Influence of Temperature on Electroless Copper Deposition from Formaldehyde-containing Solutions using 2-hydroxy-1,2,3-propanetricarboxylic Acid as Cu(Ⅱ) Ligand

摘要

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 ℃ temperature. The thickness of the compact copper coatings obtained under optimal operating conditions in 1 h can reach ca. 3 m. 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 (S_R, cm~2) 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.