Multilayer dispensing of remote phosphor for LED wafer level packaging with pre-formed silicone lens

Phosphor converted LED is commonly used as the white light source in solid state luminaires. Among the packaging processes involved, phosphor deposition is a critical step, which controls the overall optical performance of LEDs. There are several phosphor deposition methods, among which disperse dispensing and conformal coating methods are widely used. In these two methods, phosphor materials are applied directly on top of the LED chip. The phosphor materials are heated up by the LED chip during the operation. The behavior of phosphor materials highly depends on their temperature. The emission efficiency decreases as temperature increases. High phosphor temperature may also introduce reliability problems. The situation can be improved by adopting a remote phosphor method. Some high power LEDs packages utilize silicone lens to increase the light extraction efficiency. It is difficult to apply a remote phosphor layer on the convex surface using a regular dispensing process. In this paper, an innovative multilayer remote phosphor deposition method is proposed for the packages with silicone lens. Phosphor slurry was dispensed directly on the silicone lens with steps. The slurry flowed and spread on the dome, and stopped when it reached the edge of the step. The unique step feature stopped the phosphor slurry from overflowing. A package with multilayer remote phosphor layer was fabricated. The phosphor material in each layer was different. This method provides a simple and flexible platform for adopting different types of phosphor materials in one package, and hence to achieve the designed optical performance.