Long-term degradation mechanisms of mid-power LEDs for lighting applications. Issue 9 (August 2015)

• Record Type: Journal Article
• Authors: Buffolo, M.; De Santi, C.; Meneghini, M.; Rigon, D.; Meneghesso, G.; Zanoni, E.
• Is Part Of: Microelectronics and reliability. Volume 55:Issue 9/10(2015)
• Page Start: 1754
• Page End: 1758
• Publication Date: 2015-08
• Subjects: Mid-power LED -- Reliability -- Accelerated aging -- Lighting devices -- General lighting; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2015.06.098
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: This paper reports the results of a reliability investigation performed on four different groups of commercially available mid-power white LEDs. In order to determine the robustness of this continuously growing class of lighting devices we arranged an experiment of accelerated aging: the four groups of LEDs (from different manufacturers) were submitted to a series of stress tests in environmental chambers with set-point temperatures ranging from 45 °C to 105 °C, in accordance to the IES LM-80-08 lumen maintenance measurement standard. The experimental data gathered all along the 4000 h of stress accumulated up to now suggest the presence of multiple degradation mechanisms that may limit the useful lifespan of the light-emitting diodes under test. In particular we observed the following phenomena: i) a decay of the luminous flux; ii) an increase in the reverse and forward leakage current; iii) the worsening of the chromatic properties of the emitted light; and iv) the presence of a thermally activated degradation mechanism. The results provide a first insight into the reliability of those widely used LEDs; the results on the temperature-dependence of the degradation kinetics can be used as a guideline for the thermal design of modern distributed-light lamps. Highlights: Reliability investigation performed on commercially available mid-power white LEDs Generalized decay of luminous flux for junction-temperatures above 120 °C Generation of defects within the active region of the devices Worsening in the optical properties of the package/phosphor system Presence of a thermally activated degradation mechanism