Abstract: The present invention includes an etching agent that selectively etches a copper layer of a processing target in which a noble metal layer containing a metal nobler than copper and the copper layer coexist, the etching agent including: a copper ion; one or more nitrogen-containing compounds selected from the group consisting of a heterocyclic compound having two or more nitrogen atoms in a ring and an amino group-containing compound having 8 or less carbon atoms; a polyalkylene glycol; and a halogen ion, in which the polyalkylene glycol is contained in an amount of 0.0005% by weight or more and 7% by weight or less, and the halogen ion is contained in an amount of 1 ppm or more and 250 ppm or less.

Abstract: In manufacturing a printed circuit board using a semi-additive method, a removal liquid that has been used in removing a nickel-chromium-containing layer (5) is regenerated by contacting the removal liquid with a chelate resin having a functional group represented by a following formula (1) : where a plurality of Rs are identical divalent hydrocarbon groups having 1 to 5 carbons, and a portion of hydrogen atoms may be substituted with halogen atoms.

Abstract: A regenerating method of a removal liquid including: removing a nickel-chromium-containing layer from a substrate using the removal liquid at a time of manufacturing a printed circuit board by a semi-additive method, the substrate including the nickel-chromium-containing layer and a copper-containing layer; collecting the removal liquid that has been used; and contacting the collected removal liquid in collecting the removal liquid with a chelate resin, wherein the chelate resin includes a functional group represented by a following formula (1): where a plurality of Rs are identical divalent hydrocarbon groups having 1 to 5 carbons, and a portion of hydrogen atoms in the hydrocarbon groups are substituted with halogen atoms or not substituted with a halogen atom.