Copper Electrodeposition Research Articles

Novel 2,5-bis(6-(trimethylamonium)hexyl)-3,6-diaryl-1,4-diketopyrrolo[3,4-c]pyrrole pigments as levelers for efficient electroplating applications

2,5-Bis(6-(trimethylamonium)hexyl)-3,6-diaryl-1,4-diketopyrrolo [3,4-c]pyrrole (DPP) pigments are excellent choices as levelers for copper electrodeposition. Herein, novel 4-methoxylaryl (1b) and 4-trifluoromethoxyaryl (1d) diketopyrrolopyrrole-based levelers were synthesized and the inhibitory ability of these levelers is evaluated by electrochemical measurements on copper electrodeposition which were compared with 4-methylaryl (1a) and 4-trifluoromethylaryl (1c) diketopyrrolopyrrole-based levelers. To investigate interactions between metal surface and additives, quantum chemical calculations and molecular dynamics simulations were used. Among them, the 4-trifluoromethoxy-DPP (1d) showed optimal inhibition and strong adsorption capacity on the copper surface. Then, as the representative leveler, 1d was selected for the systematic study of the leveling influence during microvia filling. Notably, 1d has achieved the bottom-up deposition of microvias under the synergistic effect of the microvia filling performance reached 96.9%. These results demonstrated that 1d could serve as a promising leveler for microvia filling and provide theoretical guidance to the discovery and synthesis of novel levelers.

Selective electrochemical extraction of copper from multi-metal e-waste leaching solution and its enhanced recovery mechanism

Recycling activity for waste electrical and electronic equipment is always accompanied with leaching solution containing copper. Its selective extraction is of environmental and economic significance, and is beneficial for subsequent resource purification procedure. Compared with techniques such as chemical precipitation and solvent extraction, potentiostatic electrodeposition is outstanding with the advantage of high selectivity, electron as clean reagent, and minimal chemical usage. However, key factors affecting copper electrodeposition behavior as well as its kinetic process remain unclear, which blocks its further application. In this study, selective copper electrochemical extraction from multi-metal leaching solution of waste liquid crystal display panels is explored. Copper electrodeposition is analyzed from electrochemical and mass transport point of view, and the main results are summarized: (i) copper can be first electrodeposited due to its higher reduction potential compared with indium; (ii) applied potential and agitation are the most influential factors towards space-time yield and current efficiency; (iii) a semi-empirical kinetic model could quantitatively describe the influence of agitation and the time-current-concentration relationship. The model-predicted extraction rate agreed well with experimental data throughout electrodeposition; (iv) electrodeposition experiments show over 95% of copper can be selectively extracted as ultrafine copper powder (~150 nm) at 0.05 V (vs. SHE).

High TEC Copper to Connect Copper Bond Pads for Low Temperature Wafer Bonding

Copper to copper wafer hybrid bonding is the most promising technology for three-dimensional (3D) integration. In the hybrid bonding process, two silicon wafers are aligned and contacted. At room temperature (RT), these aligned copper pads contain radial-shaped nanometer-sized hollows due to the dishing effect induced by chemical-mechanical polishing (CMP). These wafers are annealed for copper to expand and connect upper and lower pads. This copper expansion is key to eliminate the radial-shaped hollows and make copper pads contacted. Therefore, in this research, we investigated the new high thermal expansion coefficient (TEC) electrodeposited copper to eliminate the dishing hollows at lower temperature than that with conventional copper using the combination of new additive A and low TEC additives. The TEC of new electrodeposited copper is 25.2 × 10−6 °C−1, 46% higher than conventional copper and the calculated contact area of copper surface at 250 °C with 5 nm dishing depth is 100%.

Void-free Copper Electrodeposition in High Aspect Ratio, Full Wafer Thickness Through-Silicon Vias with Endpoint Detection

High density interconnects are required for increased input/output for microelectronics applications, incentivizing the development of Cu electrochemical deposition (ECD) processes for high aspect ratio through-silicon vias (TSVs). This work outlines Cu ECD processes for 62.5 μm diameter TSVs, etched into a 625 μm thick silicon substrate, a 10:1 aspect ratio. Cu ECD in high aspect ratio features relies on a delicate balance of electrolyte composition, solution replenishment, and applied voltage. Implementing a CuSO4-H2SO4 electrolyte, which contains suppressor and a low chloride concentration, allows for a tunable relationship between applied voltage and localized deposition in the vias. A stepped potential waveform was applied to move the Cu growth front from the bottom of the via to the top. Sample characterization was performed through mechanical cross-sections and X-ray computed tomography (CT) scans. The CT scans revealed small seam voids in the Cu electrodeposit, and process parameters were tuned accordingly to produce void-free Cu features. During the voltage-controlled experiments, measured current data showed a characteristic current minimum, which was identified as an endpoint detection method for Cu deposition in these vias. We believe this is the first report of this novel endpoint detection method for TSV filling.

Deciphering the levelling mechanism of sorbitol for copper electrodeposition via electrochemical and computational chemistry study

A combined method using electrochemical analysis, molecular dynamic simulation and quantum chemical calculation was employed to reveal the effects of sorbitol on copper electrodeposition from the pyrophosphate bath. It was demonstrated that sorbitol is a desirable leveler. A possible mechanism responsible for the levelling improvement was that sorbitol displayed lower adsorption energy on the electrode surface than pyrophosphate, due to its smaller energy gap. Therefore, adding sorbitol into the pyrophosphate bath could significantly elevate the adsorption capacity of copper pyrophosphate complex ions {[Cu(P2O7)2]6−} on cathode, thereby increasing the diffusion coefficient (D) of [Cu(P2O7)2]6− and the number density (N) of copper nuclei. And the increased D and N are beneficial to improve the bath's levelling power. It should also be pointed out that sorbitol did not influence the purity and electrical conductivity of copper deposit as well as its nucleation mechanism, i.e., an irreversible and instantaneous nucleation process with three-dimensional growth of nuclei controlled by the diffusion of [Cu(P2O7)2]6−.

What Happens to Repeatable Low TCE Copper with Annealing

1. Introduction Since the Copper resistivity is second lowest next to the Silver, the Copper electrodeposits have been very intensively used in the wiring for the semiconductor and the printed circuit board (PCB). The Copper problem is the thermal coefficient of expansion(TCE). The TCE of Silicon is 2x10-6(1/K) and the TCE of Copper is 18x10-6(1/K). If the composite of the Silicon and the Copper warpage, protrusion or delamination occurs. This discussion is focused on the low TCE Copper with repeatable annealing. 2. Results 1) Figure 1 shows the TCE comparison with our repeatable low TCE Copper and the conventional Copper. X-axis is the expansion length and y-axis is the temperature. For the conventional Copper, the TCE is 18x10-6(1/K) and the expansion length is linear with the temperature. However, for our repeatable low TCE Copper, the TCE is 6x10-6(1/K) and 1/3 of the conventional Copper. The TCE of 6x10-6(1/K) repeats three times. This TCE of 6x10-6(1/K) starts after two times pre-annealing.2) Also we have run 200 cycles of -40℃ to 200℃ heat cycle test and measured the TCE and the resistivity. These TCE and the resistivity have been measured after 50,100,150 and 200 cycles.The TCE up to 300℃ for 50, 100 and 150 cycles show constant value and the TCE is lower with 200 cycles. The resistivities of 50,100,150 and 200 cycles become even lower than as deposit of zero cycle.The repeatable low TCE mechanism will be discussed at the meeting. Reference V. Q. Dinh and K. Kondo, ECS J.Solid State Sci. Technol., 6, P566-P569 (2017) Figure 1

Surface Characterization of High-Purity Copper Electropolishing and Electrodeposition Treatments in an Ionic Liquid

High purity (>99.9% composition) copper metal specimens were used in electropolishing treatments with an acid-free ionic liquid electrolyte prepared from quaternary ammonium salts as a green polishing solution. A prominent ionic liquid composed of ethylene glycol (HOCH2CH2OH) and choline chloride (HOC2H4N(CH3)3 +Cl−), sometimes abbreviated as 2EG:1VB4, has been used in other studies to successfully electropolish various metal alloys, but has only been used in limited capacity to polish pure rare earth metals (1-5), like copper, the focus of this study. Voltammetry and chronoamperometry tests were conducted to determine the optimum conditions for electrochemical polishing, while Atomic Force Microscopy (AFM) revealed nanoscale effectiveness of the ionic liquid relative to an industry standard acid polishing treatment of 1 Mol Phosphoric Acid (H3PO4). Surface morphology comparisons summarized electrochemical polishing efficiency of these relative treatments by providing root mean square roughness prior to and post-electrochemical polishing.Electropolishing using the ionic liquid revealed a mirror finish >10 times smoother than the same copper metal surface prior to electropolishing. This transition manifested in a marked change in root mean squared roughness from 167.15 nm to 14.744 nm and resulted in a mass loss of 0.0535 g for an electropolishing rate of 59.444 µg/s when subjected to a 900 second treatment with an average voltage of 1.5 V. By comparison, the phosphoric acid electropolishing treatment yielded an improvement in root mean squared roughness of 85.019 nm, resulted in a mass loss of 0.067 g for a higher electropolishing rate of 74.444 µg/s when subjected to the same treatment conditions. However, the it can be noted that while the elctropolishing rate via the acid solutionis greater, there are extreme peaks and troughs etched on the smoothed surface due to pitting at low current densities (Figure 1). Hydrogen contamination can be observed to affect the overall root mean square average of the region, which may be remedied via a relatively costly degassing treatment at temperatures up to 800 deg C to achieve more comparable results to the ionic liquid solution.After these electropolishing pretreatments, the resulting copper surfaces were subsequently electroplated during a 1 hour treatment at 2 V with an 2EG:1VB4 ionic liquid solution that had previously been used to electropolish high-purity niobium metal. A thin film of niobium metal coated the polished copper during electrodeposition resulting in an average mass gain of 0.002 g, and a root mean squared roughness of increase of -2.101 nm for the ionic liquid pretreated sample, compared to the -2.417 nm resulting roughness from the phosphoric acid pretreatment.As a result, pretreatments revealed a cheaper, recyclable, and environmentally-friendly approach to electopolishing pure copper was demonstrated to be more effective than an acidic industry standard electrolyte. Additionally, electrodeposition of niobium metals on each pretreatment sample provides a reasonably cost-effective method to combine the electroconductivity benefits of copper and ferroelasticity attributes of niobium metals. References Derek Lofis and Tarek M Abdel-Fattah, International Journal of Minerals, Metallurgy and Materials, 26(5), 649–656 (2019)Derek Lofts and Tarek M. Abdel-Fattah, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 511C, 113-119 (2016)Tarek M. Abdel-Fattah, Derek Loftis and Anil Mahapatro, Nanoscience and Nanotechnology, 5(2), 36-44 (2015)Tarek M. Abdel-Fattah, Derek Loftis and Anil Mahapatro, Journal of Surfaces and Interfaces of Materials, 3, 67-74 (2015)Tarek M. Abdel-Fattah, Derek Loftis and Anil Mahapatro, Journal of Biomedical Nanotechnology, 7(6) 794-800 (2011) Figure 1

Oscillatory Behavior in Cobalt Electrodeposition with 3-Mercapto-1-Propanesulfonate

As the copper interconnects used in integrated circuits1 are facing a physical limitation of resistivity increase in dimensions below the electron mean free path of Cu, alternative metals with a shorter electron mean free path such as cobalt (Co) are being explored as alternative conductors2. The damascene fabrication of Cu interconnects relies on the synergistic interactions between organic additives3. Such interactions result in bi- or even multi- steady states of deposition, which not only enables defect-free filling of Cu into small trenches but also often results in oscillatory behavior between these steady states during thin film deposition4. For example, the rapid self-breakdown of a suppressor-accelerator complex molecule mediated by a cuprous ion, together with the slow formation and accumulation of such a complex on the electrode surface, results in potential oscillations during galvanostatic deposition of Cu using 3-mercapto-1-propanesulfonate (MPS) as accelerator and a copolymer of imidazole and epichlorohydrin (Imep) as leveler4. While similar oscillations have also been reported with other commercial Cu chemistries, MPS or its dimer remains as the key component of the chemistry, the accelerator. Here, we are reporting a study of Co deposition with MPS as a single-component additive, where potential oscillations are also observed. A systematic study on the effects of several influencing factors (e.g. pH, Co2+/ MPS concentrations, current density and agitation) are thoroughly investigated and will be presented. A competitive adsorption mechanism is proposed to explain these observations. In addition, the effect of potential oscillation on the morphology of electrodeposited Co films will also be discussed.Figure 1 (a) shows the cyclic voltammograms of Co deposition on platinum rotating disk electrode with the absence and presence of 300 ppm MPS at pH = 4. The suppression effect of MPS on Co deposition is observed regardless of agitation. Figure 1 (b) shows the potential oscillation at different current densities with 300 ppm MPS at pH = 4 with the magnified oscillation curves included as insets. Stable oscillations are observed when the current is increased to -6.12 mA/cm2, which indicates that a threshold current or potential must be reached to enable such oscillation phenomenon. References Andricacos, P. C.; Uzoh, C.; Dukovic, J. O.; Horkans, J.; Deligianni, H., Damascene copper electroplating for chip interconnections. IBM Journal of Research and Development 1998, 42 (5), 567-574.Gall, D., Electron mean free path in elemental metals. Journal of Applied Physics 2016, 119 (8), 085101.Moffat, T.; Wheeler, D.; Huber, W.; Josell, D., Superconformal electrodeposition of copper. Electrochemical and Solid-State Letters 2001, 4 (4), C26-C29.Hai, N. T.; Odermatt, J.; Grimaudo, V.; Krämer, K. W.; Fluegel, A.; Arnold, M.; Mayer, D.; Broekmann, P., Potential oscillations in galvanostatic Cu electrodeposition: antagonistic and synergistic effects among SPS, chloride, and suppressor additives. The Journal of Physical Chemistry C 2012, 116 (12), 6913-6924. Figure 1

A novel strategy to electrodeposit high-quality copper foils using composite additive and pulse superimposed on direct current

As a crucial material for fabrication of lithium-ion battery current collector, the properties of electrodeposited copper foil are closely related to the battery performances. How to improve its properties is thus of great importance for battery design and manufacturing. In this paper, we reported a novel composite additive, consisting of collagen, glycerol, hydroxyethyl cellulose, and sodium polydisulfide dipropane sulfonate, for electrodeposition of high-quality copper foil from conventional acid copper sulfate bath. Meanwhile, a pulse superimposed on direct current was used during the preparation process of copper foil. It was demonstrated that the additive could improve the foil’s performances, through changing the kinetic parameters of copper electrodeposition in sulfate bath. The optimized bath has a higher allowable current density during superimposed current electrodeposition, in contrast to the situation in direct current electrodeposition. This may then lead to an increase in deposition rate of copper foil, and a further improvement in surface roughness, grain size, residual stress, as well as elongation. Specially, the superimposed current offers a number of adjustable parameters for modulating copper foil’s properties in a wide range.

Bottom-up Copper Electrodeposition in 20:1 Aspect Ratio, 20 Μm Pitch through Silicon Vias

Heterogeneous integration (HI) offers a path to increase bandwidth density and reducing power consumption per area for advanced microelectronic systems by minimizing fan-in/out structures and reducing parasitics. To achieve state-of-the-art areal bandwidth density, 3D HI is required with through silicon vias (TSVs) with extremely tight interconnect pitches (< 50 µm) and high aspect ratios. Fabrication and fill of these proposed TSVs pose significant challenges including substrate thinning, high aspect ratio deep reactive ion etching (DRIE), conformal thin film deposition to deposit insulating layers as well as seed metals for electrodeposition, and void-free fill of the TSVs. Here, we target an interconnect pitch of 20 µm and TSV diameter of 5 µm. At these dimensions, DRIE lag limits the TSV depth to 100 µm. The TSVs are integrated using a via-last scheme with atomic layer deposition (ALD) Al2O3 as the insulating liner and ALD Pt serving as both the barrier and electrochemical deposition (ECD) seed liner. In this work, we describe the integration scheme for these high density TSVs and focus on the ECD process for achieving a void-free fill with Cu as well as characterization approaches using focus ion beam (FIB) cross sectioning.Recent work on Cu ECD has demonstrated the efficacy of a two-additive acid sulfate electrolyte system based on a chemistry exhibiting a S-shaped negative differential resistance voltammogram1. The electrodeposition system presented is a 1.0 mol/L CuSO4 – 0.5 mol/L H2SO4 acid sulfate electrolyte containing a polyether surfactant and halide additive which promotes a bottom-up Cu growth profile via positive feedback between localized disruption of adsorbed polyether-halide layer and metal deposition. This electrolyte has been applied to potentiostatic filling of a variety of geometries with both micro-scale1 and mm-scale2 TSVs as well as current controlled bottom-up filling from a conformally conductive seed metal3. This system relies on fine tuning of applied bias, adsorbate concentrations, convection, and deposition time to ensure a bottom-up deposition regime is maintained in a particular via geometry.Previous work developed parameters for filling 600 µm deep 5:1 aspect ratio TSVs and the same parameters were applied to 600 µm deep 10:1 aspect ratio TSVs with drastically different filling results.2 In this work, we further adjust the relevant ECD parameters to fill 20:1 aspect ratio TSVs that are 100 µm deep.In fine pitch, high aspect ratio ECD, characterization of the deposited fill profile is important and is difficult to obtain using mechanical cross-sectioning. Here, we use a characterization approach which relies on focused ion beam (FIB) cross-sectioning rather physical grinding and polishing. The FIB mills into the surface of the sample at a 38º angle with respect to the surface of the sample while the electron beam collects a series of images looking down at the sample, as shown in Figure 1.The series of images collected throughout the FIB milling process are then reconstructed to generate a cross-sectional image. FIB cross-sectioning is also used to provide granular detail about deposition morphology and grain size of the ECD Cu that can be lost during mechanical cross-sectioning. Figure 2, shows a top down scanning electron microscopy image of the TSV sample after milling at 38º and the resulting reconstructed cross-sectional image. T. P. Moffat and D. Josell, J. Electrochem. Soc., 159, D208 (2012).L. A. Menk, D. Josell, T. P. Moffat, E. Baca, M. G. Blain, A. Smith, J. Dominguez, J. McClain, P. D. Yeh, and A. E. Hollowell, Journal of the Electrochemical Society, 166 (1) D3066-D3071 (2019).L. A. Menk, E. Baca, M. G. Blain, J. McClain, J. Dominguez, A. Smith, and A. E. Hollowell, Journal of the Electrochemical Society, 166 (1) D3226-D3231 (2019) Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. This work was funded by the DARPA Photonics in the Package for Extreme Scalability (PIPES) program under award number HR001119S0004. The views, opinions, and/or findings expressed are those of the author(s) and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government. Figure 1

Heat transfer enhancements in heat pipe constructed with a copper porous microstructure

ABSTRACT This paper aims to measure heat transfer performance in heat pipe cooling device under constant heat flux condition. Emphasis is placed on a surface modification of heat pipe to enhance heat transfer performance. The surface fabricated here is coated by hydrogen codeposition of copper electrodeposits to modify the surface’s porosity and roughness. It is found that thermal resistance for the coated surface is suppressed to 16% as compared to the uncoated surface, that is, the surface modification results in attenuation on heat pipe’s thermal resistance, especially for low heat flux. This characteristic, by an electron microscope, is explained as the formation of the rough inner surface in heat pipe which supports higher heat transfer as compared to the uncoated surface.

A comparative investigation of the effects of some alcohols on copper electrodeposition from pyrophosphate bath

As a kind of environmentally friendly and highly effective additive, alcohols have broad application prospects in copper electrodeposition. It is highly desired to expand the types of alcohol additives. In this study, electroplating of copper coatings from a pyrophosphate bath in presence of glycerol, erythritol, xylitol and glucose, respectively, were comparatively investigated, including nucleation mechanism, electrochemical kinetic parameters, surface morphology, purity as well as electrical conductivity. It was demonstrated that glucose was a desirable grain refiner. A possible mechanism responsible for the high effectiveness of glucose is that the pyrophosphate bath has the maximum charge transfer coefficient as well as the minimum diffusion coefficient of copper ions after its addition, thereby inhibiting the growth of copper nucleus. The study offers researchers with more options in the selection of alcohol additives for copper electrodeposition.

Study of the electrochemical behavior of printed circuit boards (PCBs) leaching solutions using glycine and copper recovery by electrodeposition from leachate solutions

The present work focuses on the study of the electrochemical behavior of printed circuit boards (PCBs) leaching solutions using glycine and copper recovery by electrodeposition from leachate solutions. The recovery is done in a minimum number of steps and under ambient conditions of temperature and pressure. Printed circuits boards (PCBs) were pulverized and sieved, which allowed to obtain a PCBs powder of particle size fraction ≤ 1 mm. X-ray fluorescence spectroscopy analysis was used for PCBs powder characterization before and after leaching. The copper leaching has been carried out from PCBs powder in the open air, under ambient conditions of temperature and pressure using a buffer solution of glycine. UV–Vis spectrophotometry and atomic absorption spectrophotometry were utilized to determine the efficiency of copper leaching. Cyclic sweep voltammetry and chronoamperometry were employed to obtain informations on the electrochemical behavior of metals in the leaching solutions and then compared to that of synthetic solutions containing Cu (II) ions. UV–Visible spectrophotometry was used to determine the nature of the formed complex. Electrodeposition technique was applied in order to recover copper in powder form. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to examine the surface morphology and chemical composition of electrodeposited copper. The leaching solutions show exactly the same electrochemical behavior as the synthetic cupric solutions with two reduction peaks and a single oxidation peak, which demonstrates the high selectivity of glycine for copper. The chronoamperometric results confirm those obtained by voltammetry. UV–Visible spectrophotometry showed that the complex formed is [Cu(Gly)2] for the synthetic solutions as well as for the leachate solutions. Selective copper leaching was achieved with an efficiency of 92.5%. The resulting leachate solution was used directly for copper electrodeposition allowing the recovery of metallic copper as a pure product.

Preparation of highly (111) textured nanotwinned copper by medium-frequency pulsed electrodeposition in an additive-free electrolyte

A simple and novel strategy for fabricating highly (111) textured nanotwinned copper (nt-Cu) by using medium-frequency (10–1000 Hz) pulsed electrodeposition in an ultra-low Cu2+ concentration electrolyte without additives is reported. First, direct-current electrodeposition was conducted to determine the appropriate Cu2+concentration, which is critical for subsequent pulsed electrodeposition. Highly (111) textured Cu with densely packed coherent nanotwins was successfully prepared by varying the pulse frequency. The mechanical properties and thermal stability of the as-deposited Cu were also studied. The twin thickness was found to decrease with an increase in the pulse frequency. The spiral feature of the hexagonal pyramid on the top of the nt-Cu indicated that the formation of periodic twin structures could be the result of the screw dislocation-induced growth. The as-prepared nt-Cu showed the same thermal stability and mechanical properties as those prepared using existing preparation methods. The outcomes of this work deepen the understanding of the formation of nanotwin structures in copper electrodeposits and broaden the application of this process in the industry.

Copper electrodeposition under a weak magnetic field: effect on the texturing and properties of the deposits

The effect of a weak magnetic field (induction of 0.5 to 0.7 mT) on the electrodeposition process and the formation of crystallographic texture, morphology and properties of copper deposits has been considered. Electrodeposition studies were performed using cyclic voltammetry, chronoamperometry, and chronopotentiometry. X-ray texture analysis and scanning electron microscopy observations were used to study the texture and the morphology of the copper deposits. Some of their properties were obtained by measuring their microhardness and reflectivity. The effects of decreasing the rate of copper electrodeposition, enhancing texture formation and refinement of grain aggregates of the surface of copper films under the influence of a weak magnetic field have been evidenced. The interrelation of the texture and morphology of the copper electrodeposit surface with their microhardness and reflectivity have been revealed. The conditions for obtaining copper deposits with enhanced microhardness and reflectivity have been determined. It is shown that the electrochemical deposition with a weak magnetic field is a promising direction for obtaining materials with desired properties, without using strong magnetic fields and adding surfactants to the electrolyte.

Effect of zinc ions on copper electrodeposition in the context of metal recovery from waste printed circuit boards

This paper evaluates the effect of zinc ions on copper electrodeposition. Although zincis not found at significant concentrations in conventional industrial copper electrolytes, in copper-concentrated sulfate leach liquors produced in the treatment of waste printed circuit boards (WPCB) its concentration may reach high levels. In this context, the effect of zinc on physical-chemical properties of copper sulfate electrolyte, performance indicators of copper electrowinning, and morphology and crystal structure of copper deposits were investigated. Copper electrowinning tests indicated that the current efficiency was negligibly affected by adding zinc (up to 75 g L−1) to synthetic copper sulfate electrolyte (30 g L−1 Cu2+ and 110 g L−1 H2SO4) at two levels of current density (250 A m−2 and 450 A m−2) and fixed temperature (35 °C). The energy consumption slightly increased: up to 4% at 250 A m−2 and up to 3% at 450 A m−2, both effects at 75 g L−1 Zn2+. This behavior was ascribed to decreases in the electrical conductivity of the electrolyte by adding zinc (up to 35% at 75 g L−1) and consequent increases in the ohmic drop and cell voltage. Electrochemical measurements by cyclic voltammetry and linear sweep voltammetry (LSV) indicated no cathode polarization by adding this impurity to the electrolyte, even at the highest level. In turn, the addition of zinc caused significant drops in the limiting current for copper deposition (e.g., the values recorded at 100 min−1 decreased about 60% when 75 g L−1 Zn2+ was added to the electrolyte). This effect was explained by the measured increases of electrolyte viscosity and calculated decreases of copper diffusion coefficient. The addition of 75 g L−1 Zn2+ to the electrolyte increased its viscosity in the order of 76%, and decreased the diffusion coefficient in the order of 45%. Regarding the effect of zinc on product quality, SEM analysis revealed negative effects on the morphology of the deposits (i.e., higher roughness and nodulation), mainly at the highest concentration of zinc and highest current density. XRD analysis showed modifications in the growth pattern of copper crystals under some conditions. For example, the addition of 30–75 g L−1 Zn2+ to the electrolyte led to the formation of (220) textured deposits at 250 A m−2. The findings of this work may be helpful to define proper operating conditions for copper electrowinning in order to produce high quality products, thus maximizing the recycling of copper from the selected secondary source.

ELECTRODEPOSITION OF COPPER IN ULTRASONIC FIELD FROM SPENT ETCHING SOLUTIONS

It is studied the regeneration and utilization possibility of spent nitric acid solutions for copper and its alloys etching for the creating an environmentally clean closed-cycle production of regenerated electrolytes. It is established that some difficulties arise when using the electrochemical method in the regeneration process of these solutions: during copper electrodeposition from spent copper-containing nitric acid solutions, nitric acid decomposes with vigorous evolution of nitrogen dioxide, which prevents copper ions reduction. In order to suppress the side process, it was proposed to partially neutralize the solution, not reaching the pH of copper hydration (pH 4-5). It is revealed that a decrease in the concentration of metal cations occurs due to partial neutralization of the nitric acid contained in the solution by concentrated alkali solution. The pulsed electrolysis mode was used to increase the efficiency of the metal ions electrodeposition process from dilute solutions. It is established that the using of pulsed electrolysis can reduce diffusion difficulties that arise in a dilute spent nitric acid copper-containing solution, thereby intensify the process of copper electrodeposition. It is showed that the prospects of using ultrasound to increase the rate of the copper electrodeposition process and improve the quality of the resulting coating. It is studied the ultrasound field effect on nucleation during copper electrodeposition in a pulsed mode from a partially neutralized electrolyte simulating the spent nitrate solution of etching copper alloys on various materials by the potentiostatic. It is established an increase in the number of copper nucleus that form on the studied substrates (graphite, copper, steel) at the initial time under the action of an ultrasonic field. It is concluded that the use of ultrasound allows to intensify the process of metal electrodeposition. An increase in current efficiency during copper electrodeposition and an increase in the copper extraction degree using ultrasonic field are achieved at lower cathodic current densities in a pulse. It is substantiated using of graphite foil and steel as cathode materials in the copper extraction from the spent nitric acid etching solution.

Development of technology for fabrication of prototype ion extraction grid for fusion research

• Ion extractor grids are the heart of any NBI system. • Ion extractor grid fabrication involves various critical technologies. • Friction welding for joining of dissimilar metals of SS304 L rod and OFHC copper plate. • Electro-deposition technique is best for making embedded coiling channels inside thin OFHC copper plate. • Surface flatness of 100 μm of grid is most important during CNC machining. Steady-state Superconducting Tokamak (SST-1) has a provision for a positive hydrogen ion-based Neutral Beam Injection (NBI) system. This system has a capability of injection of neutral hydrogen beam power of 1.7 MW at 55 kV. This NBI system consists of a 3-grid accel-decel ion extractor system. Each grid has 774 apertures distributed in the area of 23 cm × 48 cm on the OFHC copper plate. During beam operation grid received maximum heat load of ∼1.75 MW/m 2 which is removed by a dense network of 22 semi-circular ( r = 1.1±0.05 mm) cooling channels embedded between the rows of shaped apertures. The water flow velocity inside the cooling channel is 13 m/s and the pressure drop is 9 bar. To maintain the high electric field (∼7 kV/mm) between grids, the required surface flatness of the OFHC copper plate is 100 μm. Another requirement is positional tolerance of aperture of ±60 μm. All these critical requirements imply that the fabrication of the ion extractor grid is very complex and several technologies are involved: (i) Friction Welding (FW) for joining of dissimilar metals of SS304 L rod to the specific location of OFHC copper plate for the fabrication of water manifold of the grid. This has been successfully developed and obtained FW joint strength of 264 MPa (ii) 2.5 mm thickness electro-deposition of OFHC copper for making embedded cooling channels (iii) Precision CNC grid machining. This paper shall describe the development of these technologies for the manufacturing of the extractor grid.

Trace bis-(3-sulfopropyl)-disulfide enhanced electrodeposited copper foils

Smooth and strong copper foils are highly required for the development of printed circuit boards and Li-ion batteries. Adding additives is an efficient and low-cost method to enhance electrodeposited copper foils. Here we chose Bis-(3-sulfopropyl)-disulfide (SPS) as the additive and investigated its concentration on the surface roughness and tensile strength of the electrodeposited copper foils. A copper foil with the smoothest surface (Rz = 2.1 μm) and the highest tensile strength (∼338 MPa) was prepared with 1.5 mg/L SPS. The contact angle on the copper foil decreased with the reduction of surface roughness. The enhancing mechanism of the SPS was investigated by scanning electron microscopy and X-ray diffraction. The refined grain and enhanced (220) texture were considered to be the radical reason for the smooth and strong copper foils. The electrochemical results prove the suppressing effect is related to the SPS adsorption.

Metallic Surface Coating of Polymeric Parts Produced by Additive Manufacturing Process

Metal coating films were deposited on the surface of the pieces of non-conducting polymers, acrylonitrile butadiene styrene (ABS), high impact polystyrene (HIPS) and poly (lactic acid) (PLA). These three polymers have been used since they are the main raw materials available for fusion and deposition molding equipment. In order to achieve surface metallization by electrodeposition, it was necessary to apply a pre-treatment using the chemical polymerization technique in solution with the electroconductive polymer polypyrrole (PPy) was deposited on the specimens. A uniform layer of PPy was deposited on the surface of the specimens of the ABS and HIPS polymers, while in the specimen of the polymer PLA this layer showed uniformity faults. After this pretreatment was possible to perform copper electrodeposition, creating the metallic coatings on the ABS / PPy, HIPS / PPy and PLA / PPy surfaces. This metallic coating was uniform in all specimens except the one of the PLA polymer that was not sanded. The adhesion of the coating was evaluated by the adhesion test with tape and the quality of the appearance (absence of visual defects), the morphology, the uniformity, the thickness, the conductivity and the adhesion quality of the films were analyzed.