薄型均溫板的毛細結構的量測、提升與熱傳性能的預測

The Measurement, Improvement, and Performance Prediction of Capillary Structure for a Thin Vapor Chamber

莊博盛(Po-Sheng Chuang)

指導教授 ： 朱錦洲

共同指導教授 ： 張建成

國立臺灣大學/工學院/應用力學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702450

摘要

近年的手機設計朝向輕薄方向邁進，且 IC 晶片的處理性能也進一步的提高， 若沒有適時將廢熱移除，手機將產生熱點 (Hot spot) 造成區域溫度過高，除手機效能降低外，也會增添電池過熱的安全疑慮。為有效移除廢熱，大多數電子產品傾 向使用熱板作為導熱媒介，目前為符合手機設計空間，熱板的總厚度需進一步減少，面臨熱管性能無法提升的困境，故本研究將著重於量測毛細結構性能並進一 步提升輕薄型熱板性能做為最終目標。
藉熱板最大熱傳量理論分析，薄型熱板最大熱傳量受控於毛細限制，其中可提升性能之因子為毛細結構性能指標 ( Kw/reff )，與滲透度 (permeability)、有效孔徑(effictive pore radius) 及材質潤濕性有關。毛細結構設計方面，本研究使用張建成 教授之理論設計出不同銅網毛細結構，銅網尺寸 54 ∗ 104 ∗ 0.1 (mm3)，藉毛細力實驗 (Capillary rise) 量測毛細高度 (Capillary height) 與毛細重量 (Capillary mass)，量化毛細結構性能指標，其中蒸發端 15 ∗ 15 (mm2)，冷凝端 30 ∗ 50 (mm2)，有效長度 77.5(mm)利用此配置預測最大熱傳量。
研究結果顯示當開口寬度在小於 1.80 mm 時，開口區域將含有工作流體，使毛細結構從單孔洞結構轉變成雙孔洞結構，其中開口有水_#4_1 的 Kw/reff 為 0.644(μm)，純銅網的 Kw/reff 為 0.305(μm)，提升 52% 的毛細性能; 預估最大熱傳量在開口有水 _#4_1 此組為 7.56(W)，純銅網預測最大熱傳量為 3.94(W)，保守估計可提升約30%。研究結果顯示開口結構能有效的提升毛細結構性能，因開口結構內能額外提供毛細力，並提高滲透度使工作流體的阻力變小，使整體性能提高。

關鍵字

薄型熱板 ； 雙孔洞毛細結構 ； 毛細力實驗 ； 毛細結構性能指標

並列摘要

Currently the overall thickness of a vapor chamber needs to be flattened to meet the design space of a mobile phone but the performance of a vapor chamber thus cannot be raised. This study puts an emphasis on measuring the performance of wick and determining to promote the performance of a thin vapor chamber.

From analyzing maximum heat transfer capacity of vapor chamber, the maximum heat transfer rate of a thin vapor chamber is controlled by the capillary limitation of ultra-thin vapor chamber. The factor which can enhance the capillary performance is related to permeability, effective pore radius and wettability. This study, with the help of Professor Chien-Cheng Cahng’s theory, designs different copper mesh wicks(54*104*0.1 mm3). By capillary rise, we can measure capillary height and capillary mass. The quantity index of wick is as follows. Evaporating section(15*15 mm2), Condensing section(30*50 mm2).

The study shows that when the width of groove is less than 1.80 mm, the groove area will contain working fluid, turning wick from biporous structure to mono-porous structure. Compared with Kw/reff of Copper_Mesh_#1_1(0.305 μm), Groove_with_water_#4_1(0.644 μm) can improve the capillary performance by 52%. Compared with maximum heat transfer capacity of Copper_Mesh_#1_1(3.94 W), Groove_with_water_#4_1 (7.56 W) can improve the capillary performance by 30%. This study appears that the structure of groove can effectively enhance the capillary performance since it can provide extra capillary force, as well as raise the permeability to reduce the working fluid resistance, and therefore better the overall performance.

並列關鍵字

Ultra-thin Vapor Chamber ； Bi-porous wick ； Capillary rise method

參考文獻

[4] R. Lucas. Rate of capillary ascension of liquids. Kolloid Z, 23(15):15–22, 1918.

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