Current Printed Circuit Board Research Articles

Implementation of quality control systems based on machine vision and web technologies

The development of Computer Vision technologies has seen widespread adoption in various fields over the last time, including medicine, manufacturing, transportation, logistics, agriculture, and chemical industry. Research analysis indicates that Computer Vision and its practical implementation, known as Machine Vision, are widely used for defect detection in production and equipment. Despite significant research progress in this field in recent years, many unresolved issues remain concerning the quality and dimensions of input data, selection of image recognition models and their training, and the accuracy of results. Integration of machine vision system elements for information exchange and decision-making poses a significant challenge. This paper presents one approach to addressing this issue. The aim of the paper is to explore the implementation approach of quality control systems using web technologies. The task of detecting defects in printed circuit boards (PCBs) is common in many manufacturing processes. PCB inspection involves comparing the current PCB sample with a defect-free reference. Essentially, this task involves comparing two images and identifying differences between them. Defect recognition is based on the Structural Similarity Index (SSIM), which computes the degradation component reflecting the difference between images and the similarity component. The SSIM metric is already implemented in image processing libraries. This work utilizes calculations using OpenCV and scikit-image image libraries. To automate the PCB comparison process and address deployment and integration challenges at the SCADA level, a web application has been developed. This web application allows users to select a reference PCB image and upload the current PCB image for inspection. For the client-side implementation, Vue.js was chosen due to its popularity and efficiency in developing web interfaces, particularly Single Page Applications (SPAs). Vue.js's reactive system ensures automatic updates to reflect changes in data state. For the server-side implementation, Flask – a Python framework, was used, facilitating integration with the PCB comparison algorithm as both utilize Python. According to the available features, operators can upload two images – a reference PCB image and the PCB image to be compared with the reference. After uploading, the images are displayed in the system interface. On the server side, the received data is decoded and compared using the appropriate algorithms. After comparison, the results are encoded in base64 format and sent back to the client-side for display, allowing the operator to assess the similarity or differences between the PCBs. The application can operate in both automatic and manual modes. Therefore, an analysis of the challenges encountered in implementing and deploying quality control systems based on computer vision methods has been developed. The use of web technologies, particularly Python frameworks, for integrating developed models is proposed. This approach is demonstrated using the example of PCB defect recognition tasks.

LDD-Net: Lightweight printed circuit board defect detection network fusing multi-scale features

The current printed circuit board (PCB) defect detection model is difficult to balance accuracy and computational cost and cannot satisfy the requirements of practical applications. In this regard, a lightweight PCB image defect detection network (LDD-Net) with high accuracy is proposed in this study. First, LDD-Net designs a novel lightweight feature extraction network (LFEN), which adds convolutional layers for extracting large-scale feature maps and uses an efficient downsampling method to extract richer defect features. LFEN not only greatly reduces resource requirements, but also improves detection accuracy. Second, LDD-Net devises multi-scale aggregation network (MAN) to facilitate information sharing among feature maps at different scales. In addition, MAN incorporates an efficient attention module to suppress similar background interference. Finally, LDD-Net uses the lightweight decoupling head to detect three groups of shallow feature maps with rich information of the small object. Experimental results on the PCB defect dataset ,and VisDrone public dataset show that the mean average precision (mAP), recall, and precision of LDD-Net outperform state-of-the-art lightweight object detection models. The mAP, computation, number of parameters, and detection speed of LDD-Net are 95.90%, 21.48 G, 5.13 M, and 78.13 frames per second, respectively. LDD-Net effectively balances accuracy, computational cost, and detection speed for applications in edge systems or resource-constrained embedded devices.

A Novel PCB Defect Detection Method Based on Digital Image Processing

Printed circuit board (PCB) has a wide range of applications, and its automated quality inspection is a vital part of economic production. The time overhead of the current PCB defect detection method will increase with the increase in the number of detection targets. To ensure the stability of detection performance, this paper proposes a novel PCB detection method based on color threshold segmentation. Experiments show that this method can effectively detect and analyse various information about solder pads and solder pastes, among which the detection accuracy rate of solder pads is 99.4%, the missed detection rate is 0.4%, and the detection accuracy rate of solder paste is 99.3%, The missed detection rate is 0.03%. At the same time, the method in this paper has better robustness and stability than other PCB defect detection methods, and can better meet the needs of industrial production.

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.

All‐Fabric Flexible Frequency‐Selective‐Rasorber Based on Cutting‐Transfer Patterning Method

AbstractFrequency‐selective rasorber (FSR) can realize a passband between two adjacent absorption bands, which is essential in many electromagnetic scenarios such as antennas and cloaking technologies. However, the current printed circuit board (PCB)–based FSR has shortcomings such as being heavy, rigid, and complex structure (too many lumped elements), making it a long distance from practical military and civil applications. Here, a novel FSR comprised of carbon cloth/ copper cloth/ fabric hybrid structure is proposed to realize the function of frequency selective absorption for the application of indoor electromagnetic protection. Several sub‐subjects are studied, including the structure design of rasorber without lumped elements, the carbon cloth‐based planner resistive material, and the fabrication method of large area non‐contact patterns. Measured results show that a transmission window is achieved between two absorption bands with a transmission rate higher than 86%. Under the circumstances of similar electromagnetic properties, the sample has the unique features of simple structure, large area, high flexibility, and light‐weight compared with commonly used PCB technology, which largely improve the usability of FSR in practical civil or military applications.

Computational evaluation of a new digital tandem quadrupole mass filter.

A tandem mass filter consists of two low-resolution mass filters arranged in series that operate with a small offset between their mass windows. In principle, the overlap of the two individual mass windows defines the tandem window. Tandem operation provides improved resolution and transmission compared to a single mass filter operated with the same mass window. The improvement in transmission is owed to the larger acceptance of the low-resolution quadrupoles. The tandem filter resolution and transmission are adjusted by changing the amount of offset separating the mass windows of the individual filters. Sine wave systems create this offset through voltage changes. Digital tandem mass filters depart from convention because they do not change voltage. The tandem mass window is created when the individual filters are operated with two slightly different duty cycles. Both quadrupoles operate at the same frequency, phase, and voltage. When the frequency, phase, and voltage of each quadrupole are identical, there theoretically are no changes to the Mathieu parameters to cause ion excitation and loss during transition between the quadrupole pair. The work presented here shows that a fixed AC voltage digital tandem mass filter can only operate in higher stability zones. However, unlike sine mass filters, the mass range of a digital system is not limited. This makes the digital tandem mass filter feasible as a commercial product. For the tandem digital mode to be successful, the duty cycles of each quadrupole must be precisely controlled because the duty cycle differences required to shift the mass windows are small. The creation of these mass window offsets requires waveform generation that can obtain high duty cycle resolution. Our method of generating waveforms can meet this demand; however, modifications to our current printed circuit board must be made. These modifications are minor and will be discussed.

Scalability of Copper-Interconnects down to 3μm on Printed Boards by Laser-assisted-subtractive process

Abstract As per the latest roadmap of iNEMI, the global electronics market is emphasizing to identify disruptive technologies that can contribute towards denser, robust and tighter integration on the board level. Therefore, reduction in packaging factor of printed board can accommodate greater number of ICs to support miniaturization. This paper has shown an experimental method to pattern the metallic layer on a Printed circuit Board (PCB) to the smallest feature size. To investigate this, a commercially available FR-4 PCB with photosensitive material coat and a Copper (Cu) layer on it, is used. A reverse-mode Laser assisted writing is implemented to pattern the desired copper tracks. Soon after, a well-controlled development and chemical etching of the Laser-activated regions are done using Sodium Hydroxide solution followed by an aqueous solution of Sodium Persulfate. Current PCB interconnects used by the industries are of the order (~20 μm). Whereas the present work is a contribution towards achieving Copper interconnects with feature size 3.0μm. This miniaturization corresponds to 70% reduction in the feature size from 20 μm to 3 μm. The natural adhesion of the Cu layer has remained intact even after the etching, shows the efficiency of the method adopted. Also, variation in the parameters such as etching time, etchant solution concentrations, temaperature, gain and exposure time of Laser beam and their corresponding effects are discussed. Other highlights of this subtractive method includes its cost-efficiency, lesser production time and repeatability.

High Current Applications Issues in Designs of High Current Applications

This paper deals with design high current printed circuit boards (PCB), with the issues of implementation the power layer into standard PCB and influence of parasitic parameters of conductive traces of PCB. The parasitic parameters of conductive traces play a significant role in design of high current PCB, and therefore must be minimized. The technology of manufacturing PCB for high current designs as a compact device is mentioned in the paper. The quality of MOSFET switching power in high current design was compared in two ways of proposed leading power lines in order to demonstrate the influence of parasitic inductances of conductive traces.

YIG Thick Film as Substrate Overlay for Bandwidth Enhancement of Microstrip Patch Antenna

Research on microstrip patch antenna (MPA) has been growing in the past few decades due to its planar profile and easy fabrication. Its simplicity of structure, which includes a conductive patch, a dielectric substrate, a ground plane, and a microstrip feeder, is making it more popular for integration in devices which are more focused on miniaturization and flexibility. There are, however, a few disadvantages of MPA, such as narrow bandwidth, low power, and limited inexpensive material selection if a current printed circuit board etching fabrication technique is used. Ferrite substrates are known to be able to help overcome this issue, but the properties of bulk ferrites are difficult to control. This paper aims to solve this problem by using thick-film technology, which utilizes a screen printing method to include ferrite thick film in the MPA structure as substrate overlay to help enhance the performance of MPA. Yttrium iron garnet was chosen as the starting ferrite nanopowders, and the preparation and characterization of the ferrite thick-film paste were carried out to investigate properties of the thick film. Results showed that the thick film showed moderate permittivity and permeability, which is suitable for MPA fabrication. The actual fabricated MPA with ferrite thick-film inclusion on FR4 substrate showed that the thick film improved the performance of MPA with low firing temperature of 200 °C. For MPA which is designed to work at 5.8 GHz, the return loss and −3-dB bandwidth improved 100% and 73%, respectively. In conclusion, ferrite thick-film inclusion in MPA fabrication has proven to improve the performance of the antenna in terms of return loss and bandwidth enhancement.

Development of Embedded High Power Electronics Modules for Automotive Applications

The automotive industry has a strong demand for highly reliable and cost-efficient electronics. Especially the upcoming generations of hybrid cars and fully electrical vehicles need compact and efficient 400 V power modules. Within the engine compartment installation space is of major concern. Therefore small size and high integration level of the modules are needed. Conventionally IGBTs and diodes are soldered to DCB (Direct Copper Bond) ceramics substrates and their top contacts are connected by heavy Al wire bonds. These ceramic modules are vacuum soldered to water-cooled base plates. Embedding of power switches, and controller into compact modules using PCB (Printed Circuit Board) technologies offers the potential to further improve the thermal management by double-sided cooling and to reduce the thickness of the module. In the recently started “HI-LEVEL” (Integration of Power Electronics in in High Current PCBs for Electric Vehicle Application) project, partners from automotive, automotive supplier, material supplier, PCB manufacturer and research teamed up to develop the technology, components and materials to realize high power modules. The following topics of the development will be addressed in detail in this paper:Assemble of power dies (IGBT and diode) using new sinter die attach materials:The deployment of new no pressure, low temperature sinter paste for the assembly of the power dies is a mayor development goal. Here the development of a reliable process to realize a defect free bonding of large IGBT dies (up to 10x14mm2) is essentially. These pastes are applied by stencil printing or dispensing and the sintering will take place after die placement at temperatures of around 200 °C.Thick copper substrate technology:To handle the high switching current, suitable copper tracks in the PCB are required. The realization of such thick copper lines (up to 1mm thickness) requires advanced processing, compared to conventional multilayer PCB production. In this paper the essential development steps towards a 10 kW inverter module with embedded components will be described. The process steps and reliability investigations of the different interconnect levels will be described in detail.

Design and Evaluation of Bioepoxy-Flax Composites for Printed Circuit Boards

Printed circuit boards (PCBs) pose considerable occupational health risks during manufacturing and are a potential source of toxic hazards if improperly disposed at the end of their useful life. Indeed, base materials in current PCBs include epoxy resins, fiberglass, and brominated flame retardants. To improve the environmental performance of PCB manufacturing and disposal, we developed composite designs using a thermosetting matrix based on epoxidized linseed oil, melamine polyphosphate for flame retardance, and woven flax fiber for reinforcement. Analyses of our prototypes using IPC 4101A/24 specification for thick PCB laminates gave acceptable results for thermal, mechanical, and electrical properties, except for wet conditioning or water submersion. To improve moisture resistance, we treated flax fibers with sodium hydroxide and octadecyltrichlorosilane. We find that the improved bioepoxy-flax PCB design is a viable alternative to current PCBs; it has potentially lower environmental impacts, it is cheaper, and it has satisfactory thermal, electrical, and mechanical properties. However, additional improvements in moisture absorption properties may remain needed for commercial applications.

Manufacturing an environmentally friendly PCB using existing industrial processes and equipment

This paper investigates the possibility of utilising an additive screen printing process with conductive ink and adhesive together with a degradable substrate to identify whether this process offers a viable alternative to current subtractive methods of PCB manufacture. Existing manufacturing equipment and production process were adopted in order to establish the compatibility of a sustainable and environmental friendly PCB with these processes. Experimental trials have shown that by using a stainless steel stencil 150 mm thick in conjunction with an MPM Ultraprint machine with a printing speed of 89 mm/s, a squeegee pressure of 0.97 bar and a downstop of 1.9 mm successful printing of the electrically conductive adhesive was achieved. It was also shown that the substrate was compatible with electronic placement technology and convection oven. Comparisons of the electronic assemblies to an industrial IPC standard illustrated that it is possible to develop a circuit, which is deemed acceptable under this standard. It can be concluded therefore that a screen printed conductive ink pattern, when printed on a degradable substrate can offer a viable alternative to current printed circuit boards and can be manufactured using existing technology and manufacturing processes.

Practical issues in high speed PCB design

Current high-speed PCB (printed circuit board) designs need extra care due to the frequency of operation and reduced rise time signals. We present the main issues and parameters that a PCB designer has to consider and analyze before a board layout is created. First order approximation equations for various parameters are presented, based on the geometry of the PCB traces. Some useful design practices are also mentioned. As the speed of operation increases, the variables that are neglected in the lower frequency/higher rise time situation become more significant. Such parameters increase the complexity of the design. Three-dimensional analysis becomes a must to calculate and model interconnects accurately. This is where field solvers and the role of the signal integrity engineer come into play.

The effect of the hot air levelling process on skip solder defects in the wave soldering process

It was observed that “no solder” or “skipped solder” defects occurred on a particular printed circuit board assembly product during wave soldering. Investigations were carried out to find out the cause of this defect and to recommend an optimal hot air level coating thickness. To evaluate whether thicker plating helps to produce better solderability, new printed circuit boards with an average plating thickness of 4.27 μm were sent for solderability testing. This increase in plating thickness resulted in no defects in the solderability test. This is in contrast to the current printed circuit board that had a no/skipped solder defect rate of 1,433 ppm due to the thinner plating thickness which was in the region of 2.26 μm. In summary, the investigations made have revealed imperfections in the pad plating, and it is recommended that a thicker or more even plating is achieved during the hot air levelling process at the printed circuit board manufacturing site so as to eliminate no/skipped solder defects that are induced by this printed circuit board deficiency.

Are PCB fabricators ready to fabricate MCM‐L technology?

Since the 1960s, interconnection technology has been dominated by implementations of printed circuit board (PCB) technology. However, in response to the ever increasing demand for higher routing densities and improved electrical performance, this technology has been increasingly challenged by multichip module (MCM) technology and in particular the MCM‐L type. MCM‐L technology is a laminate construction and is basically a further development of PCB technology with two or more bare chips and fine line interconnects. Consequently, it is perceived that the current PCB fabricators are ideally positioned to take the initiative with MCM‐L technology. Reviews the current state of PCB industry and MCM‐L technological (process and material) requirements, within the UK, such that a comparison can be made between the two technologies. Planning, training and investment requirements for new technology implementation are then identified and compared with PCB fabricators’ technological, training, planning and investment capabilities. The shortfalls between MCM‐L fabrication requirements and PCB fabricators capability are identified and discussed.

SURF: rubber-band routing system for multichip modules

Current PCB (printed circuit board)-based routing tools cannot meet the performance and cost constraints presented by today's packaging technologies, including thin-film multichip modules. The authors describe SURF, a routing system designed specifically to meet these challenges. The strength of the SURF system comes from its extremely flexible rubber-band data representation. The rubber-band model is an ideal framework for performance-driven and cost-driven routing and naturally supports rectilinear, octilinear, and all-angle wiring patterns: one-and-a-half-layer routing; even wiring distribution; and powerful manual editing. The integrated spoke-based design-rule-checking/enforcement mechanism supports an incremental design style. As objects are moved or wires are resized, the wires are adjusted incrementally so that they maintain the same wiring topology. By working in the topological domain instead of the geometrical one, the designer can focus on higher-level design issues while the tool handles the precise geometrical details.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>