Showing papers on "Electroplating published in 2015"

Exploiting Microscale Roughness on Hierarchical Superhydrophobic Copper Surfaces for Enhanced Dropwise Condensation

Abstract: These studies are limited to silicon substrates, however, and are not suitable for scaled-up industrial applications. Therefore, it is highly desirable to develop hybrid surfaces that are compatible with materials commonly employed for heat transfer applications, such as copper. To the best of our knowledge, studies of dropwise condensation on copper substrates have exclusively focused on nanostructured surfaces; [ 25–27 ] condensation dynamics on copper surfaces with hierarchical surface structures have not been explored. In this work, we develop a technique to fabricate hierarchical micro/nanostructured surfaces on copper substrates, and exploit the role of microscale roughness elements to increase the droplet departure frequency during the condensation process. To demonstrate the effectiveness of such surfaces, the droplet growth rate at the start of condensation and the cumulative droplet self-removal volume for the hierarchical surface are compared to a surface which features only nanostructures. The hierarchical copper surfaces were fabricated in the Birck Nanotechnology Center at Purdue University. The process fl ow diagram is shown in Figure S1 (Supporting Information). The copper substrate (0.5 mm thick) was fi rst cleaned in a diluted HCl solution (volume ratio HCl: deionized (DI) water = 1:3) for 2 min, rinsed with DI water, and dried with nitrogen. A photoresist layer was then lithographically patterned onto the copper substrate. This process included spin-coating with hexamethyldisilazane (HMDS) at 3000 rpm for 20 s and photoresist AZ 9260 at 1000 rpm for 30 s. Subsequently, the copper was soft-baked at 100 °C for 15 min and exposed for 78 s at a power of 26 mW cm −2 under a chrome mask in a mask aligner (MJB-3, Karl Suss). The mask has square arrays of dots (30 μm diameter) at six different pitches (40, 50, 60, 70, 90, and 105 μm). The exposed photoresist layer was developed using AZ 400K in DI water at a dilution ratio of 1:1.5 for 3 min. A photoresist layer with a thickness of ≈15 μm was produced as a mold for subsequent copper deposition on exposed areas via electroplating. Pulse-electroplating was performed in a custom setup. The electrolyte had three main components: CuSO 4 ·5H 2 O (225 g L −1 ), H 2 SO 4 (40 g L −1 ), and HCl (50 mg L −1 ). The processing parameters (current density, frequency, and duty cycle) were tuned to achieve dense and uniform copper grains within the exposed areas. Electroplating was performed with a current density of 10 mA cm −2 at 1 Hz and 50% duty cycle. The total electroplating time to fi ll the mold was ≈2 h. After electroplating, the copper substrate was soaked in acetone for 2 min to dissolve the AZ 9260 photoresist mold and form copper microposts on the substrate (Figure S2, Supporting Information). Condensation of water vapor is of great interest in thermal management [ 1 ] and power generation [ 2 ] owing to the improved heat transfer by phase change, and in desalination [ 3 ] and dew/ fog harvesting [ 4,5 ] systems for its ability to extract vapor from carrier gases. Enhancement of the condensation heat and mass transfer processes in these systems could lead to considerable performance gains, economic return, and energy savings. Heterogeneous condensation is dramatically infl uenced by the physical structure and chemical properties of a surface. Depending on the surface wettability, water vapor can condense on a surface either as a continuous liquid fi lm (fi lmwise) or as individual droplets (dropwise). It is reported that dropwise condensation can produce heat transfer coeffi cients that are an order of magnitude higher than in fi lmwise condensation. [ 6 ] To attain this performance, condensed droplets must be rapidly removed from the surface and fresh spaces on the substrate exposed for nucleation; otherwise, accumulated large droplets will act as a thermal barrier and inhibit the heat/mass transfer rate. [ 7 ] To promote removal of condensate droplets, the droplet adhesion to the substrate must be minimized. Structured superhydrophobic surfaces [ 8–12 ] could offer an ideal means for enhanced dropwise condensation via improved droplet shedding due to their ability to support spherical water droplets with large contact angle and minimal contact angle hysteresis. However, unlike sessile droplets deposited artifi cially on such surfaces, droplets formed by condensation grow on all interstitial surfaces of the substrate, from the bottom up. Thus, notionally superhydrophobic surfaces (characterized via sessile droplet deposition) do not necessarily preserve their superhydrophobicity during condensation. [ 13–15 ] Previous studies [ 14,15 ] have shown that on superhydrophobic surfaces with only microscale roughness, condensate droplets tend to nucleate and grow in the cavities between microstructures, forming sticky droplets in the Wenzel state, [ 16 ] which are pinned strongly to the surface at the three-phase contact line. To overcome this limitation, superhydrophobic surfaces with nanoscale [ 17,18 ] or hybrid micro/ nanoscale [ 19–24 ] roughness have been developed that enable the formation of condensate droplets in the Cassie state. Although nanostructured surfaces can retain their superhydrophobicity and prevent contact-line pinning of droplets

Electrodeposition of laminar coatings of Ni–W alloy and their corrosion behaviour

Abstract: The attractiveness of electroplating for the synthesis of advanced materials is linked to large selection of plating conditions coupled with different mass transfer processes towards the cathode, and this allows the tailoring of different properties of many electrodeposited coatings. This theme has been exploited effectively in the development of a new class of coatings; called composition modulated multilayered (CMM), or in short laminar coatings. The work embodied in this paper is to demonstrate how the corrosion resistance of monolayer Ni–W alloys can be increased to many fold of its magnitude by multilayer deposition. Ni–W coatings have been deposited on mild steel (MS) in a laminar multilayer pattern from a citrate bath using single bath technique (SBT). Electrodeposits having alternate layers of alloys, having different compositions were developed by modulating the direct current (DC). CMM coating configurations have been optimized from a newly developed bath, in terms of current pulse height and thickness of each layer to maximize its corrosion protection ability, in relation to its monolayer coating, developed from same bath for same time. The process and product of the Ni–W coatings have been characterized using different instrumental methods, such as cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) study. The better corrosion resistance behaviour of CMM Ni–W coatings has been analysed in the light of increased surface areas of the coatings due to layering, and results are discussed.

Properties of nanocrystalline Cr coatings prepared by cathode plasma electrolytic deposition from trivalent chromium electrolyte

Abstract: Pure Cr coatings were prepared directly from trivalent chromium sulfate electrolyte by cathode plasma electrolytic deposition (CPED). Composition and microstructure of the coatings were investigated by EDS, XRD, SEM and TEM. The deposited Cr coatings are crack-free with the thickness up to approximately 30 μm, and exhibit nanocrystalline structure, high hardness, excellent adhesion and corrosion resistance with the stainless steels. The quality of Cr coatings prepared by CPED is improved significantly compared with that prepared by traditional chromium electroplating. It indicates that cathode plasma electrolytic deposition is an effective way to prepare high quality Cr coatings.

Synthesis, structure, and properties of superhydrophobic nickel–PTFE nanocomposite coatings made by electrodeposition

Abstract: The objective of the current research is to create multifunctional metal matrix composite coatings that are able to provide high strength as well as high water repellency by electrodeposition of nanocrystalline nickel matrix with embedded polytetrafluoroethylene (PTFE) particles. The study of the co-deposition process demonstrated that the amount of PTFE co-deposited is highly dependent on the concentration of PTFE particles in the electroplating bath. A very high fraction of co-deposited PTFE was achieved (69 vol.%) using a concentration of 30 g/L of PTFE particles in the plating bath. The contact angle of the surface greatly increased when the PTFE content increased over 50 vol.%. At 69 vol.% PTFE the coatings had a contact angle of 152°. Saccharin was added to the electroplating bath in an attempt to refine grain size. Using transmission electron microscopy, the average grain size of the nickel matrix without saccharin was determined to be 27 nm for the coating containing 69 vol.% PTFE. However, no nickel grain size reduction was observed when saccharin was added as it was found that the composite samples already had a very fine grain structure likely due to the use of cetyltrimethylammonium bromide (CTAB) as a PTFE particle dispersant. The addition of saccharin provided no additional hardening of the composite while the wetting angle was greatly decreased at concentrations greater than 0.1 g/L.

Ultra-precision grinding of optical glasses using mono-layer nickel electroplated coarse-grained diamond wheels. Part 1: ELID assisted precision conditioning of grinding wheels

Abstract: In order to realize ultra-precision grinding of optical glasses with mono-layer nickel electroplated coarse-grained diamond grinding wheels, a novel conditioning technique was developed using copper bonded diamond grinding wheels with grain sizes of 15 μm (D15) and 91 μm (D91), respectively, as conditioners for truing of diamond wheels with grain sizes of 46 μm (D46), 91 μm (D91) and 151 μm (D151), respectively. During the conditioning process, the conditioners were continuously dressed by means of electrolytic in-process dressing (ELID). A force transducer was used to monitor the conditioning force while a coaxial optical distance measurement system was used to monitor the wheel run-out. In addition, a white-light interferometer (WLI) and a scanning electron microscope (SEM) were used to characterize the successively modified diamond grain morphologies of the conditioned wheels both directly and by a replication technique. The experimental results show that with optimized conditioning parameters, the developed conditioning technique can be applied for truing of coarse-grained diamond wheels within the abrasive layer achieving a constant wheel peripheral envelop surface exhibiting flattened diamond grains with a run-out

A combined theoretical and experimental study for silver electroplating.

Abstract: A novel method combined theoretical and experimental study for environmental friendly silver electroplating was introduced. Quantum chemical calculations and molecular dynamic (MD) simulations were employed for predicting the behaviour and function of the complexing agents. Electronic properties, orbital information, and single point energies of the 5,5-dimethylhydantoin (DMH), nicotinic acid (NA), as well as their silver(I)-complexes were provided by quantum chemical calculations based on density functional theory (DFT). Adsorption behaviors of the agents on copper and silver surfaces were investigated using MD simulations. Basing on the data of quantum chemical calculations and MD simulations, we believed that DMH and NA could be the promising complexing agents for silver electroplating. The experimental results, including of electrochemical measurement and silver electroplating, further confirmed the above prediction. This efficient and versatile method thus opens a new window to study or design complexing agents for generalized metal electroplating and will vigorously promote the level of this research region.

Fabrication and electrical performance of through silicon via interconnects filled with a copper/carbon nanotube composite

Abstract: In this work, through silicon vias (TSVs) were fabricated using a materials system consisting of a composite of copper (Cu) and vertically grown carbon nanotubes (CNTs) as a possible solution to the problems encountered when using Cu-based interconnects. A metallic seed layer, tungsten, was deposited prior to CNT growth. Tungsten replaces Cu as a seed layer due to the thermal sensitivity of Cu at CNT growth temperatures. CNTs were grown both on the wafer surface and inside the silicon vias by chemical vapor deposition. A self-directed densification process was applied to modify the shape of the CNTs from a forest with equal top and bottom dimensions into bundles with a significantly smaller dimension at the top compared to the bottom. This process maximizes the contact area between the Cu electroplating solution and the CNTs. Cu was deposited by periodic pulse electroplating after CNT growth to form the Cu/CNT composite. Wafer thinning and polishing completed the TSV fabrication forming a test configuration to evaluate electrical performance. Experimental results were compared for interconnects filled with pure Cu to those filled with the Cu/CNT composite. The results indicate potential application of the Cu/CNT composite as a TSV interconnect material.

Effect of current density on morphology of electroplated tin

Abstract: In this work, tin electroplating from acidic sulphate bath containing stannous sulphate, sulphuric acid and a glycol type additive with a leveller has been studied on steel substrates. The effects of plating current density on microstructural and morphological features are investigated. The structural and morphological characteristics have been studied by X-ray diffraction (XRD), and scanning electron microscopy (SEM). The XRD analysis confirms that the coatings produced by sulphate bath consist of tetragonal (β-Sn) crystal structure. The grain size of the deposits decreases up to a critical current density (∼30 mA cm−2), and then an increase in grain size is noticed. The coating morphology turns irregular and porous at higher current densities (about 40–50 mA cm−2) due to the rapid increase in hydrogen evolution as depicted from the secondary electron SEM images. Line profile analysis across the cross-section of the coatings further confirms the absence of any constituent coming from the bath add...

Direct identification and analysis of heavy metals in solution (Hg, Cu, Pb, Zn, Ni) by use of in situ electrochemical X-ray fluorescence.

Abstract: The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limit...

A pulsed mode electrolytic drug delivery device

Abstract: This paper reports the design of a proof-of-concept drug delivery device that is actuated using the bubbles formed during electrolysis. The device uses a platinum (Pt) coated nickel (Ni) metal foam and a solid drug in reservoir (SDR) approach to improve the device's performance. This electrochemically-driven pump has many features that are unlike conventional drug delivery devices: it is capable of pumping periodically and being refilled automatically; it features drug release control; and it enables targeted delivery. Pt-coated metal foam is used as a catalytic reforming element, which reduces the period of each delivery cycle. Two methods were used for fabricating the Pt-coated metal: sputtering and electroplating. Of these two methods, the sputtered Pt-coated metal foam has a higher pumping rate; it also has a comparable recombination rate when compared to the electroplated Pt-coated metal foam. The only drawback of this catalytic reformer is that it consumes nickel scaffold. Considering long-term applications, the electroplated Pt metal foam was selected for drug delivery, where a controlled drug release rate of 2.2 μg ± 0.3 μg per actuation pulse was achieved using 4 mW of power.

Microstructuring of carbon nanotubes-nickel nanocomposite

Abstract: In this paper, we develop a novel electroplating method for the synthesis of carbon nanotubes (CNTs)-nickel (Ni) nanocomposite, and present the fabrication of a silicon micromirror with the CNTs-Ni nanocomposite beams to evaluate the mechanical stability of the micromirror in terms of resonant frequency. CNTs are pretreated to have positive charges on their surface and added into a Ni electroplating solution to form a CNTs-Ni nanocomposite electroplating suspension. The weight fraction of the CNTs in the electroplated nanocomposite is 2.4 wt%, and the ultramicroindentation hardness is 18.6 GPa. The mechanical strengthening phenomenon is found in the nanocomposite in comparison with a Ni film. Moreover, the addition of CNTs in the nanocomposite beams effectively increases the shear modulus compared with the pure Ni. The maximum variation of the resonant frequency of the micromirror during a long-term stability test is approximately 0.25%, and its scanning angle is approximately 20°. It shows the potential suitability of the CNTs-Ni nanocomposite with proper design for micromechanical element applications.

Oxidation and Electrical Behavior of a Ferritic Stainless Steel with a Mn–Co-Based Coating for SOFC Interconnect Applications

Abstract: Protective coatings with high electrical conductivity that resist oxide scale growth are required for stainless steel interconnect materials in the long-term durable operation of solid oxide fuel cells. This work evaluates the oxidation and electrical behavior of Crofer 22 APU ferritic stainless steel coated with manganese and cobalt by electrodeposition. Isothermal and cyclic oxidation (800 °C in air) tests were done to evaluate the role of the coating layer during oxidation. Area-specific resistance (ASR) of the coated and uncoated substrates was also tested at 800 °C in air. Results show that the coating layer transforms into Mn1.5Co1.5O4 spinel during oxidation. The mass gain and spallation indicated that the formation of Mn–Co spinel improves the high temperature oxidation. These spinels also cause a reduction in ASR for electroplated substrates (12.42 mΩ cm2) as compared to uncoated ones (38.74 mΩ cm2) after 400 h of isothermal oxidation at 800 °C.

Effect of Current Density and Plating Time on Cu Electroplating in TSV and Low Alpha Solder Bumping

Abstract: In this study, copper filling in through-silicon via (TSV) by pulse periodic reverse electroplating and low alpha solder bumping on Cu-filled TSVs was investigated. The via diameter and depth of TSV were 60 and 120 µm, respectively. The experimental results indicated that the thickness of electrodeposited copper layer increased with increasing cathodic current density and plating time. The electroplated Cu in TSV showed a typical bottom-up filling. A defectless, complete, and fast 100% Cu-filled TSV was achieved at cathodic and anodic current densities of −8 and 16 mA/cm2 for a plating time of 4 h, respectively. A sound low alpha solder ball, Sn-1.0 wt.% Ag-0.5 wt.% Cu (SAC 105) with a diameter of 83 µm and height of 66 µm was reflow processed at 245 °C on Cu-filled TSV. The Cu/solder joint interface was subjected to high temperature aging at 85 °C for 150 h, which showed an excellent bonding characteristic with minimum Cu-Sn intermetallic compounds growth.

The electrodeposition of nanocrystalline Cobalt–Nickel–Phosphorus alloy coatings: a review

Abstract: The importance of Co–Ni–P alloy deposits is summarised and recent developments are highlighted. Electroplating and electroless deposition of nanocrystalline Co–Ni–P ternary coatings are considered. Nanostructure, physical and mechanical properties (including corrosion resistance) of various bath types and compositions (including pH and electrolyte additives) as well as plating conditions (including current density, temperature and agitation) are summarised. Applications range from wear and corrosion resistant coatings, particularly as a hard chromium replacement to speciality hydrogen evolution electrodes in water electrolysis. Following this concise review, future research needs are briefly listed.

Fe-Pt thick-film magnets prepared by electroplating method

Abstract: Fe-Pt thick-films were electroplated on Ta substrates using a direct current, and the magnetic properties of the film were evaluated. The Fe-Pt films with the thickness from 3 to 23 μm were obtained by changing in the plating time from 2 to 20 min. As the as-plated Fe-Pt films had the disordered fcc (face-centered-cubic) structure and low coercivity (<5 kA/m), we annealed the films at 700 °C for 60 min. The annealing induced the phase transformation from fcc structure to fct (face-centered-tetragonal) one, and we consequently obtained the Fe50Pt50 thick-films with large coercivity of approximately 700 kA/m. The large coercivity was observed in the wide thickness range for our experimental conditions. Therefore, we concluded that our prepared Fe-Pt film is one of the attractive thick-film magnets.

Electrochemistry of Metal Complexes: Applications from Electroplating to Oxide Layer Formation

Abstract: Starting with general considerations on equilibria in solutions and at interfaces as well as on mass transport, the text acquaints readers with the theory and common experimental practice for studying electrochemical reactions of metals complexes. The core part of the book deals with all important aspects of electroplating, including a systematic discussion of co-deposition of metals and formation of alloys. It also discusses such related subjects as oxide layer formation and hydrogen evolution as a side reaction.

Characterization of Imidazolium Chloride Ionic Liquids Plus Trivalent Chromium Chloride for Chromium Electroplating

Abstract: A series of mixtures consisting of the ionic liquids (ILs) 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-hexyl-3-methylimidazolium chloride ([emim][Cl], [bmim][Cl], and [hmim][Cl], respectively) and trivalent chromium chloride have been prepared. Physicochemical and electrochemical properties of these mixtures have been studied and the potential applications of these mixtures for chromium electroplating, as an alternative to the conventional hard chromium electroplating processes using hexavalent chromium baths, have been examined. To optimize the transport properties of the mixtures, different amounts of ultrapure water were added to the Cr(III) salt–IL mixtures, although the ultimate goal is to reduce or eliminate water. As shown previously for choline chloride/Cr(III) salt mixtures, we found that the physicochemical and electrochemical properties of the mixtures are affected by the relative water content. Our preliminary electroplating results show that these types o...

Investigation of the Microstructure and the Mechanical Properties of Cu-Ni C Composite Produced by Accumulative Roll Bonding and Coating Processes

Abstract: In the present study, Cu-1.8 wt.% NiC (nickel coating) composite was produced by the combination of two methods, including accumulative roll bonding (ARB) and electroplating processes. Electroplating process was done on copper strips in order to produce a nickel-particle-reinforced composite. Microstructure, texture, and the mechanical properties of the produced composite were evaluated during various cycles of ARB using optical and scanning electron microscopes, x-ray diffraction, microhardness, and tensile tests. In addition, the results were compared with Cu-Cu and also Cu-NiS (nickel sheet) samples. It was found that nickel layers were fractured from the first cycle of the process, and nickel fragments were distributed in the copper matrix as the number of cycles was increased. Variation of orientation density of α-, β-, and τ-fibers for the produced composite was examined in different cycles. Microhardness for different elements in different cycles of Cu-NiC was also evaluated. Also, the investigation of the mechanical properties showed that by proceeding the ARB process, the tensile strength of the produced Cu-NiC and Cu-Cu samples was increased. However, improvement in the mechanical properties of composite samples was more noticeable due to the reinforcing effect of nickel particles. The elongation of composite samples showed a decrease in the primary cycles, unlike Cu-Cu ones; however, it was then increased. Finally, by using scanning electron microscopy, the fracture surfaces of Cu-NiC composite were studied to disclose the fracture mechanism of the samples.

An investigation of supercritical-CO2 copper electroplating parameters for application in TSV chips

Abstract: This study uses supercritical electroplating for the filling of through silicon vias (TSVs) in chips. The present study utilizes the inductively coupled plasma reactive ion etching (ICP RIE) process technique to etch the TSVs and discusses different supercritical-CO2 electroplating parameters, such as the supercritical pressure, the electroplating current density’s effect on the TSV Cu pillar filling time, the I–V curve, the electrical resistance and the hermeticity. In addition, the results for all the tests mentioned above have been compared to results from traditional electroplating techniques. For the testing, we will first discuss the hermeticity of the TSV Cu pillars, using a helium leaking test apparatus to assess the vacuum sealing of the fabricated TSV Cu pillars. In addition, this study also conducts tests for the electrical properties, which include the measurement of the electrical resistance of the TSV at both ends in the horizontal direction, followed by the passing of a high current (10 A, due to probe limitations) to check if the TSV can withstand it without burnout. Finally, the TSV is cut in half in cross-section to observe the filling of Cu pillars by the supercritical electroplating and check for voids. The important characteristic of this study is the use of the supercritical electroplating process without the addition of any surfactants to aid the filling of the TSVs, but by taking advantage of the high permeability and low surface tension of supercritical fluids to achieve our goal. The results of this investigation point to a supercritical pressure of 2000 psi and a current density of 3 A dm−2 giving off the best electroplating filling and hermeticity, while also being able to withstand a high current of 10 A, with a relatively short electroplating time of 3 h (when compared to our own traditional dc electroplating).

Fabrication of electrodes and near-field communication tags based on screen printing of silver seed patterns and copper electroless plating

Abstract: Highly conductive patterns were studied based on a combination of screen printing and electroless plating using Ag and Cu, respectively. Furthermore, near-field communication (NFC) tags were fabricated to demonstrate the performance of the conductive patterns. Ag and Cu patterns with thicknesses of 2-6 µm and 6 µm, respectively, were obtained. The conductivity of the pattern after the electroplating process was improved to approximately 20-30 times higher than that of the Ag-printed seed pattern, and its performance was 30% of that of a traditional chemical-etched pattern based on the photolithography process. Moreover, the Cu electroless plated pattern reached a level of 50% of the bulk Ag material. In addition, the resonance frequency of the fabricated NFC tag was measured using various numbers of coil turns, and was observed to range from 16 to 25 MHz. All the experimental processes were performed on a mass production platform and approached the commercialization level.