Conformal phosphor coating using capillary microchannel for controlling color deviation of phosphor-converted white light-emitting diodes

We demonstrated a conformal phosphor coating method for phosphor-converted white light-emitting diodes (LEDs) using capillary microchannel formed by a fixture. The mixture of the phosphor particles and the silicone spontaneously flows in capillary microchannel and was pinned at the edge of the fixture due to the surface tension effect. The present coating method was applied to different packaging types with both the conventional chip and the vertical injection chip. Experimental results show this method can efficiently improve the angular color uniformity (ACU). Compared with those samples packaged by conventional dispensing coating, angular color correlated temperature (CCT) deviation of the test samples by the present method can reduce from 1500K to 200K for the average CCT 5200K from -90° to +90 view angles, and reduce from 5000K to 1000K for the average CCT 9150K. Additionally, this method can prevent the packaging non-consistency that the average CCT varies from package to package due to the deviation of phosphor-silicone mixture volume. In the experiments, even when the phosphor-silicone mixture volume varies from 0.3 µl to 0.5 µl, the deviation of the average CCT is less than 80K.