荧光粉沉降导致的白光LED色温漂移及其解决办法

发布时间：2019-02-09 14:04

【摘要】：白光LED具有高效节能、寿命长、绿色环保等优点,在显示和照明领域有着广泛的应用。蓝光LED芯片与黄色荧光粉组合是最主要的白光LED实现形式。在白光LED封装工艺中的点胶和烘烤环节,荧光粉都会产生明显的沉降,而导致白光LED色温严重漂移、产品光色性能不一致等问题。为研究此现象,本文设计出白光LED光谱实时观测系统,并对实际SMD型白光LED封装结构中的荧光粉沉降状态进行横截面观察,解释了荧光粉沉降对白光LED色温的影响原因。在此基础上,本文尝试了几种色温漂移问题的解决方法,最终发现在荧光粉胶中掺入轻密度的散射颗粒,可以有效解决荧光粉沉降导致的色温漂移问题。1)本文设计并制作出白光LED光谱实时观测系统,研究了荧光粉沉降现象与白光LED色温的关系。结果表明：荧光粉的沉降会使得白光LED光谱中的蓝光强度下降,黄光强度升高,导致色温下降。本文认为,荧光粉沉降会导致其在封装胶中的分布变化,在荧光粉沉降聚集的过程中,荧光粉层的透射率下降,反射率上升,对光的背散射／反射程度不断上升,蓝光在支架反射层与荧光粉层之间多次反射激发Ce产生更多黄光,蓝黄转换率升高,从而色温逐渐降低。2)研究表明,荧光粉中掺入适量Si02散射颗粒或用细粒径荧光粉能在一定程度上减轻沉降导致的色温漂移现象,但是都会对白光LED的初始亮度产生较大影响;本文尝试在荧光胶中加入轻密度、粒径适宜的空心玻璃微珠,微珠在封装胶中会逐渐上浮,其对光的背散射／反射程度逐渐下降,与荧光粉沉降对光散射的影响正好相反。空心微珠的掺入能够基本消除沉降过程的色温变化,且对初始亮度影响很小3)本文使用透明硅树脂镶嵌的方法,制作出SMD型白光LED的横截面切片,研究了荧光粉在实际SMD型白光LED中的沉降现象。研究发现,由于蓝光LED芯片具有一定高度,部分荧光粉会沉降到LED芯片出光表面的下方,导致侧向漏光,从而使蓝光出射增多,色温升高。4)本文对SMD型白光LED做了预垫平处理,并在荧光粉中掺入精选空心玻璃微珠,缓解了荧光粉沉降过程导致的色温漂移现象。实际SMD封装试验表明,该工艺应用效果良好。
[Abstract]:White LED is widely used in display and lighting field because of its advantages of high efficiency and energy saving, long life and green environment. The combination of blue LED chip and yellow phosphor is the most important white light LED realization form. In the process of dispensing and baking in white LED packaging process, the phosphors will produce obvious deposition, which will lead to the serious drift of white LED color temperature and the inconsistent photochromic properties of the products. In order to study this phenomenon, a real-time measurement system of white LED spectrum is designed, and the deposition state of phosphors in SMD type white LED packaging structure is observed cross-section, which explains the influence of phosphor deposition on the color temperature of white LED. On this basis, several methods to solve the problem of color temperature drift are tried, and it is found that the scattering particles with light density are mixed in the phosphor gel. It can effectively solve the problem of color temperature drift caused by phosphor deposition. 1) the real-time measurement system of white LED spectrum is designed and fabricated. The relationship between the phenomenon of phosphor deposition and the color temperature of white LED is studied. The results show that the deposition of phosphors will decrease the intensity of blue light in white LED spectrum and increase the intensity of yellow light, which will lead to the decrease of color temperature. In this paper, it is concluded that the deposition of phosphors will lead to the change of their distribution in the encapsulated adhesive. During the deposition and aggregation of the phosphors, the transmittance of the phosphors decreases, the reflectivity increases, and the backscattering / reflectance of the phosphors increases. Blue light produced more yellow light and blue yellow conversion rate by multiple reflection between the reflector layer and phosphor layer, and the color temperature decreased gradually. 2) The addition of appropriate amount of Si02 scattering particles or the use of fine particle size phosphors can reduce the color temperature drift caused by deposition to a certain extent, but all of them have a great effect on the initial brightness of white LED. In this paper, we try to add hollow glass beads with light density and suitable diameter to fluorescent adhesive, which will float up gradually in encapsulation adhesive, and the backscattering / reflection degree of fluorescent beads will decrease gradually, which is contrary to the effect of phosphor deposition on light scattering. The incorporation of hollow beads can basically eliminate the color temperature change in the sedimentation process, and has little effect on the initial brightness. 3) in this paper, the cross section sections of SMD type white light LED are made by using transparent silicone resin mosaic method. The deposition of phosphors in SMD type white LED was studied. It is found that due to the height of the blue LED chip, some phosphors will sink below the surface of the LED chip, resulting in lateral leakage of light, thus increasing the blue emission. The color temperature is raised. 4) the SMD type white light LED is pre-padded and the fine hollow glass beads are added into the phosphor to alleviate the phenomenon of color temperature drift caused by the deposition process of the phosphor. The practical SMD package test shows that the process has good application effect.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN104.3;TN312.8;TQ422

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