The Reliability Study Of White LED Based On YAG Phosphors

As the latest generation of solid state light sources, light-emitting diodes(LED) has been widely used in display and illumination owning to long life-time, low power consumption, high brightness, low cost and environmental protection. LED is seems to break the existing bottleneck of incandescent and fluorescent lamps and becomes the mainstream lighting in the future. Reliability is the basis for a wide range of LED applications, and the study of reliability is the basis and premise to improve the reliability.Based on the analysis of mass abnormal products, the thesis summarized the failure mode and analyzed the failure mechanism of package reliability and usage reliability, studied the LED reliability with accelerated life test(ALT) with different factors such as current, temperature and humidity etc. The specific detail contents are:Starting from the principle, development, advantages and application of LED, the thesis introduced the basis theory of LED reliability, which including the basic concepts of reliability, test method of reliability, accelerated life testing and normal ALT model.The thesis proposed the basic concepts of package reliability according to the package process, and studied the process of the LED package influencing the reliability and analyzed the measures to improve the reliability respectively. At last a statistical model was established based on the statistics of package unreliability, which can improve the reliability of product in the future.The thesis proposed the usage reliability of LED, classified the LED failure modes into the chip failure, phosphor degradation and packaging material degradation by raw materials. At the same time, the paper proposed measures to improve the reliability of the LED according to study of failure modes and failure mechanisms.At last the influence of current, temperature, humidity and ultraviolet light on the LED life were studied by preparing LED and designing ALT. Errors were analyzed after calculated the life of the samples and had a brief analysis of the life during the lifetime projections.