A test method for quickly evaluating the lifespan of LED lighting products

Luminous flux decay is a key indicator for determining LED lifespan. The US Energy Star (ES) defines the end of life of an LED lighting product as a lumen maintenance factor falling below 70%. Energy Star proposes measuring lumen maintenance for 6,000 hours at 25°C ± 1°C to infer the lifespan of LED lighting products (the lumen maintenance factor must be no less than 91.8% after 6,000 hours). Given the rapid advancements in LED lighting technology and product upgrades, a 6,000-hour (or longer) testing period is still too long to meet the demands of the rapidly evolving industry.

　　Developing a rapid reliability test method for evaluating the lifespan of LED lighting products has become a crucial issue for the industry. To address this challenge, the National Joint Innovation Laboratory for Semiconductor Lighting (UNIL) conducted two years of research and developed the "CSA020 Accelerated Luminous Flux Output Degradation Test Method for LED Lighting Products."

　　On August 9, 2013, DOE reliability research expert Fan Xuejun gave an in-depth and systematic explanation of the principles of the accelerated luminous flux output degradation test method in this far-reaching research result, the verified test data, and the significance of the release of this standard.

　　Building on the test methods of US ENERGY STAR, LM-79, LM-80H, and TM-21, CSA020 proposes a new accelerated degradation test method based on the theoretical foundations of the "e-exponential model," the "Arrhenius acceleration model," and the "Poisson distribution." This method further shortens the test time by increasing the ambient temperature during testing (to raise the LED junction temperature). Under the recommended maximum test temperature of 55°C, data from less than 2000 hours can be used to replace the 6000 hours of room temperature data required by the ES method. This method not only significantly shortens the traditional 6000-hour test time to less than 2000 hours, but also maintains the quality and accuracy of the ES method. Fan Xuejun stated that the feasibility and rationality of the accelerated degradation test method adopted in this standard have been demonstrated not only theoretically but also verified using actual test data from LED lighting fixtures.

　　CSA020 has been discussed within the National Semiconductor Lighting Engineering Research and Development and Industry Alliance's more than 400 member organizations, soliciting feedback from a wide range of industry players. It has been voted on and approved by over 80 formal members, officially released, and is gradually being promoted and applied by domestic testing institutions. As a test method for rapidly determining the lifespan of LED lighting products, it will better support the implementation of national financial subsidy policies and significantly boost the R&D and industrial development of LED lighting products.