The Reliability Research And The Thermal Characteristics Of Ligh-power LED For Lighting

The LED (Light Emitting Diode) is a kind of semiconductor luminescent device with the advantages of low operating voltage, low power consumption, high luminous efficiency, environment-friendly and long life time. It is considered as a new generation light source and becomes the research hotspot in recent years. With the light efficiency of LEDs generally passed beyond 1001m/W, the application of LEDs turned to general lighting. Such as LED street lamps, LED lamps, LED bulbs, and so on. However, there are some technical problems need to solve, such as secondary light distribution, drive and heat dissipation. In fact, heat dissipation is a serious problem for the LED lamps; it affects the light efficiency, operating voltage, color temperature, reliability and the lifetime of LED. Due to the luminous efficiency of LED and the temperature of the P-N junction, that the junction temperature rises luminous efficiency. Current luminous efficiency of only about 35%, the future even rise to 50% and still has 50% of the energy is converted into heat, which will cause the LED junction temperature rise. Therefore, so that there are three different research content:1)How to test the LED junction temperature.2) Junction temperature of the LED characteristics.3)In considering the LED devices work when the junction temperature rises unavoidable circumstances, how to measure the actual life of the LED. Therefore, this is the subject of this dissertation, namely, "lighting-class high-power LED thermal characteristics and reliability."First,1W and 3 W white LED experiment samples, current-accelerated stress, white LED current stress accelerated life test, finishing the test data, including the luminous flux, luminous efficiency, color temperature, peak wavelength, forwardthe voltage optical parameters with aging time, the analysis of the main factors to affect life white LED test; life expectancy projections, respectively, of the test sample of 1W and 3W, and a brief analysis of the errors introduced during the test as well as life expectancy projections.Secondly, the use of the radiator of the same material with the same thermal conductivity, temperature of accelerated stress, temperature impact test, a temperature of 100℃C,120℃ impact. The test results show that:the LED forward voltage decreases with increasing temperature decreases linearly, different materials LED down slope. LED light output is reduced with increasing temperature, a substantially linear relationship. LED peak wavelength red shift with increasing temperature, the LED color temperature rises with increasing temperature, and caused the reasons for these changes are analyzed theoretically.In the Second, the thesis of lighting-class LED failure analysis highlights the LED failure caused by the migration of the metal electrode failure caused by over (EOS), electrostatic damage caused by the failure, the phosphor degradation caused by the failure of the package and heatmaterial cause of LED failure. And high power LED lighting level in order to reduce the degradation of improvement method, such as to reduce the junction temperature, improve the welding quality, use more advanced packaging technology and phosphor.Finally, the combination of my work experience, to talk about the problem of high power LED lighting level in the application process prone plain, and to analyze and propose solutions.