| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 103 === With the development of science and technology, computer displays become an indispensable peripheral equipment due to popularization of personal computers. Traditional CRT displays have been gradually replaced by LCD, and associated backlights shift from CCFL to LED as well. While consumers keep pursuing larger screen displays with thinner thickness, how to eliminate high temperatures and to ensure longer life cycles along with proper heat dissipation constitute an important topic of research.
As the benchmark, this study measures the temperature distributions on the LED back plate and the chips on the PCB in an LCD. A numerical model corresponding to the LCD is developed and the thermal and flow fields are solved by using a commercial code FloTHERM. The errors for the temperature between the experimental data and the numerical results are generally less than 10%. Thus the numerical model can be regarded as appropriate with acceptable accuracy. Waste heat accumulates on one side because the backlight of the LCD for experiment is edge-lighting and the heat generated by chips accumulates in chip packages. To remedy the above problems, heat transfer enhancement via conduction is proposed by performing thermal analysis and evaluating cooling improvements.
It is indicated from simulation that heat conduction is the primary heat dissipation mode in the LCD. However, for better understanding the influence of venting and natural convection inside the LCD, effects of the openings of the plastic housing and the inner metal lid are also discussed. Effects of the increase in openings turn out to be minor. Photocoupler, inverter, LDO, LCD control IC and the EEPROM are the objects chosen for observation and heat dissipation improvements. The temperatures of components are lowered by changing the PCB substrate materials, chip packaging materials, and installing heat sinks on the surface of a chip. Changing the back plate materials and coating a flexible graphite sheet on the back plate can decrease heat accumulation on one side of the LCD. A combination of various improvements can resolve the above-mentioned problems and decrease the operating temperatures of the components effectively.
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