Remote phosphor deposition on LED arrays with pre-encapsulated silicone lens

Abstract

Phosphor converted LED is one of the commonly used components 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 remote phosphor deposition method is proposed for the packages with silicone lens. Phosphor slurry is dispensed directly on the silicone lens specially designed with a step. It flows and spreads on the dome, and stops when it reaches the edge of the step. The unique step feature stops the phosphor slurry from overflowing. The thickness of the remote phosphor layer can be easily adjusted by changing the dispensing volume. This dispensing method increases the throughput and reduces the processing cost.