US 4,395,302 AGranted

Metal dissolution process using H.sub.2 O.sub.2 --H.sub.2 SO.sub.4 etchant

AssigneeEnthone Inc.

InventorConstantine I. Courduvelis

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Abstract

An improved process for dissolution of metals by etching, and particularly the etching of copper in printed circuit board processing or the like, using an aqueous H.sub.2 O.sub.2 --H.sub.2 SO.sub.4 etching solution, in which the concentration of H.sub.2 SO.sub.4 in the etching solution is allowed to decrease during use of the etching solution from an initial, relatively high level at the time the etching solution is put into use, to a final, relatively low level. When a predetermined concentration of dissolved etched metal exists in the etching solution, the etching solution is removed from use, H.sub.2 SO.sub.4 is added to increase the concentration of H.sub.2 SO.sub.4 in the etching solution to approximately the initial, relatively high level, and the metal is precipitated out of the etching solution.

Claims8

Dependent claims

In a process for dissolving a metal by etching with an aqueous solution, wherein the aqueous etching solution includes initial predetermined high levels of of H.sub.2 O.sub.2 and H.sub.2 SO.sub.4 in water, the improvement comprising:

etching the metal from work pieces with the etching solution while permitting the concentration of H.sub.2 SO.sub.4 in the etching solution to decrease from its high level to a predetermined low level which is not more than about one-half of the predetermined high level, and until the concentration of etched metal dissolved in the etching solution reaches a predetermined level;
removing the etching solution from use;
adding H.sub.2 SO.sub.4 to the etching solution to increase the H.sub.2 SO.sub.4 concentration to the predetermined high level;
allowing the metal dissolved in the etching solution to precipitate out of the etching solution, and
recycling the metal-depleted etching solution to the etching step.

2 more elements

Dependencies are inferred from the claim text.