Development process of phosphor coating with screen printing for white LED packaging

An improved screen printing technology for the coating of a cerium-doped yttrium aluminum garnet (YAG): Ce³⁺ yellow phosphor on blue light emitting diodes (LEDs) is presented. A metal plate with apertures matches with wire-bonded LED chips on a substrate. Silicone with YAG: Ce³⁺ phosphor is pushed into the apertures by a squeegee blade and then the metal plate is removed by release agent after curing. The thickness of phosphor layer is controlled by the thickness of metal mask and the phosphor concentration on luminescence emission and chromaticity are investigated. In order to obtain uniform coating and an optimized geometry of the phosphor layer on the surface of LED chip, this approach is optimized to manufacture and provide a wide range of color temperature.