D.Mendeleev University of Chemical Technology of Russia, Moscow, Russia

M. S. Solopchuk, Postgraduate Student, e-mail: mariya.solopchuk.96@mail.ru
N. S. Grigoryan, Associate Professor, Professor at the Department of Innovative Materials and Corrosion Protection, Candidate of Chemical Sciences
T. A. Vagramyan, Head of the Department of Innovative Materials and Corrosion Protection, Professor, Doctor of Technical Sciences
P. O. Shmelkova, Master’s Student at the Department of Innovative Materials and Corrosion Protection

Electroless copper plating is a process that is widely used for indirect metal plating of dielectric in the production of printed circuit boards, and namely for depositing the first metal layer — i. e. a 0.3 to 1.0 μm thick chemical copper coating in the openings of workpieces. The properties of such chemical copper coating dictate the quality of the following metal layers — a copper flash (5–6 μm) and the basic galvanic layer (25–30 μm). This paper is aimed at the development of electroless copper plating solutions to substitute the imported ones. They are trilonate and tartrate solutions and they are used for metal plating at modern production site. The paper looked at the effect of the concentration of components in the solutions on the deposition rate, as well as the stability and soundness of coatings in the openings. The soundness of coatings was assessed with the help of backlight test, which is used by developers and producers both in Russian and abroad. It was established that the concentration of ligand slightly influences the rate of deposition from tartrate solutions, unlike it is with coatings deposited from trilonate solutions, when the deposition rate rises as the concentration of ligand increases. This can be associated with the buffer properties of ethylene diamine tetraacetic acid (or, EDTA). It was found that with a small amount of nickel sulphate present in the tartrate solution — in contrast to the trilonate solution — nickel tends to codeposit with copper in the amount of 1–2% modifying the structure of the coating. The authors developed a tartrate solution for electroless copper plating of openings in printed circuit boards containing, g/L: 8.5 CuSO₄·5H₂O; 2.0 NiSO₄·7H₂O; 16.5–65.8 KNaC₄H₄O₆·4H₂O; 6–9 NaOH (free); 5–13 ml/L of 37 % formaldehyde, 0.5 mg/L DEDTC-Na. With the help of the above solution, one can obtain quality electroless copper coatings in 15 min at the temperature of 35 ^oC. The authors also developed a trilonate solution for electroless copper plating of openings in printed circuit boards containing, g/L: 8.0 CuSO₄·5H₂O; 32–64 Trilon B; 6–9 NaOH (free); 7–13 ml/L of 37% formaldehyde, 0.5 mg/L DEDTC-Na, enabling to obtain quality electroless copper coatings in 20 min at the temperature of 25 ^oC.
This research was funded by D.Mendeleev University of Chemical Technology of Russia. Project number: VIG-2022-015.
The research was carried out using the equipment of the D. I. Mendeleev Center for Collective Use within the framework of project No. 075-15-2021-688.

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