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Single-component Overstressing Lift-time Test for SSL

Single-component Overstressing Lift-time Test for SSL. Delft Institute of Microsystems and Nanoelectronics. Bo Sun (sandysun23@gmail.com), Sau Koh (s.w.koh@tudelft.nl), G.Q. Zhang (g.q.zhang@tudelft.nl) Beijing Research Center, Delft University of Technology. Abstract

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Single-component Overstressing Lift-time Test for SSL

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  1. Single-component Overstressing Lift-time Test for SSL Delft Institute of Microsystems and Nanoelectronics Bo Sun (sandysun23@gmail.com), Sau Koh (s.w.koh@tudelft.nl),G.Q. Zhang (g.q.zhang@tudelft.nl) Beijing Research Center, Delft University of Technology Abstract The single-component overstressing lift-time test for SSL system, which applying accelerated stresses only to electrolytic capacitors in LED drivers, while investigating the entire SSL system’s response. During this accelerated lift-time test, the capacitor connects with the other driver parts by a pair of low resistant wire, making it could be placed into an environment chamber which applying heat, moisture and other accelerated stresses while the whole system is working in rated status. Meanwhile, the real-time processing equipment can measure LEDs’ input current ripple and capacitor’s pin temperature, which are the most critical indicators for predicating the system’s life-time. For evaluating LEDs’ performance during capacitor degradation, it is also need to measure lumen flux, luminous efficiency, input power, power factor and colors temperature. By analysis of all these output data, the relationship between SSL system’s outputs, which represent its lift-time, and each accelerated stress through electrolytic capacitor can be established, and thus the lift-time of a SSL system can be predicted base on these relationships. • State of the Art • Current Life-time test of SSL system takes very long time, an accelerated test is needed. • Several failure mechanisms works simultaneously in conventional accelerated test. Life-time is hard to predicted. • the electrolytic capacitor used at output end is weakest link in LED driver whose degradation one of primary failure reasons of SSL system. • Objectives • Developing an single component accelerated life test for LED Drivers as a part of methodology of SSL system reliability. • Main Failures • Electrolytic Capacitors Degradation • ESC drops to zero (Short) • ESR goes to infinite (Open) • LED Array Damaged • Wire Bonding broken (Open) • LED Degradation • Lumens depreciation SimulationResult Electrolytic Capacitors Degradation LED Array Damaged • Design • Capacitors are isolated in environmental chamber which apply high temperature and humidity. • LED module is working in integrating sphere which can measure input mean current and voltage and LED’s Luminous parameters. • DAQs capacitors’ can measure pin temperature and current ripple. • Loss of wire is limited less than 2% TestResult Conclusions Power factor and efficiency are suitable indicators for distinguishing failure of a linear driver. In the first 800hrs’ testing, LEDs’ degradation is dominating and the driver still in normal and stable status.

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