Thin Copper Foil Research Articles

Effect of heterogeneous microstructures on mechanical properties of thin gradient nanotwinned copper foils

Strengthening of metals generally weakens ductility, but gradient strengthening is an exception. Heterogeneous microstructures, characterized by variations in grain size and twin spacing (structural gradients), were incorporated into 20-μm thin nanotwinned copper (NT-Cu) foils to enhance their mechanical properties. Four distinct heterogeneous NT-Cu samples, including two-layer (2L) structures and three-layer (3L) structures, were produced through rotary electroplating. The mechanical properties, work hardening rates, and microstructural features of these samples were systematically analyzed and compared. The results showed that an increase of 9.5 %, 6.4 %, and 20.1 % in ultimate tensile strength, yield strength, and work hardening rate, respectively, could be achieved in 3L structures, and the elongation was maintained at 5.5 %. The significant structural gradients and two interfaces of 3L structures were confirmed to stimulate the production of geometrically necessary dislocations (GNDs), which increased strength and work hardening rate. Two interfaces of 3L structures also contributed to the efficient moderation of plastic strains and thus improved the ductility. This study significantly enhances the strength and ductility of thin electroplated NT-Cu foils by introducing heterogeneous microstructures, promoting the application of thin NT-Cu films in electric vehicles, batteries, and the semiconductor industry.

Competition between microstructural factors affecting growth of abnormally large grains in thin Cu foils

Grain boundary types and local boundary curvatures are generally considered to be important microstructural factors controlling grain boundary migration during grain growth. In this work, grain growth in thin copper foils is studied during annealing at a temperature of 1040 °C near the melting point by ex-situ experiments and Monte Carlo simulations. Few grains, stimulated by slight deformation at the sample edge, are observed to grow abnormally into the cube-oriented recrystallized microstructure with columnar grains spanning the foil thickness. The grain boundaries of these abnormally growing grains and the grain sizes in the adjacent polycrystalline recrystallized regions are analyzed. The experimental results suggest that spatial heterogeneities in the distribution of small recrystallized grains have a significant effect on the migrating boundaries. Potts model simulations confirm that grain boundary segments with small grains in front are more likely to migrate than segments facing coarser grains. The simulations also demonstrate the importance of grain morphology. Altogether, this work highlights the effects of a heterogeneous recrystallized microstructure on abnormal grain growth in thin foil samples.

Bromine-enhanced polarization for strengthening ultra-thin copper foil in lithium-ion battery

Reducing the weight of the negative current collector is an effective strategy for lightweighting vehicle batteries. Herein, thin copper foil with high tensile strength was prepared through electrodeposition in Br−-based aqueous solution. The synergistic effect of additive Br−, polyethylene glycol (PEG), Bis-(sodium sulfopropyl)-disulfide (SPS) on the microstructure and tensile strength of the copper foils have been systematically explored. It was found that the addition of Br− modifies the microstructure of copper via grain refinement, thereby enhancing the mechanical properties of copper foil. The obtained copper foil reaches an enhanced tensile strength of 469.8 N/mm2 and an elongation of 2.2%. The results of electrochemical measurements confirm that Br− enhances electrochemical polarization of PEG and attenuates the acceleration of SPS. The improved mechanical properties of copper foils are attributed to the closer proximity and stronger adsorption energy between Br− and Cu atoms, which results in a synergy of grain refinement and nanotwinned grains associated with increased dislocation density as well as dislocations entangled around nanotwin GBs.

Experimental study and modeling of the wettability of fluorine graphene. Corrosion behavior of the fluorine graphene layer on a copper substrate

Fluorographene (FG) is a high-quality 2D insulator, which is effectively used as the atomically thin tunnel barrier. To date, the most common idea is that the complete fluorination of graphene (G) leads to an increase in hydrophobicity. We have shown that in reality fluorination leads to superhydrophilicity and to a significant increase in the defectiveness of the graphene layer. Without hydrocarbons, as well as due to the high defectiveness and superhydrophilicity, the corrosion current of FG is an order of magnitude higher than for pure copper and two orders of magnitude higher than for G synthesized on copper. The simulation results confirm experimental data on FG superhydrophilicity after prolonged fluorination. Thus, in order to achieve high hydrophilicity, it is not necessary to create hydroxyl groups on the surface of FG. A higher concentration of fluorine (the C/F composition ratio) is realized on a thicker copper plate with a graphene layer, compared to thin copper foil. Different fluorine concentrations are associated with different sizes of crystal grains, their orientation, as well as defectiveness and the number of graphene layers. The corrosive effect leads to a decrease in roughness and a multiple decrease in the amount of F on the FG.

Proton Beam Range and Charge Verification Using Multilayer Faraday Collector.

A daily quality assurance (QA) check in proton therapy is ensuring that the range of each proton beam energy in water is accurate to 1 mm. This is important for ensuring that the tumor is adequately irradiated while minimizing damage to surrounding healthy tissue. It is also important to verify the total charge collected against the beam model. This work proposes a time-efficient method for verifying the range and total charge of proton beams at different energies using a multilayer Faraday collector (MLFC). We used an MLFC-128-250 MeV comprising 128 layers of thin copper foils separated by thin insulating KaptonTM layers. Protons passing through the collector induce a charge on the metallic foils, which is integrated and measured by a multichannel electrometer. The charge deposition on the foils provides information about the beam range. Our results show that the proton beam range obtained using MLFC correlates closely with the range obtained from commissioning water tank measurements for all proton energies. Upon applying a range calibration factor, the maximum deviation is 0.4 g/cm2. The MLFC range showed no dependence on the number of monitor units and the source-to-surface distance. Range measurements collected over multiple weeks exhibited stability. The total charge collected agrees closely with the theoretical charge from the treatment planning system beam model for low- and mid-range energies. We have calibrated and commissioned the use of the MLFC to easily verify range and total charge of proton beams. This tool will improve the workflow efficiency of the proton QA.

Abnormal grain growth in thin copper foils during high-temperature annealing

We investigate grain growth at 1000 °C, a critical temperature for abnormal grain growth in copper foils. By ex-situ annealing experiments at 1000 °C, it is found that abnormal grains grow through the entire sample thickness, forming a polycrystalline structure with a single layer of grains. The migration of the boundaries surrounding the abnormally large grains are characterized by optical microscopy and electron backscatter diffraction. The migration rates are found to vary significantly from place to place, which is analysed based on boundary characteristics, i.e., misorientation and boundary curvature, and the size distribution of the neighbouring grains.

Underwater microsecond timescale electrical explosions of aluminum and copper foils

We present results on underwater electrical explosions of thin aluminum and copper foils using a generator delivering ∼200 kA current amplitude, ∼0.9 μs rise time pulses. Time-resolved shadow imaging displays the generation of a strong planar shock wave in water in the vicinity of the exploding foil. Using time-resolved spectroscopy, aluminum oxide (AlO) absorption bands were observed in a Planckian-like spectrum, indicating that aluminum combustion starts when aluminum vaporizes. It is also shown that the strongest shock wave is obtained for the largest linear energy deposition rate to the foil.

A Study on the Optimization of Welding Parameters for Titanium Drums Using Optimization Algorithms

An electrolytic copper foil uses titanium drums, which exhibit excellent corrosion resistance and can produce thin electrodeposited copper foils. The appropriate technology for producing thin copper foils is required as electronic products become lighter, thinner, shorter, and smaller. Thus, the importance of titanium drum manufacturing technology, which affects the specifications of electrolytic copper foils, is emphasized. In this study, thermo-elastic-plastic analysis is performed to select an appropriate range of welding process parameters for titanium drums. In addition, using a range of welding process variables derived from analysis, GBO and GPS algorithms, which are optimization algorithms, are developed to derive objective and restriction functions as well as to select the optimal algorithm.

Influence of Diffusion Bonding Pressure on Microstructural Features and Strength Performance of Dissimilar Ti–6Al–4V Alloy and AISI 304 Steel Joints Developed Using Copper Interlayer

Abstract The joining of Ti–6Al–4V (Ti64) alloy and AISI 304 austenitic stainless steel (ASS 304) carries significant importance in aeroengines for turbine blade applications. However, it is difficult to join using fusion welding. The fusion welding of Ti64 alloy and ASS 304 steel promotes the evolution of various Fe–Cr–Ti and Fe–Ti intermetallics in weld zone owing to limited solid solubility of Fe, Cr, Ti, and Ni with each other. The evolution of these intermetallics deteriorates the strength performance of joints. Hence for joining Ti64 alloy and ASS 304 steel, vacuum diffusion bonding (VDB) method is employed with thin copper (Cu) foil as an interlayer. The DB pressure extends significant influence on microstructural evolution and strength of joints. So, for the feasibility of joining Ti64 alloy and ASS 304 steel, the effect of DB pressure on microstructure and strength of joints is investigated. Results showed that the dissimilar joints of Ti64 alloy and ASS 304 steel developed using the DB pressure of 14 MPa exhibited greater lap shear strength (LSS) and bonding strength (BS) of 180 MPa and 268 MPa, respectively. It is attributed to the improved coalescence of joining interface and the development of ideal bonding width with the least amount of embrittlement consequences. An increase in DB pressure increases the width of the diffusion region which promotes the development of detrimental intermetallics of Ti–Fe and deteriorates the strength of dissimilar joints.

Predicting the drop size passing through a superhydrophobic orifice

Superhydrophobic surfaces can be utilized in various applications, such as enhanced heat transfer, anti-icing, self-cleaning, and viscous drag reduction. In this work, we investigated the water droplet size separation using superhydrophobic surfaces, which is relatively new and unexplored research field, but yet promising for pharmaceutical and medical applications. We developed a theoretical model for predicting the diameter of a droplet passing through a smaller superhydrophobic orifice by considering the balance of forces, geometrical characteristics, and the surface wettability. For verification of the model, experimental water droplet size separation was conducted using a thin superhydrophobic copper foil with a laser-cut orifice with a diameter ranging from 1.2 to 2.1 mm. A comparison of the experimental and analytical results has shown that the error of the model is less than 20% within the model's validity range with the upper limit at the capillary length of the fluid. By moving away from this limit toward smaller droplet diameters, the accuracy of the model improves and reaches an error of less than 7% at the smallest used orifice diameter of 1.2 mm.

Investigations on laser beam welding of thin foils of copper and aluminum regarding weld seam quality using different laser beam sources

Nowadays, there is a strong and growing ambition to switch from combustion technology to battery-electric drives, and energy storage is spotlighted. Laser beam welding is an appropriate and favorable welding technology in battery production. Due to the high welding speed, the local heat input, the contact freeness efficient, and automatable processes can be established. Materials used in batteries for electrodes that have to be connected are commonly copper and aluminum. Specifically, copper is highly reflective for widely used infrared laser beam wavelengths. Furthermore, the thickness in the area of 10 μm is quite challenging to deal with, in terms of gap free clamping and avoidance of damage to the material as well as distortion during welding. There is a fine line regarding energy input between burning the material and generating a lack of fusion. In the presented research, welding approaches with different laser beam sources emitting laser beams with infrared wavelengths, various beam shapes, and welding modes (continuous and pulsed) are studied. A total of 40 copper foils with a thickness of 10 μm and 40 aluminum foils with a thickness of 15 μm are welded to similar sheet metals. Aim of the process development are welds with high quality and high connection widths to provide the best electric conductivity.

A Comparative Study on Fatigue Response of Aluminum Alloy Friction Stir Welded Joints at Various Post-Processing and Treatments

The present study examines the fatigue of friction stir welded (FSW) aluminum 6061, 7075, 1060 joints followed by (i) in situ and sequential rolling (SR) processes, (ii) plastic burnishing (iii) solution-treatment artificial aging (STA), (iv) local alloying through depositing thin copper foils, and (v) inserting alumina powder in the weld nugget zone (NZ). The microstructural features and fatigue life of post-processed joints were compared with those of as-welded joints. The in situ rolling technique offered simultaneous rolling and welding operations of aluminum joints, while through the sequential rolling process, the top surface of FSW joints was rolled after the welding process. The fatigue life of in situ rolled samples was increased as the ball diameter of welding tool increased. The fatigue life of friction stir welded joints after a low-plasticity burnishing process was noticeably promoted. The addition of 1 wt.% alumina in the NZ of joints resulted in a significant elevation on fatigue life of friction stir spot welded joints, while an increase in alumina powder to 2.5 wt.% adversely affected fatigue strength. Weld NZ was alloyed through the insertion of copper foils between the faying surfaces of joints. This localized alloy slightly improved the fatigue life of joints; however, its effects on fatigue life were not as influential as STA heat-treated or in situ rolled joints. The microstructure of weld joints was highly affected through post-processing and treatments, resulting in a substantial influence on the fatigue response of FSW aluminum joints.

Effects of JGB Additives on the Microstructures and Electrical Properties of Electroplated Copper Foil

Extremely thin film high quality copper foil is required to ensure high performance in electronics and slimness in secondary batteries. During the electroplating of copper foil, Janus Green B(JGB) and Collagen were introduced as additives to the electrolytes to study their effects. The structural and electrical properties of the electroplated copper foil were evaluated. When each additive was added individually, the potential was increased. Specifically, the potential of the group with 30 ppm added collagen was about 27% higher rather than the non-additive group. When Cl- ions and MPSA(3-mercapto-1-propane sulfonic acid) were added to the electrolytes without collagen and JGB, the surface roughness(Rz) increased by about 136% to 2.24 μm compared to the non-additive group. This was the highest value among all groups. However, a uniform layer with a surface roughness value below 0.3 μm was formed when less than 30 ppm and 10 ppm collagen and JGB were added, respectively, to the electrolyte. The direction of crystal growth with the JGB additives tended to go forward to the (220) direction, and the crystal size was reduced by 10~27% compared to the non-additive group. The addition of Collagen is necessary to reduce the difference in resistivity of the shiny layer and right matte layer. JGB additives were required to reduce the deviation in grain size. The results confirmed that the accelerators, inhibitors and leveler need to be properly added to form a copper plating layer with low surface roughness and to reduce differences in crystal texture of the shiny layer and right matte layer. Copper foil can be safely and uniformly deposited from electrolytes with JGB below 10 ppm and collagen below 30 ppm.

Long-pulse diagnostic calorimeter for the negative ion source testbed BATMAN upgrade.

The RF-driven negative ion source testbed BATMAN upgrade is being developed at IPP Garching in the framework of the ion source development for ITER and DEMO neutral beam injection systems. The testbed has recently been enhanced to allow for steady state operation with a focus on beam optics studies. The previous titanium sublimation pumps and inertial calorimeter limited the beam pulse length to about 6s every 3min. The upgrade comprises a long-pulse compatible, actively cooled diagnostic calorimeter. This has been designed and is currently being manufactured to substitute the inertially cooled calorimeter that has limited diagnostic capabilities. The new diagnostic calorimeter consists of a copper plate with dimensions of 910 × 660 × 25mm3 placed about 2m from the ion source extraction grids, and through a novel solution, it will provide a 2D profile of beam power density with a 20mm spatial resolution. Water flowing through cooling channels embedded in the copper plate will actively cool the calorimeter, which is loaded with about 160 kW beam power at ITER-relevant current density, but 45 kV acceleration. A fraction of the beam will pass through many small apertures (ø2mm) positioned in the calorimeter plate and will be collected by thin (0.2mm) copper foils attached to the calorimeter back side. Evaluation of power density will be performed by measuring the temperature of the heat flux foils with a high-resolution infrared camera observing the calorimeter from the back side and calibrated by thermocouples.

Fatigue response of friction stir welded joints of Al 6061 in the absence and presence of inserted copper foils in the butt weld

The present study examines the impact of inserted copper foil on n mechanical characteristics and fatigue strength of aluminum 6061 butt joints welded through the Friction Stir Welding (FSW) process. Thin copper foils were inserted between the faying surfaces of the sheet joints alloying Al 6061 locally with copper foil over FSW operation. Test specimens were then cut off from the welded plates to examine the quasi-static and fatigue behavior of the joints. The load-controlled condition tests were conducted on the specimens with a stress ratio of R = 0.1. Insertion of copper foils of 100 μm and 200 μm in the stirred zones, improved tensile strengths respectively 48 % and 31 %. The fatigue life of alloyed joints was improved as compared to as-welded joints in the absence of foils. A three-dimensional finite element (FE) analysis was employed to simulate the maximum stress and strain values in the weld zones. Weld regions due to their different mechanical properties experienced different stress magnitudes. The simulated stress and strain components were then used to predict uniaxial fatigue lives of FSW joint samples through the Smith-Watson-Topper (SWT) approach.

Analysis Result of Delivery Foil Profile of Ultra–Thin Copper Foil Rolling with 6X Mill

Analysis Result of Delivery Foil Profile of Ultra–Thin Copper Foil Rolling with 6X Mill

Chemical vapour deposited graphene: substrate pre-treatment, growth and demonstration as a simple graphene-based SERS substrate

In chemical vapour deposition (CVD) of graphene, surface roughness and purity of the copper substrate are very crucial for obtaining uniform films. Even though electrochemical polishing is an effective technique for obtaining homogeneous graphene films, most of the experiments adopt complex experimental parameters like electrolyte heating, stirring and use of additives for better results. These are not applicable to thin copper foils used in CVD of graphene. In the present study, a simple electrochemical procedure is developed for deposition of high-quality graphene films with good coverage. The depositions of graphene films on bare and polished copper foils for the same growth conditions are analysed using various microscopic techniques. The uniformly grown graphene on copper is then directly employed as a surface-enhanced Raman scattering (SERS) substrate along with plasmonic silver nanoparticles. A simple SERS substrate having a reasonable detection limit of $$10^{-10}$$ M for R6G is achieved with uniform SERS signals over a large area. The homogeneity of SERS substrate can be attributed to the uniformity of the deposited graphene film. A simple and efficient SERS substrate using conventional methods is achieved through the incorporation of chemical vapour deposited graphene. The study covers the growth of CVD graphene film starting from substrate pre-treatment, various analyses of the film and finally the application in SERS.

Electroless Deposition of Automatically Shedded Thin Copper Foils.

Electroless deposition (ELD) is a process widely used for the production of thin metal films, but stripping the films from the substrate remains challenging. Here, we report a low-cost ELD method for the large-scale production of freestanding copper (Cu) foils in a short time of 25-55 min. By atomizing a thin (<100 nm) sacrificial layer of chitosan with weak glycosyl bonds and a high degree of deacetylation on the glass substrate, the chitosan is completely decomposed in the process of Cu-deposition, producing automatically shedded Cu foils with varied thicknesses from 746 nm to 8.33 μm and high elastic modulus. When used as battery current collectors, the thin Cu foils with enhanced adhesive fastness and contact areas greatly enhance the capacity and rate capability of graphite anodes. Compared with the commercial Cu current collectors, both the battery capacity and energy density are increased by 429.6 and 484.1%, respectively. The reported approach can be extended for fabricating other metal foils such as nickel with properties appealing for applications.

Impact of a parallel magnetic field on radiation dose beneath thin copper and aluminum foils

Purpose: The RF coils for magnetic resonance image guided radiotherapy (MRIgRT) may be constructed using thin and/or low-density conductors, along with thinner enclosure materials. This work measures the surface dose increases for lightweight conductors and enclosure materials in a magnetic field parallel to a 6 MV photon beam. Methods: Aluminum and copper foils (9–127 μm thick), as well as samples of polyimide (17 μm) and polyester (127 μm) films are positioned atop a polystyrene phantom. A parallel plate ion chamber embedded into the top of the phantom measures the surface dose in 6 MV photon beam. Measurements (% of dose at the depth of maximum dose) are performed with and without a parallel magnetic field (0.22T at magnet center). Results: In the presence of a magnetic field, the unobstructed surface dose is higher (31.9%Dmax versus 22.2%Dmax). The surface dose is found to increase linearly with thickness for thin (<25 μm) copper (0.339%Dmaxμm−1) and aluminum (0.116%Dmaxμm−1) foils. In the presence of a magnetic field the slope is lower (copper: 0.16%Dmaxμm−1, aluminum: 0.06%Dmaxμm−1). The effect of in-beam foils is reduced due to partial shielding of the surface from contaminant electrons. Copper causes a surface dose increase ≈3 times higher than aluminum of the same thickness, consistent with their relative electron density. Polyester film (127μm) increases the surface dose (to 35% Dmax with field) about as much as a gown (36% Dmax with field), while the increase with polyimide film (17μm) is less than 1% above the open field dose. Conclusions: Thin copper and aluminum conductors increase surface dose by an amount comparable to a hospital gown. Similarly, enclosure materials made of thin polyester or polyimide film increase surface dose by only a few %Dmax in excess of an unobstructed beam. Based on measurements in this study, in-beam, surface RF coils are feasible for MRIgRT systems.

Performance enhancement of the triboelectric energy harvester by forming rough surface polymer film using poly-dimethyl-siloxane +25 wt% water solution

In this paper, an experimental study of performance enhancement of the triboelectric energy harvester (TEH) by using rough surface poly-dimethyl-siloxane (PDMS) polymer film as one of the tribo layer has been presented. A parallel plate vertical-separation mode type TEH has been fabricated with rough surface morphology PDMS polymer film. Rough surface morphology is formed by spin coating diluted PDMS formed of Dow Corning 10:1 PDMS solution +25wt% water on the FR4 PCB board. FR4 substrate with single side copper clad has been utilised to realise bottom electrode. A cantilever structure is implemented utilising 50 μm thin copper foil, as top electrode, attached beneath a Kapton film. The device performance measurements showed the peak output voltage of 39.69 V and peak to peak voltage of 53.75 V. As a proof of concept, self-powered light emitting diodes (LED) system with 26 serially connected LEDs has been demonstrated with manual tapping on the TEH device.