LED teperature effect - Thermal Grease test report v1
芯片封装的热阻分析
芯⽚封装的热阻分析概述半导体器件散热的三个主要途径是:封装顶部到空⽓，或者封装顶部到散热⽚再到空⽓封装底部到电路板封装引脚到电路板在JEDEC中以热阻Theta来表⽰，其中ThetaJA参数综合了Die的⼤⼩, 封装⽅式，填充材料，封装材料，引脚设计，外部散热⽚和外部电路板的属性多个因素；ThetaJC和ThetaJB这2个参数是表征芯⽚和封装本⾝的，不会随着芯⽚封装外部环境的改变⽽改变。
关于芯⽚外部温度的趣事半导体元器件"烫⼿"未必不正常，55C摄⽒温度就会让⼈感觉发烫，很多⼤功率的芯⽚，表⾯温度可以达到85C摄⽒度以上。
对于Thermal测量的⼏个参数的困惑JEDEC对芯⽚封装的热性能参数的定义热阻参数ThetaJA，结到空⽓环境的热阻，= (Tj-Ta)/PThetaJC，结到封装外壳的热阻，= (Tj-Tc)/P, ⼀般⽽⾔是到封装顶部的热阻，所以⼀般的，ThetaJC = ThetaJTThetaJB，结到PCB的热阻， = (Tj-Tb)/P热特性参数PsiJT，结到封装顶部的热参数，=(Tj-Tt)/PPsiJB, 结到封装底部的热参数，=(Tj-Tb)/P其中:Tj - 芯⽚结温Ta - 芯⽚环境温度Tb - 芯⽚底部的表⾯温度Tc/Tt - 芯⽚顶部的表⾯温度按照JESD测量⽅法得出的ThetaJA热阻参数是对封装的品质度量，并⾮是application specific的热阻参数，只能是芯⽚封装的热性能品质参数的⽐较，不能应⽤于实际测量和分析中的结温预测。
PsiJT和PsiJB和ThetaXX参数不同，并⾮是器件的热阻值，只是数学构造物。
ThetaJA 结到空⽓环境的热阻ThetaJA是最常使⽤的热阻参数，也是最容易引起误解的参数。
IDT公司的定义ThetaJA = (Tj - Ta)/PThetaJA = (ThetaJB + ThetaBA) || (ThetaJC + ThetaCA);其中ThetaXY = (Tx - Ty)/PAltera公司的定义Without a heat sink, ThetaJA = ThetaJC + ThetaCA = (Tj - Ta)/PWith a heat sink , ThetaJA = ThetaJC + ThetaCS + ThetaSA = (Tj - Ta)/P实际上，Altera公司对加散热器的ThetaJA的定义不够严谨，散热器的引⼊相当于增加了⼀个散热通道，即增加了从管壳(Case)到散热器(heat Sink)的散热通道，所以加⼊散热器后，ThetaJA(heat sink) = ThetaJC + ( ThetaCA || ( ThetaCS + ThetaSA) )由于ThetaCA >> (ThetaCS + ThetaSA), 所以上式才可以近似化简为:ThetaJA = ThetaJC + ThetaCS + ThetaSA, 其中ThetaCS通常是导热硅脂或者硅胶, 热阻⾮常⼩TI公司的定义根据TI⽂档spra953c的描述, JESD定义ThetaJA的初衷是为了⼀种封装的相对热阻性能可以被互相⽐较，⽐如TI公司的某个芯⽚的热阻性能和其它公司的热阻性能做对⽐，前提是两家公司都是⽤JESD51-x中规定的标准⽅法来做测试，但是⼤部分芯⽚的热阻系数不会严格按照JESD51中规定的标准⽅法进⾏测量。
温度升高对LED各光电参数及可靠性的影响
温度升⾼对LED各光电参数及可靠性的影响温度升⾼对LED各光电参数及可靠性的影响2011/6/30 作者：未知来源：电⼦元件技术导读：本⽂详细分析了温度升⾼对LED各光电参数及可靠性的影响，以利于LED芯⽚和 LED照明产品的设计开发。
标签：可靠性结温LED寿命光通量光效光⾊配光曲线⾊温显⾊性led(Light Emitting Diode：发光⼆极管) 作为第四代光源，因其节能、环保、长寿命等优点极具发展前景。
但因为LED对温度极为敏感，结温升⾼会影响LED的寿命、光效、光⾊(波长)、⾊温、光形 (配光)以及正向电压、最⼤注⼊电流、光度、⾊度、电⽓参数以及可靠性等。
⼀、温度过⾼会对LED造成永久性破坏(1)LED⼯作温度超过芯⽚的承载温度将会使LED的发光效率快速降低，产⽣明显的光衰，并造成损坏;(2)LED多以透明环氧树脂封装，若结温超过固相转变温度(通常为125℃)，封装材料会向橡胶状转变并且热膨胀系数骤升，从⽽导致LED开路和失效。
⼆、温度升⾼会缩短LED的寿命LED的寿命表现为它的光衰，也就是时间长了，亮度就越来越低，直到最后熄灭。
通常定义LED光通量衰减30%的时间为其寿命。
通常造成LED光衰的原因有以下⼏⽅⾯：(1)LED芯⽚材料内存在的缺陷在较⾼温度时会快速增殖、繁衍，直⾄侵⼊发光区，形成⼤量的⾮辐射复合中⼼，严重降低LED的发光效率。
另外，在⾼温条件下，材料内的微缺陷及来⾃界⾯与电板的快扩杂质也会引⼊发光区，形成⼤量的深能级，同样会加速LED器件的光衰。
(2)⾼温时透明环氧树脂会变性、发黄，影响其透光性能，⼯作温度越⾼这种过程将进⾏得越快，这是LED光衰的⼜⼀个主要原因。
(3)荧光粉的光衰也是影响LED光衰的⼀个主要原因，因为荧光粉在⾼温下的衰减⼗分严重。
所以，⾼温是造成LED光衰，缩短LED寿命的主要根源。
不同品牌LED的光衰是不同的，通常LED⼚家会给出⼀套标准的光衰曲线。
近红外led的发光效率
近红外led的发光效率下载温馨提示：该文档是我店铺精心编制而成，希望大家下载以后，能够帮助大家解决实际的问题。
文档下载后可定制随意修改，请根据实际需要进行相应的调整和使用，谢谢!并且，本店铺为大家提供各种各样类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，如想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by the editor. I hope that after you download them, they can help yousolve practical problems. The document can be customized and modified after downloading, please adjust and use it according to actual needs, thank you!In addition, our shop provides you with various types of practical materials, such as educational essays, diary appreciation, sentence excerpts, ancient poems, classic articles, topic composition, work summary, word parsing, copy excerpts,other materials and so on, want to know different data formats and writing methods, please pay attention!随着科学技术的不断发展，LED技术在各个领域都有着广泛的应用。
低温高效发光二极管原理实验总结
低温高效发光二极管原理实验总结发光二极管（Light Emitting Diode，简称LED）是一种利用半导体材料发出光的电子元件。
随着科技的进步和节能环保意识的提高，LED已经渗透到各个领域，并成为照明行业的重要组成部分。
本篇文章将总结低温高效发光二极管原理实验的相关内容，并探讨其应用潜力。
一、实验原理低温高效发光二极管实验是通过对LED进行降温处理，观察其发光效果和性能变化。
实验中，首先将LED置于低温环境中，然后逐渐升温，记录不同温度下LED的电流、亮度、色温等数据。
实验的目的在于研究LED在不同温度下的工作特性，从而得出最佳工作温度范围，优化其性能。
在实验中，我们采用了常用的红光LED作为研究对象。
红光LED是LED家族中应用最广泛的一种，其在照明、显示、信号传输等领域具有广泛的应用前景。
通过对红光LED进行低温处理，并测量其电流-电压特性曲线、光强变化曲线等，可以得出一些有价值的实验结果。
二、实验结果通过实验，我们获得了以下重要的实验结果：1. 电流-电压特性曲线在不同温度下，红光LED的电流-电压特性曲线呈现出明显的变化。
随着温度的降低，LED的电流-电压曲线逐渐向左下方偏移。
这表明低温环境下，LED的电压降低，需要更小的电流就能够达到相同的发光效果。
这对于LED的电能转化效率提升具有重要意义。
2. 亮度与温度的关系在实验过程中，我们还测量了红光LED的亮度随温度变化的数据。
实验结果显示，随着温度的降低，LED的亮度呈现出上升的趋势。
这意味着将LED放置在低温环境中，可提高其亮度，从而实现高效能的照明效果。
3. 色温的变化我们还测量了红光LED的色温随温度的变化情况。
色温是定义光源颜色性质的重要指标，对于照明产品的质量至关重要。
实验结果显示，在不同温度下，红光LED的色温存在一定的变化。
这意味着通过控制LED的工作温度，可以调节其色温，满足不同的照明需求。
三、应用潜力低温高效发光二极管具有广阔的应用潜力。
LED结温测试
北京海基嘉盛科技有限公司 线性c-delta 函数 d(t) 更容易实现
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得到阶跃响应函数 a(t) 意味着我们了解了整个系统。
电路分析理论 —— RC 网络模型 对于单一的 RC 网络，其时间相应可描述为：
化试验效果以及可靠性筛选等）。
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北京海基嘉盛科技有限公司 结构函数的推导
T3Ster Master: Derivative
18 VIPER1-2 - Ch. 0 16
从原点到这条渐近线之间的x值就是结区到空气环境的热阻也就是稳态情况下的热如何用结构函数识别器件封装内部如固晶层的缺陷北京海基嘉盛科技有限公司达到热稳定状态时的热阻thja探测器件内部的缺陷包括固晶层树脂层的焊接工艺老化试验效果以及可靠性筛选等
北京海基嘉盛科技有限公司
T3Ster 测试原理
硬件实时采集 测量原理：根据先进的 JEDEC 静态测量法（JESD51-1 Static Method） 原理，改变器件的输入功率，使器件温度发生变化。在达到热平衡之前， T3Ster 以 1 s 的告诉采样率实时记录温度随着时间变化的瞬态响应曲线。
a(t ) R 1 exp(t / )
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北京海基嘉盛科技有限公司
对于多个 RC 网络串联，其时间相应可描述为： a(t ) Ri 1 exp(t / i )
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对于通常的热学系统，可以看做一个分布式的 RC 系统，其时间相应为：
LED热学参数测试研究
热阻基本概念
LED热学设计的目的在于预 言LED芯片的结温，所谓结 温是指LED芯片PN结的温 度。
热阻定义为热流通道上的温度差与通道上耗散功率 之比
LED热学参数测试研究
Thermal Resisitance & Thermal Impedance
LED热学参数测试研究
瞬态和稳态热阻
LED结温测量的电试验法
在和相系低 正 关 数正向系,单向电数位电压K: 即流增C温时量/度m，成v-线P-电N性结压相温敏关升感。♣♣♣开开开正关关关向置置置电121压,,,加快快VH电速速流加加I上电M,加流测热I得M,电正测流向量I电正H,测压向量VFi。
电压VFf。 ♣ ΔVF=│ VFi-- VFf│
♣ 腔内尺寸为1 ft3,它与外部环境热隔离。通过前 面门可进入腔内部，提起插销后可打开门,插销放 置在腔外面。当完全闩栓住的时候，装在门上密 封材料被些微地压紧确保外部气流不进入腔内。 为测定腔内环境温度,把一个热电偶安装在后腔壁 上的塑料管内。它通常装备一个T型热电偶和超小 型联接器。
LED热学参数测试研究
path）中各个单个热阻之和。
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为芯片和芯片粘结剂到反射腔之间形成的热阻。
SB
为反射腔，环氧树脂到印刷板间的热阻。
BA
为印刷板和接触环境空气的热沉之间组合的热阻 JS
结温计算:
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LED热学参数测试研究
多元LED热阻
多元LED产品的热阻可
以采用并联热阻的模型
➢半导体结与壳体或环境温度之间的 稳态条件需数秒或数分钟才能达到。 为提高效率,可以采用测量瞬态热阻 抗的方法。
城市LED灯光数据手册 10W-500W 黄色 CLU048-1818C4-22AL1K3说明书
DATA SHEETIntroduction Performance Characteristics Mechanical Dimensions Characteristic Curves ReliabilityPacking Specification PrecautionP 2P 3P 5P 6P 9P 10P 11 CITILED COB SeriesAmber ModelCLU048-1818C4-22AL1K31. Introduction1-1. Product Description1-2. FeaturesCITIZEN ELECTRONICS is the first COB manufacture. Our advanced knowledge and packaging technology for many years has excellent reliability and high quality of our products. CITILED COB Series covers a wide range of luminous flux from a 10W incandescent bulb to a 500W mercury lamp in general lighting sources. The element arrangement of LED package is capable of utilizing light more effectively and higher performance. The new version of CITILED COB Series succeed to reduce the thermal resistance significantly. New version creates more options to match luminaire's products design (ex. High performance , Cost effective , Higher lumen density ,Increased allowable max. If). The outline and LES size is same since version 1. 3-step MacAdam ellipse color definition at Tj=85℃ is available.・ Mechanical Dimensions :28.0×28.0×1.4 (mm)・ Package Structure :Aluminum Base Chip on Board ・ Reference Assembly :M3 screw, Connector ・ CRI (Ra):65 Typ.・ Nominal CCT :2,200K ・ Chromaticity Range :ANSI C78.377:2015.・ Thermal Resistance :0.17C/W ・ Maximum drive current :3240 mA ・ RoHS compliant・ Better die arrangement for optics・ Wide range of luminous flux and high efficacy・ Improved lumen density compared with previous version ・ UL recognized component (E358566)CLU048-1818C4-22A L1K3[1][2][3][4][5][1][2][3][4][5]Product NomenclatureCRI (Ra)CLU04818182200K Typ.65Product shape Die count in series Die count in parallel Nominal CCT2. Performance Characteristics2-1. Electro Optical Characteristics2-2. Absolute Maximum RatingsSymbol RatingPi 202.8*1If 3240*1Ir 1Top -40 ~ +100Tst -40 ~ +100Tc 105*2Tj140*3*1. Input power and forward current are the values when the LED is used within the range of the derating curve in this data sheet.*2. Refer to 3. Outline drawing for Tc measurement point.ParameterInput Power (W)Forward Current (mA)Reverse Current (mA)*3. D.C. Current : Tj = Tc + Rj-c × PiStorage Temperature (C)Case Temperature (C)Junction Temperature (C)Operating Temperature (C)( Tj=85C )R9Tc=25C*Min.Typ.Min.Min.Typ.Max Typ.Typ.Min.Typ.Max.CLU048-1818C4-22AL1K32200K-65-10,19311,583-12,6641381,62047.852.056.20.17Notes :1. Citizen Electronics maintains forward voltage +/-3%, luminous flux +/-10%,Ra and R9 +/-1.*Values of Luminous flux at Tc=25C are provided as reference only.Product codeForward Current ( mA )ThermalResistanceRj-c ( C/W )Nominal CCT Luminous flux( lm )Efficacy ( lm/W )Voltage( V )Ra T ｊ=85CCRI2-3. Chromaticity CharacteristicsNote : Citizen Electronics maintains chromaticity ( x, y ) +/-0.0050.350.400.450.500.400.450.500.55yxx-y chart CIE19312,200KBlack Body LocusANSIANSI C78. 377:20152,200K( 0.5018, 0.4153)* The chromaticity center refers to ANSI C78.377:2015. Please refer to ANSI C78. 377 for the chromaticity center.0.52590.43420.50450.43440.47990.39670.49930.3967Color Region Nominal CCT Center Point ( x, y )ANSI parametera ( x, y )b ( x, y )c ( x, y )d ( x, y ) ( Rated current , Tj=85℃ )3. Mechanical DimensionsUnit : mmTolerances unless otherwise specified : +/-0.3・Internal Circuit18 s 18 p Protection deviceLED deviceCathodeAnodeMarking 1 : Serial No.Marking 2 : CRI CCTDies count in parallel Dies count in series CLU048H 18 18 ** **4. Characteristic Curves4-1. Forward Current Characteristics / Temperature CharacteristicsForward Current vs. Forward VoltageForward Current vs. Relative Luminous FluxTc=25C Tc=25CCase Temperature vs. Forward VoltageCase Temperature vs. Relative Luminous FluxIf=1620mAIf=1620mA48.050.052.054.056.058.060.001000200030004000V f [V ]If [mA]0%20%40%60%80%100%120%140%160%180%200%01000200030004000R e l a t i v e L u m i n o u s F l u x [a .u .]If [mA]50.051.052.053.054.055.056.00255075100V f [V ]Tc [C]0%20%40%60%80%100%120%0255075100R e l a t i v e L u m i n o u s F l u x [a .u .]Tc [C]4-2. Optical CharacteristicsSpectrumTj=85℃If=1620mA0%10%20%30%40%50%60%70%80%90%100%380430480530580630680730780R a d i a t i v e I n t e n s i t yWave length [nm]2,200KRadiation Characteristic 0%20%40%60%80%100%X Y80°70°60°50°40°30°20°10°-80°-70°-60°-50°-20°-30°-40°-10°90°-90°Case Temperaturevs. Allowable Forward Current05001000150020002500300035000255075100125I f [m A ]Tc [C]4-2. Optical Characteristics (continued)4-3. Derating Characteristics5. Reliability5-1. Reliability Test5-2. Failure Criteria-40 C × 30 minutes – 100 C × 30 minutes, 100 cycle85 C, 85 %RH for 500 hoursThermal Shock TestContinuous Operation Test High Temperature Storage TestLow Temperature Storage Test Moisture-proof Test IF=1620mA Tj=140C (with Al-fin) ×1000hrsTest Item100 C × 1000 hours -40 C × 1000 hours Test ConditionIF=1620mA Ta=25C (with Al-fin) ×1000hrs ( Tc=25C )U defines the upper limit of the specified characteristics. S defines the initial value.Note : Measurement shall be taken between 2 hours and 24 hours, and the test pieces should be return to the normal ambient conditions after the completion of each test.Total Luminous FluxΦvIf=1620mA<S × 0.85Measuring Item Symbol Measuring ConditionFailure CriteriaForward Voltage Vf If=1620mA >U × 1.11675001(2)(1)(3)Example of indication label1. TYPE e.g. CLU048-1818C4-22AL1K32. P.No. ( Cutomer's P/N )3. Lot No.e.g. 4. Quantity(1) Last two digit of the year 16 : year 2016(2) Production month 7 : JuryNote: October, November and December are designated X,Y and Z.(3) CE's control number 6. Packing Specification6-1. PackingAn empty tray is placed on top of a 6-tier tray which contain 30 pieces each.(Smallest packing unit: 180 pieces)A label with product name, quantity and lot number is placed on the upper empty tray.Tray (Dimensions: 310 x 210 x 12 mm / Materials: Electrically conductive PS)Unit : mmProduct 30 pcs/trayCUSTOMERTYPEP.NO Lot No Q'ty: CLU***-******-******* : ****** : ******* : ***--- ( 1 ) --- ( 2 ) --- ( 3 ) --- ( 4 )7. Precaution7-1. Handling with care for this product-Both the light emitting area and white rim around the light emitting area is composed of resin materials.Please avoid the resin area from being pressed, stressed, rubbed, come into contact with sharp metal nail(e.g. edge of reflector part) because the function, performance and reliability of this product are negatively impacted.-Please be aware that this product should not come into contact with any other parts while incorporating in your lightingapparatus or your other products.-Please be aware that careful handling is required after the attachment of lead wires to prevent the application of any loadto the connections.-For more information, please refer to application note "Instruction Manual(COB LED Package)".7-2. Countermeasure against static electricity-Handling of this product needs countermeasures against static electricity because this is a semiconductor product.-Please take adequate measures to prevent any static electricity being produced such as the wearing of a wristband oranti-static gloves when handling this product.-Every manufacturing facility in regard to the product (plant, equipment, machine, carrier machine and conveyance unit)should be connected to ground and please avoid the product to be electric-charged.-ESD sensitivity of this product is over 1,000V (HBM, based on JEITA ED-4701/304).-After assembling the LEDs into your final product(s), it is recommended to check whether the assembled LEDs aredamaged by static electricity (electrical leak phenomenon) or not.-It is easy to find static damaged LED dies by a light-on test with the minimum current value.7-3. Caution of product assembly-Regarding this product assembling on the heat sink, it is recommended to use M3 screw.It might be good for screw tightening on the heat sink to do temporary tightening and final tightening.In addition, please don’t press with excess stress on the product.-The condition of the product assembling on the heat sink and the control of screw tightening torque needs to be optimized according to the specification of the heat sink.-Roughness, unevenness and burr of surface negatively impact thermal bonding between the product and heat sink andincrease heat thermal resistance between them.Confidence of thermally and mechanical coupling between the product and heat sink are confirmed by checkingthe mounting surface and measuring the case temperature of the product.-In order to reduce the thermal resistance at assembly, it might be good to use TIM (Thermal Interface Material) on whole contact surface of the product.In case of using thermal grease for the TIM, it might be good to apply uniformly on the contact surface of the product.In case of using thermal sheet for the TIM, it might be good to make sure that the product is NOT strained by stress when the screws are tightened for assembly.-For more information, please refer to application note "Instruction Manual(COB LED Package)".7-4. Thermal Design-The thermal design to draw heat away from the LED junction is most critical parameter for an LED illumination system. High operating temperatures at the LED junction adversely affect the performance of LED’s light output and lifetime. Therefore the LED junction temperature should not exceed the absolute maximum rating in LED illumination system. -The LED junction temperature while operation of LED illumination system depends upon thermal resistance of internal LED package (Rj-c), outer thermal resistances of LED package, power loss and ambient temperature. Please take both of the thermal design specifications and ambient temperature conditions into consideration for the setting of driving conditions.-For more information, please refer to application note "Thermal Management", "Instruction Manual(COB LED Package)".7-5. Driving Current-A constant current is recommended as an applying driving current to this product.In the case of constant voltage driving, please connect current-limiting resistor to each products in series and control the driving current to keep under the absolute maximum rating forward current value.-Electrical transient might apply excess voltage, excess current and reverse voltage to the product(s).They also affect negative impact on the product(s) therefore please make sure that no excess voltage, no excess current and no reverse voltage is applied to the product(s) when the LED driver is turn-on and/or turn-off.-For more information, please refer to application note "Driving", "Instruction Manual(COB LED Package)".7-6. Lighting at a minimum current value-A minimum current value of lighting of all dice is 15mA.When a minimum current is applied, LED dice may look different in their brightness due to the individual difference of the LED element, and it is not a failed product.7-7. Electrical Safety-This product is designed and produced according to IEC 62031:2008(IEC 62031:2008 LED modules for general lighting. Safety specification)-Dielectric voltage withstand test has been conducted on this product to see any failure after applyingvoltage between active pads and aluminum section of the product, and to pass at least 500V.-Considering conformity assessment for IEC62031:2008, almost all items of the specification depend uponyour final product of LED illumination system.Therefore, please confirm with your final product for electrical safety of your product.As well, the products comply with the criteria of IEC62031:2008 as single LED package.- A minimum current value of lighting of all dice is 90 mA. When a minimum current is applied, LED dice may look different in their brightness due tothe individual difference of the LED element, and it is not a failed product.7-8. Recommended soldering Condition (This product is not adaptable to reflow process.) -For manual solderingPlease use lead-free soldering.Soldering shall be implemented using a soldering bit at a temperature lower than 350C, and shall befinished within 3.5 seconds for one land.No external force shall be applied to resin part while soldering is implemented.Next process of soldering should be carried out after the product has return to ambient temperature.Contacts number of soldering bit should be within twice for each terminal.* Citizen Electronics cannot guarantee if usage exceeds these recommended conditions.Please use it after sufficient verification is carried out on your own risk if absolutely necessary.-For more information, please refer to application note "Instruction Manual(COB LED Package)".7-9. Eye Safety-The International Electrical Commission (IEC) published in 2006 IEC 62471”2006 Photobiological safety of lamps and lamp systems ” which includes LEDs within its scope.When sorting single LEDs according to IEC 62471, almost all white LEDs can be classifiedas belonging to either Exempt Group (no hazard) or Risk Group 1 (low risk).-However, Optical characteristics of LEDs such as radiant flux, spectrum and light distribution are factorsthat affect the risk group determination of the LED, and especially a high-power LED, that emits lightcontaining blue wavelengths,might have properties equivalent to those of Risk Group 2 (moderate risk).-Great care should be taken when directly viewing an LED that is driven at high current, has multipleuses as a module or when focusing the light with optical instruments, as these actions might greatlyincrease the hazard to your eyes.-It is recommended to regard the evaluation of stand-alone LED packages as a referenceand to evaluate your final product.7-10. This product is not designed for usage under the following conditions.If the product might be used under the following conditions, you shall evaluate its effect and appropriate them. In places where the product might:-directly and indirectly get wet due to rain and/or at place with the fear.-be damage by seawater and/or at place with the fear-be exposed to corrosive gas (such as Cl2, H2S, NH3, SOx, NOx and so on) and/or at place with the fear.-be exposed to dust, fluid or oil and/or at place with the fear.Precautions with regard to product use(1) This document is provided for reference purposes only so that CITIZEN ELECTRONICS' products are used as intended. CITIZEN ELECTRONICS neither makes warranties or representations with respect to the accuracy or completeness of the information contained in this document nor grants any license to any intellectual property rights or any other rights of CITIZEN ELECTRONICS or any third party with respect to the information in this document. (2) All information included in this document such as product data, diagrams, charts, is current as of the date this document is issued.Such information, however, is subject to change without any prior notice.Before purchasing or using any CITIZEN ELECTRONICS' products listed in this document, please confirm the latest product information with a CITIZEN ELECTRONICS' sales office, and formal specifications must be exchanged and signed by both parties prior to mass production.(3) CITIZEN ELECTRONICS has used reasonable care in compiling the information included in this document, but CITIZEN ELECTRONICS assumes no liability whatsoever for any damages incurred as a result of errors or omissions in the information included in this document.(4) Absent a written signed agreement, except as provided in the relevant terms and conditions of sale for product, and to the maximum extent allowable by law, CITIZEN ELECTRONICS assumes no liability whatsoever, including without limitation, indirect, consequential, special, or incidental damages or loss, including without limitation, loss of profits, loss of opportunities, business interruption and loss of data, and disclaims any and all express or implied warranties and conditions related to sale, use of product, or information, including warranties or conditions of merchantability, fitness fora particular purpose, accuracy of information, or no infringement.(5) Though CITIZEN ELECTRONICS works continually to improve products' quality and reliability, products can malfunction or fail. Customers are responsible for complying with safety standards and for providing adequate designs and safeguards to minimize risk and avoid situations in which a malfunction or failure of a product could cause loss of human life, bodily injury or damage to property, including data loss or corruption.In addition, customers are also responsible for determining the appropriateness of use of any information contained in this document such as application cases not only with evaluating by their own but also by the entire system.CITIZEN ELECTRONICS assumes no liability for customers' product design or applications.(6) Please contact CITIZEN ELECTRONICS' sales office if you have any questions regarding the information contained in this document, or if you have any other inquiries.CITIZEN Micro HumanTech is a registered trademark of Citizen Holding Co., Japan.CITILED is a registered trademark of CITIZEN ELECTRONICS CO., LTD. Japanand are trademarks or registered trademarks of CITIZEN HOLDINGS CO., LTD. JAPAN.is a trademark or a registered trademark of CITIZEN ELECTRONICS CO., LTD. JAPAN.。
LED热隔离封装技术及对光电性能的改善(精)
LED 热隔离封装技术及对光电性能的改善在传统的白光LED 封装结构中，荧光粉直接涂覆于芯片上面，工作时，芯片释放的热量直接加载在荧光粉上面，导致了荧光粉的温升，使得荧光粉在高温下转化效率降低。
而在荧光粉与芯片之间引入一层低导热的热隔离层能够有效的阻止芯片的热量直接加载到荧光粉上，降低了荧光粉层温度，使得白光LED 在大电流注入下都能保持较高的流明效率。
除了芯片释放的热量之外，涂覆的荧光粉受蓝光激发时，因荧光粉的转化效率尚未达到100%，另外由于散射等其它损耗的存在，荧光粉颗粒本身也会有少量的热量释放，容易形成局域热量累积，为此当荧光粉材料转化效率较低时，还需为荧光粉提供散热通道，防止荧光粉颗粒局域热的生成。
下面通过传统荧光粉涂覆方式和热隔离封装方式两组实验对比了解两种结构中芯片和荧光粉的热相互作用。
1. LED 芯片对荧光粉的加热为了评价LED 芯片对荧光粉热性能方面的影响，我们制作了两组白光LED 封装结构，一组采用传统的荧光粉涂覆方式，另一组采用热隔离的荧光粉涂覆方式，图1是该热隔离封装结构的剖面制样图。
图1 传统白光LED 横截面图示(a荧光粉热隔离封装结构(b，h=1mm[14-16]. 荧光粉热隔离封装结构是通过荧光粉覆膜的方式实现的。
荧光粉覆膜技术是我们提出的一种新型荧光粉涂覆方法，即根据出光要求设计好荧光粉膜层的结构，在专用模具内完成荧光粉膜层的成型，剥离后，将荧光粉膜层转移到LED 芯片上方，同时LED 芯片和荧光粉膜层中间还有一层低导热系数的硅胶层。
为了表明两种封装结构热性能上的差别，我们比较了两种封装结构表面的温度分布图。
图2是两种封装结构在200、350和500mA 直流驱动下表面IR Camera测得温度径向分布。
在200 mA驱动电流下时，热隔离封装结构比传统封装方式中心温度低1.6℃。
在350mA 和500mA 注入电流下时，荧光粉层的温差分别达到了8.5℃和16.8℃，并且在500mA 注入电流下时，传统结构荧光粉的表层最高温度已经达到130.2℃。