Study on Convective Flow Behaviors of Phosphor Particles During Curing Process of Silicone and the Influences on the Optical Performance of White LEDs

The correlated color temperature (CCT) variation of the phosphor-converted light-emitting diodes (LEDs) after curing is a common phenomenon. In the past, it was believed that the phenomenon was caused by the sedimentation of phosphor particles. However, not only sedimentation, but these particles can also flow with the natural convection of silicone because of nonuniform heating during curing. The convective flow of the phosphor particles during curing was studied in detail in this work. The CCT variation and phosphor particles flow in the LED device cup with different depths and wall inclination angles were studied. The results show that the CCT increases after curing when the depth of the device cup is shallow. The case is the opposite when the depth of the device cup is deep. The convective flow behaviors of the silicone were revealed in the simulation. The large-angle inclined wall can increase the silicone flow path length and inhibit the particles flow downward caused by the flow to a certain extent. It is envisioned that the findings will strengthen the understanding of the CCT variation phenomenon and guide the encapsulation structure design of LEDs for better color quality.