Multilayer Printed Circuit Board Research Articles

Ka-Band Wide-Angle Scanning Phased Array with Dual Circular Polarization

A wide-angle scanning phased array with dual circular polarization in the Ka-band is presented in this paper. To improve the scanning capability of the phased array, the microstrip element is modified by loading many metal posts at its center and periphery. In addition, a stripline coupler is designed to achieve dual circularly polarized (CP) radiation, and the inner conductor of the subminiature micro-push-on (SSMP) connectors for feeding the coupler is extended to the top layer of the multilayer element by introducing an open stub, which simplifies the assembly process between the SSMP connector and multilayer printed circuit board (PCB) due to through-hole soldering instead of blind-hole soldering. The proposed element can cover a frequency range from 28 GHz to 30.5 GHz with a relative bandwidth of 8.5% in the Ka-band. An 8 × 8 phased array is constructed based on this proposed element, and a wide-angle scanning range from −65° to +65° is obtained for the dual circular polarization. The proposed array has a gain fluctuation of 5.1 dB and an axial ratio (AR) of less than 3.3 dB during beam-steering. The prototype is fabricated and measured, with a good agreement between the measured and simulated results. The proposed phased array can be applied in a Ka-band millimeter-wave (MMW) communication system.

Novel, compact electrochemical and impedance instrumentation

This paper presents the development of a novel, compact electrochemical and impedance instrumentation utilizing an analog integrated circuit (IC) for biosensing applications. Given the increasing availability of multifunctional integrated circuits (ICs), there is a growing need for devices capable of versatile applications spanning multiple fields. To address this requirement, a design was tailored to accommodate multifunctional techniques for biosensing. By combining multi-layer printed circuit board (PCB) techniques with 3D printing, the module was compact and capable of cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) measurements. Additionally, a comparison was conducted between the CV functionality of a commercial and the customized module. The results demonstrated that the customized module outperformed the commercial module. The Bode and Nyquist plots obtained from the EIS measurements accurately depicted the impedance values of resistance (R) and capacitance (C) in basic RC circuits. The experimental results show the error of R was below 2% and C was below 4% across the full frequency range from 500 Hz to 10 kHz. Furthermore, the high performance of this system was demonstrated by its successful application in monitoring the ripeness of bananas through EIS measurements. These measurements specified the total impedance and phase to assess the ripening stages accurately. This suggests the potential of the proposed system for utilizing impedance measurements in controlling fruit quality. Based on the achieved results, the proposed system holds promise for various electrochemical research and monitoring applications, particularly for electrochemical sensors and biosensors.

Solution for pre-pressing surface treatment of the conductive pattern of the inner layers of multilayer printed circuit boards

Solution for pre-pressing surface treatment of the conductive pattern of the inner layers of multilayer printed circuit boards

Comparison of Different NDT Techniques for Evaluation of the Quality of PCBs Produced Using Traditional vs. Additive Manufacturing Technologies.

Multilayer printed circuit boards (PCBs) can be produced not only in the traditional way but also additively. Both traditional and additive manufacturing can lead to invisible defects in the internal structure of the electronic component, eventually leading to the spontaneous failure of the device. No matter what kind of technology is used for the production of PCBs, when they are used in important structures, quality control is important to ensure the reliability of the component. The nondestructive testing (NDT) of the structure of manufactured electronic components can help ensure the quality of devices. Investigations of possible changes in the structure of the product can help identify the causes of defects. Different types of manufacturing technologies can lead to diverse types of possible defects. Therefore, employing several nondestructive inspection techniques could be preferable for the inspection of electronic components. In this article, we present a comparison of various NDT techniques for the evaluation of the quality of PCBs produced using traditional and additive manufacturing technologies. The methodology for investigating the internal structure of PCBs is based on several of the most reliable and widely used technologies, namely, acoustic microscopy, active thermography, and radiography. All of the technologies investigated have their advantages and disadvantages, so if high-reliability products are to be produced, it would be advantageous to carry out tests using multiple technologies in order to detect the various types of defects and determine their parameters.

Development of Printed Circuit Boards with High Thermal Conductivity and Low Thermal Expansion by Applying Cu-Mo Composite Materials

In recent years, electronic devices are strongly required to be smaller, lighter, and more powerful. As a result, mounted components have become smaller, more powerful, and denser, and the heat generation density on printed circuit boards (PCBs) has increased. Since rising component temperatures can lead to component failure, efficient heat removal from the generated heat has become an urgent issue. Since general PCBs have low thermal conductivity, when high heat dissipation is required, methods to increase the thermal conductivity of PCBs have been employed by increasing the copper (Cu) content in the PCB or by placing an aluminum (Al) alloy in the inner layer. However, while Cu and Al have high thermal conductivity, they also have high coefficients of thermal expansion (CTE) and young’s modulus, and the CTE of a PCB with increased thermal conductivity using these materials is high. If the thermal expansion difference between the PCB and mounted components is large, reliability against heat cycles cannot be obtained. Therefore, we have focused on copper-molybdenum (CuMo) composite materials with high thermal conductivity, high elastic modulus, and low thermal expansion. We have been utilizing Cu-Mo for the development of our PCBs and fabricated multilayered CuMo composite PCBs; therefore, this report will focus on the results regarding thermal characterization of prototype PCBs.

Detection of defects in printed circuit boards by the acoustic emission method

Objectives. Defects in the form of layering may occur during lamination in the production of multilayer printed circuit boards (MPCB). These defects cannot be detected by optical and electrical methods of output control. However, they can lead to breaches of the mechanical mode of operation and failures while running radioelectronic devices. In order to detect such defects, the acoustic emission (AE) method is proposed. This is based on the occurrence and propagation of acoustic waves in MPCBs caused by the presence of defects. The aim of this study is to investigate the possibility of using the AE method to detect defects in multilayer printed circuit boards. These defects can occur, in particular, in the lamination process.Methods. A mechanical processes modeling program (for research on the MPCB model) and various samples of two-layer printed circuit boards with pre-introduced defects (for experimental studies) were used to study the propagation of acoustic signals in the MPCB in the presence of defects. A solenoid mounted on the MPCB was used as a source of acoustic signals, while a piezoelectric sensor was used to receive signals. Data processing was carried out by comparing AE signals obtained for a serviceable MPCB sample and for MPCB samples with defects.Results. Simulation of the acoustic signal propagation in MPCBs in serviceable and faulty (with a rectangular defect in the form of delamination) states was carried out to show the difference in the received signals at the sensor installation point. Experimental studies were also conducted to examine the AE method applicability for detecting defects of various sizes and quantities.Conclusions. The studies demonstrated that the AE method allows the presence of defects in MPCB occurring during the lamination process to be detected effectively and reliably. This study proposes a new approach to non-destructive testing of MPCB using the AE method. This method significantly increases the reliability of MPCBs and the efficiency of their production processes.

Applying Characteristic Impedance Compensation Cut-Outs to Full Radio Frequency Chains in Multi-Layer Printed Circuit Board Designs.

Modern wireless communication systems are of utmost importance to various sectors such as healthcare, education, the household, and the advancement of emerging technologies like the internet of things, autonomous vehicles, and the enhancement of 5G. Further development and improvement of these systems drives the need for small dimension, high integration and density, and cost-effective electronic devices. Achieving optimal performance in wireless electronic devices involves overcoming engineering challenges related to microstrip line signal integrity. This research addresses the impact of surface mount technology (SMT) component pads on signal integrity, proposing a novel high-frequency microstrip line structure for mitigating impedance discontinuities. The study introduces stepped microstrip lines and explores characteristic impedance compensation techniques. A six-layer printed circuit board (PCB) structure is presented, and the effects of compensation on signal integrity are analyzed using time-domain reflectometry and scattering parameter measurements. The results demonstrate the effectiveness of compensation methods in aligning characteristic impedance with desired values, thereby ensuring improved impedance matching and transmission coefficients. The average over-the-length impedance for the proposed structure with compensation applied was measured to be 52.7 Ω, which is only 1.3 Ω (2.5%) more than that of the reference microstrip. Applying reference plane cut-outs leads to a maximum compensated absolute value of more than 30 Ω to reach the target impedance with a 10% tolerance. This research contributes valuable insights for advancing wireless communication systems and maintaining robustness in high-frequency microstrip transmission lines.

Analysis of the thermal effect of two external parallel printed circuit board conductors set on a metal base and operating in a space vacuum on each other

Background. The need to analyze the thermal effect of two external parallel conductors is due to an increase in the density of the conductive pattern. For printed circuit boards set on a metal base and operating in the vacuum of space, this need is aggravated by the weakness of the issue's development. 
 Aim. Analysis of the mutual influence of two external parallel printed circuit board conductors set on a metal base and operating in a space vacuum on each other to identify the dependence of their temperature on the distance between them and determine the distance at which this dependence practically disappears.
 Methods. To achieve the purpose, a finite element method calculation implemented in the ANSYS program, the Steady-State Thermal module, was used. Three multilayer printed circuit boards were calculated: 4-layer, 6-layer, 8-layer. The temperature coefficient of resistance was taken into account separately, by recalculation.
 Results. Graphs of the dependence of overheating (the difference between the temperature of the printed conductor and the metal base) on the distance between the printed conductors were constructed. The approximation of the obtained results is carried out. According to the approximated dependencies, the minimum values of the distances between printed conductors are found, at which the cross influence of printed conductors practically disappears. As the thickness of the printed circuit board increases, this distance increases.
 Conclusion. The results obtained can help to assess the influence of neighboring printed conductors in the design of the boards of the onboard equipment of spacecraft.

Dual-wideband radiating surface using interleaved electric and magnetic currents: Underlying physics and experimental verification

Unlike popular multiband antenna array radiation based on either electric or magnetic surface currents, the use of mutually interleaved and tightly coupled electric and magnetic currents results in an aperture-reuse space-efficient multiband radiating surface for highly integrated antenna-frontend architecture and spatial power combining design scenarios. In this work, slot and dipole modes corresponding to magnetic and electric currents are effectively interleaved and excited in a surface to develop a space-efficient dual-wideband aperture-shared radiating surface. In this case, due to an effective reuse of the antenna aperture over both frequency bands, a high aperture-reuse efficiency is achieved. First, we devise a planar magneto-electric (ME)-dipole-alike antenna and analyze it in both the frequency and time domain. The antenna is then studied by the characteristic mode theory and the findings are validated using full-wave simulations. The developed planar ME-dipole-alike antenna is used to realize a dual-wideband radiating surface in which electric and magnetic currents are mutually coupled and interlaced, which is excited by properly oriented and distributed sources on the antenna's surface. Eventually, a highly isolated dual-wideband prototype was developed and fabricated using a cost-effective multi-layer Printed Circuit Board (PCB) process that operates in the Ku-band with both impedance and gain bandwidth of approximately 42% and in the Ka-band with respective impedance and gain bandwidth of 29% and 16.32%.

10 GHz MONOLITHIC FILTER BASED ON STRIPLINE RESONATORS WITH SPLIT CONDUCTOR

The monolithic design of the compact bandpass filter X-band is made on technology of multilayered printed circuit boards. A quarter-wave stripline resonators of the filter have two conductors divided by the layer prepreg having low parameters which is bonding together a design. This eliminates influence of prepreg on the characteristics of the devices, ensuring good repeatability of filters in mass production. For increase the high-frequency stopband of filter, one of the conductors of each resonator is cut in half by a transverse slit. The constructive sizes of the device were obtained by parametric synthesis using the electrodynamic analysis of its 3D model. The experimental data of five-order filter are in good agreement with the electromagnetic simulation of filters 3D model. An experimental device has a central frequency of the passband of 10 GHz and fractional bandwidth of 5.7%, its dimensions and weight are 18.0 × 5.4 × 2.1 mm and 0.5 g. The important advantage of the developed design is the possibility of its installation on the board using the surface mounting method.

Analysis and Design of a Diplexing Power Divider for Ku-Band Satellite Applications.

In dual-band RF front-end systems, to transmit different frequency signals in different paths, each path requires the power to be divided along two transmission channels. In such systems, a circuit is created in which the input ports of power dividers with different frequency bands are connected to the output ports of a diplexing circuit in a cascade form. These circuits often contain different band filters in their schemes and have a complicated design. In this paper, an innovative technique for designing a diplexing power divider for Ku-band applications is presented. The proposed structure is designed on multilayer printed circuit boards (PCBs) and the utilization of a transition based on an extended SMA connector. The extended SMA connector provides two separate paths for the transmission of the RF signals. Hence, the proposed structure eliminates the need for intricate and bulky bandpass filters, allowing seamless integration with other planar devices and components within Ku-band satellite subsystems. In fact, the proposed architecture channelizes the divided output electromagnetic signals into two separate frequency spectrums. With the presented technique, two frequency ranges are envisaged, covering Ku-band applications at 13-15.8 GHz and 16.6-18.2 GHz. With the proposed structure, an insertion loss as low as 1.5 dB was achieved. A prototype of the proposed power-divider diplexing device was fabricated and measured. It exhibits a good performance in terms of return loss, isolation, and insertion losses.

A Fast Object Detection-Based Framework for Via Modeling on PCB X-Ray CT Images

For successful printed circuit board (PCB) reverse engineering (RE), the resulting device must retain the physical characteristics and functionality of the original. Although the applications of RE are within the discretion of the executing party, establishing a viable, non-destructive framework for analysis is vital for any stakeholder in the PCB industry. A widely regarded approach in PCB RE uses non-destructive x-ray computed tomography (CT) to produce three-dimensional volumes with several slices of data corresponding to multi-layered PCBs. However, the noise sources specific to x-ray CT and variability from designers hampers the thorough acquisition of features necessary for successful RE. This article investigates a deep learning approach as a successor to the current state-of-the-art for detecting vias on PCB x-ray CT images; vias are a key building block of PCB designs. During RE, vias offer an understanding of the PCB’s electrical connections across multiple layers. Our method is an improvement on an earlier iteration which demonstrates significantly faster runtime with quality of results comparable to or better than the current state-of-the-art, unsupervised iterative Hough-based method. Compared with the Hough-based method, the current framework is 4.5 times faster for the discrete image scenario and 24.1 times faster for the volumetric image scenario. The upgrades to the prior deep learning version include faster feature-based detection for real-world usability and adaptive post-processing methods to improve the quality of detections.

The multi-scale fusion reconstruction algorithm of CT and CL

Computed tomography (CT) is a widely used nondestructive testing (NDT) technique for material research, paleontology research and other fields. However, it is difficult for CT to reconstruct flat objects at high magnification ratios. Computed laminography (CL) enables high-resolution imaging for flat objects due to its unique scanning geometry. A challenging task for CL image reconstruction is to deal with the cross-section artifacts resulting from the incomplete projection data acquired from the CL scan. An effective multi-scale fusion reconstruction algorithm of CT and CL was proposed in this paper. The algorithm combining the advantages of the two scanning geometries, low-resolution CT data was used to compensate for the data missing in CL projection domain, and the cross-section artifacts were reduced. Experiments on paleontological fossils and multilayer printed circuit boards (PCB) were performed, where CT and CL data from different systems and scanning conditions. The results showed that the method can effectively suppress the cross-section artifacts of CL and obtain high-resolution reconstructed images.

Bending analysis of glass fiber reinforced epoxy composites/copper-clad laminates for multi-layer printed circuit boards

Printed circuit board (PCB) is the most important part of any electronic device which is made of copper-clad laminate and glass fiber-reinforced composites. Since the ply orientation of fiber-reinforced composites and lamina thickness have a significant influence on the mechanical properties of the whole composite laminate it is necessary to investigate the effects of ply orientation and lamina thickness on the bending properties of PCB so that they can be manufactured to meet the service requirements. In this work, the bending properties of PCB were investigated for seven different ply orientations of glass fiber-reinforced composite laminas and for eight different thickness combinations (for a constant laminate thickness) of glass fiber-reinforced composite lamina and copper-clad laminate. A commercially available finite element analysis software (Abaqus) was used to simulate a three-point bending test of PCBs and the simulation results were validated using experimental results. It is found that the bending stiffness is maximum for the cross-ply laminate. The introduction of angle ply improves the maximum von-Mises stress of the PCB with an insignificant cost of bending stiffness (less than 5% reduction). It is found that the bending stiffness and the maximum von-Mises stress of the PCB can be regulated through the variation of thickness of the constituent lamina. The laminate stiffness can be increased by increasing the thickness of stiffer laminas or by placing the stiffer laminas towards the surface of the laminate. The outcome of this research would provide a comprehensive understanding of the bending characteristics of the multi-layered PCBs which can be directly utilized by the PCB manufacturers. However, the effects of ply orientation and lamina thickness variation on the behavior of the PCBs subject to temperature variation, impact loading, vibration, and other conditions that might affect the service life of the PCBs should be investigated.

Methodology for choosing the optimal layout of multilayer printed circuit boards taking into account external mechanical influences

Formulation of the problem. radio-electronic modules on multilayer printed circuit boards (PCB) are characterized by an extremely complex design. When creating such modules, it is necessary to take into account, often extremely contradictory, requirements for the placement of components on the surface, taking into account thermal criteria, requirements for vibration strength and electromagnetic compatibility. Special-purpose radio equipment is often placed in blocks of a "cassette" design, which has a feature in fixing the PCB. Unlike conventional printed circuit boards, in this design, the PCB can only be fixed at the edges, so the placement of components, especially those with a large area, for example, such as microcircuits in BGA, QFP, QFN, PLCC packages, must be given great attention, as this affects mechanical strength and performance of the device. Purpose. Improving the efficiency of the design process of radio-electronic modules by rational placement of components on the PCB of a "cassette" design. Identification of areas with the highest mechanical stresses and deflections. Results. It was found that on the PCB of a "cassette" design, when it is fixed only around the perimeter, there are areas with increased deflections, where the installation of components with a large area is undesirable, since this leads to the destruction of the solder joint and the failure of the device. The board can be conditionally divided into nine areas with an aspect ratio of a/4 and b/4, where a, b are the length and width of the board. Experimentally, the most loaded areas of the MPP and areas that have the least impact on the component during external vibration were identified. Practical significance. A method for placing components on the PCB of a "cassette" design is proposed, which makes it possible to reduce the negative effects of external vibrations and static loads.

Highly Integrated Ka-Band Multi-Beam Network Design Based on a Low-Cost Multi-Layer Printed Circuit Board

A Ka-band low-profile and low-loss tile-type four-beam network based on high-density interconnection printed circuit board (PCB) technology is proposed, which integrates a power supply network, serial peripheral interface (SPI) control network, and four-beam radio frequency (RF) feeding network. In order to realize the fast optimal design, an integrated multi-beam network topology and fast optimization methods are established. The proposed feed networks can be integrated with antenna array structures directly, which not only realizes low-profile, light, and miniaturized design but also achieves efficient heat dissipation and low-loss interconnection. The designed multi-beam network has an amplitude balance better than ±0.5 dB and a phase balance better than ±6° in the Ka-band with a 4 GHz working bandwidth. A prototype was fabricated and measured, and good performance was observed.

FanoutNet: A Neuralized PCB Fanout Automation Method Using Deep Reinforcement Learning

In modern electronic manufacturing processes, multi-layer Printed Circuit Board (PCB) routing requires connecting more than hundreds of nets with perplexing topology under complex routing constraints and highly limited resources, so that takes intense effort and time of human engineers. PCB fanout as a pre-design of PCB routing has been proved to be an ideal technique to reduce the complexity of PCB routing by pre-allocating resources and pre-routing. However, current PCB fanout design heavily relies on the experience of human engineers, and there is no existing solution for PCB fanout automation in industry, which limits the quality of PCB routing automation. To address the problem, we propose a neuralized PCB fanout method by deep reinforcement learning. To the best of our knowledge, we are the first in the literature to propose the automation method for PCB fanout. We combine with Convolution Neural Network (CNN) and attention-based network to train our fanout policy model and value model. The models learn representations of PCB layout and netlist to make decisions and evaluations in place of human engineers. We employ Proximal Policy Optimization (PPO) to update the parameters of the models. In addition, we apply our PCB fanout method to a PCB router to improve the quality of PCB routing. Extensive experimental results on real-world industrial PCB benchmarks demonstrate that our approach achieves 100% routability in all industrial cases and improves wire length by an average of 6.8%, which makes a significant improvement compared with the state-of-the-art methods.

Improving the Microwave Generator Module Design

The article presents the results of improving the voltage-controlled oscillator (VCO) design by arranging part of the conductors of the topological metallization pattern of multilayer printed circuit board (MLPCB) with capacitive elements (communication lines of the coaxial output with the control and generator components) at the end of coaxial dielectric resonator (CDR), which made it possible to improve the electrical and weight and size characteristics of the generator.

Low-Profile circularly polarized substrate integrated array antenna

In this paper, a novel low-profile circular polarization (CP) substrate integrated array antenna is proposed which is designed as a multilayer printed circuit board (PCB) structure, consisting of a lower feeding part-substrate integrated waveguide (SIW) and an upper radiating element - sixteen hollow square patches (HSP) evenly distributed in a square array and divided into four groups. The circular polarization (CP) characteristic is realized by chamfering each HSP in the left and right corners, and the greatest common bandwidth of the return loss and the axial ratio (AR) is obtained by adjusting the top chamfer size of each HSP. Simulation results show that the overall usable CP bandwidth is 41.2 GHz-42.1 GHz, the gain in the operating frequency band and the radiation efficiency (RE) are up to 16.1dBic and 91%, respectively, and the low-profile of antenna is less than 0.1λ 0.

D-Band Air-Filled Substrate Integrated Waveguide (AFSIW) and Broadband Stripline to AFSIW Launcher Embedded in Multi-Layer PCBs

We report <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 air-filled substrate integrated waveguides (AFSIWs) with solid copper sidewalls fabricated inside a multi-layer printed circuit board (PCB) with broad wall width of 1.6 mm and cavity height of 300 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m. Measurements show a loss of 0.07–0.08 dB/mm across 115–155 GHz. This result is the first demonstration of an AFSIW above 100 GHz in a low-cost mass manufacturable PCB and has the lowest loss compared to reported planar PCB lines or substrate integrated waveguides (SIWs) in PCBs and Interposers. We also introduce a broadband stripline to the AFSIW launcher using a broad wall transverse slot which offers ease of manufacturability over existing transitions having a measured insertion loss of 1.1 dB and 27% bandwidth. The combination of a low-loss AFSIW and wideband launcher allows both striplines and AFSIWs to coexist in the same multi-layer PCB.