Investigation In Fabrication And Performance Of LED Phosphor Coating By Centrifugation

Based on centrifugal process,this investigation conducts the researches on phosphor coating model,key manufacturing parameters and LED packaging structure in white lightemitting diode(LED).The mathematical model and optical model of the coating during centrifugation are established thoroughly.Based on this model,the effect of centrifugation on a series of coatings' optical performance are studied,which include YAG phosphor coatings,YAG phosphor-nitride phosphor mixed coatings,and YAG phosphor-CdSe/ZnS QD mixed coatings,and the mechanism of LED consistency improved by centrifugation is revealed.The key centrifugal process parameters in the preparation of phosphor coatings are studied experimentally,which verifies the rationality of the model.Considering the characteristics of the centrifugation,a phosphor coating structure manufactured by bidirectional centrifugation method is proposed,which benefits the optical performance of LED.The main research contents include:1)Modeling method for centrifugal sedimentation of phosphorsBased on the movement model of a single phosphor particle in the silicone during the centrifugation and the interaction between the phosphors,the variation of the distribution of the phosphor particles during the centrifugation is simulated,by which the optimal correspondence between the input of the centrifugal process parameter and the output of the concentration gradient is established.Using the finite difference time domain method,the optical characters of the gradient concentration coating are calculated,and the optical performance of the device is simulated with Monte Carlo ray tracing method followingly.This model is applied to study the influence of the centrifugal process parameters on the optical performance of the devices and provides guidance for manufacturing of the phosphor coating.2)Effect of centrifugal process parameters on LED optical performanceBased on the proposed model,the influence of the key centrifugal process parameters,including centrifugal acceleration and centrifugation time,on the optical performance of a series of phosphor-coated LED is studied.The results show that the ratio of excitation light to blue light is reduced by centrifugation,and a reasonable parameter of centrifugation can improve the device consistency after settlement.3)Centrifugal-based LED phosphor coating preparation processFurthermore,the preparation process and the parameter of the phosphor coating for LED devices based on centrifugal process are given in detail,and the influence of centrifugal process on a series of phosphor coatings is studied.It is indicated that the variations of optical performance and consistency match basically with the simulation results.4)Fabricating LED phosphor coating structure based on bidirectional centrifugationTo solve the problem that the angular color uniformity(ACU)of the forward centrifuged LED is difficult to further improve,according to the characteristics of centrifugation,a bidirectional centrifugal process solution is proposed.Considering the existence of the overflow area in the backward centrifuged LED lens,which cannot directly improve ACU,a bidirectional centrifugal coating with pre-cured silicone in lens is proposed,and the effect of the pre-cured silicone content on light quality is systematically studied.Compared with the forward centrifugal LED,it is demonstrated that the ACU of the LED with a 12 mg mass of pre-cured silicone in the 6 lens can be increased by more than 45%.