High-rate electrochemical copper deposition on bars

The industrial electrodeposition of copper from cupric acid sulphate baths is typically carried out at approximately 3 kA m^?2. A much higher rate of copper deposition is necessary to improve this electroplating process significantly. To achieve this higher rate for the deposition of copper on a round bar, the solution flow is directed normal to the axis of a round bar. The current efficiencyη _Cu for copper deposition on a round bar, 9 mm in diameter, has been determined from 1 M H₂SO₄+1 M CuSO₄ bath as a function of current density, solution flow rate and temperature. A set of relations has been proposed for calculating the current efficiencyη _Cu for a broad range of parameters.     

Fabrication of superhydrophilic surface on copper substrate by electrochemical deposition and sintering process

Superhydrophilic surfaces were fabricated on copper substrates by an electrochemical deposition and sintering process. Superhydrophobic surfaces were prepared by constructing micro/nano-structure on copper substrates through an electrochemical deposition method. Conversion from superhydrophobic to superhydrophilic was ob-tained via a suitable sintering process. After reduction sintering, the contact angle of the superhydrophilic sur-faces changed from 155° to 0°. The scanning electron microscope (SEM) images show that the morphology of superhydrophobic and superhydrophilic surfaces looks like corals and cells respectively. The chemical composi-tion and crystal structure of these surfaces were examined using energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The results show that the main components on superhydrophobic surfaces are Cu, Cu2O and CuO, while the superhydrophilic surfaces are composed of Cu merely. The crystal structure is more inerratic and the grain size becomes bigger after the sintering. The interfacial strength of the superhydrophilic surfaces was investigated, showing that the interfacial strength between superhydrophilic layer and copper substrate is considerably high.     

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.     

Optical and electrochemical study of underpotential deposition of bismuth on gold electrode

The underpotential deposition of Bi on Au has been investigated by specular reflectance spectroscopy and linear sweep voltammetry. The spectral dependance of ΔR/R caused by Bi adatoms has been determined and compared with the calculated spectrum. A satisfactory agreement between experimental and calculated spectra was found. ΔR/R values have been used to determine the surface concentration of Bi_ad which then has been used to calculate the electrosorption valence of Bi_ad. It has been found that γ_Bi = 2.6. The optical evidence of interaction of Bi ions with gold oxide has been obtained.     

An investigation of copper interconnect deposition bath ageing by electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy was performed on copper interconnect plating baths during deposition to study their degradation (ageing). A kinetic-based model was used to simulate the impedance scans by taking into account the organic additives in the reaction mechanism. Also, an equivalent circuit analysis was performed to characterize the deposition process in terms of resistive and capacitive components. Experimental results for two chemistries indicate that the low-frequency impedance relaxations change as the plating bath ages. Impedance diagrams calculated from the kinetic model resulted in a reasonable fit with the experimental impedance scans. In addition, the low-frequency capacitive and inductive impedance loop diameters are proposed as parameters to follow bath ageing. From these results, a monitoring method is proposed which could be applied to an industrial production line.     

Morphological and structural studies of nanoporous nickel oxide films fabricated by anodic electrochemical deposition techniques

Porous nickel oxide films are directly deposited onto conducting indium tin oxide coated glass substrates by cyclic voltammetric (CV), galvanostatic, and potentiostatic strategies in a plating bath of sodium acetate, nickel sulfate, and sodium sulfate. By tuning the deposition parameters, it is possible to prepare nickel oxide films with various morphologies and structures. Film formation relies on the oxidation of dissolved Ni²⁺ to Ni³⁺, which further reacts with the available hydroxide ions from a slightly alkaline electrolyte to form insoluble nickel oxide/hydroxide deposits on the substrate. A compact film with particularly small pores is obtained by CV deposition in a potential range of 0.7-1.1 V. A galvanostatically deposited film is structurally denser near the surface of the substrate, and becomes less dense further away from the surface. Interestingly, a potentiostatically deposited film has pores distributed uniformly throughout the entire film. Therefore, for obtaining a uniform film with suitable pore size for electrolyte penetration, potentiostatic deposition technique is suggested. In addition, except for CV deposition, the deposited films resemble closely to cubic NiO when the annealing temperature exceeds 200 °C.     

铝合金表面电解沉积稀土转化膜工艺研究

研究了一种通过电解沉积方法在防锈铝LF21表面上生成铈盐转化膜的工艺,应用正交实验研究了有关因素对成膜过程的影响并获得了最佳的技术参数用极化曲线、交流阻抗和中性盐雾试验等方法测试了该工艺形成膜层的耐蚀性能及其组成一结果表明：经过电解沉积稀土转化膜处理后,防锈铝的阳极腐蚀过程受到了阻滞,自然腐蚀电位负移;与经过化学转化膜处理后相比,其耐蚀性能有显著提高,可通过400h的中性盐雾实验,亲水性能亦有明显提高。     

Enhanced electrocatalytic reduction of aqueous nitrate by modified copper catalyst through electrochemical deposition and annealing treatment

Copper has been intensively investigated as an electrocatalyst for electrochemical reduction of aqueous nitrate. Here we report preparation of Cu electrocatalyst by electrochemical deposition of Cu on Ni foils, annealing treatment to produce nanograins of Cu oxides and electroreduction to form metallic Cu nanograins to enhance the catalytic activities of nitrate reduction. The prepared Cu electrocatalysts were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The electrochemical deposition of Cu on Ni substrates produced different sizes and sharp-edged microcrystal of Cu, and the annealing treatment at 300°C transformed these microcrystals into uniform spheroids of Cu oxides in sizes of 150–350?nm. The potentiostatic electrolysis of aqueous nitrate showed that the annealing treatment improved nitrate reduction efficiency by 4.5 times and 20% at ?0.8 and ?1.4?V versus the saturated calomel electrode, respectively. The rate and Faradaic efficiency for nitrate reduction by modified Cu electrode remained constant within a testing time of 48?h. The results demonstrate that electrochemical deposition on Ni foils and subsequent annealing treatment provide a simple and cost-effective approach to enhance the catalytic activity and stability of a transition metal catalyst.     

A study of electrochemical kinetics of copper deposition under pulsed current conditions

The investigation is concerned with the drop of current efficiency (CE) of copper deposition under pulsed current conditions. A mathematical model which is based on different charge transfer rates between the following two reactions, (1) $$Cu^{2 + } + e \to Cu^ + $$ and (2) $$Cu^ + + e \to Cu$$ has been formulated to describe the behaviour of a Cu/CuSO₄ system under pulsed current conditions on a rotating disc electrode. The results indicate that the CE drops continuously as the difference between the exchange current densities of the two reactions increases. The exchange current densities of Reactions 1 and 2 were estimated to be 0.034 mA cm^?2 and 0.024 mA cm^?2, respectively. Prediction of CE using the mathematical model agreed to within 3.5% with experimental data over a range 80.4–93.7%.     

Electrodeposition of copper from spent Li-ion batteries by electrochemical quartz crystal microbalance and impedance spectroscopy techniques

Information about the copper electrodeposition mechanism at different pH values was obtained using an electrochemical quartz crystal microbalance (EQCM) technique, as well as potentiodynamic, potentiostatic, and electrochemical impedance spectroscopy (EIS) techniques. In agreement with the measurements obtained from the EQCM and potentiostatic experiments, an intermediate Cu⁺ species and a CuO layer are formed. Simultaneous mechanism of direct reduction of Cu²⁺ and copper oxide (CuO) reduction at pH 2.0 and 4.5 occur. The EIS experiment shows a diffusion-controlled process by the presence of a Warburg element, a CPE related to the irregular metallic copper electrodeposition, and a resistance of the electrodeposit.     

Study of the electrochemical deposition of Sn-Ag-Cu alloy by cyclic voltammetry and chronoamperometry

The electrochemical deposition of Sn-Ag-Cu alloy from weakly acidic baths onto glassy carbon electrodes (GCE) was studied by cyclic voltammetry (CV) and chronoamperometry (CA). The properties of the electrodeposits were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometery (EDS) and X-ray diffraction (XRD). Test results indicate that the two cathodic peaks in the CV curves, at −0.6 V and −0.85 V during the forward scan towards the negative potentials, correspond to the irreversible deposition of a solid solution of tin, silver and copper. The underpotential deposition (UPD) of Sn occurs at −0.6 V during the cathodic period and the amount of Ag and Cu in the Sn-Ag-Cu alloy decreases with increasingly negative cathodic potentials. During the forward scan, towards the positive potentials used in CV testing, cathodic peaks at −0.85 V appear in the CV curves for baths containing mixtures of tin salts and triethanolamine (TEA). This corresponds to a reduction of transient complex ions [Sn(TEA)_x]²⁺ on the surface of the cathode. Furthermore, the formation and reduction of [Sn(TEA)_x]²⁺ is a diffusion controlled process. On the surface of the GCE, the actual nucleus growth mechanism of the Sn-Ag-Cu alloy is represented by the progressive nucleation model.     

Effect of electrochemical surface area on electroless copper deposition: Pd nanocubes as new activators

In this study, the electrochemical surface area (ESA) and specific activity are used to obtain a fair comparison of various activators used for electroless copper deposition (ECD). Different sizes (i.e., 27, 48, and 63 nm) of Pd nanocubes (NCs) enclosed by {1 0 0} facets were successfully synthesized for use as new activators. The results of an analysis based on mixed potential theory indicated that the specific activities in terms of deposition current densities for the 27, 48, and 63 nm NCs and 9 nm nanoparticles (NPs) were 0.31, 1.06, 0.93, and 0.13 mA cm^?2_ESA, respectively. From the results of electrochemical quartz crystal microbalance measurements, the specific activities calculated from the mean deposition rates of the 27, 48, and 63 nm NCs and 9 nm NPs were 29.62, 68.72, 54.77, and 9.72 μg cm^?2 s^?1, respectively. A specific activity order of 48 nm NC > 63 nm NC > 27 nm NC > 9 nm NP was obtained. The 48 nm Pd NCs exhibited the maximum activity towards the activation of the ECD bath.     

Influence of deposition temperature on the properties of hydroxyapatite obtained by electrochemical assisted deposition

Surface functionalization of pure titanium (cp-Ti) with hydroxyapatite (HAp) was successfully achieved by means of electrochemical deposition (ED) in a solution containing calcium nitrate and ammonium dihydrogen phosphate. The aim of this study is to evaluate the influence of the deposition temperature on the elemental and phase composition, chemical bonds, morphology, and in vitro electrochemical behaviour in biological simulated media (simulated body fluid - SBF). The roughness and wettability of the developed coatings are also investigated. By increasing the deposition temperature from 50 °C to 75 °C, the HAp coatings present a well-crystalized structure, denser and a nobler behaviour in terms of electrochemical behaviour in SBF at 37 °C. Also, by increasing the deposition temperature from 50 °C to 75 °C, the contact angle has decreased from 76.1° to 27.4°, exhibiting a highly hydrophilic surface. Taking into consideration all the obtained data, electrodeposition of HAp at 75 °C was found preferable when compared to 50 °C. The characteristics of the HAp coatings can be easily adjusted by optimizing the electrochemical deposition parameters and/or controlling specific features like pH, temperature, or ionic concentration of electrolyte, etc.     

Study on electrochemical mechanical polishing process of copper circuit on PCB

As an alternative to conventional chemical mechanical polishing (CMP) for the planarization of copper layers on electronic circuits, the electrochemical mechanical polishing (ECMP) process in alkali-based solution was investigated in this work. The influence of the polishing pad materials on the polishing process was studied, and the hard polyurethane polishing pad was shown to eliminate the “dishing effect”. The polishing conditions, such as the pad rotating speed, concentration of H₂O₂, and the amount of BTA additives were optimized to control the planarization performance. As a result, good planarization uniformity was obtained not only in small scale (30 μm) trenches but also in very large scale (a few mm) patterns with a single step ECMP process.     

Evaluation of nickel deposition by electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy was used to characterize the deposition of nickel from unbuffered acid sulfate electrolytes, from which a wide range of deposit morphologies and current efficiencies are possible. The operating parameters were in the range of 40 to 60 g L^–1 Ni²⁺, 40 to 60 °C, and the pH from 2.0 to 3.5. The resulting impedance spectra for nickel deposition at 20 mA cm^–2 consisted of one or two characteristic loops whose frequency and capacitance were dependent upon the electrowinning conditions and indicative of the resultant deposit morphology. A single high frequency capacitive loop, on the order of 1 kHz, correlated to good quality deposits which were flat, smooth and ductile. The presence of a low frequency loop, on the order of a few hertz, indicated a degraded deposit morphology which showed localized dark, glassy areas and were cracked, curled and brittle. The second loop may be associated with a diffusion controlled component in the reaction mechanism. Deposits of intermediate quality had impedance spectra consisting of both type loops. No apparent trend between the impedance spectra and the deposit current efficiency was determined, but a correlation with deposit quality was clearly established.     

Copper deposition and its replacement by platinum on a gold electrode

The decoration of single crystal gold electrodes with platinum using underpotential deposited copper as an intermediate has been studied in detail. It was found that a significant fraction of the copper is lost in the transfer process from the upd cell to the exchange cell. In addition the surface of the gold is not covered uniformly by the platinum. Nevertheless, acceleration of the electroreduction of oxygen was observed with a loading of 0.14 μg cm⁻². The structure of the decorating layer was studied by scanning electron microscopy and atomic force microscopy.     

Formation of nanocrystalline Zinc on ITO and Silicon substrates by electrochemical deposition

Zn was deposited by means of cyclic voltammetry (CV) and square wave pulsating overpotential (OP) methods on ITO (indium tin oxide) and n-doped silicon (n-Si) substrates from an acetate-based electrolyte at two different temperatures in the absence of additives. The surface morphology of the Zn deposits was studied by scanning electron microscopy (SEM). The preferred orientation and the average size of the Zn electrodeposited particles on n-Si substrates were obtained by X-ray diffraction and the microhardness of the deposits was measured by standard means. The results show that the grain size of the electrodeposits increases as the temperature rises, and on the other hand that the PO method yields smaller grains and higher hardness values compared with those obtained by CV, irrespective of the temperature. Furthermore, in PO conditions a preferential (101) orientation is obtained for the growth of the Zn electrodeposits, but for long deposition times the growth direction is that [100] corresponding to the basal plane (002).     

Fe–Pt magnetic multilayers by electrochemical deposition

A series of magnetically soft/hard bilayers (BL) and multilayers with various sublayer thickness and configurations were prepared by electrodeposition from an alkaline solution using potential modulated waveforms and successive thermal annealing. In the as-deposited conditions the equiatomic layers grow with a face centered cubic FCC structure, and the Fe-rich ones with a body-centered cubic BCC structure. Annealing induces partial transformations of both structures to a L1₀ FCT phase. The coercivity of bilayers after annealing at or above 450 °C shows a maximum when the Fe-rich layer thickness is 10 nm; this configuration yields up to 45% increase in coercivity compared with single layers of 15 nm equiatomic Fe–Pt. Multilayer structures with fixed 5 or 10 nm Fe-rich layers show a coercivity enhancement similar to that of bilayers, suggesting that a bilayer structure is sufficient to facilitate magnetic hardening while minimizing the overall structure thickness. Either BLs or multilayers with 5 nm thick Fe-rich layers show a single phase magnetization behavior, behaving like a rigid magnet; those with 10 nm thick Fe-rich layers show instead a two stage magnetization switching, implying partial exchange decoupling.     

Study and characterization of porous copper oxide produced by electrochemical anodization for radiometric heat absorber

The aim of this work is to optimize the different parameters for realization of an absorbing cavity to measure the incident absolute laser energy. Electrochemical oxidation is the background process that allowed the copper blackening. A study of the blackened surface quality was undertaken using atomic force microscopy (AFM) analysis and ultraviolet-visible-infrared spectrophotometry using a Shimadzu spectrophotometer. A two-dimensional and three-dimensional visualization by AFM of the formed oxide coating showed that the copper surfaces became porous after electrochemical etching with different roughness. This aspect is becoming more and more important with decreasing current density anodization. In a 2 mol L ^-1 of NaOH solution, at a temperature of 90°C, and using a 16 mA cm² constant density current, the copper oxide formed has a reflectivity of around 3% in the spectral range between 300 and 1,800 nm. Using the ‘mirage effect’ technique, the obtained Cu₂O diffusivity and thermal conductivity are respectively equal to (11.5 ± 0.5) 10 to 7 m² s^-1 and (370 ± 20) Wm^-1 K^-1. This allows us to consider that our Cu₂O coating is a good thermal conductor. The results of the optical and thermal studies dictate the choice of the cavity design. The absorbing cavity is a hollow cylinder machined to its base at an angle of 30°. If the included angle of the plane is 30° and the interior surface gives specular reflection, an incoming ray parallel to the axis will undergo five reflections before exit. So the absorption of the surface becomes closely near 0.999999.