本文選題：LED　切入點(diǎn)：熱阻　出處：《江蘇大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：隨著電子技術(shù)的飛速發(fā)展,電子器件趨向于高度集成化和微尺度化。微系統(tǒng)中保證器件互連的界面結(jié)構(gòu)越來(lái)越多,能量在傳輸?shù)倪^(guò)程中勢(shì)必會(huì)部分消耗于界面處。由此,熱設(shè)計(jì)必然會(huì)成為電子器件中一項(xiàng)非常重要的工作。在節(jié)能減排的浪潮下,LED憑借節(jié)能、環(huán)保、無(wú)污染等優(yōu)點(diǎn)作為一顆新星引領(lǐng)照明行業(yè)的發(fā)展。目前LED的光電轉(zhuǎn)換效率僅為20%-30%,其70%-80%的能量以熱能的形式存在,這嚴(yán)重阻礙著LED的廣泛應(yīng)用,因此LED熱可靠性問(wèn)題成為亟待解決的難題。納米技術(shù)的發(fā)展促進(jìn)新材料技術(shù)的進(jìn)步,其中低維納米結(jié)構(gòu)的石墨烯材料憑借其在熱學(xué)、力學(xué)、光學(xué)和電學(xué)等方面優(yōu)異的特性被引起極大的關(guān)注。在熱學(xué)方面,通過(guò)對(duì)石墨烯納米帶和石墨烯復(fù)合材料進(jìn)行理論研究和數(shù)值模擬,加深對(duì)其熱傳導(dǎo)物理機(jī)制的理解,使其在電子器件中的應(yīng)用成為可能。本文以LED為研究對(duì)象,針對(duì)其散熱可靠性問(wèn)題,首先采用宏觀過(guò)程的理論計(jì)算和實(shí)驗(yàn)手段分析LED系統(tǒng)的熱傳輸特性,然后在微納尺度下利用非平衡態(tài)分子動(dòng)力學(xué)方法來(lái)探尋適合于LED的高導(dǎo)熱界面散熱材料,最后進(jìn)行LED燈具的MD/FE多尺度模型計(jì)算。本論文所做的主要工作和取得的研究成果如下：1.基于系統(tǒng)結(jié)構(gòu)建立功率型LED傳熱數(shù)學(xué)模型,搭建LED熱瞬態(tài)測(cè)試系統(tǒng),理論計(jì)算和實(shí)驗(yàn)測(cè)試LED在冷板不同位置處的傳熱特性。利用Flotherm熱分析軟件建立LED理論數(shù)學(xué)模型,研究冷板上不同位置的LED溫度分布,分析結(jié)溫和基板厚度之間的關(guān)系；搭建LED熱瞬態(tài)測(cè)試系統(tǒng),抽取積分結(jié)構(gòu)函數(shù)和微分結(jié)構(gòu)函數(shù),測(cè)試得到A、B、C和D不同位置的總熱阻分別為26.19K/W、26.45K/W、26.94K/W和27.06K/W。通過(guò)對(duì)數(shù)值仿真結(jié)果和實(shí)驗(yàn)結(jié)果進(jìn)行對(duì)比,揭示熱量傳輸通道上界面處導(dǎo)熱材料的熱影響作用,這為尋求高導(dǎo)熱界面材料或新型界面結(jié)構(gòu)提供理論依據(jù)。2.構(gòu)建缺陷型石墨烯納米帶的熱學(xué)理論傳輸模型,計(jì)算不同條件和不同狀態(tài)下熱導(dǎo)率值,計(jì)算并繪制石墨烯納米帶的局部位置聲子譜,分析熱傳輸機(jī)制,為L(zhǎng)ED器件高效傳熱界面結(jié)構(gòu)設(shè)計(jì)制造尋找新型材料基礎(chǔ)。利用Material Studio軟件構(gòu)建缺陷型石墨烯納米帶的數(shù)學(xué)理論模型,采用LAMMPS軟件進(jìn)行分子動(dòng)力學(xué)計(jì)算模擬。利用非平衡態(tài)分子動(dòng)力學(xué)方法研究水平方向和垂直方向上缺陷位置對(duì)單層石墨烯納米帶的熱傳輸影響。當(dāng)垂直距離為1.065nm時(shí),在水平方向上缺陷位置由左向右移動(dòng)的過(guò)程中,熱導(dǎo)率下降到最小值73.17W/mK后,逐漸增加到80.09W/mK;同時(shí)分析五種不同垂直距離的情況,研究發(fā)現(xiàn)定性依賴關(guān)系為先減小再增大,呈浴盆曲線變化趨勢(shì)。當(dāng)水平距離為4.059nm時(shí),在垂直方向上缺陷位置由下向上移動(dòng)的過(guò)程中,熱導(dǎo)率呈現(xiàn)先增加再減小的周期性變化趨勢(shì)。計(jì)算并繪制不同位置的聲子譜,通過(guò)聲子匹配度分析認(rèn)為水平方向上缺陷位置在溫度較低的邊界處聲子不能穿過(guò)缺陷,溫度和聲子頻率增加,高頻聲子發(fā)生隧道效應(yīng)。缺陷在垂直方向上對(duì)熱導(dǎo)率的影響小于水平方向上的影響,同時(shí)垂直方向上表現(xiàn)出周期性變化趨勢(shì),分析認(rèn)為這主要與石墨烯納米帶的手征鋸齒特性相關(guān)。3.構(gòu)建石墨烯／硅界面異質(zhì)熱傳輸理論模型,研究溫度、尺寸和摻雜對(duì)石墨烯異質(zhì)結(jié)構(gòu)的傳熱特性的影響,為L(zhǎng)ED器件高效傳熱界面結(jié)構(gòu)設(shè)計(jì)制造尋找新型熱傳輸模式及匹配法則。利用Material Studio軟件構(gòu)建石墨烯／硅異質(zhì)界面理論模型,采用分子動(dòng)力學(xué)方法來(lái)研究石墨烯／硅界面的熱傳輸特性。研究發(fā)現(xiàn)在溫度處于300K-800K時(shí),理想異質(zhì)結(jié)構(gòu)的熱導(dǎo)率整體呈現(xiàn)下降趨勢(shì),但在300K～500K時(shí),此時(shí)的熱導(dǎo)率卻呈現(xiàn)上升的趨勢(shì),即理想接觸界面熱導(dǎo)率呈現(xiàn)先緩慢上升再下降的趨勢(shì),具有一定的溫度依賴性。當(dāng)異質(zhì)結(jié)構(gòu)接觸面積缺陷為3%時(shí),此時(shí)的傳熱特性與理想異質(zhì)結(jié)構(gòu)相似。隨著接觸面積缺陷的增加,整體呈現(xiàn)下降趨勢(shì)。當(dāng)異質(zhì)結(jié)構(gòu)接觸面積缺陷達(dá)到35%時(shí),分析認(rèn)為溫度的上升使熱導(dǎo)率下降的主要原因是石墨烯聲子ZA模式和硅表面波的耦合。在尺寸方面,建立不同寬度的異質(zhì)結(jié)構(gòu)模型,在模擬尺寸范圍內(nèi)發(fā)現(xiàn)異質(zhì)結(jié)構(gòu)的熱導(dǎo)率遠(yuǎn)遠(yuǎn)小于單層或多層不同手型的石墨烯納米帶的熱導(dǎo)率值。當(dāng)異質(zhì)結(jié)構(gòu)寬度為2.71nm時(shí),異質(zhì)結(jié)構(gòu)表面熱導(dǎo)率隨尺寸增加而增大,呈現(xiàn)尺寸效應(yīng)。在100nm左右時(shí),影響趨勢(shì)變小,獲得理想異質(zhì)結(jié)構(gòu)熱導(dǎo)率指數(shù)函數(shù)關(guān)系。通過(guò)對(duì)不同缺陷比例的異質(zhì)結(jié)構(gòu)進(jìn)行邊緣硼和氮的摻雜,發(fā)現(xiàn)隨著缺陷比例的增大,使得摻雜后的異質(zhì)結(jié)構(gòu)熱導(dǎo)率呈現(xiàn)下降趨勢(shì),且硼原子的摻雜對(duì)異質(zhì)結(jié)構(gòu)傳熱特性的影響要明顯大于氮原子摻雜的影響,分析認(rèn)為原子質(zhì)量的不同造成一定程度的晶格振動(dòng)非簡(jiǎn)諧效應(yīng)。4.進(jìn)行LED關(guān)鍵界面結(jié)構(gòu)多尺度數(shù)學(xué)模型計(jì)算,模擬并對(duì)比分析三種不同界面材料時(shí)不同對(duì)流系數(shù)和輸入功率下LED的散熱特性；通過(guò)對(duì)LED燈具結(jié)構(gòu)進(jìn)行MD/FE多尺度模型計(jì)算,研究發(fā)現(xiàn)當(dāng)石墨烯結(jié)構(gòu)材料作為界面材料時(shí),LED燈具的穩(wěn)態(tài)溫度下降約8.4%。對(duì)流系數(shù)增加時(shí),石墨烯材料和錫合金焊料對(duì)燈具結(jié)溫的影響趨勢(shì)相似,而導(dǎo)電銀漿的作用遠(yuǎn)遠(yuǎn)小于兩者。同時(shí),功率的增加急劇降低LED產(chǎn)品的壽命。該研究成果為L(zhǎng)ED產(chǎn)品的結(jié)構(gòu)設(shè)計(jì)提供一種新型結(jié)構(gòu)。
[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.

【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN312.8

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