磷酸前處理對鋁箔特性及其電蝕行為之影響

Abstract

鋁質電解電容器在電路系統上的應用相當廣泛, 需求量亦大. 為朝 向小型化發展, 工業界在改進高壓用電解電容器設計時, 一般均朝擴大陽 極鋁箔表面積方向著手, 其中則以電蝕方法作擴面處理為研究重點之一. 鋁箔電蝕前之表面特性會影響電蝕之效果, 優良之前處理可以有效的改善 電容器之品質. 本研究主要以不同濃度之磷酸在尚未電蝕之鋁箔表面 進行前處理, 探討其特性改變及對後續電蝕行為的影響. 結果如下:1. 鋁 箔經磷酸前處理後, 表面有明顯侵蝕現象, 隨磷酸濃度升高, 侵蝕愈大. 而壓延線為優先侵蝕區域.2. 依XPS,ATR分析, 隨磷酸濃度增加, 磷酸吸 附現象明顯. 3. 本研究證實電蝕時電位過渡之 高電位階段為孔蝕成核 期, 電位持平階段為隧道成長期4. 經磷酸前處理試片之孔蝕電位, 在 A 及 B 電蝕液中測試時, 均呈現隨磷酸濃度增加而下降(i.e.愈active)之 趨勢; 而 A 溶液(HCl+H2SO4) 中之孔蝕電位較 B 溶液 (HCl)者高(i.e. 較noble), 且電蝕時生成較大密度之隧道.5. 電蝕液溫度對隧道之成核生 長關係密切. 在 A 電蝕液中, 於50C即發現有隧道生成. 而在50C以上, 隨電蝕液溫度升高, 其隧道寬度變小, 臨界長度縮短, 且過電位, transient time,孔蝕電位等呈現下降之趨勢. Aluminum electrolytic capacitor is applied extensively in the circuit ystem, and large demaneding is therfore exit. For the sake of size minimization,in improving the high-voltage capacitor usage, the industry interest is focusedon enlargement of the apparent foil surface, and electrolytic etching is one ofthe method to achieve this object. The surface characteristics of the pretreated foil would affect the electrolytic etching behavior. Good pretreatment can effectively improve the quality of the foil surface such that good etching behavior and hence high quality capacitor can be expected. In the thesis, effects of phosphoric acid pretreatment on the characteristicsof aluminum foil and its electrolytic etching behavior are studied and the following results are reached: 1. After the phosphoric acid pretreatment, the foil surface is apparentlyetched to a greater extent as the phosphoric acid concentrationincreases. Therolling line is the preferred etching zone. 2. By XPS, ATR analyses, it is shown that the phosphoric acid absorption increasesas its concentration increases. 3. It is proved that in the potential transient during etching, pit initiates in the potential plateau stage. 4. After the phosphoric acid pretreatmen3. the pitting potentials in A (HCl+H2SO4) and B (HCl) electrolytes move toward active direction as the phosphoric acid concentration increases. The pitting potential is generallynobler in A solution than in B solution, also a higher tunnel density is obtainedin the A solution. 5. The initiation and growth of tunnel are affected significantly by the etching temperature. It is found that tunnel forms even at 50C. Above 50C, as temperature increases tunnel width becomes smaller, critical length becomesshorter, also the overshoot potential, transient time and pitting potentialall tend to decrease or descend.