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Article history: Received 21 August 2015 Received in revised form 29 December 2015 Accepted 30 December 2015 Available online xxxx A sharp rise in lumen degradation was observed for packaged high power LEDs during the initial period of operation under high humidity and temperature conditions, and the degradation reaches a peak value, followed by a(More)
A moisture- electrical - temperature (MET) test is proposed to evaluate the outdoor reliability of high power blue LEDs, with and without phosphor, and to understand the degradation physics of LEDs under the environment of combined humidity, temperature and electrical stresses. The blue LEDs with phosphor will be the high power white LEDs. Scanning acoustic(More)
A modified distributed Lagrange multiplier/fictitious domain method (DLM) that allows particles to undergo collisions is developed for particulate flows. In the earlier versions of the DLM method for Newtonian and viscoelastic liquids described in [1,2] the particle surfaces were restricted to be at least one and half times the velocity element size away(More)
High power LEDs are replacing the traditional lighting sources due its wide range of advantages. However, their reliability remain a concern due to the lack of understanding in terms of their failure mechanisms and related reliability studies, especially in outdoor applications. In this work, a comprehensive review on the study of humidity and high(More)
Flip chip technology has been widely adopted in modern power light-emitting diode (LED) fabrications and its output efficiency is closely related to the submount material properties. Here, we present the electrical, optical and thermal properties of flip chip light-emitting diodes mounted on transparent sapphire and borosilicate glass which have shown a(More)
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