Printed Circuit Board Manufacturing Process Research Articles

Local and Global Context-Enhanced Lightweight CenterNet for PCB Surface Defect Detection.

Printed circuit board (PCB) surface defect detection is an essential part of the PCB manufacturing process. Currently, advanced CCD or CMOS sensors can capture high-resolution PCB images. However, the existing computer vision approaches for PCB surface defect detection require high computing effort, leading to insufficient efficiency. To this end, this article proposes a local and global context-enhanced lightweight CenterNet (LGCL-CenterNet) to detect PCB surface defects in real time. Specifically, we propose a two-branch lightweight vision transformer module with local and global attention, named LGT, as a complement to extract high-dimension features and leverage context-aware local enhancement after the backbone network. In the local branch, we utilize coordinate attention to aggregate more powerful features of PCB defects with different shapes. In the global branch, Bi-Level Routing Attention with pooling is used to capture long-distance pixel interactions with limited computational cost. Furthermore, a Path Aggregation Network (PANet) feature fusion structure is incorporated to mitigate the loss of shallow features caused by the increase in model depth. Then, we design a lightweight prediction head by using depthwise separable convolutions, which further compresses the computational complexity and parameters while maintaining the detection capability of the model. In the experiment, the LGCL-CenterNet increased the mAP@0.5 by 2% and 1.4%, respectively, in comparison to CenterNet-ResNet18 and YOLOv8s. Meanwhile, our approach requires fewer model parameters (0.542M) than existing techniques. The results show that the proposed method improves both detection accuracy and inference speed and indicate that the LGCL-CenterNet has better real-time performance and robustness.

Surface Roughness Effect From Different Surfaces of Microstrip Lines and Reference Plane

Microstrip line structures consist of different conductors, such as trace and reference planes, which have different surface roughness levels due to the printed circuit board manufacturing process. The bottom surface of the trace is often rougher than the top surface of the trace, and the roughness levels of different reference planes vary for different foil types and manufacturing processes. To accurately model the additional conductor loss caused by such differences in microstrip lines, a new modeling method is proposed with different roughness levels on different surfaces and a reference plane, in contrast to the traditional roughness modeling approach, which considers a uniform roughness distribution for all surfaces. The effect of the different surfaces on the resistance is determined by applying additional microstrip models to analyze the effect of surface roughness from different surfaces and to improve the accuracy of insertion loss prediction based on the modeled total resistance.

A Novel Data Mining Approach for Defect Detection in the Printed Circuit Board Manufacturing Process

Abstract This research aims to propose an effective model for the detection of defective Printed Circuit Boards (PCBs) in the output stage of the Surface-Mount Technology (SMT) line. The emphasis is placed on increasing the classification accuracy, reducing the algorithm training time, and a further improvement of the final product quality. This approach combines a feature extraction technique, the Principal Component Analysis (PCA), and a classification algorithm, the Support Vector Machine (SVM), with previously applied Automated Optical Inspection (AOI). Different types of SVM algorithms (linear, kernels and weighted) were tuned to get the best accuracy of the resulting algorithm for separating good-quality and defective products. A novel automated defect detection approach for the PCB manufacturing process is proposed. The data from the real PCB manufacturing process were used for this experimental study. The resulting PCALWSVM model achieved 100 % accuracy in the PCB defect detection task. This article proposes a potentially unique model for accurate defect detection in the PCB industry. A combination of PCA and LWSVM methods with AOI technology is an original and effective solution. The proposed model can be used in various manufacturing companies as a postprocessing step for an SMT line with AOI, either for accurate defect detection or for preventing false calls.

Analysis of Uncertainties in Inductance of Multi-Layered Printed-Circuit Spiral Coils.

Eddy-current sensors are widely used for precise displacement sensing and non-destructive testing. Application of printed-circuit board (PCB) technology for manufacturing sensor coils may reduce the cost of the sensor and enhance the performance by ensuring consistency. However, these prospects depend on the uniformness of the sensor coil. Inductance measurements of sample coils reveal rather considerable variations. In this paper, we investigate the sources of these variations. Through image analysis of cut-away cross-sections of sensor coils, four factors that contribute to the inductance variations are identified: the distance between layers, the distance between tracings, cross-sectional areas, and misalignment among layers. By using and extending existing method of calculating inductance of spiral coils, the inductance distributions are obtained when these factors are randomly varied. A sensitivity analysis shows that the inductance uncertainty is most affected by the uniformness of the spacings between coil traces and the distances between layers. Improvements in PCB manufacturing process can help to reduce the uncertainty in inductance.

Effect of printed circuit board dust on the workability and mechanical properties of self-compacting concrete: A preliminary study

Electronic waste has had an adverse impact on the environment in this era of fast electronic technology advancement and rapid consumption growth. Therefore, awareness and focus on the sustainable disposal of electronic products should be raised. The objective of this research is to study the feasibility of using the dust from the printed circuit board manufacturing process (PCB dust) as a binder to replace ordinary Portland cement (OPC) for manufacturing of self-compacting concrete (SCC). All of the seven SCC mixtures were obtained by replacing OPC with PCB dust by the volume ratio of 0%, 5%, 10%, 15%, 20%, 25%, and 30% respectively, then the workability and the properties of hardened concrete were investigated. From the experimental results, it can be seen that the workability of SCC tends to decrease with the PCB dust replacing increases, and clear that SCC tends to block during the flow and segregate. The engineering properties of hardened concrete indicates that the efficiency decreases as the amount of PCB dust increases. The highest 28-day compressive strength obtained is about 54 MPa at 5% replacement level and tends to decrease between 11.49% and 57.44% at replacement level between 5% and 30% by volume, when compared to the control mix. However, when SCC is mixed with 20% of PCB dust, it can provide a compressive strength of more than 50 MPa after 180 days. The results of the study point out the possibility of recycling PCB dust as a new filler that can be utilized to reduce the consumption of natural materials.

Affordable Thin Lens Using Single Polarized Disparate Filter Arrays for Beyond 5G toward 6G.

This paper proposes a novel design approach for a thin lens with the aim of overcoming fineness limits in the commercial millimeter wave printed circuit board (PCB) manufacturing process. The PCB manufacturing process typically does not allow the fabrication of metallic patterns with a gap and width of less than 100 μm. This hampers expanding thin lens technology to 5G commercial applications, especially when such technology is considered for 60 GHz or higher frequency, which requires a finer gap and width of metallic traces. This paper proposes that problematic process conditions can be mitigated when a lens is designed by establishing single-polarized lumped element models where larger capacitance and inductance values can be obtained for the same patch and grid unit cells. While the proposed design technique is more advantageous at higher target frequencies, a 60 GHz application and a wireless backhaul system is selected because of a limited range of frequencies that can be measured by an available vector network analyzer. The required gap or width of metallic traces can be widened significantly by using the proposed single-polarized unit cells to acquire the same in-plane capacitance or inductance. This enables the lens operating at higher-frequency under the process limits in fabricable fine traces. Finally, the effectiveness of the simulated design procedure is demonstrated by fabricating a 60 GHz thin lens that can achieve a gain enhancement of 16 dB for a 4 × 4 patch antenna array with a gain of 16.5 dBi.

Influence of the PCB Manufacturing Process on the Measurement Error of Planar Relative Permittivity Sensors Up To 100 GHz

Accurate and precise knowledge of the relative permittivity of printed circuit board (PCB) materials is essential for the reliable design of high-frequency circuits. For simplicity reasons, planar, resonant permittivity sensors, which are directly integrated on the unknown PCB material, are widely used. However, the sensors are affected by the nonidealities of the copper-clad laminate and PCB manufacturing process, e.g., the difference in roughness between the top and bottom sides of each metal layer. This paper analyzes the influence of these nonidealities on the extracted relative permittivity values of different sensor geometries in microstrip and substrate integrated waveguide (SIW) technology up to 100 GHz. Microstrip resonators are very sensitive against the investigated nonidealities. Additional roughness measurements and more detailed simulation models cannot noticeably reduce the uncertainties. SIW cavity sensors are more robust, and simple modeling approaches lead to low uncertainties smaller than 0.05 for the whole frequency range from 10 to 100 GHz.

PCB Fault Detection Using Image Processing

The importance of the Printed Circuit Board inspection process has been magnified by requirements of the modern manufacturing environment where delivery of 100% defect free PCBs is the expectation. To meet such expectations, identifying various defects and their types becomes the first step. In this PCB inspection system the inspection algorithm mainly focuses on the defect detection using the natural images. Many practical issues like tilt of the images, bad light conditions, height at which images are taken etc. are to be considered to ensure good quality of the image which can then be used for defect detection. Printed circuit board (PCB) fabrication is a multidisciplinary process, and etching is the most critical part in the PCB manufacturing process. The main objective of Etching process is to remove the exposed unwanted copper other than the required circuit pattern. In order to minimize scrap caused by the wrongly etched PCB panel, inspection has to be done in early stage. However, all of the inspections are done after the etching process where any defective PCB found is no longer useful and is simply thrown away. Since etching process costs 0% of the entire PCB fabrication, it is uneconomical to simply discard the defective PCBs. In this paper a method to identify the defects in natural PCB images and associated practical issues are addressed using Software tools and some of the major types of single layer PCB defects are Pattern Cut, Pin hole, Pattern Short, Nick etc., Therefore the defects should be identified before the etching process so that the PCB would be reprocessed. In the present approach expected to improve the efficiency of the system in detecting the defects even in low quality images

Realization of a Low-Cost Displacement Sensor on PCB With Two-Metal-Layer Coplanar Waveguide Loaded by an EBG Structure

There are some difficulties in the realization of a microwave displacement sensor with conventional CPW loaded by electromagnetic bandgap structure on RF laminates with a regular printed circuit board manufacturing process. These difficulties have made this process impossible in practice. In this paper, for the first time, this kind of sensor has been implemented using a two-metal-layer (TML) CPW as a transmission line to overcome these difficulties. The proposed sensor consists of a TML CPW line loaded by two periodic-air-hole structures at both sides of the transmission line. Sliding the periodic structure at one side of the transmission line makes a change in the maximum insertion loss at the fundamental central frequency of the bandgap proportional to the length of the displacement. Analysis, finite-element method simulation, and fabrication have been carried out, and an average sensitivity of about 9 dB/mm and a dynamic range of 3 mm have been achieved for the 21 unit cells sensor with a period of 6 mm at 14.24 GHz. Furthermore, some practical issues, such as influence of the air gap between the metal traces and the movable structured dielectric on the sensor behavior and robustness of the sensor against the temperature variations, are practically investigated.

PCB Surface Fingerprints Based Counterfeit Detection of Electronic Devices

Nowadays counterfeit electronic devices are in wide circulation and cause huge financial losses to the industry. In this work, visually imperceptible random patterns on a printed circuit board (PCB) surface resulting from the PCB manufacturing process are investigated as the potential fingerprints for counterfeit detection of electronic devices. For device authentication, surface fingerprints are matched by computing the normalized cross-correlation. The experimental results show that the variations (e.g.small marks of random size, shape, orientation, shape distortions, texture, etc.) encountered in the interlayer connecting vias resulting from the PCB manufacturing process imperfections can be used as surface fingerprints for device authentication. For performance evaluation PCB surfaces with specially designed test patterns produced by industrial grade PCB manufacturing facilities are considered. Appropriate measures are suggested to address the challenges that are not yet addressed in this research work.

Substrate-integrated waveguide filters based on mushroom-shaped resonators

This paper presents a new class of quasi-elliptic pass-band filters in substrate-integrated waveguide technology, which exhibits compact size and modular geometry. These filters are based on mushroom-shaped metallic resonators, and they can be easily implemented using a standard dual-layer printed circuit board manufacturing process. The presented filters exploit non-resonating modes to obtain coupling between non-adjacent nodes in the case of in-line geometry. The resulting structure is very compact and capable of transmission zeros. In this work, the singlet configuration is preliminarily investigated, and a parametric study is performed. The design of three-pole, four-pole, and higher-order filters is illustrated with examples and thoroughly discussed. A four-pole filter operating at the frequency of 4 GHz has been manufactured and experimentally verified, to validate the proposed technique.

Realistic warpage evaluation of printed board assembly during reflow process

Purpose – This paper aims to develop an estimation tool for warpage behavior of slim printed circuit board (PCB) array while soldering with electronic components by using finite element method. One of the essential requirements for handheld devices, such as smart phone, digital camera, and Note-PC, is the slim design to satisfy the customers’ desires. Accordingly, the printed circuit board (PCB) should be also thinner for a slim appearance, which would result in decreasing the PCB’s bending stiffness. This means that PCB deforms severely during the reflow (soldering) process where the peak temperature goes up to 250°C. Therefore, it is important to estimate PCB deformation at a high temperature for thermo-mechanical quality/reliability after reflow process. Design/methodology/approach – A numerical simulation technique was devised and customized to accurately estimate the behavior of a thin printed board assembly (PBA) during reflow by considering all components, including PCB, microelectronic packages and solder interconnects. Findings – By applying appropriate constraints and boundary conditions, it was found that PBA’s warpage can be accurately predicted during the reflow process. The results were also validated by warpage measurement, which showed a fairly good agreement with one and another. Research limitations/implications – For research limitations, there are many assumptions regarding numerical modeling. That is, the viscoplastic material property of solder ball is ignored, the reflow profile is simplified and the accurate heat capacity is not considered. Furthermore, the residual stress within the PCB, generated at PCB manufacturing process, is not included in this paper. Practical implications – This paper shows how to calculate PBA warpage during the reflow process as accurately as possible. This methodology helps a PCB designer and surface-mount technology (SMT) process manager to predict a PBA warpage issue and modify PCB design before PCB real fabrication. Practically, this modeling and simulation process can be easily performed by using a graphical user interface (GUI) module, so that the engineer can handle an issue by inputting some numbers and clicking some buttons. Social implications – In a common sense manner, a numerical simulation method can decrease time and cost in manufacturing real samples. This PCB warpage method can also decrease product development duration and produce a new product earlier. Furthermore, PCB is a common component in all the electronic devices. So, this PCB warpage method can have various applications. Originality/value – Because of an economic advantage, the development of a numerical simulation tool for estimating the thin PBA warpage behaviour during reflow process was attempted. The developed tool contains the features of detailed modeling for electronic components and contact boundary conditions of the supporting rails in the reflow oven.

Reliability Failure Analysis of PCB and its Technological Improvement

Reliability failure analysis is extremely important in the manufacturing process of PCB (Printed Circuit Board). In this paper, we use thermal shock test method to analysis the electrical interconnection reliability of PCB in harsh environment. Also taking into account the reliability of PCB is closely related to its design and technology, approaches of technological improvement are proposed. Finally through temperature shock test method, the results show that the reliability of PCB designed with improved technology is enhanced.

A High Slow-Wave Factor Microstrip Structure With Simple Design Formulas and Its Application to Microwave Circuit Design

This paper proposes a new microstrip slow-wave structure. The unit cell comprises a Schiffman section of meander line and a shunt open-circuited stub. No via-holes and ground-plane patterns are required. Simple design formulas can be used to obtain line parameters, such as the characteristic impedance and phase velocity. According to the analysis, the characteristic impedance and slow-wave factor of the proposed slow-wave line can be independently controlled by merely two layout parameters. The proposed uniplanar structure only requires a single-layer substrate and is simply constructed using the conventional printed circuit board manufacturing process. A branch-line and a rat-race coupler were designed and fabricated using the proposed structure to demonstrate its feasibility. Their sizes are only 8.49% and 4.87% of the conventional ones, respectively. This novel slow-wave structure should find wide applications in compact microwave circuits.

Main aspects concerning PCB manufacturing optimization

PurposeThe purpose of this paper is to outline the main features concerning the optimization of printed circuit board (PCB) fabrication by improving the manufacturing process productivity.Design/methodology/approachThe author explored two different approaches to increase the manufacturing process productivity of PCBs. The first approach involved optimization of the PCB manufacturing process as a whole. The second approach was based on increasing the process productivity at the operational level.FindingsTo reduce the total manufacturing time, two heuristic algorithms for solving flowshop scheduling problems were designed. These algorithms were used for the computation of an optimal PCB manufacturing schedule. The case study shows both mono‐ and bi‐criteria optimization of the PCBs manufacturing.Research limitations/implicationsWhile the input data used in the case study were based on random numbers, the mathematical considerations drew only the main directions for manufacturing process optimization.Originality/valueThe paper shows two original heuristic algorithms for solving the flowshop scheduling problem, with high performance according to the best heuristics in the field. Besides their performances, these algorithms have the advantage of simplicity and ease of implementation on a computer. Using these algorithms, the optimal schedule for the PCB manufacturing process was calculated. For the case of the bi‐criteria optimization, the study of points which belong to the Pareto‐optimal set are presented.

Application of Genetic Algorithms in the Optimization of the Drilling Path on the Printed Circuit Board

Efficient production of PCB is the electronic industry’s needs, while drilling is an important part in the printed circuit board manufacturing process. The drilling path optimization is crucial for improving the efficiency. Inspired by the shortest path algorithm, this paper used genetic algorithm for solving the shortest to optimal path selection of PCB drilling process and find the best path according to the specific circumstances of PCB drilling to achieve high efficiency drilling. The algorithm which has been used in the different points for practice is proved to be reasonable and efficient. The method can be optimized for fast global search, greatly reducing the computation, it is robust, efficient, can be a good solution for PCB drilling path optimization problem.

Adhesion Improvement on Smooth Cu Wiring Surfaces of Printed Circuit Boards

A novel Cu surface treatment method was developed to improve the adhesion between smooth Cu surfaces and epoxy dielectric layers using a silane coupling agent. In this process, the Cu surface was first modified with a functional group, which was then treated with the silane coupling agent. Here, we investigated the effect of the functional group and the silane coupling agent on the adhesion strength between Cu and epoxy dielectric layers. We also investigated the influence of the Cu/dielectric adhesion layer on smooth Cu wirings of the printed circuit board manufacturing process compatibility. From this study, it was found that two-step Cu surface modification with triazine trithiol followed by treatment of mercapto-group containing silane coupling agent would dramatically enhance the adhesion strength. It was found that a thin triazine trithiol layer was very effective to improve desmear-resistance.

Energy conservation and related best practices in printed circuit board (PCB) manufacturing

PurposeThe purpose of this paper is to present the details of key best practices that can help printed circuit board (PCB) manufacturing companies to optimize energy consumption, conserve materials, and reduce waste and costs.Design/methodology/approachVarious individual opportunities for making energy saving are discussed along with the accompanying manufacturing best practices.FindingsThere are many opportunities to reduce energy consumption across the whole PCB manufacturing process. Additional savings may also be made by enhancements to the broader activities within PCB manufacturing plants.Research limitations/implicationsThe paper summarises key findings that have been reported in a much larger Best Practice Guide and due to space considerations the amount of information given is somewhat restricted.Originality/valueThe paper details how the introduction of best practices in each stage of the PCB manufacturing process can lead to material and energy savings that have value in helping board makers to reduce costs. Readers are directed to a larger Best Practice Guide which is freely available from the SurfEnergy web site.

Stripping of organic compounds from wastewater as an auxiliary fuel of regenerative thermal oxidizer

Organic solvents with different volatilities are widely used in various processes and generate air and water pollution problems. In the cleaning processes of electronics industries, most volatile organic compounds (VOCs) are vented to air pollution control devices while most non-volatile organic solvents dissolve in the cleaning water and become the major sources of COD in wastewater. Discharging a high-COD wastewater stream to wastewater treatment facility often disturbs the treatment performance. A pretreatment of the high-COD wastewater is therefore highly desirable. This study used a packed-bed stripping tower in combination with a regenerative thermal oxidizer to remove the COD in the wastewater from a printed circuit board manufacturing process and to utilize the stripped organic compounds as the auxiliary fuel of the RTO. The experimental results showed that up to 45% of the COD could be removed and 66% of the RTO fuel could be saved by the combined treatment system.

New chemical process waste treatment technologies for a sustainable printed circuit board manufacturing process

The Printed Circuit Board (PCB) manufacturing process uses large quantities of water and a wide range of chemicals. If not handled responsibly, many of these materials may ultimately have an impact on the environment or at best generate effluent that needs increasingly costly treatment. There is an opportunity to move towards a more sustainable methodology where waste is minimised, water is recycled and materials are recovered. This paper presents the results from work aimed at enabling PCB manufacturing to become more sustainable. Novel processes evaluated include special electroplating techniques, advanced oxidation methods to remove organic contaminants, and new ion exchange systems. Work has been carried out to develop these processes into viable demonstrators and the results of progress to date are reported. Descriptions of how these individual technologies may be combined to provide an integrated approach to a more sustainable PCB manufacturing methodology are also given.