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How to Regenerate Copper Etching With Cupric Chloride

Copper etching solution is used in the production of printed circuit boards. The removal of the copper on the circuit board leaves copper traces on the board in areas where the resist exists. The chemical reaction occurring at the surface of the copper on board is Cu(s) + Cu2+ --> 2 CuCl. To maintain the effectiveness of the etching solution, you must regenerate the copper (II) chloride. The regeneration reaction is 2HCl + 2 CuCl + O -->2 CuCl2 + H2O. The etching solution has an excess of HCl in solution, which provides the chlorine needed for regeneration. The oxidizing agents available for conversion of CuCl back into CuCl2 include oxygen from air, hydrogen peroxide, sodium chlorate, dissolved chlorine and dissolved oxygen.

Things You'll Need

Aerator
Compressed air supply
Cupric chloride etching solution

Instructions

- 1
  Install an aerator into the bottom of the cupric chloride etching tank. To provide complete exposure of the etching solution to aeration, place the aerator as far down in the tank as possible.
- 2
  Connect a compressed air supply to the aerator. The aeration of the etching solution can occur periodically or constantly during operation. The choice of how aeration occurs depends on the load of the etching process. A system that requires a heavy loading of boards for cost-effective operation will work better using a periodic aeration methodology. After each etching run, aerate the solution back to the original state of the etching solution.
- 3
  Turn on the air supply and allow the compressed air to bubble through the solution until you reach a solution with a transparent bright green color, which indicates a concentration of cuprous ion less than 1 gram per liter. To ascertain the color of the solution, place a drop of the etching solution on a white background.

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