Application study on 1-dodecylpyridinium chloride as a leveling agent for blind via copper electroplating
LUO Yan;YAO Hui;SONG Zihao;WAN Chuanyun;[Objective] Taking 1-dodecylpyridinium chloride(LPC) as an example, this study investigates the feasibility of using alkyl pyridinium compounds as electroplating leveling agents in blind via filling. [Method] The effect of LPC concentration on the electrodeposition behavior of copper ions, blind via filling efficiency, and microstructure of copper coating was studied through density functional theory(DFT) calculations, electrochemical measurements, Haring cell plating experiments, and characterization by scanning electron microscopy(SEM) and X-ray diffraction(XRD), with a comparative study against the conventional leveling agent Janus Green B(JGB). [Result] DFT calculations revealed that LPC possessed a smaller energy gap(3.057 e V) compared with JGB(3.420 e V), suggesting theoretically stronger adsorption affinity toward the copper surface. Moreover, the low electron density of LPC was concentrated at the terminal end of the alkyl chain, facilitating the formation of a hydrophobic inhibition layer. Electrochemical measurements indicated that LPC acted as a depolarizer to promote copper deposition at mass concentrations not exceeding 8 mg/L, whereas it switched to inhibiting copper deposition when the mass concentration was increased to 12 mg/L. At this concentration, both the difference in anodic oxidation peak area(91.4 μC) and the difference in chronopotentiometric potential(29.10 mV) between high and low rotational speeds reached their maximum values. Haring cell electroplating experiments showed that a blind via filling efficiency of 87.4% was achieved at an LPC mass concentration of 12 mg/L, outperforming the 75.6% obtained with JGB at the same concentration. SEM and XRD analyses confirmed that the addition of LPC refined the copper grains and promoted the preferential orientation of the Cu(111) crystal plane, with the smoothest surface and the highest Cu(111) diffraction peak intensity attained at 12 mg/L. [Conclusion] As a smallmolecule pyridine-based leveling agent, LPC demonstrates promising application potential for blind via copper electroplating. This study provides theoretical foundation and data support for the utilization of small-molecule alkyl pyridinium compounds as leveling agents in acidic copper plating systems.
Preparation of high-tensile-strength copper–nickel alloy foil by electrodeposition in a pyrophosphate bath
LIU Feiyang;ZHANG Han;LI Jiujuan;CHEN Wenjin;JIANG Qitao;KOU Xiaoqin;ZHOU Guoyun;HONG Yan;WANG Chong;[Objective] To develop high-performance ultrathin current collectors, the feasibility of preparing Cu–Ni alloy foils by electrodeposition in a pyrophosphate system was studied, and the effect of key process parameters on the properties of Cu–Ni alloy foils was studied. [Method] Key influencing factors were first screened using a PlackettBurman experimental design, followed by single-factor experiments to optimize the concentrations of K_4P_2O7 and NiSO4·6H_2O. The optimal formulation was determined through macroscopic morphology observation and tensile strength testing. The properties of the foils obtained under the optimized conditions were characterized using scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD), and tensile testing. [Result] The conditions for electrodepositing Cu–Ni alloy foil were optimized as follows: CuSO4·5H_2O 0.05 mol/L, NiSO4·6H_2O 0.10 mol/L, K_4P_2O7 0.50 mol/L, Na_3C_6H_5O7·2H_2O 0.10 mol/L, pH 9.0, temperature 60 °C, current density 1.0 A/dm2, and stirring speed 400 r/min. The Cu–Ni alloy foil obtained under the optimal conditions had a thickness of approximately 6 μm, a Ni mass fraction of about 3.28%, a uniform and compact structure, and a high tensile strength of 796.58 MPa. [Conclusion] A uniform Cu–Ni alloy foil can be successfully prepared by electrodeposition in a pyrophosphate bath. This study provides a reliable technical route for the industrial fabrication of high-performance ultrathin current collectors.
Study on factors affecting surface insulation performance of PCB
ZHENG Xubin;LI Juanjuan;LIU Lu;[Objective] To study the factors affecting the surface insulation performance of printed circuit board assembly(PCB), clarify the action mechanisms of ionic residue concentration on the board surface and conformal coating thickness, and provide a basis for process control and reliability design of PCBA in fields such as automotive electronics. [Method] Using IPC-B-25A standard boards as test substrates, specimens with different ionic residue concentrations(0.5, 1.5, 3.0, 5.0, 7.0, 12.0 μg/cm2) were prepared using water-based and no-clean fluxes respectively. Conformal coating was sprayed on some specimens to obtain coated boards with single-side thicknesses of 50, 100, and 150 μm. The effect of ionic residue concentration and conformal coating thickness on the surface insulation performance of PCB was systematically evaluated through water drop electrochemical migration tests, resistance monitoring under alternating temperature(25-65 °C) and at relative humidity ≥93%, and cross-cut coating adhesion tests. [Result] Before spraying conformal coating, an ionic residue concentration exceeding 1.5 μg/cm2 significantly increased the risk of insulation failure, and water-based flux was more likely to induce electrochemical migration than no-clean flux. After spraying conformal coating, the ionic residue concentration had no significant effect on resistance but affected coating adhesion. [Conclusion] To ensure the surface insulation performance of PCB, no-clean flux should be preferred; for unprotected products, the ionic residue concentration should be controlled below 1.5 μg/cm2; the thickness of the conformal coating should be determined comprehensively based on the product's reliability life requirements and the ionic residue concentration, and thicker coatings are required under high ionic residue or high reliability scenarios.
Preparation and properties of highly conductive and oxidation-resistant silver-coated copper powder by electroless plating
XIAO Weihong;ZHANG Nianchun;LIANG Jinkun;SUN Yijie;WANG Yu;[Objective] To address the high cost of pure silver powder and the susceptibility of pure copper powder to oxidation, a silver-coated copper powder with high conductivity and excellent oxidation resistance as a substitute for pure silver powder in electronic pastes was developed. [Method] Micron-sized, spherical high-purity copper powder was firstly prepared by liquid-phase reduction. And then silver-coated copper powder was prepared via a two-step process involving low-temperature displacement plating followed by high-temperature reduction plating. The effects of reductant(i.e. potassium sodium tartrate, formaldehyde, ascorbic acid, and hydrazine hydrate) and reaction temperature(50-80 °C) during reduction plating on the coating effectiveness were studied. The morphology, composition, structure, particle size distribution, oxidation resistance, and electrical conductivity of the obtained powder were characterized using scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD), laser particle size analysis, thermogravimetric analysis(TGA), and powder resistivity testing. [Result] Using potassium sodium tartrate as the reducing agent at 70 °C yielded silver-coated copper powder with a smooth surface and compact coating. The resulting powder(25% Ag by mass) exhibited a uniform particle size distribution and was free of oxide impurities. It demonstrated an oxidation resistance temperature of 280 °C and a low resistivity of 3.45 × 10-5 Ω·cm at 30 MPa, which was very close to that of pure silver. [Conclusion] The silver-coated copper powder prepared by this process combines excellent thermal stability and high electrical conductivity. It effectively addresses the oxidation issue of copper powder and the high cost of silver powder, meeting the performance requirements for conductive fillers in electronic pastes.
Effect of gelatin on cadmium electroplating in chloride-based bath and coating properties
LI Lanchen;WANG Qiong;WANG Shengyong;CHENG Shuyu;ZOU Yujie;LI Yaqiang;LI Ruopeng;LIU Jifei;Dalian Changfeng Industrial Corporation;[Objective] To address the poor bath stability and rough coating surface commonly encountered in chloride cadmium plating, the effect of gelatin as an additive on the bath performance and the overall properties of cadmium coatings were studied, aiming to provide a theoretical basis for preparing highly corrosion resistant Cd coatings. [Method] Cd coatings were obtained by electroplating at 1.0 A/dm2 for 20 min from a basic plating bath composed of 45 g/L CdCl2·2.5H_2O, 240 g/L NH4 Cl, 35 g/L NaCl, and various mass concentrations of gelatin. The effect of gelatin on the cathodic polarization of Cd coating was studied by linear sweep voltammetry(LSV). The throwing power of the bath was studied by Hull cell electroplating test. The microstructure, surface roughness, and wettability of Cd coating were characterized by scanning electron microscopy(SEM), laser confocal microscopy(CLSM), and contact angle measurements. The corrosion resistance of Cd coating in 3.5% NaCl solution was examined by potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS). In addition, the pitting corrosion process of hydrophilic and hydrophobic coatings was simulated using COMSOL Multiphysics. [Result] Gelatin significantly inhibited cadmium electrodeposition, thereby improving the coating microstructure, reducing surface roughness, and enhancing both hydrophobicity and corrosion resistance. When the gelatin concentration was in the range of 1.0-2.0 g/L, the bath showed good throwing power and the Cd coating achieved superior overall performance; in particular, the best corrosion resistance was obtained at 1.0 g/L. Simulation results revealed that the corrosion current density of hydrophobic coating was significantly lower and more uniformly distributed than that of hydrophilic coatings, resulting in shallower corrosion pits. [Conclusion] The addition of an appropriate amount of gelatin to the chloride cadmium plating bath effectively improves the throwing power and significantly enhances the hydrophobicity and corrosion resistance of Cd coatings. This study provides experimental and theoretical support for the selection of additives and the preparation of high-performance coatings in chloride cadmium plating bath.
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