LED关键界面结构热特性及可靠性研究

发布时间：2018-03-06 19:55

本文选题：LED　切入点：热阻　出处：《江苏大学》2015年博士论文　论文类型：学位论文

【摘要】：随着电子技术的飞速发展,电子器件趋向于高度集成化和微尺度化。微系统中保证器件互连的界面结构越来越多,能量在传输的过程中势必会部分消耗于界面处。由此,热设计必然会成为电子器件中一项非常重要的工作。在节能减排的浪潮下,LED凭借节能、环保、无污染等优点作为一颗新星引领照明行业的发展。目前LED的光电转换效率仅为20%-30%,其70%-80%的能量以热能的形式存在,这严重阻碍着LED的广泛应用,因此LED热可靠性问题成为亟待解决的难题。纳米技术的发展促进新材料技术的进步,其中低维纳米结构的石墨烯材料凭借其在热学、力学、光学和电学等方面优异的特性被引起极大的关注。在热学方面,通过对石墨烯纳米带和石墨烯复合材料进行理论研究和数值模拟,加深对其热传导物理机制的理解,使其在电子器件中的应用成为可能。本文以LED为研究对象,针对其散热可靠性问题,首先采用宏观过程的理论计算和实验手段分析LED系统的热传输特性,然后在微纳尺度下利用非平衡态分子动力学方法来探寻适合于LED的高导热界面散热材料,最后进行LED灯具的MD/FE多尺度模型计算。本论文所做的主要工作和取得的研究成果如下：1.基于系统结构建立功率型LED传热数学模型,搭建LED热瞬态测试系统,理论计算和实验测试LED在冷板不同位置处的传热特性。利用Flotherm热分析软件建立LED理论数学模型,研究冷板上不同位置的LED温度分布,分析结温和基板厚度之间的关系；搭建LED热瞬态测试系统,抽取积分结构函数和微分结构函数,测试得到A、B、C和D不同位置的总热阻分别为26.19K/W、26.45K/W、26.94K/W和27.06K/W。通过对数值仿真结果和实验结果进行对比,揭示热量传输通道上界面处导热材料的热影响作用,这为寻求高导热界面材料或新型界面结构提供理论依据。2.构建缺陷型石墨烯纳米带的热学理论传输模型,计算不同条件和不同状态下热导率值,计算并绘制石墨烯纳米带的局部位置声子谱,分析热传输机制,为LED器件高效传热界面结构设计制造寻找新型材料基础。利用Material Studio软件构建缺陷型石墨烯纳米带的数学理论模型,采用LAMMPS软件进行分子动力学计算模拟。利用非平衡态分子动力学方法研究水平方向和垂直方向上缺陷位置对单层石墨烯纳米带的热传输影响。当垂直距离为1.065nm时,在水平方向上缺陷位置由左向右移动的过程中,热导率下降到最小值73.17W/mK后,逐渐增加到80.09W/mK;同时分析五种不同垂直距离的情况,研究发现定性依赖关系为先减小再增大,呈浴盆曲线变化趋势。当水平距离为4.059nm时,在垂直方向上缺陷位置由下向上移动的过程中,热导率呈现先增加再减小的周期性变化趋势。计算并绘制不同位置的声子谱,通过声子匹配度分析认为水平方向上缺陷位置在温度较低的边界处声子不能穿过缺陷,温度和声子频率增加,高频声子发生隧道效应。缺陷在垂直方向上对热导率的影响小于水平方向上的影响,同时垂直方向上表现出周期性变化趋势,分析认为这主要与石墨烯纳米带的手征锯齿特性相关。3.构建石墨烯／硅界面异质热传输理论模型,研究温度、尺寸和掺杂对石墨烯异质结构的传热特性的影响,为LED器件高效传热界面结构设计制造寻找新型热传输模式及匹配法则。利用Material Studio软件构建石墨烯／硅异质界面理论模型,采用分子动力学方法来研究石墨烯／硅界面的热传输特性。研究发现在温度处于300K-800K时,理想异质结构的热导率整体呈现下降趋势,但在300K～500K时,此时的热导率却呈现上升的趋势,即理想接触界面热导率呈现先缓慢上升再下降的趋势,具有一定的温度依赖性。当异质结构接触面积缺陷为3%时,此时的传热特性与理想异质结构相似。随着接触面积缺陷的增加,整体呈现下降趋势。当异质结构接触面积缺陷达到35%时,分析认为温度的上升使热导率下降的主要原因是石墨烯声子ZA模式和硅表面波的耦合。在尺寸方面,建立不同宽度的异质结构模型,在模拟尺寸范围内发现异质结构的热导率远远小于单层或多层不同手型的石墨烯纳米带的热导率值。当异质结构宽度为2.71nm时,异质结构表面热导率随尺寸增加而增大,呈现尺寸效应。在100nm左右时,影响趋势变小,获得理想异质结构热导率指数函数关系。通过对不同缺陷比例的异质结构进行边缘硼和氮的掺杂,发现随着缺陷比例的增大,使得掺杂后的异质结构热导率呈现下降趋势,且硼原子的掺杂对异质结构传热特性的影响要明显大于氮原子掺杂的影响,分析认为原子质量的不同造成一定程度的晶格振动非简谐效应。4.进行LED关键界面结构多尺度数学模型计算,模拟并对比分析三种不同界面材料时不同对流系数和输入功率下LED的散热特性；通过对LED灯具结构进行MD/FE多尺度模型计算,研究发现当石墨烯结构材料作为界面材料时,LED灯具的稳态温度下降约8.4%。对流系数增加时,石墨烯材料和锡合金焊料对灯具结温的影响趋势相似,而导电银浆的作用远远小于两者。同时,功率的增加急剧降低LED产品的寿命。该研究成果为LED产品的结构设计提供一种新型结构。
[Abstract]:With the rapid development of electronic technology, electronic devices tend to be highly integrated and micro scale. The interface structure is more and more interconnected devices to ensure that micro systems, energy in the process of transmission will be partially consumed by the interface. Thus, the thermal design will become a very important work in such electronic devices. The wave of LED emission reduction, with energy saving, environmental protection, no pollution and other advantages as a new star to lead the development of the lighting industry. At present, the photoelectric conversion efficiency of LED is only 20%-30%, the 70%-80% of energy in the form of heat, which seriously hinder the wide application of LED, so the LED thermal reliability problem is an urgent problem the development of nanotechnology. The promotion of new materials and technology progress, the low dimensional nanostructures of graphene materials with its thermal, mechanical, optical and electrical aspects of excellent characteristics are great Attention in the Thermosciences area of theoretical research and numerical simulation based on the graphene and graphene composite materials, deepen their understanding of the physical mechanisms of heat conduction and its application in electronic devices possible. This paper takes LED as the research object, the reliability of the heat, heat transfer characteristics firstly, by theoretical calculation and experimental methods of macro analysis in the process of LED system, and then in the micro nano scale using nonequilibrium molecular dynamics method to explore the high heat thermal interface materials are suitable for LED, calculate the multiscale MD/FE model and finally the LED lamp. The main work of this paper are as follows 1.: Based on the mathematical model of heat transfer of power type LED system structure, build LED thermal transient testing system, the heat transfer characteristics of the theoretical calculation and experimental test of LED in different positions of cold plate by Flotherm. The establishment of mathematical software LED theoretical model of thermal analysis of LED cold plate temperature distribution in different positions, analysis to moderate the relationship between the thickness of the substrate; build LED thermal transient testing system, extraction and integral structure function and differential structure function test, A, B, C and D, the total thermal resistance in different positions were 26.19K/W. 26.45K/W, 26.94K/W and 27.06K/W. by comparing the results of numerical simulation and experimental results reveal the thermal effect at the interface of heat conducting material heat transmission, which provide the theoretical basis for the construction of.2. defective graphene nanoribbons theory of thermal transfer model for high thermal interface materials or new interface structure, calculation of different conditions and different under the condition of thermal conductivity, calculate and draw local phonon graphene nanoribbons spectrum, analysis of heat transfer mechanism, heat transfer device with high efficiency LED interface structure design and manufacture for new Material basis. To construct mathematical models defective graphene nanoribbons by using Material Studio software, molecular dynamics calculations were simulated by LAMMPS software. The heat transfer effect of defect location based on state level molecular dynamics method of non balanced direction and the vertical direction of the single-layer graphene nanoribbons. When the vertical distance is 1.065nm, the process of in the horizontal direction defects position from left to right, the thermal conductivity decreases to a minimum value after 73.17W/mK gradually increased to 80.09W/mK; at the same time, analysis of five different vertical distance, the study found that the qualitative dependence of first decrease and then increase, showed a trend of bathtub curve. When the horizontal distance is 4.059nm, in the vertical direction on the position of defect from the bottom to the process of moving, the thermal conductivity increases first and then decreased trend. Phonon is calculated and drawn in different positions By matching the phonon spectrum, the position of defect analysis that the horizontal direction through the defect in the lower temperature at the boundary temperature and phonons, phonon frequency increase, tunneling frequency phonon. Defects smaller than effects on thermal conductivity in the vertical direction in the horizontal direction and the vertical direction influence, showing periodic change the trend, analysts believe that this is mainly related to graphene nanoribbons chiral.3. sawtooth characteristics constructed graphene / silicon interfaces of heterogeneous heat transfer model, the effects of temperature, heat transfer effect of size and doping of graphene heterostructures, looking for new manufacturing heat transfer mode and matching rules for LED devices, the interface structure of heat transfer design. Construction of graphene / silicon interface theory model by using Material Studio software, the heat transfer characteristics of Shi Moxi / Si interface by molecular dynamics method. Study found that the temperature is 300K-800K, the ideal thermal conductivity heterostructure rate showed a downward trend, but in the 300K ~ 500K, the thermal conductivity is increasing, that is the ideal contact interface thermal conductivity showed the first slowly rising trend, has a certain temperature dependent. When the heterostructure contact area defects 3%, the heat transfer characteristics and ideal heterogeneous structure similar. With the increase of contact area of defects, decreased. When the area reached 35% contact heterostructure defects, analyses that the main reason of temperature rise to lower thermal conductivity of graphene is coupled ZA phonon mode and silicon surface. In size. Heterogeneous structure model is established with different width, found that thermal conductivity heterostructure rate is much smaller than single or multiple different hand type graphene nanoribbons with thermal conductivity in the simulated size range Value. When the heterogeneous structure width is 2.71nm, the surface conductivity heterostructure rate increase with the size increasing, showing the size effect. At about 100nm, the influence trend becomes small, obtain ideal heterostructure thermal conductivity exponential function. The edge of boron and nitrogen through the heterogeneous structure of different proportion defective doping with the increase the defect ratio, making heterostructure doped thermal conductivity rate decreased, and the effect of boron doping effect on the heat transfer characteristics of heterostructures is obviously higher than the doping of nitrogen atoms, atomic mass analysis of lattice vibration caused by different degree of anharmonicity.4. multi-scale mathematical model to calculate the interface structure of LED key. Simulation and comparative analysis of three kinds of different materials at different interface characteristics of heat convection coefficient and the input power of LED; through the LED lamp structure MD/FE multiscalc Calculation of the model, researchers found that when the graphene structure material as interface materials, decrease steady-state temperature of LED lamps increases about 8.4%. convection coefficient, influence of graphene materials and tin alloy solder on the lamp junction temperature tendency is similar, but the effect of conductive silver paste is far less than the two. At the same time, power increased dramatically reduced LED products life. The research results provide a new structure for the structure design of LED products.

【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN312.8

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