Search

Uniform electrodeposition of through-hole (TH) with a high aspect ratio is the key to the reliability of printed circuit board (PCB) interconnection. Inhibitors produce stronger inhibition at high potentials during TH electrodeposition and thus reduce the difference in electrodeposition rates between inside and outside the TH. In this paper, the electrochemical behavior of an ethylene oxide propylene oxide random copolymer (EO-PO) as an inhibitor on the cathode during periodic pulse reverse (PPR) electrodeposition was systematically studied. The results show that EO-PO will rotate under the effect of reverse pulse, and adsorb more strongly on the cathode surface, which inhibits the "cathode stripping" process of the reverse pulse. Through the electrodeposition experiments, compared with direct current (DC) electrodeposition, the PPR method effectively eliminates the copper nodule and improves the concentration window of EO-PO. The results pave the way for regulating and controlling TH electrodeposition with other additives. [Display omitted] [ABSTRACT FROM AUTHOR]

The inhibitory effect of molecular weight (Mw) of polyethylene glycol (PEG) on the through-hole filling by copper electroplating was investigated by the electrochemical testing method and energy change with DFT. The cathodic polarization, electron transfer resistance, and diffusion coefficient of PEG with different Mw and concentration were assayed by cyclic voltammetry and electrochemical impedance spectroscopy; The inhibitory effect of different PEG Mw was demonstrated and examined by cross-sectional images using OLYMPUS confocal laser microscope, and the thickness of the copper layer and TP value were important measurement standards. The adsorption behavior on copper surfaces was calculated using the first principles. As PEG Mw and concentration are increased, the best TP value and diffusion coefficient of the plating formula is gained when PEG Mw and concentration are 20000 g/mol and 250 mg/L, they are 148.56% and 2.34 × 10-7, respectively. Better adsorption energy can be obtained as the adsorption sites of PEG increases, and the adsorption energy of PEG5 is − 1.99 eV. The experimental and theoretical results show that PEG with small Mw has no inhibitory effect, and even accelerates the deposition rate of Cu2+/1+. Only when the Mw and concentration exceed 2000 g/mol and 150 mg/L, PEG can inhibit the deposition of Cu2+/1+, and the best effect of through-hole electroplating is 20000 g/mol and 250 mg/L. [Display omitted] [ABSTRACT FROM AUTHOR]

The methanesulfonate system is gradually replacing the traditional highly polluting fluoride electroplating lead （Pb） system with its eco-friendly advantage, and searching for suitable additives is crucially important to obtain uniform Pb coatings in the methanesulfonate system. In this work, a potential additive of thiourea suitable for methanesulfonate-based Pb electroplating was screened based on the theoretical calculations and cyclic voltammetry tests, and the effect of thiourea in the Pb electrodeposition was investigated. Specifically, the adsorption-coordination mechanism was proposed to explain the effect of thiourea by calculating the Bader charge density difference of thiourea on Pb surface and its interaction with Pb2+. Meanwhile, the effects of thiourea on the electrochemical behavior of lead electrodeposition were investigated by cyclic voltammetry and chronoamperometry. The nucleation and growth of Pb follow 3D diffusion-controlled progressive nucleation at the low potential and high thiourea concentration but follow 3D diffusion-controlled instantaneous nucleation at the high overpotential. The appropriate concentration of thiourea could improve the surface morphology of lead coating and make the layer flat and dense. The influence of thiourea on the crystalline orientation and grain size of the coating was analyzed, which indicated that the increase of thiourea concentration favored the formation of the Pb (220) crystal plane and the decrease of grain size. [Display omitted] [ABSTRACT FROM AUTHOR]