High-power LED Package Thermal Analysis

Light emitting diode (LED), because of its less pollution, high efficiency, small volume and many other advantages, is considered to be the most promising new light source in the21st century. It would replace incandescent lamp and fluorescent lamp as the mainstream of the lighting market and has huge market prospect. With the power density of LED chip becomes larger and larger in recent years, the chip will generate a large amount of heat, the heat assembles would lead to a series of negative consequences such as chip temperature rise, luminous efficiency reduce and so on, then shortens the normal working life of LED. Therefore, there is some practical significance to study heat dissipation study of the high power LED.The heat dissipation problems of the high power LED are mainly discussed in this paper. Some factors such as packaging structure, packaging materials, etc that can affect the dissipation performance of LED were analyzed and designed by finite element method. Firstly, this paper systematically introduces some basic knowledge of LED such as luminous principle, characteristic parameters. Then some basic theory of the heat transfer is introduced in this paper. We propose a thermal resistance model of LED, and calculate the thermal resistance of high power LED theoretically.High power LED packaging was analyzed by finite element method, and the steady-state temperature distribution was obtained. The results show that the temperature difference between plastic package and chip is a large, while the temperature difference between base plate and chip is much smaller. It can be seen that most of heat generated by chip passes into air through base plate. Then this paper analyzed the influence of the different encapsulation structure, packaging materials, cooling conditions on the heat dissipation performance of LED.Simulation analysis was carried out on the bar-tooth radiator, and thus the influence of different radiator material and size, etc factors on the heat dissipation performance of radiator was obtained. Results show that the more number, smaller interval and the higher height of fins, the better heat dissipation performance of radiator under the same conditions. Meanwhile, the thicker fins, the better heat dissipation performance, but the change of thickness of fins has little impact on the heat dissipation performance. In addition, the heat dissipation performance of pier-tooth radiator was analyzed. The results show that when the interval of fins is lower than a number, the heat dissipation performance of pier-tooth radiator is better than bar-tooth radiator’s.