Printed Wiring Boards Research Articles

End-of-life mobile phones parts contain toxic metals that make them hazardous, but can also serve as resource reserves for such metals

Abstract In this study, the concentration of some toxic metals in different parts of end-of-life mobile phones was assessed. Twenty end-of-life mobile phones of different brands and countries of origin, which were widely in use up to the year 2011, were collected from phone repair workshops in Lagos, Nigeria. The collected mobile phones were disassembled into the phone screens, printed wiring boards, plastic casings and batteries. Disassembled parts were individually milled and pulverized, and digested using HCl, HNO3 and H2O2. Flame atomic absorption spectrometry was used to quantify some toxic metals (Pb, Cd and Ni) in the digested samples, and the determined concentrations were compared with permissible limits. The average metals concentration in the disassembled parts followed the order: printed wiring boards > batteries > plastic casings > phone screens. The concentrations of Pb and Ni exceeded their toxicity threshold limit concentration in printed wiring boards, while Ni exceeded the limit concentration in batteries. Based on the maximum permissible concentration required by the Restriction of Hazardous Substances (RoHS) Directives, all Cd concentrations were below the limit concentration; Pb and Ni in printed wiring boards exceeded their limit concentrations, while Ni exceeded its permissible concentration in batteries. The results of this study indicate that printed wiring boards and batteries of end-of-life mobile phones are hazardous, and their improper disposal of could cause environmental and health problems. However, considering the very high concentrations of Pb and Ni, these mobile phone parts could serve as resource reserves for these metals.

News From Japan

The traffic of information communication has continued to increase dramatically in our modern society. The use of millimeter (mm) waves has started to deal with the above trend in the new communication network technology called the fifth generation (5G) system. Here, the mm waves refer scientifically to radio waves of 1 to 10 mm in vacuum with frequencies from 30 to 300 GHz. Because the mm waves cover a wide frequency band, they can make it possible to build a high-speed large-capacity telecommunication system. However, the use of mm-waves in the 5G system has various concerns that must be addressed. One of the significant points is that most conventional printed wiring boards (PWBs) are hardly usable due to their high transmission losses. From this viewpoint, this short article briefly introduces technological trials for developing suitable materials for PWB substrates conducted by Fujikura, a major manufacturer of cables, insulating materials, and other transmission devices of power and telecommunication.

Needs Analysis for the Information System to Support Middle School Students’ Speaking Skills in English Classes

The study aimed to determine the needs and expectations regarding an online information system which will support speaking skills of secondary school students in English lesson. The participants of the study comprised 4 secondary school students and 4 secondary school English teachers in a district of Burdur province in Turkey. In the selection of the participants, convenience sampling model was adopted on the volunteering basis. In the study, the phenomenology research model was utilized. The data were obtained from the semi- structured interviews conducted face-to-face with the participants. In the analysis of the data, the Content Analysis technique was used. The results of the study revealed that participants were willing to access to the system via technologicsl devices like smart phones, computers, tablet pc and smart board. Since communication is important, participants stated that there should be video chat, instant messaging, announcements, forum, social networks, storage and game components in the system. In addition to these, participants noted that the properties such as activities, uploading home works, grading students, student information, attendance shedule, feedback, and duties and responsibilities should be available in the system. Morever, the participants stated that the applicability of the system depends on the introducing the system, motivation, internet-free usage, technological infrastructure, updatability and competitive features. Hereby, it is hoped that the results of these study will be useful in the development of an online information system to support speaking skills of secondary school students in English lesson.

Intrinsically modified self-extinguishing fire-retardant epoxy resin using boron-polyol complex

A novel fire-retardant epoxy thermoset, containing boron polyol complex, was prepared and characterised. The fire-retardant additive was a stoichiometric mixture of boric acid and glycerol. Flame retardancy of the epoxy resin was improved by the formation of stable char layer that protected the underlying epoxy from further burning. Phonon transport through the polymer matrix via hydrogen bonding was identified. The hydrogen bonding acted as a thermal bridge for intermolecular phonon transport to gain improved thermal conductivity resulting early char formation. The hydrogen bonding between the complex and the epoxy matrix was demonstrated using Fourier Transform Infrared Spectroscopy. The phonon transport and a high degree of graphitization was confirmed using Raman Spectroscopy. Thermogravimetric analysis was used for polymer decomposition to confirm a char yield of over 20%. Reaction to fire test revealed enhancement in fire retardancy and self-extinguishing properties of the blend compared to the neat epoxy. Cone calorimetry testing confirmed decreased peak heat release rate and total smoke production by the effect of boron compound in the epoxy matrix. Hydrogen bonding, formation of thick stable layer of char at the polymer surface, and a blowing out effect caused by pyrolytic gases escaping to the gaseous phase, were attributed to the improved fire retardancy. This research may find applications in thermal insulation material of electronic circuit boards, coating in aerospace materials, as well as building and construction industries.

Rapid extraction of gold from complex solutions by metal sulfides

The industrial application potential of current adsorbents for Au(III) recovery is limited due to their high costs, poor adsorption capacity, and complicated preparation processes. This study introduces a novel approach to address these challenges by synthesizing metal sulfides through a one-step hydrothermal method. The synthesized metal sulfides exhibit exceptional adsorption capacities, exceeding 1500 mg/g. Particularly, petal-shaped CuS demonstrates outstanding performance in extracting gold from complex solutions, including fresh water and simulated leaching liquid of electronic circuit boards. With an impressive adsorption capacity of 2536 mg/g in a 700 mg/L Au (III) spiked solution, CuS achieves a remarkable 90.6% removal efficiency. The adsorption process of CuS on gold can be well described by a pseudo-second-order kinetic model and the Langmuir model. Furthermore, CuS is successfully loaded onto sodium alginate (SA) aerogel for large-scale applications. The layered structure of SA overcomes the challenge of solution retrieval, making it a promising material with outstanding removal performance for industrial use. In cases where a high specific surface area does not confer advantages, CuS demonstrates superior performance compared to numerous gold ion adsorbents. This observation motivates us to emphasize the content of active functional groups during the design of gold ion adsorbents. This research significantly advances the field of Au(III) recovery by providing cost-effective and efficient adsorbents with simplified synthesis processes and strong adsorption capabilities.

Numerical Investigation of Fluid Flow and Heat Transfer Characteristics over Double Backward-Facing Step with Obstacles

Many engineering device, including nuclear reactors, heat exchangers, and electronic circuit boards, exhibit flow separation and reattachment. To reduce thermal stress impacts, the components of these devices, which resemble stepped channel designs and are susceptible to high heat flux, must be properly cooled. The present work numerically investigates the fluid flow and heat transfer characteristics through a double backward-facing step with elliptic obstacles located after each step. For this purpose, equations governing fluid flow and heat transfer are solved in a Cartesian framework using an in-house code based on streamline upwind/Petrov-Galerkin finite element method. The effect of various parameters (axis ratios (0.25, 0.5, 0.75, 1), vertical location of obstacles (0.38, 0.577, 0.769), Reynolds number (300, 500, 800, 1000)) on fluid flow and heat transfer characteristics in the channel with and without obstacles are compared and quantified. The recirculation region length of the double backward-facing stepped channel with obstacles decreases after the first and second steps when compared with no obstacles. The local Nusselt number distribution along the corner regions of the stepped wall is enhanced due to obstacles. The axis ratio of obstacles has less influence on the convective heat transfer enhancement than the vertical location of the obstacles.

Design Verification Process for Subsea Oil and Gas Products

Summary A crucial step in new product development is the design verification process (DVP), which assures that the conceptual design of new technology is successfully transformed into a prototype product. In this paper, a novel DVP for subsea electrical and electronic prototype products is introduced. The comprehensive DVP ensures that the prototype of the product is designed righteously, is well documented, and is verified according to international practices and standards such as The American Petroleum Institute (API), International Organization for Standardization, European Norm, and European Union specifications. Compliance testing [environmental stresses and electromagnetic compatibility (EMC)] on the product is proposed to achieve Technology Readiness Level 2 (TRL2) of the first article of a printed circuit board (PCB). Concerning the quality of an electronic circuit board, it is recommended in this paper to follow the guidelines and specifications of the Institute of Printed Circuits to certify the robustness of the design. Finally, the proposed DVP is thoroughly exercised on the insulation monitoring PCB under the prescribed test methods as a case study. The experimental results show that the design is robust and the product is suitable for use in the intended subsea environment after further raising the technology maturity level of the product.

Reconstruction of incomplete public transportation check-out records by heuristic approaching

Smart cards, integrated circuit cards, are frequently used to pay transportation fees in many countries such as the United States, the European Union, Korea and others. Smart card transaction histories in public transportation have been used in making diverse traffic policies. Unfortunately, data preprocessing is required to organize records to extract useful information since the raw data contain artifacts and incomplete information. The paired data, i.e. a boarding and its associated alighting, are one of the key pieces of information required to yield the city traffic demand. However, it is difficult to gather the paired data mainly because the card tagging policies and data collecting methods vary from city to city and from institution to institution. The broken trip links between the boarding and its associated alighting information are the most frequent incomplete data in the smart card histories. Although huge budgets are spent on annual traffic surveys in many countries, there are no accurate Smart card data analysis methods that cover all city cases due to high data complexity and limited base information. Among these two restrictions, limited information is more difficult to resolve because it has a large codomain, thousands of stops, for inference under tiny samples. It gives handicaps of applying well-known high-performance approaches such as deep learning and probability analysis. We propose a reconstruction method by a customized clustering algorithm based on coordinates of transactions-occurred stops, user trip histories and actual vehicle movement trajectories for incomplete trip pairs. The proposed method is derived from evaluating each passenger’s historical clusters and trip patterns. In a blind test 79.1% accuracy is achieved in predicting missing alighting stops while conventional methods reach only 42.3% accuracy.

Investigation of electroless copper plating with high plating coverage in small BVH for next generation fine pattern SAP

Printed wiring board (PWB) used for package substrates are required to have higher circuit densities. We anticipate that PWB circuit patterns and blind via hole (BVH) will continue to be miniaturized due to higher density requirements. The electroless copper plating solution generally used has less chemical material supply to the inside of the BVH than the surface of the substrate. As a result, the copper thickness at the bottom of the BVH tends to be thinner than that on the surface of the substrate. It is difficult to uniformly deposit the electroless copper plating in the BVH on the package substrate by the semi-additive process (SAP), especially when the BVH are becoming smaller. Therefore, we investigated additives that suppress the electroless copper plating deposition on the surface of the substrate and additives that improve the permeability of the plating solution into the BVH. Two additives have been discovered that dramatically improve the plating uniformity in the small BVH compared to the conventional bath. In addition, we used this plating solution with the new additives to evaluate the internal stress and peel strength of the electroless copper plating film. As a result, it was confirmed that both internal stress and peel strength were improved compared to the conventional bath.

Experimental investigations on magnetic pulse crimping of copper lug

One of the most complicated issues in the production of electronic circuit boards, vehicles, aircraft, satellite, and communication components is the crimping of electrical wires to produce a secure connection. Furthermore, terminal crimping is crucial to the safe transmission of electricity; improper crimping causes difficulties like overheating of the plug, power loss, arcing, and mechanical connection failure. Magnetic pulse crimping has the ability to effectively address these difficulties. Magnetic pulse crimping is a non-contact technique creating a uniform pressure without any tool marks on lugs. This technique has better compression of conducting metal wires strands inside the lug and also has less voids compared to conventional mechanical crimping techniques. In this technique the pulsed magnetic field is generated inside the electromagnetic coil by the discharge of capacitor bank current. This magnetic field applies uniform pressure across the circumference of lug and crimp it with cable. 120 sq mm copper lug is magnetic pulse crimped with copper wire at 20 T. Significant improvements in leak rate in magnetically crimped lugs is seem compared to mechanically crimped 120 sq mm copper lugs. This technique also reduces the contact resistance and ultimately the temperature during operation in electrical system.

Effects of deformation and applied temperature on the microstructure and performance of industrial ultra-thin rolled Cu foil

Five-generation communication, foldable cell phone, and wearable devices promote the development of Cu foils by applying multi-layer printed circuit board (MLPCB) and flexible printed circuit board (FPCB). However, few research focused on the combined influence of processing, defects (dislocation, stacking faults, and grain boundaries), and textures modification and its effects on applied performance evolution in the electronic circuit board of ultra-thin Cu foil. In this paper, 12 μm Cu foils were fabricated by the rolling process at reduction deformations of 93.3% and 95.2%. The low-temperature annealing process was utilized to simulate the application of printed circuit boards. The results show that the dislocation density is significantly decreased after annealing, but the influence of reduction deformation has no changes and the dislocation density of the samples with large deformation increased by 40%. In addition to defects, grain orientation has a significant influence on copper foil properties. With the increase of brass and S textures, the tensile strength increased 28.5%. Moreover, the high index of grain plane of S, R, and {025}<001> improves the corrosion resistance by about 130.7%. This work has great significance for preparing high-performance Cu foil applied in PCB.

A Low-Resolution Used Electronic Parts Image Dataset for Sorting Application

The accumulation of electronic waste (e-waste) is becoming a problem in society. Old parts and components are conveniently discarded instead of being recycled. Economic and environmental measures should be taken by individuals and organizations to enhance sustainability. This could include desoldering and reusing parts from electronic circuit boards. Hence, the purpose of the dataset presented in this paper is for the classification of used electronic parts in linear voltage regulator power supply circuits. The dataset presented in this paper comprises low-resolution (30 × 30 pixels) grayscale images of major reusable electronic parts from a typical adjustable regulated linear voltage power supply kitset. The three major reusable parts are capacitors, potentiometers, and voltage regulator ICs. These are typically the most relatively expensive components. Data representing the parts are extracted from 960 × 720 pixel workspace images containing multiple parts. This permits the dataset to be used with multiple types of classifiers, such as lightweight shallow neural networks (SNNs), support vector machines (SVMs), or convolutional neural networks (CNNs). Classification accuracies of 93.5%, 94.9%, and 98.4% were achieved with SNNs, SVMs, and CNNs, respectively. Successful detection and classification of parts will permit a Niryo Ned robotic arm to pick and place parts in the desired locations. The dataset can be used by other academics and researchers working with the Niryo Ned robot and Matlab to handle electronic parts. It can be expanded to include relatively expensive components from other types of electronic circuit boards.

Occurrence and distribution characteristics of PCBs and PBDEs in farmland soils adjacent to electronic circuit board dismantling ruins

The Nanwan village, a green ecological village in Taizhou city, is used as a recycling area (recycling for heavy metal) for electronic circuit boards and as crushing and stacking sites of waste circuit boards for nearly 20 years from 1980s to 2000s. At present, although the e-waste recycling activities in Taizhou city have been effectively controlled, and many areas polluted by the e-dismantling activities have been gradually remediated except Nanwan village. Nanwan village seems to have been forgotten for its special geographical location, which has attracted our attention because of its ecological and food safety issues. Accordingly, the content of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the surface soil around the ruins and four edible agricultural crops were investigated. The main conclusions are as follows: among the four dismantling ruins and surrounding soil samples investigated, the content of Σ20PCBs in vegetable field topsoil of 2(20) is 1,321.3 ± 132.1 μg kg−1; the content of Σ8PBDEs in the paddy soil of 3(1S) is 7,216.9 ± 232.0 μg kg−1; biological toxicity events are likely to occur frequently in 2(20) and 3(1S). PCBs and PBDEs have both horizontal diffusion in distance and vertical diffusion in depth. The lifetime carcinogenic and non-carcinogenic risks of PCBs and PBDEs are at a low risk level, except for the non-carcinogenic risk of PCBs for children in 3(1S). The lifetime carcinogenic and non-carcinogenic risks of PCBs and PBDEs in the edible parts of garlic, ginger, mung beans, and oranges were all at acceptable or negligible levels.

Direct adhesion between Cu foil and polytetrafluoroethylene without increasing surface roughness for high-frequency printed wiring boards.

Polytetrafluoroethylene (PTFE) serves as a suitable dielectric substrate for high-frequency printed wiring boards (PWBs) owing to its excellent properties at high frequency. However, to the best of our knowledge, no study has investigated the strong adhesion between PTFE and Cu foil with low surface roughness. Therefore, in this study, pure-PTFE comprising a weak boundary layer (WBL) on the surface and glass-cloth-containing PTFE (GC-PTFE), which did not contain a WBL, were subjected to heat-assisted plasma (HAP) treatment. Thereafter, we investigated the surface chemical bonding state, surface morphology, and adhesion properties of the as-prepared PTFE toward Cu foil with low surface roughness. As observed, oxygen-containing functional groups were generated on the HAP-treated PTFE, and the WBL in the as-received pure-PTFE was eliminated via HAP treatment. Moreover, the surface roughness of the HAP-treated PTFE did not increase compared to that of as-received PTFE. After performing thermal compression under atmospheric conditions, the adhesion strength of both HAP-treated pure-PTFE and GC-PTFE was ∼0.9 N mm-1. In addition, the adhesion strength of Cu/pure-PTFE and Cu/GC-PTFE increased after thermal compression under a reduced pressure, and the adhesion strength of 1 N mm-1 was obtained. Although the Cu foil was not roughened, Cu/PTFE realized strong adhesive strength. The developed method is advantageous because maintaining a low interface roughness is crucial for applying PTFE to manufacture high-frequency PWBs.

Technological Trends in High-Frequency Low-Loss Printed Wiring Board Materials for Information and Communication Systems

Technological Trends in High-Frequency Low-Loss Printed Wiring Board Materials for Information and Communication Systems

Development of Active-ester Type Epoxy Resin Curing Agents and its Practical Application to the Printed Wiring Boards of High-Speed Communication Devices.

Development of Active-ester Type Epoxy Resin Curing Agents and its Practical Application to the Printed Wiring Boards of High-Speed Communication Devices.

画像認識技術による廃電子基板上製錬忌避素子／有価素子の自動検出

In order to remove smelting repellent elements such as Al and to efficiently recover valuable elements such as Au from waste printed circuit boards, the author have developed an algorithm that automatically detects electronic devices containing a large amount of repellent elements and valuable elements from 2D images of circuit boards by applying image recognition technology. The two types of detection algorithms based on rule-based image processing and deep learning networks were proposed. The former focuses on the appearance characteristics (color, size, shape) of each device and sequentially performs relatively simple image processing. As a result of the detection tests on images of actual waste PC boards using, almost 100% of the heat sinks and CPU socket holders, which are repellent devices, could be detected. The detection ratio was about 80% for the aluminum electrolytic capacitors, and about 80 to 90% for the ICs and connectors, which are valuable devices, even for large ones. On the other hand, when using an algorithm based on a deep learning network, in detection tests targeting the aluminum electrolytic capacitors, ICs, and connectors mounted on waste PC boards, the detection ratio of 95% or more and false detection ratio of less than 5% were successfully achieved.

CFD Modeling of the Effect of the Air- Cooling on Electronic Heat Sources

ABSTRACT The target of this research is to study the performance of air cooling of an electronic cabinet including a heat sources (electronic circuit boards) by using axial fan. The cabinet is cooled from the top by one port while the lower and side walls temperature is kept constant. The effect of inlet and outlet air ports positions in the cabinet is considered. In this work, Icepak4.2.8 package is used in the numerical study. The steady of the 3D incompressible viscous flow problem is solved by using the Icepak package. Various air cooling geometries are applied. Specific conditions for each case are defined, and the computational fluid dynamics is provided for three different groups containing six cases of local inlet and outlet ports. The results are performed for cooling effect factor (CEF). KEYWORDS: Air cooling, Electronic circuit, CFD, Icepak. INTRODUCTION he design of cooling systems for electronic equipment is getting very involved and challenging due to an increase in demand for faster and more reliable electronic systems. Therefore, robust and more efficient design and optimization methodologies are required. Natural convection heat transfer is an important phenomenon in engineering systems due to its wide application in electronics cooling, heat exchangers, and double pane windows. Enhancement of heat transfer in these systems is essential from the industrial and energy saving perspectives. The low thermal conductivity of conventional heat transfer fluids, such as water puts a primary limitation on the performance and the compactness of thermal systems. As a result, different cooling technologies have been developed to efficiently remove the heat from these components. The use of a liquid coolant has become attractive due to the higher heat transfer coefficient achieved as compared to air-cooling. Coolants are used in both single phase and two-phase applications. A single phase cooling loop consists of a pump, a heat exchanger (cold plate/mini- or microchannels), and a heat sink (radiator with a fan or a liquid-to-liquid heat exchanger with chilled water cooling). The heat source in the electronics system is attached to the heat exchanger. Liquid coolants are also used in two-phase systems, such as heat pipes, thermo-siphons, sub-cooled boiling, spray cooling, and direct immersion systems for cooling of electronics [1]. The rapid development in the design of electronic packages for modern high-speed computers has led to the demand for new and reliable methods of chip cooling. As stated by Mahalingam and Berg [2], the averaged dissipating heat flux can be up to 25 W/cm² for high-speed electronic components. However, the conventional natural or forced convection cooling methods are only capable of removing small heat fluxes per unit temperature difference, about 0.001 W/cm².

Corrosion assessment of passivation film generated on solder surface in artificial sweat solution

As the electric joint, the reliability of solder alloy is very important for the circuit card. Since the corrosion might lead to the failure of solder, various characterization methods have been used to assess the corrosion property of Sn-0.7Cu solder alloy in artificial sweat such as the potentiodynamic (PD) polarization, the potentiostatic (PS) polarization, the electrochemical impedance spectroscopy (EIS) and Motty-Schottky (MS) measurement. The EIS results showed that the passivation film owns better barrier properties in alkaline artificial sweat solution. The analysis of electrical equivalent circuit suggested that the passivation film resistance in alkaline solution is two orders of magnitude higher than that in acid solution, which were also supported by MS measurement. The better barrier properties of intact passivation surface contributed to corrosion resistance in alkaline artificial sweat solution. After a typical PD polarization process, the scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) has been employed to characterize surface morphology and chemical composition of passivation surfaces. This work can provide some suggestions for the personalized design of wearable devices by considering the sweat corrosion effect.

External-Field-Independent Thermometric Sensitivity and Green Emission of Upconversion Phosphor Sr2InF7: Yb3+, Er3.

Based on luminescence intensity ratio (LIR) technology, the noncontact upconversion (UC) optical temperature sensor has aroused a great deal of interest due to its great application prospects in some extreme environments. However, most of the studies focused on improving its sensitivity due to the fact that the sensitivity can be influenced by many external field factors, such as the power density and pulse width of pumping sources or temperature. Herein, a green-emitting UC phosphor Sr2InF7: Yb3+, Er3+ was developed as a potential thermometer, which retained bright green emission under 980 nm excitation with different pulse widths and power densities or at different temperatures; the possible mechanisms are discussed in detail. Its sensitivity almost remained constant when using both continuous wave (c.w.) and pulsed laser or different power densities, which meant the sensitivity of Sr2InF7: Yb3+, Er3+ was independent of the characteristics of pumping laser. A flexible thin-film thermometer composed of Sr2InF7: 2%Yb3+, 2%Er3+ was also fabricated to detect the temperature of microelectronic components, which can not only accurately measure the temperature of the working electronic circuit board but also exhibit excellent repeatability. The results indicated that the present noncontact UC temperature sensor showed stable green emission and thermometric sensitivity as well as the possibility of replacing the traditional thermometers.