高分子微流道熱壓成型模擬與實驗驗證之研究

Simulation and Experimental Verification of Polymer Hot Embossed Micro Channels

林明俊(Ming-Chung Lin)

指導教授 ： 陳夏宗

中原大學/工學院/機械工程研究所/博士(2009年)

https://doi.org/10.6840/CYCU.2009.00723

摘要

本論文以熱壓成型製程方式針對具微流道結構塑膠產品的轉寫特性做出有系統之研究，同時並運用有限元素法的理論來模擬分析高分子材料在熱壓過程中的成型行為。研究中，針對PMMA板材進行相關的材料實驗以獲得其流變特性，進而建立材料資料庫；而後以建立之模型進行PMMA微流道之熱壓模擬並與實驗結果做一驗證。模擬時採用可同時考慮作用力及溫度效應的非線性黏彈性有限元素軟體LS-DYNA，有效地模擬出在熱壓過程中高分子材料的流動情形以及建立以壓印溫度及壓印作用力為參數的成型視窗。而在實驗中，則利用紫外光深刻模造法(UV-LIGA)製程以矽基SU-8光阻搭配微電鑄來得到用於生物晶片用途之微特徵流體平台之鎳鈷（Ni-Co）基模仁，其中微流道陣列之尺寸約30μm深、50μm寬且流道間距為250μm、750μm與1250μm。然後選用1 mm厚之PMMA板材作為微熱壓成型之成型材料，針對不同成型條件對微流道包括寬度與深度之轉寫正確性，以3D雷射顯微鏡作一量測、分析與探討。
研究結果發現，熱壓印溫度與壓印作用力為影響具微細特徵熱壓元件成型正確性之兩個重要關鍵性參數。當壓印溫度135℃時，微流道壓印轉寫之正確性隨作用力之增大而增加且達到一飽和值。當壓印作用力固定為18kN，微流道壓印轉寫之正確性雖隨溫度之增高而增加，但溫度超過140℃以上時，卻受徑向壓力梯度與高溫時塑料流動性佳的影響，成型圖案中拘束力較低的微流道圖案處之轉寫正確性隨溫度增加反而會降低。同時研究結果證實，此有限元素模組能準確的模擬PMMA以熱壓製程成型微流道結構時的行為。從模擬分析結果亦得到壓印作用力隨流道深寬比增加而增加，各區塊之壓印作用力隨流道數目增加而增加，其壓印作用力增加的主要原因在於流道深寬比愈大與流道數目的增加進而提升向下壓印時的阻力與融膠充填流動的拘束力。
本研究除了探討高分子熱壓製程且歸納出其關鍵參數的影響特性外，也建立了橡膠態高分子的材料特性蒐集實驗方式及有限元素應用於微流道熱壓印行為的模式，相關研究成果將可運用於其他工作溫度高於玻璃轉移溫度的高分子材料與製程。

關鍵字

轉寫正確性 ； 非線性黏彈性 ； 玻璃轉移溫度 ； 熱壓成型 ； 有限元素法

並列摘要

This thesis used the hot embossing process to systematically make up the replication characteristics of molded parts with micro-channels, and also adopted the finite element method (FEM) to analyze the molding behaviors of polymer PMMA. During the research procedures, a series of material property experiments are performed to determine the rheological characteristics of PMMA. The finite element material database is built using material properties from experiments. Subsequently, a simulation model of PMMA hot embossed micro-channels is constructed and verified experimentally. The proposed simulation model is used to predict the applied embossing forces in various temperatures on the products. The nonlinear viscoelastic material model which depends on working pressure and temperature incorporated into FEM code LS-DYNA, and successfully simulated the flow situation of PMMA and the optimal molding window taking applied force and embossing temperature as parameters in hot embossing process. In the experiment, hot embossing is applied to micro-featured fluidic platform used for Bio-Chip test. UV-LIGA like processes are used to prepare silicon-based SU-8 photoresist followed by electroforming for making Ni-Co based stamp. The micro feature in the stamp consists of micro-channel array of 30μm in depth, 50μm in width and 250μm, 750μm, 1250μm, receptively, in pitch size. A PMMA film of 1 mm thickness was used as a hot embossing substrate. Effect of various molding conditions on the replication accuracy of micro-features is investigated. The width and depth of micro-channels are measured and analyzed.
From the results, it was found that applied force and embossing temperature are the two key parameters affecting molding accuracy significantly. When embossing temperature is 135℃, the accuracies of the imprint replication increased with the applied embossing force until the associated dimensions reached saturated values. When the applied embossing force is 18kN, it can be seen that the accuracies of the imprint replication increased gradually with embossing temperature initially, but its accuracies decreases when the embossing temperature is higher than 140℃. This can be attributed to the radial gradient of compression stress and higher temperature result in the polymer can flow easily in the location of lower constrained force regions. Meanwhile, the results verify the FEM module that can accurately simulate the deformation behaviors of micro-channels structure in hot embossing process, it also indicated that applied force increased with the depth/width ratio, and the number of micro-channels in every simulation block. The reasons result from impressing obstruction and constrained forces of melt in filling mold
This study besides sums up influence of key parameters in hot embossing process for the fabrication of micro-channels within a polymer substrate, the experimental methods for collecting the material characteristics of semi-molten polymers and the finite element material model established in this study also can be applied in any processes involving working temperatures exceeding glass transition temperature.

並列關鍵字

Replication Accuracy ； Glass Transition Temperature ； Nonlinear Viscoelastic ； Hot Embossing ； Finite Element

參考文獻

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