Hydrogen peroxide etching of copper in manufacture of printed circuits

A solvent for metals for use in etching printed circuits or other dissolving operations such as chemical milling or polishing, comprises an acidified aqueous solution of hydrogen peroxide to which has been added a catalytic amount of phenacetin or sulphathiazole or silver ions or mixtures thereof. When phenacetin is used alone, the solvent must contain less than 2 parts per million by weight of free chloride or bromide ions. The solution contains 2%-12% by weight of hydrogen peroxide and 2%-23% by weight of sulphuric acid. Other acids such as acetic acid, nitric acid or fluoboric acid may be employed. Salts yielding the additives in the acid-peroxide solution may be employed e.g. the sodium salt of sulphathiazole, silver nitrate, silver sulphate. If water containing excessive amounts of chloride and bromide ions is used in the solvent, suitable material such as a water soluble silver salt is added to remove the free chloride and bromide ions. Acid may be added during the use of the solution to keep the concentration at the required amount. Etching is carried out at a temperature of 40 DEG C.-65 DEG C. The solvent may be used for etching copper, iron, nickel, cadmium, zinc, germanium, lead, steel and aluminium and alloys thereof.