Utilization of Silicone Microspheres: Improving Color Uniformity and Reducing the Amount of Phosphor Used in White Light-Emitting Diodes

The aim of this paper is to improve the color temperature uniformity per view angle of a white light-emitting diode (LED) by utilizing silicone microspheres (SMSs). The view angle is 97.5 ° when using silicone encapsulant alone, and it increases to 108 ° with the use of 0.1 wt% SMSs. With 0.3 wt% SMSs added to a silicone encapsulant that contains 7 wt% phosphor, the color temperature deviation improves from 1300 to 167 K. A design of experiments is used to quantitatively analyze the effect of SMSs on the reduction of the amount of phosphor required, and actual samples are fabricated based on the results to compare their characteristics. To fabricate a white LED with a correlated color temperature (CCT) of 5500 K, 9.5 wt% phosphor is used when using phosphor only, whereas 6.7 wt% phosphor is used after adding 2.3 wt% SMSs. When a combination of phosphor and SMSs is used to fabricate an LED with the same color temperature, the luminous flux decreases by 4.6%, the CCT deviation improves from 502 to 106 K, and the amount of phosphor needed by is reduced to 30%.