鎳微柱電鍍受鍍浴黏度與電阻率之影響; Effect of bath viscosity and electrical resistivity on the morphology of nickel micro pillar from localized electrochemical deposition

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Title:	鎳微柱電鍍受鍍浴黏度與電阻率之影響;Effect of bath viscosity and electrical resistivity on the morphology of nickel micro pillar from localized electrochemical deposition
Authors:	陳譽升;Yu-Sheng Chen
Contributors:	機械工程研究所
Keywords:	成核;活化能;黏度;電阻率;膽鹼基離子液體;局部電化學沈積;Localized electrochemical deposition (LECD);ionic liquid;electrical resistivity;viscosity;activation energy;nucleation
Date:	2011-08-01
Issue Date:	2012-01-05 12:33:10 (UTC+8)
Abstract:	本研究主要藉微陽極導引電鍍法，分別在氯化鎳 (含0.35 M~1 M 鎳離子)，不同液溫(323 K~353 K)的水溶液鍍浴及膽鹼基離子液體(由氯化膽鹼及乙二醇所混合調配而成) 鍍浴兩種系統中製備鎳金屬微柱，並以活化能觀點來探討此兩種鍍浴的表現差異。接著，在定電位-1.00 V 的微電鍍下，所測得的電流-時間關係，搭配成核理論方程式，可用來檢討、比對兩種鍍浴系統之析鍍物成核與成長行為，探討溶液特性對微陽極導引電鍍過程中鎳金屬微柱表面形貌之影響。以定電位微電鍍法所量測之電流-時間曲線顯示: 在水溶液鍍浴系統的成核行為屬於瞬時成核模式;而在膽鹼基離子液體鍍浴中的成核行為則屬於漸進成核模式。在兩種鍍浴系統所呈現之不同成核方式與鍍浴之電阻率及黏度有密切關係。溶液電阻率、黏度會隨浴溫提高而下降，也會隨浴中氯化鎳濃度而表現出不同特性。依據在兩種鍍浴中溶液電阻率、黏度及總活化能(ESUM＝Eρ+Eη)等的估計發現: 膽鹼基離子鍍浴之溶液電阻率及黏度活化能均遠高於水溶液之鍍浴系統。不論在任何鍍浴中，溶液之黏度活化能均高於電阻率活化能，此結果暗示: 溶液黏度對鎳金屬微柱微電鍍行為的影響遠大於溶液電阻率。膽鹼基離子液體的高黏度及高電阻率，升高了微柱成長的能量障礙，導致鎳金屬析鍍物沈積行為的不連續，進而使得微柱呈現瘤狀堆積的形貌。 Localized electrochemical deposition (LECD) was conducted by microanode-guided electroplating (MAGE) in two different bath systems containing the same concentration of nickel chloride (in the range from 0.35 M to 1.00 M nickel ions) to investigate the bath effect on the surface morphology of the nickel micro pillars. One of the baths is the ordinary aqueous solution and the other is an ionic liquid prepared by mixing choline chloride with ethylene glycol. The temperature of the baths was controlled in the range from 323 K to 353 K. Different electrochemical behavior arisen from different baths could be realized on the viewpoint of activation energy in the nickel electrochemical deposition. A plot of current density versus time for LECD performed at 1.0 V was helpful to correlated to theoretical background to illustrate their different behaviors. The current measured in the aqueous bath reveals a typical profile correlated to instantaneous nucleation; however, the current measured in the ionic liquid system depicts a characteristic behavior of progressive nucleation. Electrochemical deposition determined by different nucleation modes in different baths could be realized on the experimental parameters (such as electrical resistivity and viscosity) characterized by the baths. Both electrical resistivity and viscosity decreases with increasing bath temperatures. The electrochemical behavior depended upon the concentration of NiCl2 in the baths. The electrical resistivity and viscosity were determined in the systems, The activation energy ascribed to electrical resistivity (Eρ) and viscosity (Eη) in different baths could be estimated. In comparison with the magnitude of electrical resistivity, viscosity in the bath and overall activation energy (i.e., Esum = Eρ + Eη) contributed to electrical resistivity and viscosity, we found that they are all higher in the system of ionic liquid bath as compared with the aqueous system. Moreover, activation energy ascribed to viscosity is much higher than that ascribed to electrical resistivity regardless the bath. This fact implies that the activation energy ascribed to viscosity plays more important role than to electrical resistivity. Higher barrier activation energy in the system of ionic liquid bath leads to retard the nucleation. As a result, progressive nucleation dominates the deposition and it grows gradually to nodular form distributed non-uniformly. In contrast, least activation energy ascribed to viscosity plays only a tiny contribution in the aqueous bath, tiny barrier in activation energy leads to instantaneous nucleation. Consequent growth of a film dispersed with tiny crystals results in uniform smooth morphology.
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