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
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-
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.