電解コンデンサ用高純度アルミニウム箔のピット形成に及ぼす電解液浸漬時間の影響

抄録

The effects of surface dissolution of high-purity aluminum foils for electrolytic capacitors during immersion in hot hydrochloric acid on distributions of pits initiated by direct current (DC) etching are discussed. Pit structures were observed with TEM of oxide films stripped from etched foils in I₂/methanol solution. Anodized oxide film replicas were prepared for SEM to observe pit distribution. γ-Al₂O₃ crystals with sizes of 0.2-0.3μm were observed on rolling lines of oxide films. With increasing electrolyte immersion time before DC etching, areas of surface dissolution of aluminum foils around γ-Al₂O₃ crystals expanded. When immersion time was prolonged from 0s to 60s, pits were initiated uniformly because of the increase in active sites. Excess active sites on surfaces formed above 60s delayed tunnel pit growth.