流体对流下大功率LED散热性能研究

发布时间：2018-08-11 18:26

【摘要】：发光二极管(Light Emitting Diode,LED)具有节能、环保、体积小、寿命长、耐冲击、可靠性高、响应速度快等优点,被称为第四代新型绿色照明光源。随着LED在照明领域的应用发展,高功率、高亮度、高品质的LED已经成为重要的发展趋势。然而,目前LED的电光转换效率还较低,随着输入功率的增大,散热对LED器件的影响也越来越明显。结温的升高,导致发光波长发生偏移、光通量和使用寿命降低,所以LED的热管理对器件的整体性能起着至关重要作用,如何提高大功率LED器件的散热性能是其发展道路上亟待解决的关键技术之一。要获得高品质、高功率的LED,就必须理解LED热沉结构的散热原理,改进大功率LED封装结构。在大功率LED封装的散热设计上,最重要的是有效降低LED芯片的结温和热阻,通过设计合理的散热结构,增加器件的整体散热量。LED芯片的热量主要是先通过热传导传递到散热器,再通过热对流与外界环境进行交换,因为在固体与流体之间存在热边界层,所以如何减小边界层厚度,是增加LED散热性能的关键因素。因此,对大功率LED封装结构进行研究,有利于提高大功率LED器件整体散热性能,加快半导体照明时代的进程。文中采用理论分析与计算机仿真模拟分析相结合的方法,研究了热沉结构对LED散热性能的影响。其中,在自然对流条件下设计了新型散热结构,在液冷条件下,探究了不同结构热沉的散热机理。分析结果表明:(1)开缝基板能有效改善流场分布,提高表面换热系数,增加散热性能。在传导和对流的双重作用下,存在最佳缝间距使结温和热阻最低,输入功率为1 W时,结温和热阻分别降低3.2 K和1.01 K/W。随芯片输入功率的增加,开缝基板的散热效果愈发明显。同时,开缝基板的提出也节省了器件封装成本。(2)在开缝基板且散热体积相同的条件下,存在最佳翅片数量使LED散热性能最好,翅片数量为6时,结温最低,为345.970 K。(3)运用30°角矩形翅片的LED结温和器件热阻最低,换热性能最好,即速度场与温度场之间的协同性最好;菱形翅片次之,垂直平行翅片最差。30°角矩形翅片和菱形翅片由于倾斜角的存在,在增加换热性能的同时也增加了流动阻力,即速度与速度梯度之间的协同性变差;综合分析换热性能和流动阻力,菱形翅片的综合换热性能最好。封装散热结构的设计和散热原理的分析,对提高大功率LED散热性能具有极其重要的意义。研究大功率LED封装结构及其散热性能,对改进大功率LED封装具有一定的指导意义,为解决大功率LED的散热问题提供了新的途径。
[Abstract]:Light emitting diode (Light Emitting) has the advantages of energy saving, environmental protection, small size, long life, high impact resistance, high reliability and fast response, etc. It is called the fourth generation green lighting source. With the development of LED in the field of lighting, high power, high brightness, high quality LED has become an important development trend. However, the electro-optic conversion efficiency of LED is still low. With the increase of input power, the effect of heat dissipation on LED devices is becoming more and more obvious. The increase of junction temperature leads to the shift of luminous wavelength, the decrease of luminous flux and service life, so the thermal management of LED plays an important role in the overall performance of the device. How to improve the heat dissipation performance of high power LED devices is one of the key technologies to be solved. In order to obtain high quality and high power LED, it is necessary to understand the heat dissipation principle of LED heat sink structure and improve the high power LED package structure. In the heat dissipation design of high power LED packaging, the most important thing is to effectively reduce the junction and thermal resistance of LED chip. By designing a reasonable heat dissipation structure, the overall heat dissipation of the device can be increased. The heat of the chip is mainly transferred to the radiator by heat transfer. Because there is a thermal boundary layer between solid and fluid, how to reduce the thickness of boundary layer is the key factor to increase the heat dissipation performance of LED. Therefore, the research of high power LED packaging structure is helpful to improve the overall heat dissipation performance of high power LED devices and speed up the process of semiconductor lighting era. In this paper, the influence of heat sink structure on the heat dissipation performance of LED is studied by combining theoretical analysis with computer simulation analysis. Among them, a new heat dissipation structure was designed under natural convection, and the heat sink mechanism of different structures was explored under liquid cooling conditions. The results show that: (1) the slit substrate can effectively improve the flow field distribution, increase the surface heat transfer coefficient and increase the heat dissipation performance. Under the dual action of conduction and convection, the optimum gap spacing makes the thermal resistance of junction temperature minimum. When the input power is 1 W, the thermal resistance of junction and temperature decreases by 3.2 K and 1.01 K / W, respectively. With the increase of chip input power, the heat dissipation effect of slit substrate becomes more and more obvious. At the same time, the proposed slit substrate also saves the packaging cost of the device. (2) under the same heat dissipation volume of the slit substrate, the optimal number of fins makes the heat dissipation performance of LED the best, the number of fins is 6, and the junction temperature is the lowest. For 345.970 K. (3) the thermal resistance of LED junction and temperature field is the lowest, and the heat transfer performance is the best, that is, the synergy between velocity field and temperature field is the best, and the rhomboid fin is the second. The perpendicular parallel fin has the worst .30 掳angle rectangular fin and rhomboid fin, which increases the heat transfer performance and increases the flow resistance at the same time, that is, the synergy between velocity and velocity gradient becomes worse. Comprehensive analysis of heat transfer performance and flow resistance, the rhomboid fin comprehensive heat transfer performance is the best. The design of package heat dissipation structure and the analysis of heat dissipation principle are of great significance to improve the heat dissipation performance of high power LED. The research on the high power LED packaging structure and its heat dissipation performance has a certain guiding significance for improving the high power LED packaging, and provides a new way to solve the heat dissipation problem of the high power LED.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN312.8

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