Copper Microwires Research Articles

Giant magneto-impedance effect in amorphous CoP@Cu microstrip based device in a wide frequency range

The giant magneto-impedance effect (GMI) consists in a large variation in the electrical impedance that occurs in some magnetic materials when subjected to a variable external magnetic field. Here we present an experimental study of the GMI in a wide frequency range observed in a structure of the metallic amorphous magnetic alloy CoP electrodeposited on copper microwires by using a microstrip configuration. In the low frequency range, the magnetic field dependence of the impedance is due to the behavior of the circumferential ac susceptibility in the magnetic coating. In the microwave range the behavior of the GMI is dominated by the main dynamical magnetic phenomenon at high frequencies, namely ferromagnetic resonance (FMR). The experimental data are well fit by Kittel equation for the FMR frequency for a ferromagnetic layer with a saturation magnetization similar to the ones reported in previous works. The structural stability of the CoP alloy against aging effects was also investigated. The overall results indicate that the CoP alloy is a good candidate for applications in sensors and in microwave devices.

Design and fabrication of optically transparent transmitarrays using inkjet-printing technology

Abstract This paper explores the use of inkjet-printing technology for transparent transmitarrays, presenting a viable alternative to traditional copper microwire counterparts. The study focuses on achieving high-gain performance crucial for wireless communication systems, with a particular emphasis on the fifth-generation (5G) millimeter-wave communication. Transparent transmitarrays leverage transparent conducting films and conductive mesh structures, overcoming opacity limitations and seamlessly integrating with urban architecture. In this paper, the inkjet-printing process is detailed for fabricating transmitarray apertures, highlighting the flexibility and precision in depositing nanosilver particles onto a glass substrate. The design intricacies involve optimizing feeding characteristics, determining unit cell structures, and constructing transmitarrays of various sizes. To validate the proposed technique, three different apertures (15 × 15, 20 × 20, and 25 × 25 unit cells) are constructed. The antenna performances are evaluated in terms of reflection coefficients, radiation efficiency, realized gain, and patterns, demonstrating the effectiveness of inkjet-printed transmitarrays. Comparative analysis with copper microwire counterparts is also conducted, validating the inkjet-printing technology for similar gain performance with added advantages of flexibility, compatibility with transparent substrates, and cost-effective manufacturing.

Magnetoimpedance effect in NiFeP thin films deposited on Cu microwire through electrodeposition

Thin coatings of the Nickel–Iron–Phosphorous (NiFeP) alloy is electrodeposited onto copper microwire while varying phosphorus ion concentration in the bath. With increasing phosphorus ion concentration in the deposition bath up to 1 mM, reduced surface roughness, crystallite size and coercivity is witnessed which reflects in enhanced magnetoimpedance (MI) ratio of the plated wires. Maximum MI ratio of 378% and sensitivity of 25 %/Oe is observed at 100 kHz driving frequency for film deposited using 1 mM of P ion in the electrodeposition bath. This enhancement is associated with the reduction of crystallite size and magnetocrystalline anisotropy due to leading formation of amorphous deposits with the optimized incorporation of P atoms coupled with reduction of surface roughness. Additionally, the experimental results of MI measurements are compared with a analytical model and the model parameters related to the circumferential permeability of the NiFeP magnetic film is extracted from it. These parameters are further used to calculate the circumferential permeability of the samples, which is then mapped to a color-coded visualization of current density variation across the wire cross-section, providing a detailed insight into the impedance change.

Direct 3D microprinting of highly conductive gold structures via localized electrodeposition

Directly 3D-printed metal microstructures could enable hybrid micromanufacturing, combining conventional micromanufacturing with additive micromanufacturing (µAM). The microstructure’s material properties, including the electrical resistivity, are of decisive importance for a wide range of applications in microelectronics, high-frequency communication, and biomedical engineering. In this work, we present a room-temperature process for µAM of gold structures based on local electrodeposition. We demonstrate control of the electrodeposition process by regulating the precursor species supply rate through air pressure and by regulating the reaction rate through the electrodeposition potential. We 3D printed complex gold microscale structures and characterized the resistivity of the printed gold by developing hybrid devices with integrated four-point probe measurement capability. Additionally, we printed copper microwires, building on a previously shown copper µAM process, and characterized the copper resistivity. We demonstrate near-bulk resistivity values of 65 nΩ·m (about 2.5 times higher than bulk) and 19 nΩ·m (only 10% higher than bulk) for the gold and copper wires, respectively, without post-treatment. Microstructural analysis of the gold wires revealed a dense metal deposit free of voids. Finally, we printed gold structures on a pre-patterned substrate, paving the way to hybrid devices in which additive micromanufacturing is combined with existing micromanufacturing techniques.

Microstructure-driven electrical conductivity optimization in additively manufactured microscale copper interconnects.

As the microelectronics field pushes to increase device density through downscaling component dimensions, various novel micro- and nano-scale additive manufacturing technologies have emerged to expand the small scale design space. These techniques offer unprecedented freedom in designing 3D circuitry but have not yet delivered device-grade materials. To highlight the complex role of processing on the quality and microstructure of AM metals, we report the electrical properties of micrometer-scale copper interconnects fabricated by Fluid Force Microscopy (FluidFM) and Electrohydrodynamic-Redox Printing (EHD-RP). Using a thin film-based 4-terminal testing chip developed for the scope of this study, the electrical resistance of as-printed metals is directly related to print strategies and the specific morphological and microstructural features. Notably, the chip requires direct synthesis of conductive structures on an insulating substrate, which is shown for the first time in the case of FluidFM. Finally, we demonstrate the unique ability of EHD-RP to tune the materials resistivity by one order of magnitude solely through printing voltage. Through its novel electrical characterization approach, this study offers unique insight into the electrical properties of micro- and submicrometer-sized copper interconnects and steps towards a deeper understanding of micro AM metal properties for advanced electronics applications.

Incremental strain gradient plasticity model and torsion simulation of copper micro-wires

Experimental observations show that the torsional deformation of copper micro-wires exhibits obvious sample and grain size effects. In this work, based on the framework of the cyclic plastic J2 flow rule, an incremental higher-order strain gradient constitutive model is established to describe the size effect observed in the torsional deformation of copper micro-wires. A novel kinematic hardening evolution rule is constructed in which the coupling effect of sample and grain sizes on the plastic hardening has been considered. In terms of numerical implementation, a finite element iterative algorithm which can independently solve the gradient field and plastic strain increment is proposed. Finally, the proposed model is implemented into the finite element software ABAQUS using a three-dimensional user-defined element and user-defined material subroutine. Simulated results show that the proposed model can capture the size-dependent torsional deformation of copper micro-wires since both the effects of sample and grain sizes are considered reasonably. This provides a good basis for the combination of strain gradient plasticity theory and cyclic plasticity constitutive model.

Interconnecting embroidered hybrid conductive yarns by ultrasonic plastic welding for e-textiles

This article presents a novel approach for the electrical interconnection of embroidered conductive yarns with each other at defined cross-points using ultrasonic spot welding. The electrically conductive yarns are made of silver-coated copper microwires plied with polyester filament fibers into a hybrid embroidery yarn. In this study we evaluated the influence of different material properties (number of microwires of conductive yarn, fabric substrate, and adhesive film), the embroidery designs of contact pads, and the main parameters of the welding process (energy, force, amplitude, and tools) on the welded interconnection. The results were evaluated by the process yield and the contact resistance of the welded contacts. The electrical contacts were then tested for long-term reliability (elevated temperature and humidity, temperature shock change, bending, washing and drying) and analyzed. In addition, the contacts were examined with scanning electron microscopy (SEM) and micro-computed tomography and in the form of cross-sections with optical and SEM techniques to discuss interconnection and failure mechanisms. The results show that ultrasonic spot welding can enable the production of highly reliable interconnections of textile-integrated conductive yarns with contact resistances of a few milliohms that are resistant to mechanical, environmental, and washing conditions, leading to potential new manufacturing processes of e-textiles.

Facile and Efficient Negative Permittivity Realization of Copper Microwire Polymer Metacomposites at X-Band Frequency

Facile and Efficient Negative Permittivity Realization of Copper Microwire Polymer Metacomposites at X-Band Frequency

100 m Long Thermally Drawn Supercapacitor Fibers with Applications to 3D Printing and Textiles.

Supercapacitor fibers, with short charging times, long cycle lifespans, and high power densities, hold promise for powering flexible fabric-based electronics. To date, however, only short lengths of functioning fiber supercapacitors have been produced. The primary goal of this study is to introduce a supercapacitor fiber that addresses the remaining challenges of scalability, flexibility, cladding impermeability, and performance at length. This is achieved through a top-down fabrication method in which a macroscale preform is thermally drawn into a fully functional energy-storage fiber. The preform consists of five components: thermally reversible porous electrode and electrolyte gels; conductive polymer and copper microwire current collectors; and an encapsulating hermetic cladding. This process produces 100 m of continuous functional supercapacitor fiber, orders of magnitude longer than any previously reported. In addition to flexibility (5 mm radius of curvature), moisture resistance (100 washing cycles), and strength (68MPa), these fibers have an energy density of 306 μWh cm-2 at 3.0V and ≈100% capacitance retention over 13000 cycles at 1.6V. To demonstrate the utility of this fiber, it is machine-woven and used as filament for 3D printing.

Hi-Bi Photonic Crystal Fiber for Broadband Filter Realization Using Copper Microwires

This paper presents a highly birefringence (Hi-Bi) photonic crystal fiber (PCF)-based single-polarization filter, which consists of copper microwires. Copper is chemically stable and the use of microwires is benefit to fabricate than any metal-coated PCF. The filter characteristics are inspected by the full-vector finite element method (FEM). The proposed filter can filter out y-polarized mode, while the x-polarized mode can be guided. The confinement loss of the y-polarized mode at the wavelength of 1.31 μm is achieved of 696.79 dB/cm, while the x-polarized loss is only 4.34 dB/cm. According to numerical results, 20 dB bandwidth of the proposed filter with a maximum value of crosstalk of 601.37 dB is achieved of 650 nm that range from 1.1 to 1.75 μm. Furthermore, the insertion loss of the guided mode (x-polarization) is as low as 0.142 dB for 1 mm of fiber length. Moreover, by optimizing the structural parameters, it has shown that the proposed filter can be effective at any wavelength at the optical communication window.

Enhancing Piezoresistive Pressure Response Device Sensitivity by Orders of Magnitude

AbstractA bulk material electrode interfacing approach capable of enhancing the sensitivity of piezoresistive pressure sensors with magnitude orders is presented. Metal copper microwires are emplaced between the bulk conductive substrate and an electrode connecting it to the external circuit, replacing commonly used silver paste. These microwires create gaps on the interface between the two materials and increase the initial system resistance. As the applied pressure rises, the contact area between the substrate and microwires increases while the conductive substrate deforms, resulting in overall resistance reduction. With an appropriate setting of microwires, the sensitivity of the piezoresistive pressure sensor can be enhanced up to 106‐fold. The current design is widely adaptable toward different types of materials and allows a pressure operation of up to 931.2 kPa. The results indicate that rather than developing bulk materials, straightforward improvements in the device connecting interface can significantly enhance pressure response sensitivity with magnitude orders.

Simulation of Picking Up Metal Microcomponents Based on Electrochemistry.

The technology of picking up microcomponents plays a decisive role in the assembly of complex systems in micro- and nanoscale. The traditional method of picking up microcomponents with a mechanical manipulation tool can easily cause irreversible damage to the object, and only one object can be manipulated at a time. Furthermore, it is difficult to release the object with this method, and the release location is not accurate. With the aim of solving the above problems, the present study proposes an electrochemistry-based method for picking up metal microcomponents. First, the effect of ambient relative humidity on pickup was analyzed, and the effect of current density and electrolyte concentration on the deposition was examined. Then, a force analysis in the process of manipulation was carried out. Through the analysis of influence factors, the ideal experimental parameters were obtained theoretically. Finally, a simulation was carried out with COMSOL Multiphysics based on the above analysis. Copper microwires with a diameter of 60 μm and lengths of 300, 500, and 700 μm were successfully picked up and released using a pipette with a nozzle diameter of 15 μm. Compared with the traditional method, this method is simple to manipulate. Furthermore, it has a high success rate, causes less damage to the object, and good releasing accuracy.

Effects of fluorination of carbon film and annealing conditions on side leakage current and current breakdown time of SiO2/graphene/Cu/Ti/SiO2/Si specimens

Efforts are made to grow a few-layer graphene film over copper micro-interconnects to reduce the electrical resistance and improve the impediment of current breakdown. The annealing conditions for successful graphene growth and the effective method for the minimization of side leakage current between adjacent copper wires become the challenges for the targets. Copper micro-interconnects deposited on an Si wafer substrate with a SiO2 as the top dielectric layer are prepared using lithography with an ultrathin carbon film between the copper wire and SiO2 layer. The annealing conditions in the process of converting carbon into graphene are set with consideration of the preservation of copper wires and enhancement of the intensity of the Raman signal of graphene. Carbon films between adjacent copper microwires are converted into CFx by fluorination to impede side leakage current from the interconnects. A sufficiently low chamber vacuum pressure and large hydrogen flow rate can increase graphene intensity and thus impede the side leakage current effectively. Specimens with few-layer graphene have a higher voltage and a longer time needed for current breakdown. In tests without current breakdown, the thermal diffusion intensity of copper ions into SiO2 layer and the electrical resistance of the specimen with few-layer graphene are greatly reduced indeed.

Twin-core sunflower-type photonic quasicrystal fibers incorporated gold, silver, and copper microwire: an ultrashort and broad bandwidth polarization splitter

Polarization splitters are beneficial in the field of passive optical devices which are principally used in the coherent optical communication systems. An ideal polarization splitter must possess an efficient coupling with significant optical bandwidth. Hence, we proposed a novel metal-filled polarization splitter based on twin-core sunflower-type photonic quasicrystal fiber (PQF). The characteristics of the proposed splitter such as coupling length, extinction ratio, and available optical bandwidth were investigated by using the commercially available software, COMSOL Multiphysics. These aforementioned characteristics were determined by optimizing the geometrical parameters of proposed PQF—first by using gold-filled PQF (AuPQF). With optimized geometrical parameters, the splitter achieved an ultra-short coupling length of 132 µm and an ultra-broad bandwidth of 301 nm (wavelength range 1.36–1.68 µm) with an extinction ratio below than − 20 dB which comprised E + S+C + L+U band. Secondly, a comparative study to use silver- and copper-filled PQF (AgPQF and CuPQF) was explored. Both AgPQF and CuPQF retained a short length with adequate bandwidth and a significant extinction ratio below than − 20 dB. The AgPQF has a coupling length of 137 µm with a bandwidth of 136 nm which operated at 1.44 µm wavelength, while CuPQF with 134 µm lengths with a bandwidth of 149 nm and operated at 1.50 µm wavelengths.

Criteria for the process of drawing copper microwire for electronics

The paper provides information on the use of the developed mathematical model of repeated drawing with the sliding of a microwire from copper, intended for the installation of intracircuit electrical connections of microcircuits. Creation of a microwire based on copper for internal electric contact connections is a complex task: in the world practice, only a few firms can produce such a material that fully meets the requirements of the microelectronic industry. To obtain the specified microwire, it is necessary to work on the creation of high quality micro-alloyed copper; make a serious adjustment of the process of obtaining microwires, taking into account the complex of physical and chemical properties of the material. The article defines the criteria for the stability of the process of drawing during modelling, suitable for designing transitions of diamond dies. An analysis of the slip drawing process criteria, the safety factor of the drawing transitions, and the peripheral speeds of the pulls and wires to ensure the selection of both theoretically accepted and actually specified transitions of diamond dies is given. Based on a preliminary analysis of the model, recommendations are presented for its further improvement with the use of the criteria for the stability of the drawing process in order to increase the reliability of the process of obtaining a copper microwire for electronics.

Study of the Electrical and Diffusion Barrier Properties in Ultrathin Carbon Film-Coated Copper Microwires for Interconnects

Four specimen patterns with the microstructure of a microcopper wire are deposited on the Si-wafer substrate plus thermal oxide (SiO2) film as the top layer. Each pattern was prepared to have two kinds of specimens, including with and without ultrathin carbon film between the copper wire and the top layer (SiO2). The effect of carbon film on electrical properties is evaluated via the measurements of the I (current)–V (voltage) curve, sheet electrical resistance, current leakage, and its ratio and effective permittivity. A rapid thermal annealing (RTA) technique is provided as an economic and efficient method to grow the ultrathin carbon film rapidly as the interlayer. Appropriate choices of 900 °C and 3 min as the annealing temperature and time can produce ultrathin carbon film with nearly 100% coverage of the copper surface. The sheet resistance of specimen demonstrates the behavior exactly opposite to that of the carbon film coverage of wire surface. The combined effect of elevating the voltage and annealing temperature of the specimen with carbon film on the current leakage is much lower than that arising in the specimen without carbon film, so long as the carbon films operating at that temperature (between 350 and 500 °C) are still sustainable. The differences in current leakage and effective permittivity between these two kinds of specimen are significantly increased by raising the temperature. The intensity (IC) of copper diffusions into the SiO2 layer in the specimens with the carbon film demonstrates behavior similar to that of current leakage (CL). The IC and CL values for the temperatures ≦ 350 °C are much lower than those obtained at 500 °C.

Scale effect investigation of copper microwire's mechanical properties after in situ scanning electron microscope twisting

In this study, the mechanical property of copper microwire, a widely used material in our daily life, is investigated by subjecting it to in situ scanning electron microscope twisting based on a self-developed nanorobotic manipulation system. First, copper microwire is assembled on the nanorobotic system inside the scanning electron microscope, and then twisted clockwise and anticlockwise continuously from 0° to 360° until fracture. After that, the mechanical properties of elastic modulus, microhardness, yield stress, and the strain hardening exponent of the twisted sample are investigated by nanoindentation. The change in elastic modulus and indention hardness showed strong indentation size effects, because a large number of geometrically necessary dislocations were generated around the indenter. In addition, the fracture analysis indicated that the smaller the scale of the material, the more sensitive it was to surface cracks or defects. Ductile fracture features of the twisted sample appear due to the nucleation, growth, and coalescence of the microvoids.

On-line coupling of millimeter size motors and chronoamperometry for real time bio-sensing of branched-chain amino acids in maple syrup urine disease clinical samples

Here, the on-line coupling of millimeter size motors (m-motors) and chronoamperometry for real time bio-sensing of branched-chain amino acids (l-b-AAs) in maple syrup urine disease (MSUD) clinical samples is proposed. Marangoni effect for controlled mixing and delivery of active enzyme for substrate digestion and subsequent electrochemical sensing is conveniently explored. To this end, an integrated cell device, which includes reservoirs for motors movement and electrochemical detection, was fabricated. l-amino acid oxidase (LAO)-loaded m-motors just by capillarity without any coating chemistry are used for the enantiomers selective recognition, and then the hydrogen peroxide released from enzymatic reaction is electrochemically monitored at −0.20 V using copper microwires as exclusive transducers. The inherent enzyme m-motor features – “self-micro mixing” and the continuous release of fresh and free enzyme-, not only avoided the use of external stirring or the enzymatic physical adsorption or chemical bonding to the electrode; but a dramatic decreasing of analysis times (just 200 s vs. 25 min without motors, yielding only a 70% of the m-motor signal). In addition, an excellent accuracy (Er < 6%) for l-b-AAs determination in clinical samples from patients previously diagnosed by a reference center was also obtained. We envision future opportunities for this approach to be a potential point of care (POC) testing device, because of its rapid response, simplicity, selectivity and sensitivity; becoming into another step facing towards the challenges of rare disease diagnostics.

Microfabrication of conductive copper patterns by meniscus-confined electrodeposition

ABSTRACTComplex three-dimensional copper (Cu) wires have been successfully fabricated by meniscus-confined electrodeposition (MCED) controlled by quasi-static stability of the meniscus. Here, we report a new dynamic meniscus stability based MCED process. The obtained copper microwires are straight, uniform in width and have a smooth surface (surface finish of 8.79 nm (Ra)). When current density higher than 31.81 mA/cm2, dense Cu microstructure is deposited on the cathode substrate, while current density between 12.13 mA/cm2 and 31.81 mA/cm2, sparsity structure was observed on the surface of the copper wire. This work provides a direct method to fabricate Cu microwires on conductive substrates without the use of additives.

The effect of surfactant on the structure, composition and magnetic properties of electrodeposited CoNiFe /Cu microwire

In this work, the constant current electrodeposition of a ternary CoNiFe alloy onto a copper microwire from borate baths containing three surfactant additives was compared. The additives were sodium dodecyl sulfate (SDS) as an anionic surfactant, Triton X-100 as a nonionic surfactant, and the ionic liquid (IL) 1-dodecyl-3-methylimidazolium chloride) [C12mim]Cl(as a cationic surfactant. The scanning electron microscopy of the film surfaces showed that the coatings are compact and crack-free, but morphological differences were observed. The films prepared in the IL under optimized experimental conditions showed mechanical stability, high saturation magnetization (79 emu/g), and a GMI ratio of 183.4% at 1.5 MHz, which make them promising candidates for soft magnetic applications. The effect of current density, pH, IL concentration, and metal ion concentration on the current efficiency and the alloy composition was systematically investigated. Anomalous co-deposition under a current density of 29 mA/cm2 and pH of 2.5 in the presence of 1.2 g/L IL for a deposition time of 120 min lead to 30 μm thick Co17Ni53Fe30 alloy coatings with a nanocrystalline/amorphous structure.