Influence of the interaction between chloride and thiourea on copper electrodeposition

The interaction between chloride and thiourea in copper electrodeposition in a sulfate-plating bath was investigated. The sole addition of thiourea to the bath increased the polarization of the electrode potential during copper deposition, leading to very fine and smoothly structured deposit but with microscopic nodules distributed over the surface. When chloride was added to a plating solution containing thiourea, the copper deposition mechanism was changed, showing a depolarization of the electrode potential, and the copper deposits were found to have a relatively rougher microstructure, but without the formation of microscopic nodules. However, rough deposit surfaces having no distinct pattern were formed at the macroscopic scale. Observations of roughening evolution show that the rough surface was initiated from small holes formed across the deposit surface during the initial stage of deposition that eventually developed into visibly rough deposits. The copper deposition inside these holes and at other areas was expected to undergo different deposition mechanisms. Copper deposition in the areas that ultimately developed into holes was almost totally inhibited by the thiourea–Cu(I)–chloride complex film, not just in the grain growth process, but over practically the entire electrodeposition process. Conversely, copper deposition occurred in other areas under conditions where nucleation proceeded, but grain growth was inhibited to produce a fine, homogeneous microstructure. An uneven deposit surface that had different microscopic structures in different areas was then formed. The structure of the thiourea–Cu(I)–chloride film was strongly affected by the current density and appeared to break down completely if sufficiently high current density was applied to yield a fine and homogeneous microstructure that was also macroscopically smooth.     

Effect of additives and pulse plating on copper nucleation onto Ru

The impact of organic additives and pulse-plating parameters on the initial stages of copper electrodeposition on Ru is characterized. Microscopy is used to observe 7-15 nm thick Cu deposits, prior to complete coverage of the substrate. Because the nucleus density is very high for the conditions studied here, the counting of individual Cu islands is difficult and an alternative method to analyze the images is presented. Results are compared for different additives for continuous plating and pulse-plating conditions. Pulse plating has a significant impact on the nucleus density. Replacement of Cl⁻ ions with Br⁻ ions of the same concentration yields an increase in the nucleus density at the same current density. A PEG-PPG-PEG block copolymer, when used instead of PEG as a suppressor, appeared to result in high nonuniformity in particle size.     

Evaluation of cysteine as environmentally friendly corrosion inhibitor for copper in neutral and acidic chloride solutions

The efficiency of cysteine as a non-toxic corrosion inhibitor for copper metal in 0.6 M NaCl and 1.0 M HCl has been investigated by electrochemical studies. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy “EIS” were used to study the effect of cysteine on the corrosion inhibition of copper. Inhibition efficiency of about 84% could be achieved in chloride solutions. The presence of Cu²⁺ ions increases the inhibition efficiency to 90%. Potentiodynamic polarization measurements showed that the presence of cysteine in acidic and neutral chloride solutions affects mainly the cathodic process and decreases the corrosion current to a great extent and shifts the corrosion potential towards more negative values. The experimental impedance data were analyzed according to a proposed equivalent circuit model for the electrode/electrolyte interface. Results obtained from potentiodynamic polarization and impedance measurements are in good agreement. Adsorption of cysteine on the surface of Cu, in neutral and acidic chloride solutions, follows the Langmuir adsorption isotherm. The adsorption free energy of cysteine on Cu (−25 kJ mol⁻¹) reveals a strong physical adsorption of the inhibitor on the metal surface.     

Gold dissolution in acidic thiourea and thiocyanate solutions

Gold dissolution in acidic solutions containing thiourea (Tu) and thiocyanate was studied using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and surface enhanced Raman spectroscopy (SERS). A synergistic response found in that mixed ligand system promoted a higher dissolution rate than either lixiviant alone. The passivation of gold occurs in a Tu only solution, but when thiocyanate is mixed with Tu, passivation is significantly alleviated. The dissolution rate of gold in the mixed lixiviant system increases with increasing Tu and thiocyanate concentration. Results from LSV and EIS indicate that gold dissolution is controlled by a combination of charge transfer and diffusion in the mixed lixiviant system. The optimum concentration for Tu and thiocyanate is about 5 mM and 0.05 M, respectively for the rate of gold dissolution. SERS results suggest a possible formation of a mixed ligand complex involving the interaction of Au(Tu)₂⁺ and SCN⁻. Further study is necessary to identify the mixed ligand complex.     

硫脲对聚甲基丙烯酸甲酯基材化学镀铜的影响

以硫脲为添加剂、硫酸铜为主盐、次磷酸钠为还原剂,在聚甲基丙烯酸甲酯(PMMA)基材表面进行化学镀铜。研究了添加不同质量浓度(0.10、0.25、0.50、0.75和1.00 mg/L)的硫脲对铜沉积速率、镀层导电性和结合力以及化学镀铜中氧化还原反应的影响,并通过扫描电镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)等方法分别对镀层微观形貌、组成成分、晶体结构进行了表征。结果表明,硫脲的加入主要影响铜(111)晶面的生长,能有效提高镀层与基体之间的结合力,但对镀层成分无太大影响。随着硫脲加入量的增大,铜沉积速率和镀层导电性先减后增,而镀铜速率主要由阴极还原过程控制。适宜的硫脲添加量为0.50~0.75 mg/L,此时铜沉积速率相对较低,所得镀层晶粒尺寸较小,表面电阻为40~50 mΩ/cm2,镀层结合力1~2级。     

Voltametry and EQCM study of copper oxidation in acidic solution in presence of chloride ions

Cyclic voltametry experiments coupled with electrochemical quartz crystal microbalance (EQCM) measurements showed the corrosion mechanism of electrodeposited copper in presence of chloride ions. The oxidation of copper in acidic solution containing high concentration of Cl⁻ begins with formation of Cu⁺ ions. The Cu⁺ concentration at the vicinity of the electrode increasing, the small solubility product of CuCl is then exceeded, leading to a CuCl precipitation on the gold covered quartz crystal used as working electrode. For highest anodic potentials, the oxidation of electrodeposited copper or CuCl precipitate phases could occur. A combination with structural techniques like SEM, EDAX, AFM and DRX gives insight into the morphology and the nature of these CuCl precipitates.     

Effect of chloride ions on immersion plating of copper onto porous silicon from a methanol solution

The effect of chloride ions (Cl⁻) during the immersion plating of copper onto porous silicon (PS) from a methanol (MeOH) solution has been studied. The presence of Cl⁻ in the Cu²⁺ solution was found to slow down the rate of copper deposition, as confirmed by inductively coupled argon plasma emission spectroscopy and X-ray photoelectron spectroscopy measurements. The threshold concentration of Cl⁻ at which the deposition of copper is very severely diminished was found to be 0.1 M. The inhibition effect is discussed on the basis of the rest potential values of PS and polarization curve measurements. They revealed that the rest potential of PS upon dipping in these solutions appears to direct the metal deposition. Current density-potential curves show that at Cl⁻ concentrations higher than 0.1 M, the reduction of Cu ions proceeds in two steps; the reduction of Cu(II) to Cu(I) followed by the reduction of Cu(I) to Cu(0). This suggests that Cu(I) species in MeOH solution can be stable over a certain potential range and this stability of Cu(I) is responsible for the inhibition of metal deposition. Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) were also performed to investigate the structural changes and characterizations of PS samples after the plating process.     

Enhancement of filling performance of a copper plating formula at low chloride concentration

In this work, microvia filling was performed by copper electroplating using two plating formulas with and without a leveler at a low concentration of chloride. The base plating solution contained CuSO₄, H₂SO₄, polyethylene glycol (PEG), bis (3-sulfopropyl) disulfide (SPS) and Cl⁻. When the Cl⁻ concentration was lower than 30 ppm, the plating formula without a leveler became dead for bottom-up filling, resulting in conformal deposition. The addition of 1 ppm Alcian Blue, used as a leveler, could effectively recover the filling performance of the plating formula with low chloride concentration. Electrochemical analyses revealed possible mechanisms. The results demonstrate that the usage of Alcian Blue can widen the operation window of chloride concentration, since it can assist PEG in competing with SPS in adsorption at low chloride concentration.     

Recovery of nickel,cobalt, copper and zinc in sulphate and chloride solutions using synergistic solvent extraction

A number of synergistic solvent extraction (SSX) systems have been developed to recover nickel, cobalt, zinc and copper from sulphuric and chloride leach solutions by the solvent extraction team of CSIRO, Australia. These in-clude (1) Versatic 10/CLX50 system for the separation of Ni from Ca in sulphate solutions, (2) Versatic 10/4PC system for the separation of Ni and Co from Mn/Mg/Ca in sulphate solutions, (3) Cyanex 471X/HRJ-4277 system for the separation of Zn from Cd in sulphate solutions, (4) Versatic 10/LIX63 system for the separation of Co from Mn/Mg/Ca in sulphate solutions, (5) Versatic 10/LIX63/TBP system for separation of Ni and Co from Mn/Mg/Ca in sulphate solutions, (6) Versatic 10/LIX63 system for the separation of cobalt from nickel in sulphate solutions by difference in kinetics, (7) Cyanex 272/LIX84 system for the separation of Cu/Fe/Zn from Ni/Co in sulphate solutions, (8) Versatic 10/LIX63/TBP system to recover Cu/Ni from strong chloride solutions, and (9) Versatic 10/LIX63 system to separate Cu from Fe in strong chloride solutions. The synergistic effect on metal separation and efficiency is presented and possible industrial applications are demonstrated. The chemical stability of selected SSX systems is also reported.     

酸性氯化钾镀锌故障分析

在对某铁件制品进行酸性氯化钾镀锌过程中,镀层出现低位发雾,而且有白斑,在硝酸出光及钝化后依然存在。运用鱼骨分析法、排除法等方法分析发现,该故障产生原因是由于镀件在防锈水中浸泡时形成的一层氧化膜的缘故。针对此问题,经过反复实验,对原工艺流程进行了改进,增加了一道98%浓硫酸浸泡(3～10s)工序,从而避免了该故障的发生。     

Localized electrochemical deposition of micrometer copper columns by pulse plating

Micrometer copper column fabrication by localized electrochemical deposition (LECD) was investigated in this study. To obtain columns with uniform diameter, compact structure and a smooth surface, LECD conducted in pulse current (PC) mode was better than that conducted in direct current (DC) mode. A micro-reference electrode was used to monitor the potential at the LECD site. Measurement of this potential permitted estimation of the local copper ion concentration resulting from their dynamic consumption by electrochemical reduction and their supply by mass transport. The electroplating current was measured in order to evaluate the rate of electrochemical reduction. The mass-transfer rate of copper ions was estimated using a theoretical calculation based on diffusion. The surface morphology and internal structure were significantly affected by this local concentration, which was in turn governed by the electrical voltage and the duty cycle employed. The mechanism for LECD conducted in PC mode is discussed.     

表面活性剂对铜粉表面酸性化学镀银的影响

在酸性镀银体系中,研究了乙醇、十二烷基硫酸钠(SDS)、十二烷基苯磺酸钠(SDBS)、聚乙二醇6000(PEG6000)、烷基酚聚氧乙烯醚(OP-10)、聚乙烯吡咯烷酮(PVP)等表面活性剂对铜粉表面化学镀银的影响,初步探讨了其作用机理。结果表明,PVP的加入能有效改善铜粉在镀银过程中的分散,镀层的连续性较好。PVP的质量浓度为0.030 g/L时获得的银包铜粉为银白色,电阻最小,松装密度为0.58 g/m L。     

酸性镀铜工艺硫酸过量引起的故障分析

工业生产中,硫酸的过量添加会造成酸性镀铜工艺阳极钝化、槽电压升高、工作电流下降.本文讨论了硫酸对硫酸铜溶解度的影响,发现水溶液中硫酸含量超过50 g/L后硫酸铜的溶解度急剧下降.当硫酸含量过高时,随着电镀过程的进行,CU<'2+>在阳极表面层的浓度不断升高,引起硫酸铜晶体在阳极表面析出,使阳极钝化,导致无法正常生产.     

比浊法测定酸性镀铜液中的氯离子

利用比浊法,以OP乳化剂作为稳定剂测定酸性镀铜液中的氯离子。研究了测量波长、酸度、乳化剂浓度、硝酸银浓度对测量结果的影响。在450nm波长下,氯离子浓度在8～80ug/10mL范围内遵守比耳定律,该方法准确度和精密度高,能满足实际生产的要求。     

酸性镀铜镀液中氯离子的分析测定及调整方法

概括了酸性镀铜液中氯离子的多种分析测试方法,包括络合滴定法、硝酸汞滴定法、比浊法、离子色谱法和共振散射光谱法等。对实际生产中常用的氯离子的调整方法总结如下:当C l-含量偏低时,可以通过加入氯化钠、盐酸或氯化铜补充;当C l-过量时,则可以加入硝酸银或硫酸银去除。     

印制线路板酸性镀铜整平剂的研究

以N-乙烯基咪唑和1,4-丁二醇二环氧甘油醚为原料合成了一种带聚醚链的整平剂,采用FT-IR和<'1>H NMR对其结构进行了表征.对由此整平剂与聚二硫二丙烷磺酸钠(SPS)和聚乙二醇(PEG-6000)组成的添加剂体系与市售整平性能较好的添加剂的阴极极化曲线、铜镀层表面形貌和镀液均镀能力作了对比.结果表明,含此整平剂...     

Pulsed electrodeposition of bismuth telluride films: Influence of pulse parameters over nucleation and morphology

Pulsed electrodeposition methods were applied to the preparation of bismuth telluride films. Over the potential ranges from −170 mV to −600 mV, the formation of Bi₂Te₃ nuclei proceeded through a three-dimensional instantaneous nucleation mode. The nuclei densities for several values of potential were ranged between ∼10⁶ nuclei cm⁻² and ∼10⁸ nuclei cm⁻². For a pulsed galvanostatic electroplating, the best covering percentage and a stoichiometry close to the desired Bi₂Te₃ were obtained with the parameters t_on, t_off and J_c, respectively, equal to 10 ms, 1000 ms and −100 mA cm⁻².     

化学镀铜原理、应用及研究展望

化学镀铜技术主要用作印制线路板孔金属化和塑料电镀,其镀层具有良好的延展性、导热性和导电性,介绍了化学镀铜的应用范围与发展,强调了化学镀铜预处理的必要性及要注意的几个方面：应用易清洗的油脂作防锈剂,低碳钢件用阳极电解除油,酸洗除油与碱性除油互补等。介绍了化学镀铜的一些常用体系及其主要组分。讨论了添加剂的影响,对非金属表面化学镀铜的研究进展进行了报道,提出了化学镀铜今后的研究重点。     

2-巯基苯并噻唑对化学镀铜的影响

以甲醛为还原剂,研究了2-巯基苯并噻唑(2-MBT)对ABS塑料化学镀铜沉积速率、铜镀层表面形貌、纯度、平整度及晶型的影响.化学镀铜的工艺条件为:CuSO4·5H2O 10g/L,EDTA-2Na30g/L,HCHO3mL/L,PEG-10002mg/L,2-MBT0～2mg/L,温度70℃或40℃,pH 12.5,时...     

The effect of thiourea,LIX65N and chloride ion on the morphology of electrowon copper

The effect of thiourea, LIX65N (a common organic extractant for copper) and chloride ion on the morphology of electrodeposited copper under different conditions is reported. The deposit morphology was assessed by optical microscopy techniques, scanning electron microscopy and X-ray diffraction measurements. The importance of controlling the concentration of these additives in electrowinning copper from electrolytes obtained from a solvent extraction separation process is indicated.