Study of ultraviolet assisted cure mechanism of the phosphor/silicone composites used in White LEDs

Abstract

Due to low power consumption, long lifetime and many other advantages, Light-emitting Diode (LED) has increased dramatically all over the world. Chip Scale Package (CSP) LED is a new LED package with small size, high current, and high reliability. For the CSP LED with smaller size and lower thermal resistance, phosphors and silicone are usually combined as the phosphors/silicone composite and prepared by using a high temperature cure process. However, for those CSPs which are not sufficiently cured, their reliability under a harsh environment (e.g. high temperatures and high humidity) will obviously decrease. In this study, the influence of temperature and ultraviolet light on the cure process of phosphor/silicone composites is studied and an optimal cure process is extracted accordingly. According to the cure experiment under different conditions, the results show that ultraviolet light and phosphor can promote the cure reaction of silicone. With the increase of ultraviolet light intensity and phosphor mass fraction, the cure rate of the silicone and phosphor/silicone composite is greatly increased as well.