Influence of Temperature on Electroless Copper Deposition from Formaldehyde-Containing Solutions Using 2-Hydroxy-1,2,3-Propanetricarboxylic Acid As Cu(II) Ligand

Abstract

Electroless coating technique is one of the ways to obtain metallic coatings in which there is no usage of electric current. Trisodium salt of 2-hydroxy-1,2,3-propanetricarboxylic acid (citric acid), forming sufficiently stable complexes with copper(II) ions in alkaline solutions, was found to be a suitable ligand for copper(II) chelating in alkaline (pH > 12) electroless copper deposition solutions. The measurements were carried out in electroless copper plating solutions for 30 or 60 min. at pH 12.0 – 13.0 and 10 – 30 °C temperature. The thickness of the compact copper coatings obtained under optimal operating conditions in 1 h can reach ca. 3 μm. The copper surface determination method is based on the underpotential deposition of the thallium monolayer on the Cu electrode surface. The real surface area (in nano-scale dimensions) of the Cu electrode (SR , cm2) was calculated using the Tl monolayer capacity Q Tl. The surface nano-scale roughness factor R f is calculated as a ratio of real and geometric surface areas. From Cu(II)-citrate solutions deposited copper coatings surface roughness factor (R f) vary from ca. 2.5 up to 15.0.