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A good understanding of the optical and thermal properties of mid-power LEDs requires an accurate simulation of the light conversion process in the phosphor layer and a good description of the major materials properties. A ray-tracing model for the light conversion process is developed in LightTools® and the output is used as input for the thermal model in ANSYS®. The thermal resistances of the main resistors in the junction to case heat flow path are measured and implemented in the thermal model. The results of the optical and thermal simulations using key parameters are compared with the measured values.Depending on the effort used to calibrate the model, deviations of less than ten percent can be achieved. This is typically within the error margin of the experiments. The main source of error is most likely missing information on the precise optical die properties.Nomenclature

The absorption of mercury into glass and metal-oxide coated glass tubes is investigated with the aid of Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS), low-energy ion scattering, and thermal desorption mass spectroscopy. The absorption reaction of bare glass with activated mercury species is strongly reduced when the glass is covered with a thin oxide film. The concentration profile of the mercury measured in the films with the aid of RBS varied between a homogeneous distribution and a higher concentration of mercury close to the discharge side of the coating. XPS showed that the oxidation state of the mercury at the surface of the coatings was between that of metallic mercury and mercury(II) oxide. Thermal desorption mass spectroscopy showed that at least two different states of bound mercury were involved. The combination of the thermal desorption mass spectroscopy and XPS led to the conclusion that direct mercury-metal-oxide interactions contribute to the bonding of the mercury. © 2003 The Electrochemical Society. All rights reserved.

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