Thin Printed Circuit Board Research Articles

Low-Profile Millimeter-Wave Metasurface-Based Antenna with Enhanced Bandwidth.

A millimeter-wave broadband metasurface-based antenna with a low profile is proposed. In order to guide the mode excitation, the characteristic mode analysis (CMA) is used for the design and optimization of the proposed antenna. Four sets of coplanar patches with different dimensions on a thin printed circuit board are used to generate four adjacent broadside modes, which are directly fed by a coaxial probe. Then, to expand low-frequency bandwidth, a new resonant mode is introduced by etching slots on the parasite patch. Meanwhile, the extra mode introduced does not significantly change the radiation performance of the original modes. Moreover, dual slots are etched on the mid patch fed by the coaxial probe, which moves the orthogonal modes of the chosen modes out of the operating band to reduce cross-polarization levels. The proposed antenna realized 25.02 % (30-38.58 GHz) impedance bandwidth with dimensions of 1.423×1.423×0.029λ0 3 (λ0 is the wavelength at 34 GHz in free space), and the realized gain in the band is 8.35-11.3 dB.

Design and studies of thick Gas Electron Multipliers fabricated in India

THick Gas Electron Multipliers (THGEMs) are robust and high gain Micro Pattern Gaseous Detectors which are economically manufactured by standard drilling and etching of thin printed circuit boards. In this paper, we present our recent simulation as well as experimental studies on THGEMs which have been fabricated in India using local expertise. Two types of THGEMs have been fabricated; one set has holes without any external rim and another set has holes with rims. These detectors have been characterized using argon-carbon dioxide and argon-isobutane gas mixtures. Electron transmission, effective gain, energy resolution, optimized working range and charging up studies have been presented for both the sets of THGEMs.

Results of magnetometry of spheres’ chains as basic structural elements of a granulated material

During the magnetization of a granulated material with back filling of ferromagnetic spheres, the chains of contacting granules (spheres) serve as self-sufficient conductors of the magnetic flux. Each of such chains is characterized by a pronounced redistribution of the magnetic flux along its cross section. If in the chain of spheres with radius R the conditional core with radius r is selected, and then this core is surrounded by a loop placed between the contacting spheres in order to measure magnetic flux, it has been found that an increase in r decreases the thread density (magnetic induction). The data for magnetic flux are given for a different relative radius r/R of the cores of two chains differing only in R. For this purpose, the sensors created in the form of circular circuits based on thin printed circuit boards have been used. According to recorded magnetic flux, the detailed information on magnetic induction within the cores and their magnetic permeability under the magnetization of the chains in a solenoid has been obtained. It has been shown that as the ratio r/R increases, i.e., with the thickening in the conditional cores and the corresponding increase in magnetic flux, both magnetic induction and magnetic permeability significantly reduce. The complete mutual agreement of the corresponding r/R-dependence of magnetic induction and magnetic permeability is demonstrated for both chains, what indicates the potential in applying the results obtained for the chains of spheres of other radii.

A chain of granules as a model element of a “bundle” of chains in a magnetized matrix: New opportunities for diagnostics

In accordance with the model of matrix magnetization from the filling of granules, a “bundle” of conductor channels of magnetic flux formed along the chains of granules (spheres) and the magnetic parameters of the conditional cores of a chain of spheres with a radius of R = 15 mm (but different in radius r) were studied. The research was developed by measuring magnetic flux sensors in the form of technologically advantageous (for measurements in small volumes) circular contours of different relative radii (r/R = 0.2–0.9) on thin printed circuit boards placed between adjacent spheres in the middle chains. This study presents an array of data on the measurement of the magnetic flux Φ in the cores of a chain of spheres with a radius of R = 15 mm when magnetized in a solenoid by a 4.8 to 54.5 kA/m field. The values of the magnetic induction B in the cores (and their magnetic permeability µ) have been determined. As r/R increases (i.e., as the conditional cores thicken), despite the increase in Ф, B and μ values decrease due to a reduction of the ferromagnetic metal's volume in the core. Using the example of the induction field dependences the qualitative and quantitative similarity of the magnetic properties of the poly-ball medium-filling and the chain of spheres (r/R → 1) is shown. This example confirms the status of the chain of spheres as a physically self-sufficient model element responsible for magnetizing the granular medium matrix.

Towards a model of chain-by-chain magnetization of a granular medium: a variant of magnetic diagnostics of chains of spheres

In addition to information on the magnetic parameters of inhomogeneous magnetics, in particular, granular magnetics usually studied within the framework of the quasi-continuous medium model, it is of no less interest to obtain information from the standpoint of the model, when the object of study is the characteristic elements of an inhomogeneous magnetic. According to the well-proven model of selective magnetization of a granular medium, the elements that make up this medium are chains of granules – straight and sinuous, always manifesting themselves in the direction of its magnetization. They perform the function of conductor channels of the generated magnetic flux through the granular medium. As a result, it is a kind of branched «bundle» of conductor channels. For any of the chains of granules, for example, granules-balls of radius R, conceptually significant are the magnetic parameters of its conditional cores with radius r ≤ R, and these parameters, first of all, the magnetic permeability of quasi-continuous cores and magnetic induction in them, for different (in r) cores are variable, which requires appropriate magnetic diagnostics. To clarify the magnetic parameters of the conditional cores of a chain of granules-balls, as a physically self-sufficient element of a granular medium (i.e., in accordance with the model of chain-link magnetization of such a medium), it is practical to make measuring magnetic flux sensors in the core as circular sensors surrounding the contact point of granules-balls, however, not as traditional wire loops, but as circuits on thin printed circuit boards (with mounting holes) placed between adjacent balls. Based on the obtained data of the magnetic flux in cores of different radii r (r/R = 0.2–0.9) of a chain of spheres with a radius of R = 20 mm, the values of the magnetic induction B in them, as well as their magnetic permeability μ, were determined when the chain is magnetized in the solenoid by a field of strength from 4.8 to 54.5 kA/m. It is shown that with formal thickening of the cores, the values of B and μ decrease due to a decrease in the volume of the ferromagnet in the core, and for the limiting core (r/R → 1), i.e., for the chain as a whole, they correspond to the values of B and μ for a poly-ball backfill medium.

Deformation and Anchoring of AA 2024-T3 rivets within thin printed circuit boards

This work evaluates the viability of applying Friction Riveting as an alternative for the assembly of components on printed circuit boards (PCBs). The popular press-fit technology for assembling components on PCBs consists of a pin inserted tightly into a relatively smaller hole, resulting in good electrical and mechanical properties. However, some limitations are highlighted, such as numerous processing steps and the need for predrilled holes. Friction Riveting is based on mechanical fastening and friction welding principles, where polymeric components are joined with metallic rivets through frictional heating and pressure. The main benefits of using Friction Riveting in PCBs compared with fit-press are (i) a reduced number of processing steps and (ii) shorter joining cycles, because there is no pre-drilling involved with fasteners anchored within the PCB in a single step. The joints were manufactured using 5 mm diameter AA-2024-T3 rivets and 1.5 mm thick glass-fiber-reinforced epoxy laminates (FR4-PCB). It is shown for the first time that it is possible to deform metallic rivets within thin composite plates at a reduced diameterto-thickness ratio. The feasibility study followed a one-factor-a-time approach for parameter screening and optical microscopy assessed joint formation of the deformed rivets inside the laminates through volumetric ratio (VR). The joints present significant deformation (VR=0.5) at the tip of the rivet inserted into overlapped PCBs plates, with thicknesses below 3.0 mm, which is considered the lowest achieved so far with Friction Riveting.

Analysis and Design of Asymmetric Mid-Range Wireless Power Transfer System with Metamaterials

In a wireless power transfer (WPT) system, the power transfer efficiency (PTE) decreases sharply with the increase in transfer distance. Metamaterials (MMs) have shown great potential to enhance PTE in mid-range WPT systems. In this paper, we propose two MM slabs of a 3 × 3 array to enhance the magnetic coupling. The MM unit cell was designed by using square spiral patterns on a thin printed circuit board (PCB). Moreover, the asymmetric four-coil WPT system was designed and built based on the practical application scenario of wireless charging for unmanned devices. The simulation and experimental results show that two MM slabs can enhance power transmission capability better than one MM slab. By optimizing the position and spacing of two MM slabs, the PTE was significantly improved at a mid-range distance. The measured PTEs of a system with two MM slabs can reach 72.05%, 64.33% and 49.63% at transfer distances of 80, 100 and 120 cm. When the transfer distance is 100 cm, the PTE of a system with MMs is 33.83% higher than that without MMs. Furthermore, the receiving and load coils were integrated, and the effect of coil offset on PTE was studied.

PCB-Embedded GaN-on-Si Half-Bridge and Driver ICs With On-Package Gate and DC-Link Capacitors

A low-inductive half-bridge and gate driver package with on-package gate and dc-link capacitors is realized by printed circuit board (PCB) embedding of two GaN-on-Si ICs. While monolithic half-bridge and driver integration reduces on-chip parasitics, it does not solve the interconnection challenge to external capacitors. This letter solves this issue through advantageous combination of PCB embedding and monolithic circuit integration. This letter uses GaN-on-Si power circuits with integrated gate drivers, freewheeling diodes, and temperature and current sensors. GaN ICs are fabricated with thick copper on both sides, which makes them applicable to commercial PCB-embedding technologies. Thermal aspects are discussed and electromagnetic simulations used to compare the PCB-embedded package to a bond wire based package. A PCB-embedded dc–dc converter is operated up to 350 V and 450 W with up to 98.7% efficiency. 380 V hard-switching transitions show below 8% over- and undershoot despite over 120 V/ns slew rates. Parallel platelike placement of silicon flip-chip capacitors above the gate driver final stage transistors and separated only by a thin PCB layer increased the gate-loop parasitic inductance by only 40 pH.

A Dual-Perforation Electromagnetic Bandgap Structure for Parallel-Plate Noise Suppression in Thin and Low-Cost Printed Circuit Boards

In this study, we propose and analyze a dual-perforation (DP) technique to improve an electromagnetic bandgap (EBG) structure in thin and low-cost printed circuit boards (PCBs). The proposed DP–EBG structure includes a power plane with a square aperture and a patch with an L-shape slot that overcomes efficiently the problems resulting from the low-inductance and the characteristic impedance of the EBG structure developed for parallel-plate noise suppression in thin PCBs. The effects of the proposed dual-perforation technique on the stopband characteristics and unit cell size are analyzed using an analytical dispersion method and full-wave simulations. The closed-form expressions for the main design parameters of the proposed DP–EBG structure are extracted as a design guide. It is verified based on full-wave simulations and measurements that the DP technique is a cost-effective method that can be used to achieve a size reduction and a stopband extension of the EBG structure in thin PCBs. For the same unit cell size and low cut-off frequency, the DP–EBG structure increases the stopband bandwidth by up to 473% compared to an inductance-enhanced EBG structure. In addition, the unit cell size is substantially reduced by up to 94.2% compared to the metallo–dielectric EBG structure. The proposed DP–EBG technique achieves the wideband suppression of parallel plate noise and miniaturization of the EBG structure in thin and low-cost PCBs.

Thin Hybrid Metamaterial Slab With Negative and Zero Permeability for High Efficiency and Low Electromagnetic Field in Wireless Power Transfer Systems

Current wireless power transfer (WPT) systems have limited charging distance and high induced electromagnetic field (EMF) leakage. Thus, we first proposed a thin printed circuit board (PCB) type hybrid metamaterial slab (HMS) combining two kinds of metamaterial cell structures. The metamaterial cells in the center area of the HMS have zero relative permeability and straighten the magnetic field direction. The metamaterial cells located at the edges of the HMS have negative relative permeability and change the outgoing magnetic fields to opposite direction by magnetic boundary condition. Therefore, the magnetic field can be more confined between transmitter and receiver coils, enhancing the power transfer efficiency, while decreasing the EMF leakage in a WPT system. In this paper, we demonstrated that increased power transfer efficiency from 34.5% to 41.7% and reduced EMF leakage from −19.21 to −26.03 dBm in 6.78-MHz WPT system. Furthermore, we proposed new analysis method for relative permeability measurement of the metamaterial using a novel cubic structure with perfect electrical conductor and perfect magnetic conductor boundary.

Novel Ultra Wide Band Polarisation Independent Capacitive Jaumann Radar Absorber

<p style="margin-bottom: 0.14in; line-height: 115%;" align="justify">An ultra wide band (UWB), reduced thickness four layers capacitive jaumann absorber (CJA) with measured reflectivity of -15 dB (minimum) from 2 GHz to 19 GHz is presented in this paper. The novel CJA is designed and implemented by modifying the jaumann absorber (JA) design. The crucial impedance matching layers of CJA are designed by conceptualizing hexagonal resistive grid on dielectric substrates. Reduced thickness of 24.8 mm is realised by capacitive loading of hexagonal resistive grids with hexagonal resistive patches. Absorption performance of CJA is verified by full wave analysis using high frequency structural simulator software. Polarisation independent absorption performance is realised. Absorption of 96.5 per cent (minimum) is achieved with variation in angles of incidence from 0° to 30°. Resistive capacitive layers of CJA are developed as electrically thin printed circuit boards and integrated with alternating low loss, low density foam dielectric spacers backed by metallic conducting plane. Size of panel CJA is 280 mm × 280 mm. Fabricated panel CJA is evaluated for radar cross section (RCS) performance in microwave anechoic chamber. Matching results are obtained in simulation and measurements. The reduced thickness, low weight, UWB CJA finds application in RCS reduction of air vehicles/unmanned air vehicle. <span class="Apple-converted-space"> </span></p>

Study of resin flow in carbon fiber reinforced polymer composites by means of pressure sensors

This paper presents an evaluation of resin flow in carbon fiber reinforced polymer by means of small embedded pressure sensors. High-quality carbon fiber reinforced polymer parts require entire impregnation of fibers with resin before resin curing starts. Small piezo-resistive pressure sensors are used to measure the vacuum hold and to track resin flow and pressure elevation inside the composite part. The sensors are placed at different locations in the fiber stacks. Real-time pressure changes are obtained inside the laminate during infusion. To reduce the size of the embedded sensing element, the sensor dies are flip-chipped on a thin printed circuit board. The two component thermoset resin (RIM 035 c) and uni-directional carbon fiber with the alignment of 30° are used in a complex-shaped mold. The result shows that the flip-chipped piezo-resistive pressure sensors can be used in conductive fibers to monitor resin arrival and pressure development in vacuum assisted resin transfer molding infusion processes. The sensors are supplied by a constant current source to compensate the sensitivity reduction if the temperature changes in the curing process.

Folded Multilayer C-Sections With Large Group Delay Swing for Passive Chipless RFID Applications

An origami-based multilayer structure suitable for passive chipless radio frequency identification applications is presented in this paper. Contrary to the existing multilayer designs where metallic via is used for the interconnections, the proposed technique uses the folding of the structure designed in a flexible substrate. Thus, the multilayer structure is obtained from a thin printed circuit board that is folded to give the desired 3-D structure. The proposed structure consists of cascaded commensurate transmission line sections (also known as C-sections) coupled at alternative ends. The group delay (GD) characteristic of the C-sections is utilized for encoding. Broad side coupling of the structure is exploited here, which enables large GD with higher frequency selectivity. It is proved that to produce the same amount of delay, linearly cascaded C-sections demands five times more number of C-sections than that of a multilayered structure, which also signifies the factor of miniaturization of the proposed design. A coding capacity of 6 and 12 b is estimated from the simulation, respectively, for single group and multigroup of multilayered C-sections in the allowed industrial, scientific, and medical (ISM) bands. This shows for the first time that frequency domain chipless technology can be compatible with the use of ISM bands. It also allows a coding capacity of 43 b in the ultra-wideband band which is comparable with the EAN 13 barcode.

A PDMS-Based Integrated Stretchable Microelectrode Array (isMEA) for Neural and Muscular Surface Interfacing

Numerous applications in neuroscience research and neural prosthetics, such as electrocorticogram (ECoG) recording and retinal prosthesis, involve electrical interactions with soft excitable tissues using a surface recording and/or stimulation approach. These applications require an interface that is capable of setting up high-throughput communications between the electrical circuit and the excitable tissue and that can dynamically conform to the shape of the soft tissue. Being a compliant material with mechanical impedance close to that of soft tissues, polydimethylsiloxane (PDMS) offers excellent potential as a substrate material for such neural interfaces. This paper describes an integrated technology for fabrication of PDMS-based stretchable microelectrode arrays (MEAs). Specifically, as an integral part of the fabrication process, a stretchable MEA is directly fabricated with a rigid substrate, such as a thin printed circuit board (PCB), through an innovative bonding technology-via-bonding-for integrated packaging. This integrated strategy overcomes the conventional challenge of high-density packaging for this type of stretchable electronics. Combined with a high-density interconnect technology developed previously, this stretchable MEA technology facilitates a high-resolution, high-density integrated system solution for neural and muscular surface interfacing. In this paper, this PDMS-based integrated stretchable MEA (isMEA) technology is demonstrated by an example design that packages a stretchable MEA with a small PCB. The resulting isMEA is assessed for its biocompatibility, surface conformability, electrode impedance spectrum, and capability to record muscle fiber activity when applied epimysially.

노트북용 액정 모듈 내부의 온도 및 상대 습도 변화에 관한 실험적 연구

노트북용 액정 모듈 내부의 광학 시트(Optical Sheet) 변형에 기인한 시인성 품질 불량을 개선하기 위한 기초 연구의 일환으로 변형 유발의 요인인 온도 및 습도의 영향을 분석할 수 있는 측정 시스템이 필요하였다. 액정 모듈 내부에는 0.5㎜ 미만의 미세한 공기 층이 존재하는데, 이 공간으로 외부의 습한 공기가 내부로 확산되는 것으로 추정된다. 이러한 현상을 규명하기 위하여 초소형 온도 및 습도 센서를 실장한 초박형 센서 PCB 를 액정 모듈 내부에 삽입하여 실시간으로 온/습도 변화를 측정 및 분석하였으며, 향후 변형 거동 시뮬레이션 및 구조 설계 시 필요한 기초 데이터로 활용하고자 한다.

Integrated Design and Manufacturing of Flat Miniature Heat Pipes Using Printed Circuit Board Technology

A novel, integrated approach in thermal management of electronic products, based on two-phase cooling, is presented. A flat miniature heat pipe, integrated inside the laminated structure of a printed circuit board (PCB) has been developed, based on mainstream PCB fabrication processes. Hot spots on the PCB, caused by heat dissipating components, can be cooled with relatively small temperature gradients across the board. An analytical model is presented to predict the behavior of the embedded heat pipe for various geometries, orientations, and operating temperatures. Experimental verification has shown successful heat pipe operation. The heat pipe exhibited a measured equivalent thermal conductivity more than seven times higher than solid copper. Low-thermal resistance values establish this concept as a promising thermal management solution for future electronic products. As mainstream manufacturing techniques are applied, thin PCBs with integrated cooling support can be produced at low-cost.

Micro-assembled multi-chamber thermal cycler for low-cost reaction chip thermal multiplexing

Abstract This paper presents a miniaturised multi-chamber thermal cycler capable of thermal multiplexing for high throughput polymerase chain reaction (PCR) of nucleic acids, using low-cost reaction chip. The thermal cycler has been fabricated in a micro-assembly manner using flip–chip bonding technique, which is batch manufacturable with good reproducibility. Silicon heating blocks in the multi-chamber array are mounted on a printed-circuit-board (PCB) substrate, with the later attached to a metal plate heat sink. Thermal cross-talk has been minimised by using thin and low thermal conductivity PCB. The preferred reaction chip containing multiple chambers is made of low-cost plastics, while other PCR compatible materials are also possible. The preliminary experiments show that with up to 20 μl sample in the thermally formed plastic chip, a full speed of 8 min for 30-cycle PCR is achievable. Thermal cross-talk of as less as 0.2% is obtained with the very thin PCB substrate (500 μm, FR4) and the plastic chip (100 μm PET), in a standard format of multi-chamber array. A temperature fluctuation of ±0.1 °C has been achieved during thermal multiplexing of up to 16 chambers, with each chamber consuming an average heating power of no more than 1.2 W. Finite element analysis (FEA) is conducted to optimise the thermal performance of the cycler. Experiments are in well agreements with the simulations.

A Surface Mount Amplifier-Shaper-Discriminator and Preamplifier for the Fermilab CDF Tracking Chambers

A custom monolithic common base preamplifier chip was designed for Fermilab's Colliding Detector Facility Vertex Time Projection Chamber. The chip contains 4 preamplifiers on a single substrate. All of the associated circuitry as well as the preamplifiers are surface mounted on a thin printed circuit board to reduce the mass of the circuit. A low mass circuit is essential to reduce unwanted particle interactions with the circuit which could interfere with the physics seen by other layers of detectors. The Amplifier-Shaper-Discriminator (ASD) following the wire preamplifier was designed for use with several of the CDF Central Detector tracking chambers. Surface mount components are used extensively on the ASD's to reduce the number of circuit cards and number of crates in the system. Both the new preamplifier and the large scale use of surface mounted components reported in this paper are expected to find wide spread use in new detector electronics.