【摘要】 发光二极管(light-emitting diode,LED)具有电光转换效率高、节能环保、体积小等优点,被誉为21世纪绿色照明光源.随着LED在越来越多的照明场合的应用推广和人们对于光源质量的要求的提高,LED出光品质越来越被重视.评价LED出光品质的指标主要有效率、空间颜色均匀性和显色指数,这些参数和LED封装密切相关.LED封装是将芯片和其他封装材料集成在一起形成最终的照明产品,起着机械保护、外部信号和电连接、散热和光学参数调控等关键性功能.本文从封装的角度,对LED的效率、空间颜色均匀性和显色指数的调控技术进行了系统阐述.具体到封装中的关键技术,主要包含以下3方面:(1)热设计.LED在工作过程中约有60%的输入电能被转化为热量,如果产生的热量不能及时有效地散到环境中,将会造成LED的温度急剧升高,导致LED的效率下降并带来可靠性问题.(2)光学设计.LED的光从芯片有源层中通过电子-空穴复合的方式产生后,在经过芯片、荧光粉、封装胶和透镜等材料后,由于散射和折射等作用,光的传播方向和路径会发生改变.此外由于吸收作用,部分的光被吸收并转换成热量.因此通过光学设计不仅可以调控LED光源能量分布,还可以减少光在封装材料中的吸收从而提高光效.(3)荧光粉涂覆.相比于多色发光LED芯片组合获得期望出光品质LED的封装形式,将单色或者多色荧光粉涂覆在单色LED芯片上的封装形式具有更强的相关色温可调性和工艺灵活性而被广泛应用于LED工业生产中.对于荧光粉结合芯片的白光LED封装形式,荧光粉涂覆起着调控空间颜色均匀性和显色指数的关键作用.更多还原

【Abstract】 Light-emitting diode(LED) is regarded as the green lighting source in 21 st century due to its advantages of high efficiency, energy saving, environmental protection and compact size, etc. With the popularization and application of LED in more and more lighting occasions and the improvement of people’s requirement for the quality of light source, more and more attention has been paid to the light quality of LED. The main indexes for evaluating the light quality of LED are the efficiency, angular color uniformity(ACU) and color rendering index(CRI), which are closely related to LED packaging. LED packaging is a process of assembling the chip and other packaging materials together to form the final lighting products, it plays a key role in mechanical protection, external signals and electrical connections, heat dissipation and light quality control. This paper makes a systematic exposition of the control technology of efficiency, ACU and CRI from the view of LED packaging, mainly involves three key packaging technologies: 1) thermal management.For LED products, about 60% of the input electrical power is converted to heat, therefore, the failure of the effectively heat dissipation would cause sharply increase of the temperature, which leads to the decrease of efficiency and induces reliability problems. 2) Optical design. The LED light is generate by the electron-hole recombination from the active layer of the chip, then it across the chip, phosphor layer, encapsulant layer, lens and other packaging materials. Due to scattering, refraction and absorption of the packaging materials,the light propagation direction and path would be changed, and part of the light is absorbed and converted into heat. Therefore,the optical design not only can control the LED light energy distribution, but also can reduce the light absorption in the packaging materials to improve the efficiency. 3) Phosphor coating. Compared to the multi-color LED chips packaging method, coating the monochromatic or polychromatic fluorescent powder on the LED chip to achieve white light is more popular and widely applied in the LED industrial due to its correlated color temperature(CCT) adjustability and process flexibility. For the phosphor-converted white LED, the phosphor coating plays a key role in deciding the ACU and CRI.更多还原