Peculiarities of Electroless Copper Deposition Using Environmentally-Friendly Natural Polyhydroxylic Compounds As Cu(II) Ligands

Cu(II) ligands are important components of common formaldehyde-containing alkaline electroless copper plating baths:

Cu(II)-Ligand + 2CH₂O(hydrated) + 4OH^-  →   Cu  +  2HCOO^-  +  H₂  +  2H₂O  +  Ligand                      (1)

From one hand, the ligands used should form Cu(II) complexes stable enough to prevent Cu(OH)₂ formation, since the solubility product of Cu(OH)₂ is of the order    10^-18 and the concentration of “free” (uncomplexed) Cu(II) ions in the pH range 11–14 cannot exceed 10^-12–10^-18 M, respectively. On the other hand, it is worth to note that kinetics of copper deposition as well as the properties of copper deposits (compactness, exterior, morphology and crystal structure) in high extent depend on the nature of ligands used for Cu(II) binding into complexes in electroless copper plating solutions.

The aim of the study presented herein was comparison of the parameters of process of electroless copper plating – mainly plating rate and nanoscale surface roughness of the copper deposits obtained, – using different polyhydroxylic ligands under the similar conditions.

The ligands considered were glycerol, xylitol, D-mannitol, D-sorbitol and saccharose.

Acknowledgement

The work was carried out within the Project VP1-3.1 ŠMM-08-K-01-009 that is partly supported by the National Programme “An Improvement of the Skills of Researchers” launched by the Lithuanian Ministry of Education and Science.