In the LED use, loss of photons generated in the radiative recombination emission outwards when produced, mainly in three aspects:

　　1, the chip internal structural defects and an absorbent material;

　　2, the photon emission interface reflection loss caused by the difference in the refractive index of;

　　3, and the total reflection loss due to the angle of incidence larger than the critical angle of total reflection caused.

　　Therefore, a lot of light can not be emitted to the outside from the chip. By the chip surface coated with a layer of relatively high refractive index of silica gel, and the air in between the chips, thus effectively reducing the loss of photons at the interface to improve the light extraction efficiency.

　　In addition, the role of silicone chip also includes mechanical protection, stress relief, and as a light guide structure, enhance heat dissipation, in order to reduce the chip junction temperature and improve LED performance. In order to improve the reliability of the LED package, silicone also has low moisture absorption, low stress, anti-aging properties.

　　The most commonly used include epoxy and silicone potting. Studies have shown that improved silica can effectively reduce the refractive index of the refractive index caused by a physical barrier photon losses and improve the external quantum efficiency, but silicone performance greatly affected by ambient temperature. As the temperature increases, thermal stress inside the silica increased, resulting in lowering the refractive index of silica gel, thus affecting the LED luminous efficiency and light intensity distribution. However, the overall performance was better than silicone epoxy resin, widely used in high-power LED package.