Abstract: This invention is directed to an etchant and to a process for its use. The etchant comprises sulfuric acid activated with hydrogen peroxide or the synergistic combination of hydrogen peroxide and molybdenum. The etchant is characterized by a source of phosphate ions as an inhibitor against attack on tin, especially immersion tin, as well as several other metals such as nickel and alloys of nickel such as gold alloys. The etchant is especially useful for etching copper and its alloys in the presence of a tin etch resist, and therefore, provides a new procedure for the fabrication of printed circuit boards using immersion tin as an etch resist.

Abstract: This invention is directed to an etchant and to a process for its use. The etchant comprises a synergistic combination of hydrogen peroxide and molybdenum as oxidants in acidic solution. The combination of oxidants provides for sustained etching at an exalted rate. The etchant is useful for etching metals, especially copper and its alloys, and is particularly useful in the manufacture of printed circuit boards.

Abstract: An electroless metal plating solution is characterized by an elemental sulfur stabilizer, either in colloidal or soluble, non-ionic form. Elemental sulfur as a stabilizer is an improvement over prior art stabilizers as it can be used in substantially larger concentration than prior art divalent sulfur stabilizers which are catalytic poisons.