具開孔之電路板設計於自然對流下電子冷卻能力提昇之研究

Enhancement of Thermal Characteristics for Electronic Cooling under Natural Convection through Substrate with Apertures

曾永信(Yung-Shin Tseng)

指導教授 ： 白寶實 ； 洪祖全

國立清華大學/原子科學院/工程與系統科學系/博士(2007年)

https://doi.org/10.6843/NTHU.2007.00436

摘要

本研究藉由實驗與數值模擬方法進行電路板開孔之被動式散熱概念之可行性驗證，以期此構想能於實際產品之設計中提供散熱能力改善與成本降低之目的。透過初步的研究得知，此構想可以在自然對流中有效的改善電路板下表面之熱邊界層分佈，因此不需額外進行主動式散熱設計即可增強電子產品本身的散熱效果。進一步的探討更發現，電路板開孔之散熱能力可以透過研究所獲得的數個設計準則來加以強化；例如，控制電路板開孔位置之周長截斷率、增加開孔面積與周長以及利用表面Nu值輔助電路板開孔設計等。最後，研究更藉由外殼的流體導引孔以及非對稱配置等數種設計方式之結合，使得開孔構想除了能使原有的最佳熱阻獲得15%的改善以外，更可降低其參數限制與製程成本並提高產品之設計自由，而使得開孔構想的實用性得以提昇。另一方面，研究過程中發現熱輻射為一不可或缺之移熱機制，此一熱傳機制的忽略除了造成最高溫度的評估誤差之外。結果更顯示如幾何形狀、擺置方式以及流場條件等參數對於溫度的影響趨勢可能此而產生變化。不幸的是，此機制卻在大多數的電子散熱分析或是計算中被加以忽略。因此研究中更藉由合理的參數來建立電子產品之熱輻射重要性評估方法，以供設計者對電子散熱中熱輻射之重要性有定性的了解。

關鍵字

電子散熱 ； 被動式散熱 ； 電路板開孔 ； 熱輻射 ； 設計自由度

並列摘要

In this study, a CFD model has been developed to interpret and validate the experimental results originating from a concept of enhancing heat dissipation from a substrate with flow inducing openings. Through parametric study as a part of the preliminary research, the practicability and the influence of parameters of this previously unnoticed cooing concept has been discussed. Results indicate that the openings will have a destructive effect on the growth of the boundary layer occurring on the lower surface of the substrate; and hence improve the cooling ability of a configured module without using any additional active heat dissipation measures. More improvement investigations further indicate that the cooling ability of the opening can be augmented through the design rules such as a control of the opening rate to reduce the conduction resistance, an enhancement of net heat transfer ability through a distribution analysis of Nu numbers, etc. Finally, by combining a guide aperture on the shell board and unsymmetrical arrangement design, some adverse phenomena or effects (e.g., the limit of aperture ratio and an obstruct flow within the upper channel) have been obviously improves as found in this study. The concept of opening not only improves 15% in heat dissipation the best original design, but also eliminates some difficulties in finding an appropriate thermal solution such as the manufacturing cost and the design flexibility. Moreover, results show that thermal radiation is an important cooling mechanism as a part of electronic cooling modes, but it is usually overlooked by most researches with an incorrect judgment. A reasonable diagnosis method was also developed in order to verify the issues under investigation. This method would provide future designers with a qualitative understanding of the importance of thermal radiation.

並列關鍵字

Electronic Cooling ； Passive Cooling ； Substrate with Apertures ； Thermal Radiation ； Design Freedom

參考文獻

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