Multilayer Substrate Research Articles

Nonlinear optical interactions in focused beams and nanosized structures

Thin-film materials from μm thickness down to single-atomic-layered 2D materials play a central role in many novel electronic and optical applications. Coherent, nonlinear optical (NLO) μ-spectroscopy offers insight into the local thickness, stacking order, symmetry, or electronic and vibrational properties. Thin films and 2D materials are usually supported on multi-layered substrates leading to (multi-)reflections, interference, or phase jumps at interfaces during μ-spectroscopy, which all can make the interpretation of experiments particularly challenging. The disentanglement of the influence parameters can be achieved via rigorous theoretical analysis. In this work, we compare two self-developed modeling approaches, a semi-analytical and a fully vectorial model, to experiments carried out in thin-film geometry for two archetypal NLO processes, second-harmonic and third-harmonic generation. In particular, we demonstrate that thin-film interference and phase matching do heavily influence the signal strength. Furthermore, we work out key differences between three and four photon processes, such as the role of the Gouy-phase shift and the focal position. Last, we can show that a relatively simple semi-analytical model, despite its limitations, is able to accurately describe experiments at a significantly lower computational cost as compared to a full vectorial modeling. This study lays the groundwork for performing quantitative NLO μ-spectroscopy on thin films and 2D materials, as it identifies and quantifies the impact of the corresponding sample and setup parameters on the NLO signal, in order to distinguish them from genuine material properties.

Multilayer thin film metallic glasses under nanoscratch: Deformation and failure characteristics

A nanoscratch technique to investigate the deformation and failure characteristics of multilayer thin film metallic glasses (TFMGs) is described. Nanoscratch experiments were performed on Zr-based multilayer (bilayer) TFMGs deposited over hard substrates (Si, soda-lime glass). Layer pattern and modulation ratio greatly influence the thin films failures under nanoscratch. When compared with pattern (layer-1 / layer-2) = (Zr65 / Zr55), multilayer TFMGs with layer pattern = (Zr55 / Zr65) shows better tribological performances regardless of substrate type (Si or SLG) under the considered nanoscratch conditions. This study is beneficial to find appropriate combination of layer pattern and modulation ratio to ensure good adhesion between multilayer TFMG and substrate.

Integrated Module Antenna for Automotive UWB Application

In this paper, an integrated module antenna for automotive UWB application is proposed. The target applications of the proposed antenna are for UWB localization and rear passenger detection. The purpose of this work is to design an antenna with a wide and narrow beamwidth that can be attached to the exterior/interior of a vehicle for simultaneous UWB localization and a rear passenger detection sensor with a single-module substrate in a limited space. For UWB localization, the wide beam coverage is required so the antenna receives the signal from any incident angle in horizontal plane. Meanwhile, the rear passenger detection sensor requires a relatively narrower beamwidth than the localization antenna for accurate detection within the vehicle. To integrate two different antennas into a single compact module substrate, modified ground stubs and parasitic radiators are applied. The size of the entire antenna structure is 35 mm × 65 mm × 1.156 mm. The proposed antenna designed on the multi-layered FR-4 substrate with a dielectric constant of 4.3. The bandwidth of the monopole is 6.14~8.24 GHz, and the patch array is 6.95~8.47 GHz. The isolation between the monopole and the patch array is less than −23 dBi in the target band. The performance of the proposed antenna is verified with simulation and measurement. In addition, a simulation of the proposed antenna with the real vehicle model is also conducted to verify the feasibility on actual vehicle. Based on this work, the proposed antenna can be applied to multi-function antenna for automotive application with low cost.

Multilayer packaging dual‐band balanced bandpass filter based on dual‐mode substrate integrated waveguide cavities with split‐type topology

A new design method of the dual-band balanced bandpass filter (BPF) using multilayer packaging dual-mode substrate integrated waveguide (SIW) cavities is proposed. Split-type coupling topology based on dual-mode resonators is developed for the design. Firstly, a single-band balanced filter with perturbed metal vias is designed. The TE201 mode and the TE202 mode perturbed by the metal vias can form a passband. Secondly, an additional metal vias perturbed SIW cavity with the same dual-mode is placed in the lower layer for the bandstop function. A dual-band balanced BPF with split-type coupling topology is successfully realised. Compared with the traditional cascaded single-mode form, the proposed dual-mode split-type design has more compact size and can be more easily extended to multi-passbands. To verify the proposed method, a dual-band balanced filter operating at 13.3 and 14.2 GHz is designed, fabricated and measured. The designed dual-band balanced filter has good filtering performance including differential mode passband transmission and common mode rejection. Measured results show good agreements with simulated ones.

Fast Construction of a Circuit Model for Via-Hole Transition Based on Liquid Crystal Polymer Multilayer Substrate

Fast Construction of a Circuit Model for Via-Hole Transition Based on Liquid Crystal Polymer Multilayer Substrate

Recent Advances in Multi-Material 3D Printing of Functional Ceramic Devices.

In recent years, functional ceramic devices have become smaller, thinner, more refined, and highly integrated, which makes it difficult to realize their rapid prototyping and low-cost manufacturing using traditional processing. As an emerging technology, multi-material 3D printing offers increased complexity and greater freedom in the design of functional ceramic devices because of its unique ability to directly construct arbitrary 3D parts that incorporate multiple material constituents without an intricate process or expensive tools. Here, the latest advances in multi-material 3D printing methods are reviewed, providing a comprehensive study on 3D-printable functional ceramic materials and processes for various functional ceramic devices, including capacitors, multilayer substrates, and microstrip antennas. Furthermore, the key challenges and prospects of multi-material 3D-printed functional ceramic devices are identified, and future directions are discussed.

A Ku-Band Miniaturized System-in-Package Using HTCC for Radar Transceiver Module Application.

This paper introduces a miniaturized system in package (SIP) for a Ku-band four-channel RF transceiver front-end. The SIP adopts the packaging scheme of an inner heat-dissipation gasket and multi-layer substrate in the high temperature co-fired ceramics (HTCC) shell with a metal heat sink at the bottom. The gasket effectively solves the heat-dissipation problem of high-power transceiver chips, and the multi-layer substrate achieves the interconnection between multiple chips. Within the limited size of 14.0 × 14.0 × 2.5 mm3, the SIP integrates five bidirectional amplifier chips, an amplitude-phase control multi-function chip, and two power modulation chips to realize the Ku-band four-channel RF transceiver front-end. Transmitting power over 0.5 W (27dBm) and receiving noise figure of 3.4 dB are achieved in the Ku-band. The efficient heat dissipation, high air tightness, and excellent integration are simultaneously realized in this SIP. The measurement results show that the performance is stable in the receiving and transmitting states, and the SIP based on HTCC technology has specific prospects for radar transceiver application.

Optical and Mechanical Properties of Layered Infrared Interference Filters.

The design and manufacturing technology of interference-absorbing short-wave filters based on a layered composition of Si-SiO on a sapphire substrate of various shapes was developed. A transition layer of SiO was applied to the surface of the substrate, alternating with layers of Si-SiO with an odd number of quarter-wave layers of materials with high (Si) and low refractive indices (SiO), and the application of an outer layer of SiO as an appropriate control of the materials' thickness. The optical properties of the infrared light filter were studied. It was established that the created design of the light filter provides the minimum light transmission in the visible region of the spectrum from 0.38 to 0.78 µm and the maximum in the near infrared region from 1.25 to 5 µm and has stable optical indicators. A method for studying the stress-strain state and strength of a multilayer coating of a light filter under the action of a local arbitrarily oriented load was developed. For simplicity in the analysis and for obtaining results in the analytical form, the one-dimensional model of the configuration "multilayer covering-firm substrate" constructed earlier by authors was used. From a mechanical point of view, the upper protective layer of the multilayer coating was modeled by a flexible plate, and the inner operational composite N-layer was subjected to Winkler's hypothesis about the proportionality of stresses and elastic displacements.

Microstructure and Electrochemical Performance of Rapidly Sintered LiCoO2 Cathodes

Lithium ion battery technology based upon liquid carbonate electrolytes and intercalation electrodes has achieved widespread commercial success. The batteries power mobile devices like cell phones, laptop computers and cordless power tools. They are used in hybrid and all electric vehicles to reduce greenhouse gas emissions and dependency on limited petrochemical resources. They have been demonstrated to stabilize electric grids at local and national levels under periods of high demand. Even with these remarkable achievements, improvements in energy density are sought in batteries for most applications. Lithium metal batteries are being pursued around the world to meet this need.Rapid, continuous, roll-to-roll sintering of alumina ceramic tapes was recently demonstrated at Corning Incorporated [1]. The process is based on the pioneering work of Ketcham et al [2]. The ceramic tape, because it is thin, is flexible and may be heated, sintered, and cooled back to room temperature in less than one hour without cracking. One application of this technology is for manufacture of thin, <30 µm, solid electrolyte separators. Another is to enable novel, cathode-supported battery architectures. To that end, rapid sintering has been extended to lithium cobaltite (LCO). Continuous sintering and winding of LCO is shown in Fig. 1. The LCO cathode because it is sintered and self-supporting may be used to reduce the proportions of inactive components to dramatically increase energy density. Both composite and dense cathodes can be envisioned.One possible way of creating a solid-state battery with LCO ribbon is to capitalize on the LiPON solid electrolyte originally developed at ORNL for thin-film micro-batteries (TFMB’s) [3, 4]. The materials in TFMB’s have proven track records and attractive performance attributes. The LiPON solid electrolyte in contact with a lithium metal anode is resistant to dendrite formation even at current densities >5 mA/cm²; a claim that cannot be made for lithium garnet and lithium phosphosulfide glass [5, 6].TFMB’s also have tremendous cycling longevity and retain more than 90% of capacity after over 104 charge-discharge cycles [7]. The challenge with the technology is the high cost associated with growth of the cathode by sputtering processes; thicknesses are limited to ~2-3 µm. As a consequence, TFMB’s are a good fit for applications where small size power sources are needed like smart cards, medical implants, RFID tags, and wireless sensing. A thicker, rapidly sintered cathode could address the cost-capacity limitation. The cathode for this architecture could be made in a dense, closed pore form or with 15-25% porosity to host and electrolyte. The later would be expected to offer greater rate performance due to shorter diffusion distances and greater surface area for charge transfer. Energy density of more than 1,500 Wh/L is theoretically achievable.The performance of cathode materials like LCO depends upon synthesis conditions, process history, design and microstructure. We explore the electrochemical attributes of free standing LCO cathodes with thickness of 15 to 80 µm and porosity ranging from closed (dense) to ~25%. Cathodes were tested in 2032 coin cells using Whatman glass fiber as the separator and 1 M LiPF6 in 1:1 EC:DMC. Capacity of the cathodes regardless of microstructure is near the theoretical value. Lithium diffusivity of dense polycrystalline cathodes was characterized by galvanostatic intermittent titration and averages 1.13×10-9 cm²/s over the potential window of 3.0 to 4.3 V. Surface XRD shows the grain texture to be nominally random. Approximately 50% capacity was available at C/2 at a 23 µm thickness. Resistance of porous cathodes decreased with perimeter-to-surface area, and effective resistances below 10 Ωcm² were observed. Cycling endurance of porous sintered cathodes with 2.4 mAh/cm² capacity was evaluated with lithium titanate working electrodes. More than 90% capacity was retained after 1000 cycles between 3.0 and 4.3 V vs Li at 3C rate.[1] C. Kim, et al, “5G mm Wave Patch Antenna on Multi-layered Alumina Ribbon Ceramic Substrates,” IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting, July 2020, pp. 65-66.[2] T.D. Ketcham, et al., US 5,089,455, Feb 18, 1992.[3] J.B. Bates, et al., Solid State Ionics, 53-56 (1992) 647-654.[4] J.B. Bates, et al., U.S. 5,561,004, Oct 10, 1996.[5] F.D. Han, et al., Nat. Energy, (2019) 1-10.[6] J.C. Li, et al., Adv. Energy. Mater., 5 (2015) 1401408.[7] J. Xie, et al., Solid State Ionics, 178 (2008) 362-370. Figure 1

Reliability Analysis of Large-Area, Low-Pressure-Assisted Silver Sintering for Medium-Voltage Power Modules

Multi-layer insulating ceramic substrates can enable medium-voltage (MV) power modules with reduced peak electric field. This benefit is particularly important for MV silicon carbide (SiC) MOSFETs due to their higher operating voltages. Large-area, low-pressure-assisted silver sintering is a potential solution for bonding substrates to create a multi-layer structure. The voiding content and defect density of the bond used to create the multi-layer substrate stack-up are critical to the reliability of the power module and thermal performance, as this bond is in the primary path for heat dissipation in the power module structure. Samples of two-layer direct bonded aluminum (DBA) stacks have been fabricated and subjected to thermal cycling to analyze their reliability. Passive thermal cycling from −40 °C to 200 °C was performed. Cross sections were cut at pre-determined intervals and imaged with scanning electron microscopy (SEM). After 1000 thermal cycles, adhesive failures are observed between the sintered silver and DBA surface. Cross sections were cut and imaged via optical microscope and SEM. Thermal analyzer measurements are recorded on a 10-kV SiC power module using the sintered DBA substrate stacks.

Effect of bilayer numbers on structural, mechanical, tribological and corrosion properties of TiO2–SiO2 multilayer film-coated β-type Ti45Nb alloys

Protective films with excellent tribological performance and good corrosion resistance are needed in general because titanium implants are used in aggressive environments and always suffer from severe wear and corrosion. In this study, TiO2–SiO2 multilayer films were deposited with different numbers of bilayers (2, 4, and 8) on β-type Ti45Nb alloy substrates by physical vapour deposition. The influence of number of bilayers on microstructure, wettability, mechanical features, tribological performance and electrochemical behaviour of TiO2–SiO2 multilayer films were comparatively observed via XRD, XPS, SEM, AFM, nanoindentation tester, contact angle measurement system, reciprocating tribo-tester, and electrochemical corrosion media. The surface hardness, wear and corrosion resistance values of multilayer film-coated substrates were higher than the untreated substrate values. These properties and adhesion resistance and hydrophobicity of coated samples also increased with increase in number of bilayers due to the smaller grain size, increased layered interfaces and high structural density.

Femtosecond Laser Fabrication of Microporous Membranes for Biological Applications.

The possibility of fabricating micrometric pore size membranes is gaining great interest in many applications, from studying cell signaling, to filtration. Currently, many technologies are reported to fabricate such microsystems, the choice of which depends strictly on the substrate material and on the final application. Here, we demonstrate the capability with a single femtosecond laser source and experimental setup to fabricate micromembranes both on polymeric and multilayer metallic substrate, without the need for moulds, mask, and complex facilities. In particular, the flexibility of laser drilling was exploited to obtain microfilters with pore size of 8 and 18 µm in diameter, on metallic and polymeric substrate, respectively, and controlled distribution. For evaluating the possibility to use such laser-fabricated membranes into biological assay, their biocompatibility has been investigated. To this aim, as a proof of concept, we tested the two materials into viability tests. The culture of mammalian cells on these microfabricated membranes were studied showing their compatibility with cells.

Temperature Self-Compensation Method for Crack Length Measurement Based on a Microstrip Antenna Sensor

A temperature self-compensation method for the microstrip antenna sensor is innovatively proposed to reduce the measurement error associated with temperature variation. Temperature compensation is achieved by inserting a layer of compensation substrate in the resonant cavity of the antenna sensor. The compensation substrate with a thermal coefficient of the dielectric constant opposite that of the sensor substrate is designed to offset the frequency variation of the sensor. The design parameters of the sensor are obtained from multi-layer substrate theory and microstrip antenna theory. The temperature compensation performance of the sensor is experimentally and numerically analyzed to validate the proposed method. The results show that the microstrip antenna sensor proposed in this paper provides more accurate measurement results of the structural crack length with an identification error of ±0.2mm within the temperature range of 0 to 60 °C. This reduces the measurement error of the crack length in a multi-temperature environment by more than 95%, relative to that of conventional microstrip antenna sensors.

Opposite surface stress induced the distinctly different contact behaviors of monolayer and bilayer borophene on Ag(1 1 1)

The experimental synthesis of the boron sheets beyond a single layer is a challenge in low-dimensional physics, and the interaction mechanism between multilayered boron sheets and metal substrates remains unclear. Here, we propose an exchange-transfer mechanism to understand the distinctively different behaviors of monolayer (ML) and bilayer (BL) borophene contacts on Ag(111) based on first-principles calculations. It is shown that threefold enhancement of the tensile surface stress in the BL borophene plays a vital role in this exchange-transfer mechanism, while released compressive surface stress was found for ML borophene covers on Ag(111). The feature of the mechanism is that the dz2 electrons on the Ag(111) transferring to the pz orbital of the bridged B pillars are compensated mainly by the electrons from the bottom B px + py orbitals. This mechanism causes more interaction density states between the Ag(111) and BL borophene while not found in the ML borophene. In addition, the analysis of surface stress indicates that it has high feasibility of growing BL borophene by chemical vapor deposition method on Al and Au substrates.

Investigation of Terahertz Wave Propagation along Symmetric Coplanar Strpline on Multilayer Dielctric Substrates

Characteristics of the symmetric coplanar strip line on multi-layer dielectric substrates expressed in analytic formulas have been obtained using conformal mapping. But in most previous presented papers, the metal strip is considered as infinitely thin or PEC while the influence of dielectric substrates are not considered. In this paper, the propagation characteristics of symmetric coplanar strip line with finite conductivity and finite metal strip thickness on multilayer substrates are analyzed by conformal mapping at THz regions. The influences of metal strips and dielectric substrates on the propagation characteristics of CPS are also given. The numerical results are very useful for the development of terahertz devices and terahertz material.

Broadband tunable coding metasurfaces based on a metal patch and graphene for beam control at the terahertz frequencies.

We present a broadband tunable coding metasurfaces structure using a cruciate metal patch and circular graphene on a multilayer substrate. By changing the Fermi level of the graphene, we can achieve obvious reflection phase variation to design multi-bit coding metasurfaces. In the research of 1-bit coding metasurfaces, we combine the advantages of graphene and copper to realize the real-time adjustment of the reflected waves in four broadband frequency bands. In this case, we can control the number of far-field reflected waves in the frequency range of 5.45-6.45 THz. Then, we create 2-bit and 3-bit coding modes on the basis of 1-bit coding metasurfaces to obtain a single beam of reflected waves. Finally, we use the convolution calculation to realize the real-time adjustment of the single beam reflection direction from 0° to 360° in the azimuthal plane. Research of the 2-bit and 3-bit coding modes also provides a way to control the number and direction of the reflected beam, specifically in the 1-bit coding mode. The present coding metasurfaces structure provides inspiration for the design of functional devices in future-oriented intelligent communication.

Miniaturized Quarter-Mode SIW Filters Loaded by Dual-Mode Microstrip Resonator With High Selectivity and Flexible Response

A novel miniaturized multilayer quarter-mode substrate integrated waveguide (QMSIW) filter with high selectivity and wide stopband is proposed. First, an innovative multilayer dual-mode microstrip resonator is proposed to couple the QMSIW resonators located at the upper and lower substrate layers. The combination of the dual-mode resonator with the two QMSIW cavities leads to a fourth-order filtering response. Then, the coupling iris is opened at the position, where the magnetic field distribution in the QMSIW cavity achieves a peak value. Finally, sharp skirt is obtained by composing the modified box-like topology. In addition, different responses could be achieved by changing the position of the coupling iris, resulting in a wide stopband and flexible response. The size of the filter is also reduced through the multilayer QMSIW configuration and miniaturized multilayer dual-mode microstrip resonator.

28 GHz and 38 GHz Dual-Band Vertically Stacked Dipole Antennas on Flexible Liquid Crystal Polymer Substrates for Millimeter-Wave 5G Cellular Handsets

Minimizing the size of mobile antennas is necessary for integrating the components inside a mobile device. Wideband and multiband antennas are also required to cover various 5G mobile communication frequency spectra. This article presents a vertically stacked dipole antenna array operating in the 28/38 GHz dual-band. The proposed antenna is small and satisfies the need for wide bandwidth in the form of a dual band. The antenna structure has symmetric 38 GHz band radiators positioned above and below a multilayer substrate, and a 28 GHz band radiator positioned on the middle plane, providing a dual-band antenna structure with small lateral width. Herein, two types of antenna structures are proposed, each with a single-ended and differential feed structure for compatibility with various RF front ends. The single antenna yields &#x2212;10 dB bandwidth for return loss of 23.9&#x0025; and 14.4&#x0025;, and gain of 4.8 and 4.6 dBi at 28 and 38.5 GHz, respectively. The 4-element antenna array yields a gain of 9.0 dBi at 28 GHz and 10.3 dBi at 38.5 GHz. It was fabricated on a flexible substrate and can be bent and inserted into the lateral edge of the terminal. The proposed antenna elements and arrays satisfy the performance factors requisite for millimeter wave 5G communication including compact size, wideband, dual-band, and adequate gain.

Developing Broadband Microstrip Patch Antennas Fed by SIW Feeding Network for Spatially Low Cross-Polarization Situation.

A stacked multi-layer substrate integrated waveguide (SIW) microstrip patch antenna with broadband operating bandwidth and low cross-polarization radiation is provided. A complete study on the propagating element bandwidth and cross polarization level is presented to demonstrate the importance of the design. The proposed antenna includes three stacked printed circuit board (PCB) layers, including one layer for the radiating 2 × 2 rectangular patch elements and two SIW PCB layers for the feeding network. There are two common methods for excitation in cavity-backed patch antennas: probe feeding (PF) and aperture coupling (AC). PF can be used to increase the bandwidth of the antenna. Although this method increases the antenna’s bandwidth, it produces a strong cross-polarized field. The AC method can be used to suppress cross-polarized fields in microstrip patch antennas. As microstrip patch antennas are inherently narrowband, the AC method has little effect on their bandwidth. This paper proposes an antenna that is simultaneously fed by AC and PF. As a result of this innovation, the operating bandwidth of the antenna has increased, and cross-polarization has been reduced. Actually, the combination of probe feeding and aperture coupling schemes leads to achieving a broadband operating bandwidth. The arrangement of radiator elements and cavities implements a mirrored excitation technique while maintaining a low cross-polarization level. In both numerical and experimental solutions, a less than −30 dB cross-polarization level has been achieved for all of the main directions. A fractional impedance bandwidth of 29.8% (10.55–14.25 GHz) for < −10-dB is measured for the proposed array. Simulated and measured results illustrate good agreement. Having features like low cost, light weight, compactness, broadband, integration capabilities, and low cross-polarization level makes the designed antenna suitable for remote-sensing and satellite applications.

Multilayer Conductive Metallization With Offset Vias Using Aerosol Jet Technology

Abstract The transition of additive printed electronics into high-volume production requires process consistency to allow quality control of the manufactured product. Process recipes are needed for multilayer substrates with z-axis interconnects in order to enable complex systems. In this paper, process recipes have been developed through fundamental studies of the interactions between the process parameters and the mechanical–electrical performance achieved for multilayer substrates. The study reported in this paper focuses on printed vias also known as donut vias. Aerosol jet process parameters studied include carrier mass flow rate, sheath mass flow rate, exhaust mass flow rate, print speed, number of passes, sintering time and temperature, UV-intensity for UV-cure, and standoff height. The electrical performance has been quantified through the measurements of resistance. The mechanical performance has been quantified through measurement of shear load-to-failure. The effect of sequential build-up on the mechanical–electrical properties vs process parameters has been quantified for up to eight-layers designs. The performance of five-layer and eight-layer additively printed substrate designs and effect of multiple vias has been compared to assess process consistency.