Packaging Light Extraction Efficiency Enhancement Of LED Array Packaging

Light emitting diodes(LEDs)are widely used in general lighting,advertising,emergency lighting and other fields due to their high lumen efficiency and other advantages such as energy saving as well as environmental protection.The multi chips packaging(LED array packaging)is the developing trend of LED packaging owing to highe luminous flux compared with single chip LED.However,the multi chips packaging is not perfect at present,and its main technical problem is that the packaging light extraction efficiency is still much lower than single chip LED's,and too much bad angular CCT uniformity.We focuse on how to improve the efficiency of LED array packaging and modify angular CCT uniformity:Light propagation in blue chip and phosphor layer was simulated based on the mathod of Monte Carlo,referring to different packaging and lacation of phosphor layer for multi-chips LED.And the influence of encapsulation efficiency on different distrances between chip and phosphor layer was analyzed.The result shows that the encapsulation efficiency of conformal coating firstly rises,then drops with the diameter increasing.The flat remote coating has higher efficiency compared with others.The maximum encapsulation efficiency reaches up to 77.183% for the flat remote coating while the gap of chips is set as 0.2mm and the distancebetween chip and phosphor layer is 0.28 mm.The influence of the curvature radius of phosphor layer on encapsulation efficiency is small.The effect of the surface microstructure of encapsulated colloids on the encapsulation efficiency of array LED is systematically studied.Compared with the plane of the multi chips LED package,the two micro structure can significantly improve the packaging light extraction efficiency,and change the distribution of light intensity angle can be adjusted by the parameters of half intensity angle at 90° ~ 160° range.In the range of simulation data,the multi chip LED with concave cone structure has higher stability than the concave spherical structure for the light efficiency of encapsulation.The LED packaging structure with cavity is designed.Compared with the traditional packaging structure,it can significantly improve the correlation color temperature uniformity,and the difference is reduced from 1534 k to 359 k.The evaluation factor is adopted to evaluate optical performance of LED,and the cavity structure with the center angle of 53°is used.The evaluation factor is 4.2 times of the traditional packaging structure,and better optical performance can be obtained.The relative color temperature uniformity is not affected by the concentration of phosphor,and the low color temperature region of 4000 K and 5000 K can also reduce the correlation color temperature deviation value.In addition,the cavity structure is also applicable to multi chips LED.