【作者】 苏达；

【导师】 王德苗；

【作者基本信息】 浙江大学 ， 物理电子学， 2008， 硕士

【摘要】 LED以其体积小,全固态,长寿命,环保,省电等一系列优点,已经在汽车照明、装饰照明、手机闪光灯、大中尺寸（NB、LCD-TV等）显示屏光源模块得到广泛应用,成为21世纪最具发展前景的高技术领域之一。美国、欧盟、日本等众多国家纷纷出台计划,投入巨资加速其发展,以占领能源战略制高点。现有LED的电光转换效率约为20%～30%,而70%～80%的能量转化为无法借助辐射释放的热能。如果封装散热不良,会使芯片温度升高,引起应力分布不均、芯片发光效率降低、荧光粉转换效率下降。当温度超过一定值,器件的失效率将呈指数规律攀升。因此,大功率LED封装的散热难题是当前产业化的瓶颈技术之一,大功率白光LED封装的散热性能更是国内外的研究热点。本文针对目前国内外封装存在的问题,首先提出了一种新的大功率LED封装结构,然后对该结构及其材料进行了理论、实验分析和工艺研究,再对采用该结构的5W单芯片白光LED封装和5W多芯片白光LED阵列封装进行了仿真优化设计,最后设计并制备了热阻为8.05K/W的5W单芯片白光LED封装。论文取得的成果及创新点主要有:（1）针对目前大功率LED封装结构普遍存在散热性能不良,制备工艺复杂,成本高等缺点,通过理论分析和实验研究,我们提出了一种高功率LED兼容集成封装模块和一种自散热式发光二极管日光灯,并已申请相关专利两项。通过将绝缘层和电极层以薄膜形式直接制备在铝基板上,减少了大功率LED封装的内部热沉数量、减薄内部热沉厚度。不仅提高了大功率LED封装的散热性能,而且制备工艺简单、成本低、无污染,符合RollS标准,为解决大功率LED封装的散热难题提供了一种新的结构。（2）通过理论分析和比较组成散热基板、绝缘层和电极层的各种材料性能,设计并选用铝作为基板材料、氧化铝作为绝缘层材料、过渡层（Ti）/阻挡层（Ni-Cu）/电极层（Ag）的梯度膜系和ITO薄膜两种作为电极层的结构。（3）采用ANSYS软件对5W单芯片白光LED封装和5W多芯片白光LED阵列封装进行三维热力学仿真优化设计,研究发现5W单芯片白光LED封装的热阻为5.8K/W,当环境温度为50℃时,芯片最高的结温为73.197℃,可以满足大功率LED封装的散热要求;5W多芯片白光LED阵列封装的热阻为3.986K/W,当环境温度为50℃时,芯片最高的结温为65.994℃,可以满足大功率LED封装的散热要求;优化结构参数后采用厚度为1.1 mm的铝基板,空气对流系数为10W/（m²·K）时,5W多芯片白光LED阵列封装的热阻为2.563 K/W。该封装结构无论是应用于单芯片还是多芯片阵列封装,都可以满足LED的散热要求。（4）采用硬质硫酸阳极氧化法制备了厚度为30.2um,介电强度为32.5V/um氧化铝绝缘层,通过理论研究和测试分析了绝缘层镀膜后短路的机理并指出了改进方法。（5）研究了电极层的材料和制备工艺,采用直流磁控溅射法制备出Ti（150nm）/Ni-Cu（400nm）/Ag（200nm）组成的梯度膜系作为电极层,其电阻率为3×10^-6Ω·cm,平均抗拉强度为4.22MPa,膜层表面缺陷较少,致密性好,焊接性能好,满足电极层的需求。（6）提出了在氧化铝绝缘层上采用射频磁控直流溅射法制备ITO薄膜作为电极层的过程中引入紫外在线辐照来降低ITO薄膜电阻率的新工艺,并申请了相关专利一项。实验表明在紫外辐照条件下制备的样品的电阻率、表面形貌和生长取向明显优于未经紫外辐照的样品,在线紫外辐照下最低方阻为5Ω/□,电阻率为2.5×10^-4Ω·cm,平均抗拉强度为5.3MPa,表面缺陷少,致密度好,趋于[222]的择优取向,焊接性能好,基本满足电极层的需求。（7）在上述研究的基础上,我们初步制备出了散热性能良好的5W白光LED单芯片封装,初测其封装热阻为8.05K/W,与第四章中的5W白光LED单芯片封装的热阻仿真结果5.8K/W比较吻合。当环境温度为50℃时,芯片最高的结温为82.2℃,可以满足大功率LED封装的散热要求。更多还原

【Abstract】 Light emitting diode（LED）,being widely used in mobile flashlight,large and medium sizes displays（NB,LCD-TV） and illumination system,has become one of the most promising high technologies in 21st century with a series of distinctive advantages such as lower-power consumption,pure light,solid-state,environmental protection.Many countries such as the United States,the European Union,Japan and China have established national strategies and invested to accelerate LED industry.The eletrophotic conversion efficiency ranges from 20%to 30%,thus the rest energy converts into thermopower which can’t be released through radiation.With this low heat removal efficiency,the raise of temperature in the chip will result in non-uniform distribution of thermal stress,decline of the luminous efficiency of the chip and the maser efficiency of the phosphor,and ultimately lead to device failure. So the packaging of high-power LEDs,especially the packaging of white high-power LEDs has been the obstacles to the industrilization.To solve the problems of the current packaging of high-power LEDs,we put forward a new structure of packaging of high-power LEDs.Through research both theoretically and experimentally as well as processing on the structure and materials of packaging for high-power LEDs and the simulation and optimal design of 5W single-chip white LED packaging and 5W multi-chip white LEDs packaging,we designed and prepared a thermal packaging module for 5W white LEDs with the thermal resistance of 8.05K/W and the luminous efficiency of 1601m/W.The major works and innovation in this paper are as follows:（1） To solve the common problems about the present packaging of high-power LEDs with worse thermal performance,complicate process and high cost,we presented an integrated packaging of high-power LEDs and a packaging of fluorescent lamp composed of LEDs on the basis of both theory and experiment,and applied for two relevant patents.By preparing the insulating layer and the electrode layer directly on the aluminum plate,the amount and thickness of internal heat sinks about the packaging of high-power LEDs is reduced.Thus,these methods,which could improve the thermal performance of packaging for high-power LEDs with easy processing,lost cost and environmental protection according to RollS,could lead to a effective solution to the heat-release problem for packaging of high-power LEDs.（2） Through theoretical analysis and comparison about performance among the materials used for the cooling plate,the insulator layer and the electrode layer,we chose the aluminum for cooling plate,Al₂O₃ for insulator layer and Cr/Ni-Cu/Ag or ITO layer for the electrode layer.（3） With the simulation and optimal design of thermodynamics for packaging modules of 5W single-chip white LED and 5W multi-chip white LEDs,we found that the thermal resistance of the first packaging is 5.8K/W and This packaging,of which the highest temperature of the chip is 73.197℃when the ambient temperature is 50℃,could well satisfy heat-release needs for the high-power LED packaging.And the second packaging,of which the thermal resistance is 3.986K/W and the highest temperature of the chip is 65.994℃when the ambient temperature is 50℃,could well satisfy heat-release needs for the high-power LED packaging.The thermal resistance of the second one is 2.563K/W with aluminum plate 1.1 mm thick and the convection coefficient of 10 W/（m²·K） after the optimal of structure parameters. The packaging both for single-chip and multi-chips could meet the heat-release requirement for high-power LEDs.（4）We prepared the aluminum dioxide layer with the thickness of 30.2urn and the dielectric probability of 32.5V/um by the method of hard acid anodizing.Through theoretical analysis and test,we analyzed the explanation for non-insulation about the insulator layer after coating and pointed out some improvements.（5） After the research about the preparation and materials of the electrode layer, we produced each layer of it as Cr/Ni-Cu/Ag.The results shown that the sample of which the resistivity achieved 3×10^-6Ω·cm,average bonding force up to 4.22 MPa with little surface defaults and good density and fine welding probability could meet the acquirement of the electrode layer.（6） We presented a new method with the introduction of online ultraviolet radiation during the preparation of ITO thin-film as electrode layer by RF magnetron sputtering and applied for a relevant patent.These results shown that the resistivity, the surface topography and the growth orientation of samples produced with UV radiation are much better than samples produced without UV radiation.The sample produced with UV radiation of which the smallest square resistance is 5Ω/□,the resistivity achieved 2.5×10^-4Ω·cm,average bonding force up to 5.3 MPa with little surface defaults and good density and the peak of[222]and good welding probability could meet the acquirement of the electrode layer.（7）Based on the study above,we prepared a packaging of 5W single-chip white LED with thermal resistance of 8.05K/W.This result is highly consistent with the predictions of the theoretical model.This packaging,of which the highest temperature of the chip is 82.2℃when the ambient temperature is 50℃,could well satisfy heat-release needs for the high-power LED packaging.更多还原