Printed Circuit Board Fabrication Research Articles

Tailored polyphenylene sulfite composite with desirable mechanical performance and low dielectric constant by constructing a controllable aramid fiber network

With an increasingly complex working environment and the growing demand in the electrical equipment market, the performance of high-frequency printed circuit boards (PCBs) is generally inadequate, and this problem is due to the failure of either its material or internal architecture. Thus, state-of-the-art PCBs with robust mechanical performance and a low dielectric constant need to be developed. This study proposes a facile technique to fabricate PCBs by assembling aramid fiber (AF) and polyphenylene sulfide (PPS) by combining papermaking and thermocompression lamination. A PPS nonwoven fabric and AFs were first introduced into deionized water and then subjected to intense shearing to form hybrid paper. AF/PPS composite laminates were then fabricated by thermocompression. The as-prepared AF/PPS-30 wt% sample exhibited a flexural strength of 181.4 MPa and a flexural modulus of 13.1 GPa. The sample also achieved a dielectric constant of 3.3 at 15 kHz to 2 MHz, suggesting that the sample exhibited superior dielectric performance and frequency independency as a high-frequency function attributable to the controllable aramid network structure. The dielectric constants of one-dimensional materials reinforced polymer composites were also studied theoretically, and the results presented using the Bruggeman model were consistent with the experimental values. This study provides a feasible strategy for the fabrication of extraordinary PCBs to achieve both desirable mechanical performance and low dielectric constant.

Dielectric Loss Tangent Extraction Using Modal Measurements and 2-D Cross-Sectional Analysis for Multilayer PCBs

Frequency-dependent electrical properties of dielectric materials are one of the most important factors for high-speed signal integrity design. To accurately characterize material's dielectric loss tangent (tanδ) after multilayer printed circuit board fabrication a novel method was proposed recently to extract tanδ using coupled striplines' measured S-parameters and cross-section geometry. By relating modal attenuation factors to the ratio between the differential and common mode per-unit-length resistances, the surface roughness contribution is eliminated and the contributions of dielectric and conductor loss are separated. Here, we specifically decided to avoid using any physical dielectric model in the extraction algorithm in order to eliminate a need for any a priori information about dielectric behavior. Further analysis and improvement of the tanδ extraction approach is presented in this article. To evaluate the accuracy of the extraction, the impact of errors due to de-embedding, vector network analyzer measurement, and two-dimensional solver's calculation are taken into account by a statistical error model. A confidence interval of extracted tanδ is provided. To describe the frequency dependence of tanδ, a two-term Djordjevic model is proposed to fit the extracted tanδ curve, which guarantees causality and gives better agreement with measured insertion loss compared to the traditional Djordjevic model.

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.

Fabrication of Copper Circuit Pattern By Using Solid-Electrodeposition Process

Recently, automotive industry faces to revolution originated from the concept of Connected, Autonomous, Shared and Electric (CASE). For future society, it is noted that electric devices should be increasingly important components because a large number of the devices is indispensable to put CASE in practice. In electric devices, printed circuit boards (PCBs) are particularly key materials, which require further high density wiring as well as cost reduction. The fine patterned PCBs is often fabricated by semi-additive process. However, it is not easy to achieve finer pattering, owing to limitation of photolithographic resolution as well as residual palladium and/or copper metal in etching area. Regarding with the fabrication cost, the drastic reduction cannot be expected without changing process flow because semi-additive process is one of the mature technologies. In addition to that, the exhaust water generated from developing, electroplating, etching and rinsing processes causes serious environmental issues on nature, almost all of which are related to masking and electro/electroless plating processes. Therefore, it is urgently necessary for CASE to develop simple process without masking and conventional plating. We have developed novel electrodeposition process named solid electrodeposition (SED) which is characterized with metal ion electrophoresis through solid electrolyte membrane. The present SED apparatus is shown in Fig. 1. The head part composed of anode electrode, metal solution and the membrane is settled on the tip of press apparatus. The head part contacts with substrate under constant pressure and then a voltage is applied between anode electrode and cathode substrate. The metal deposition proceeds on solid-solid interface between membrane and substrate. It is important to note that cation exchangeable polyelectrolyte is used for membrane, i.e., metal ion can diffuse through ion-exchange reaction. When this system is accumulated into small probe system, this process enables electrodeposition of metals only by attaching the membrane surface into the substrate in a serial patterning manner. Moreover, SED has a merit of relatively high deposition rate, which is characterized with effective mass transfer mechanism of metal ion into membrane. We believe that SED can be highly potential process to dissolve not only the cost but also the environmental issues for current fabrication process of electronic elements. In the current study, we report on the fabrication of PCBs by using SED process. Although SED process can apply for selective deposition, an area of which depends on contact area of membrane used for deposition, it is difficult to match membrane size with fine patterns. Therefore, the patterned seed layer is printed on the substrate before SED process. The deposited copper patterns completely reflect underlying seed patterns without widening metal lines. This is because copper predominantly deposits along height direction, presumably due to selective growth of copper at solid interface. In this contribution, we will report the characteristics of SED process and novel process to fabricate circuit patterns without using masking and rinsing process. Figure 1

Electroless Copper Deposition Using Complexed Copper(II) Ion As Catalyst for Printed Circuit Board Fabrication

Electroless (ELS) copper plating process has been commonly used for printed circuit board (PCB) metallization. The traditional ELS copper plating process uses tin/palladium colloid or complexed palladium ion as catalysts for ELS copper deposition. But the price of palladium catalyst is much higher than that of gold. Herein, we use complexed copper(II) ion to replace the palladium catalyst in order to greatly reduce the process cost but maintain the performance and the reliability of the complexed copper(II) ion as good as palladium. The synthesis process of the complexed copper ion is simple and its cost, which compared with palladium, is cheap. Especially, they have no oxidation issue because they are not metallic copper nanoparticles but copper(II) ions. Before ELS copper plating, the grafted copper(II) ion that is chemically adsorbed onto the substrate surface is reduced to copper atom, so they can catalyze ELS copper deposition. In this work, we optimize the experimental parameters such as operating temperature, reaction time, copper ion concentration and the pH of the plating solution. After ELS plating process, the backlight test of through holes (THs) of a PCB and the morphology of the ELS copper deposited onto the sidewalls of the THs are evaluated by optical microscope (OM) and scanning electron microscope (SEM), respectively. The thermal reliability of the ELS copper deposition catalyzed by the grafted copper catalyst was examined after copper electroplating using thermal shock in a tin bath at 288℃ for ten seconds and repeated it for 5 times. Results show that it can pass the thermal shock test. Therefore, the application of complexed copper(II) ion as the catalyst of ELS copper plating is expected to replace the expensive palladium for PCB fabrication.

Computational Modeling of Copper Deposition in through Silicon Via Structures

Copper electrodeposition is critical to integrated circuit manufacturing, ranging in scale from nanometer features in damascene plating to micrometer scale through-silicon via structures and even millimeter scale printed circuit board fabrication. Essential to this technology is electrodeposition of void-free copper in high aspect ratio cavities, which is achieved through various additives that enable bottom-up filling. In through-silicon-via structures, void-free filling can be realized with micro-to-milli molar concentrations of polyether suppressor and chloride additives. A variety of analytical measurements have shown chloride adsorption on copper is a necessary precursor to formation of a polyether blocking layer to suppress deposition. In this study, experimental measurements and computational models are presented exploring the dynamics of polyether and chloride adsorption during copper deposition. Microelectrode measurements eliminate solution iR effects, while demonstrating comparable results to rotating disk electrode systems at equivalent transport conditions. A two-additive co-adsorption model for polyether and chloride is presented, comparing simulations to experimental feature filling at conditions when chloride transport is limiting formation of the inhibiting ad-layer (< 80 μmol/L). Suppression breakdown is related to the local polyether coverage, which is in turn limited by the chloride coverage on the depositing interface. A passive-active transition of copper deposition is associated with limited flux of chloride in the feature. At higher chloride concentrations (≥ 80 μmol/L), sidewall breakdown during deposition occurs nearer to the bottom of the via, followed by a shift to bottom-up growth.

The ZOG Method: True Printed Circuit Boards

Printed circuit board (PCB) fabrication is a time-consuming process that uses dangerous and tedious subtractive methods such as milling, chemical etching, or laser etching. The Zhou–Oyama–Garmire (ZOG) method is introduced as an alternative to the traditional PCB fabrication. This nontoxic, inexpensive method results in packaged, sealed circuitry and allows a wide range of users to iterate prototypes quickly. Traces are 3-D printed, and liquid metal is deposited onto the traces with a brush and sacrificial layer. Electrical components are placed on the traces, and pin headers are inserted to interface with the circuit. The circuit board is sealed with a thin layer of the thermoplastic polymer. To illustrate, an instrumentation amplifier circuit was fabricated using this method and yielded a gain of 106 with a 3.64% error. The ZOG method provides advantages over the traditional PCB fabrication in terms of cost, safety, recyclability, ease of fabrication, and robustness.

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 PCB Sensor for Magnetic Materials

Printed circuit board (PCB) sensors are a sensor technology where the layout of traces on a PCB has been optimized so that the traces electromagnetically interact with the surrounding environment. These types of sensors can be manufactured at very low cost using standard commercially available low-cost printed circuit board fabrication. Exposed conductive electrodes on the circuit board are useful for measuring the electrical conductivity of the surrounding environment, and these sensors have been used in applications such as salinity measurement and dissolved ion content measurement of aqueous solutions. Insulated interdigitated electrode sensors are useful for capacitively analyzing the surrounding environment, and these sensors have been used to detect the presence of liquid water and to measure the moisture content of substances in physical contact with the sensor. Additionally, by measuring the complex impedance of the capacitive sensor over a wide frequency range, information concerning the chemical composition of the substance in contact with the sensor can be determined. In addition to conducive and capacitive PCB sensors, the third type of PCB sensor would be an inductive sensor. Although it is challenging to realize 3D coils in PCB technology, planar inductors can be realized in a single Cu layer on a PCB, and insulated from the environment using a cover layer of polymeric solder mask. This type of electrode structure can inductively couple with magnetic materials in close proximity to the sensor. A variety of magnetic materials exist, including iron, nickel and cobalt. Additionally, many alloys of these elements are also magnetic. Of particular interest are corrosion products with magnetic properties, such as iron(III) oxide, Fe3O2, also known as common rust. A thin layer of iron(III) oxide powder deposited on the sensor's active area results in a measureable increase in the sensor's inductance. As such, an inductive PCB sensor could be a low-cost option for detecting the presence of some corrosion products in its operating environment.

A new and improved electric fish finder with resources for printed circuit board fabrication

ABSTRACT We describe the circuit design, construction, and operation of a field-portable electric fish finder (an AC-coupled wide-band differential bio-amplifier with loudspeaker output). This device permits detection and monitoring of the electric organ discharges generated by neotropical gymnotiform fishes (as well as the mormyroid fishes of tropical Africa). Our design is modified from earlier versions to optimize detection performance and stability over a wider range of ambient water conductivity, including under conditions of extremely low conductivity (&lt; ca. 10 μScm-1). Our new electric fish finder design also incorporates complete waterproofing and longer battery autonomy. We provide Gerber and Eagle files made with the electronic design automation software ‘Autodesk Eagle’ to allow researchers to order printed circuit boards directly from commercial manufacturers.

Wide Solid Angle Beam-Switching Conical Conformal Array Antenna With High Gain for 5G Applications

This letter presents a design for three-dimensional polymeride printing, printed circuit board fabrication, and a full experimental verification of a conical conformal array antenna (CCAA) with wide solid angle switching beam by a radio frequency semiconductor switch (RFSS) configuration. The CCAA consists of eight linear array antennas (LAAs) with uniform circumferential arrangement around a conical surface. Only one LAA out of the eight arrays is individually excited, operating each time by the RFSS connected to the ports of 1–8 power dividers in order to achieve the requirement of beam switching. The CCAA with beam-switching feeding network operates at 4.8 GHz according to the fifth-generation (5G) band requirements. Both a wide solid scanning angle of 0°–218° in the H-plane and a half-power bandwidth less than 16° in the E-plane are achieved. When the realized gain of each LLA is over 10 dBi, the measured peak gain of the final antenna can reach about over 11 dBi and the average radiation efficiency can reach 59.5%. This CCAA with wide solid angle beam switching and high-gain property has the potential to reduce the signal-to-noise ratio and integrate with 5G communication systems.

Planar Broadband Huygens’ Metasurfaces for Wave Manipulations

Electrically thin and effectively 2-D material composites, metasurfaces, have been widely exploited for the manipulation of electromagnetic waves. For many applications, it is desired to transform incident waves of a specific frequency range keeping the metasurface invisible at other frequencies. Such a frequency-selective response can be achieved based on subwavelength Huygens’ inclusions. However, their fabrication requires sophisticated processes due to the 3-D geometry. Here, we propose a planar Huygens’ meta-atom with the goal to open a way to realize broadband invisible metasurfaces with topologies suitable for the conventional printed circuit board fabrication technology. We synthesize and analyze, both numerically and experimentally, three different metasurfaces capable of polarization and amplitude transformations of incident waves.

A Low-Profile Coplanar Dual-Polarized and Dual-Band Base Station Antenna Array

This paper presents a low-profile coplanar dual-polarized dual-band base station antenna array. A slotted patch antenna operating from 0.82 to 0.99 GHz with four shorting strips is proposed and analyzed. The four shorting strips are employed not only to improve the impedance matching in the lower band but also to remove the center part of the patch, thus making room for higher band dipoles operating from 1.68 to 2.86 GHz. The height of the proposed array is nearly half of the conventional base station array while other performances are guaranteed. The measured results show that the proposed antenna array has wide impedance bandwidths of 18.7% (0.82–0.99 GHz) and 57.9% (1.68–2.86 GHz) (VSWR $0.109\lambda _{0}$ at 820 MHz). The measured gains are 13.8±0.5 dB and 16.7 ± 1 dB in lower and upper bands. Large front-to-back ratio (>24.6 dB) and high isolations (>30 and >25 dB in lower and upper bands, respectively) are achieved. The proposed antenna can be easily built with printed circuit board fabrication technique and applied in low profile multiband base stations for 2G/3G/4G and the next-generation systems.

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.

A 60 GHz phased array with measurement and de-embedding techniques

We present a 60 GHz phased array system that combines several key technologies to realize 10 GHz bandwidth coverage. Particularly, a tightly coupled dipole array centered at 60 GHz is designed and tested for its wideband performance. The tightly coupled dipole elements offer excellent wideband behavior of 10 GHz with voltage standing wave ratio < 3 with scanning to 45°, as well as low cost printed circuit board fabrication. Additionally, we demonstrate a measurement setup with de-embedding procedure to measure gain at the antenna feed point. A feeding structure was designed and fabricated for de-embedding gain pattern measurements. Recovered measurements are shown to be in agreement with simulation.

Design and Implementation of CNC Milling Bot for Milled Circuit Board Fabrication

This research paper presents an alternative way to fabricate a Milled Circuit Board (MCB) with the help of a Computer Numerical Controlled (CNC) milling robot. Printed Circuit Boards (PCB) are one of the most widely used control modules in electrical and electronic industries. In this research paper we propose a computer controlled milling machine which can be used for quick fabrication of double layered PCBs called MCB where a user wants to test the circuit without the need to wait for the conventional PCB fabrication. The end effector of the CNC milling machine has the provision to move in 3 axes-x, y and z in accordance with the input received from the controller. DipTrace, an EDA/CAD software is used for creating the schematic diagram for the milled circuit boards. The design to be engraved on the copper clad board is uploaded to a software called CopperCam, where it can be converted to G-code files after making the necessary modifications. These G-code files are then uploaded to the CNC machine using the software Universal G-code Sender, thus enabling the microcontroller to direct the rotation of motors and coordinate the movements of the end effector so as to engrave the board design on to a copper clad.

Body-Worn 30:1 Bandwidth Tightly Coupled Dipole Array on Conductive Textiles

We present a novel tightly coupled dipole array (TCDA) based on conductive textiles (E-threads) that achieves 30:1 bandwidth across the 60–2000 MHz frequency range (VSWR < 4). The proposed antenna occupies 1.4 m in length and 0.05 m in width and consists of three overlapping dipoles that are fed in phase to ensure uniform current flow. Two fabricated prototypes are presented in this letter. The first is a rigid metallic version using a 1.524 mm thick Rogers RO4003 board via conventional printed circuit board fabrication. The other is a fully flexible textile-based prototype “printed” on organza fabric via automated embroidery of conductive threads (E-threads). In both cases, measurements are in very good agreement with simulations. Specifically, the TCDA is well matched from 500 to 2000 MHz with VSWR < 2.5 and has a realized gain ranging from −16 to 6 dBi across the entire bandwidth from 60 to 2000 MHz. The proposed design is intended for on-body operation (e.g., placed along the arms). To assess the performance of this antenna for body mounting, we applied a 2 cmthick ground beef beneath the textile TCDA to represent the body tissue. Overall, the proposed TCDA brings forward new opportunities for several ultrawideband applications.