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Thermal and flow simulation and cooling improvements of edge-lighting LED displays
|Authors: ||Lee, Kuan-Yeh|
|Contributors: ||NTOU:Department of Mechanical and Mechatronic Engineering|
|Issue Date: ||2017-05-24T08:23:31Z
|Abstract: ||隨著科技的發展，個人電腦普及化之後，電腦顯示器成為不可或缺的周邊產品，傳統CRT顯示器逐漸被液晶顯示器所取代，背光源也從冷陰極管轉換為LED。在人們追求大尺寸螢幕、輕薄機身厚度的需求下，如何使系統元件不受高溫影響以及增加產品使用壽命，散熱為必須面對的課題。 本文量測自然對流下之液晶顯示器內背光模組背板與PCB上晶片元件溫度，並使用數值模擬軟體FloTHERM對實驗機體建構模型，求解該情形下的系統溫度分布。量測值與軟體模擬值差距在10%以內時，表示所建構之模型具有一定的準確度。由於實驗機體為側光式LED背光源液晶顯示器，熱量集中於單側；晶片元件產生的熱容易累積於封裝體內，吾人對於模型進行散熱分析與改良，增加熱傳導性以解決上述問題。 由模擬分析可以得知，熱傳導為液晶顯示器中主要散熱方式，但也探討自然對流下，塑膠外殼與金屬內蓋開孔對於液晶顯示器散熱的影響，結果顯示增加開孔之影響不明顯。吾人選擇光電耦合元件、逆變器、低壓差線性穩壓器、LCD控制IC與指令暫存器作為觀察對象，藉由改變PCB基板材質、晶片封裝材料、裝置散熱鰭片等方式降低晶片元件溫度。對於熱量集中單側問題，則以更換背光模組背板材料與塗佈柔性石墨片於背板上，使熱量平均分布。最後採用綜合改良模型能有效改善上述問題，降低整體操作溫度。|
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.
|Appears in Collections:||[機械與機電工程學系] 博碩士論文|
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