1070-4272/05/7804-0579 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 4, 2005, pp. 579!583. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005,
Original Russian Text Copyright + 2005 by Turaev, Kruglikov.
AND CORROSION PROTECTION OF METALS
Regeneration of a Solution for Electroless Copper Plating
D. Yu. Turaev and S. S. Kruglikov
Mendeleev Russian University of Chemical Technology, Moscow, Russia
Received September 15, 2004; in final form, February 2005
Abstract-The possibility of electrochemical regeneration of a solution for electroless copper plating by
membrane electrolysis was studied. The conditions of anodic dissolution of copper in a spent solution for
electroless copper plating, under which the concentration of copper ions increases at a rate exceeding by
an order of magnitude that of their deposition in the course of electroless copper plating, were examined.
A scheme for regeneration of spent solutions for electroless copper plating was suggested.
Metals are commonly deposited from aqueous so-
lutions to obtain metal coatings with various func-
tional properties by the electrochemical method.
However, the method of chemical reduction is used
in some cases (electrically nonconducting support,
intricate shape of articles). An electrically conducting
sublayer for subsequent electrodeposition of metals
and alloys is most frequently deposited by electroless
copper plating. When in use, solutions for electroless
copper plating accumulate reaction products and this
restricts their service life. In this study, the method of
membrane electrolysis was used to develop a process
for complete regeneration of a tartrate-formaldehyde
solution for electroless copper plating, widely used
The reduction of copper ions is described by
+ 2HCOH + 4OH
Equation (1) expresses the overall result of the con-
jugated cathodic and anodic reactions:
2HCOH + 4OH
+ 2e, (3)
stands for the tartrate ion C
The equilibrium potential of reaction (3) depends
on the solution pH:
(4)E = 0.372 3 0.118pH.
It was shown in  that the anodic reaction (3)
occurs in a number of stages to form unstable inter-
mediates. A side reaction in electroless copper plating
is the disproportionation of formaldehyde (Cannizzaro
reaction) [2, 3]:
2HCOH + OH
When in use, the solution is to be adjusted at reg-
ular intervals of time by addition of copper sulfate,
alkali, and formaldehyde, in order to compensate for
the consumption of these components. However, SO
, and CO
ions are simultaneously accumu-
lated, which impairs the plasticity of the copper films
obtained. For example, additional introduction of
0.28 M SO
into the working solution leads to a de-
crease in the relative elongation at break of a copper
film by a factor of 6312 . Therefore, the incapacita-
tion of solutions for electroless copper plating is due
to accumulation of reaction products, rather than to
consumption of the starting reagents.
In , a method for regeneration of solutions for
electroless copper plating with a three-chamber elec-
trolyzer having two anion-exchange membranes was
described. The middle chamber of the electrolyzer
contains a solution to be regenerated, and the cathode
and anode chambers, a sodium hydroxide solution and
dilute sulfuric acid, respectively.
In the present study, copper ions were introduced
into a solution for electroless copper plating by anodic
dissolution of copper, which yields solutions contain-
ing the minimum amount of copper sulfate.
Two- and three-compartment cells with cation- and
anion-exchange membranes, working volume of each
compartment equal to 25330 ml, and working sur-
face area of each membrane of 16 cm
were used in