An improved electrophoretic deposition method for wafer level white pc-LED array packaging

Abstract

Combining the blue light-emitting diodes (LEDs) with the yellow phosphors, as called phosphors-converted white light-emitting diodes (pc-WLEDs), is an approach widely used for white LEDs manufacturing. The investigation of an improved electrophoretic deposition (EPD) method of conformal phosphor coating for pc-WLEDs packaging is presented in this paper. The antimony tin oxide (ATO) nanoparticles were used to coat surface of LED chips array to achieve an evenly distributed transparent conductive layer as electrode (i.e., cathode for EPD process) by the spray technique. A kind of dispersant was added into the suspension of prepared phosphor particles to improve the stability. The experimental measurement reveals that a sort of compact uniform distribution of the phosphor layer surrounding the LED chips' surface was realized with this newly developed EPD method. And the standard deviation of correlated color temperature (CCT) and luminous efficiency are 256.03 K and 3.06 lm/W, respectively. The prototype of phosphor coating on a multchip array scale demonstrates that a Wafer Level Chip Scale Packaging (WLCSP) for white pc-LEDs can be achieved with the improved EPD method in this work.