多孔性堆疊薄膜界面破裂能量模擬方法之建立與驗證

Establishment and Verification of Interfacial Fracture Energy Simulation Methodology for Porous Stacked Thin Films

施睿綺(Ruei-Ci Shih)

指導教授 ： 李昌駿

國立清華大學/工學院/動力機械工程學系/碩士(2020年)

摘要

有鑒於多孔性低介電材料之具低界面黏著性的特徵，本研究聚焦於相異材料間界面黏著力之估算方法的建立。在實驗部分方面，首先規劃一系列實驗，將石墨烯導電油墨塗布於PI基板，量測PI基板與石墨烯導電油墨之黏著性，並探討對PI基板進行電漿表面處理是否能增加其與石墨烯導電油墨之黏著性。其中，利用水滴接觸角實驗量測PI基板親疏水性的變化；利用XPS分析PI基板表面分子組態的變化；利用拉拔實驗與剪切實驗量測其界面黏著性。最後，藉由彎曲實驗觀察其脫層現象，並與有限元素模擬之結果進行比對與驗證。
另一方面，在界面黏著性分析部分，則是利用有限元素模擬建立四點彎曲實驗之模型，並在所關注之薄膜接合界面埋入界面裂縫與孔洞，利用J積分理論計算界面裂縫尖端之能量釋放率。針對J積分模擬分析之可行性，則進行收斂性分析以獲得J積分路徑規劃與網格大小之選擇準則。此外，本研究亦探討界面孔洞的尺寸、孔洞與裂縫尖端的距離等設計參數對於裂縫尖端能量釋放率的影響。進一步地，利用實驗設計方法決定影響能量釋放率之因子影響程度與充分作用之關係。最後，利用蒙地卡羅方法探討多孔性材料其孔隙率與孔洞分佈情況對於界面黏著性的影響。
研究結果指出藉由PI基板表面進行電漿表面處理能夠增加其與石墨烯導電油墨之黏著性。其機制歸因於PI基板表面之含氧官能基比例的增加。另一方面，針對界面孔洞與裂縫之分析，研究結果顯示若裂縫尖端附近具有孔洞存在，將會造成裂縫尖端產生較大之能量釋放率；且當孔洞距離愈靠近裂縫尖端，亦或孔洞尺寸較大時，引致之裂縫尖端能量釋放率則愈高。此外，多孔性材料之孔隙率增加亦會造成材料結構剛性降低，產生類似應力緩衝層的效應，予以舒緩裂縫尖端之應力集中現象，降低界面破裂能量。

關鍵字

電漿表面處理 ； 石墨烯導電油墨 ； 多孔性材料 ； 低介電材料 ； 界面黏著性 ； 能量釋放率 ； 有限元素法 ； 破壞力學 ； J積分

並列摘要

In view of the low interfacial adhesion characteristics of porous low-dielectric materials, this research focuses on the establishment of estimated methodology for the interfacial adhesion between dissimilar materials. In the experimental part, the graphene conductive ink is coated on the PI substrate to measure the adhesion between the concerned stacked films. A systematic arrangement of experimental split is implemented to discuss whether the plasma surface treatment on the PI substrate can enhance the interfacial adhesion or not. The test with regard to contact angle of water drop is utilized to judge the surface of PI substrate is either hydrophilicity or hydrophobicity. In addition, a change in the molecular configuration of PI surface is analyzed by XPS analysis. Furthermore, both the pull-off and shearing tests are performed to measure the critical interfacial adhesion. Finally, the delamination phenomenon is observed and validated through the use of bending tests and compared with the results of finite element simulation.
On the other hand, in order to develop the simulated methodology with regarding to cracking energy estimation of concerned interface having porous geometry features, the vehicle of four-point bending model is constructed to perform and to validate the proposed simulated approach. It is noticed that an interfacial crack and vacancy are simultaneously embedded in the bonded interface of dissimilar materials. To quantify the interfacial energy release rate of crack tip, the J-integral approach combined the convergence analysis of numerical calculation is performed to acquire the selection criteria of J-integral path and the suitable element size around the cracked tip. In addition, this research also discusses the influences of designed parameters, composed of the vacancy size along the concerned interface hole and the distance between the vacancy and the crack tip, on the variation of energy release rate of the crack tip. In addition, design of experiment approach is considered to find the influenced significance and interaction of design factors for the above-mentioned energy release rate. Finally, the Monte Carlo method is presented to investigate the effects of the porosity and void distribution for porous film materials on the interfacial adhesion.
The analytic results indicate that the plasma surface treatment of PI substrate surface can increase its adhesion to the graphene conductive ink. This mechanism is attributed to the increase in the proportion of oxygen-containing functional groups on the PI surface. On the other hand, the results regarding fractured analysis of concerned interfacial crack having vacancies show that a larger cracking energy is induced when a vacancy is close to the crack tip. In addition, the occurrence of that vacancy is closer to the crack tip or the vacancy size becomes larger would like to introduce a higher energy release rate. Furthermore, It is found that an increase in porosity of the porous material would deteriorate the structural rigidity itself and provide a capability similar to the stress buffer layer. In other words, the stress concentration at the crack tip and the interfacial fracture energy are simultaneously relieved and reduced.

並列關鍵字

Plasma Surface Treatment ； Graphene Conductive Ink ； Porous Material ； Low Dielectric Material ； Interfacial Adhesion ； Energy Release Rate ； Finite Element Method ； Fracture Mechanics ； J-integral Approach

參考文獻

[1] G. E. Moore, ‘‘Cramming More Components onto Integrated Circuits,” Electronics, Vol. 38, pp. 114-117, 1965.

[2] G. E. Moore, ‘‘Progress in Digital Integrated Electronics,” Electron Devices Meeting, Vol. 21, pp. 11-13, 1975.

[3] B. D. Hatton, K. Landskron, W. J. Hunks, M.R. Bennett, D. Shukaris, D. D. Perovic, and G. A. Ozin, ‘‘Materials Chemistry for Low-K Materials,” Materials Today, Vol. 9, No. 3, pp. 22-31, 2006.

[4] D. Shamiryan, T. Abell, F. Iacopi, and K. Maex, ‘‘Low-k Dielectric Materials,” Materials Today, Vol. 7, No. 1, pp. 34–39, 2004.

[5] J. Im, P. H. Townsend, J. Curphy, C. Karas, and E. O. Shaffer II, ‘‘Mechanical Properties of Cured SiLK Low-K Dielectric Films,” Metallization of Polymers, Vol. 2, pp. 53-60, 2002.