Printed Circuit Board Process Research Articles

Design of Low-Cost Full W-Band 8th Harmonic Mixers for Frequency Extension of Spectrum Analyzer

High-order harmonic mixer is popular for frequency extension of spectrum analyzer (SA) from microwave to millimeter-wave or even terahertz band. The manufactures of SA usually offer expensive harmonic mixers where frequency extension is needed. In this work, low-cost designs of 2-port and 3-port W-band 8th harmonic mixers covering 75–110 GHz are proposed, and design method of two port mixer without frequency diplexer to separate local oscillator (LO) and intermediate frequency (IF) signals are first presented. These two kinds of mixers are compatible with almost all the current SAs with frequency extension options, which provides LO for the external harmonic mixer. The mixers are designed with planar microstrip lines and antiparallel Schottky diodes. The circuit of 2-port mixer includes the input broadband bandpass filter, diodes, output lowpass filter, and matching circuits. As for 3-port mixer, only an extra diplexer is needed to separate the IF signal and LO signal. The diplexer is composed of a planar semi-lumped lowpass and a highpass filter. The planar circuits are easily fabricated with low-cost print circuit board process on polytetrafluoroethylene substrate. The measured conversion loss of 2-port 8th harmonic mixer is from 20 to 26 dB, and 23 to 28 dB for 3-port mixer at full W-band. The good measured results indicate the proposed mixers are simple and effective.

A Design of Bare Printed Circuit Board Defect Detection System Based on YOLOv8

As electronic products develop towards miniaturization and digitization, printed circuit boards (PCBs) also develop towards high density and high precision. In the manufacturing process of PCBs, some PCBs with defects will be produced, and these defects often lead to circuit failure, so defect detection technology is an indispensable part of PCB manufacturing technology. Aiming at the problems of low efficiency and accuracy of traditional image recognition and classification technology, A PCB defect detection algorithm is proposed based on YOLOv8 in this paper. For these five PCB defects, the neural network in deep learning was used to identify and classify PCB defects. The prediction accuracy of YOLOv8 model after training is close to 97%, and it is compared with the accuracy of other algorithms to prove the effectiveness and feasibility of the model. In addition, the object detection image user interface is also established in this paper, which can realize image detection more conveniently.

Oblique incidence-insensitive metamaterial absorber using strong magnetic coupling resonance for low-frequency microwave absorption

In this work, we presented an oblique incidence-insensitive metamaterial absorber (MA) based on the strong magnetic coupling resonance using the printed circuit board process, and the spacer is produced by a typical magnetic absorber material (MAM). As for reflection loss (RL) at oblique angles, it can achieve high-efficiency absorption for both transverse-electric (TE) and transverse-magnetic (TM) polarizations with a wide angular range from 0° to 60° in the low frequency of 2.33 GHz to 3.44 GHz. In addition, the magnetic coupling mechanism of the metamaterial absorber was deeply analyzed. Comparing the results of the simulation and experiment, it displays excellent absorption performance of the proposed absorber in TE and TM modes under large oblique incidence angles.

A low‐profile planar end‐fire broadband antenna with wide beamwidth

AbstractA low‐profile planar end‐fire broadband antenna with wide beamwidth is presented. The proposed antenna consists of a grounded coplanar waveguide (GCPW), an antipodal dipole, and a pair of directors. A transition from the GCPW to the substrate integrated waveguide (SIW) with tapered coupling slots is designed to achieve a wide impedance bandwidth. Wide beamwidths of the proposed antenna are realised through the antipodal dipole with bilaterally symmetrical sector arms. A pair of directors are symmetrically located on both sides of the sector arms to further widen the beamwidth. An antenna prototype operating at Ka band with a size of 2.18 λ0 × 0.77 λ0 × 0.06 λ0 (λ0 is the wavelength of the centre frequency) is fabricated based on the conventional printed circuit board process. The measurement results show that the reflection coefficient is lower than −12.5 dB in the frequency range of 32.2–37.0 GHz. At 35.5 GHz, the peak gain is 3.8 dBi, and the half‐power beamwidths (HPBWs) in E‐plane and H‐plane are 116° and 215°, respectively.

A sprayed graphene transistor platform for rapid and low-cost chemical sensing.

We demonstrate a novel and versatile sensing platform, based on electrolyte-gated graphene field-effect transistors, for easy, low-cost and scalable production of chemical sensor test strips. The Lab-on-PCB platform is enabled by low-boiling, low-surface-tension sprayable graphene ink deposited on a substrate manufactured using a commercial printed circuit board process. We demonstrate the versatility of the platform by sensing pH and Na+ concentrations in an aqueous solution, achieving a sensitivity of 143 ± 4 μA per pH and 131 ± 5 μA per log10Na+, respectively, in line with state-of-the-art graphene chemical sensing performance.

Low-Profile Dual-Wideband Dual-Polarized Antenna for 5G Millimeter-Wave Communications

This letter presents a dual-wideband dual-polarized antenna that fully covers the fifth-generation (5G) millimeter-wave (mm-wave) bands of n257−n261 (24.25–29.5 GHz and 37–43.5 GHz), and that shows a low-profile feature and a band-stop filtering response. For each polarization, the low-band and high-band radiation modes are, respectively, achieved by the two pairs of U-shaped dipole arms which are distributed along the co- and cross-polarized directions. Meanwhile, a radiation null is generated by the radiating cancellation effect of the two pairs of dipole arms, suppressing the unwanted frequency between the two operating bands. Moreover, an extra high-band resonant mode is introduced by the parasitic patches, enhancing the bandwidth of the proposed antenna. Furthermore, a vertical balun structure connecting each dipole arm with the ground is bent to reduce the antenna profile. In the fabrication, high-density interconnect printed circuit board process is employed to meet the antenna-in-package consideration. Under the constrained substrate thickness of 1 mm, the proposed antenna achieves a dual-wideband operation of 24–30 GHz (22%) and 37–43.5 GHz (16%). These merits make the proposed antenna suitable for 5G mm-wave communications.

Ultrathin High-Gain D-Band Transmitarray Based on a Spatial Filter Topology Utilizing Bonding Layer Effect

This letter presents an ultrathin transmitarray (TA) in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> -band (110–170 GHz) by utilizing the bonding layer effect of spatial filters. The standard printed circuit board process limits the performance of spatial filters, resulting in a poor phase-shifting range in the sub-terahertz. The proposed unit cells based on the frequency selective surfaces use only two substrates to be ultrathin. By attaching the additional metal layer on the other side of the bonding substrate, the bonding layer effect can be maximized. Consequently, the proposed unit cells achieved a 271° phase-shifting range without any additional substrates. The proposed TA is the first to attain a high gain of more than 40 dBi in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> -band by reducing the quantization loss. The TA is synthesized using ten types of unit cells that have a low insertion loss of less than 1.5 dB. A 25.5 dBi horn antenna was selected as the source. The focal-to-diameter ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> ) ratio is 1.686 for the TA. The proposed TA, which is comprised of 50 176 elements, attains a peak gain of 44.3 dBi, an efficiency of 24.1%, and a bandwidth of 6% (134.5–143.5 GHz).

A dielectric resonator bandpass filter using printed circuit board technology for wideband application

A dual-mode dielectric resonator based on printed circuit board (PCB) technology formed bandpass filter is proposed for relatively wide bandwidth under low quality factor. By using the low dielectric constant substrate itself to become the core part of the two coupled dual-mode resonators through the PCB process, the proposed design can share the same substrate with other PCB circuits and reduce the installation error. Moreover, benefiting from the dual-mode ( TE 111 y mode and TM 111 z mode) resonator realized by low dielectric constant substrate with low quality factor, the proposed design exhibits the features of low cost and wide bandwidth. A prototype with the center frequency (f0) of 13.85 GHz was demonstrated, which shows the 3-dB fractional bandwidth of 8.34% and the minimum insertion loss of 1.29 dB.

Cooling chip on PCB by embedded active microchannel heat sink

The use of chips is inseparable from printed circuit board (PCB), therefore, it is an effective way to realize microchannel heat sink (MCHS) on PCB to actively cool chip. For improving the integration and cooling efficiency, and reducing the size, energy consumption and coolant consumption of cooling system for thermal management of chips on PCB, the principle and structure of cooling chip on PCB by embedded active microchannel heat sink (EAMCHS) are proposed. EAMCHS is formed by simultaneously integrating MCHS, diffuser/nozzle piezoelectric micropump (PMP) and piezoelectric microvalves with annular boundary on PCB. Chip to be cooled is mounted directly on MCHS. PMP and piezoelectric microvalves enable EAMCHS to drive and control coolant, respectively. The finite element simulation model and theoretical model of cooling chip on PCB by EAMCHS are established to simulate and analyze its heat transfer characteristics and flow characteristics. The manufacturing and assembly based on PCB process are studied and EAMCHS is manufactured. The size and weight of the assembled EAMCHS are small (about 6.5 cm3) and light (about 18.2 g), respectively. Utilizing high temperature co-fired ceramic (HTCC) to simulate chip heating, the working performances of cooling chip on PCB by EAMCHS are experimentally tested and analyzed on the constructed experimental setup. Research results show that EAMCHS can control the temperature of HTCC at 64.0 °C with heat flux of 50 W/cm2 through the flow rate of 30.11 mL/min of coolant. The established theoretical model can describe heat transfer characteristics and flow characteristics of cooling chip by EAMCHS, which will be conducive to its structural design and optimization. The proposed EAMCHS has low energy consumption, small size and light weight, and provides a novel principle, novel method and novel structure for thermal management of chips highly integrated on PCB.

Management of waste printed circuit boards via supercritical water technology

In this study, the application of the supercritical water technology on the management of waste printed circuit boards (PCBs) obtained from small information technology (IT) and communication equipment was conducted. Initially, an extensive recycling-oriented characterization of waste printed circuit boards was conducted through a combination of several physicochemical analyzes such as MP-AES, XRF, TG/DTA, CHNS elemental analysis, SEM and XRD. Afterwards, at supercritical conditions of water (Tc > 374.29 °C and Pc > 22.089 MPa), the optimal conditions for the degradation of the organic polymers present in the waste PCBs were defined by a response surface methodology. A complete organic degradation rate (ODR) was achieved at 600 °C, reaction time of 60 min, waste PCBs load of 15 g and flow-rate of 5 mL min−1. After the removal of the organic polymers, the metals were liberated, and the metal recovery efficiency (MRE) reached values higher than 90% at all evaluated conditions. Then, initial insights on the subsequent treatment of the liquid decomposition by-products generated during the supercritical water (ScW) processing of waste PCBs were provided. A total organic carbon reduction of 99.88% was achieved via the ScW oxidation process using the same experimental apparatus. The treated solution was successfully re-used in the ScW processing of waste PCBs instead of clean water. Moreover, hydrogen, methane, CO2, and CO were identified as the major gaseous products associated to the supercritical water treatment of waste PCBs. Finally, a novel strategy to enhance the production of combustible gases, through the addition of ethanol and glycerol, and increase the economic feasibility of the supercritical water processing of waste PCBs was proposed.

A D-Band Multichannel TX System-in-Package Achieving 84.48 Gb/s With 64-QAM Based on 45-nm CMOS and Low-Cost PCB Technology

A high-data-rate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$ </tex-math></inline-formula> -band transmitter (TX) module cointegrating a dual-channel TX integrated circuit (IC) in 45-nm CMOS partially deplated silicon-on-insulator (PDSOI) technology and an antenna is presented. The proposed system-in-package is based on an innovative channel-bonding technique and is fabricated using a low-cost printed circuit board process. The IC consists of two upconversion chains, including on-chip millimeter-wave local oscillator generators. The emitted signal is composed of eight channels, each one having 2.16-GHz bandwidth, organized in two sets of four channels at the intermediate frequency (IF) band (around 61.56 GHz) that are upconverted to two adjacent subbands centered at 148 GHz. Then, the two subband signals are combined off-chip using a substrate integrated waveguide diplexer and radiated by a patch antenna array realized on the same package. The output spans from 139.3 to 156.6 GHz. The total equivalent isotropic radiated power is 8.3 dBm. An 84.48-Gb/s data rate is achieved with 64-QAM. The module consumes 600 mW from a 1-V supply and occupies a compact area of 12 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Cost estimation of photopolymer resin for 3D exposure of circuit boards

The research object in the work is the printed circuit boards (PCB) Production technological process using the additive technology of photopolymer 3D printing. The existing problem is that the manufacturing process of single-sided and double-sided PCBs, simple in technology, from the third to the fifth accuracy class, requires the use of a large amount of consumables and technological equipment. In turn, this affects the cost of the product. The research subject is models and methods for manufacturing PCB using photopolymer 3D printing. In order to reduce the cost of materials: film or aerosol photoresist, as well as reduce the number of technological operations, applying photoresist and for the manufacture of PCBs stencils, it is proposed to use photopolymer 3D printing technologies for the manufacture of PCBs. The paper analyzes the costs of Plexiwire Resin Basic Orange Transparen photopolymer resin for the manufacture of single-sided PCBs and calculates the cost of the consumable (resin) compared to the costs of dry film photoresist. 60 % cost of consumables (photopolymer resin) compared to dry film photoresist for making single-sided PCBs. The work is aimed at determining the dependence of the geometric dimensions of the PСВs topology and the consumption of photopolymer resin on the technological parameters of photopolymer exposure. A regression correlation model of the dependence of resin consumption on exposure parameters has been developed and correlation coefficients have been calculated. It has been established that with an increase in the exposure time of the photopolymer resin, the consumption of the photopolymer resin increases and the deviation of the geometric dimensions of the PCBs topology increases, which in turn negatively affects the quality of the product. Therefore, using the obtained regression model, it is possible to calculate the influence of parameters on the PCB topology and reduce the deviation of conductor sizes and resin consumption.

Design and Characterization of a Multi-Processed Differential Magnetic Field Probe by Using Asymmetric Calibration Method

In order to improve the spatial resolution of a magnetic near field probe, the design method combining multiple ports with multiple production processes has been proven effective. However, the asymmetry of transmission structure introduced by the junction between two different processes is a key problem that limits the performance of these probes. In this paper, a differential magnetic near field probe (diff-H-probe) combining flexible printed circuit (FPC) process with print circuit board (PCB) process has been manufactured to achieve high spatial resolution. The measurement results show that this probe can recognize a serpentine line with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~\mu \text{m}$ </tex-math></inline-formula> -width of trace and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~\mu \text{m}$ </tex-math></inline-formula> -space between traces. Meanwhile, an asymmetric calibration method (ACM) has been applied to significantly improve the performance of the diff-H-probe. Some key parameters of the probe with and without using the ACM are compared by using an air-dielectric microstrip line. The compared results show that the detection frequency range of the proposed probe is broaden to 12 GHz. Moreover, the results also demonstrate that the ACM can improve the differential electric field suppression up to 4.1 dB and improve the common mode electric field suppression to 20 dB at the frequency below 12 GHz.

Printed circuit board process based thermopile-type heat flux sensor used for monitoring chips

• Proposed PCB process based thermopile-type HFS can sense heat flux accurately. • Established sensing equation of HFS can accurately predict the performance. • Manufacturing process was proposed and used to manufacture HFS. • Manufactured HFSs were applied to monitoring heat flux of chip successfully. • Developed HFS can be embedded in system without affecting temperature field . At present, most of existing heat flux sensors (HFSs) have the disadvantages of large volume, complex manufacturing process, poor embedding property and affecting existing thermal field distribution, which seriously hinders the development and practicality of chip thermal management technology. To address the above issues, this paper presents a principle and structure of a novel thermopile-type HFS based on printed circuit board process (PCB) for monitoring heat flux of chips. According to the proposed principle, PCB process based thermopile-type HFS was designed and manufactured and its corresponding sensor equation was established. Experimental setups were built and manufactured HFSs were experimentally tested and also applied to monitoring the heat flux of chip on PCB, which is mimicked by a small electronic heating system. Theoretical and experimental results show that HFS designed and manufactured according to the proposed principle can sense heat flux accurately with the sensitivity, nonlinear error, repeatability error, time response and measurement range of 0.2670 μV/(W/m 2 ), 1.59%, 1.30%, 5 s and 0–20 kW/m 2 , respectively, and has the potential to be conveniently and flexibly embedded in electronic system to measure heat flux of chips with affecting existing temperature field as little as possible.

Applying Deep Learning to Construct a Defect Detection System for Ceramic Substrates

Under the emerging topic of machine vision technology replacing manual examination, automatic optical inspection (AOI) technology has been adopted for the detection of defects in semi-finished/finished products and is widely used for the defect detection of printed circuit boards (PCB) in electronic industries where surface mount technology (SMT) is applied. In order to convert images from gray-scale to binary in the PCB process, a strict threshold value was set for AOI to prevent ‘escapes’, but this can lead to serious false alarm because of unwanted noises. Therefore, they tend to set up a Noise-Removal procedure after AOI, which increases the computational cost. By applying deep learning to circuit images of the ceramic substrates in AOI, this paper aimed to construct an automatic defect detection system that could also identify the categories as well as the locations of defects. This study proposed and evaluated three models with integrated structures: ResNeXt+YOLO v3, Inception v3+YOLO v3, and YOLO v3. The outcomes indicate that the defect detection system built on ResNeXt+YOLO v3 could most effectively detect standard images that had been misidentified as defects by AOI, categorize genuine defects, and find their location. The proposed method could not only increase the inspection accuracy to 99.2%, but also help decrease the cost of human resources generated by manual re-examination.

A comparative analysis of printed circuit drying methods for the reliability of assembly process

Aim of the research was to examine the effectiveness of various methods to remove moisture from printed circuit boards (PCBs) depending on PCB's type and process parameters. The presented results are part of ongoing research on the absorption and desorption of moisture. The additional aim is to find new solutions to increase the reliability of electronics. The results are useful for whole EMS market because they facilitate to select the most appropriate method for their products. The initial conditions and parameters of the process are selected to reduce the risk associated with high temperature annealing while preventing damage caused by moisture during soldering.The FLEX, RIGID-FLEX and SEMI-FLEX PCBs were fabricated. All PCBs were humidified and exposed to drying conditions in which elevated temperature, reduced humidity or reduced pressure were utilized. The parameters were set by taking into account material characteristics, process time and operation cost. Mass of the samples was measured before and after annealing so as to evaluate the removed moisture. The highest removal rate was observed at the beginning of the drying. The recommended time was appeared to be 8 h. The most efficient method was high temperatures annealing, but it should be taken into account that the treatment can result in micro-damages and aging. It is recommended to limit repetitions of the process as well as to store PCBs at temperature in the range of 20–25 °C and humidity below 5% RH. An alternative is an annealing at reduced pressure and elevated temperature or application of anaerobic chamber with nitrogen and moisture below 0.5 ppm.

Root Cause Analysis of a Printed Circuit Board (PCB) Failure in a Public Transport Communication System

A printed circuit board (PCB) is an essential element for practical circuit applications and its failure can inflict large financial costs and even safety concerns, especially if the PCB failure occurs prematurely and unexpectedly. Understanding the failure modes and even the failure mechanisms of a PCB failure are not sufficient to ensure the same failure will not occur again in subsequent operations with different batches of PCBs. The identification of the root cause is crucial to prevent the reoccurrence of the same failure. In this work, a step-by-step approach from customer returned and inventory reproduced boards to the root cause identification is described for an actual industry case where the failure is a PCB burn-out. The failure mechanism is found to be a conductive anodic filament (CAF) even though the PCB is CAF-resistant. The root cause is due to PCB de-penalization. A reliability verification to assure the effectiveness of the corrective action according to the identified root cause is shown to complete the case study. This work shows that a CAF-resistant PCB does not necessarily guarantee no CAF and PCB processes can render its CAF resistance ineffective.

Автоматизоване проектування друкованих плат у CАПР та їх подальше виготовлення за допомогою CNC-машин

The article presents methods and means of 3D design of printed circuit boards in CAx. Automated placement of elements on the board is implemented by means of API SolidWorks using Visual Studio C#. The API application works by an algorithm that allows you to create a 3D layout of printed circuit boards. Each component of the library contains a conditional graphic notation of the element. With the help of the implemented algorithm, a comprehensive approach is provided, which consists in the fact that already at this stage the preparation of the strategy for tracing the conductors of the future printed circuit board is carried out, the classes of circuits are determined and the necessary technological parameters are set, as well as the data necessary for the preparation of design documentation is generated. After the completion of the work on the input of the scheme, a check is made for the presence of errors and compliance with the specified parameters, and if the test is successful, a list of circuits is generated for transfer to the tracing program. From this moment, any possibility of errors in the subsequent stages of design is excluded. CAD DipTrace was used to trace printed circuit boards and generate g-code. Printed circuit board processing is carried out on a CNC machine - CNC3018 using the Candle program. The printed circuit board tracks are created by forming a groove between the track and the metallized coating of the textolite. With the help of the formed height map, the uniform removal of the metallization layer over the entire area of the textolite is ensured. In addition, holes are drilled for the output elements of the circuit, the printed circuit board is cut along the contour and covered with a layer of tin to prevent oxidation of its metallized coating. The considered CAD methods and tools made it possible to automate the design of the printed circuit board of the FM radio receiver control module. As a result of the performed work, means of automating the design of printed circuit boards were applied and a fully functional printed circuit board with a track width of 0.8 mm was obtained.

Integrated Slotted Serpentine Waveguide to Enhance Radiation Properties and Efficiency

Slotted waveguides are often used when high-power and high-efficiency antennas must be designed and particularly for millimeter waves applications (automotive radar for example). But it is not easy to choose any distance between radiation slots because of the guided wavelength, to obtain a wide beam in E plane and so to cover a wide angular sector in beam scanning antennas. Moreover, the main beam depends of frequency because it is a progressive wave antenna. In this article, the authors propose an original solution based on a slotted serpentine waveguide with slots on the narrow wall of the waveguide allowing to obtain a very wide radiation pattern in E plane, and this antenna is manufactured, thanks a PCB (printed circuit board) process with empty waveguides to enhance the efficiency for the global structure. Simulations and measurements are given to validate the idea and the technological process in W band, and some different prototypes demonstrate that it could be possible to obtain a wide angular sector in a beam scanning antenna configuration.

Improved profit model for production of MicroLED PCB with asymmetric specifications

Due to strict requirements for high-tech processes, yield is an essential performance measure of quality output and affects production economics significantly. Yield is a performance index that significantly influences the optimal decision on profit and production quantity. For instance, in micro light-emitting diodes (MicroLED) manufacturing, the yield of surface mounting highly affects the production cost. To guarantee the production decision is reliable, accurately evaluating yields is crucial. However, the existing yield evaluation method for asymmetric processes with a very low fraction of defective by process capability index is conservative and may mislead the decisions. In this paper, a revised unbiased estimator is investigated and a weighted parametric bootstrap method for accurate production decision making is provided. With extensive comparisons, the proposed method outperforms the existing analytical method and considerably improves the precision of yield evaluation. We also provided managerial insights for a profit with various yield measure methods. For demonstration, an application of production yield determination for a printed circuit board process for MicroLED is presented.