Thermal Analysis Of High-Power Led Packaging

LED is considered as a new green light source to take the place of traditional lighting, with a series of distinctive advantages such as energy saving, environmental protection, small volume, long service life, impact resistance, high reliability, fast response, an so on. With the application of LED in lighting area, LED of high-power, high brightness and high quality has become an important development trend. However, the electro-optical conversion efficiency of high-power LED is still low so far. With the increase of the input power, heat dissipation has become the biggest technical bottleneck to the popularization and development of LED lighting. The way to improve the heat dissipation performance of high-power LED device is one of the key technologies urgently needed to be solved on its development road.In order to achieve high quality and high-power LED, its packaging should be improved. For the thermal design of high-power LED packaging, the most important task is to effectively reduce the thermal resistance between chip luminous layer and the environment. By means of designing a reasonable heat dissipation channel, let the quantity of heat diffuses into the environment from the chip through the most effective channel. The proper selection of efficient packaging materials and encapsulation structures is an important link to effectively improve the reliability of high-power LED packaging. In addition, designing and using more suitable cooling structure and cooling way also can improve the reliability of high-power LED. Therefore, it is beneficial to promoting the advancement of high-power LED device’s overall performance and reliability, as well as accelerating the process of semiconductor lighting era, to carry on a research on the heat dissipation performance of high-power LED packaging.The influences on the device’s heat dissipation performance of various high-power LED packaging materials and packaging structures have been researched through the method of combining theoretical analysis and computer simulation analysis in this paper. The substrate materials, bonding materials and sealing materials are mainly discussed as the packaging materials, while a new packaging structure without aluminum substrate and the multichip COB packaging structure are mainly researched as the packaging structures. The simulation results show that:(1) For the chip whose input power is1W, it can meet the requirements of general device when the thermal conductivity of substrate is only20W/(m-K) and the thermal conductivity of bonding materials is about20-80W/(m-K). The optimum thickness of substrate is1.8mm, while decreasing the thickness of the bonding layer can lower the chip temperature of high-power LED to some extent, as well as reducing the cost of packaging.(2) The heat dissipation effect of the new structure without aluminum is obviously superior to that of traditional aluminum substrate structure. With the increase of input power, the advantage of the new structure is more remarkable. Combining the COB packaging technology and the eutectic welding process can effectively improve the thermal characteristics of high-power LED.Thus it can be seen that the reasonable combination of packaging materials and the optimization design of packaging structures help to improve the packaging of high power LED, which has great significances to improve the heat dissipation performance of high-power LED, and also provides a new way to solve the heat dissipation problem of high power LED.