| Summary: | 碩士 === 明新科技大學 === 精密機電工程研究所 === 98 === The study aim at the heat transfer and thermal stress analysis of the micro packaging structure of high power Light Emitting Diode (LED) have been performed. The silicon substrate material of LED micro structure system the research method of design and analysis based on the finite element method. The research topic includes (1) heat transfer characteristics of the LED; (2) thermal stress results in the phenomenon of bending variation of the LED; and (3) thermal and structure method to be provided to solve the dilemma of LED heat dissipation.
The chip material for design and analysis is made of Gallium Nitride (GaN) which is the III-V semiconductor. The silicon substrate, etched holes in the bottom and filled with high conductivity of copper material, is constituted the packaging structure is made up by Micro-Electro-Mechanical System (MEMS) technology. The analysis result indicate that the temperature and thermal stress increase of the chip with the input power increase, but decrease with the design input the thermal conductivity and convection heat transfer coefficient. Furthermore, the research results also show that the choices of applicability of the LED chip adhesion layer and the problem of the uniform coefficient of thermal expansion of the Silicon package structure block will increase thermal stress deformation. In order to avoid structure failure, LED chip could be configured on the heat sink to enhance heat dissipation performance of LED packaging and reduce temperature of LED chip, and so as to increase the reliability and lift of the structure.
Compare with sapphire adhesion layer (1W), the Cu layer’s temperature decreased about 6.2% while SiC layer 6.4% because the thermal conductivities of these two materials are very similar to the temperature drops are very quite the same. When the applied power increases, the chip temperature and thermal stress will decrease as the convective coefficient increase and approach to a constant when the coefficient larger than some certain values. If the LED array mounted on the PCB board, it will help to heat transfer and thermal stress performance improvement, since LED array heat source distribution is intensive than the single LED, the temperature and thermal stress of the LED array will be higher than the single one. The assembly of the LED array with PCB and the heat sink will improve the cooling efficiency and the overall performance.
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