Recovery of copper and tin from stripping tin solution by electrodeposition

In this paper, the method of recycling copper and tin by constant-current and constant-voltage electrolysis from the stripping tin solution of tinned copper wastes was studied. The experimental results show that the elements could be deposited on the cathode in turn by different deposition potentials, therefore, the copper and tin were separated by constant-voltage electrolysis but not constant-current electrolysis. In this study, the influence of anode materials was also investigated. Graphite anode is stable without impurities dissolved into the stripping tin solution, while 316 stainless steel anode is dissolved into Fe2？and Fe3？as anodic corrosion, which could decrease the deposition efficiency of tin. The copper and tin in the stripping tin solution are separated orderly by electrodeposition at different voltages using the graphite anode. The recovery rate of copper is up to 100 % at 2.00 V, while that of tin is 80 % at 3.00 V.     

Chromium electrodeposition from Cr(III) aqueous solutions

The aim of this work is to study an alternative plating process to obtain chromium coatings through electrodeposition from baths containing trivalent chromium, as aqueous solutions of Cr (III) are significantly less dangerous, in terms of human health and environmental impact, as compared to the traditional Cr (VI) baths employed for this purpose. In order to overcome problems regarding the reduction of Cr (III) in aqueous solution, two approaches were followed: i) the possibility of co-depositing chromium along with a second metal, which could help the process of discharge of Cr³⁺ on the substrate; ii) the use of a specific ligand for the Cr³⁺ ion, which can generate easily reducible complexes at the metal-solution interphase. Both approaches led to interesting results: in particular, the co-deposition enabled us to obtain NiCr alloy with a high percentage of chromium, and the deposition using specific complexing agents allowed optimal bath compositions to be developed both for decorative and hard chromium plating.     

Adsorption of thiourea on polycrystalline platinum: Influence on electrodeposition of copper

Although previous works have shown the marked influence of thiourea as an organic additive in electrolyte bulk on copper electrodeposition, a variety of mechanisms could be responsible. The present paper concerns the effect of a thiourea layer adsorbed prior to copper electrodeposition. First evidence of a monolayer on platinum substrate was revealed by X-ray photoelectron spectroscopy. Two different times (15 h and 1 min) for platinum immersion were tested, and it was observed that, even for short times, thiourea is chemisorbed on the surface. Then, effects of thiourea adsorption on copper underpotential deposition (UPD) and overpotential deposition (OPD) processes on polycrystalline platinum were investigated by polarisation curves, atomic force microscopy and X-ray photoelectrons. Thiourea monolayer increases the copper UPD process: in fact the current density of UPD cathodic peak is higher in the presence of thiourea on the platinum surface. However no modifications were observed on the AFM images and on the XPS spectra. For the copper OPD process, the presence of thiourea monolayer inhibits copper deposition: the current density of OPD cathodic peak is lower whatever the immersion time of the platinum substrate in the thiourea solution. Moreover, XPS spectra show that the presence of thiourea modified the oxidation state of the copper coating, as an oxide film is formed more quickly on the surface of the coating.     

Silver electrodeposition from air and water-stable ionic liquid: An environmentally friendly alternative to cyanide baths

The influence of temperature on the kinetics and the morphology of silver deposits obtained from an air and water-stable ionic liquid (the 1-butyl-3-methyl imidazolium tetrafluoroborate) was studied by means of cyclic voltammetry and chronoamperometry. The nucleation and growth mechanisms have been investigated and the effect of temperature evaluated up to 200 °C. Dense, pure and very thin (about 0.3 μm) silver coatings, with decorative properties, have been obtained on commercial copper electrodes at different temperatures. The characterization of the deposits morphology has been performed by visual investigation and SEM microscopy. Data about thickness were acquired by Calotest® measurements. The deposits result constituted by pure silver as determined by combination of EDX microanalysis and Auger Electron Spectroscopy (AES). The deposition method promises to be a new, environmentally friendly, method for silver electrodeposition which is the reason for the absence of cyanide and volatile toxic solvents in the electroplating bath.     

Fabrication of Pd-Fe nanowires with a high aspect ratio by AAO template-assisted electrodeposition

In this study, vertically oriented Pd_0.86Fe_0.14 nanowires have been fabricated using an anodized aluminum oxide (AAO) template by direct voltage electrodeposition at room temperature. AAO template-assisted electrodeposition of Pd-Fe was carried out in Pd(NH₃)₂Cl₂:FeSO₄·7H₂O solution. The AAO template and the Pd_0.86Fe_0.14 nanowires were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) methods and X-ray diffraction (XRD). It was observed that the Pd_0.86Fe_0.14 nanowires were approximately 65 nm in diameter and 10 μm in length with an aspect ratio of 153 in a relatively large area of about 4 cm². The nucleation rate and the number of atoms in the critical nucleus are determined from the analysis of current transients.     

Electrochemical effect of Copper Gleam additives during copper electrodeposition

Electrochemical nano and micro fabrication by flow and chemistry is a maskless micro-patterning technology that uses an acid-free and low ion concentration electrolyte. However, the effects of additives on the electrochemical behaviour of this type of electrolyte are still unknown; hence, their role during micro- and nano-fabrication is unpredictable. This study reports the effect of a suppressor (Copper Gleam B), an accelerator (Copper Gleam A) and a promoter (Cl^?) on the electrochemical behaviour of copper reduction. The three additives, when employed separately, were found to increase cathode polarisation. The combination of Copper Gleam B and Cl^? showed strong inhibition, particularly in the diffusion-limited region. The addition of Copper Gleam A to the Copper Gleam B–Cl^? mix increased the limiting current and suggested plating acceleration. These effects are interpreted in terms of the adsorption–desorption behaviour of the additives on the cathode surface.     

Linear sweep voltammetry of the electrodeposition of copper from a methanesulfonic acid bath containing a perfluorinated cationic surfactant

The influence of a perfluorinated, cationic surfactant, DuPont™ ForaFac® 1098, on the electrodeposition of copper from a CH₃SO₃H bath was investigated. The background electrolyte contained 0.005 mol dm^− 3 hydroquinone and 12.5vol.% (1.93 mol dm^− 3) methanesulfonic acid, surfactant (0.002 to 0.12 vol.%) and copper ion (0.02 to 0.5 mol dm^− 3) at 23 °C. The effects of electrode rotation speed, surfactant concentration and copper ion concentration were investigated. Linear sweep voltammetry was used to identify the charge transfer, mixed control and mass transport control regions. Changes in the limiting current density, copper nucleation potential and hydrogen evolution potential are discussed. The shift in copper nucleation potential was also investigated as a function of the surfactant and copper ion concentrations. Copper was electrodeposited, at a constant potential, onto a rotating cylinder electrode and the surface morphology was characterised using scanning electron microscopy.     

Investigation of Sn-Zn electrodeposition from acidic bath on EQCM

Tin-zinc (Sn-Zn) alloy with low tin content was deposited on gold electrode and steel substrate with use of chronoamperometric technique from an acidic bath. In order to evaluate coating efficiency of Sn-Zn alloy in 0.5 M NaCl solution, open circuit potential-time curve (E_OCP-t), polarization curves, mass change of the electrode (Δm-t) using quartz crystal microbalance (QCM) were compared to those of pure Sn and Zn coatings. Anodic stripping measurements were carried out simultaneously with the mass loss of the deposit. Scanning electron microscopy (SEM) and energy dispersive X-ray spectra (EDS) analysis were performed to characterize the surface morphology. Anodic stripping experiment and EDS analysis indicated that Sn, Zn, and SnO₂ formed on the electrode surface when Sn-Zn was coated from acidic bath. Furthermore, local mapping demonstrated homogeneous distribution of Sn and Zn atoms throughout the surface.     

Influence of bath concentration and pH on electrodeposition process of ternary Zn-Ni-Mo alloy coatings

The influence of bath pH and also citrate and molybdate concentration, on the electrodeposition process of ternary Zn-Ni-Mo alloy coatings has been examined. The occurrence of the particular forms of the metal-citrate complexes in the electrolytes was analysed using UV-VIS spectroscopy and on the basis of the stability constants of the complexes. In the solutions with lower pH (4·5 and 5·7), in which free metal ions and ZnHCit^? and NiHCit^? complexes predominate, anomalous codeposition of nickel with zinc took place. In electrolytes with higher pH, containing excess of citrate, in which all the metal ions occur in the form of citrate complexes, and about 20% of the Zn²⁺ and Ni²⁺ ions form a ZnNiCit₂^4? mixed complex, the codeposition changes from anomalous to normal. The percentage of Mo in the alloy increases with the increase in concentration of uncomplexed MoO₄^2? ions in the solution. Alloys with much higher Mo content may be obtained from the bath in which preferential deposition of nickel (normal codeposition) takes place.     

Corrosion properties of micro- and nanocomposite copper matrix coatings produced from a copper pyrophosphate bath under pulse current

The aim of this work was the deposition of copper matrix composites under direct and pulse current at different frequencies and the evaluation of their protective properties, in the frame of the research domain of the production of metal matrix composite coatings.The deposits were produced using copper pyrophosphate bath in which 20 g/l of either micro- (mean diameter 2 μm) or nano- (mean diameter 45 nm) SiC particles have been added. A squared current waveform was used with the frequencies 0.01, 0.1, 1, and 10 Hz for the pulse current deposition.The microstructure of all deposits, both on the top surface and in cross section, was studied by Scanning Electron Microscopy. The SiC content was evaluated by EDXs in the case of the micro-composite deposits and by Glow Discharge Optical Emission Spectroscopy for the nanocomposite ones. The protective properties were examined by potentiodynamic measurements in different corrosive environments and by salt spray exposure combined with Electrochemical Impedance Spectroscopy measurements.Both the nanoparticles incorporation and the use of pulse current lead to a noticeable grain refinement and thus to a corrosion resistance increase. The nanocomposite deposits present the highest resistance to both uniform and localized corrosion, strongly correlated to their compact structure. The micro-composite deposits produced under direct current present gaps between the particles and the copper matrix, which lower the corrosion resistance. The use of the pulse current managed to partially close these gaps and increase the corrosion resistance to values similar to those of the pure copper deposits.     

Electrochemical aspects of deposition and characterisation of zinc coating produced in presence of 1,2-diaminopropane in sulphate bath

Abstract

The effect of 1,2-diaminopropane addition on zinc electrodeposition was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Adding 1,2-diaminopropane into the electrodeposition bath increased the zinc ion discharge potential. Analysis of chronoamperograms in the absence and presence of 1,2-diaminopropane indicated that the progressive nucleation is predominant in both cases. Scanning electron microscopy analysis showed that the zinc coating obtained in the presence of 1,2-diaminopropane is more homogenous in appearance and lower in crystallite size. By inhibiting the growth of (00·2) planes, 1,2-diaminopropane also affected the texture of the zinc deposit. Potentiodynamic polarisation readings in deaerated 5%NaCl solution indicated that the corrosion resistance of the zinc deposit is slightly improved in the presence of 1,2-diaminopropane in the bath.     

Effect of additive concentration during copper deposition using EnFACE electrolyte

Copper deposition from solutions using high concentration of acid, metal ions and polyethylene glycol (PEG), and bis-(3-sulphopropyl) disulphide (SPS) and chloride ions (Cl^–) is well known. A recent maskless micropatterning technology, which has the potential to replace the traditional photolithographic process, called EnFACE, proposed using an acid-free, low metal ion solution which is in direct contrast to those used in standard plating technology. In this work copper has been deposited using both standard electroplating solutions and those used in the EnFACE process. In the standard electrolyte 0.63 M CuSO₄ and 2.04 M H₂SO₄ has been used, along with Gleam additives supplied by Dow Chemicals. For the Enface electrolyte, copper deposition has been carried out without any acid, and with different concentrations of additives between 17% - 200% of those recommended by suppliers. 25?µm of metal has been plated on stainless steel coupons as suggested by ASTM, peeled off and subjected to ductility and resistance measurements. Scanning electron microscopy and electron back scatter diffraction have been carried out to determine the deposit morphology. It was found that copper deposits obtained from acid-free solutions containing low concentration of metal ion and additives produced copper deposits with properties which are comparable to those obtained from standard electrolytes. The optimum additive concentration for the EnFACE electrolyte was 50% of the supplier recommended value.     

锌镍合金的异常共沉积与正常共沉积的转变

讨论了在电镀锌镍(Zn-Ni)合金过程中由异常共沉积转变为正常共沉积的条件及原因.提出了温度和镀液的组成与转变电流密度的关系以及阴极电位对合金镀层成分的影响.     

Process of pulse electrodeposition nanocrystalline chromium from trivalent chromium bath

Nanocrystalline chromium coating was prepared by pulse electrodeposition from trivalent chromium bath containing carboxylate-urea as complexing agent. The effects of electrodeposition parameters such as current density, bath temperature and solution concentration on the thickness and electrodeposition velocity of Cr deposited films were investigated. The crystallographic structures, morphology and chemical composition of Cr deposited films were analyzed by means of XRD, SEM and EDS. The results indicate that the deposited films with thickness up to 11.2 μm possess a smooth and clean appearance, and the grain size is less than 100 nm. The coating is pure chromium and the Cr deposit has face-centered cubic （fcc） structure and exhibits a （210） growth preference. Both the electrodeposition velocity and thickness exist maximum under different concentration complex agents, ureas, acetates, different temperatures and current densities. Compared with direct current electrodeposition, the thicker coating and finer grains can be obtained at lower temperature and current density by pulse electrodeposition. The electrodepostion velocity is about 0.24 μm/min, which is faster than that by direct current electrodeposition. In l mol/L H2SO4, 3.5% NaCl and 10% NaOH solution, corrosion potential of Cr pulse-deposited film is about 100 mV higher than that of direct current. Corrosion and passivation current densities are lower and the nanocrystalline exhibits better corrosion resistance.     

十二烷基硫酸钠（SDS）对铜电沉积行为的影响

在酸性体系中采用阴极扫描伏安和计时电流等电化学测试方法,研究添加十二烷基硫酸钠（SDS）对铜电沉积过程的影响机理。结果表明：SDS的添加使沉积电位正移,降低了阴极极化。SDS浓度低于临界胶束浓度1g/L时,铜的成核弛豫时间延长,形核速率降低。SDS浓度高于临界胶束浓度时,形成SDS球状胶束,铜的成核弛豫时间减少,形核速率加快。铜晶核形成过程符合Scharitker?Hill 三维成核/生长机制,当SDS为1g/L时,在-0.2V的低过电位区,铜结晶按渐进成核方式进行,在-0.23--0.28V的高过电位区,铜结晶按瞬时成核方式进行。而当SDS为0.5g/L时,铜在-0.2V--0.25V的低电位区和在-0.28V的高电位区均符合渐进成核。     

Effect of direct current and pulse plating parameters on tin whisker growth from tin electrodeposits on copper and brass substrates

Abstract

Electroplated tin finishes are widely utilised in the electronics industry due to their advantageous properties such as excellent solderability, electrical conductivity and corrosion resistance. However, the spontaneous growth of tin whiskers during service can be highly deleterious, resulting in localised electrical shorting or other harmful effects. The formation of tin whiskers, widely accepted as resulting from the formation of compressive stresses within the electrodeposit, has been responsible for a wide range of equipment failures in consumer products, safety critical industrial and aerospace based applications. The numbers of failures associated with tin whiskers is likely to increase in the future following legislation banning the use of lead in electronics, the latter when alloyed with tin, being an acknowledged tin whisker mitigator. Using a bright tin electroplating bath, the effect of process parameters on the characteristic structure of the deposit has been evaluated for deposition onto both brass and copper substrates. The effect on whisker growth rate of process variables, such as current density and deposit thickness, has been evaluated. In addition, the effect of pulse plating on subsequent whisker growth rates has also been investigated, particularly by varying duty cycle and pulse frequency. Whisker growth has been investigated under both ambient conditions and also using elevated temperature and humidity to accelerate the growth of whiskers. Studies have shown that whisker formation is strongly influenced by pulse plating parameters. Furthermore, increasing both current density and thickness of the deposit reduce whisker growth rates. It is also observed that whisker formation is greatly accelerated on brass substrates compared with copper. The basis for this observation is explained.     

Electrochemical and transport properties of ethaline containing copper and tin chloride

Electrochemical and transport properties were measured for hydrated chloride salts of copper and tin in ethaline, which is a 1∶2 ratio of choline chloride and ethylene glycol. Density, viscosity and conductivity for ethaline melts with different salt concentrations have been measured for temperatures between 293 and 328 K. The change in formal potential with changing metal ion concentration has been determined to evaluate changing speciation in the ionic liquid. Cyclic voltammetry has been carried out to ascertain the reduction potential and diffusion coefficient of the reacting species. For pure ethaline the density was found to decrease by <5% with increase in temperature. On the other hand, the viscosity was found to decrease and conductivity was found to increase by 65% over the same temperature range. The inclusion of metal salts in ethaline had negligible effect on these parameters. Potential measurements showed that copper was reduced through a two-step mechanism and Sn was reduced via a two electron transfer route. The diffusion coefficient values for Cu²⁺ and Sn²⁺ species were 1·22×10^?11 and 1·96×10^?11 m² s^?1 respectively.     

The effect of adatoms on the corrosion rate of copper

On the premises that corrosion is a surface process and adatoms modify the electronic states of the surface, the influence of Zn, Sn, S, I, F, Ta, Sb, Ti, Bi and Cr adatoms on the corrosion rate of copper was investigated. Adatoms were adsorbed at open-circuit from a solution containing 1.0×10⁻² mol l⁻¹ of the ions of the adatom element. The coverage of the adatoms at the surface was calculated by integration of the area under one of the peaks on the voltammogram of the copper electrode before and after dosing the electrode with the adatom. A significant difference in adsorbability of the adatoms at copper surface was observed. This difference was inter alia attributed to atomic size, crystallographic and kinetic effects. The surface properties were characterized by cyclic voltammetry, and for selected systems by SEM and electron microprobe. Corrosion of the surface in presence and in absence of the adatoms was followed by weight-loss method while surface oxidation, ‘surface corrosion’ was investigated by cyclic voltammetry and by electrochemical polarization techniques. The results showed that the nonmetals (F, S and I) markedly enhanced the rate of corrosion; Cr, Ta, Sb, Bi, Ti, Sn slightly enhanced the rate of corrosion of copper. Zinc, however, was the only element which decreased the rate of corrosion.     

Observations on the uniformity of immersion tin coatings on copper

The development of chemical tin coatings by a replacement reaction Cu+Sn²⁺Cu²⁺+Sn from hydrochloric acid based and methanesulphonic acid based baths on the inner surface of a copper tube was studied by transmission electron microscopy and scanning electron microscopy in order to explore the factors influencing the uniformity of tin coatings. Despite the fact that tin coatings develop in different ways in studied baths, uniform coatings are equally plated from both these baths when the substrate surface is clean and smooth. However, differences in the surface-sensitivity, i.e. the dependence of coating uniformity on the substrate surface condition, of plating baths materialise when plated on irregular or improperly cleaned substrate. A hydrochloric acid based bath may yield non-uniform coatings on irregular or improperly cleaned substrate, since large-sized grains develop immediately after coating initiation. These large grains are suggested to orientate to follow the contours of impurity particles or surface irregularities introducing misalignment in grain columns and, thus, non-uniformity into coatings. In contrast, a methanesulphonic acid based bath is still able to produce uniform tin coatings on contaminated or rough surfaces, as the coating is proposed to accommodate to substrate surface irregularities by the build-up of a nanocrystalline zone at the early stages of tin coating deposition. Sulfur-containing elements in this methanesulphonic acid based plating bath play the central role in the nanocrystalline layer formation.     

Electrodeposition of copper-zinc from an alkaline bath based on EDTA

The electrodeposition of copper-zinc on 1010 steel from a non-cyanide alkaline electrolyte based on EDTA (ethylenediaminetetraacetic acid, disodium salt) — alkaline with various proportions of copper and zinc ions, was investigated. The complexation of copper and zinc by EDTA stabilized the solution. The deposition potential and the composition of the Cu-Zn bath were shown to influence the composition, morphology and phase composition of the Cu-Zn deposits. Scanning electron microscopy analysis showed that the best conditions to obtain smooth Cu-Zn deposits were at − 1.45 V, with Cu70-Zn30 and Cu50-Zn50 baths, and at − 1.60 V, with Cu30-Zn70. Besides being smoother than others, these deposits were golden in colour. Energy-dispersive X-ray spectroscopy analysis showed that a Zn content above 60 wt.% in the Cu-Zn deposits was achieved from the last bath, at − 1.45 V. X-ray diffractograms of the Cu-Zn deposits produced at -1.45 V, from Cu70-Zn30, Cu50-Zn50 and Cu30-Zn70 baths, indicated the occurrence of phases Cu_0.61Zn_0.39 and Cu, CuZn, Cu₅Zn₈ and Cu, CuZn, Cu₅Zn₈, CuO, Cu_0.61Zn_0.39, respectively. For the Cu30-Zn70 bath at − 1.60 V, Cu, CuZn, Cu₅Zn₈, and CuO phases were observed.