THE EFFECT OF LEAD IMPURITY ON THE DC-ETCHING BEHAVIOR OF ALUMINUM FOIL FOR ELECTROLYTIC CAPACITOR USAGE

The effects of lead impurity on the etched morphology of high purity a luminum foils for electrolytic capacitor applications were investigate d in this work. The lead impurity was either present in as-received al uminum foils or deposited purposely on the foil surface through an imm ersion-reduction reaction. The amount and distribution of deposited le ad varies with the lead content in as-received foil. The as-received f oil with higher lead content gave a higher concentration and a more un iform distribution of deposited lead. Uniformly distributed vertical t unnel etchings were obtained when high lead foil, formed by immersion as-received high lead foil in Pb(NO3)(2) solution, was subject to DC-e tching. For the as-received lower lead foils, the deposited lead was c oncentrated in rolling lines which resulted in surface etching along r olling lines. Both the surfacial and cross-sectional etching morpholog ies are presented in this study, together with the etching mechanism d iscussed. Copyright (C) 1996 Elsevier Science Ltd.