Research On Technology Of Controlling The Optical Surface Morphology And The Applications In High Power LED Packaging

With the development and progress of technology,high power light-emitting diodes(LED)have been widely used in backlight display,indoor lighting,cars headlights and so on.However,the optical surface morphology reduces the optical performances of LED products in the current LED packaging process.The current high-quality LED products rely on expensive advanced packaging equipments which increase the cost of manufacture.The study of improving the optical performances of products is still limited to changing the design of module.These methods lead to low production efficiency,reducing reliability,complex process and package structure.Therefore,this paper starts innovatively from the regulating and controlling the optical surface morphology and studies on the theory of controlling the different media surface morphology and carry out experiments to master the relevant rules.Based on the research,it is applied in LED packaging process and enhancing the optical performances.The applications are carried out in three aspects which include microlens fabrication,phosphor coating process and realization of tunable correlated color temperature(CCT).The detailed contents and innovations are described as follows:(1)In order to enhance the light extraction efficiency(LEE)of COB modules,a new kind of packaging process is proposed.Through fabricating microlens structure with porous film and reducing the total reflection effect at the silicone gel surface,the improving of optical performance for COB is achieved.In the experiments,the different polystyrene porous films with average diameter of 6.72?m,12.64?m and 20.38?m are prepared by using different volume of the polymer solution.According to the mold method,the patterns on the different polystyrene porous film are transferred onto the silicone gel surface of COB module and the various microlens structures are observed.The experimental results show that the application of microlens structures can significantly enhance the LEE of COB.When the average diameter of structures becomes lager,the LEE is increased more obvious.The COB with microlens structures which average diameter is 20.38?m,the sample's LEE reaches 0.92 which is improved 19.48%than that of none structures samples.(2)Designed to improve the angular color uniformity(ACU)of the LED package module with the vertical chip,a stamp-printed phosphor coating process is proposed to change the morphology of phosphor gel surface and obtain different phosphor gel layers under the action of surface tension and additional pressure.In the experimnets,the samples with frustum,cube and inverted phosphor layers are obtained by using the different plates.And the different volumes of phosphor gel are used to fabricate the samples with various catenary phosphor layers.The experimental results show that the catenary phosphor layer with the inward width of 0.07mm is an optimal geometry for the module.The sample presents that the maximum CCT deviation is only 151K at the average CCT of 6300K.(3)Based on improving the ACU of the LED package module with the horizontal chip,a phosphor coating technique is proposed to adjust the morphology of the phosphor gel surface under the action of electric field.Aiming at the morphological changes of silicone gel surface by electric field,the related theory analysis and experiments are developed.Based on the electrohydrodynamics,the laws of regulating the silicone gel surface morphologies are masterd.According to the experiments,it is found that the higher voltage,longer distance between electrodes and the larger initial height of silicone gel lead to more obvious changes of surface morphology.In the experiment,the different phosphor gel pillars with the height of 1.53mm and 1.98mm are fabricated by adjusting the distance between the pair of electrodes.The experimental results show that the best ACU performance is presented by the structure with height of 1.53mm.The maximum correlation color temperatures deviations are only 388K,711K and 1802K when the average CCTs are 4901K,6911K and 9358K,respectively.Compared with the traditional spherical cap structure,the maximum CCT deviations are reduced 76.19%,68.09%and 46.13%,respectively.Finally,it is proved that the phosphor coating process can achieve great ACU of samples with different average CCT by using different concentrations of phpsphor gel.(4)For the sake of "smart" LED and realizing the real-time tunable CCT LED module,a new method is proposed by combination of phosphor-in-indium tin oxides glass(PiG)and adaptive liquid lens based on electrohydrodynamic(EHD)and surface tension.Under the action of different distances between the electrodes,the distances and the initial height of the silicone gel are important parameters for morphological changes.In order to combine the two ways to change the silicone gel surface morphologies,the pre-coated silicone gel is used to realise the continuous surface morphological changes.Under the action of two ways,the morphologies of adaptive liquid lens surface have been changed to different geometries such as frustum,catenary pillar,the two spherical caps and so on.The experimental results show that the average CCT of samples can be continuously adjusted from 1928K to 6460K through changing the distance.However,the average CCT of samples can be steeply adjusted from 4360K to 6452K through changing the voltage between the pair of electrodes.