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Yan B.,University of California at Irvine | You J.P.,NEPES LED | Tran N.T.,NEPES LED | He Y.,University of California at Irvine | Shi F.G.,University of California at Irvine
IEEE Transactions on Components and Packaging Technologies

In this paper, the influence of the die attach adhesive (DAA) layer on the thermal performance of high power light emitting diodes was first investigated by using finite element analysis, and some key results were verified by the experimental data. Effective thermal management of the studied light emitting diode package can be achieved by selecting a DAA material with a proper thermal conductivity and by manipulating the geometry parameters of the DAA layer, such as the DAA area, and the bond-line thickness. The significance of DAA thermal conductivity to heat dissipation was further demonstrated by an analysis of the bottleneck to heat transfer. © 2009 IEEE. Source

Yan B.,University of California at Irvine | Tran N.T.,NEPES LED | You J.-P.,NEPES LED | Shi F.G.,University of California at Irvine
IEEE Photonics Technology Letters

Thermal performance of phosphor-based white light-emitting diodes (LEDs) under an input current of 350 mA is investigated by finite-element simulation in which the thermal and optical interactions are considered. It is demonstrated that the temperature of the phosphor particles, regardless of phosphor placement, is always higher than the junction temperature. It is concluded that the junction temperature, which characterizes the thermal behavior of monotonic color LED emitters, cannot be used alone for characterizing the thermal behavior of white LED emitters. In fact, the phosphor temperature is critical in determining the lumen performance and reliability of white LED emitters. In addition, the phosphor temperature is effectively reduced by coating the phosphors directly on the chip and maintaining a relatively higher phosphor concentration (above 60 wt.%) in the phosphor-silicone mixture layer. © 2006 IEEE. Source

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