The Power LED Packaging Technique And Thermal Design

LED (light-emitting diode) is a new kind of green illuminating products which has some great advantages such as high efficiency, long lifetime and environmental friendliness. With the energy source crisis and environmental contamination, it would become the developing trend of illuminants. It can be foreseen that solid illuminants such as LEDs must be applied widely in 21st century. Developing with the light intensity and power, heat dissipation of chip became serious. Thermal problem is a key issue in high-power LED design, or it will great affect the output efficiency and lifetime of LED chip.LED Substrate is one of decisive components to solve the heat dissipation problem. It affects the electric-connecting, physical supporting, heat dissipating ability, the packaging process and the system cost, and then the reliability and stability of LED. In this dissertation, Aluminium substrate is researched as package materials to solve the heat dissipation for high power LED. Theory is analyzed and real production is produced.Nanometer Al2O3,SiC,SiO2 is used to enhance thermal conductivity by filling them in insulation layer. Different fillers are used, and their content effect on the properties of aluminium substrate are analyzied. The temperature distribution of substrate is analyzied by thermal infrared imager. The formula of filler is optimized after research. Results show when the filler content is from 100:35 to 100:45, LED aluminium substrate has good thermal conductivity. Mixed fillers has better thermal conductivity than one. When the proportion of resin, Al2O3, SiC and SiO2 is 100:30:5:5, LED aluminium substrate has best thermal conductivity. The thermal resistance can reach 0.65℃/W.ANSYS is used to analyze LED aluminium substrate. Results show that the thermal resistance is about linear with the thickness and conductivity of insulating layer respectively. The increase of conductivity and reduce of thickness of insulating layer are good ways to reduce thermal resistance and junction temperature. Six array LED chips have been packaged on the 6cm*6cm*1.5mm LED aluminium substrate. With the greater clearance of LED chips, the resistance it will become smaller firstly and then become larger. It has minimum resistance when the clearance is 20mm, and the heat is best distributed.According to theoretical study, a 6W LED packaging is designed and prepared. LED driver is designed with LNK306 to provide a constant current. After testing, the actual temperature of LED is 41.49℃which is very close to the simulated result 39.143℃.