Thermal analysis of plastic heat sink for high power LED lamp

Recently, people are seeking lighting source which has higher efficiency and no pollution. Light Emitting Diode (LED) has become important illumination technology for many types of applications. It also has been used in many applications such as watches, indicator lights for many common household devices. LED brought the brightness. In addition, it´s eco-friendly to the environment. However, LED´s performance and lifetime depend on junction temperature. High power LED produces a great deal of heat. So it´s important to decrease the junction temperature of LED. In general, aluminum heat sink is used to reducing junction temperature of LED lamp. When surface area increases, junction temperature of LED will be lower. In order to obtain more surface area of heat sink, plastic heat sink can be considered. Because plastic heat sink can get complex geometric structure by molding. With enough surface area of heat sink and better surface finish, plastic heat sink can replace aluminum heat sink. It´s because the heat convection and radiation can remove the heat effectively. In this paper, the thermal analysis was carried out by numerical finite element simulation to investigate the thermal characteristics of LED lamp. Effect of heat sink´s material on junction temperature was compared for both aluminum and plastic heat sink. The aluminum heat sink can provide better thermal performance than the latter. In this study, a 7-Watt LED with plastic heat sink was performed. Then, the target temperature of 7-Watt LED with aluminum heat sink is about 74°C. Through numerical simulation observing variations in surface area and surface finish of plastic heat sink are determined to achieve the target temperature of 74°C. Results showed that plastic heat sink obtain 76.6°C by increasing emissivity and surface area of heat sink.