Scalable Manufacturing of Multi-Stacked Copper Spiral Inductors Using a Novel Fully Additive Method

This study reports, for the first time, the fully additive fabrication of miniaturized, embedded triple-stacked copper spiral inductors—an unprecedented achievement in multilayer inductor manufacturing. Using our novel Sequential Build-Up–Covalent Bonded Metallization (SBU–CBM) method, we demonstrate a etch-free, room-temperature process capable of producing complex 3D inductor architectures with sub-10 μm features and high vertical integration. Unlike conventional additive, subtractive or hybrid subtractive–additive techniques, the SBU–CBM method enables high-resolution laser-defined patterning, selective electroless copper deposition, and accurate optical alignment—completely eliminating the need for vacuum systems, chemical etching, or thermal sintering. The successful fabrication of three vertically interconnected spiral inductors through 10 μm copper microvias confirms the method’s unmatched capability in fabricating intricate multilayer geometries through a fully additive process. Optical microscopy and X-ray Computed Tomography (XCT) imaging validate the structural integrity, precise interlayer alignment, and continuous electrical connectivity across all layers. Critically, the method achieves uniform miniaturized copper strip widths of 10 μm, underscoring its strength in high-density packaging and next-generation integrated systems. This breakthrough establishes SBU–CBM as a transformative approach for realizing compact, high-performance, and scalable 3D embedded components in future electronic applications.

The specimen surfaces bombarded with Ar+ ions prepared from OFHC, Nb base super-conducting alloy ingots and multi-layered magnetic alloys plated on thin wire of Cu-3wt % Ag alloy were observed mainly with optical and electron microscopes, interference microscope and differential interference microscope to discuss the distinction between chemical and ion etchings. The results of experiments were as follows: (1) In both of chemical and ion etchings of OFHC specimen, a clear step was observed between two neighboring crystal grains having different crystal orientations. In the chemical etching, no change was seen in the height of step with the lapse of time. (2) In the chemical etching, marks of slip lines, having been produced by plastic deformation, were too indistinct to be observed. While, in the ion etching the marks, having be lessened by electropolishing, reappeared. (3) Typical nodular structures were observed by chemical etching of Nb-base super-conducting alloy ingots. While, the nodular structures disappeared by ion etching, showing preferential removing of Zr and Ti from the alloy. (4) The multi-layered structure, mainly consisting of magnetic alloys, could not be clearly observed by the conventional chemical etching; but, it could be clearly observed by application of the ion etching.

Improvement of the mechanical strength of Si structures by applying chemical wet etching was investigated. The cantilever specimens that have a sidewall surface of Si{110} were produced by a Bosch process with a resist mask. The typical height and pitch of the scalloping formed on the sidewall were 245 and 891 nm, respectively. To improve mechanical strength of the cantilever, 50 % KOH (40 °C) chemical wet etching was applied to reduce the scalloping. The cantilevers with and without chemical etching applied were bent laterally by using a manipulator under an optical microscope. The maximum stresses in the cantilever at the fracture were increased by applying chemical etching. The increment ratio of the stress in Si{110} specimens was 1.7–1.8 times. Cantilevers with and without chemical etching applied showed no big differences in terms of the fracture configurations.

Additive Manufacturing (AM) often produces complex engineered structures by precisely distributing materials in a layer-by-layer fashion. Multimaterial AM is a particularly flexible technique able to combine a range of hard and soft materials to produce designed composites. Critically, the design of AM multimaterial structures requires the development of precise three-dimensional (3D) computed aided design (CAD) files. While such digital design is heavily used, techniques able to validate the physically manufactured composite against the digital design from which it is generated are lacking for AM, especially as any evaluations must be able to distinguish material variation across the 3D space. Nowadays, there is a growing interest in volumetric tools that can provide topological information hidden by the surface of shaped materials. So far, technologies such as Optical microscopy (OM), Scanning Electron Microscopy (SEM), and Coordinate Measuring Machine (CMM) have paved the way into the metrology field to measure the external geometry of physical objects. Currently, alongside conventional metrology tools, X-ray computed tomography (XCT) is emerging to measure the subsurface of the objects but maintaining the integrity of the probed samples. Thereby, the volumetric nature of the XCT investigations and its associated imaging techniques, ensure 3D quantitative measurements comparable to the output data from 2D metrology tools, but above all, supply the missing subsurface description for an exhaustive metrology study. The reward associated with XCT applied to multimaterial AM is a map reflecting the fabricated distribution of materials following CAD, with the benefits of better understanding the mechanical interplay within phases, hence, describing the hidden processes as well as the changes in phases due to a range of mechanical or chemical phenomena. In this study, a nondestructive approach using X-ray computed tomography (XCT) is used to fully evaluate the 3D distribution of multimaterials from an AM process. Specifically, two diverse hard and soft materials are alternatively produced in the form of a fibre embedded in a matrix via ink-jet printing. XCT coupled with imaging evaluation were able to distinguish between the differing materials and, importantly, to demonstrate a reduction in the expected fabricated volumes when compared to the respective CAD designs. LAY DESCRIPTION: Additive Manufacturing (AM) has recently become important in producing complex engineered structures. Using 3D CAD files and/or reconstructed data sets from imaging, hard and soft materials are manufactured independently or in combination, according to geometrical features and shapes in the input data. However, the evaluation of the resultant manufactured parts in comparison with the original 3D drawing is currently lacking. In this sense, X-ray computed tomography (XCT) provides an important metrology tool for mono and multimaterial AM. In this work a volumetric metrology investigation is proposed using higher resolution XCT to provide 3D information comparable to that of the 3D CAD drawings. A commercial high-resolution multijetting material printer (ProJet 5500X, 3D Systems, USA) is used to manufacture single fibre composites, through a complementary deposition of photo sensible polymers. Hard and soft plastics are produced using a UV curable step, resulting in materials of similar attenuation under an X-ray probe. A critical aim of the evaluations is the potential for XCT to distinguish between different UV curable 3D printing materials.

X-ray computed tomography (X-CT) plays an important role in non-destructive quality inspection and process evaluation in metal additive manufacturing, as several types of defects such as keyhole and lack of fusion pores can be observed in these 3D images as local changes in material density. Segmentation of these defects often relies on threshold methods applied to the reconstructed attenuation values of the 3D image voxels. However, the segmentation accuracy is affected by unavoidable X-CT reconstruction features such as partial volume effects, voxel noise and imaging artefacts. These effects create false positives, difficulties in threshold value selection and unclear or jagged defect edges. In this paper, we present a new X-CT defect segmentation method based on preprocessing the X-CT image with a 3D total variation denoising method. By comparing the changes in the histogram, threshold selection can be significantly better, and the resulting segmentation is of much higher quality. We derive the optimal algorithm parameter settings and demonstrate robustness for deviating settings. The technique is presented on simulated data sets, compared between low- and high-quality X-CT scans, and evaluated with optical microscopy after destructive tests.

Correlation between selective laser melting parameters, pore defects and tensile properties of 99.9 % silver

Introduction Three-dimensional (3D) copper nanostructures are expected to be applied as current collectors for lithium ion battery anodes due to their high electrical conductivity and large specific surface area. The production of 3D copper nanostructures usually requires complicated fabrication steps; however, we have developed a simple method for the production of 3D copper nanostructures.1) There is a disadvantage with this method in that the 3D copper nanostructure is likely to collapse due to low mechanical strength. Reinforcement of the 3D structures is thus considered to be one of the most effective methods to address this problem. This study aims to develop a reinforcement technology using a plating method that is applied after fabrication of the 3D copper nanostructures. The reinforcement technology employed here was viafilling plating technology. This technology is also expected to improve the adhesion to the substrate by selectively depositing copper to the bottom of the 3D nanostructure.Experimental A 3D copper nanostructure plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + 3×10-4 M polyacrylic acid) and a selective copper plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + additives) were prepared. A copper sulfate bath that does not contain additives was also employed for comparison. Pure copper and phosphorus-containing copper plates were used as the cathode and anode, respectively. Electrodeposition was conducted under galvanostatic conditions (1 A dm-2) without agitation at 25 °C. In addition, the influence of agitation on selective copper deposition was also investigated. Air agitation, magnetic stirring and a cathode rocker were used. The phase structure and microstructure of the deposits were analyzed using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. Results and discussion Figures 1a and 1d show a surface and cross-sectional SEM images of the 3D copper nanostructure before selective copper electrodeposition. Figure 1b shows a surface SEM image of the 3D copper nanostructure after electrodeposition without additives. The 3D nanostructure was not observed, because copper was deposited on the surface of the 3D nanostructure. The 3D nanostructure seems to have been deformed by the copper deposited on the surface, according to cross-sectional observations (Fig. 1e).Figure 1c shows a surface SEM image of the 3D copper nanostructure after electrodeposition with additives. The surface morphology is almost the same as the bare 3D nanostructure shown in Figure 1a because copper deposition at the surface of the 3D nanostructure is suppressed. Thus, the 3D nanostructure was maintained, and copper was deposited selectively at the boundary of the 3D nanostructure and the substrate, according to cross-sectional observations (Fig. 1f). Agitation also affected the selective copper deposition, and the results of agitation tests will be discussed at the meeting. References S. Arai and T. Kitamura, ECS Electrochem. Lett., 3(5), D7-D9 (2014). Figure 1

Additively manufactured (AM) metallic sheet-based Triply Periodic Minimal Surface Structures (TPMSS) meet several requirements in both bio-medical and engineering fields: Tunable mechanical properties, low sensitivity to manufacturing defects, mechanical stability, and high energy absorption. However, they also present some challenges related to quality control, which can prevent their successful application. In fact, the optimization of the AM process is impossible without considering structural characteristics as manufacturing accuracy, internal defects, as well as surface topography and roughness. In this study, the quantitative non-destructive analysis of TPMSS manufactured from Ti-6Al-4V alloy by electron beam melting was performed by means of X-ray computed tomography (XCT). Several advanced image analysis workflows are presented to evaluate the effect of build orientation on wall thicknesses distribution, wall degradation, and surface roughness reduction due to the chemical etching of TPMSS. It is shown that the manufacturing accuracy differs for the structural elements printed parallel and orthogonal to the manufactured layers. Different strategies for chemical etching show different powder removal capabilities and both lead to the loss of material and hence the gradient of the wall thickness. This affects the mechanical performance under compression by reduction of the yield stress. The positive effect of the chemical etching is the reduction of the surface roughness, which can potentially improve the fatigue properties of the components. Finally, XCT was used to correlate the amount of retained powder with the pore size of the functionally graded TPMSS, which can further improve the manufacturing process.

Carrier-based dry powder inhaler (DPI) formulations need to be accurately characterised for their particle size distributions, surface roughnesses, fines contents and flow properties. Understanding the micro-structure of the powder formulation is crucial, yet current characterisation methods give incomplete information. Commonly used techniques like laser diffraction (LD) and optical microscopy (OM) are limited due to the assumption of sphericity and can give variable results depending on particle orientation and dispersion. The aim of this work was to develop new three dimensional (3D) powder analytical techniques using X-ray computed tomography (XCT) that could be employed for non-destructive metrology of inhaled formulations. α-lactose monohydrate powders with different characteristics have been analysed, and their size and shape (sphericity/aspect ratio) distributions compared with results from LD and OM. The three techniques were shown to produce comparable size distributions, while the different shape distributions from XCT and OM highlight the difference between 2D and 3D imaging. The effect of micro-structure on flowability was also analysed through 3D measurements of void volume and tap density. This study has demonstrated for the first time that XCT provides an invaluable, non-destructive and analytical approach to obtain number- and volume-based particle size distributions of DPI formulations in 3D space, and for unique 3D characterisation of powder micro-structure.

Growth and characterization of lead molybdate (PbMoO4) single crystals have attracted increasing interest due to the variety of applications of these crystals [1–6]. Defect characterization, together with growth-related fundamental studies, were of special importance for many of the device requirements. This material was initially tested for its luminescence properties [7]. Subsequently, the main application has been in the field of acousto-optics because of its high acousto-optic figure of merit, low acoustic loss, low optical loss in the region 420 nm to 3900 nm and good mechanical impedance for acoustic matching [8, 9]. It has also attracted particular interest as one of the possible candidates for use in low temperature scintillator applications [10]. Difficulties associated with the growth of single crystals of lead molybdate have received significant attention due to a greater influence of thermal conditions during and after the growth [1, 11]. Zeng [12] has reported that when an as-grown crystal is held at a temperature close to the melting point for a long time, physical and chemical properties change. In the present investigation, single crystals of lead molybdate were grown by the Czochralski method with high purity starting materials of PbO and MoO3. They were mixed in the stoichiometric ratio and synthesized at around 800 8C with two intermediate grindings before melting. The pre-synthesized material was melted in a platinum crucible at 1063 8C. The detailed growth process has been discussed elsewhere [13]. The crystals for the present work were grown along the c-direction. As soon as the growth was terminated, the crystal was cooled at a rate of 20 8C hy1 to 500 8C and then at a relatively faster rate to room temperature. The crystal was not annealed at any intermediate temperature. The crystal was carefully cut along the aand c-directions using an internal diameter cutting machine so as to obtain a cube of 5 mm3 in size. The cut pieces were finally polished using 0.25 im diamond polishing paste. The cut and polished samples were subjected to chemical and thermal etching studies. Chemical etching was carried out using NaOH 5% solution as etchant at room temperature for 10–20 min. Since the cube was completely immersed in the etching solution, both aand c-faces were etched simultaneously under identical conditions. The etched samples were cleaned and their microstructure was analysed using an optical microscope (Leitz Metallux-II) in the reflection mode. Pits were not seen clearly on the cface whereas the a-face showed imperfection-induced arrow-headed etch pits (Fig. 1). A subgrain boundary was seen as a line of etch pits on the c-face (Fig. 2). This subgrain boundary line was observed on all samples cut perpendicular to the growth direction along the entire length of the crystal. This shows that the general nature of the subgrain boundaries is to run parallel to the pulling direction [14]. The process adopted for thermal etching is as follows. The samples were carefully loaded into a platinum boat and placed inside a resistively heated muffle furnace with temperature controlled by a Eurotherm 818P temperature controller. The furnace was heated to 900 8C at a rate of 30 8C hy1 and held at this temperature for 10 h. The furnace was then cooled at a rate of 10 8C hy1 to 600 8C and then at 25 8C hy1 to room temperature. After the heat treatment, the samples were analysed with an optical microscope. Heat treatment at 900 8C revealed thermal etch

A gray cast iron specimen was investigated by color and chemical etching with optical and atomic force microscopy, and the effect of grain orientation on the effectiveness of etching was examined. It was proven that the grain orientation dependence of chemical and color etching is just the opposite, and that the specimen surface after color etching is not uniformly smooth. Explanation for the layer structure of the color etched iron specimen is given.

In this paper, fully embedded circular‐stacked spiral inductors are investigated into a multilayered PCB substrate for low cost and miniaturized RF system on package (SOP) applications. The embedded circular‐stacked inductors are optimally designed to obtain high quality factor and self‐resonant frequency by using 3D EM simulator. The fabricated two‐turn circular‐stacked inductor has an inductance of 8.4 nH and a maximum quality factor of 67 at 1.2 GHz. The device size of the staked inductor is ∼65% of the planar inductor. The measured performance characteristics are well matched with the 3D EM‐simulated ones. The embedded circular stacked spiral inductors are promising for organic‐based SOP, which needs various functionality, low cost, small size and volume, and high packaging density. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1074–1077, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22354

Spheroidal graphite coalescence during thermal cycling in the ferritic domain of a high-silicon cast iron studied by optical microscopy and X-ray computed tomography

Using reduced sericin as a green resist for precise pattern fabrication via water-based lithography.

Shock synthesis and densification of tungsten based heavy alloys