Printed Circuit Board Fabrication Process Research Articles

무선랜 중계기용 다층 PCB 구조의 평판형 무지향성 이중공진 안테나

In recent years, efforts have been made to replace rod-shaped monopole antennas with planar antennas exhibiting an omnidirectional radiation pattern. In this paper, we describe the design, fabrication, and testing procedures of a dual-band planar antenna that can replace a monopole antenna used in wireless local area network (LAN) routers. The proposed antenna consists of a square metal patch, square ring, and shorting vias on a multilayer printed circuit board to induce 2.4 GHz and 5 GHz dual-band resonance and omnidirectional radiation patterns. The antenna design is optimized using a 3D full-wave simulation software, and an antenna sample is prepared using the printed circuit board fabrication process. The antenna sample is tuned using a copper tape to resolve the operation frequency mismatch, and its performance is tested using a network analyzer and an anechoic chamber. Furthermore, the antenna sample is installed in a commercial wireless LAN router, and its signal reception is analyzed in an actual wireless communication environment to verify its applicability.

The OpenPicoAmp-100K, an Open-source High Performance Amplifier for Single Channel Recording in Planar Lipid Bilayers

We propose an upgraded version of our previously designed open-source lipid bilayer amplifier. This improved amplifier is now suitable both for the use in introductory courses in biophysics and neurosciences at the undergraduate level and for scientific research. Similar to its predecessor, the OpenPicoAmp-100k is designed using the common lithographic printed circuit board fabrication process and off-the-shelf electronic components. It consists of the high-speed headstage, followed by voltage-gain amplifier with built-in 6-order Bessel filter. The amplifier has a bandwidth of 100 kHz in the presence of 100 pF input membrane capacitance and is capable of measuring ion channel current with amplitudes from sub-pA and up to ±4 nA. At the full bandwidth and with a 1 GΩ transimpedance gain, the amplifier shows 12 pArms noise with an open input and 112 pArms noise in the presence of 100 pF input capacitance, while at the 5 kHz bandwidth (typical in single-channel experiments) noise amounts to 0.45 pArms and 2.11 pArms, respectively. Using an optocoupler circuit producing TTL-controlled current impulses and using 50% threshold analysis we show that at full bandwidth the amplifier has deadtimes of 3.5 µs and 5 µs at signal-to-noise ratios(SNR) of 9 and 1.7, respectively. Near 100% of true current impulses longer than 5 µs and 6.6 µs are detected at these two respective SNRs, while false event detection rate remains acceptably low. The wide bandwidth of the amplifier was confirmed in bilayer experiments with alamethicin, for which open ion channel current events shorter that 10 µs could be resolved.

The OpenPicoAmp-100k: an open-source high-performance amplifier for single channel recording in planar lipid bilayers.

We propose an upgraded version of our previously designed open-source lipid bilayer amplifier. This improved amplifier is now suitable both for the use in introductory courses in biophysics and neurosciences at the undergraduate level and for scientific research. Similar to its predecessor, the OpenPicoAmp-100k is designed using the common lithographic printed circuit board fabrication process and off-the-shelf electronic components. It consists of the high-speed headstage, followed by voltage-gain amplifier with built-in 6-order Bessel filter. The amplifier has a bandwidth of 100 kHz in the presence of 100-pF input membrane capacitance and is capable of measuring ion channel current with amplitudes from sub-pA and up to ± 4 nA. At the full bandwidth and with a 1 GΩ transimpedance gain, the amplifier shows 12 pArms noise with an open input and 112 pArms noise in the presence of 100-pF input capacitance, while at the 5-kHz bandwidth (typical in single-channel experiments), noise amounts to 0.45 pArms and 2.11 pArms, respectively. Using an optocoupler circuit producing TTL-controlled current impulses and using 50% threshold analysis, we show that at full bandwidth, the amplifier has deadtimes of 3.5 μs and 5 μs at signal-to-noise ratios (SNR) of 9 and 1.7, respectively. Near 100% of true current impulses longer than 5 μs and 6.6 μs are detected at these two respective SNRs, while false event detection rate remains acceptably low. The wide bandwidth of the amplifier was confirmed in bilayer experiments with alamethicin, for which open ion channel current events shorter that 10 μs could be resolved.

Demonstration of waferscale voltage amplifier and electrostatic quadrupole focusing array for compact linear accelerators

Compact linear accelerators, with beam energies in the kiloelectron volt to megaelectron volt range, have applications in medicine, neutron/X-ray generation, surface modifications, etc. The size, weight, and power of existing accelerators preclude them from mass availability in portable formats. This paper presents a specific implementation of an ion accelerator architecture based on planar wafers with accelerating and focusing sections. Our low cost approach allows the control of the final ion beam energy with potential applications, for example, for accelerator-based ion implantation. In this paper, we demonstrate two important waferscale modules required to build a linear particle accelerator; these include (1) on-wafer voltage amplification for beam acceleration using Inductor-Capacitor (LC) resonators and (2) waferscale electrostatic quadrupole arrays (ESQA) to refocus the ion beams during transport. On-board LC resonators were developed using Printed Circuit Board fabrication processes to implement an LC element resonant at ∼16.6 MHz with a quality factor of 25. An energy gain of ∼250 eV was observed using a two wafer acceleration unit with an argon ion beam with 6.5 keV initial energy. A 3 × 3 ESQA was fabricated on a glass wafer with metal electrodes formed by depositing copper metal around the beam apertures. The ESQA was used to focus and defocus an argon ion beam, demonstrating a field gradient of ∼500 V over a gap of ∼250 μm.

Ku/Ka Dual-Band Dual-Polarized Shared-Aperture Beam-Scanning Antenna Array With High Isolation

This paper describes the design and realization of a Ku/Ka dual-band shared-aperture beam-scanning antenna array based on the concept of structure reuse. The antenna consists of four Ku-band linear antenna arrays implemented by the substrate-integrated waveguide (SIW) and four Ka-band linear antenna arrays. To increase the aperture utilization efficiency, the Ku-band antenna is employed as some sidewalls of the Ka-band antenna. Thanks to this compact topology, the element spacing at two frequency bands is able to meet the requirement of a wide-angle beam scan. Both feeding networks of these two arrays are designed by proper SIW power dividers through the printed circuit board fabrication process. In addition, the self-filtering characteristic of the antenna, the orthogonal polarization, and the optimal layout of the array are employed to ensure the high channel isolation between the two antennas operating at different frequency bands over the whole beam scan range. The isolation between antennas is better than 28 and 70 dB at the Ku-band and Ka-band, respectively, scanning up to even 40°. The proposed shared-aperture concept and the design results have been validated by the experimental results.

A Novel Microfluidic Point-of-Care Biosensor System on Printed Circuit Board for Cytokine Detection.

Point of Care (PoC) diagnostics have been the subject of considerable research over the last few decades driven by the pressure to detect diseases quickly and effectively and reduce healthcare costs. Herein, we demonstrate a novel, fully integrated, microfluidic amperometric enzyme-linked immunosorbent assay (ELISA) prototype using a commercial interferon gamma release assay (IGRA) as a model antibody binding system. Microfluidic assay chemistry was engineered to take place on Au-plated electrodes within an assay cell on a printed circuit board (PCB)-based biosensor system. The assay cell is linked to an electrochemical reporter cell comprising microfluidic architecture, Au working and counter electrodes and a Ag/AgCl reference electrode, all manufactured exclusively via standard commercial PCB fabrication processes. Assay chemistry has been optimised for microfluidic diffusion kinetics to function under continual flow. We characterised the electrode integrity of the developed platforms with reference to biological sampling and buffer composition and subsequently we demonstrated concentration-dependent measurements of H2O2 depletion as resolved by existing FDA-validated ELISA kits. Finally, we validated the assay technology in both buffer and serum and demonstrate limits of detection comparable to high-end commercial systems with the addition of full microfluidic assay architecture capable of returning diagnostic analyses in approximately eight minutes.

A Low-Loss Fully Board-Integrated Low-Pass Filter Using Suspended Integrated Strip-Line Technology

This paper presents a low-loss fully board-integrated low-pass filter (LPF) using suspended integrated strip-line (SISL) technology. A multilayer board stack-up, with internally buried hollow cavities, is used to create the suspended strip-line. By transitioning from the top copper ground-backed coplanar waveguide trace to an internal strip-line and vice versa, a more traditional industry-standard utilization of the top copper can be realized with this SISL implementation. Based on the proposed design, an 11th-order generalized Chebyshev LPF, with a cutoff frequency of 18 GHz, has been designed and fabricated using standard printed circuit board fabrication processes. Compensated measured results show less than 1 dB of attenuation over the dc-18-GHz passband and greater than 30 dB of stopband attenuation up to 26 GHz. The proposed SISL technology LPF has advantages of low loss, compact size, and low cost, which are crucial to meet unprecedented reductions in size, weight, power, and cost (SWaP-C) of future systems.

Design and Performance of a High- $Q$ Narrow Bandwidth Bandpass Filter in Empty Substrate Integrated Coaxial Line at $K_{u}$ -Band

This letter presents the design and performance of a planar narrow bandwidth bandpass filter with high quality factor. The structure is composed of an empty substrate integrated coaxial line with the center conductor suspended in air. The component dimensions have been calculated by means of classical microwave filter design theory. The filter has been manufactured using standard printed circuit board fabrication processes. A measured insertion loss of 1.59 dB, 2.93% fractional bandwidth, and a $Q$ -factor of 1505 have been obtained at 15 GHz. A $Q$ -factor comparison with other substrate and empty substrate integrated technologies shows the advantages of the solution considered in this letter. The proposed filter proves to be suitable for the implementation of integrated microwave or millimeter-wave subsystems with severe restrictions, i.e., low in-band losses, very narrow bandpass responses, low frequency dispersion, high out-of-band rejection, and low manufacturing cost.

3D Metamorphic Stretchable Microphone Arrays

AbstractThis article describes the realization of a metamorphic microphone array. The array morphs from a concave to a planar and then to a convex shape. The morphing array enables a better (12×) sound source localization when compared to existing static and planar arrangements. To enable the realization, a novel stretchable (elongated up to 320% of the original length) printed circuit board fabrication process is reported. The fabrication process enables high‐temperature processing, alignment, and registration. Moreover, conventional and otherwise rigid surface mount devices (SMDs) can be used. The process allows the researcher to increase the number of devices (30 SMDs) and interconnects (60 in total) to the required level. As electrical connections, a polyimide‐cladded metal track design is reported; the design sustained 11 050 stretch and release cycles. Moreover, 3D reinforcement frames are reported as an effective measure to shield the SMD components from high levels of stress. The resulting products are millimeter‐thin stretchable rubber‐embedded and electrically interconnected electronic structures with mechanical rubber‐membrane‐like properties. Morphology changes involve deflation and inflation of the membrane to bulge inward or outward. Finally, the use of 3D‐shaped chaperon is discussed to provide additional shape control.

Design of a 75-140 GHz high-pass printed circuit board dichroic filter.

A new high-performing PCB (Printed Circuit Board) dichroic filter, which can be used for the KSTAR (Korea Superconducting Tokamak Advanced Research) electron cyclotron emission imaging system, is proposed. The current dichroic filter consists of a triangular lattice array of circular holes on the 6-mm thick metal plate, while circular hole spacing limitation caused relatively narrow passband (∼20 GHz). On the other hand, the proposed PCB dichroic filter utilizes the inexpensive commercial PCB fabrication process with a flexible adjustment of circular hole spacing. Therefore, the proposed PCB dichroic filter provides significantly wider passband (∼60 GHz with 0.84 dB insertion loss) with much reduced weight and expense. Also, it is shown that a steep skirt property can be obtained with the thick PCB filter substrate. The design process, fabrication, and measurement results of the new PCB dichroic filter are described.

A Comparison of Immersion Gold and Tin Surface Finishes on Sensing Electrodes for PCB Environmental Saltwater Concentration Sensors

Abstract Printed circuit board (PCB) sensors using low-cost commercial printed circuit board fabrication processes have been demonstrated for environmental sensing applications. One configuration of these sensors uses exposed electrodes to measure saltwater concentration in freshwater/seawater mixtures, through monitoring the resistance between the electrodes when they are immersed in the saltwater/freshwater solution. The lowest cost commercial PCB processes use an immersion Sn HASL surface finish on exposed copper cladding, including the sensing electrodes. This commercial PCB process has been demonstrated to make an effective, low-cost, short-lifetime sensor for saltwater concentration testing. The Sn finish, however, may not be optimal for this application. Sn oxidizes, which can interfere with sensor performance. Additionally, Sn and Sn oxides are potentially reactive with chemical constituents in seawater and seawater/freshwater solutions. An immersion Au (ENIG) surface finish is certainly less reactive with the atmosphere and chemicals likely present in the testing environment. However, an immersion Au finish increases the cost of the sensors by 30% to 40%. To investigate if the possible benefits of the more expensive Au surface finish are worth the extra expense, a study was performed where identical PCB sensors were procured from a commercial vendor with their standard low-cost Sn HASL finish and with their standard ENIG surface finish. Both sets of sensors were then evaluated in concentrations of seawater and freshwater, from 0% to 100% seawater concentration, using freshwater samples from a natural freshwater source near the coast where the seawater was obtained. Testing demonstrated an insignificant difference in sensor performance between the Sn HASL and the ENIG coated sensing electrodes. The results of this investigation indicated that for applications where the sensors will not be used for long periods of time, the added expense of an immersion Au surface finish is not worth the added cost.

Unequal Wilkinson power divider with wide range of arbitrary power division based on recombinant technology

An arbitrary ratio Wilkinson power divider with large power dividing ratio is analysed and demonstrated in this study. This kind of Wilkinson power divider is constructed by incorporating equal (or unequal) power divider cells, recombinant structures, extra low power branches and transformers for matching the circuits. The proposed structure is compatible with single-layer printed circuit board fabrication process. The structure is analysed in detail, while the formulas are given as design guidelines. Moreover, this method is extended to unequal power dividers based on three-way Wilkinson power divider with larger dividing ratio. To verify the proposed design approach, the prototypes of 5:1, 7:1 and 11:1 unequal power divider are optimised, fabricated and measured. The measured bandwidth of 20 dB return loss are about 10, 10 and 6%, respectively, while the isolations of the output ports are better than 20 dB. Good agreements can be observed between the simulated and measured results. The phase differences of output ports are within ±3° over 10% fractional bandwidth.

Novel Coupled Line 180<formula formulatype="inline"> <tex Notation="TeX">$^{\circ}$</tex></formula> Hybrid With Non-Interspersed Input and Output Ports

This paper presents a novel coupled line 180 ° hybrid with non-interspersed input/output ports. With the combination of a weak coupling parallel coupled line and strong coupling trans-directional coupler, a non-interspersed input/output ports coupled line 180 ° hybrid is obtained by using printed circuit board fabrication process, and reduced substrate area is achieved. The proposed hybrid owns the features of reducing the complexity of dc biasing for the next-stage active circuits. Moreover, it requires no bond wires, via-holes, or multilayer structures. The formula of the proposed hybrid is derived, and the characteristics of the hybrid are analyzed. Two prototypes are designed to verify the concept. One is arranged with the two couplers perpendicular to each other, and the other is constructed with the two couplers arranged in a line. The measured results are in good agreement with the simulated ones.

The OpenPicoAmp: an open-source planar lipid bilayer amplifier for hands-on learning of neuroscience.

Understanding the electrical biophysical properties of the cell membrane can be difficult for neuroscience students as it relies solely on lectures of theoretical models without practical hands on experiments. To address this issue, we developed an open-source lipid bilayer amplifier, the OpenPicoAmp, which is appropriate for use in introductory courses in biophysics or neurosciences at the undergraduate level, dealing with the electrical properties of the cell membrane. The amplifier is designed using the common lithographic printed circuit board fabrication process and off-the-shelf electronic components. In addition, we propose a specific design for experimental chambers allowing the insertion of a commercially available polytetrafluoroethylene film. We provide a complete documentation allowing to build the amplifier and the experimental chamber. The students hand-out giving step-by step instructions to perform a recording is also included. Our experimental setup can be used in basic experiments in which students monitor the bilayer formation by capacitance measurement and record unitary currents produced by ionic channels like gramicidin A dimers. Used in combination with a low-cost data acquisition board this system provides a complete solution for hands-on lessons, therefore improving the effectiveness in teaching basic neurosciences or biophysics.

Battery-operated, portable, and flexible air microplasma generation device for fabrication of microfluidic paper-based analytical devices on demand.

A portable microplasma generation device (MGD) operated in ambient air is introduced for making a microfluidic paper-based analytical device (μPAD) that serves as a primary healthcare platform. By utilizing a printed circuit board fabrication process, a flexible and lightweight MGD can be fabricated within 30 min with ultra low-cost. This MGD can be driven by a portable power supply (less than two pounds), which can be powered using 12 V-batteries or ac-dc converters. This MGD is used to perform maskless patterning of hydrophilic patterns with sub-millimeter spatial resolution on hydrophobic paper substrates with good pattern transfer fidelity. Using this MGD to fabricate μPADs is demonstrated. With a proper design of the MGD electrode geometry, μPADs with 500-μm-wide flow channels can be fabricated within 1 min and with a cost of less than $USD 0.05/device. We then test the μPADs by performing quantitative colorimetric assay tests and establish a calibration curve for detection of glucose and nitrite. The results show a linear response to a glucose assay for 1-50 mM and a nitrite assay for 0.1-5 mM. The low cost, miniaturized, and portable MGD can be used to fabricate μPADs on demand, which is suitable for in-field diagnostic tests. We believe this concept brings impact to the field of biomedical analysis, environmental monitoring, and food safety survey.

An Open-Source Lipid Bilayer Setup for Hands-On Learning of Biophysics

Although people are generally interested in how the brain functions, neuroscience education is hampered by a lack of low cost and engaging teaching materials. To address this, we developed an open-source lipid bilayer amplifier which is appropriate for use in introductory courses in biophysics or neurosciences. The amplifier is designed using the common lithographic printed circuit board fabrication process and off-the-shelf electronic components. In addition, we propose a specific design for experimental chambers allowing the insertion of a commercially available polytetrafluoroethylene film. This device can be used in simple experiments in which students monitor the bilayer formation by capacitance measurement and record unitary currents produced by ionophores like gramicidin A. Used in combination with a low-cost data acquisition board this system provides a complete solution for hands-on lessons, therefore improving the effectiveness in teaching basic neurosciences or biophysics.

Multi-Beam Multi-Layer Leaky-Wave SIW Pillbox Antenna for Millimeter-Wave Applications

This work proposes a novel multi-beam leaky-wave pillbox antenna. The antenna system is based on three main parts: feeding part (integrated horns), quasi-optical system and radiating part. The radiating and input parts are placed in two different stacked substrates connected by an optimized quasi-optical system. In contrast to conventional pillbox antennas, the quasi-optical system is made by a pin-made integrated parabola and several coupling slots whose sizes and positions are used to efficiently transfer the energy coming from the input part to the radiating part. The latter consists of a printed leaky-wave antenna, namely an array of slots etched on the uppermost metal layer. Seven pin-made integrated horns are placed in the focal plane of the integrated parabola to radiate seven beams in the far field. Each part of the antenna structure can be optimized independently, thus facilitating and speeding up the complete antenna design. The antenna concept has been validated by measurements (around 24 GHz) showing a scanning capability over ±30° in azimuth and more than 20° in elevation thanks to the frequency scanning behavior of the leaky-wave radiating part. The proposed antenna is well suited to low-cost printed circuit board fabrication process, and its low profile and compactness make it a very promising solution for applications in the millimeter-wave range.

Enhanced Coupling Structures for Tight Couplers and Wideband Filters

Tightly coupled lines are difficult to realize on the conventional printed circuit board (PCB). This paper proposes two types of novel enhanced coupled-line structures appropriate for tightly coupled directional couplers and wideband filters. The proposed coupled-line structures both have a rectangular ground-plane aperture and two inserted signal strips in the aperture to increase the coupling strength significantly. No fine lines and narrow gaps are required so as to fit the conventional PCB fabrication process. More importantly, the proposed structures only need a single-layer substrate. To demonstrate the feasibility of the proposed structures, one 3-dB directional coupler and two four-pole Chebyshev filters with 0.05-dB equal-ripple bandwidths of 40% and 37% are designed and realized. The coupler and filters are fabricated on a PCB substrate with a dielectric constant of 3.58 and a thickness of 0.508 mm. Good agreement between measurements and simulations is observed.

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.

Development of a Compact Broadband Folded Hybrid Coupler on Multilayer Organic Substrate

We present the design and fabrication of a wide bandwidth folded hybrid coupler on a multilayer organic substrate. The coupler is designed with a tandem connection of two 5-sections with a coupling of 8.34 dB. We propose a novel center coupling structure that achieves tight coupling while being compatible with printed circuit board fabrication processes. The folded coupler achieves a bandwidth of 2 to 18 GHz with 42% reduction in size.