Fabrication of Phosphor Pillar Based on Electrohy-drodynamic for High Angular Color Uniformity of White Light-emitting Diodes

Advanced phosphor coating techniques are urgently required to enhance the angular color uniformity (ACU) for packaging white light-emitting diode (LED). In this letter, wo proposed a method base on electrohydrodynamic (EHD) to fabricating phosphor gel pillar. In the method, the electric field was applied around phosphor gel to induce and adjust the nomal stress on the air-liquid interface.After being dropped onto the LED chip and being controlled by the interface stress, the phosphor gel could be tailored into cone and contacted with the lens, meanwhile heating the sample at 120°C and maintained for 1 hour. Finally, the phosphor gel pillar was obtained and ACU performances were tested. The experimental results show that the samples with phosphor gel pillar achieve much smaller correlated color temperature deviation (<;400K at about 5000K, <;800K at about 5000K) than the traditional spherical cap structure.