Phosphor-converted white light-emitting diodes (pc-white LEDs) have attracted considerable attention as a new generation light source since the first commercial GaN chip was invented in 1990s. A pc-white LED can be regarded as a sophisticated system including a number of components made of a variety of materials. An understanding of the behavior of its component parts is helpful to gain a comprehensive insight of the failure of the pc-white LED itself. For this reason, issues related to materials and reliabilities of the LED key components such as LED chip, phosphor, encapsulant, lead frame, and interface are discussed in this chapter.

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.