【作者】 向建化；

【导师】 叶邦彦； 汤勇；

【作者基本信息】 华南理工大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 大功率LED作为新型固态照明光源与传统光源相比具有节能、环保和长寿命等优势,随着LED光源向小型化、大功率化方向发展,金属实体封装热沉存在较大的扩散热阻难以满足其散热需求,散热问题已成为大功率LED应用亟需解决的难题。本文提出了一种基于相变传热原理的大功率LED封装级散热器件—微小型相变热沉,对其制造工艺进行了分析,将强化沸腾结构应用于蒸发面以提高沸腾效率,制造了相变热沉并对其进行了性能测试,结果表明相变热沉具有较快的热响应特性和良好的传热性能。论文主要研究内容如下:(1)相变热沉系统理论分析及结构设计提出了基于相变热沉的大功率LED封装结构,相变热沉由本体、端盖、吸液芯和工质组成,分析了其传热原理;建立了变截面实体金属热沉和相变热沉的热阻模型,对实体铜质热沉和相变热沉热阻进行了理论分析,实体铜质金属热沉扩散热阻大于相变热沉热阻,影响相变热沉热阻的最大因素为蒸发端表面的强化沸腾效率;考虑了热沉材料、密封结构、工质和吸液芯、灌注和抽真空等因素对相变热沉各参数进行了设计。(2)相变热沉蒸发端强化沸腾结构成形方法在分析管外和平面沸腾结构成形工艺基础上,提出了相变热沉蒸发端面三维沸腾结构加工方法,采用犁切-挤压成形方法加工周向螺旋状微沟槽,建立了犁切-挤压速度和周向螺旋状微沟槽成形时间与进给量之间的关系模型并进行了分析;采用冲压成形方法加工放射状径向微沟槽,建立了干涉长度和进给角度、冲压深度以及刀具夹角之间的关系模型并进行了分析,最终形成的三维微沟槽强化沸腾结构在蒸发端平面内实现径向和周向之间的相互连通。(3)蒸发端面强化沸腾结构成形数值模拟分析在分析大变形刚塑性有限元模拟基本理论的基础上,以DEFORM-3D软件为平台分别建立了周向犁切-挤压和径向冲压成形的三维有限元模型,研究了周向和径向微沟槽成形时不同加工参数对沟槽塑性变形、应力分布和切削力的影响规律。数值模拟分析结果表明,犁切挤压深度和进给量影响周向微沟槽成形,并与冲压深度和进给角度参数共同影响最终三维微沟槽结构成形,沟槽塑性变形模拟结果与实验结果一致。(4)大功率LED微小型相变热沉制造分析了微小型相变热沉制造工艺,研究了蒸发端三维沸腾结构成形机理并进行了优化,得到了最优三维沸腾结构加工参数;研究了铜粉烧结温度和烧结时间对吸液芯孔隙率和脱模难易程度的影响,确定了最佳烧结温度和烧结时间参数;同时对灌注抽真空密封焊接各参数进行了分析,最后制造出了大功率LED微小型相变热沉。(5)相变热沉性能测试与分析通过热响应红外测试,分析了相变热沉和实体金属热沉在相同热输入条件下的热响应速度和温度分布,相变热沉热响应快的面积远大于铜质实体金属热沉热响应快的面积;通过传热性能实验,测试了不同热载荷、不同工质以及不同偏转角度条件下对相变热沉的性能的影响,结果表明,相变热沉具有良好的传热性能,在环境温度为20℃时,相变热沉适合功率为10W以下的LED封装散热,而实体金属热沉仅适合3W以下的LED封装散热。更多还原

【Abstract】 High power Light Emitting Diode (LED) is a new type of solid-state light source. There are a number of advantages compared to traditional light sources such as energy conservation, environmental friendly and long life time etc. With the development of LED light source to miniaturization and high power, traditional solid heat sink is difficult to meet cooling demand of high power LED due to spreading resistance, so thermal management has become one of the challenges for application of high power LED. In this paper, a kind of miniaturized phase change heat sink based on principle of phase change heat transfer is designed for high power LED packaging and its manufacturing technique is analysized. Boiling enhancement structures is formed in evaporation surface to improve boiling efficiency and it is proved that phase change heat sink possessed faster heat response performance and higher heat transfer performance than that of traditional solid heat sink by heat transfer testing. The research in the paper is mainly as follows:(1) Theory analysis and design of phase change heat sinkHigh power LED packaging structure based on phase change heat sink, which makes up of main body, end-cover, wick and refrigerant, is designed and its heat transfer principle is analysized. Thermal resistance model of solid and phase change heat sink with variable section are established respectively. It is found that spreading resistance of solid heat sink is greater than that of phase change heat sink and the most important factor to impact thermal resistance of phase change heat sink is boiling efficiency of evaporation surface by the theoretical analysis. Considering the materials, sealing method, refrigerant, wick, perfusion and vacuum, structure parameters of phase change heat sink are designed.(2) Forming method of boiling enhancement structures in evaporation surfaceBased on analysis of forming technology for boiling structure of outside tube and plane, forming method of 3D boiling enhancement structures in evaporation surface of phase change heat sink is designed. Spiral groove is processed by ploughing-extrusion (P-E) method, meanwhile, relationship between P-E speed, processing time and feed is analysized. Radial groove is formed by stamping method based on spiral grooves to obtain 3D enhancement structures which interconnect the radial and circumferential grooves in evaporation surface. Relationship among interferential length, feed angle, stamping depth and angle of stamping tool is analysized. (3) Finite numerical simulation of boiling enhancement structures forming3D finite element model of spiral P-E and radial stamping are established based on the analysis of theory of large rigid plastic deformation by the DEFORM-3D software. Groove plastic deformation, distribution rule of stress and force in the spiral and radial grooves process under different parameters are simulated. The results show that the spiral grooves are influenced by P-E depth and feed, and 3D boiling structures are affected by P-E depth, feed, stamping depth and feed angle together. Simulation results of groove are consistent with the experimental results.(4) Manufacturing of miniaturized phase change heat sink for high power LEDManufacturing technology of miniaturized phase change heat sink is analysized. Formation mechanism of 3D enhancement structure is researched and the processing parameters are optimized. Relationships of sintering temperature, sintering time of copper wick and porosity and withdrawing state are studied. The optimized parameters of sintering temperature and time are determined. At the same time, processing parameters of refrigerant injection, vacuum-pumping and welding, are investigated. Finnaly, miniaturized phase-change heat sinks for high power LED are obtained.(5) Performance testing and analysis of phase change heat sinkHeat response performance and temperature distribution are observed by the infrared test. It is found that the area of higher temperature of phase change heat sink is far larger than that of solid heat sink in the equivalent heating time. Heat transfer performances under different input power, refrigerants and inclination of phase change heat sink are tested. The results show that phase change heat sink is suitable for less than 10W LED heat dissipation and solid heat sink is only suitable for less than 3W.更多还原