COB封装的LED的热应力与应变的模拟仿真与分析
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摘要
将COMSOL焦耳热模块和结构力学模块耦合,仿真计算了板上芯片封装(COB)情况下,LED芯片、硅胶、固晶胶、衬底的热应力(应变)分别随反射杯结构参数、固晶胶厚度、固晶胶热导率、衬底厚度、衬底热导率和芯片功率的变化情况,结果表明:LED内最大应力出现在透镜与基板的连接处,其次,在芯片固晶胶与基板之间;反射杯的深度对硅胶热应力、应变影响较小;芯片、固晶胶的热应力和z方向形变量均随芯片功率的增加而逐渐增加。结合结温和热应力综合考虑,建议固晶胶厚度约40 μm;若能解决硅与GaN材料晶格匹配的问题,可选用厚度100 μm以下的硅作为衬底。
The effects of the structure parameters of reflector cup,adhesive thickness,thermal conductivity of adhesive,substrate thickness,thermal conductivity of substrate and power of chip on the thermal stress( strain) of LED chip,silica gel,adhesive and substrate are simulated and calculated by coupling the COMSOL Joule thermal module with structural mechanics module. The results show that the maximum stress in the LED occurs at the junction between the lens and the substrate,then,between the chip adhesive glue and the substrate. The depth of the reflecting cup has little effect on the thermal stress and strain of the silica gel.The thermal stress and Z-direction deformation of the chip and the adhesive glue increase gradually with the increase of the chip power. After comprehensive consideration of both junction temperature and thermal stress,the thickness of the adhesive glue is suggested to be about 40μm,and if the lattice matching problem between silicon and GaN materials can be solved,the silicon with thickness less than 100μm can be selected as the substrate.
The effects of the structure parameters of reflector cup,adhesive thickness,thermal conductivity of adhesive,substrate thickness,thermal conductivity of substrate and power of chip on the thermal stress( strain) of LED chip,silica gel,adhesive and substrate are simulated and calculated by coupling the COMSOL Joule thermal module with structural mechanics module. The results show that the maximum stress in the LED occurs at the junction between the lens and the substrate,then,between the chip adhesive glue and the substrate. The depth of the reflecting cup has little effect on the thermal stress and strain of the silica gel.The thermal stress and Z-direction deformation of the chip and the adhesive glue increase gradually with the increase of the chip power. After comprehensive consideration of both junction temperature and thermal stress,the thickness of the adhesive glue is suggested to be about 40μm,and if the lattice matching problem between silicon and GaN materials can be solved,the silicon with thickness less than 100μm can be selected as the substrate.
引文
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[2]KRAMES MR,SHCHEKIN OB,MUELLER-MACH R,et al.Status and future of high-power light-emitting diodes for solid-state lighting[J].J.Disp.Technol.,2007,3(2):160-175
[3]ARIK M,WEAVER S.Chip scale thermalmanagement of high brightness LEDpackages[C].Proc.of SPIE,2004,5530:214-223.
[4]ZHMAKINA I.Enhancement of light extraction from lightemitting diodes[J],Phys.Rep.,2011,498(4-5):189-241.
[5]龙兴明.InGaN/Ga N发光二极管的数学物理模型和特性及最优驱动电流研究[D].重庆:重庆大学,2012.
[6]LONG X,LIAO R,ZHOU J,Numerical simulation on electrical-thermal properties of Ga N-based light-emitting diodes embedded in board[J].Advances in Opto-Electronics,2012,2012:495981
[7]LONG X,LIAO R,ZHOU J,Development of streetlighting system-based novel high-brightness LED modules[J].IETOptoelectron.,2009,3(1):40-46
[8]LONG X,LIAO R,ZHOU J,et al.Multiple-chip package embedded on compound board for light emitting diode[J].Electron.Lett.,2011,47(20):28-31.
[9]HU J Z,YANG L Q,HWANG W J,et al.Thermal and mechanical analysis of delamination in Ga N-basedlight-emitting diode packages[J].J.Cryst.Growth,2006,288(1):157-161.
[10]于新刚,梁新刚.功率型发光二极管芯片的温度场与应力场[J].清华大学学报:自然科学版,2007,47(8):1380-1383.
[11]戴炜锋,王珺,李越生.大功率LED封装的温度场和热应力分布的分析[J].半导体光电,2008,29(3):324-328.
[12]刘一兵.功率型LED封装基板材料的温度场和热应力分析[J].半导体光电,2011,32(5):646-649.
[13]周庆,潘开林,黄静,等.大功率LED硅胶透镜热分析[A].第八届中国国际半导体照明论坛(大会/技术分会)论文集,2011:259-262
[14]朱旭平,余桂英,丁纾姝,等.功率型LED瞬态温度场及热应力分布的研究[J].光电工程,2011,38(2):132-137
[15]连兴峰,苏继龙,封装热效应及粘结层对微芯片应力和应变的影响[J].机电技术,2012,35:33-36.
[16]兰海,邓种华,刘著光,等.LED的COB封装热仿真设计[J].光学学报,2012,33(5):535-549.
[17]TAN JT,ZHANG SF,QIAN MC,et al.Effect of graphene/Zn O hybrid transparent electrode on characteristics of Ga Nlight-emitting diodes[J].Chin.Phys.B,2018,27(11):114401-1~7
[18]QIAN MC,ZHANG SF,LUO HJ,et al.Simulation on effect of metal/graphene hybrid transparent electrode on characteristics of Ga N light emitting diodes[J].Chin.Phys.B,2017,26(10):104402
[19]YAN QX.,ZHANG SF.,LONG XM.,etal.Numerical simulation on thermal-electrical characteristics and electrode patterns of Ga N-LEDs with graphene/Ni Ox hybrid electrode[J].Chin.Phys.Lett.2016,33(7):078501,
[20]XUE SJ,FANG L,LONGXM,et al.Influence of ITO,graphene thickness and electrodes buried depth on led thermal-electrical characteristics using numerical simulation[J].Chin.Phys.Lett.2014,31(2):028501
[21]李明,黄庆安,宋竞,等.COB封装中热-机械耦合效应的研究[J].传感技术学报,2006(5):1606-1609.