白光LED封装材料对其光衰影响的实验研究

Experimental Research on Influence of Packing Materials of White LED on Its Luminous Decay

为了确定不同封装材料对白光LED光衰等性能指标影响的程度,进行了不同材料支架、不同种类固晶胶,以及不同厂家荧光粉及配粉胶的对比试验。试验发现,使用铜支架比铁支架LED的光效高,在第8周时光衰比铁支架低10%;使用银浆固晶比用环氧树脂寿命长,但初始光通比环氧树脂低近1/3;不同厂家的荧光粉对白光LED光衰的影响程度不同;使用环氧树脂作为配粉胶比用硅胶寿命短,但初始光通量相对高出25%。分析认为,主要是由于不同固晶胶和支架使PN结至支架之间的热阻发生了变化,不同配粉胶在LED封装过程中烘烤温度不一样,以及荧光粉本身具有光衰特性导致了白光LED产生不同程度的光衰。因此,在进行白光LED的封装设计、制造过程中,应根据用户对初始光通量、光衰以及色温漂移等参量的重视程度综合考虑并选择相应的封装材料。

Some packing materials have been tested contrastively including different brackets, glues for fixing chips, fluorescent powder and glues for mixing fluorescent powder, in order to confirm their influence on luminous decay performance of white LED. It is found out from test that, the efficiency of white LED using copper brackets is higher than iron brackets, moreover, the light decay is lower about 10 %. The life of white LED using silver glues is longer than using epoxy resins, but initial luminous flux is much lower by 1/3. Different fluorescent powders have different influence on the luminous decay of white LED. The life of white LED using epoxy resins to mix fluorescent powder is shorter than silica gel, hut initial luminous flux is higher about 25 %. It can be concluded that, different glues for fixing chips and brackets make the thermal resistance from PN junction to bracket change, solidified temperature is distinct during packing when different glues for mixing fluorescent powder have been used, and fluorescent powders have the phenomenon of luminous decay, all of those affect the white LED life time. Therefore,the materials should be selected synthesizing many factors during designing and packing, based on the importance of initial luminous flux, light decay and drift of color temperature.