A methodology, based on accelerated degradation testing, is developed to predict the lifetime of remote phosphor plates used in solid-state lighting (SSL) applications. Both thermal stress and light intensity are used to accelerate degradation reaction in remote phosphor plates. A reliability model, based on the Eyring relationship, is also developed in which both acceleration factors (light intensity and temperature) are incorporated. Results show that the developed methodology leads to a significant decay of the luminous flux, correlated colour temperature (CCT) and chromatic properties of phosphor plates within a practically reasonable period of time. The combination of developed acceleration testing and a generalized Eyring equation-based reliability model is a very promising methodology which can be applied in the SSL industry.
A high accelerated stress testing (HAST) system is introduced to study the photo-thermal stability and reliability of remote phosphor plates, made from Bisphenol-A polycarbonate (BPA-PC) and YA G. Remote phosphor plates, combined with a blue-light LED source, are used to produce white light with a correlated colour temperature (CCT) of 4000 K. Tn this study, the remote phosphor BPA-PC samples of 3 mm thickness were photo-thermally aged at temperature range 80 to 120°C.The blue light is radiated on the sample with light intensity of 13200 W/m 2 • Thermal quenching of the YA G samples is also studied. It is shown that crystallographic structure of phosphor is stable during thermal ageing.
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