A fully integrated novel Wafer-Level LED package (WL2P) technology for extremely low-cost solid state lighting devices

Abstract

Reduction of cost has become the most important challenge for solid state lighting. We proposed a novel Wafer-Level LED Packaging (WL2P) technology, which enables both extremely low cost and small size for future solid state lighting. Where a conventional package needs individual assembly steps, resulting in high fabrication cost, we carried out from growth of the GaN layer, over formation of Inter Layer Dielectric (ILD), wiring for solder pad to printing the phosphor layer on a whole wafer in our WL2P. Thus, for the first time a fully integrated wafer-level process was successfully applied to light emitting diode (LED) devices. It was clearly demonstrated that our WL2P has an excellent thermal resistance as low as 24.2K/W in the 0.6×0.3mm size prototype structure because of the direct connection of Cu wiring to the light emitting layer and a maximum injection power density was as high as 1157W/cm2 in a difference of 50°C between junction temperature and ambient temperature on the aluminum based printed wiring board (PCB)