0 Preface
In recent years, high-power LEDs have gradually become a research hotspot in the field due to their advantages of energy saving and environmental protection. With the rapid development of LED technology, how to improve the performance of LED lamps has become the focus of research. Performance evaluation of LED luminaires helps to improve luminaire performance. For example, increase the light output of the luminaire, increase the overheat protection function to improve reliability, and simplify the thermomechanical design. For this reason, the performance evaluation of high-power LED lamps is indispensable, and the traditional aging test is less time-consuming and the evaluation environment is higher, and the corresponding experimental research is less. As a commonly used aging test method, high temperature aging simulates the various factors involved in the actual use conditions of the luminaire, and carries out the process of strengthening the experiment under the condition of aging of the luminaire, simulating the working process of the luminaire, and examining its performance over time. The change. High-temperature aging increases the intensity of the experiment by increasing the operating temperature, which greatly shortens the test time. It can be used to understand the long-term aging of the product lamps through a short test.
Today's high-power white LEDs are mainly composed of high-power blue LEDs and phosphors. Therefore, research on high-power blue LED lamps can be used as an important reference for high-power white LED lamps. High-temperature aging of blue LED floodlights can comprehensively evaluate the performance of the fixtures, and is an important means to investigate the average trouble-free working time and failure rate of the lamps. In order to evaluate the performance of high-power blue LED lamps, this paper conducted high-temperature aging tests on two kinds of blue LED floodlights, measured the photoelectric parameters of the lamps, and analyzed their photoelectric properties to study their light decay.
1 Test principle and process
With the development of LED technology, the integration degree of LED lamps is getting higher and higher, the structure of LED lamps is more and more subtle, and the manufacturing process is more and more complicated, so latent defects are generated in the manufacturing process. For a good LED lighting product, not only requires higher performance indicators, but also has higher stability. The stability of LED luminaire products depends on the rationality of the design, the performance of the selected light source device, and the overall lamp manufacturing process of the luminaire. At present, high-temperature aging processes are widely used at home and abroad to screen LED lamps to improve their stability and reliability. The service life of power LEDs can reach 50 000 h. It takes 6 years to evaluate the life of a conventional life test method. For fast-developing LED technology, this method cannot meet the development speed of LEDs. At present, foreign manufacturers generally use the life test data of 10 000 h as the basis for evaluation, and speculate on the actual life of the LED. This time is obviously too long. According to the comparison of the experimental results of various power LEDs under different stresses, a practical accelerated life test method can be used to evaluate the long-term service life of power LEDs in a shorter time with fewer samples.
1.1 Principle and equipment for high temperature aging
In order to improve the reliability of the luminaire and prolong the trouble-free working time of the luminaire, the necessary assessment of its stability to ensure the excellent quality of the luminaire and the expected working time is the principle of high temperature aging. The purpose of "electric heating and aging" is to expose the hidden dangers in the production process of defects, welding and assembly of components on the PCB of the electrical control component as early as possible to ensure that the lamps can withstand the test of time. After aging, the electrical parameters are measured, and the components that reject the failure or the variable value are screened to eliminate the early failure of the luminaire as much as possible before normal use.
High-temperature aging equipment (aging room) simulates a high-temperature environment testing equipment, which is an important experimental equipment to improve the stability and reliability of the luminaire. It is an important production process for each manufacturer to improve the quality and competitiveness of the luminaire. The aging room is a professional equipment. The design of the specification and performance must meet the requirements of the luminaire test. It must also ensure the stability of its work. Therefore, it must be of high quality, safe and reliable. Using advanced and mature technology and equipment, the most stable and practical components and materials, the aging room is designed with high performance and price. The system can be operated at a lower cost and with less staffing.
1.2 Structure and performance of blue LED floodlights
High-power LED lamps are mainly composed of the following components: semiconductor light source devices, package substrates, drive power supplies and lamp heat dissipation structures.
1.2.1 Analysis of light source devices
The two LED luminaire chips use high-power LEDs produced by a certain company in the United States as the light source. According to the accelerated life test at 100 ° C and 1000 h, the 1 w blue LED accelerated life test has a light attenuation of 9% for 500 h. .
1.2.2 Analysis of package substrate
The power LED package substrate acts as a carrier for heat and air convection, and its thermal conductivity plays a decisive role in the heat dissipation of the LED. Choosing the right substrate has a significant impact on the heat dissipation and reliability of the LED. Power LED package substrate materials are required to have high electrical insulation, high stability, high thermal conductivity and thermal expansion coefficient, flatness and high strength matched to the chip.