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Study on the Reliability of High-power LEDs under Temperature Cycle

Study on the Reliability of High-power LEDs under Temperatur...

2011 12th International Conference on Electronic Packaging Technology & High Density Packaging(2011 电子封装技术与高密度封装国际会议)

作者： Fan Huang Luqiao Yin Shuzhi Li Guangming Xu Huafeng Yan Yu Chen Jianhua Zhang Lianqiao Yang Key Laboratory of Advanced Display and System Applications (Shanghai University) School of Mechatron Key Laboratory of Advanced Display and System Applications (Shanghai University Shanghai Research Center of Eengineering and Technology for Semiconductor Lighting Shanghai Yaming Lighting co. Ltd.Ministry of Education.P.O.B 143 149 Yanchang Rd. Shanghai Univer Key Laboratory of Advanced Display and System Applications (Shanghai University) School of Mechatron

High-power LEDs have been widely used and have a big potential market due to the many advantages compared to conventional light sources. Reliability is one of the most important issues for the application of LEDs. In order to study the degradation mechanism and the stability of LED withstanding cyclical exposures to temperature variations, life test was carried out under temperature cycle testing. The experiment was designed basing on the EIAJ ED-4701/100. Four groups of 1 W high power LEDs adopting different material and structures were utilized. The temperature cycle accelerated life test under the condition of -25℃/125℃. After the accelerated test, the optical performance of the four kinds of devices were compared and analyzed, and the thermal performance of the LEDs was also tested, analyzed and discussed. At last, the reliability differences of high-power LEDs were analyzed and degradation mechanism of high power LEDs under temperature cycling was discussed.

关键词： Light emitting diodes Life estimation Reliability Thermal analysis Degradation Junctions Electronic packaging thermal management

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Study into High Temperature Reliability of Isotropic Conductive Adhesive

Study into High Temperature Reliability of Isotropic Conduct...

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2011 12th International Conference on Electronic Packaging Technology & High Density Packaging(2011 电子封装技术与高密度封装国际会议)

作者： Wenhui Du Huiwang Cui Si Chen Zhichao Yuan Lilei Ye Johan Liu Key Laboratory of Advanced Display and System Applications Ministry of Education and SMIT Center S Key Laboratory of Advanced Display and System Applications Ministry of Education and SMIT Center S Shangda Rui Hu Microsystem Integration Technology Co.Ltd Room 101 Science &Technology Building Sh Smart High Tech AB Fysikgrand 3 41296 Gothenburg SWEDEN Key Laboratory of Advanced Display and System Applications Ministry of Education and SMIT Center S

With the rapid development of technologies for high density assembly and packaging in electronic industry, isotropic conductive adhesive (ICA) has been paid more and more attention as a potential substitute for solder, due to its advantages of low processing temperature, simple processing conditions and good manufacturability. However, studies into the reliability of ICA are not as abundant as those of solder. As a composite material, the failure feasibility of ICA not only depends not only on the variation in performance of different constituent parts, such as high temperature aging of the polymer, aging due to moisture absorption and oxidization of filler particles, but also on interface changes. Thus, the failure mechanism of ICA seems to be complicated and studies into the reliability of ICA are also necessary. Reliability in humidity and heat has been investigated in previous works, and in this paper high temperature reliability will be studied as a comparison. Some reliability tests and results will be given and some failure mechanisms discussed. Finally, we present some discussion about the further optimization of reliability for follow-up studies.

关键词： Aging Reliability Conductivity Conductive adhesives Materials Packaging Temperature

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Effects of Die-attach Materials on the Optical Durability and Thermal Performances of HP-LED

Effects of Die-attach Materials on the Optical Durability an...

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2011 12th International Conference on Electronic Packaging Technology & High Density Packaging(2011 电子封装技术与高密度封装国际会议)

作者： Luqiao Yin Lianqiao Yang Weiqiao Yang Guangming Xu Huafeng Yan Yu Chen Shuzhi Li Jianhua Zhang Key Laboratory of Advanced Display and System Applications (Shanghai University) Ministry of Educat Key Laboratory of Advanced Display and System Applications (Shanghai University) Ministry of Educat Shanghai Yaming Lighting co. Ltd.P.O.B 143 149 Yanchang Rd. Shanghai University Shanghai 200072 Shanghai Research Center of Engineering and Technology for Semiconductor Lighting Key Laboratory of Advanced Display and System Applications (Shanghai University) Ministry of Educat

Die interconnection layer is one of the main factors to improve the HP-LED thermal issue as it is the main thermal transfer media from the HP-LED chip to the substrate or heat sink. Silver epoxy is now widely used for LED interconnection, but it becomes more and more difficult for efficient heat dissipation as the HP-LED electric power density becomes higher and higher. Nowadays more and more attentions have been moved to metallic eutectic interconnection, especially for solder paste and AuSn20 eutectic interconnection which have big potential to be used for HP-LED. In order to further understand the thermal characteristics and reliability of HP-LED interconnected by different die-attach materials, the AuSn20 eutectic, solder paste and silver epoxy were applied to HP-LED respectively. The transient thermal resistance, steady state junction temperature and optical durability of the HP-LEDs are tested and studied. For HP-LED interconnected by AuSn20 eutectic, solder paste and silver epoxy, when applied 450 mA working current, the transient thermal resistance of die attach layer are 2.5 K/W, 3.2 K/W and 4 K/W respectively, and the junction temperature variation are 0.4%, 9.6% and 6.6% respectively after about 1180 hours 85 ℃/85 H aging. The results show the AuSn20 eutectic has better thermal performances and optical durability than the solder paste and silver epoxy.

关键词： Thermal resistance Microassembly Materials Silver Junctions Transient analysis

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systematic studies on fractal scan model for Flat Panel display (FPD) controllers

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International Journal of Manufacturing Research 2011年第4期6卷 367-379页

作者： Xu, M. Ran, F. Chen, Z. School of Mechatronical Engineering and Automation Shanghai University Shanghai 200072 China Key Laboratory of Advanced Display and System Application Ministry of Education Shanghai University Shanghai 200072 China Microelectronic Research and Development Centre Shanghai University Shanghai 200072 China

This paper presents the design and logic implementation of the fractal scan algorithm based on the mathematical model of the optimal scan architecture. Through the exploration of the sub-space code sequences and bit code sequences for different grey levels, we deduce the general formulae for the sequences and propose the corresponding logic implementations including the fractal scanning IP core and the general grey-level controller for Flat Panel display (FPD). The parameterised IP core for various grey levels, embedded in FPD scan controller, can efficiently increase the scan utilisation and imaging quality. This research provides a new engineering way to solve a pressing problem of high resolution FPD technology. Copyright © 2011 Inderscience Enterprises Ltd.

关键词： Controllers

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Thin Film Encapsulation for OLED display using Silicon Nitride and Silicon Oxide Composite Film

Thin Film Encapsulation for OLED Display using Silicon Nitri...

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2011 12th International Conference on Electronic Packaging Technology & High Density Packaging(2011 电子封装技术与高密度封装国际会议)

作者： Jianhua zhang Renzheng Sang Hao Zhang Li Long Bin Wei Jianling Yu Xingyang Wu Zikai Hua Tao Feng Key Laboratory of Advanced Display and System Applications Ministry of Education Shanghai Universi The School of Mechanical & Electronic Engineering and Automation Shanghai University Shanghai 200 Key Laboratory of Advanced Display and System Applications Ministry of Education Shanghai Universi The Linde Group Carl-von-Linde-Strasse 25 85716 Unterchleissheim Germany

In this paper, SiNx and SiOx films for OLED encapsulation were deposited by plasma-enhanced chemical vapor deposition (PECVD). The properties, including surface roughness, scratch adhesion between the films and substrates, water vapor permeation rate were investigated. The results showed that the root-mean-square (Rms) surface roughness of encapsulation film could be improved from 2.7 nm to 1.2 nm by depositing SiNx onto SiOx film. The SiOx film exhibited stronger adhesion strength to PET substrates compared with SiNx. The moisture barrier capability was enhanced immensely when SiOx/SiNx composite film instead SiNx or SiOx film. Moreover, according to the tests results, OLED devices were designed and fabricated on plastic substrates, were encapsulated with the optimized SiOx/SiNx composite film. The OLED devices can keep emitting during bending, the films were not found to crack. The results indicate that SiOx/SiNx composite film is a potential choice for the OLED encapsulation. Then more tests are needed in order to get a more precise investigation.

关键词： Films Organic light emitting diodes Substrates Encapsulation Adhesives Moisture Silicon

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Interactive object segmentation using iterative adjustable graph cut

Interactive object segmentation using iterative adjustable g...

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IEEE Visual Communications and Image Processing (VCIP)

作者： Ran Shi Zhi Liu Yinzhu Xue Xiang Zhang School of Communication and Information Engineering Shanghai University Shanghai China Key Laboratory of Advanced Display and System Application Ministry of Education Shanghai University Shanghai China Institute of Image Processing and Pattern Recognition Shanghai Jiaotong University Shanghai China

Interactive object segmentation is widely used for extracting any user-interested objects from natural images. A common problem with many interactive segmentation approaches is that the object segmentation quality is degraded due to inaccurate object/background seeds provided by the user. This paper proposes an iterative adjustable graph cut to efficiently solve this problem. First, object/background seeds are initialized based on the object segmentation result obtained with the user-specified scribbles as the interactive input. Then, an iterative seed adjustment scheme is exploited to correct inaccurate seeds and extract new suitable seeds via graph cut, in which the balancing weight between energy terms are adaptively updated to protect stable seeds and speedup the iteration process. Finally, suitable seeds are obtained and graph cut is used to segment the objects. Experimental results demonstrate the better segmentation performance of our approach even if user provides rather rough seeds.

关键词： Object segmentation Image segmentation Reliability Iterative methods Educational institutions Image color analysis Error analysis

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A new two-phase fluid dispensing technology for the adhesive distribution

A new two-phase fluid dispensing technology for the adhesive...

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2011 IEEE International Conference Mechatronics and Automation(2011 IEEE机电一体化与自动化国际会议)

作者： Peng Peng Jianhua Zhang Jinsong Zhang School of Mechatronics Engineering and Automation Key Laboratory of Advanced Display and System Applications of Ministry of Education Shanghai University Shanghai P.R. China

The fluid dispensing with a controllable method is one of the key technologies in electronic packaging. The the higher accuracy and consistency boosts the emergence of the new fluid dispensing technologies. This paper first adopted the two-phase fluid principle for the fluid dispensing technology and designed and fabricated the unique dispenser prototype. The slug flow was a stable flow type in the two-phase fluid with an intermittent bubbles and droplets. To control the flow parameters of the two fluids which were the compressed gas and adhesive, it performed an intermittent and a persistent fluid dispensing process. The accurate and uniform droplets without satellite points had the same volume and mass were 660.6nL and 766μg, while the adhesive, compressed gas and electromagnetic valve had a flow rale for 1.4mL/min, a pressure for 80KPa and a frequency for 8Hz, respectively. As the gas pressure dropped down to 60KPa and the adhesive flow rate was 2.0ml7min, the adhesive dispensed to the substrate in a stream mode with a width for 2.3mm.

关键词： dispensing technology two-phase fluid dispensing adhesive uniformity

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High-performance n-channel organic thin-film transistors based on the dual effects of heterojunction and surface modification

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Chinese Physics B 2010年第3期19卷 456-461页

作者：曹进洪飞邢菲菲顾文郭新安张浩魏斌张建华王军 Key Laboratory of Advanced Display and System Application(Shanghai University) Special Display Technology(Hefei University of Technology) Ministry of Education Chemistry Department College of SciencesShanghai University

This paper presents two n-channel organic heterojunction transistors with modified insulator by using hexadecafiuorophthalocyaninatocopper （F16CuPc）/copper phthalocyanine （CuPc） and F16CuPc/pentacene as the active layers. Compared with a single-layer device, it reports that an improved field-effect mobility and a 6-fold higher drain current are observed. The highest mobility of 0.081 cm^2/（V. s） was obtained from F16CuPc/CuPc heterojunction devices. This result is attributed to the dual effects of the organic heterojunction and interface modification. Furthermore, for two heterojunction devices, the performance of the F16CuPc/CuPc-based transistor is better than that of F16CuPc/pentacene. This is attributed to the morphologic match of two organic components.

关键词： n-channel heterojunction effect surface modification

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Study of GaN-based Light-emitting Diodes with Double Roughened Surfaces

Study of GaN-based Light-emitting Diodes with Double Roughen...

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2011 12th International Conference on Electronic Packaging Technology & High Density Packaging(2011 电子封装技术与高密度封装国际会议)

作者： Jianhua Zhang Lianqiao Yang Jianzheng Hu Key Laboratory of Advanced Display and System Applications (Shanghai University) Ministry of Educat Institute of RD Group Rainbow Optoelectronics Material Shanghai Co.ltd.

In this paper, GaN-based blue light emitting diodes with double roughened surfaces were fabricated and compared with planar LEDs and these with single roughened layer. The double roughened surfaces were fulfilled by patterned sapphire substrates (PSS) and roughened p-GaN surface. Magnesium treatment during the growth process was used to produce p-GaN surface roughening. After the epitaxial growth, the four group samples were fabricated using the standard process (four mask steps) with a mesa area of 10x23 mil2. At last, 25 LED devices were packaged for each group using the same packaging material and by the same method. It was found that import of PSS and roughened p-GaN surface may lead to a little higher voltage by simply copying the epitaxial process of planar LED. However, even fabricated by the non-optimized epitaxial process, comparing with planar LEDs, the optical power of the package can be increased by 40.1% by using the patterned sapphire substrate, 10.2% by using p-GaN surface roughing, and 44.9% by using double roughing technologies.

关键词： Light emitting diodes Surface roughness Rough surfaces Surface treatment Substrates Gallium nitride Optical device fabrication

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Dependence of charge trapping of fluorescent and phosphorescent dopants in organic light-emitting diodes on the dye species and current density

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Chinese Physics B 2010年第3期19卷 450-455页

作者：魏斌廖英杰刘纪忠路林曹进王军张建华 Key Laboratory of Advanced Display and System Applications Ministry of Education Shanghai University

This paper utilizes multilayer organic light-emitting diodes with a thin layer of dye molecules to study the mech- anism of charge trapping under different electric regimes. It demonstrates that the carrier trapping was independent of the current density in devices using fluorescent material as the emitting molecule while this process was exactly opposite when phosphorescent material was used. The triplet-triplet annihilation and dissociation of excitons into free charge carriers was considered to contribute to the decrease in phosphorescent emission under high electric fields. Moreover, the fluorescent dye molecule with a lower energy gap and ionized potential than the host emitter was observed to facilitate the carrier trapping mechanism, and it would produce photon emission.

关键词： organic light-emitting diodes excitation mechanism charge trapping current density

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