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

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 fabricating white LEDs. The investigation on an advanced electrophoretic deposition (EPD) method of conformal phosphor coating for pc-WLEDs packaging is presented in this paper. With spray process, the antimony tin oxide (ATO) nanoparticles were applied to surface of LED array to achieve an evenly coated transparent conductive layer as electrode (i.e. cathode for EPD process). A particular surface-modifier was added to increase the electric double layer region of the prepared phosphor particles suspension. The experiment results show that a compact uniform distribution of phosphor coating layer surrounding the LED chip surfaces was realized with this newly developed EPD method. The prototype of phosphor coating in mult-chip arrays scale demonstrated that a Wafer Level Chip Scale Packaging (WLCSP) for white pc-LEDs can be achieved with the improved EPD method in this study.