Kinetics of electroless copper deposition using cobalt(II)-ethylenediamine complex compounds as reducing agents

Abstract

Electroless copper deposition using Co(II)-ethylenediamine (En) complexes as reducing agents was investigated in 0.4–1.2 M En solutions at 50 and 70 °C. There is a complicated dependence of the process rate on pH, En concentration and temperature. A copper deposition rate up to 6 μm h⁻¹ (50–70 °C) in relatively stable solutions (pH ∼ 6) can be achieved. The stoichiometry of the Cu(II) reduction at pH 6–7 corresponds to the reaction:

$${\text{Cu}}En_2^{2 + } + 2{\text{ Co}}En_2^{2 + } \xrightarrow{{{\text{Cu}}}}{\text{Cu + 2 Cu}}En_3^{3 + } $$

The correlation between the rate of the copper deposition on the catalytic surface and the concentration of the ${\text{Cu}}En_2^{2 + }$ complex species in the solution was found.