the initial luminous

 (2) package failure

Package failure is improper packaging design or production processes lead to device failure. The  LED Lighting china epoxy material used in packaging, in the course of degradation problem occurs, resulting in reduced life of LED. Such degradation problems include: light transmittance, refractive index, expansion coefficient, hardness, water permeability, air permeability, filler performance, especially in the light transmittance is most important. Studies have shown that the shorter the wavelength, the more serious deterioration of light transmittance, but the green  Ceiling Light  wavelengths above (i.e., greater than 560nm), this effect is not serious. Lumileds2003 years has published over power white LED devices and the device lifetime φ5 white experimental curve, 19kh, the use of silicone resin encapsulated power devices, the initial luminous flux can be maintained for 80% of the epoxy encapsulated contrast curve indicates the 6kh, the luminous flux maintenance rate is 50%. Experimental results show that the luminous efficiency of the chip under the same circumstances, the epoxy resin was close to the chip becomes yellow, then to brown. This apparent degradation processes, is mainly caused by the light and temperature epoxy light transmittance caused by deterioration. Meanwhile, in yellow phosphor excited by the blue LED white light, the package will affect its browning lens reflex, and makes enough to excite the blue glow yellow phosphor, making efficiency and spectral distribution of the light changes.