Acid Plating Bath Research Articles

Corrosion Resistance of Electroless Ni-Cu-P Ternary Alloy Coatings in Acidic and Neutral Corrosive Mediums

Electroless Ni-Cu-P alloy coatings were deposited on the ordinary steel substrate in an acidic hypophosphite-type plating bath. These coatings were characterized by a scanning electron microscope (SEM) and an X-ray diffraction. The micrograph shows that coating presents a nodular aspect and is relatively homogeneous and very smooth. The EDX analysis shows that the coating contains 12 wt.% of phosphorus element with a predominance of nickel element. In addition, the anticorrosion properties of the Ni-Cu-P coatings in 1 M HCl, 1 M H2SO4, and 3% NaCl solutions were investigated using Tafel polarization curves, electrochemical impedance spectroscopy, and SEM/EDX analysis. The result showed a marginal improvement in corrosion resistance in 3% NaCl solution compared to acidic medium. It also showed that the corrosion mechanism depends on the nature of the solution.

Nickel electrodeposition on copper substrate for cyclotron production of 64Cu

Natural nickel electrodeposition on a copper substrate with a gold layer was studied with the aim of production of 64Cu radionuclide. The electrodeposition experiments were carried out in acid plating baths. The operating parameters such as pH, temperature, and current density were optimized. The current efficiency was measured at different current densities. The optimum conditions of the nickel electrodeposition are as follows: 5.7 g 1−1 nickel, pH 3–4, dc current density 85.54 mA cm−2, and 55°C, with 97% current efficiency. SEM photomicrographs demonstrated fine-grained structure of the deposit obtained from the optimum bath. A 46-μm high-quality layer was deposited on a gold layer of the copper substrate.

Composite electroplating of Cu–SiO 2 nano particles on carbon fiber reinforced epoxy composites

The main purpose of this work is to co-deposit nano-SiO 2 particles into the copper coatings on carbon fiber reinforced epoxy (C/EP) composite surface by electrodeposition method in order to improve the micro hardness of coatings. C/EP composites are copper plated with sulfuric acid based solution, and the effects of nano-SiO 2 and C 6H 12O 6 in the electrolyte contents on the copper coatings are investigated. It is found that crystalline grains of coatings are markedly refined by nano-SiO 2 in the acidic sulfate copper plating bath and the ceramic particles cause an increase in hardness of coatings though nano-SiO 2 results in a decline of deposition rate and a decrease in electrical conductivity of electroplating layers. Otherwise, C 6H 12O 6 in the plating bath is indispensable to the layer formation even though nano-SiO 2 added. These results demonstrate that the hardness of coatings will be increased with appropriate contents of co-deposited SiO 2 and C 6H 12O 6 in the plating bath.

Electroless Sn–Ni alloy plating with high Sn content free of activation pretreatment

Electroless plating technique was used to coat Sn–Ni alloy on copper substrate with high Sn content by adding the amounts of thiourea as special complexing agent and sodium hypophosphite as reducing agent to an acidic electroless plating bath of SnCl 2 and NiCl 2, which avoided activation pretreatment in plating process. The Sn content of the Sn–Ni layer increased with lowing temperature which reached 60 wt.% under optimum plating conditions. The effect of thiourea and sodium hypophosphite amount, plating temperature, and the acidity of plating bath was also discussed in this article. The corrosion-resistance properties of Sn–Ni alloy layer proved to be good by testing the anodic polarization curves of the alloy layer.

Electrodeposited nanocrystalline bronze alloys as replacement for Ni

AbstractNanocrystalline white‐bronze, CuSn, electroplating was investigated as alternative to Ni plating as undercoat for noble metals in jewellery applications. A strongly acidic plating bath was developed with an organic additive to suppress hydrogen evolution and obtain bright coatings. Polarization curves indicate a strong inhibition by the organic additive at the tin equilibrium potential. Mass transfer controlled deposition yields nanocrystalline bronze coating with 0–65 wt% Sn. One or two low temperature equilibrium phases, high temperature equilibrium phases or a non‐equilibrium phase were identified by XRD analyses. Bright white bronze, 50 wt% Cu/50 wt% Sn, bronze coatings show improved tarnishing resistance and similar corrosion and wear resistance as undercoat for gold on actual jewellery parts compared to nickel. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A pretreatment with galvanostatic etching for copper electrodeposition on pure magnesium and magnesium alloys in an alkaline copper-sulfate bath

A pretreatment with galvanostatic etching is recommended to obtain an adherent and uniformly covered copper deposit on pure magnesium and magnesium alloy specimens (AZ31 and AZ61) in an alkaline copper-sulfate bath. The effect of galvanostatic etching on the surfaces of Mg and Mg alloy specimens can be realized by their potential variation during galvanostatic etching, in which four distinct stages could be distinguished. Galvanostatic etching to stage III, an activated surface of Mg or Mg alloy, was obtained for electroplating a uniformly covered Cu deposit in the alkaline Cu-sulfate bath. The Cu-deposited Mg or Mg alloy was used as the substrate for further Cu and then Ni electrodeposition in acid plating baths to obtain a protective Ni/Cu coating. The proposed electroplating baths are environmentally friendly, and the electrodeposition process is easy to conduct to achieve a protective coating for Mg and Mg alloys.

Copper electrodeposition from an acidic plating bath containing accelerating and inhibiting organic additives

Copper electrodeposition on copper from still plating solutions of different compositions was investigated utilising electrochemical impedance spectroscopy (EIS), cyclic voltammetry, and scanning electron microscopy (SEM). An acid copper sulphate plating base solution was employed either with or without sodium chloride in the presence of a single additive, either polyethylene glycol (PEG) or 3-mercapto-2-propanesulphonic acid (MPSA), and their mixture. Thallium underpotential deposition/anodic stripping was employed to determine the adsorption capability of additives on copper. In the absence of chloride ions, MPSA shows a moderate adsorption on copper, whereas PEG is slightly adsorbed. At low cathodic overpotentials, the simultaneous presence of MPSA and chloride ions accelerates copper electrodeposition through the formation of an MPSA-chloride ion complex in the solution, particularly for about 220 μM sodium chloride. The reverse effect occurs in PEG-sodium chloride plating solutions. In this case, from EIS data the formation of a film that interferes with copper electrodeposition can be inferred. At higher cathodic overpotentials, when copper electrodeposition is under mass transport control, the cathode coverage by a PEG-copper chloride-mediated film becomes either partially or completely detached as the concentration of chloride ions at the negatively charged copper surface diminishes. The copper cathode grain topography at the μm scale depends on the cathodic overpotential, plating solution composition and average current density. Available data about the solution constituents and their adsorption on copper make it possible to propose a likely complex mechanism to understand copper electrodeposition from these media, including the accelerating effect of MPSA and the dynamics of PEG-copper chloride complex adsorbate interfering with the surface mobility of depositing copper ad-ions/ad-atoms.

Growth Behavior of Ni–P Film on Fe/Si Substrate in an Acid Electroless Plating Bath

Ni–P film was electrolessly deposited on Fe/Si substrate in an acid plating bath containing nickel sulfate as the nickel source and sodium hypophosphite as a reducing agent. The Fe film in Fe/Si substrate was formed by electron-beam evaporation deposition. The Ni–P film was characterized by transmission electron microscopy. The results showed that the Ni–P film on Fe/Si substrate has a homogeneous and nanocrystalline structure in comparison with that on Si substrate, which has a columnar structure, and there are straight cracks in the Ni–P film when the pH value of the plating bath is relatively high due to the higher internal tensile stress. The plating rates of Ni–P film on Fe/Si substrate increase with increase in plating temperature and pH value, ranging from 0.22 to 5.27 nm/s for plating temperatures of and pH values of 4.2–5.0. The activation energies of Ni–P films on Fe/Si substrate were 99.58, 87.4, and 41.55 kJ/mol for pH values of 4.2, 4.6, and 5.0, respectively.

The oxide electrochemistry of ruthenium and its relevance to trench liner applications in damascene copper plating

There is considerable interest in the use of ruthenium as an ultrathin trench liner in damascene copper plating used to fabricate on-chip interconnects. The problem is that when freshly deposited ruthenium films are exposed to air, their surfaces tend to undergo spontaneous oxidation, and such deposits (as demonstrated here) are reluctant to undergo reduction. Copper deposition in an acid plating bath occurs readily on the oxidized ruthenium, but the presence of oxide is known to have a detrimental effect both on the copper superfilling process and copper adhesion at the Ru/Cu interface.

Electrodeposition of platinum metal on titanium and anodised titanium from P salt: application to electro-oxidation of glycerol

Pt/Ti and Pt/TiO2 electrodes were made by galvanic deposition of platinum metal from an acid plating bath containing cis-dinitro-diammin-platinum(II) complex (P salt) onto titanium and anodic TiO2 layer on titanium substrates respectively. Titanium oxide nanotubes were fabricated by anodising titanium foil in acid solution. Pt/Ti and Pt/TiO2 electrodes were characterised using electrochemical methods and scanning electron microscopy. Cyclic voltammetric analysis of Pt/Ti electrodes in dilute sulphuric acid yields voltammograms with features characteristic of bulk polycrystalline platinum electrodes. In contrast, the voltammograms for Pt/TiO2 electrodes are not quantitatively similar to those for smooth polycrystalline platinum electrodes. Voltammetry in potassium ferricyanide yields reversible voltammograms, indicating the good electrical conductivity of and connectivity between the deposited platinum and substrates and hence the absence of any significant resistive surface oxide film. The electrocatalytic behaviour of this type of electrodes in the glycerol electro-oxidation was studied.

Nucleation of Tin and Tin–Silver Alloy on Copper and Nickel in Acid Plating Baths

The rate of nucleation and number density of nuclei of tin and tin–silver deposits on copper and nickel substrates in acid sulfate and acid methanesulfonate baths were measured by application of a nucleation model to chronoamperometric data. Based on the dependence of nucleation rate on overpotential, the critical Gibbs free energy of nucleation and the critical nucleation size were calculated. A mechanism of alloy nucleation in the presence of thiourea is proposed.

MORPHOLOGY, THERMAL STABILITY, AND SOLDERABILITY OF ELECTROLESS NICKEL–PHOSPHORUS PLATING LAYER

We studied the growth kinetics and characteristics of electroless nickel–phosphorus (EN–P) deposition layer on Cu substrate in an acid plating bath with sodium hypophosphite as the reducing agent. The individual nodules of the EN–P layer increased in size but decreased in number with increasing plating time and pH, i.e. the root-mean-square (RMS) roughness of the EN deposit decreased. In addition, the plating rate of the EN layer increased with increasing plating bath pH. X-ray diffraction (XRD) analyses revealed that the as-plated deposit was in an amorphous phase, while the heat-treated layer was composed of crystallized Ni and Ni 3 P compound. The solderability of the EN layer increased with decreasing P content. In addition, the wetting force increased with increasing surface roughness. The present study clearly showed that the solderability behavior of the EN layer is affected by both surface composition ( P content) and morphology.

Effect of rare earth (Ce, La) compounds in the electroless bath on the plating rate, bath stability and microstructure of the nickel–phosphorus deposits

Effects of added rare earth elements (RE) in the acidic hypophosphite plating bath on the plating rate, bath stability and microstructure of the electroless nickel–phosphorus (EN) deposits were studied. The surface appearance and microstructure were examined under a reflection optical microscope and a scanning electron microscope equipped with an in-situ energy dispersive X-ray spectroscopy, which can evaluate the elemental analysis of deposits. It was demonstrated that the rare earth elements can decrease grain size and refine microstructure. The deposition rate of the Ni–P deposits was estimated by gravimetric, polarization and quartz crystal microbalance (QCM) methods. Results revealed that up to an optimum concentration of rare earth elements, the deposition rate increases. The stability test method was used to determine the stabilization effect of RE on the stability of the bath. It was found that the addition of RE significantly improved the Pd stability of the EN bath.

Deposition of electroless Ni on micro-sized acrylic spheres

In this work a thin film of electroless Ni was deposited on the surface of commercial acrylic spheres about 4 μm in size. After the acrylic spheres were cleaned, sensitized and activated successively, they were put into an acid plating bath containing sodium hypophosphite as reducing agent for the electroless Ni deposition. The acrylic spheres with a film of Ni deposit were molded into a cold set resin and ground and polished to form a cross section for observation. The thickness of the Ni film was measured and the state of the adhesion of Ni film to the surface of the acrylic sphere was observed by a scanning electron microscope. The results showed that the Ni film deposited in a plating bath with pH 4.2 can tightly adhere on the surface of the acrylic sphere due to the compressive stress of the Ni film. The thickness of the Ni film on the acrylic sphere can reach about 0.35 μm in 3 min of deposition time at 50–70 °C of plating temperature. The activation energy of electroless Ni deposition in plating bath with pH 4.2 is about 28.50 kJ/mole. The acrylic spheres with a layer of electroless Ni film deposited by the method proposed in this work can be further applied to anisotropic conductive adhesives in flip chip package.

Role of Cu2+ as an Additive in an Electroless Nickel−Phosphorus Plating System: A Stabilizer or a Codeposit?

The effect of cupric (Cu2+) ion as an additive in the acidic electroless nickel plating (ENP) bath on the characteristics of the resulting nickel−phosphorus (Ni−P) alloys was investigated mainly with X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray (EDX) spectrometry. Cupric ions in the acidic ENP bath using hypophosphite anions as reductants have been reported ambiguously as stabilizers or codeposit constituents. In this work, the critical concentration of added copper salts, CuSO4·5H2O, that starts to inhibit the ENP process was determined to be ca. 536 mg/L. In general, the deposition rate, surface morphology, and pit formation on the surface of as-deposits are significantly improved with Cu2+ addition at concentrations less than the critical value. The electroless nickel alloys were shown as a mixture of an amorphous deposit and a crystalline copper metal rather than as amorphous alloys alone.1,2 During the initial stage of the electroless plating process, the copper conten...

Detection of Organic Electroactive Species in Acidic Copper Plating Baths by HPLC with an Electrochemical Detector

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Temperature and pH dependence of the electroless Ni–P deposition on silicon

The sensitization, activation, nucleation and growth of electroless Ni–P deposition on silicon in an acid plating bath with sodium hydrophosphite as reducing agent and sodium succinate as complexing agent were studied by transmission electron microscopy, field emission scanning electron microscopy and atomic force microscopy. The results show that a continuous polycrystalline SnCl 2 film was formed on the silicon surface in the sensitization process, and small crystalline Pd particles were dispersedly produced on SnCl 2 film in the activation process. In the initial deposition stage, the small Ni–P particles had already emerged on the silicon surface in a deposition time of less than 2 s. When Ni–P particles grew, their size increased but their number decreased, and they later developed into a columnar structure. The deposition rate of the electroless Ni–P deposit increased as the pH value and the temperature of the plating bath increased (from 1.36 to 29.66 μm/h). The activation energy of the electroless Ni–P deposition on silicon increased as the pH value of the plating bath decreased (from 68.8 to 79.4 kJ/mol).

SPE-HPLC Detection of Organic Additives in Acidic Copper Plating Baths : I. Sulfopropyl Disulfide-Based Brighteners

A technique has been developed for the study of reaction mechanism and the monitoring of copper electroplating baths utilizing a combination of solid phase extraction (SPE) and high-performance liquid chromatography (HPLC). This method appears suitable for live plating bath control as well as for organic identification, concentration measurement, and reaction mechanism studies. While in the past the total amount of carbon (TOC) present in the deposition bath was used to quantify the decomposition of organics and to determine the plating bath quality, a strong correlation between the TOC measurement and effective plating bath composition was not possible. Moreover, a direct way to thoroughly analyze the organic components of the bath is not commonly available using current electrochemical techniques. However, the results from experiments conducted with the technique described in this paper show how the monitoring of a few diagnostic peaks recovered from a live bath sample can be used directly for this purpose. The identification and quantification of by-products is also proven. Two copper sulfuric plating baths at different acidity were used for this study, and the stability of bis(sodiumsulfopropyl) disulfide and polyethylene glycol additive components, as well as their degradation mechanism and by-products, are studied in this work.

Ion-pair chromatography of bis (sodium-sulfopropyl) disulfide brightener in acidic copper plating baths

Quantitative analysis of the brightener component bis (sodium-sulfopropyl) disulfide (SPS) in acidic copper plating baths poses a real challenge due to the complex chemical matrix containing large amounts of Cu(II) ion and sulfuric acid together with other organic additives and additive decomposition products. We developed a new ion-pair chromatography method to analyze micro-molar amounts of SPS directly in plating bath samples without the need for sample pre-treatment. Addition of tetra- N-methylammonium cation as ion-pairing agent to a methanol–sulfuric acid–water eluent increases the retention time of the anionic SPS 2− on a C 18 column sufficiently to separate this compound from Cu(II) ion and additive by-products.

Design of Acidic Ni-Mo Alloy Plating Baths Using a Set of Apparent Equilibrium Constants

The electrodeposition of Ni-Mo alloy using a series of aqueous acidic citrate plating baths (pH 5.0) were examined from the standpoint of the Ni(II)- and Mo(VI)-species present in the solutions. The distribution of the species was calculated using a set of the formation constants for polymolybdates and citrate complexes, optimized by a factor analysis of optical spectra. Through the design of the bath compositions such that the dominant Ni(II)- and Mo(VI)-species are both 1:1 complexes with citrate, lustrous and uniform Ni-Mo layers having almost constant Ni content were found to be plated over a wide range of Ni(II)/Mo(VI) analytical concentration ratios, although the current efficiency decreased with decreasing Ni(II) concentration. This indicates the validity and importance of the bath design using these constants. The deposition phenomena were briefly discussed in terms of the mechanisms hitherto reported. © 2004 The Electrochemical Society. All rights reserved.