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1.
陈照辉  刘勇  刘胜 《半导体学报》2011,32(2):024011-4
Wire bonding is one of the main processes of the LED packaging which provides electrical interconnection between the LED chip and lead frame. The gold wire bonding process has been widely used in LED packaging industry currently. However, due to the high cost of gold wire, copper wire bonding is a good substitute for the gold wire bonding which can lead to significant cost saving. In this paper, the copper and gold wire bonding processes on the high power LED chip are compared and analyzed with finite element simulation. This modeling work may provide guidelines for the parameter optimization of copper wire bonding process on the high power LED packaging.  相似文献   
2.
制备铝电解用NiFe2O4-10NiO基金属陶瓷惰性阳极,并在实验室电解槽中考察其电解腐蚀性能。结果表明,电解过程中虽然惰性阳极在960°C熔盐电解质中表现出优异的耐腐蚀性能,但采用XRD、SEM/EDX和金相分析其物相组成和微观结构后发现,电解后阳极中的金属相发生了优先腐蚀,在阳极表面产生大量孔洞。NiFe2O4相中的 Fe 元素的优先溶解可能导致 NiFe2O4晶粒的不均匀腐蚀。溶解在电解液中的 Al2O3与阳极中的 NiO 或FeO 发生反应生成的 NiFe2O4-NiAl2O4-FeAl2O4相对 NiO 相的吞并以及体积膨胀,阳极表面形成致密的NiFe2O4-NiAl2O4-FeAl2O4保护层。因此,致密的NiFe2O4-NiAl2O4-FeAl2O4保护层可以阻挡阳极表面金属相的损失和陶瓷相的腐蚀。  相似文献   
3.
采用均匀设计法研究了MgO-CaF2-Al2O3-SiO2碱性渣系烧结焊剂的焊缝成形;应用数理统计方法回归出了焊剂中各组分与焊缝成形的数学模型;获得了电熔镁、大理石、氟石、铝矾土、金红石与黏土的交互作用对焊缝成形的影响数据.试验结果表明:大理石与氟石共同作用对焊缝成形的影响为负相关;但大理石与铝矾土、金红石共同作用对焊缝成形的影响则为正相关.  相似文献   
4.
张芹  焦峰  陈照辉  徐玲  王思敏  刘胜 《半导体学报》2011,32(1):012002-3
In order to determine the environmental effects on the luminescence properties of a phosphor layer for high-power light emitting diodes, a high humidity and temperature test (85 ℃/85%RH) and a thermal aging test (85 ℃) were performed on silicone/YAG phosphor composites. The luminescence properties of silicone/phosphor composites are monitored by a fluorescence spectrometer. The results show that high temperature could result in an increase in conversion efficiency of composites during the early aging stage and red shift of YAG phosphor; and high humidity could result in a significant decrease in conversion efficiency of composites while having a small influence upon the optimal excitation wavelength of the YAG phosphor.  相似文献   
5.
A new type application specific light emitting diode(LED) package(ASLP) with freeform polycarbonate lens for street lighting is developed,whose manufacturing processes are compatible with a typical LED packaging process.The reliability test methods and failure criterions from different vendors are reviewed and compared.It is found that test methods and failure criterions are quite different.The rapid reliability assessment standards are urgently needed for the LED industry.85℃/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h,showing no visible degradation in optical performance for our modules,with two other vendors showing significant degradation.Some failure analysis methods such as C-SAM,Nano X-ray CT and optical microscope are used for LED packages.Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing.The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging.One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing.  相似文献   
6.
基于变分水平集的图像模糊聚类分割   总被引:4,自引:0,他引:4  
结合变分水平集方法和模糊聚类,提出了一个基于变分水平集的图像聚类分割模型.该模型引入了一个基于图像局部信息的外部模糊聚类能量和一个新的关于零水平集的正则化能量,使得该模型对噪声图像的聚类分割更具鲁棒性.通过在能量泛函中加入一个内部约束能量约束水平集函数为符号距离函数,可以使水平集演化过程无需重新初始化.进一步提出了一种变分形式的聚类中心更新方法,实现了半监督的图像聚类分割.实验中采用不同类型的图像与FCM聚类模型、CV模型、Samson模型进行了对比实验,实验结果显示,该模型能够克服图像中噪声的影响,取得较满意的聚类分割效果.  相似文献   
7.
以数学建模分析为基础的运筹学案例教学   总被引:1,自引:0,他引:1  
数学建模在"运筹学"课程教学内容中占有重要位置。"运筹学"课程可以数学建模分析为基础采用案例教学法,从而激发学生学习兴趣,增强学生的数学应用意识,培养学生的数学思维和建模能力。  相似文献   
8.
In order to determine the environmental effects on the luminescence properties of a phosphor layer for high-power light emitting diodes,a high humidity and temperature test(85℃/85%RH) and a thermal aging test (85℃) were performed on silicone/YAG phosphor composites.The luminescence properties of silicone/phosphor composites are monitored by a fluorescence spectrometer.The results show that high temperature could result in an increase in conversion efficiency of composites during the early aging stage and red shift of YAG phosphor;and high humidity could result in a significant decrease in conversion efficiency of composites while having a small influence upon the optimal excitation wavelength of the YAG phosphor.  相似文献   
9.
计算方法作为数学与应用数学专业的一门核心课程,在培养学生理论联系实际,应用科学计算方法解决工程问题中起着重要作用。基于此,分析该课程实践教学中存在的问题,从实践教学内容、教学方法和考核方式等各教学环节尝试进行一系列改革,有效提高应用型、创新性人才培养质量,努力实现应用型人才的培养目标。  相似文献   
10.
对讨论式教学方法的探讨   总被引:5,自引:0,他引:5  
讨论式教学是以启发式教学思想为基础,培养学生学习的主动性,提高学生的自主创新能力的一种教学方法.介绍了讨论式教学的课堂结构的三大要素:教师、学生和问题的设计,指出讨论式教学的课堂操作要营造宽松的讨论氛围、有效组织引导讨论和采取多样性的讨论方式.  相似文献   
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