Optical characteristics and reliability evaluation of wafer level white LED package

In this paper, we describe optical characteristics and reliability of a novel wafer level white LED (light-emitting diode) package. In this package, re-distribution wiring layer and phosphor layer could be formed in a lump by wafer level process. As a result, ultrasmall size package that is almost same size as the chip could be attained. This approach results in drastic reduction in material and process cost. We determined the package structure from the results of the numerical analysis on the thermal cycle resistance of the package after reflow soldering. The sapphire substrate is removed by laser process and the GaN layer exists between phosphor layer and encapsulation resin. Applicative light extraction was achieved by control of GaN surface roughness. In addition, it was confirmed that the package had sufficient reliability in the thermal cycle test (TCT). Consequently, this low cost package could be applicable to LED components and also the cost of them is considered to drastically decrease.