Sodium permanganate etch baths containing a co-ion for permanganate and their use in desmearing and/or etching printed circuit boards

A process for preparing a resinous substrate for subsequent metallization which comprises contacting said substrate with an aqueous, alkaline liquid NaMnO.sub.4 solution comprising water, alkali metal hydroxide, NaMnO.sub.4 and from about 0.1 to about 3.0 moles per mole of MnO.sub.4 of a co-ion for MnO.sub.4.sup.- selected from the group consisting of K.sup.+, Cs.sup.+, Rb.sup.+ and mixtures thereof.

An improved process for desmearing resin from the inside walls of holes formed in resinous substrates wherein the improvement comprises contacting the substrate with an aqueous, alkaline liquid NaMnO.sub.4 solution comprising water, alkali metal hydroxide, NaMnO.sub.4 and from about 0.1 to about 3.0 moles per mole of MnO.sub.4.sup.- of a co-ion for MnO.sub.4.sup.- selected from the group consisting of K.sup.+, Cs.sup.+, Rb.sup.+ and mixtures thereof.

An improved hole cleaning process for multilayer circuit boards wherein the improvement comprises contacting the multilayer circuit boards with aqueous, alkaline liquid NaMnO.sub.4 solution comprising water, alkali metal hydroxide, NaMnO.sub.4 and from about 0.1 to about 3.0 moles per mole of MnO.sub.4.sup.- of a co-ion for MnO.sub.4.sup.- selected from the group consisting of K.sup.+, Cs.sup.+, Rb.sup.+ and mixtures thereof.

A process for etching back the surface of a circuit board which comprises contacting the circuit board with an aqueous, alkaline liquid NaMnO.sub.4 solution comprising water, alkali metal hydroxide, NaMnO.sub.4 and from about 0.1 to about 3.0 moles per mole of MnO.sub.4.sup.- of a co-ion for MnO.sub.4.sup.- selected from the group consisting of K.sup.+, Cs.sup.+, Rb.sup.+ and mixtures thereof.