Method of regenerating an ammoniacal etching solution

Details Method of regenerating an ammoniacal etching solution Method of regenerating an ammoniacal etching solution

C - Chemistry, Metallurgy

25

C

204/66, 149/7

C25C 1/00 (2006.01) C23F 1/46 (2006.01)

Patent

CA 1175323

Title: METHOD OF REGENERATING AN AMMONIACAL ETCHING SOLUTION ABSTRACT OF THE DISCLOSURE In addition to catalyzing the reoxidization of spent alkaline etching agent, the suspension of activated carbon powder in the etching solution also increases the speed of etching when the etching solution is recirculated in the etching of printed circuit boards. The ammonium sulfate etching solution is set to a pH of about 9 by the addition of ammonia gas. In the recirculation of the etching solution, a part of the solution can be freed by filtration from sus- pended carbon particles and passed through the cathode and anode chamber= of an electrolysis cell for the recovery of the etched metal by deposition at the cathode. The activated carbon powder for this purpose is calcined before use, at a temperature of between 900 and 1200 °C in vacuum or in an atmosphere that is inert, reducing, or only slightly oxidizing as in the case of an atmosphere containing carbon dioxide, water vapor or both, in a concentration that does not appreciably oxidize the carbon particles. - 15 -

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