A Study On Phosphor Coating Structure And Processes For White LED

Due to the advantages in environmental friendliness, energy saving, long lifetime and so on, white light-emitting diodes(WLEDs) emerges as the next generation of solid state lighting(SSL) technology. Currently, phosphor converted WLEDs(pc-WLEDs) which typically realized by combining the blue LED chip and yellow YAG:Ce is widely used for their simplicity in construction and applicability for mass production. One of the key techniques in fabrication progress for pc-WLEDs is the phosphor coating method, because the quality(the thickness, shape and content) of phosphor layer are crucial factors that determine the quality of WLEDs. There was a mismatch problem between the phosphor layer pattern and the angular intensity distribution of blue light emitted from LED chip for traditional dispensing coating and conformal coating, which are regarded as two common techniques on the market, as a result, decreased the spatial color homogeneity(SCH).Based on the original technique of self-adaptive phosphor coating, we intensivly studied the self-adaptive remote phosphor coating for pc-WLEDs, applied the self-adaptive remote phosphor coating to the package of LED filament lamp and the wafer level of high-power LED and actively particpated in the work of industrilizing the self-adaptive phosphor coating technique.Through studied the experiment of the technique of self-adaptive remote phosphor coating for pc-WLEDs, it is suggested that luminous flux and luminous efficacy of self-adaptive remote phosphor structure increase by 3.23% and 4.49% at driving current of 350 mA, as compared to the conventional phosphor coating. Moreover, the self-adaptive remote phosphor coating enhanced the SCH for pc-WLEDs in contrast to conventional phosphor coating and conform phosphor coating. Lastly, the lifetime of self-adaptive phosphor coating for pc-WLEDs reached 21000 hours and achieved the demand of lifetime for WLEDs on the minaret from the experiment of aging-life test.The experimental results show that the self-adaptive phosphor coating for pc-WLEDs not only reached the commercial requirement of luminlus efficacy, but also solved the problem of the existing techonology in terms of the inconsistency of CCT between two sides and leakage blue light in application of LED filament lamp and not only owned good uniformity of phosphor layer pattern, but also reached yield of 96.49% in application of wafer level package of high-power LED.In the industrialization progress of self-adaptive phosphor coating for pc-WLEDs, the content of ADC and phosphor were studied and optimized and then decided the content of ADC and phosphor were 0.03%-0.04% and 20%-21% respectively considering the redundancy. Then studied the consistency of correlated color temperature(CCT) of experimental data which there models of 5002、5151and 3003 were experimented. The research presented that the data of CCT are consisented with a normal distribution and the pre-coated silicone better than those without pre-coated silicone in terms of the consistency of CCT and passing rate. Particularly, in terms of CCT, the passing rate of 10% is 88.97% and 81.63% for the type of 5002-A and 5002-B, the passing rate of 5% is 85.6% and 86.9% for the type of 5151 and 3003.