Additives to the electrolyte for copper plating of through-holes in multilayer printed-circuit boards

• V.Kh. Aleshina, N.S. Grigoryan, N.A. Asnis, T.A. Vagramyan and T.I. Kuznetsova

Mendeleev University of Chemical Technology of Russia, Miusskaya pl. 9, 125047 Moscow, Russian Federation

Abstract: As technologies are developing, the design of multilayer printed-circuit boards gets increasingly complicated, and requirements for their quality become increasingly stringent. To manufacture state-of-the-art high-accuracy printed-circuit boards with small aspect ratio values, copper plating electrolytes with high throwing power are required. We are developing an electrolyte for copper plating of through-holes in multilayer printed-circuit boards that enables the production of uniform bright plating both inside the holes and on the printed-circuit board surface. The effect of inhibiting, leveling, and brightening additives on the throwing power of electrolytes and copper plating distribution in the holes and on the surface of a printed-circuit board and the plating gloss have been studied. It has been found that adding polyethylene glycols to the electrolyte enhances the throwing power by 5% on average and, if the solution contains both polyethylene glycol and a leveler (a nitrogen-containing surface active agent), the throwing power increases by more than 10%. It has been shown that if PEG 4000 polyethylene glycol is added to a sulfuric acid copper plating electrolyte together with leveling agents, methyl violet or safranine Т, copper reduction is significantly inhibited (polarization is ~200 mV), and the process polarizability increases in the entire range of current densities. It has been determined that a combination of the PEG 4000 inhibitor, Janus Green B leveling agent or polyethylenimine, and the MPS accelerating agent in the electrolyte provides bright and uniform plating both inside the holes and on the surface of printed-circuit boards.

Keywords: printed-circuit boards, copper plating electrolyte, throwing power, copper plating of printed-circuit board holes, inhibiting additives, leveling additives, brightening agent, copper electroplating

Int. J. Corros. Scale Inhib., 2021, 10, no. 4, 1661-1676
doi: 10.17675/2305-6894-2021-10-4-18

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