To form a rough surface excellent in acid resistance at a high etching rate in a short time by acicularly etching the surface of copper with an etching soln. contg. a main agent of a specified oxo acid or a derivative thereof and a peroxide or the derivative thereof and an assistant of tetrazole or the like.
The surface of copper is etched with an etching soln. contg. an oxo acid such as sulfuric acid expressed by the chemical formula of XOm(OH)n or HnXOm+n {in the formulae, X denotes the center atoms of S, P, N or the like, (m) is ≥0, (n) is ≥1, preferably, (m) is ≥2 or (m+n) is ≥4} or a derivative thereof and a peroxide such as hydrogen peroxide or a derivative thereof as the main agent and contg. tetrazoles, azole or tetrazole of 1,2,3-azoles and contg. a halide, if necessary, as an assistant. At this time, by tetrazole or the like as the assistant, a carrier layer is formed on the surface of copper through electrons, and the etching is stably executed at a high dissolving rate to form a rough face having acicular ruggedness insoluble in acids.
SENBIKI KAZUNORI
YAMAZAKI NOBUHIRO
