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Direct Recycling of Copper I, ETUfR u , c - From Etching to Plating

- Jan 24, 2019 -

In the manufacture  of  printed circuit boards, the copper

dissolved during etching can be used to replace the

copper needed  for  plating using a liquid ion-exchange

agent. Extraction and stripping studies demonstrated the

feasibility. The quality  of  the etchant was not affected by

the presence of the ion-exchange agent. Good-quality

deposits were plated from the stripping solution with a

current efficiency of  100  percent.

The feasibility  of  directly recycling copper from etching to

plating has been demonstrated. The extraction of copper

from etchant by a liquid ion-exchange reagent and the

stripping of copper from a loaded  LIR  solution to the plating

bath were performed without difficulty.

The extraction isotherm shows that the LlR can be

loaded  to  40 g/L Cu. We explained the extraction isotherm

using mass balance and equilibrium calculations. Thus,

various operating parameters were also calculated. For

example, the influence of the ratio of the volumetric flow

rate of etchant  to  LIR  solution in a continuous process was

predicted. In the stripping process, copper removal  is  not

difficult. The copper concentration of the acid plating bath

is set by the solubility  of  copper sulfate, i.e., about 60 g/L

copper.

Although the etchant has a concentration of 180 g/L

chloride ions, the stripping solution has less than  50  mg/L

chloride. Thus, the brighteners work properly. Trace

amounts  of  LIR were easily oxidized anodically and the

byproducts influenced the plating. Hull Cell panels clearly

illustrated this effect. This problem was eliminated when an

anode bag made of Cationic membrane was  used.  Then we

were able to obtain good copper deposits from the stripping

solution with a current efficiency Close  to  100  percent.

Although we did not attempt  to  mgenerate the etchant.

no major problem is expected. The etch quality of the

etchant was not affected by the presence of LIR. The

regeneration  of  etchant should be investigated  in  pilot-

plant studies.

Since the process involves flammable solvent, safety

precautions must be exercised to prevent explosions and

fires. We believe that safeguards which eliminate the

inherent danger of handling kerosene can be engineered

into the proposed process.