Patent ID: 8486281

Claim:
A method of selectively etching a wiring board, wherein the printed wiring board comprises an electrically insulating base material, a metal tie coat layer and a copper layer, the method comprising immersing the flexible wiring board in an etching solution comprising: i) an acid selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, sulfonic acid, sulfamic acid and combinations of one or more of the foregoing; ii) a source of halide ions; and iii) a sulfur compound comprising a sulfur atom with an oxidation state in the range of −2 to +5; for a period of time and at a temperature sufficient to remove the metal tie coat layer wherein the metal tie coat layer comprises a nickel-chromium alloy and wherein the etch solution etches less than 2 μin of copper; and wherein the addition of the sulfur compound to the etch solution increases the etching rate of the nickel-chromium alloy while creating no detrimental attack on the copper layer, wherein the concentration of the sulfur compound is between about 180 to about 500 ppm.