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In view of the rapidly increasing e-waste, bioleaching of metals from e-waste is an economical and ecologically conscientious option to address the issue of its disposal and/or recycling. Bioleaching of heavy metals by using bacteria of the Bacillus genus has been reported in many studies; however, the bioleaching potential of the Lysinibacillus genus is unexplored. In the present study, Lysinibacillus sp. SDG4 was isolated, identified, analysed and used for leaching toxic metals from e-waste printed circuit boards (PCBs). The bioleaching of metals was deciphered and analysed by using scanning electron microscopy (SEM) along with energydispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The presence of organic acids in the Lysinibacillus primary metabolites was established by FTIR analysis. The presence of functional groups like C-O and C-N in the transmittance band range of 1037.70 to 1658.78 cm-1 wavelength, C-H at 2746.63 and 2964.59 cm-1, O-H at 3412.08 cm-1 and RCO-OH at 582.50 cm-1 suggested the production of metal chelating functional groups by the bacterial strain. The heavy metal profile was determined using ICP-OES analysis. This revealed bioleaching of Al (99.74%), Zn (99.60 %), Cu (93.75%) and Fe (59.24%) in 30 days with a PCB concentration of 1 gm/ml by Lysinibacillus sp. SDG4. These findings confirmed the display of morphological changes by accumulation of metals by Lysinibacillus sp. SDG4 using SEM-EDX analysis. Thus, the study exhibited the potential of the Lysinibacillus genus in bioleaching metals from e-waste. [ABSTRACT FROM AUTHOR]

Printed circuit boards (PCBs) are the main components of e-waste. In order to reduce the negative impact of waste PCBs on human health and the environment, they must be properly disposed of. A new method is demonstrated for recycling waste PCBs. It is referred to as the high-temperature thermo-mechano-chemical gasification (TMCG) of PCBs by the detonation-born gasification agent (GA), which is a blend of H2O and CO2 heated to a temperature above 2000 °C. The GA is produced in a pulsed detonation gun (PDG) operating on a near-stoichiometric methane–oxygen mixture. The PDG operates in a pulsed mode producing pulsed supersonic jets of GA and pulsed shock waves possessing a huge destructive power. When the PDG is attached to a compact flow reactor filled with waste PCBs, the PCBs are subject to the intense thermo-mechano-chemical action of both strong shock waves and high-temperature supersonic jets of GA in powerful vortical structures established in the flow reactor. The shock waves grind waste PCBs into fine particles, which undergo repeated involvement and gasification in the high-temperature vortical structures of the GA. Demonstration experiments show full (above 98%) gasification of the 1 kg batch of organic matter in a setup operation time of less than 350 s. The gaseous products of PCB gasification are mainly composed of CO2, CO, H2, N2, and CH4, with the share of flammable gas components reaching about 45 vol%. The solid residues appear in the form of fine powder with visible metal inclusions of different sizes. All particles in the powder freed from the visible metal inclusions possess a size less than 300–400 μm, including a large fraction of sizes less than 100 μm. The powder contains Sn, Pb, Cu, Ni, Fe, In, Cd, Zn, Ca, Si, Al, Ti, Ni, and Cl. Among these substances, Sn (10–20 wt%), Pb (5–10 wt%), and Cu (up to 1.5 wt%) are detected in the maximum amounts. In the powder submitted for analysis, precious elements Ag, Au, and Pt are not detected. Some solid mass (about 20 wt% of the processed PCBs) is removed from the flow reactor with the escaping gas and is partly (about 10 wt%) trapped by the cyclones in the exhaust cleaning system. Metal inclusions of all visible sizes accumulate only in the flow reactor and are not detected in powder samples extracted from the cyclones. The gasification degree of the solid residues extracted from the cyclones ranges from 76 to 91 wt%, i.e., they are gasified only partly. This problem will be eliminated in future work. [ABSTRACT FROM AUTHOR]

A rotating inclined disk electrostatic separation device was designed and investigated for the separation of millimeter sized metal and plastic particles. This device comprises a set of three-phase electrodes intricately built on the upper surface of a streamlined PCB (Printed Circuit Board) and powered by three high-voltage amplifiers, delivering a square waveform signal. The separation mechanism is based on the application of an electro-adhesion force to metal particles, complemented by the disk's rotational action, which facilitates the collection of plastic particles as they naturally detach from its surface. The obtained results, according to voltage levels, inclination angles, and voltage frequency settings, have confirmed the device's performance in terms of recovery and purity rates. Note that these values reached 95% for recovery and 100% for purity for determined values of the parameters. [ABSTRACT FROM AUTHOR]

The article evaluates the potential of hydrogen as a clean energy source, discussing its applications in transportation, industry and residential heating, as well as its role in achieving net zero emissions targets. It highlights ongoing efforts to produce green hydrogen and overcome technical and logistical challenges in scaling up its production and integration into existing energy systems.

Purpose: This study aims to investigate the impact of pollution control bonds (PCBs) on overinvestment within utility firms. Design/methodology/approach: This empirical study analyzes a data set comprising 215 US energy firms observed from 2011 to 2021, using the ordinary least square regression with standard errors adjusted for firm-level clustering. Findings: The study reveals a negative relationship between PCBs and overinvestment, indicating that PCBs are an effective tool in curbing excessive investment. Additionally, it demonstrates that chief executive officer (CEO) overconfidence diminishes the influence of PCBs on overinvestment. These findings remain robust across various metrics for measuring overinvestment and CEO overconfidence, as well as when alternative estimation methods are used. These results align with insights derived from agency theory and upper echelon theories. Research limitations/implications: Regulators are encouraged to actively promote the use of PCBs as a financing tool for environmentally focused initiatives. To achieve this, regulatory bodies should enhance their presence within the utility sector, particularly in regions grappling with higher pollution levels. This requires the implementation of strategic policies and regulatory frameworks aimed at mitigating excessive investments. Simultaneously, policymakers should take proactive measures to introduce financial instruments designed to optimize investment efficiency, thus facilitating eco-friendly projects. Originality/value: To the best of the authors' knowledge, this paper holds the distinction of being the first to examine the impact of a specific type of green bond, namely, PCBs, on overinvestment. Furthermore, it contributes to the literature on personality traits, particularly within the context of the upper echelon theory, by investigating the moderating influence of CEO overconfidence. [ABSTRACT FROM AUTHOR]

Printed circuit boards (PCBs) can be produced by chemical or mechanical methods. Continuous copper paths are difficult to print in the chemical method and breaks may occur in copper paths. In addition, this method is harmful to human health and the environment, as various chemicals are used. In the mechanical method, PCB is processed with computer-controlled numerical workbenches (CNC). Although prototyping can be done quickly and without harming the environment with these benches, the desired results may not be obtained. Reasons for unsuccessful machining in CNC machines; manufacturing and assembly errors in the production of benches, the use of low quality mechanical and electronic components, and the reference of a single point especially for the Z-axis of the part connected to the benches. In this paper, a precise and stable PCB Router is presented to make fast, cost-effective and successful PCB machining. In order to minimize the vibration and oscillations of the PCB Router caused by manufacturing and assembly errors, the dimensions of the router were kept low and metal material was preferred for the router body. Precision is ensured by quality motor drivers and stepper motors. The PCB Router is controlled by an original control board. This card is equipped with a multipoint referencing feature for the Z-axis. Thus, homogeneous machining in the Z-axis for the entire surface of the PCB can be realized by performing referencing operations on the PCB connected to the workbench as many points as the user enters. With the developed router, PCBs with rectangular and circular patterns were engraved at cutting depths of 0.030 mm and 0.050 mm with 0.20 mm and 0.30 mm diameter milling tools with a 30-degree tip angle, respectively. Moreover, a 16-terminal integrated circuit element was successfully engraved at a cutting depth of 0.040 mm with a 0.34 mm diameter V-tip with a 30-degree tip angle. Homogeneous milling was achieved utilizing the proposed multi-point referencing feature. Each milling operation was completed in approximately 30 min - 45 min. [ABSTRACT FROM AUTHOR]

The article explores the complexities and controversies surrounding the determination of a product's country of origin in international trade. It discusses the "substantial transformation" test, which is commonly used to determine origin, but suggests that it needs to be updated to account for modern manufacturing processes and intangibles. The article also examines alternative approaches to determining origin, such as value-content rules and process-based rules, but acknowledges their limitations. Overall, the article emphasizes the importance of consistent and predictable rules of origin in international trade. [Extracted from the article]

Our paper develops and tests a research model that proposes that job satisfaction (JSAT), career satisfaction (CSAT) and work engagement (WENG) mediate the effect of psychological contract breach (PCB) on affective organizational commitment (AOC). Data were collected from small-sized hotel employees who occupy frontline positions in three waves in four cities in Ghana. The hypothesized linkages were assessed via structural equation modelling. The empirical data confirmed all the hypothesized relationships. Specifically, PCB had a negative impact on AOC. Additionally, JSAT, CSAT and WENG mediated the effect of PCB on AOC. Discussion of implications of the findings are included in the paper. [ABSTRACT FROM AUTHOR]

Copyright of Elektronik Industrie is the property of Hüthig GmbH 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.)

Copyright of Journal of Electrochemistry is the property of Journal of Electrochemistry Editorial Office 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.)

Copyright of Elektronik Industrie is the property of Hüthig GmbH 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.)

Modal reservation (MR) allows both increasing the circuit reliability and implementing the effect of modal filtering. The paper presents the study of a printed circuit board (PCB) with MR with the reference conductor in the form of side polygons. The structure is analyzed by quasi-static simulation, and the minimization of the maximum ultra-wideband pulse amplitudes at the far end of the structure after failures is first estimated. Using the heuristic search, the parameters for the PCB structure before and after failures are obtained. It is shown that, before failures, the maximum amplitude (Umax) does not significantly change under the condition of matching and at fixed values of loads. However, after failures, the Umax changes. For this structure, with increasing delay differences between pulses, Umax after failure 3 increased. It is shown that with obtained values of the geometric parameters, amplitudes of decomposition pulses change differently before and after failures. A prototype of the PCB was designed based on this study. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems and human societies depend on oxygenic photosynthesis, which began to reshape our atmosphere approximately 2.5 billion years ago. The earliest known organisms carrying out oxygenic photosynthesis are the cyanobacteria, which use large complexes of phycobiliproteins as light-harvesting antennae. Phycobiliproteins rely on phycocyanobilin (PCB), a linear tetrapyrrole (bilin) chromophore, as the light-harvesting pigment that transfers absorbed light energy from phycobilisomes to the chlorophyll-based photosynthetic apparatus. Cyanobacteria synthesize PCB from heme in two steps: A heme oxygenase converts heme into biliverdin IXa (BV), and the ferredoxin-dependent bilin reductase (FDBR) PcyA then converts BV into PCB. In the current work, we examine the origins of this pathway. We demonstrate that PcyA evolved from pre-PcyA proteins found in nonphotosynthetic bacteria and that pre-PcyA enzymes are active FDBRs that do not yield PCB. Pre-PcyA genes are associated with two gene clusters. Both clusters encode bilin-binding globin proteins, phycobiliprotein paralogs that we designate as BBAGs (bilin biosynthesis-associated globins). Some cyanobacteria also contain one such gene cluster, including a BBAG, two V4R proteins, and an iron-sulfur protein. Phylogenetic analysis shows that this cluster is descended from those associated with pre-PcyA proteins and that light-harvesting phycobiliproteins are also descended from BBAGs found in other bacteria. We propose that PcyA and phycobiliproteins originated in heterotrophic, nonphotosynthetic bacteria and were subsequently acquired by cyanobacteria. [ABSTRACT FROM AUTHOR]

The counterfeiting of products is a serious concern for any nation with the increasing activity of counterfeit markets. Anticounterfeiting tags demand low‐cost, unclonable, facile, and ultrafast manufacturing processes. In this study, a laser‐induced carbonization (LIC) technique is employed to produce discrete sizes of LIC spots distributed randomly in an array fashion, as a tag, preferably on a laser wavelength‐sensitive polyimide (PI) film. This technique enables the intrinsic creation of LIC spots in PI without any foreign functional materials, thus avoiding the need for external material. Owing to laser technology, based on the input design and laser processing parameters, the reconfigurable desired output tags can be accomplished in a very short time. Different forms of LIC spots in an optical image are grouped and sorted into three‐level bits based on their sizes and brightness for digitalization. The unique LIC‐based tags can be applied to the flexible printed circuit board industry to address counterfeiting. [ABSTRACT FROM AUTHOR]

Copyright of Eurasian Physical Technical Journal is the property of E.A. Buketov Karaganda University 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.)

Defect inspection is essential in the semiconductor industry to fabricate printed circuit boards (PCBs) with minimum defect rates. However, conventional inspection systems are labor-intensive and time-consuming. In this study, a semi-supervised learning (SSL)-based model called PCB_SS was developed. It was trained using labeled and unlabeled images under two different augmentations. Training and test PCB images were acquired using automatic final vision inspection systems. The PCB_SS model outperformed a completely supervised model trained using only labeled images (PCB_FS). The performance of the PCB_SS model was more robust than that of the PCB_FS model when the number of labeled data is limited or comprises incorrectly labeled data. In an error-resilience test, the proposed PCB_SS model maintained stable accuracy (error increment of less than 0.5%, compared with 4% for PCB_FS) for noisy training data (with as much as 9.0% of the data labeled incorrectly). The proposed model also showed superior performance when comparing machine-learning and deep-learning classifiers. The unlabeled data utilized in the PCB_SS model helped with the generalization of the deep-learning model and improved its performance for PCB defect detection. Thus, the proposed method alleviates the burden of the manual labeling process and provides a rapid and accurate automatic classifier for PCB inspections. [ABSTRACT FROM AUTHOR]

With the rise of Industry 4.0, its pillars (which include Internet of Things, "Big Data", data analytics, augmented reality, cybersecurity, etc.) have become unavoidable tendencies for the automated manufacturing industry. Equipment upgrade is required to match the new standards of digitally assisted automation. However, not all factories in the medium to small range (or independent manufacturers) can afford to upgrade their equipment. Therefore, the availability of affordable Industry 4.0 upgrades for now-outdated devices is necessary for manufacturers in the SME range (Small-Medium Enterprises) to stay relevant and profitable. More specifically, this work revolves around the automation of printed circuit board (PCB) manufacturing, which is one of the most popular and profitable areas involved in this movement; and within it, the large majority of manufacturing defects can be traced to the soldering or "reflow" stage. Manufacturing research must, thus, aim towards improving reflow ovens and, more specifically, aim to improve their autonomous capabilities and affordability. This work presents the design and results of a controlling interface utilizing a Raspberry Pi 4 as a coupling interface between an MQTT Broker (which monitors the overall system) and the oven itself (which is, intentionally, a sub-prime model which lacks native IoT support), resulting in successful, remote, network-based controlling and monitoring of the oven. Additionally, it documents the design and implementation of the network adaptations necessary for it to be considered a cybersecure IIoT Module and connect safely to the Production Cell's Subnet. All of this to address the inclusion of specific Industry 4.0 needs such as autonomous functioning, data collection and cybersecurity in outdated manufacturing devices and help enrich the processes of SME PCB manufacturers. [ABSTRACT FROM AUTHOR]

Copyright of Elektronik Industrie is the property of Hüthig GmbH 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.)

Copyright of Elektronik Industrie is the property of Hüthig GmbH 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.)

Copyright of Elektronik Industrie is the property of Hüthig GmbH 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.)

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office 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.)

In the modern-day, just about any electronic device uses Printed Circuit Boards (or PCBs). Nevertheless, these are still prey to manufacturing defects, which are extremely hard to detect manually. Other researchers have come up with a slew of ways to improve PCB inspection and problem categorization. As a result, fewer innovative approaches in this sector are being developed as a result of the researchers' failure to disclose their datasets before. The Weibo Huang and Peng Wei study titled 'A PCB Dataset for Defects Detection and Classification'[1] was used to produce a synthetic PCB dataset. The dataset consists of 1386 photos with six types of faults for the detection, classification, and registration of tasks. As part of the evaluation, it looks at how well various convolutional neural network designs diagnose errors using the reference-based technique (proposed in the same research that generated this dataset). When compared to traditional techniques that need pixel-by-pixel processing, a novel method first locates the faults and then classifies them using the selected neural network, which performs better on the dataset than previous methods. This method also has a proposed neural network [1] whose performance is tested against popular models like Inception and VGG using transfer learning. [ABSTRACT FROM AUTHOR]

Conventional exploding foil initiator (EFI) in ignition or detonation applications hosts many performance advantages, but was hindered by the bulky, inaccurate, inefficient and expensive shortcomings. We highlight a novel micro-chip exploding foil initiator (McEFI) using printed circuit board (PCB) technology. The structural parameters were determined based on energy coupling relationship at the component interfaces. Next, the prototype McEFI has been batch-fabricated using PCB technology, with a monolithic structure of 7.0 mm (l) x 4.5 mm (w) x 4.0 mm (δ ). As expected, this PCB-McEFI illustrated the successful firing validations for explosives pellets. This paper has addressed the cost problem in both military munitions and civil markets wherever reliable, insensitive and timing-dependent ignition or detonation are involved. [ABSTRACT FROM AUTHOR]

Develop-etch-strip (DES) process in printed circuit board (PCB) manufacturing industries produces wastewater containing high organic nitrogen, in which monoethanolamine (MEA) is the main COD and nitrogen source. This study evaluated feasibility of biological treatment of high concentration MEA-containing acidified DES wastewater collected from a full-scale PCB industry. Batch test results indicated that aerobic conditions attained the highest specific COD degradation rates (6.5–14.6 mgCOD/gVSS/h), anoxic conditions attained second (4.81 mgCOD/gVSS/h), and anaerobic conditions was the lowest (1.3–3 mgCOD/gVSS/h). The anoxic/oxic (A/O) sequencing batch reactor (SBR) with porous polyurethanes carriers, BioNET, was able to treat MEA-containing acidified DES wastewater with 80 % COD removal and 23 % TN removal at influent COD of 300 mg/L, while the A/O continuous stirred tank reactor (CSTR) with BioNET at 8 h of HRT achieved above 96 % COD removal and 78 % TN removal at influent COD of 630 mg/L. The aerobic batch test results indicated that specific COD degradation rates followed a Haldane-type model, suggesting that MEA acts as an inhibitory substrate, especially at concentrations above 2000 mg/L. In addition, MEA inhibited the onset of nitrification, but not specific nitrate production rate, suggesting that MEA may inhibit nitrification by inhibiting expression of amoA gene, based on amoA gene expression results. Finally, the contribution for COD degradation, denitrification and nitrification by BioNET (< 20 %) was lower than that for suspended sludge in the A/O CSTR, suggesting that the role of BioNET carriers could retain microorganisms and served as the habitats for microorganisms to avoid washout at a shorten HRT situation. [ABSTRACT FROM AUTHOR]

In this paper, we present a new microstrip to waveguide transition design for interfacing printed circuit board (PCB) microstrip transmission lines with 3‐D printed metallised‐plastic waveguide components. Compared with traditional metal waveguides, interfacing with plastic‐based waveguides are challenging due to thermal and mechanical constraints. Despite the development of 3‐D printing technology, the precision of 3‐D printed waveguides is not as good as the machined metal counterparts. This is critical for microwave components and must be considered in the design process. To minimise the effect of non‐ideal waveguide components, a design methodology minimising sensitivity to geometrical variations in the 3‐D printed parts is proposed. By sandwiching the PCB between two waveguide sections and optimising the waveguide impedance transformation geometry, the design shows very low insertion loss. It is mechanically robust, cost effective and simple to manufacture. In full system integration, this transition design eliminates the need for expensive microwave cabling and connectors by directly mounting the waveguide to the microwave transceiver PCB. The proof‐of‐concept transition structure presented in this paper is suitable for microwave applications where low cost and low weight are critical, for example, drone‐based radars for remote sensing and space‐born satellites. The fabricated structure is characterised using two sets of waveguide components manufactured with different 3‐D printing technology and metallisation process': conductive spray painted Fused Deposition Modelling—Polylactic Acid (PLA Painted) and copper electroplated Stereolithography (SLA Plated). Scattering parameters for both types are measured in a short and back‐to‐back configuration, obtaining the reflection coefficient and insertion loss. Measurements indicate good agreement with modelling and measured performance exceeding prior art. The measured operation band of the Copper‐SLA version is 2.9–7.2 GHz with <−10 dB reflection coefficient (S11) and with an insertion loss (S21) of <0.7 dB. With the reduced metallisation and surface quality of the Spray‐PLA model, the band is shifted to 3.0–8.0 GHz with an increased S21 of <1.8 dB. The results demonstrate the importance of adopting new transition structures for 3‐D printed microwave components where the surface roughness, metallisation quality, and mechanical properties are less optimal. By combining the proposed design with 3‐D printed metallised microwave components, very light weight and cost‐effective antenna systems can be implemented. Radiation measurements of a 3‐D printed double ridge horn antenna connected to the waveguide and used as a feed are also presented, where the operation band is measured to 3–10 GHz with a gain of 5–10 dBi. [ABSTRACT FROM AUTHOR]

Inspection of defects in the printed circuit boards (PCBs) has both safety and economic significance in the 4.0 industrial manufacturing. Nevertheless, it is still a challenging problem to be studied in-depth due to the complexity of the PCB layouts and the shrinking down tendency of the electronic component size. In this paper, a real-time automated supervision algorithm is proposed to test the PCBs quality among different scenarios. The density of the PCBs layout and the complexity on the surface are analyzed based on deep learning and image feature extraction algorithms. To be more detailed, the ORB feature and the Brute-force matching method are utilized to match perfectly the input images with the PCB templates. After transferring images by aiding the RANSAC algorithm, a hybrid method using modern computer vision algorithms is developed to segment defective areas on the PCBs surface. Then, by applying the enhanced Residual Network-50, the proposed algorithm can classify the groove defects on the surface mount technology electronic components which minimum size up to 1×3 mm. After the training process, the proposed system is capable to categorize various types of overproduced, recycled, and cloned PCBs. The speed of the quality testing operation maintains at a high level with an average precision rate up to 96.29 % in case of good brightness conditions. Finally, the computational experiments demonstrate that the proposed system based on deep learning can obtain superior results and it outperforms several existing works in terms of speed, precision, and robustness. [ABSTRACT FROM AUTHOR]

Acceptance sampling has been widely used in practical applications for incoming or receiving inspections, and various sampling plans have been developed for different circumstances and purposes. Skip-lot sampling plans (SkSPs) are an effective sampling procedure and may be useful as a reduced inspection system when a submitted lot's quality is good and stable. Thus, this study attempts to integrate the concept of the SkSP and the process yield index Spk to develop a variables SkSP of type 2 (SkSP-2) with an Spk-based single sampling plan (SSP) as the reference plan. This plan is suitable for today's high-yield process environments and products, with a normally distributed quality characteristic under bilateral specification limits. The plan parameters are solved by an optimisation model with nonlinear constraints, which minimises the average sample number (ASN) and satisfies the quality and risk requirements specified by the producer and consumer. The performance and efficiency of the proposed SkSP-2 are examined and compared with the variables SSP in terms of the operating characteristic and ASN curves. Additionally, tables of the plan parameters under selected conditions are provided for reference, and an example from the printed circuit board industry is presented to demonstrate the practicality of the proposed plan. [ABSTRACT FROM AUTHOR]