表面張力驅動之指向性微裝置批次自組裝技術

Uniquely Orienting Micro Device for Self-alignment in Surface Tension Driven Micro Self-assembly

林正(Lin,Cheng)

指導教授 ： 錢景常 ； 曾繁根

國立清華大學/原子科學院/工程與系統科學系/博士(2008年)

https://doi.org/10.6843/NTHU.2008.00084

摘要

近年來先進小型化及微流體技術，帶來在流體系統中數仟計微電子元件組裝創新方法，而傳統抓取與置放技術平台於處理微元件組合過程，對於相較講求大量、效率及精確的微組裝確實是遭遇到很大困難。因此，流體自我對位研究可提供快速、低成本及精密對位來處理數仟計微元件組裝技術。
本文研究方向係微尺度微流體自組裝過程細部描述，經由數值模擬檢驗不同參數對流體自我組裝過程機制影響，由於微部件與液體有強表面張力交互作用之特性，可利用商用數值流體力學軟體(CFD-ACE+)來處理流體-結構交互耦合問題能力。數值模式建立係包括微部件、液體、基板及懸浮流體，進一步模型建構及參數分析，針對微部件–基板與液體–基板之間介面不同高度及接觸角效應，探討對流體自我組裝過程造成對位精確度之影響；模擬結果顯示介於潤滑劑及固體表面有高親水角度、較低潤滑劑高度、較高表面張力係數及較高黏滯潤滑劑，均會增進在回復過程的對位能力。
在實驗方面，可分為兩個部分(1)方形微部件是由二氧化矽四吋晶圓，切割成尺寸大小從350×350×170 μm3至1000×1000×440 μm3，然後將微元件經由吸管直接到達在水下的基板；比較不同尺度大小微部件及兩種黏合劑（高分子或低溫焊錫）效應對流體自組裝影響，此參數基礎分析可提供完成最佳化自組裝技術，高分子或焊錫黏合力實驗結果在較大接合處分別為117±15 μN及510±50 μN，此實驗條件顯示有較高組裝良率可達到100%。(2) 針對指定方向對位有發展新穎的圖案設計，淚滴尖角60°內部有中空橢圓孔（兩種新穎圖案TDE-1及TDE-2），此形狀設計可縮短角度跨距和減少能量障礙，加強指向對準能力;新穎圖案設計可行性評估，可從實驗及表面能模型結果，提供作為定量及定性分析依據。實驗結果顯示TDE新穎圖案可精確90°旋轉對位和較高毛細力，高分子黏合力量測結果在TDE-2圖案為41.2 ±10 μN；流體自組裝使用低溫焊錫及輔助對位模板黏接微部件和基板，在水溶液環境中完成，對位誤差使用標準方差計算角度對位為0.9°及平移對位為15 μm，角度對位組裝良率可達100%。

關鍵字

流體自組裝 ； 微部件 ； 黏合劑 ； 計算流體力學 ； 流體-結構交互耦合 ； 指向對位 ； 自組裝單分子層 ； 能量障壁

並列摘要

Recent advances of miniaturization and microfluidics technologies bring novel ways of parallely assembling thousands of micron-scale electronic components in fluidic phase. Conventional pick-and-place technology platform in handling micron-scale components assembly processes encounters tremendous difficulties in terms of capacity, efficiency and accuracy. Hence, Fluidic Self-Assembly (FSA) approach provides an alternative means for fast, economic, and precise handling of thousands of micro-scale parts.
The present study is intended to delineate the detailed features of fluidic self-assembly process of micro-scale parts and examine the important variables which govern the mechanisms of fluidic self-assembly process by numerical simulations. In order to characterize the strong interactions between the micro-part and lubricant, commercial Computational Fluid Dynamics (CFD) software which can handle Fluid-Structure Interaction (FSI) problems is utilized to investigate the effects of lubricant height and contact angles of interfaces between micropart-substrate and lubricant-substrate on the accuracy of micropart’s self-alignment process. The computational model is based on first principle conservation equations and is constructed by the coupling of two- phase modeling using volume of fraction, solid structure modeling, and fluid-structure coupling. A matching experimental system is set up for the micropart of aspect ratio from 3:1 to 10:1 to validate the 2-D computational simulations. Simulations reveal that high degree of hydrophilicity between lubricant and solid surfaces is required for self-assembly restoring, and lower lubricant height, higher surface tension coefficient and higher viscosity enforce the re-alignment/restoring process. Characterization of the flowfield inside lubricant slug also indicates that the asymmetry of the vortices/stress distribution at both ends of the lubricant meniscus drives the micropart in an oscillation restoring process.
The micro parts fabricated from silicon-oxide wafers and ranging in size from 350×350×170 μm3 to 1000×1000×440 μm3, aligned and filled to designated sites in the substrate under water. The effects of micropart sizes and lubricants on the FSA processes are compared. This study provides a fundamental analysis for achieving and optimizing the self-alignment. The polymer or solder adhesion force of the square-patterned micropart immobilized at the larger binding sites were estimated to be 117±15 μN and 510±50 μN, respectively, resulting in higher assembly yield of up to 100% for these samples.
Another research is to develop a novel design of two-dimensional modified alignment mark of tear-drop/ elliptical hole with a tip angle of 60 (TDE-1 and TDE-2 pattern shapes) are adopted to improve the recovery angle and reduce the energy barrier to uni-directional micropart alignment. The results of the experimental and surface energy model are compared both qualitatively and quantitatively to examine the feasibility of the new design patterns. Experimental results reveal that the micropart of TDE patterns could be accurately aligned by rotation through 90°and higher capillary force. The acrylate adhesive force of the TDE-2 patterned micropart was estimated to be 41.2±10μN. Fluidic self-assembly (FSA) was performed carried out in an aqueous environment, using a low-temperature solder adhesive for part-substrate lubricant and aligned template-assisted assembly. The standard deviation of aligned angular orientation was 0.9°and that of lateral accuracy was 15 μm ; an assembly yield of 100% was achieved. Micropart self-alignment with a unique in-plane orientation is achieved by combining shape recognition and the adhesive capillary effect. This self-assembly technique could be used to produce a heterogeneous system for packaging, including LSI and MEMS.

並列關鍵字

Fluidic Self-Assembly(FSA) ； Micropart ； Lubricant ； Computational Fluid Dynamic(CFD) ； Fluid-Structure Interaction(FSI) ； Self-Assembled Monolayer(SAM) ； Uni-direction ； Energy barrier

參考文獻

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[77]. C. Lin, F. G. Tseng, and C. C. Chieng, “Low energy barrier and large recovery angle of fluidic self-assembly for microparts employing tear-drop shape alignment mark,” The 4th Asia-Pacific Conference on Transducers and Micro/Nano Technologies (APCOT 2008), Tainan, Taiwan, 2008.

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