Electrical-thermal-luminous-chromatic model of phosphor-converted white light-emitting diodes

The drive of increased electrical currents to achieve high luminous output for phosphor-converted white light-emitting diodes (PW-LED) has led to a series of thermal problems. The light performance of PW-LED is affected by the heat generated by the two major sources in a package/module: chip(s) and phosphors. In this work, spectral shift and consequent color properties change due to the increased temperature during operation were studied by a group of experiments. An electrical-thermal-luminous-chromatic (E-T-L-C) model was then developed to predict the light performance with thermal management under in-situ temperature. The model was then validated by integrated analyses of common LED packages. Besides, the model can also be used to analyze the thermal performance and light quality due to thickness and particle density variation of phosphors. The proposed dynamic E-T-L-C model can definitely benefit the design of future HB LEDs for better light quality. (C) 2013 Elsevier Ltd. All rights reserved

A back-wafer contacted silicon-on-glass integrated bipolar process - Part I: The conflict electrical versus thermal isolation

A novel silicon-on-glass integrated bipolar technology is presented. The transfer to glass is performed by gluing and subsequent removal of the bulk silicon to a buried oxide layer. Low-ohmic collector contacts are processed on the back-wafer by implantation and dopant activation by excimer laser annealing. The improved electrical isolation with reduced collector–base capacitance, collector resistance and substrate capacitance, also provide an extremely good thermal isolation. The devices are electrothermally characterized in relationship to different heat-spreader designs by electrical measurement and nematic liquid crystal imaging. Accurate values of the temperature at thermal breakdown and thermal resistance are extracted from current-controlled Gummel plot measurements