Search

In this paper, we present a novel polylactic-acid/flax-composite substrate and the implementation of a demonstrator: a microcontroller board based on commercial design. The substrate is developed for printed circuit board (PCB) applications. The pre-preg is biodegradable, reinforced, and flame-retarded. The novel material was developed to counter the increasing amount of e-waste and to improve the sustainability of the microelectronics sector. The motivation was to present a working circuit in commercial complexity that can be implemented on a rigid substrate made of natural, bio-based materials with a structure very similar to the widely used Flame Retardant Class 4 (FR4) substrate at an early technological readiness level (2–3). The circuit design is based on the Arduino Nano open-source microcontroller board design so that the demonstration could be programmable and easy to fit into education, IoT applications, and embedded designs. During the work, the design was optimized at the level of layout. The copper-clad pre-preg was then prepared and processed with subtractive printed wiring technology and through hole plating. The traditional surface mounting methodology was applied for assembly. The resulting yield of PCB production was around 50%. Signal analysis was successful with analogue data acquisition (voltage) and low-frequency (4 kHz) tests, indistinguishable from sample FR4 boards. Eventually, the samples were subjected to highly accelerated stress test (HAST). HAST tests revealed limitations compared to traditional FR4 printed circuit materials. After six cycles, the weight loss was around 30% in the case of PLA/Flax, and as three-point bending tests showed, the possible ultimate strength (25 MPa at a flexural state) was reduced by 80%. Finally, the sustainability aspect was assessed, where we found that ∼95 vol% and ∼90 wt% of the traditional substrate can be substituted, significantly easing the load of waste on the environment. [ABSTRACT FROM AUTHOR]

Due to the continuous increase in the globalized outsourcing of printed circuit board (PCB) fabrication, PCB counterfeits have increased by a significant margin, necessitating rapid and advanced hardware assurance techniques. PCB image segmentation is the primary step in PCB assurance. Over the years, few PCB component segmentation methods have been proposed, and none of those has provided a definite performance benchmark. Besides, those methods have not discussed how the performance is correlated with underlying data or annotation quality. This work presents a PCB image segmentation benchmark. In addition, we explore how annotation quality affects component segmentation and present possible future research directions to work with coarse annotations to alleviate the human effort behind full data annotation tasks. We have analyzed the performance of the preferred deep neural network (DNN) architecture and Transformer architecture with the data annotation quality and presented the direction to leverage the outcome with limited quality annotations. Finally, we present the qualitative as well as the quantitative results to demonstrate the performance of our techniques and provide observations and future research directions on the overall task. [ABSTRACT FROM AUTHOR]

The EPFL Spacecraft Team (EST) is working on the Constellation of High-Performance Exospheric Science Satellites (CHESS) mission, which aims to launch a constellation of two CubeSats in 2027. These CubeSats will study the chemical composition of Earth's exosphere using time-of-flight mass spectrometry. To downlink the collected scientific data, the satellites will utilise a custom X-band transceiver, presented in this paper, operating in the amateur frequency range of 10.45 GHz to 10.50 GHz. The proposed transceiver architecture employs Software-Defined Radio (SDR) technology and can be easily adapted for different use cases. This modular approach has the potential to be suitable for future spacecraft missions, such as active debris removal or lifetime extension services, where flexible communication systems are required. • Hybrid SDR architectures enable versatile telecom systems for space missions. • IOD/IOV missions let students follow the entire life cycle of a space project. • Short development/prototyping cycles maximise the lessons learned in student teams. [ABSTRACT FROM AUTHOR]

Printed circuit boards (PCBs) provide stable connections between electronic components. However, defective printed circuit boards may cause the entire equipment system to malfunction, resulting in incalculable losses. Therefore, it is crucial to detect defective printed circuit boards during the generation process. Traditional detection methods have low accuracy in detecting subtle defects in complex background environments. In order to improve the detection accuracy of surface defects on industrial printed circuit boards, this paper proposes a residual large kernel network based on YOLOv5 (You Only Look Once version 5) for PCBs surface defect detection, called YOLO-RLC (You Only Look Once-Residual Large Kernel). Build a deep large kernel backbone to expand the effective field of view, capture global information more efficiently, and use 1 1 convolutions to balance the depth of the model, improving feature extraction efficiency through reparameterization methods. The neck network introduces a bidirectional weighted feature fusion network, combined with a brand-new noise filter and feature enhancement extractor, to eliminate noise information generated by information fusion and recalibrate information from different channels to improve the quality of deep features. Simplify the aspect ratio of the bounding box to alleviate the issue of specificity values. After training and testing on the PCB defect dataset, our method achieved an average accuracy of 97.3% (mAP50) after multiple experiments, which is 4.1% higher than YOLOv5-S, with an average accuracy of 97.6% and an Frames Per Second of 76.7. The comparative analysis also proves the superior performance and feasibility of YOLO-RLC in PCB defect detection. [ABSTRACT FROM AUTHOR]

This study investigates the effects of sodium dodecyl sulfate (SDS) and polyethylene glycol (PEG) on the galvanic corrosion behavior of copper (Cu) coupled to gold (Au) in a printed circuit board (PCB) etching solution. Galvanic corrosion tests using ZRA (zero resistance ammeter) were performed to determine the optimal SDS concentration for corrosion inhibition. The corrosion current between Cu and Au decreased significantly with the addition of SDS, from 3.26 mA/cm2 to 0.248 mA/cm2 at 4 mM SDS, achieving an inhibitor efficiency (IE) of 92.3%. However, at 15 mM SDS, the corrosion current increased, and IE decreased to 80.5%. This phenomenon is attributed to the critical micelle concentration (CMC) of SDS, where surfactant molecules aggregate and reduce surface adsorption properties. Similarly, ZRA tests were conducted to analyze the effects of PEG on galvanic corrosion. The corrosion current significantly decreased with PEG addition, achieving 98.1% IE at 1 g/L and 99.5% IE at 2 g/L. Beyond this concentration, no significant change in IE was observed, indicating saturation. Potentiodynamic polarization tests were also conducted to study the individual effects of SDS and PEG on Cu and Au. The results showed that SDS effectively inhibited Cu corrosion but had a minimal impact on Au. In contrast, PEG significantly reduced the corrosion current density for both Cu and Au, with reductions of 99.5% and 95.1%, respectively. [ABSTRACT FROM AUTHOR]

The growing amount of electronic waste is a global challenge: on one hand, it poses a threat to the environment as it may contain toxic or hazardous substances, on the other hand it is a valuable 'urban mine' containing metals like gold and copper. Thus, recycling of electronic waste is not only a measure to reduce environmental pollution but also economically reasonable as prices for raw materials are rising. Within electronic waste, printed circuit boards (PCBs) occupy a prominent position, as they contain most of the valuable material. One important step in the overall recycling process is the evaluation and the value estimation for further treatment of the waste PCBs (WPCBs). In this article, we introduce a method for value estimation of entire WPCBs based on component detection. The value of the WPCB is then predicted by the value of the detected components. This approach allows a flexible application to different situations. In the first step, we created a dataset and labelled the components of 104 WPCBs using different component classes. The component detection is performed on dual energy X-ray images by the deep neural object detection network 'YOLO v5'. The dataset is split into a training, validation and test subset and standard performance measures as precision, recall and F1-score of the component detection are evaluated. Representative samples from all component classes were selected and analysed for the valuable materials to provide the ground truth of the value estimation in the subsequent step. [ABSTRACT FROM AUTHOR]

This study focuses on the effects of reducing the diameter of rivets used in Friction Riveting due to the need for downscaling when joining assemblies on a smaller scale. The Friction Riveting process has shown promising feasibility for a variety of material combinations and applications in the transportation industry. Recent research has explored the potential application of this technique in electronics, specifically for the assembly of printed circuit boards (PCBs), using AA-2024-T351 rivets on thin glass-fiber-reinforced epoxy substrates (FR4). The joint formation of joints produced with PCBs was investigated in terms of process temperature evolution, microstructural changes, and mechanical properties. Joints were obtained at process temperatures ranging from 285 ºC to 368 ºC. The use of 4 mm rivets resulted in extensive delamination, weak joint mechanisms, and cracking, impaired by the different coefficients of thermal expansion of the materials involved. Reducing the rivet diameter to 3 mm significantly improved joint quality. A further reduction to 2.5 mm minimized delamination but led to insufficient anchorage and cracking. Joints produced with a 3 mm rivet diameter achieved the highest ultimate tensile force of 276 N. This study sets the foundation for applying the Friction Riveting process to practical PCB assemblies, demonstrating that optimizing the process parameters to the diameter-to-thickness ratio can balance sufficient rivet anchoring, minimize delamination, and reduce cracking. [ABSTRACT FROM AUTHOR]

Removing polychlorinated biphenyls (PCBs) from the environment is an important process for the protection of biota. This work examines three different approaches to the degradation of such contaminants. The first involves the use of iron bionanoparticles (Fe-BNPs) prepared through green synthesis from selected plant matrices. The second approach entails the use of the bacteria Stenotrophomonas maltophilia (SM) and Ochrobactrum anthropi (OA) isolated from a PCB-contaminated area, Strážsky canal, located in the Slovak republic, which receives efflux of canal from Chemko Strážske plant, a former producer of PCB mixtures. The third approach combines these two methods, employing a sequential hybrid two-step application of Fe-BNPs from the plant matrix followed by the application of bacterial strains. Fe-BNPs are intended to be an eco-friendly alternative to synthetic nanoscale zero-valent iron (nZVI), which is commonly used in many environmental applications. This work also addresses the optimization parameters for using nZVI in PCB degradation, including the pH of the reaction, oxygen requirements, and dosage of nZVI. Pure standards of polyphenols (gallic acid, GA) and flavonoids (quercetin, Q) were tested to produce Fe-BNPs using green synthesis at different concentrations (0.1, 0.3, 0.5, 0.8, and 1 g.L−1) and were subsequently applied to the PCB degradation experiments. This step monitored the minimum content of bioactive substances needed for the synthesis of Fe-BNPs and their degradation effects. Experimental analysis indicated that among the selected approaches, sequential nanobiodegradation appears to be the most effective for PCB degradation, specifically the combination of Fe-BNPs from sage and bacteria SM (75% degradation of PCBs) and Fe-BNPs from GA (0.3 g.L−1) with bacteria OA (92% degradation of PCBs). [ABSTRACT FROM AUTHOR]

Objective: The aim was to evaluate the possible association between some endocrine disruptive chemicals and thyroid cancer (TC) in an Italian case–control cohort. Methods: We enrolled 112 TC patients and 112 sex- and age-matched controls without known thyroid diseases. Per- and poly-fluoroalkyl substances (PFAS), poly-chlorinated biphenyls (PCBs), and dichlorodiphenyltrichloroethane (4,4′-DDT and 4,4′-DDE) were measured in the serum by liquid or gas chromatography–mass spectrometry. Unconditional logistic regression, Bayesan kernel machine regression and weighted quantile sum models were used to estimate the association between TC and pollutants’ levels, considered individually or as mixture. BRAFV600E mutation was assessed by standard methods. Results: The detection of perfluorodecanoic acid (PFDA) was positively correlated to TC (OR = 2.03, 95% CI: 1.10–3.75, P = 0.02), while a negative association was found with perfluorohexanesulfonic acid (PFHxS) levels (OR = 0.63, 95% CI: 0.41–0.98, P = 0.04). Moreover, perfluorononanoic acid (PFNA) was positively associated with the presence of thyroiditis, while PFHxS and perfluorooctane sulfonic acid (PFOS) with higher levels of presurgical thyroid-stimulating hormone (TSH). PFHxS, PFOS, PFNA, and PFDA were correlated with less aggressive TC, while poly-chlorinated biphenyls (PCB-105 and PCB-118) with larger and more aggressive tumors. Statistical models showed a negative association between pollutants’ mixture and TC. BRAFV600E mutations were associated with PCB-153, PCB-138, and PCB-180. Conclusion: Our study suggests, for the first time in a case–control population, that exposure to some PFAS and PCBs associates with TC and some clinical and molecular features. On the contrary, an inverse correlation was found with both PFHxS and pollutants’ mixture, likely due to a potential reverse causality.

BACKGROUND: The rapid development of industrialization in printed circuit board (PCB) warrants more complexity and integrity, which entails an essential procedure of PCB inspection. X-ray computed laminography (CL) enables inspection of arbitrary regions for large-sized flat objects with high resolution. PCB inspection based on CL imaging is worthy of exploration. OBJECTIVE: This work aims to extract PCB circuit layer information based on CL imaging through image segmentation technique. METHODS: In this work, an effective and applicable segmentation model for PCB CL images is established for the first time. The model comprises two components, with one integrating edge diffusion and l0 smoothing to filter CL images with aliasing artifacts, and the other being the fuzzy energy-based active contour model driven by local pre-fitting energy to segment the filtered images. RESULT: The proposed model is able to suppress aliasing artifacts in the PCB CL images and has good performance on images of different circuit layers. CONCLUSIONS: Results of the simulation experiment reveal that the method is capable of accurate segmentation under ideal scanning condition. Testing of different PCBs and comparison of different segmentation methods authenticate the applicability and superiority of the model. [ABSTRACT FROM AUTHOR]

Electronic components are the main components of PCBs (printed circuit boards), so the detection and classification of ECs (electronic components) is an important aspect of recycling used PCBs. However, due to the variety and quantity of ECs, traditional target detection methods for EC classification still have problems such as slow detection speed and low performance, and the accuracy of the detection needs to be improved. To overcome these limitations, this study proposes an enhanced YOLO (you only look once) network (EC-YOLOv7) for detecting EC targets. The network uses ACmix (a mixed model that enjoys the benefits of both self-attention and convolution) as a substitute for the 3 × 3 convolutional modules in the E-ELAN (Extended ELAN) architecture and implements branch links and 1 × 1 convolutional arrays between the ACmix modules to improve the speed of feature retrieval and network inference. Furthermore, the ResNet-ACmix module is engineered to prevent the leakage of function data and to minimise calculation time. Subsequently, the SPPCSPS (spatial pyramid pooling connected spatial pyramid convolution) block has been improved by replacing the serial channels with concurrent channels, which improves the fusion speed of the image features. To effectively capture spatial information and improve detection accuracy, the DyHead (the dynamic head) is utilised to enhance the model's size, mission, and sense of space, which effectively captures spatial information and improves the detection accuracy. A new bounding-box loss regression method, the WIoU-Soft-NMS method, is finally suggested to facilitate prediction regression and improve the localisation accuracy. The experimental results demonstrate that the enhanced YOLOv7 net surpasses the initial YOLOv7 model and other common EC detection methods. The proposed EC-YOLOv7 network reaches a mean accuracy (mAP@0.5) of 94.4% on the PCB dataset and exhibits higher FPS compared to the original YOLOv7 model. In conclusion, it can significantly enhance high-density EC target recognition. [ABSTRACT FROM AUTHOR]

In this paper, a triband bandpass filter has been proposed for millimeter wave and 5G applications. The filter design is progressed using a complementary spiral resonator superimposed on a hexagonal patch measuring about 7 mm × 4.2 mm × 0.8 mm. employing Rogers 5880 as substrate with εr = 2.2. This triband filter is highly selective with sharp rejections emulating bandwidths of about 1.3 GHz, 2.5 GHz, and 1.8 GHz capable of supporting millimeter wave and 5G communications. The qualifying parameters of filter-like insertion loss have been realized between −0.6 dB and −0.16 dB and return loss between −19.12 dB and −28 dB for the corresponding three bands. Moreover, the performance attainment of the filter has been verified from the surface current distribution of the filter. The filter resonates at millimeter wave frequencies of 29.6 GHz, 32.5 GHz, and 35.8 GHz portraying a triband response. The simulated and measured results substantiated very well with each other. [ABSTRACT FROM AUTHOR]

In order to improve the efficiency and accuracy of multitarget detection of soldering defects on surface-mounted components in Printed Circuit Board (PCB) fabrication, we propose a sample generation method using Stable Diffusion Model and ControlNet, as well as a defect detection method based on the Swin Transformer. The method consists of two stages: First, high-definition original images collected in industrial production and the corresponding prompts are input to Stable Diffusion Model and ControlNet for automatic generation of nonindependent samples. Subsequently, we integrate Swin Transformer as the backbone into the Cascade Mask R-CNN to improve the quality of defect features extracted from the samples for accurate detection box localization and segmentation. Instead of segmenting individual components on the PCB, the method inspects all components in the field of view simultaneously over a larger area. The experimental results demonstrate the effectiveness of our method in scaling up nonindependent sample datasets, thereby enabling the generation of high-quality datasets. The method accurately recognizes targets and detects defect types when performing multitarget inspection on printed circuit boards. The analysis against other models shows that our improved defect detection and segmentation method improves the Average Recall (AR) by 2.8% and the mean Average Precision (mAP) by 1.9%. [ABSTRACT FROM AUTHOR]

Aiming at the problems of low accuracy and slow detection rate of existing target detection algorithms for PCB defect detection, and too many parameters of algorithm model leading to the inability to deploy on mobile terminals, a PCB defect detection algorithm based on MSD-YOLOv5 is proposed. Firstly, to ensure both detection accuracy and speed while reducing the model's size,we combine the lightweight MobileNet-v3 network with the CSPDarknet53 network. Further,the attention mechanism is introduced to highlight the important feature channels and weaken the less useful ones, so as to improve the feature extraction ability of the network. Finally, the coupling detection head is replaced with a decoupling detection head, and the defect location information and category information on the PCB are extracted and learned respectively, which solves the problem of highly coupling of different information feature distributions and enhances the generalization ability of the model. We conduct experiments on a publicly available PCB defect dataset from Peking University using this algorithm. The results show that the proposed method reduces the parameters of YOLOv5 model by 46% and improves the detection accuracy by 3.34%. [ABSTRACT FROM AUTHOR]

This review summarises our two decades of polychlorinated biphenyl (PCB) monitoring in different marine organisms along the eastern Adriatic Sea. The aim was to gain an insight into the trends of PCB distribution in order to evaluate the effectiveness of past and current legislation and suggest further action. Here we mainly focus on PCB levels in wild and farmed Mediterranean mussels, wild and farmed bluefin tuna, loggerhead sea turtles, common bottlenose dolphins, and small pelagic fish. The use of artificial intelligence and advanced statistics enabled an insight into the influence of various variables on the uptake of PCBs in the investigated organisms as well as into their mutual dependence. Our findings suggest that PCBs in small pelagic fish and mussels reflect global pollution and that high levels in dolphins and wild tuna tissues raise particular concern, as they confirm their biomagnification up the food chain. Therefore, the ongoing PCB monitoring should focus on predatory species in particular to help us better understand PCB contamination in marine ecosystems in our efforts to protect the environment and human health.

This paper discusses the development of desktop applications for traceability systems. The application was developed to facilitate data recording and tracking in an electronics manufacturing company's storage process of Printed Circuit Board (PCB) products. The application is developed using the Visual Basic language and Microsoft Excel databases. Additionally, the application is integrated with a barcode scanner to simplify the data entry process from PCBs and employee ID cards. Through the trial process conducted on the developed application, it has generally functioned in accordance with the development goals. Program control validation has been tested through several application access attempts from users registered as operators and administrators. The application has successfully recorded data from inbound and outbound processes, demonstrating storage and tracking functionality. Furthermore, the application has displayed the actual status data of the PCBs present in the warehouse. In terms of user satisfaction, seven users stated that this application was effective and efficient compared to the manual data recording process previously used by the company. This result was obtained from a questionnaire after the application was implemented in the company warehouse.

With the constant advancement of electronic science and technology, accurate failure analysis has become crucial to meeting stringent quality standards in surface mount (SMT) products. Reflow soldering is commonly used in the SMT industry due to its efficiency and low failure rate. However, visual inspection is limited, especially for ball grid array (BGA) joints, requiring X-ray techniques for complete, non-destructive analysis. Although X-ray image analysis algorithms have been employed to improve defect detection, some still need to meet quality requirements, resulting in additional manual inspections. The high dimensionality and variations in X-ray images present additional challenges for detection algorithms. This study proposes a new computer-assisted inspection approach to accurately detect flaws in solder joints of SMD components using an X-ray scanning system. This approach aims to improve image interpretation and reduce workload manual. X-ray technology applied to BGA seeks to improve the accuracy of image analysis, enabling the detection of various faults, such as BGA ball connections, interconnections on printed circuit boards, and filling faults. [ABSTRACT FROM AUTHOR]

Today's unique assembly challenges are comprised of complex printed circuit board (PCB) panelization, involving identical PCBs with a goal of increased production capability, due to a reduced footprint of the production floor. Identical PCBs that are within the same panel, with uniform spacing in an array or carrier, need to be dispensed at the same time. All these high-mix challenges have gone mainstream and affect real productivity and throughput. Existing manual dual-head dispensing systems do not consider the rotational correction for the second head, which leads to yield loss. To eliminate the yield loss on the second head, there is a mini XY drive system incorporated that provides fast and accurate dispensing to double the process capabilities over the same work area. Dynamic dual-head (DDH) dispensing uses a unique mini XY drive system on the left head, mounted on a separate Z-axis, to dynamically control the position of the head for accurately aligning to a second part, while synchronously dispensing both parts. The machine vision system performs the substrate alignment for each identical PCB that is individually placed in a carrier, which provides greater potential for variation in offset and skew. During synchronous dispensing for the second part with the DDH all the kinematic adjustment is performed with calculated values, from the skew angle and scaling factor. This technique guarantees increased productivity whilst maintaining yields through unsurpassed accuracy. DDH also provides the same level of adjustment and rotational correction for all step and repeated PCBs, flex circuits, and panel designs. If a product contains an odd number of units, then either of the heads can be programmed for dispensing while the others cannot. This paper examines proven methods to determine the dot/line positional accuracy along with the mass flow rate for both heads during synchronous dispensing. This paper will also address the challenges faced, and how the rotational correction can achieve up to 23 higher throughput than existing single/dual head dispensing systems. [ABSTRACT FROM AUTHOR]

Soft lithography has long remained the state of the art to generate the necessary micropatterning for molded microfluidic (MF) chips. Previous attempts to use printed circuit boards (PCBs) as a cheap and accessible alternative to expensive lithographed molds for the production of PDMS MF chip prototypes have shown their limitations. A more in-depth exploration of using PCBs as a mold substrate and a novel methodology of using flexible PCBs to produce highly accurate MF chips is reported here for the first time. Cross sections highlight the improved accuracy of this method, and peel testing is performed to demonstrate suitable adhesion between the glass substrate and PDMS cast. Positive cell growth viability showcases this novel method as a high-accuracy, high-accessibility, low-cost prototyping method for microfluidic chips while still maintaining all favorable properties provided by the PDMS material. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are persistent organic pollutants in the environment that are responsible for many adverse health effects. Bioremediation appears to be a healthy and cost-effective alternative for remediating PCB-contaminated environments. While some microbial species have been observed to be capable of transforming PCBs, only two different microbial pathways (rdh and bph pathways) have been described to be involved in PCB transformations. Ligninolytic enzymes have been observed or are under suspicion in some microbial PCB transformations. However, the role of these promising PCB-transforming enzymes, which are produced by fungi and some aerobic bacteria, is still unclear. The present review describes their role by identifying microbial PCB-transforming species and their reported ligninolytic enzymes whether proven or suspected to be involved in PCB transformations. There are several lines of evidence that ligninolytic enzymes are responsible for PCB transformations such as (1) the ability of purified laccases from Myceliophthora thermophila, Pycnoporus cinnabarinus, Trametes versicolor, Cladosporium sp, and Coprinus cumatus to transform hydroxy-PCBs; (2) the increased production of laccases and peroxidases by many fungi in the presence of PCBs; and (3) the enhanced PCB transformation by Pseudomonas stutzeri and Sinorhizobium meliloti NM after the addition of ligninolytic enzyme enhancers. However, if the involvement of ligninolytic enzymes in PCB transformation is clearly demonstrated in some fungal species, it does not seem to be implicated in all microbial species suggesting other still unknown metabolic pathways involved in PCB transformation and different from the bph and rdh pathways. Therefore, PCB transformation may involve several metabolic pathways, some involving ligninolytic enzymes, bph or rdh genes, and some still unknown, depending on the microbial species. In addition, current knowledge does not fully clarify the role of ligninolytic enzymes in PCB oxidation and dechlorination. Therefore, further studies focusing on purified ligninolytic enzymes are needed to clearly elucidate their role in PCB transformation. [ABSTRACT FROM AUTHOR]

From 2010 to 2022, the summed concentrations of six indicator polychlorinated biphenyls (∑6PCB) and DDT with metabolites DDE and DDD (∑DDT) in the surface layer of the coastal Black Sea areas of Crimea varied from 0.05 to 34.9 and from 0.01 to 7.44 ng/L, respectively. The maximum concentrations of both groups of compounds were found during spring seasons. With the total variability in the ∑DDT content in water being significant, their average concentration tended to decrease in the study period. For PCBs, this trend was not detected. The ∑DDT concentration in mesozooplankton in the studied water areas in 2016, 2017, and 2019 reached 34.3; ∑6PCB, 475 ng/g dry weight. A positive correlation between the ∑DDT concentration in mesozooplankton and water samples (R 2 = 0.77) and the lack of such correlation for ∑PCB (R 2 = 0.03) was revealed. It was determined that the accumulation of ∑PCB and ∑DDT in mesozooplankton was directly correlated with the total lipid content in organisms. In the surface layer of sediments in open areas of the Black Sea water area of Crimea, the content of PCB congeners 101, 138, 153, and 180 was the same in 2016 and 2019, which indicates stabilization of the technogenic load on the studied water areas. [ABSTRACT FROM AUTHOR]

Copyright of Archives of Industrial Hygiene & Toxicology / Arhiv za Higijenu Rada I Toksikologiju is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Direct 3D printing of active microfluidic elements on PCB substrates enables high-speed fabrication of stand-alone microdevices for a variety of health and energy applications. Microvalves are key components of microfluidic devices and liquid metal (LM) microvalves exhibit promising flow control in microsystems integrated with PCBs. In this paper, we demonstrate LM microvalves directly 3D printed on PCB using advanced digital light processing (DLP). Electrodes on PCB are coated by carbon ink to prevent alloying between gallium-based LM plug and copper electrodes. We used DLP 3D printers with in-house developed acrylic-based resins, Isobornyl Acrylate, and Diurethane Dimethacrylate (DUDMA) and functionalized PCB surface with acrylic-based resin for strong bonding. Valving seats are printed in a 3D caterpillar geometry with chamber diameter of 700 µm. We successfully printed channels and nozzles down to 90 µm. Aiming for microvalves for low-power applications, we applied square-wave voltage of 2 Vpp at a range of frequencies between 5 to 35 Hz. The results show precise control of the bistable valving mechanism based on electrochemical actuation of LMs. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are persistent organic toxicants derived from legacy pollution sources and their formation as inadvertent byproducts of some current manufacturing processes. Metabolism of PCBs is often a critical component in their toxicity, and relevant metabolic pathways usually include their initial oxidation to form hydroxylated polychlorinated biphenyls (OH-PCBs). Subsequent sulfation of OH-PCBs was originally thought to be primarily a means of detoxication; however, there is strong evidence that it may also contribute to toxicities associated with PCBs and OH-PCBs. These contributions include either the direct interaction of PCB sulfates with receptors or their serving as a localized precursor for OH-PCBs. The formation of PCB sulfates is catalyzed by cytosolic sulfotransferases, and, when transported into the serum, these metabolites may be retained, taken up by other tissues, and subjected to hydrolysis catalyzed by intracellular sulfatase(s) to regenerate OH-PCBs. Dynamic cycling between PCB sulfates and OH-PCBs may lead to further metabolic activation of the resulting OH-PCBs. Ultimate toxic endpoints of such processes may include endocrine disruption, neurotoxicities, and many others that are associated with exposures to PCBs and OH-PCBs. This review highlights the current understanding of the complex roles that PCB sulfates can have in the toxicities of PCBs and OH-PCBs and research on the varied mechanisms that control these roles. [ABSTRACT FROM AUTHOR]

Abtsract: A comprehensive study was conducted to understand the performance of USEPA Method 1628 for the testing of Polychlorinated Biphenyl (PCB) Congeners by low-resolution Gas Chromatography-Mass Spectrometry (GCMS–). Method performance was compared to USEPA Method 1668C, USEPA's high-resolution GC–MS method, using nine pulp and paper wastewater samples. USEPA Method 1628 was designed to make PCB analysis more feasible in standard, mid-sized environmental laboratories. This method, which analyzes all PCB congeners, is less sensitive and less expensive to implement than USEPA's high-resolution GC–MS, Method 1668C. The analysis of wastewater samples revealed several potential concerns with Method 1628, including the likelihood of false positive or positively biased identifications of certain congeners. The multi-laboratory validation study conducted by the USEPA indicated that similar problems might have arisen, although a comparison with Method 1668C was not included in that study. The Quality Assurance (QA) aspects of Methods 1628 and 1668C were compared and key issues were identified. Method 1628 can yield results that differ from those obtained with Method 1668C, sometimes quite substantially. Comparison of quantitated results between the two methods could only be applied to those individual analytes that had homologous labeled isotope standards for each method. The percent difference of the reported concentration of the same analyte compared between each method ranged from -16 % to 6241 %. Furthermore, there is a significant risk that Method 1628 may produce false positives and/or positive bias, which could impact the utility of this method if used for some regulatory purposes.

In this paper, we present the concept of traceback analysis to identify the origins of non-wet defects caused by hydrophobic unknown nanoparticles in the semiconductor packaging process. Traceback analysis involves five-steps, i.e., practical observation of failure mode, detailed physical and chemical analysis, process investigation, hypothesis establishment, and failure reproduction with comparison. Initially, the morphology and composition of the unknown nanoparticles are analyzed using an optical microscope (OM), field-emission scanning electron microscopy (FE-SEM), contact angle (CA), energy-dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR). As a result, spherical unknown nanoparticles with a size of ca. 500 nm consists of organic imidazole-derived materials, similar to the composition of organic solderability preservative (OSP). To identify the origin, printed circuit board (PCB) manufacturing processes are reviewed step-by-step. Traceback analysis identifies that the 1-methoxy-2-propyl acetate (PGMEA) cleaning solvent can form spherical emulsions when mixed with deionized (DI) water during the cleaning process. This can occur when PGMEA and DI water mix in the cleaning bath or recycling pipes, or when leftover PGMEA and DI water mix during next cleaning processes. These PGMEA/DI water form emulsions owing to the polarity differences between hydrophobic PGMEA and hydrophilic DI water and remain on the PCB surface. Thus, organic nanoparticles grow in the PGMEA emulsion on the Cu pad during OSP application for surface finishing purposes. This comprehensive approach ensures a thorough understanding of defect origins. The traceback analysis described in this study, involving five-steps, is applicable not only in semiconductor packaging but also in defect investigation across various industries.

Persistent organic pollutants (POPs) are omnipresent in the environment. Due to their physical and chemical properties, POPs bioaccumulate in higher trophic-level species. Birds inhabit many niches and trophic levels and share physiological characteristics with humans. Wild bird eggs reflect the pollution of the environment and exposure experienced by the female prior to egg formation. Bird eggs are relatively easy to collect, easy to handle and store, and decompose slowly. In addition, bird eggs can also be used as biomarkers by examining the eggshell pigmentation and thickness. Aquatic bird eggs have been used most often with less published on terrestrial birds that also suffer consequences of pollution. Here, we review candidate species whose eggs can be used as near-global indicators. We found the Cattle Egret (Bubulcus ibis) as a suitable near-global indicator of terrestrial pollution. It is the most widespread Ardeid with extensive natural expansion, not threatened, occurs in high numbers, breeds in colonies with other Ardeids, has a high trophic status, and eggs are relatively large and easy to collect. Eggs of Cattle Egrets from eight countries and four continents have been analysed for pollutants such as PCBs, DDTs, HCH, HCB, dicofol, aldrin, dieldrin, endrin, heptachlor, mirex, and endosulfan. Multi-country and trans-continental studies using Cattle Egret eggs would therefore be possible, tracking the effectiveness of interventions such as the Stockholm Convention.

PCB layouts with different polygon shapes and insulation distances were prepared and their surface flashover voltage subjected to different ramping rates were measured at different temperatures and different low gas pressures for emulated high-altitude conditions. The dependence of the surface flashover voltage on effects of gas pressure, surface insulation distance, temperature, and polygon shape was studied. Modulation efforts which include tailoring the local surface conductivity and local topography modification were performed to increase the flashover of PCB, and the related mechanism was studied. The results showed that the voltage ramping rate plays an important role in determining flashover voltage. The flashover voltage is lower when the sample is subjected to a rapid voltage ramping rate than with a slow ramping rate. This phenomenon is more prominent towards ambient pressure. The increase in temperature results in a decrease in flashover voltage at 100 kPa, while at 20 kPa and 10 kPa, the influence of temperature on flashover becomes less significant. Through-holes designed in the PCB have a positive role in increasing flashover voltage at lower pressures. However, at 100 kPa, the holes no longer contribute to any higher flashover voltage. Modification of local surface conductivity has no contribution in increasing the flashover voltage, while a surface coating with a surface conductivity of $10^{-10}$ S dramatically decreases the flashover voltage. The work presented in this paper provides a reference for the design and modification of PCB layouts for use in future aerospace hybrid propulsion systems.

During the production process, Printed circuit boards (PCBs) may encounter many defect issues which can severely affect the functionality of the circuit. However, existing PCB defect detection methods suffer from low detection accuracy and slow detection speed. Considering the requirements of PCB factories for detection accuracy and real-time performance This paper first made structural improvements to the existing YOLOx defect detection algorithm, introducing PAN+FPN, SimAM, and SIoU modules to improve the detection accuracy of the algorithm, and named it YOLOx-Plus. Then, algorithm acceleration is achieved by quantifying network parameters and designing FPGA accelerators. In the experiment, the average detection accuracy of YOLOx-Plus is 93.2%, the network loss is reduced by 1.094, the model size is compressed by 64%, detection speed is improved by 68.1%, and the FPS reaches 72.6. The experimental results show that the proposed PCB defect detection method based on YOLOx-Plus and FPGA can efficiently detect typical defects in PCB boards, overcome the limitations of existing methods, and have a wide range of practical applications.

The preservation of aquatic ecosystems and the availability of drinkable water sources depends on the protection of water quality. This is especially true about bodies of water such as ponds. Traditional monitoring techniques frequently require a significant investment of resources and have a restricted application, which has prompted the investigation of more effective technologies. We present a unique wireless acquisition system for monitoring real-time water quality that makes use of the Arduino (ESP32) microcontroller. This system allows us to collect data in real-time. This cutting-edge technology collects data from a variety of pond locations utilizing three individual sensors to perform remote measurements of three critical parameters: turbidity, TDS, and pH. The integration of the system with an aquatic boat enables complete sampling from the center as well as the sides of the pond, which is a significant step forward in terms of innovation. The collected information, which may include pH, turbidity, and TDS readings, is uploaded to the cloud so that it may be evaluated in real-time using the AquaSpecs app. The effectiveness of the proposed system has been proven by deployment in four ponds in Chhattisgarh; these ponds are named Birkona Pond, Budha Pond, Dagania Pond, and Kushalpur Pond. This deployment demonstrates the system’s potential for effective water quality monitoring and management. Using the proposed water quality monitoring system, it was found that the Birkona pond was the cleanest pond having average values of pH, TDS, and Turbidity were 6.23,196.75 and, 8.83 respectively. Budha pond was found highly polluted pond having average values of pH, TDS, and Turbidity were 13.30, 544.18, and, 34.89 respectively. The proposed system is also compared with recent water quality monitoring systems and achieves a higher score. Sensor errors were also very low in the proposed system when compared with traditional approaches, which makes it suitable for monitoring water quality.

Due to the inherent loss characteristics of transmission lines today, the challenges in signal transmission are increasing. Typically, the most widely used printed circuit boards (PCBs) in transmission lines employ FR-4 as the insulation material due to its advantages in electrical insulation and cost-effectiveness. Nevertheless, PCBs that rely solely on FR-4 for the entire insulation layer are unsuitable for high-speed circuits due to significant dielectric losses. Efforts have been made to reduce losses by researching hybrid-stackup PCBs that stack low loss dielectric materials vertically. However, due to the high cost of these low loss dielectric materials, they have mainly been applied in high-end and high-speed applications. Therefore, in this paper, we propose a hybrid-plane PCB structure that uses low loss dielectric materials only in the planes adjacent to high-speed signal traces, minimizing the use of expensive low loss dielectric materials while achieving similar enhancements in signal quality compared to previously researched hybrid-stackup each PCB was modeled using Ansys Q2D Extractor, and S-parameters and eye diagrams were extracted for each to compare their electrical characteristics and signal quality. The simulation results confirm that the proposed hybrid-plane PCB structure in this paper has been found to exhibit improved electrical characteristics compared to PCBs constructed solely with an FR-4 insulation layer. Furthermore, various low loss dielectric thicknesses were compared to interpret the optimal thickness of the low loss dielectric for the hybrid-plane PCB, based on the signal integrity assurance rate.

Solid particles have a higher thermal conductivity compared to a fluid. Therefore, it is a common practice to disperse solid particles inside a base fluid to increase its thermal conductivity. The particle-dispersed fluid is called a thermal fluid. Thermal fluid, such as a coolant, is widely used as a heat transfer fluid. Several types of particles can be used to increase the thermal conductivity of the fluid, i.e., metallic particles, metal-oxide particles, or even carbon-based particles. In this research, a carbon-based particle was used as the dispersed particle. The particle was obtained by processing electronic waste, specifically Printed Circuit Board (PCB). The PCB was pyrolyzed for variable duration at 15, 30, and 45 minutes to increase the carbon content. After pyrolyzing, the particle was milled to reduce its size. Subsequently, the PCB particle was added to distilled water. Sodium Dodecylbenzene Sulfonate (SDBS) was added as a surfactant to increase fluid stability and prevent particle agglomeration. Thermal conductivity was improved by up to a 13% increase at the 15-minute pyrolysis. Adding SDBS surfactant also improves the thermal fluid's stability to -29,1 mV. The fluid's viscosity was slightly increased up to a maximum of 0.984 mPa.S.

This study investigates the effects of sodium dodecyl sulfate (SDS) and polyethylene glycol (PEG) on the galvanic corrosion behavior of copper (Cu) coupled to gold (Au) in a printed circuit board (PCB) etching solution. Galvanic corrosion tests using ZRA (zero resistance ammeter) were performed to determine the optimal SDS concentration for corrosion inhibition. The corrosion current between Cu and Au decreased significantly with the addition of SDS, from 3.26 mA/cm2 to 0.248 mA/cm2 at 4 mM SDS, achieving an inhibitor efficiency (IE) of 92.3%. However, at 15 mM SDS, the corrosion current increased, and IE decreased to 80.5%. This phenomenon is attributed to the critical micelle concentration (CMC) of SDS, where surfactant molecules aggregate and reduce surface adsorption properties. Similarly, ZRA tests were conducted to analyze the effects of PEG on galvanic corrosion. The corrosion current significantly decreased with PEG addition, achieving 98.1% IE at 1 g/L and 99.5% IE at 2 g/L. Beyond this concentration, no significant change in IE was observed, indicating saturation. Potentiodynamic polarization tests were also conducted to study the individual effects of SDS and PEG on Cu and Au. The results showed that SDS effectively inhibited Cu corrosion but had a minimal impact on Au. In contrast, PEG significantly reduced the corrosion current density for both Cu and Au, with reductions of 99.5% and 95.1%, respectively.

AbstractAlthough the sensitivity of receptor models to seeding methods, random noise, and sample size are frequently discussed in environmental forensics, a rigorous evaluation of these factors has been lacking. We generated 435,600 unique datasets with between two and seven sources of PCBs or PFAS that attempt to approximate real-world environmental datasets. Evaluation of these simulated datasets with PVA shows that EXRAWC and NNDSVD seeding methods converge more often and are typically more accurate when sources are similar to each other or are present in small proportions. The results also show that increasing sample sizes up to 25 samples can improve predictive accuracy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper presents the possibility of recovering metals from printed circuit boards (PCBs) of spent mobile phones using the hydrometallurgical method. Two-stage leaching of Cu(II), Fe(III), Sn(IV), Zn(II), Ni(II) and Pb(II) with H2SO4 (2 and 5 M) and HNO3 (2 M) with the addition of H2O2 (10 and 30%) and O3 (9 or 15 g/h) was conducted at various process conditions (temperature—313, 333 and 353 K, time—60, 120, 240, 300 min, type and concentration of leaching agent, type and concentration of oxidant, solid–liquid ratio (S/L)), allowing for a high or total metals leaching rate. The use of two leaching stages allows for the preservation of selectivity, separation and recovery of metals: in the first stage of Fe(III), Sn(IV) and in the second stage of the remaining tested metal ions, i.e., Cu(II), Zn(II), Ni(II) and Pb(II). Removing Fe from the tested PCBs' material at the beginning of the process eliminates the need to use magnetic methods, the purpose of which is to separate magnetic metal particles (ferrous) from non-magnetic (non-ferrous) particles; these procedures involve high operating costs. Since the leaching of Cu(II) ions with sulfuric(VI) acid practically does not occur (less than 1%), this allows for almost complete transfer of these ions into the solution in the second stage of leaching. Moreover, to speed up the process and not generate too many waste solutions, oxidants in the form of hydrogen peroxide and ozone were used. The best degree of leaching of all tested metal ions was obtained when 2 M sulfuric(VI) acid at 353 K was used in the 1st research stage, and 2 M nitric(V) acid and 9 g/h O3 at 298 K in the 2nd stage of leaching, which allowed it to be totally leached 100% of Fe(III), Cu(II), Sn(IV), Zn(II), Ni(II) and 90% Pb(II). [ABSTRACT FROM AUTHOR]