Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360698
Shun-yuan Ke, Wei-ming Lin
Due to low cost and high efficiency advantages, AC-DC single-stage LED driver has been widely used, But there is existing the problem of larger twice line frequency output ripple, and current ripple is one of the important factors to affect LED light-emitting properties and lifetime. A suitable kind of LED driver that single-stage flyback PFC circuit based on auxiliary winding and current ripple suppression strategies is proposed in this paper, the working principle of the proposed circuit and the implementation condition of low output current ripple are analyzed in detail. The simulation and experiment are carried out to verify the correctness and feasibility of the theoretical analysis, in switch the output current ripple can be reduced effectively through the proposed single-stage LED driver, and the input characteristics doesn't be affected.
{"title":"A novel lower output ripple single-stage flyback LED driver","authors":"Shun-yuan Ke, Wei-ming Lin","doi":"10.1109/SSLCHINA.2015.7360698","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360698","url":null,"abstract":"Due to low cost and high efficiency advantages, AC-DC single-stage LED driver has been widely used, But there is existing the problem of larger twice line frequency output ripple, and current ripple is one of the important factors to affect LED light-emitting properties and lifetime. A suitable kind of LED driver that single-stage flyback PFC circuit based on auxiliary winding and current ripple suppression strategies is proposed in this paper, the working principle of the proposed circuit and the implementation condition of low output current ripple are analyzed in detail. The simulation and experiment are carried out to verify the correctness and feasibility of the theoretical analysis, in switch the output current ripple can be reduced effectively through the proposed single-stage LED driver, and the input characteristics doesn't be affected.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121929106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360686
G. Lu, Ming-ming Hao, Canxiong Lai, Bin Yao
We showed a detailed thermal simulation of a high power flip-chip packaged LED, simulation results show that the junction temperature of the LED is more sensitive to the adhesive layer material between the Si substrate and the 1000μm thick Cu heatsink, and less sensitive to the bonding ball material and the heatsink material. Furthermore, three groups of aging tests were conducted on this type of high power flip chip LED, according to the linear regression analysis, the extrapolated lifetime of the high power flip chip LED at 25°C is 37718 hours, we also obtain an acceleration factor 70.5 of resulting in a thermal activation energy of Ea=0.35eV using Arrhenius function.
{"title":"Thermal analysis and reliability evaluation on high power flip chip LED","authors":"G. Lu, Ming-ming Hao, Canxiong Lai, Bin Yao","doi":"10.1109/SSLCHINA.2015.7360686","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360686","url":null,"abstract":"We showed a detailed thermal simulation of a high power flip-chip packaged LED, simulation results show that the junction temperature of the LED is more sensitive to the adhesive layer material between the Si substrate and the 1000μm thick Cu heatsink, and less sensitive to the bonding ball material and the heatsink material. Furthermore, three groups of aging tests were conducted on this type of high power flip chip LED, according to the linear regression analysis, the extrapolated lifetime of the high power flip chip LED at 25°C is 37718 hours, we also obtain an acceleration factor 70.5 of resulting in a thermal activation energy of Ea=0.35eV using Arrhenius function.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130576419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Si-doped GaN films was, grown on 4H-SiC by metal-organic chemical vapor deposition. It was found that the compressively strained layer of the film can be relaxed and surface structural quality can be improved by increasing the thickness of Si-doped GaN film. The critical thickness of beginning of two-dimension growth of GaN on 4H-SiC substrate by metal-organic chemical vapor deposition (MOCVD) has been systematically studied. We optimized growth time of GaN layer so that the GaN layer structral quality can be improved and the root mean square (RMS) roughness of surface can be reduced. With suitable growth time of GaN layer, crack-free 600 nm GaN was obtained and the full-width at half-maximum (FWHM) of (0 0 2) plane rocking curve measured by double crystal X-ray diffraction (DCXRD) was as low as 279.6 arcsec. This kind of film can be used as a high-quality buffer layer between the substrate and epitaxial layer.
{"title":"Structural characterization of hexagonal GaN thin films grown by MOCVD on 4H-SiC substrate","authors":"Heng Zhang, Longfei Xiao, Shuang Qu, Chengxin Wang, Xiaobo Hu, Xiangang Xu","doi":"10.1109/SSLCHINA.2015.7360683","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360683","url":null,"abstract":"A Si-doped GaN films was, grown on 4H-SiC by metal-organic chemical vapor deposition. It was found that the compressively strained layer of the film can be relaxed and surface structural quality can be improved by increasing the thickness of Si-doped GaN film. The critical thickness of beginning of two-dimension growth of GaN on 4H-SiC substrate by metal-organic chemical vapor deposition (MOCVD) has been systematically studied. We optimized growth time of GaN layer so that the GaN layer structral quality can be improved and the root mean square (RMS) roughness of surface can be reduced. With suitable growth time of GaN layer, crack-free 600 nm GaN was obtained and the full-width at half-maximum (FWHM) of (0 0 2) plane rocking curve measured by double crystal X-ray diffraction (DCXRD) was as low as 279.6 arcsec. This kind of film can be used as a high-quality buffer layer between the substrate and epitaxial layer.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129857790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360681
Hao Zhu, Jianfei Xi, J. G. Liu
As UV LED technology advances, more and more new applications emerge. This paper describes design, fabrication and packaging of a vertical-structured UV LED device. Laser lift-off (LLO) method is used in the fabrication of a 45mil × 45mil LED, which allows us to remove the Sapphire substrate and absorptive GaN layers in the epitaxy. By doing this, the UV light absorption within the epitaxy is minimized and the efficacy of the device is significantly improved. In this paper, we will describe the fabrication process for achieving higher efficiency UVA chip, and report the device performance. Packaging technology and failure mechanisms under UV condition will also be discussed.
{"title":"Fabrication and packaging of a vertical-structured UV LED device by laser lift-off of Sapphire","authors":"Hao Zhu, Jianfei Xi, J. G. Liu","doi":"10.1109/SSLCHINA.2015.7360681","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360681","url":null,"abstract":"As UV LED technology advances, more and more new applications emerge. This paper describes design, fabrication and packaging of a vertical-structured UV LED device. Laser lift-off (LLO) method is used in the fabrication of a 45mil × 45mil LED, which allows us to remove the Sapphire substrate and absorptive GaN layers in the epitaxy. By doing this, the UV light absorption within the epitaxy is minimized and the efficacy of the device is significantly improved. In this paper, we will describe the fabrication process for achieving higher efficiency UVA chip, and report the device performance. Packaging technology and failure mechanisms under UV condition will also be discussed.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124957897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360676
C. Yan, Spring Bai, Tim Nie, Vincent Wang
High-power green LEDs in mass-production is reaching a new WPE (wall-plug-efficiency) level of 35%, and this progress results from both band- and strain-engineering in the active multiple-quantum-well region and optimal p- and n-electrodes layout for uniform current spreading. For high-power green LEDs of chip size 45 mil×45 mil (4545 chips), the forward voltage at 350 mA is as low as 2.8 V, with emitting power of 345 mW and emitting flux of 152 lumen at a dominant wavelength of 525 nm. These data translate into an external quantum efficiency of 41.7% and a luminous efficacy of 153 lm/W, with peak luminous efficacy over 280lm/W. It is envisioned that these high-power high-efficiency green LEDs will open up new market applications such as high-end healthy-lighting and mitigate the so-called “green-gap” for another level of the solid-state general lighting.
{"title":"High-power high-efficiency green LEDs","authors":"C. Yan, Spring Bai, Tim Nie, Vincent Wang","doi":"10.1109/SSLCHINA.2015.7360676","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360676","url":null,"abstract":"High-power green LEDs in mass-production is reaching a new WPE (wall-plug-efficiency) level of 35%, and this progress results from both band- and strain-engineering in the active multiple-quantum-well region and optimal p- and n-electrodes layout for uniform current spreading. For high-power green LEDs of chip size 45 mil×45 mil (4545 chips), the forward voltage at 350 mA is as low as 2.8 V, with emitting power of 345 mW and emitting flux of 152 lumen at a dominant wavelength of 525 nm. These data translate into an external quantum efficiency of 41.7% and a luminous efficacy of 153 lm/W, with peak luminous efficacy over 280lm/W. It is envisioned that these high-power high-efficiency green LEDs will open up new market applications such as high-end healthy-lighting and mitigate the so-called “green-gap” for another level of the solid-state general lighting.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129832958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
White light emitting diodes (LEDs) have been regarded as the most promising light sources of new lighting technology due to the properties of high efficiency, energy saving, long lifetime and environmentally friendly. As the key materials used in white LED devices, phosphors strongly influence the properties of the white LED devices, such as luminous efficiency, service life, display color gamut and the color rendering. In this review, we introduced the photochromic properties, development actuality and the trend of the widely used yellow aluminate phosphors, red nitrides phosphors and green oxynitride phosphors. The preparation of these classic aluminate phosphors and red nitride phosphors are tending to be mature. Therefore, the performance of phosphors above is promoted slowly. However, along with the progress of semiconductor lighting technology, it's necessary to develop new phosphors which are applicable in high power excitation source containing full spectrum lighting and wide color gamut display. So the study of new phosphors becomes the research hot spot and key development orientation in the world. New yellow nitride phosphors, green oxynitride phosphors and red fluoride phosphors are springing up time to time. But properties of these new phosphors still need to be improved in many aspects, such as composition adjusting and preparation technology. In addition, China has become a big country of phosphors production and application in the world. As the quality of phosphors improving and the market share of China increasing, China will play a more important role in the technical innovation and products supply of LED phosphors in the future.
{"title":"Research on trend of worldwide white LED phosphors technologies and market development","authors":"Yuanhong Liu, Ronghui Liu, XiaoLe Ma, Guantong Chen, Yanfeng Li, Chunpei Yan, Jiyou Zhong","doi":"10.1109/SSLCHINA.2015.7360684","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360684","url":null,"abstract":"White light emitting diodes (LEDs) have been regarded as the most promising light sources of new lighting technology due to the properties of high efficiency, energy saving, long lifetime and environmentally friendly. As the key materials used in white LED devices, phosphors strongly influence the properties of the white LED devices, such as luminous efficiency, service life, display color gamut and the color rendering. In this review, we introduced the photochromic properties, development actuality and the trend of the widely used yellow aluminate phosphors, red nitrides phosphors and green oxynitride phosphors. The preparation of these classic aluminate phosphors and red nitride phosphors are tending to be mature. Therefore, the performance of phosphors above is promoted slowly. However, along with the progress of semiconductor lighting technology, it's necessary to develop new phosphors which are applicable in high power excitation source containing full spectrum lighting and wide color gamut display. So the study of new phosphors becomes the research hot spot and key development orientation in the world. New yellow nitride phosphors, green oxynitride phosphors and red fluoride phosphors are springing up time to time. But properties of these new phosphors still need to be improved in many aspects, such as composition adjusting and preparation technology. In addition, China has become a big country of phosphors production and application in the world. As the quality of phosphors improving and the market share of China increasing, China will play a more important role in the technical innovation and products supply of LED phosphors in the future.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133982847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Smooth and vertical facets for InGaN/GaN double heterostructure lasers grown on sapphire substrate are formed via a two-step method of dry etching and wet chemical etching. This two-step process consists of an inductively coupled plasma (ICP) etching with Ni metal as an etching mask to define the cavity length of the laser bars, followed by crystallographic wet etching in AZ400K developer to reduce the roughness and improve verticality of the sidewall. Optimization of ICP etching processes included the gas flow rate of Cl2/Ar and the radiofrequency (RF) power to obtain a heavily striated facet angle of 3° from vertical. Combined with the wet etching processes, the facets along 〈112̅̅0〉 direction became smooth and vertical due to the preferentially etching feature of AZ400K in exposing the (101̅0) and other (101̅n)-type planes because of their slow etch rates compared with the other planes. To confirm the feasibility of the two-step etching facets, optically pumping experiment was carried out on InGaN/GaN double heterostructure lasers. Lasing behaviors of longitudinal mode peaked at 375 nm with a narrow line width of 1.3 nm was demonstrated on the laser using this two-step etching process, and proved it an effective way for laser facets fabrication method.
{"title":"GaN-based violet lasers grown on sapphire with a novel facet fabrication method","authors":"Yingdong Tian, Yun Zhang, Jianchang Yan, Xiang Chen, Yanan Guo, Xuecheng Wei, Junxi Wang, Jinmin Li","doi":"10.1109/SSLCHINA.2015.7360680","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360680","url":null,"abstract":"Smooth and vertical facets for InGaN/GaN double heterostructure lasers grown on sapphire substrate are formed via a two-step method of dry etching and wet chemical etching. This two-step process consists of an inductively coupled plasma (ICP) etching with Ni metal as an etching mask to define the cavity length of the laser bars, followed by crystallographic wet etching in AZ400K developer to reduce the roughness and improve verticality of the sidewall. Optimization of ICP etching processes included the gas flow rate of Cl2/Ar and the radiofrequency (RF) power to obtain a heavily striated facet angle of 3° from vertical. Combined with the wet etching processes, the facets along 〈112̅̅0〉 direction became smooth and vertical due to the preferentially etching feature of AZ400K in exposing the (101̅0) and other (101̅n)-type planes because of their slow etch rates compared with the other planes. To confirm the feasibility of the two-step etching facets, optically pumping experiment was carried out on InGaN/GaN double heterostructure lasers. Lasing behaviors of longitudinal mode peaked at 375 nm with a narrow line width of 1.3 nm was demonstrated on the laser using this two-step etching process, and proved it an effective way for laser facets fabrication method.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117075027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360696
W. Feng, Bruce Feng, Fanny Zhao, Brian Shieh, Ricky S. W. Lee
In the present study, a computational model of LED filament light bulb was established by the ANSYS Icepak software based on the finite element method (FEM) and was compared with the experimental data as well. With the developed model, the effects of the filling gas and the filament substrate on the steady-state thermal performance were investigated. The simulation results revealed that the thermal conductivity of the filling gas in the bulb had a significant influence on the heat dissipation of the bulb. Compared with air filling, helium can reduce the average junction temperature of LED chips bonded on the sapphire substrate by 54.6 °C. With a glass filament substrate and helium filling in the bulb as the base case, the average junction temperature reductions of LED chips bonded on transparent ceramics, sapphire and perforated copper were 9.6 °C, 11.4 °C, and 22.4 °C, respectively. It was found that the higher the thermal conductivity of the filling gas, the less junction temperature change would be resulted from different filament substrates. In conclusion, this model can benefit the optimization of thermal design for a LED filament light bulb.
{"title":"Simulation and optimization on thermal performance of LED filament light bulb","authors":"W. Feng, Bruce Feng, Fanny Zhao, Brian Shieh, Ricky S. W. Lee","doi":"10.1109/SSLCHINA.2015.7360696","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360696","url":null,"abstract":"In the present study, a computational model of LED filament light bulb was established by the ANSYS Icepak software based on the finite element method (FEM) and was compared with the experimental data as well. With the developed model, the effects of the filling gas and the filament substrate on the steady-state thermal performance were investigated. The simulation results revealed that the thermal conductivity of the filling gas in the bulb had a significant influence on the heat dissipation of the bulb. Compared with air filling, helium can reduce the average junction temperature of LED chips bonded on the sapphire substrate by 54.6 °C. With a glass filament substrate and helium filling in the bulb as the base case, the average junction temperature reductions of LED chips bonded on transparent ceramics, sapphire and perforated copper were 9.6 °C, 11.4 °C, and 22.4 °C, respectively. It was found that the higher the thermal conductivity of the filling gas, the less junction temperature change would be resulted from different filament substrates. In conclusion, this model can benefit the optimization of thermal design for a LED filament light bulb.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116786420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360694
G. Sun, Shasha Du, Youxing Yuan, Zhiping Zeng, J. G. Liu
Mid-power LED in a lead-frame package is the most commonly used LED for LCD backlighting and retrofit LED light source such as light bulb and linear light tube replacement. The lead-frame package consists silver plated copper and white plastic housing, both for the purpose of increasing light reflection. The silver can gradually become darkening when reacting with certain organics gas or chemical compounds, especially at high temperature and under light radiation. This resulted in light decay of LED product. Sulfur and its oxides are common pollutants in the atmosphere, which will form black silver sulfide with the silver plating. The blackening phenomenon is usually more severe in the silver layer of leadframe around the heat source, the LED chip where temperature and light radiation are highest. Even under the condition without light, samples after sulfur exposure treatment for only dozens of minutes will indicate obvious blackening phenomenon surrounding the LED chip.This paper will focus on the sulfur induced LED packaging failure. The failure mechanism of silver darkening will be discussed. Due to the lack of reliability test standard in a sulfur containing environment, it is hard to run an accelerated reliability test for a given condition. In this paper, we will try to develop a test method to effectively evaluate the susceptibility of a LED package to sulfur and to estimate its lumen reduction rate. Finally, we will give some recommendations for metal coating layer, encapsulant material, and surface treatment to reduce the sulfur impact. With a proper design, right material selection, and controlled temperature conditions, lead-frame LED package can be reliability used in most lighting fixtures and display applications.
{"title":"Failure mode and test method of sulfur induced light decay in lead-frame LED package","authors":"G. Sun, Shasha Du, Youxing Yuan, Zhiping Zeng, J. G. Liu","doi":"10.1109/SSLCHINA.2015.7360694","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360694","url":null,"abstract":"Mid-power LED in a lead-frame package is the most commonly used LED for LCD backlighting and retrofit LED light source such as light bulb and linear light tube replacement. The lead-frame package consists silver plated copper and white plastic housing, both for the purpose of increasing light reflection. The silver can gradually become darkening when reacting with certain organics gas or chemical compounds, especially at high temperature and under light radiation. This resulted in light decay of LED product. Sulfur and its oxides are common pollutants in the atmosphere, which will form black silver sulfide with the silver plating. The blackening phenomenon is usually more severe in the silver layer of leadframe around the heat source, the LED chip where temperature and light radiation are highest. Even under the condition without light, samples after sulfur exposure treatment for only dozens of minutes will indicate obvious blackening phenomenon surrounding the LED chip.This paper will focus on the sulfur induced LED packaging failure. The failure mechanism of silver darkening will be discussed. Due to the lack of reliability test standard in a sulfur containing environment, it is hard to run an accelerated reliability test for a given condition. In this paper, we will try to develop a test method to effectively evaluate the susceptibility of a LED package to sulfur and to estimate its lumen reduction rate. Finally, we will give some recommendations for metal coating layer, encapsulant material, and surface treatment to reduce the sulfur impact. With a proper design, right material selection, and controlled temperature conditions, lead-frame LED package can be reliability used in most lighting fixtures and display applications.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133635943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360688
Mengni Zhang, Jiajie Fan, C. Qian, Y. Li, Xuejun Fan, Aimin Ji, Guoqi Zhang
By using a blue light source converted by phosphors to obtain white light emission, phosphor-converted white light emitting diodes (pc-white LEDs) are becoming as one of substitutes of traditional general lighting sources due to their advantages in energy saving, environment-friendliness, color controllability and long lifetime. Within pc-white LEDs, the phosphor films consisting of inorganic phosphor powders and silicone have a great effect on the luminous efficacy, color stability and color rendering properties of the LEDs. Additionally, as being close to LED chips, the phosphor film always suffers a high temperature when the LED operates. Thus, the photoluminescence and thermal effect of phosphor films become the essential research topics to identify the resulting failure mechanisms in LEDs. This study selected five widely used inorganic phosphor powers with Garnets, Silicates, Aluminates and Nitrides bases mixed with silicone to prepare the phosphor films. Then, with a 450nm InGaN blue chip as an excitation source, a thermal-controllable platform was installed in an integrating sphere to measure the thermal transient photoluminescence properties of these above prepared phosphor films. Finally, optical simulations using the LightTools software were conducted to predict the spectral power distributions (SPDs) of the pc-white LEDs with selected phosphors films. The simulated SPDs are in reasonable agreement with those measured from experiments. This implies the proposed simulation method can be a useful tool instead of physical experiments in the phosphor design for pc-white LEDs.
{"title":"Investigation of photoluminescence and thermal effect of phosphor films used in phosphor-converted white LEDs","authors":"Mengni Zhang, Jiajie Fan, C. Qian, Y. Li, Xuejun Fan, Aimin Ji, Guoqi Zhang","doi":"10.1109/SSLCHINA.2015.7360688","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360688","url":null,"abstract":"By using a blue light source converted by phosphors to obtain white light emission, phosphor-converted white light emitting diodes (pc-white LEDs) are becoming as one of substitutes of traditional general lighting sources due to their advantages in energy saving, environment-friendliness, color controllability and long lifetime. Within pc-white LEDs, the phosphor films consisting of inorganic phosphor powders and silicone have a great effect on the luminous efficacy, color stability and color rendering properties of the LEDs. Additionally, as being close to LED chips, the phosphor film always suffers a high temperature when the LED operates. Thus, the photoluminescence and thermal effect of phosphor films become the essential research topics to identify the resulting failure mechanisms in LEDs. This study selected five widely used inorganic phosphor powers with Garnets, Silicates, Aluminates and Nitrides bases mixed with silicone to prepare the phosphor films. Then, with a 450nm InGaN blue chip as an excitation source, a thermal-controllable platform was installed in an integrating sphere to measure the thermal transient photoluminescence properties of these above prepared phosphor films. Finally, optical simulations using the LightTools software were conducted to predict the spectral power distributions (SPDs) of the pc-white LEDs with selected phosphors films. The simulated SPDs are in reasonable agreement with those measured from experiments. This implies the proposed simulation method can be a useful tool instead of physical experiments in the phosphor design for pc-white LEDs.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123307161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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