Abstract
LED (lighting emitting diode, LED) has been widely used. Its array package specially has high commercial value and can allow various applications to liquid crystal display (LCD) backlight source, general lighting, and automobile instrument, etc.. However, the LED’s illumination performance and lifetime depend on the chip junction temperature distinctly. Thus, to control the thermal and extraction efficiency, the development of an effective thermal and optical analysis method on LED array package is extremely imperative. Based on the ANSYS® finite element analysis program, this work first establishes a rigorous three-dimensional finite element heat transfer model for the computation of temperature fired of the LED array package, concerning heat conduction, convection and radiation conditions. To get the accurate power of heat, an integrating sphere is adopted to measure the part of photon energy transformed from the input power. Also, this work uses the optical analysis program lighttool® to analyze the influence of nonuniform rays diffusing inside the package thermal and extraction efficiency. Under natural convection condition, this work uses the IR (infrared thermometer) to measure the temperature distribution on the surface of the LED array package. To obtain the correct surface emissivity of epoxy the difference with optical glass surface painted or not is investigated. The temperature of LED array package which has been measured and calibrated is also verified by thermal couple measurement by IR. In addition, to accurately obtain the chip junction temperature, the temperature sensitive parameter (TSP) curve of the LED array package is also established. To demonstrate the accuracy of the analysis model, computed results obtained from the above mentioned three-dimensional finite element heat transfer model are compared with various experimented results. After verifying the thermal and optical analysis model, this work finally choose a LED array package with better thermal dissipation for analysis. The response surface of lumen for different shapes of modeling component is developed. The best brightness and most uniform extraction of the specific surface is obtained by an optimization scheme. The methodology achieved can be effectively implemented for the best thermal and optical design of LED array package.