Printed circuit boards isomorphism: An experimental study

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.

An innovative approach is described for diagnosing faults in printed circuit boards (PCB) and PCB components through the detection, analysis, and localization of electrical field changes that occur within and around the PCB. This method utilizes electromagnetic emissions (EME) originating from the PCB to determine circuit health. EME from rapidly changing voltages and currents within high-speed logic and other circuits have traditionally been seen as a problematic source of interference that must be eliminated to as great an extent as possible. However, changes within these emissions can be a highly significant indicator that a failure has occurred within a PCB component as well as within adjacent circuit card paths of the board itself. Further, the hardware and software requirements needed to capture and analyze these emissions are relatively simple in comparison to todaypsilas highly complex automatic test equipment. This unique approach involves analyzing electromagnetic emission signatures through automated means, and ascribing failures to the circuit board as a whole, as well as to the individual circuit board components.

"Electronic manufacturing is currently one of the fastest growing industrial areas. This is due to the rapid advances in the computer and telecommunications sectors. Due to these advances, new surface mount devices have been developed to achieve greater miniaturisation at lower costs. As a result, a new surface mount technology has been developed to mount these devices onto printed circuit boards. However, problems exist with aspects of this process, principally open solder joints which result from circuit board warpage. The aim of this thesis is to undertake a) both an experimental and theoretical investigation of the reflow solder process and b) to develop thermal and structural models to analyse circuit board warpage. This research should aid manufacturing engineers in understanding the influence of the solder reflow process parameters on board warpage. Extensive experimental testing of the circuit board materials during the process is also presented. The thermal model detailed in this thesis simulates a) forced convective heat transfer through air impingement to the boards and b) the three dimensional temperature distribution within a composite laminate. The thermal model predicts the temperature distribution within a populated laminated composite circuit board to within 3% when compared to experimental data. The experimental results show that the convective heat transfer coefficient is primarily dependant on Reynolds number, and also the orifice to plate distance and orifice diameter. It was found that at high Reynolds number, the heat transfer coefficient increases significantly at low orifice to board distance. This heat transfer rate has to be balanced against the maximum speed of the air to prevent the components been blown off the boards. The 5mm diameter orifice provides the optimum balance between air speed and heat transfer rate. The structural model simulates the influence of a) board support, b) reflow temperature profile, c) components on the board and d) board layup on circuit board deformation. The experimental appraisal and model predictions show that the warpage of the printed circuit boards is dependant on a) support of the board during the process, b) symmetry of the board layup, c) coefficients of thermal expansion of the board materials, d) temperature distribution in the boards i.e. symmetric or nonsymmetric about board centre and e) temperature applied to the board. This research proves that if adequate support is applied to the boards during the reflow soldering process then, the warpage of the printed circuit boards may be kept within acceptable margins. Board warpage exists in current printed circuit boards because a) the boards cannot be manufactured truly symmetric in layup and b) Non-uniform temperature distributions are present in the board during the solder reflow process which leads to non-uniform expansion of the constituent laminate layers due to their varying coefficients of thermal expansion."

The rapid development of information and communication technologies has driven the rapid growth of data traffic and the large requirement of high-speed optical transceiver modules. Usually, optical subassemblies through flexible printed circuit boards (PCBs) connect with the hard PCBs to compose as optical transceiver modules. Because of the impedance mismatch of connection between flexible PCB and hard PCB, the operation bandwidth of the module can be limited. In this paper, the design of connection between flexible PCB and hard PCB in optical subassembly modules will be investigated for increasing the operation speed of the module. First, the transmission bandwidth of flexible PCB is analyzed. High-frequency performances of three transmission line structures, micro-strip line, grounded coplanar waveguide, and top ground micro-strip line, are investigated in flexible PCB. High-frequency performances of flexible PCB with different bending types are also investigated. The flexible PCB has been verified to be suitable to use in 25 Gb/s applications. Next, the high-speed transmission performance is analyzed through the connection between flexible PCB and hard PCB, because the impedance mismatch usually occurs at the connection. The ground pads are added near the signal line of flexible PCB, and the ground pads are connected to the ground layer in PCB through ground vias. The anti-pad in hard PCB is added under the signal solder pad. The dip of S21 response can be eliminated by the optimized ground pad. The impedance mismatch can be reduced by the optimized anti-pad, the impedance increases from 40-Ω to 49-Ω at the connection between flexible PCB and hard PCB, and the transmission bandwidth can increase from 16.5 GHz to 23.5 GHz. TO-46 header is a common and low-cost packaging solution for DFB laser and photodiodes. The connection between flexible PCB and TO-46 header is also investigated. While the connection has a gap, the dip of frequency response will occur at lower frequency. While the connection is very close, the bandwidth can be larger than 25 GHz. The flexible PCB, hard PCB, and TO-46 header are combined together, and the 23 GHz transmission bandwidth can be obtained. The 25 Gb/s transmission eye diagram is also measured, and the eye height, rise time, fall time, and Q-factor are 268.14 mV, 13.78 ps, 13.56 ps, and 8.76, respectively. The combined flexible PCB, hard PCB, and TO-46 header are verified to be suitable to apply in 25 Gb/s optical subassembly modules, and will be able to be used in 100G Ethernet.

This study analyzes laser processing of glass-based printed circuit boards which have the capability to replace conventional substrate materials when electronics are required to operate at elevated temperatures. There is significant potential for glass-based circuit boards within the field of aerospace and electric mobility. The new circuit board concept consists of thin copper-coated borosilicate glass with thicknesses ranging from 150 µm to 500 µm. Conventional mechanical processing of this new circuit boards induces stress on the thin glass which can lead to damage of the substrate. Therefore, laser processing with a picosecond laser source is suggested as a tool within the production process of the new circuit boards. Two necessary processes are investigated using a pulsed picosecond laser with a pulse duration of 7 ps at a wavelength of 515 nm. Precise drill-holes for vertical connections of multilayer boards were produced where chipping at the cutting edge must be avoided. Selective ablation of the copper coating was performed to generate the electrical circuits. The results show that a well-defined ablation process is crucial to achieve adequate electrical isolation without damaging the glass substrate. The study also underlines the huge potential of laser processing with picosecond laser sources, which have proven to be a versatile instrument to drill thin glass and generate electrical circuits by selective ablation.This study analyzes laser processing of glass-based printed circuit boards which have the capability to replace conventional substrate materials when electronics are required to operate at elevated temperatures. There is significant potential for glass-based circuit boards within the field of aerospace and electric mobility. The new circuit board concept consists of thin copper-coated borosilicate glass with thicknesses ranging from 150 µm to 500 µm. Conventional mechanical processing of this new circuit boards induces stress on the thin glass which can lead to damage of the substrate. Therefore, laser processing with a picosecond laser source is suggested as a tool within the production process of the new circuit boards. Two necessary processes are investigated using a pulsed picosecond laser with a pulse duration of 7 ps at a wavelength of 515 nm. Precise drill-holes for vertical connections of multilayer boards were produced where chipping at the cutting edge must be avoided. Selective ablation of the ...

Ball grid array (BGA) component packages challenge the circuit board design with signal routing and layout, creating in some cases extra board layers and added vias all resulting in increased costs for the printed circuit board (PCB). As component densities increase and microBGA (μBGA) and other fine pitch components become more common, microvia‐in‐pad technology will ease the transition to these fine pitch components. This paper presents and profiles a cost‐effective solution to interconnecting BGAs on PCBs using laser drilled blind vias connecting the outer three or more layers of a multilayer circuit board. Following a discussion on the design advantages, a comprehensive outline of the PCB fabrication process explores a new procedure for the rapid production of via‐in‐pad multi‐depth blind via laser drilling.

The materials used in the field of printed circuit boards are becoming increasingly complex as they are common to make use of numerous combination of metallic and composite plies. The potential for utilization of circuit boards is generally verified through the numerical simulation, especially for the multilayer printed circuit boards with high electronic density. This paper provides a numerical model intended to describe numerically the behavior of multilayer multimaterial circuit boards. Two parts are considered in the developed model: one is elastic-plastic damaging model that is presented to describe the metallic ply in the multilayer circuit boards; another is degenerated bi-phase model that is presented to describe composite ply. With the combination of equivalent laminate (EQLAM) method, the degenerated bi-phase successfully models the woven glass-fiber/epoxy-resin composite ply. These two plies are the basic components of multilayer circuit boards. Meanwhile, with the verification of static tests and dynamic tests, the reliability of presented model is confirmed.

Given a pin-grid-array (PGA) package with an area-array of I/O pins and some devices (blocks) distributed on a printedcircuit board (PCB), the authors propose an algorithm to obtain a pin assignment solution which eases the routing in the PGA package and then improves the nets routability of PCB. In the algorithm, the routing costs of PGA package and PCB have to be calculated separately during pin assignment. A simulated annealing technique is also applied to improve the solution by exchanging the pin assignment for some chosen nets in the PGA package. Simulation results on various PCB circuits show that PCB routings produced with pin assignment under consideration can be achieved far better than the routings without pin assignment.

The characterisation of printed circuit boards (PCB) removed from discarded mobile phones in Brazil and an inventory of data of the components in PCB were accomplished in this paper. Data of chemical composition of PCB were obtained from the physicochemical characterisation of their components through the analysis of granulometry, scanning electron microscopy with energy dispersive x-ray detector (SEM/EDS), infrared spectroscopy (FT-IR) and inductively coupled plasma optical emission spectrometry (ICP-OES). The analysis allowed a broad view and a highlight for the wide variety of elements and heterogeneity of the material. It can be also highlighted the high amount of copper, lead and other high-value metals in the PCB. This study is relevant for the development of new recycling technologies, once this material has been discarded incorrectly in Brazil. Based on the percentage of mobile phones recycled and disposed in Brazil, it is possible to quantify financial loss resulting from incorrect disposal.

The rapid increase in electronic waste has created a need for simple and safe recovery methods for reusable components from discarded circuit boards. Manual removal of components from printed circuit boards (PCBs) involves direct exposure to heat, fumes and sharp edges, making it unsafe and slow. This paper presents a compact, semi-automated system that uses a two-axis robotic arm to depopulate components from mobile PCBs. The system is built on a150mm×150mm wooden platform and uses an X–Y motion mechanism mounted below the surface. Three stations a PCB loading area, a solder-melting pot, and a collection tray are arranged in series on the top of the platform. The robotic arm moves horizontally and forward backward to pick a PCB, dip it in a heated solder bath for a very short duration, and transfer the loosened components into a tray. The mechanism is driven by low-cost geared motors and controlled through an Arduino microcontroller. Experimental trials on PCBs show that the system can reliably detach small surface-mount components after a 2–3 second dip. The work demonstrates a practical and low-cost approach suitable for small-scale e-waste processing units.

The frequency at the peak of electromagnetic radiation from a PCB (Printed Circuit Board) as a result of ground bounce is considered predictable from the frequency characteristics of the input impedance between the power supply and ground layer (below called the PCB impedance). However, the relationship is largely unknown. In this paper, the electromagnetic radiation of the PCB and the frequency spectrum of the PCB impedance are analyzed by the FDTD (Finite‐Difference Time‐Domain) method and their relational mechanism is studied by comparison with the measured values. It is found that the peak of the electromagnetic radiation appears at the frequency where the PCB is a minimum if the PCB is excited by a voltage source with an internal resistance sufficiently smaller than the PCB impedance, and that this peak is shifted toward the frequency at which the PCB impedance becomes a maximum if the internal resistance is increased. The radiation power ratio derived from the resistive components (called the resonant resistances) at two frequencies where the PCB impedance is maximum and minimum (resonant frequencies) mostly agrees with the ratio of the squares of the radiated electric field. Hence, the radiation peak frequencies of the PCB are determined both by the internal resistance of the excitation source and the resonant resistance of the PCB impedance. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 30–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10209

High density interconnect printed circuit board technology enables significant board size and layer count reduction. Thinner inner layer dielectric materials, reduced line widths, and closer spaced components inherent in high density board technology require a change in electrical design methodology. Most notably, the thinner dielectric thickness significantly impacts the electrical performance of the circuit board with respect to crosstalk, board capacitance, via inductance, and controlled impedance. Via inductance is significantly reduced as mechanically drilled through hole vias are replaced with microvias. Distributed capacitance will tend to increase because of the thinner dielectric layer and crosstalk between signal traces run on adjacent layers may also increase. Using either FR-4 type epoxy (diel, cnst.=4.0) or higher performance materials (diel, cnst.=2.8) conventional controlled impedance structures such as a stripline, microstrip, and coplanar waveguide are possible to design using current manufacturing capabilities. A 50 /spl Omega/ impedance can be achieved by a microstrip or a coplanar waveguide using either dielectric material. The stripline can only achieve approximately 35 /spl Omega/ with the higher performance material and 25 /spl Omega/ with the FR-4 type epoxy material. A 500 mW radio frequency receiver and transmitter module operating at 467 MHz was successfully fabricated using a three layer build-up high density circuit board. The circuit board construction had one build-up layer fabricated with a liquid epoxy material. The circuit board electrical design incorporated microstrip, stripline, and coplanar waveguide controlled impedance structures. The results of the electrical performance measurements indicated that transmitted power, receiver sensitivity, and frequency specification performance were similar to a six layer board manufactured with conventional technology.

Silver-plated electronic devices are extensively used in microwave circuits. The electrochemical migration of silver in these circuit boards can affect high-frequency characteristics and signal integrity. In this work, the effect of silver migration on signal transmission of printed circuit boards was evaluated using both experimental testing and analytic modeling. The S parameters of circuit boards with silver migration were measured. Based on multi-conductor transmission line theory and electrical properties of dendrite-like electrochemical migrated silver, a distributed parameter circuit model for the circuit board with silver migration was developed. The model results are in good agreement with those obtained from the experimental tests. The results of this investigation provide a better understanding of the high-frequency behavior of a circuit board with silver migration and theoretical support for identifying failure features in fault diagnosis.

In this paper, an improved efficient Faster R-CNN algorithm used in PCB solder joint defects and components detection is proposed. The accurate detection of solder joint defects and components on printed circuit boards (PCB) is very important to the quality of production of electronic products. The traditional automatic optical inspection needs a customized registration and program design for each circuit board. The necessary steps are complex and time-consuming, and the judgment standard is relatively simple and rigid, resulting in a poor generalization ability of detection and decreased detection accuracy, especially in the conditions of poor lighting, color change of circuit board, and multiple-variety and mini-batch production scenarios. In this paper, an improved Faster R-CNN PCB assembly solder joint defects and components detection algorithm, named Efficient Faster R-CNN, is proposed based on EfficientNet-B7. In this algorithm, the first eight stages of EfficientNet-B7 network structure are used to replace VGG-16 for feature extraction, and the generalized intersection over union ratio is used as the loss of bounding-box regression to avoid the non-optimal solution caused when the prediction boxes and the real boxes are disjoint. The proposed algorithm also uses the swish activation function with better performance to replace ReLU.The experimental results show that the detection accuracy of the proposed algorithm is significantly improved, with the mean average precision close to 0.99, which is of great significance for industrial application.

Industry-produced printed circuit boards (PCBs) used by the United States Navy and Marine Corps are typically coated with a layer of "conformal coating" made of silicone or polyurethane in order to protect electrical and electronic components on the board. Conformal coating has to be removed every time board troubleshooting and maintenance are performed, and must be reapplied after board maintenance is complete. This can be an expensive and time-consuming process. This paper describes an effort to develop a non-contact solution to detect failed components on a PCB without having first to remove the conformal coating. This patent-pending technique detects density changes in the physical makeup of circuit board components due to failure. By analyzing ultrasonic reflections from the components at 2MHz, the authors were able to distinguish between working components and failed components with varying degrees of accuracy. The authors applied this technique to 1KΩ resistors and three types of transistor-to-transistor logic (TTL) integrated circuits (ICs). Overvoltage faults were induced in these components in order to generate observable density changes. To reduce human error, a measurement rig was built which incorporated an automated X-Y-Z plotter system, in order to process dozens of components at a time without human interaction. The data gathered by this system was processed to isolate only the acoustic reflections of components on a circuit board. Time-domain and frequency-domain features were then extracted. These features were used to train neural networks to distinguish between working components and components with over-voltage faults that were not readily observable by eye. Each type of component or chip needed to have its own associated trained neural network. For 1KΩ resistors, the system has demonstrated seventy to eighty percent accuracy in distinguishing components with over-voltage faults. For two of the TTL ICs, eighty to eighty-five percent accuracy has been achieved. For one IC type, a fifty-five percent accuracy was measured. The authors have demonstrated that low-cost acoustic measurements in the megahertz range can be used to detect failures in ICs and other common circuit board components.