PROBLEM TO BE SOLVED: To improve coating properties on the back side of an exposed surface of a pattern-developed copper foil-laminated polyimide tape and resistance to etchant by dissolving a vinyl acetate resin and an acrylic polymer in a mixed solvent comprising xylene and an alcohol.;SOLUTION: A vinyl acetate resin, an acrylic polymer and, if required, a cresol resin are mixed so that the volume ratio thereof is 1:1:1 to give a mixed resin, which is dissolved in a mixed solvent obtained by mixing xylene with an alcohol so that the volume ratio is 1:1 to give the etching backing agent having a viscosity of 50-70 cP. Thus, the obtained coating film is resistant to an etchant under a high temperature and a high pressure in etching and easily removable when stripped with an alkali solution. This etching backing agent can be applied and filled even in a small hole or the like to form an even coating with a uniform thickness which is excellent in etching resistance and free from tears in a coating film and corrosion at the tip of a pin.;COPYRIGHT: (C)2000,JPO
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