.44% respectively which coincides well with simulation results.