Manufacturing A Fine Pattern Fpc Of Aluminum-polyester Composite

In contrast to Cu, for metals with larger ionization potential than that of hydrogen, the potential difference between etchant and the metal surface generate hydrogen and the metal dissolves. The etching by such a corrosion cell formation is also true for the acidic condition such as in HC1 or in concentrated H3P04 also under basic conditions in aqueous NaOH. The mechanism explains the difficulty to achieve the fine pattern etching of Al. Compositions of the Al/PET used are summarized in Figurel. Chemically stable thin aluminum oxide layer covers the Al surface. The dissolution rate of the oxidized layer is much slower than the metallic Al dissolution rate by the corrosive cell formation. Therefore the two sides of the A 1 2 0 3 layer resists the etching while the metallic Al layer reacts to dissolve quickly. This results in the great undercut (Figure2). CO-existing other metals, the direction of Al metal crystal lattice, its perturbation or residual strain cause the potential differences. The potential in-homogeneity occurs in the etching reaction. The effects of different metal ions not only in the case of FeC13 etching system but also with contaminated trace amounts of impure metals such as Fe, Cu and Si cause the difference in etching rate. This impure metal suffers dissolution and deposition alternatively. When attachment to .the Al surface, the Al-dissolution rate becomes greater because of the larger potential difference. The attachment of the generated H2 bubble on the Al layer stops the etching on the attached area.