Copper Circuit Research Articles

Design of wireless charging system for E-Vehicle

To address the dual problems of fuel reliance and air pollution, this study describes the design of a wireless ground to vehicle charging system powered by solar energy and specifically designed for electric vehicle (EV) charging stations. As the number of electric vehicles on the road steadily rises, they present a viable way to cut travel expenses by switching from conventional fuel to electricity, which is a more economical and sustainable option. With the introduction of a wireless EV charging system, this creative solution does away with the need for external power sources and permits continuous charging without interfering with driving. Utilizing solar power, the charging system incorporates solar panels, batteries, circuit regulators, boost converters, receiver and transmitter copper coils, AC/DC converters, microcontrollers (such as ATmega), LCD screens, and circuit regulators. This study describes a technique that shows that charging electric cars while driving is feasible and eliminates the need to stop. This technology for wireless solar electric vehicle charging presents a forward-thinking approach to sustainable mobility by providing a workable solution that can be easily included in the road infrastructure. For the wireless charging, in addition, various coil designs are suggested.

Printable and filament-drawable PDMS based adhesive assisted manufacturing of highly conductive copper micro-patterns

Manufacturing of copper micro-patterns is crucial in electronics for its utilization as high conductivity transparent conductive films (TCFs) and circuits. In the preparation process of current TCFs, a plethora of materials have emerged that can replace traditional indium tin oxide (ITO). However, even for the most promising metal-based nanowire materials, there are issues such as high cost, complex welding, and high contact resistance. To address these problems, this paper proposes a printable and filament-drawable polydimethylsiloxane (PDMS)-based adhesive, which, through a novel additive patterning technology, efficiently and economically manufactures self-welding copper micro-meshes and circuits. The adhesive can be processed into micro-patterns through printing and filament drawing, on which ionic Ag can be in situ reduced and anchored, thereby eliminating the need for tedious pre- and post-treatment steps. The fully exposed Ag particles dramatically minimize the usage of precious metal catalyst, thus efficiently catalyzing electroless copper deposition (ECD) reaction. Highly conductive (1.03 × 107 S m−1) copper circuits can be fabricated on the printed adhesive patterns, exhibiting versatile applicability to diverse substrates. Highly precise copper micro-meshes (∼50 μm) can be fabricated on the filament networks drawn by the adhesive. The copper meshes undergo complete self-welding at junctions during the ECD process, thus exhibiting ultra-low square resistance of 0.45 Ω sq−1 while maintaining a high transmittance of 82.2 %. This is far superior to most of TCFs in published literature.

Hybrid additive-subtractive manufacturing of high-density copper-based flexible transparent circuits based on side-etch process

High-density flexible transparent circuits (FTCs) are widely used in 5G/6G flexible transparent antennas, wearable devices, flexible transparent electronics and other fields. However, the rapid iteration and upgrading of electronic circuits present significant challenges to the manufacturing of both high-density and high-precision circuits (especially copper-based circuits) at room temperature, in an efficient and flexible manner. Here, we employ the side-etching phenomenon, which is typically avoided, to propose a novel method for hybrid additive-subtractive fabricating high-density copper-based FTCs that combines electric field-driven (EFD) microjet printing and wet etching technology. Firstly, the customized photoresist mask was flexibly printed on the copper-clad flexible substrate by EFD microjet printing, and then the copper circuit with less than the mask resolution was obtained by the side etching process of the wet etching process. By optimizing process parameters and precisely controlling the speed of the side etching stage during the etching process, the manufacturing of high-precision copper-based FTCs with a minimum line width of 2.4 μm and a minimum pitch of 4 μm was achieved. The typical sample is manufactured with a resistivity of 4 × 10−6 Ω·cm, a sheet resistance of 3.58 Ω/sq at a transmittance of up to 87.65 % (including the substrate), and it exhibits excellent mechanical stability. The prepared high-density flexible transparent interdigital electrode has excellent sensitivity, and can detect the concentration change of dilute H2SO4 solution at a minimum of 1 nmol/L at a frequency of 100–10,000 Hz. This method provides a new solution for the fabrication of copper-based FTCs at room temperature with high efficiency and low cost, and shows a good prospect for industrial application.

Designed wrinkles for optical encryption and flexible integrated circuit carrier board

Patterns on polymers usually have different mechanical properties as those of the substrates, causing deformation or distortion and even detachment of the patterns from the polymer substrates. Herein, we present a wrinkling strategy, which utilizes photolithography to define the area of stress distribution by light-induced physical crosslinking of polymers and controls diffusion of residual solvent to redistribute the stress and then offers the same material for patterns as substrate by thermal polymerization, providing uniform wrinkles without worrying about force relaxation. The strategy allows the recording and hiding of up to eight switchable images in one place that can be read by the naked eye without crosstalk, applying the wrinkled polymer for optical anti-counterfeiting. The wrinkled polyimide film was also utilized to act as a substrate for the creation of fine copper circuit by a full-additive process. It generates flexible integrated circuit (IC) carrier board with copper wire density of 400% higher than that of the state-of-the-art in industry while fulfilling the standards for industrialization.

The interaction between Aspergillus brasiliensis and exposed copper circuits in the space microgravity environment

In the space station, filamentous fungi are one of the main potential hazards causing short circuits or corrosion failure of printed circuit boards (PCBs). A 90-day fungal corrosion test was carried out on the China Space Station (CSS), focusing on the interaction between A. brasiliensis and exposed copper circuits. The results showed that the mycelial morphology, ultrastructure, and organic acid accumulation of the test fungi exhibited significant changes in the space microgravity environment. Aspergillus brasiliensis tended to excrete higher levels of oxalic acid in space as a defense mechanism against copper toxicity, which could exacerbate localized corrosion of copper metal.

Blended Copper and Nano-Silver Screen-Printed Circuits on FTO-Coated Glass

Using a mixture of micro-copper and nano-silver in the production of screen-printed circuits has the potential to reduce material costs and cost variability. The fundamental premise of this study involved dispersing silver nanoparticles among the larger copper microparticles at selected ratios and subsequently sintering in order to establish their resultant electrical and physical performance. Commercial materials were mixed, printed, and sintered at two thermal regimes on fluorine-doped tin oxide (FTO)-coated glass substrate. The inclusion of 25% silver provided an appreciable reduction in electrical resistance from 4.21 Ω to 0.93 Ω, with further silver additions having less impact. The thermal regime used for sintering had a secondary impact on the final electrical performance. The addition of silver reduced the adhesion to the FTO substrate, with reduced film integrity. The results show that blending inks offers the advantage of enhancing material conductivity while simultaneously reducing costs, making it a compelling area for exploration and advancement in the field of electronics manufacturing.

Simultaneous Scanning Ion Conductance and Electrochemical Microscopy in Lithium‐Ion Battery Research

AbstractDeeper understanding of processes involved in operation of lithium‐ion batteries (LIBs) is necessary to further optimize them for future applications. Extensive research was conducted on the formation of a solid electrolyte interphase (SEI) on negative battery electrodes, still leaving several questions unanswered. Scanning probe microscopies (SPMs) enable in situ and operando investigations and have the potential to explain some phenomena. Scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM) could be employed in LIB studies. A novel SICM method based on the redox couple ferrocene/ferrocenium is introduced for applications in carbonate solvents widely used in LIBs. Proof of concept measurements were conducted with a micro milled copper circuit board as model substrate. Furthermore, the proposed SICM approach was hyphenated with feedback mode SECM resulting in the simultaneous mapping of morphology and electrochemical activity. A flexible dual‐probe arrangement was developed enabling usage of both SPM techniques at the same time, and furthermore, an easy replacement of both individual probes if needed. The setup was applied in the characterisation of commercial graphite electrodes for LIBs before and after conducting a pre‐charging protocol. Changes in electrochemical activity and topography of the graphite electrode were resolved in simultaneously generated SECM/SICM recordings.

Environmentally-Friendly Electroplating Process Using Solid Electrolyte Membranes

The automobile is a very broad industry, and consists of tens of thousands of parts. Many parts of automobile employ surface treatment to provide several functions such as electronic and anti-corrosion properties. Among several surface treatment process, plating is an important elemental technology for automobile industry. For the industrial perspective, interest in SDGs significantly increases, and efforts to reduce environmental impact are highly urgent. Recently, we have developed novel electroplating process, solid electrodeposition (SED), which is based on ion transfer through solid electrolyte membrane1). This process has unique deposition characteristics that the metal film can be deposited only on the contact area between cathode and the membrane, in a fashion similar to stamping deposition. The SED process has an advantage for reducing amounts of waste effluent and CO2 gas. Moreover, this process has a potential of high deposition rate due to utilization of thin electrolyte membrane, providing lower electrical resistance between electrodes1), 2). Therefore, in the environmental and economical perspective, we believe that SED is promising process to metallize the substrate surface as an alternative to the conventional electroplating, especially in the field of electronics manufacturing. In this study, we report on SED system in details and characterization of deposited copper and nickel films. We also introduce copper fine patterning technique combined with SED using hard mask. Figure 1 shows schematic of the present SED system. The head part composed of anode plate, electrolyte solution and membrane are placed on substrate under controlled temperature and pressure. The membrane mainly plays a role of selective cation transfer from electrolyte solution to the substrate, although a small amounts of electrolyte solution can also be transferred due to pressure difference between internal head part and atmosphere. This solution uniformly spread to the interface between membrane and substrate so that uniform metal deposition is continuously proceeded without adhering the membrane with the substrate. Additionally, the SED system allows one to shorten the distance between electrodes because membrane can act as a diaphragm. Therefore, the power consumption is smaller than that of conventional electroplating, owing to decrease in an internal electrical resistance, providing the decrease of exhaust CO2 gas. The deposited film has relatively uniform thickness as shown in Figure 2, the result of which is due to the short distance between electrodes as well as uniform current feeding to deposit metal films through the back side of the cathode. The deposited copper and nickel films are crystalline and highly conductive, the quality of which are being enough for application of the SED process in the current electronics device manufacturing. By combining the SED process with the conventional screen printing technique, copper circuit patterns with line width of below 50 μm could also be successfully fabricated.1) Akamatsu, S. Nakano, K. Kimura, Y Takashima, T. Tsuruoka, H. Nawafune, Y. Sato, J. Murai, H. Yanagimoto, ACS Appl. Mater. Interfaces, 13, 13896-13906 (2021)2) Narui, Y. Hoshi, I. Shitanda, M. Itagaki, H. Yanagimoto, M. Hiraoka and H. Iisaka, E01-920, 232nd ECS Meeting. Figure 1

High Performance SiC Power Module Based on Repackaging of Discrete SiC Devices

Increased adoption of electric vehicles (EV), photovoltaic (PV), and battery energy storage systems (BESS) is driving the need for high-current SiC power modules. The state-of-the-art multichip module is substantially more expensive than the IGBT module. This paper proposes a cost-effective packaging methodology for high-power SiC intelligent power modules (IPMs) with discrete SiC devices. The proposed IPM integrates the gate drivers, decoupling capacitors, snubbers, discrete SiC devices, direct bond copper (DBC), base plate, temperature sensors, and overcurrent protection circuits, achieving very low loop inductance and thermal resistance, and more than 50% cost reduction. A 1200V/480A/2.15mΩ half-bridge IPM is presented for comparison with commercial counterparts. A 1200V/240A/4.3mΩ six-phase IPM is developed, and its performance is experimentally verified.

Fabrication of high-performance copper circuits using laser-induced forward transfer with large receiving gaps based on beam modulation technology

Laser-induced forward transfer (LIFT) technology has been widely used to print 2D/3D structural patterns in the micron level of metals due to its contactless and maskless advantages. Still, it cannot meet the practical needs of the industry due to its drawbacks, such as low efficiency and a small receiving gap. This study proposes a new LIFT by modulating a Gaussian beam into an Arc beam using a liquid crystal on silicon spatial light modulator (LCOS-SLM) to achieve stable preparation of high-performance Cu circuits at large receiving gaps. First, the laser-induced monomer transfer modes of Gaussian beams and arc beams are studied. Then the effects of laser energy density, scanning velocity, and reception gap on the microcircuits prepared by Gaussian beam laser-induced forward transfer (GB-LIFT) and Arc beam laser-induced forward transfer (AB-LIFT) are studied systematically, and suitable process parameters are found. The transfer process of action of AB-LIFT is revealed. Under the optimized process parameters, the flight distance of AB-LIFT is up to 120 μm, which is about twice that of GB-LIFT, when the laser energy density is 1.94 μJ, and the scanning velocity is 3 mm/s. And the height of the microcircuit can be controlled by the number of depositions. It is demonstrated that the AB-LIFT can achieve stable transfer with large receiving gaps and efficiently prepare continuous Cu circuits with high bonding strength and low resistance. The minimum resistivity (7.46 μΩ∙cm) obtained by selecting optimized process parameters is about 4 times that of Cu bulk (1.76 μΩ∙cm). The application of the AB-LIFT method based on the beam modulation technique in microcircuit defect repair is verified.

Development of a Novel Tape-Casting Multi-Slurry 3D Printing Technology to Fabricate the Ceramic/Metal Part.

Printing ceramic/metal parts increases the number of applications in additive manufacturing technology, but printing different materials on the same object with different mechanical properties will increase the difficulty of printing. Multi-material additive manufacturing technology is a solution. This study develops a novel tape-casting 3D printing technology that uses bottom-up photopolymerization to fabricate the green body for low-temperature co-fired ceramics (LTCC) that consist of ceramic and copper. The composition of ceramic and copper slurries is optimized to allow printing without delamination and sintering without cracks. Unlike traditional tape-casting processing, the proposed method deposits two slurries on demand on a transparent film, scrapes it flat, then photopolymerization is induced using a liquid crystal displayer to project the layer pattern beneath the film. The experimental results show that both slurries have good bonding strength, with a weight ratio of powder to resin of 70:30, and print a U-shaped copper volume as a circuit within the LTCC green body. A three-stage sintering parameter is derived using thermogravimetric analysis to ensure good mechanical properties for the sintered part. The SEM images show that the ceramic/copper interface of the LTCC sintered part is well-bonded. The average hardness and flexural strength of the sintered ceramic are 537.1 HV and 126.61 MPa, respectively. Volume shrinkage for the LTCC slurry is 67.97%, which is comparable to the value for a copper slurry of 68.85%. The electrical resistance of the printed copper circuit is 0.175 Ω, which is slightly greater than the theoretical value, hence it has good electrical conductivity. The proposed tape-casting 3D printer is used to print an LTCC benchmark. The sintered benchmark part is validated for the application in the LTCC application.

Benzaldehyde derivatives on tin electroplating as corrosion resistance for fabricating copper circuit

Abstract Electrodeposited tin is a crucial corrosion-resistant metal to protect electronic interconnection and copper circuits in the manufacturing process of electronic products. The corrosion-resistant properties of electrodeposited tin can be improved with the addition of additives in electrodeposition. Three benzaldehyde derivatives including vanillin, ethyl vanillin, and veratraldehyde as brighteners were investigated for tin electrodeposition. Computational and experimental analyses were conducted to investigate the relationship between coating properties and the chemical factors including the molecular structure, adsorption process, and electrochemical behavior of the brighteners. The computational work demonstrated that all three brighteners could hold high reactivity and spontaneously absorb on the tin surface. The results of linear sweep voltammetry tests (LSV) illustrated that all three brighteners effectively increased the cathode polarization but ethyl vanillin exhibited the best inhibiting performance in the tin deposition. Besides, the adsorption behavior of brighteners on the tin layer also affected the grain morphology and preferred growth orientation of the crystal surface. The corrosion rate and side erosion results both indicated that ethyl vanillin could benefit to form a tin coating with good corrosion performance to meet the requirement of copper circuit fabrication of printed circuit board.

The need for design-for-recycling of paper-based printed electronics – a prospective comparison with printed circuit boards

The present study compares conventional printed circuit boards (having glass-fibre and epoxy substrates and etched copper circuits) with paper-based printed electronics (offering flexible, bio-based, and biodegradable substrates with circuit design printed using silver-based inks) and assesses the relevance of e-waste recycling to the latter's sustainability. Therefore, a comparative life cycle assessment between these two options has been undertaken and the global warming impacts were calculated.The impact assessment results underscore that printed electronics offer a consistent sustainability advantage over printed circuit boards only through recycling of silver in the former at the end-of-life. Hence, design-for-recycling and recycling as e-waste are crucial to the sustainability of the current generation of printed electronics. Other foreseen waste treatment options for paper-based printed electronics, such as composting, and paper recycling, are likely to limit the sustainability advantage of printed electronics to circuits with small conductive areas.

Cu Deposition on AAO Substrate for Interposer Applications

In recent days, the demand for high-performance devices has increased in the semiconductor industry. These devices require integrated circuits to test out their performance. For this purpose, interposer with both vertical and horizontal copper circuits which offers advanced connections is used. Interposer consists of a substrate material and metal circuits. Common substrate materials for the interposer are silicon and glass. Whereas anodized aluminum oxide (AAO) has less current leakage than silicon substrate, which results in no need for the insulation, and has a vertically self-aligned nanopore structure though wet etching process, which enables high density holes with less cost. AAO was proposed as a substrate material for interposer.AAO substrate was fabricated using 0.3M oxalic acid solution, followed by fabricating through-hole of AAO. For the interconnection, copper layer was deposited on the surface and hole of AAO substrate by electroless and electrochemical techniques sequentially. Sol-gel catalyst was adopted followed by heat treatment, instead of Sn/Pd catalyzation, to increase the adhesion property and breakdown voltage. Fabricated AAO is a circle shape with 4.8 cm diameter and average pore size is about 98 nm. Cu electroless deposition was performed on AAO with and without through-holes. Thin Cu layer was deposited without voids. The adhesion was measured by SCRATCH TESTER PRO, J&L Tech, Korea, showing first crack around 1.5 N to 2 N. Pulse electrodeposition with surfactant was used to fill the trough-hole of AAO substrate for through-AAO interconnects. The more details will be presented. Figure 1

Value addition of copper sulphide from nickel refining: Process modelling and simulation

The aim of the study was to develop a process option for the value addition of a leach residue from hydrometallurgical nickel refining. The residue in question is copper-rich (58 %) with sulphur (23 %), nickel (3 %) and iron (2 %) as the other main constituents. The prevailing phases are covellite and antlerite and the residue is already a marketable product as such. The current study suggests a flow sheet with moderate temperature autogenous pressure leach, selenium removal and copper electrowinning. Precious and platinum group metals will enrich the solid phase. Further solution purification is to be considered if London Metal Exchange grade copper is desired. The process was modelled in a steady-state and a proposal was made for integration into nickel refining. The bleed requirement from the developed copper circuit was 51 % of the spent electrolyte, which may be treated and utilised in the preceding nickel refining. In addition, sensitivity analysis was conducted to obtain data for adapting the copper circuit to suit nickel refining and navigate the way forward in the development project. The process simulation showed that the copper circuit, in the case of pressure leaching, would produce more than 300 kg of acid per tonne of feed, which would need to be bled out.

Electroless plating of a 5G copper antenna on polyimide patterned with laser-induced selective activation and curing of metal–organic catalyst

An improved electroless copper plating method for fabricating 5G/Sub-6 GHz antennas is reported. A catalyst, palladium ion/4-vinylpyridine (Pd2+/4VP) complex, which not only initiated electroless copper plating but also promoted the adhesion of the copper layer, was dip-coated onto a polyimide (PI) substrate. Selective curing and activation of the Pd2+/4VP complex catalyst were induced by a pulsed UV laser. Wherever the laser scanned on the PI substrate, the palladium ions were reduced to palladium atoms, and the free radicals created from the decomposition of tert-butyl peroxybenzoate (TBPB) initiated the copolymerization of 4VP and PI, which enhanced the adhesion of the catalyst on the substrate. The unreacted Pd2+/4VP was removed by ethanol and collected for reuse, hence a much-reduced material cost. By adjusting the laser power, scanning speed, defocusing distance, and electroless plating time, the optimized process condition for Cu circuit fabrication without damaging the PI substrate was found. A high-quality copper circuit pattern was achieved with a laser power of 100 mW, a scanning speed of 330 mm/s, a defocusing distance of 2.0 mm, and an electroless plating time of 40 min. The copper patterns exhibited excellent adhesion and maintained good conductance after the bending fatigue tests. This laser treatment approach is simple, cost-effective, and applicable to non-planar 3D substrates, and the usefulness of this method was demonstrated by fabricating a 5G/Sub-6 GHz antenna with good device performances.

Scalable Strategy to Directly Prepare 2D and 3D Liquid Metal Circuits Based on Laser-Induced Selective Metallization.

Selective wetting of a gallium-based liquid metal on copper circuits is one of the ways to prepare liquid metal circuits. However, the complex fabrication processes of an adhesion layer between copper circuits (or patterns) and substrates were still inevitable, limiting scalable applications. Our work developed a facile way to directly prepare 2D and 3D liquid metal circuits by combining laser-induced selective metallization and selective wetting for the first time. The copper template was obtained on elastomers using laser-induced selective metallization, and high-resolution liquid metal circuits were fabricated by brushing Galinstan on the copper template in the alkali solution. The distribution of Cu element not only was on the top surface but also extended to the interior of the elastomer substrate. This revealed that the Cu layer prepared by laser-induced selective metallization is born to firmly embed into the substrate, which endowed the circuits with strong adhesion, reaching the highest 5B level. Moreover, the prepared liquid metal circuits (or patterns) had a typical layered structure. The liquid metal circuits exhibit good flexibility, stretchability, self-healing ability, and acid-alkaline resistance. Compared with the traditional methods of patterning liquid metals, fabricating liquid metal circuits based on laser-induced selective metallization has irreplaceable advantages, such as strong adhesion between circuits and substrate, fabricating 3D circuits, good acid-alkaline resistance, cost-effectiveness, maskless use, time savings, arbitrary design of patterns, and convenient operation, which endow this method with great application prospect.

Oxidation-reduction effects in the flotation of copper sulfide minerals and molybdenite – A proof of concept at industrial scale

Redox potential (Eh) control plays a significant role during sulfide mineral flotation by influencing the reactions on the surface of the minerals and accordingly the flotation behaviour. In this study, the metallurgical performance of typical copper sulfide minerals, molybdenite as well as gangue minerals (e.g., pyrite, tennantite, and enargite) under different pH and Eh conditions of the flotation cell were investigated. The copper and molybdenum processing plant at the Sungun complex-Iran were selected as a case study. For this purpose, Eh of flotation cells of phases 1 and 2 of copper and molybdenum processing circuits – Sungun complex – were measured by off-line method. After performing chemical analysis, the mineralogical study of the input load and products of each of the aforementioned flotation circuits in the rougher, cleaner, re-cleaner, and scavenger stages was performed. Based on the results, the potential in cells of phases 1 and 2 of copper concentration plants is in the range of −60 to −100 mV; and for the molybdenum plant, is in the range of −500 to −700 mV. The potentials of more than −100 mV in the phases of copper concentration plants have created suitable conditions for the separation of copper sulfide and molybdenite minerals from gangue minerals, especially pyrite. Adjustment of Eh in the range of −500 to −700 mV in the molybdenum processing plant has also led to the depression of copper minerals and the flotation of molybdenite, resulting in the effective separation of these minerals. However, grade analysis and mineralogical studies indicate the misplaced copper minerals into tailings, the passage of chalcopyrite and pyrite to molybdenum concentrate, the misplaced molybdenite to copper concentrate, and also the presence of minerals containing harmful elements such as arsenic in copper concentrate. Eh fluctuations in phase 1 and 2 of copper plants, the interaction of copper sulfide minerals, especially chalcopyrite with pyrite (and the depression of pyrite in Eh more than −100 mV), are reasons for the misplaced copper minerals into tailings. The interaction of chalcopyrite and pyrite with molybdenite and the high flotation tendency of molybdenite at the potential of +600 mV is the main factor in increasing the Cu and Fe grade in molybdenite concentrate. The interaction of copper minerals with arsenic-bearing minerals and the similar flotation behavior of these minerals in the potential of the rougher cells of the molybdenum processing plant has increased the arsenic grade in the copper concentrate or molybdenum tailings.

Thermal and dielectric properties enhancement of photocurable acrylate polymers for digital light processing 3D printed electronics

AbstractDigital light processing 3D printing has been rapidly evolving conventional manufacturing industry with the most meticulous resolution and strongest layer‐to‐layer adhesion among all additive manufacturing techniques. In this study, to improve poor polymer thermal stability and dielectric properties from prevailing methyl methacrylate‐based resin, tri‐functional trimethylolpropane tri‐acrylate (TMPTA) is introduced to form a stable polymer network. Meanwhile, monomers carrying non‐polar, bulky adamantane are added to eradicate poly‐TMPTA's notorious high cracking and warping tendency. Test results showed both high 1‐adamantyl methacrylate and 1, 3‐adamantyl di‐acrylate (ADDA) additions can print crack‐free samples. However, only ADDA addition keeps low CTE (82.86 ppm/oC, 200 ~ 260°C) and cuts down Df (0.02, 10 GHz). TMPTA polymer network modifications of both additions are explored. By contrast, poly‐MMA exhibits much higher CTE (323.44 ppm/oC) and Df (0.035). A 3D‐printed curvilinear circuit board from above resin formulation with electroplated copper circuits successfully passes lead‐free level reflow without deformation.

A flow-rate-controlled double-nozzles approach for electrochemical additive manufacturing

ABSTRACT The electrochemical additive manufacturing technique based on the meniscus-confined approach has been proved to be a powerful tool for fabricating nanoscale and microscale metal components. The stability of the meniscus is the key in this meniscus-confined approach to achieve high resolution and reliable product quality. In the present study, a double-nozzles design, which consists of a feed nozzle and a suction nozzle, is proposed for the meniscus confined electrochemical additive manufacturing technique. It was demonstrated that the proposed design possessed robust control of the stability of the meniscus by manipulating the feed and suction rates of the two nozzles in a quite large range. Various sizes of menisci can be easily obtained by utilising nozzles with different sizes. Compared with the pressure-controlled single-nozzle approach, the results showed that dense structures without dendrites can be fabricated by the double-nozzles design with larger current density due to the feed-and-suction process at the tip of the nozzles. The proposed flow-rate-controlled double-nozzles design was finally employed to fabricate some copper circuits and a Cu/CuNi thin film thermocouple to demonstrate its potential in fabricating electronic devices.