Lead-free Components Research Articles

Anisotropic optoelectronic properties of lead-free Cs3Bi2I9 single-crystal photodetectors

Lead-free halide perovskites have attracted widespread research interest due to their excellent optoelectronic properties and environmental friendliness. As one of the bismuth iodide compounds, Cs3Bi2I9 perovskite has been extensively explored in the field of photovoltaic devices and radiation detectors due to their non-toxic lead-free components and excellent stability. In this work, we successfully grow large-sized Cs3Bi2I9 single crystals (SC) with (l00) and (00l) crystal exposure facets by inverse temperature crystallization method. Under 525 nm light illumination with the intensity 15 mW cm−2 and 7 V bias, the (l00) Cs3Bi2I9 SC shows 2 times higher photocurrent, 3.6 times higher responsivity, and 2.8 times higher detectivity than the (00l) Cs3Bi2I9 SC, respectively. Superior response time in the scale of millisecond is obtained in both (l00) and (00l) Cs3Bi2I9 SCs. Based on the first-principle calculation, the (l00) SC possesses a higher charge distribution density and a wider dispersion distribution than (00l) SC, suggesting that more electrons in the (l00) SC can be excited in a wider range. The tighter arrangement of Cs+ and [BiI6]− octahedra in the (l00) SC than (00l) SC leads to the anisotropic photoelectric performance in (l00) and (00l) Cs3Bi2I9 SCs. Our results provide a strategy for the oriental growth of Cs3Bi2I9 SCs and the design of anisotropic optoelectronic devices with excellent performance.

The Research on Characteristics of SAC305/Sn-37Pb/ENIG Solder Joint

The reliability of the mix alloy of lead and lead-free components with SnPb paste is an important issue for military electronics. With the increase of density in PCB assembly, the traditional HASL pad has been gradually replaced by the ENIG pad for its better flatness and solderability. But the relationship between the interfacial morphology, microstructure and reliability of the alloy of lead and lead-free components still needs to be further studied. In this paper, the microstructure on the interface of SAC305/ Sn-37Pb/ ENIG solder joint is compared with that of typical SAC305/ Sn-37Pb3/ Cu solder joint, Sn63Pb37 / ENIG solder joint. It is found that the IMC layer on the interface of SAC305/Sn-37Pb/ENIG solder joint is more closer to compound (Cu, Ni) 6Sn5, and limited reflow soldering times has little effect on the strength of SAC305/Sn-37Pb/ENIG solder joint. Based on the case study, the thickness of gold layers has a significant effect on black pad problem in ENIG pad.

A Closed Form Method Combined with the Steinberg’s Solution to Estimate Number of Fatigue Cycles for Lead-Free Solders

Solder joints of components are normally the most susceptible to the vibration loading conditions. The Steinberg’s closed form solution has been widely used in industries to identify high risk components to be candidates for detailed finite element (FE) durability analysis under vibration loads. Unfortunately, the Steinberg’s closed form solution is only applicable to the SnPb, not the lead-free materials (SAC); therefore, it would be troublesome to identify high risk SAC components, especially if there are numerous SAC components in the BOM. This paper is to present a method that would be able to combine with the Steinberg’s closed form solution to identify high risk SAC components. This method is developed from comparison between SnPb and SAC fatigue vs. strain range relationship using the high and low cycles of fatigue Coffin Manson closed form equation. In addition, this method can also predict solder joint fatigue cycles of one material using the already-derived fatigue cycles from another material without re-running detailed FE analysis. This additional feature would help, for example, to make prediction if re-ball from SAC to SnPb or vice versa would pose any risks. It is strongly recommended to utilize this method when assessing lead-free components under vibration as currently it is only available method to serve this purpose.

Convergence of Social Marketing and Engineering: A Lead Mitigation Study in Madagascar

Background and Situation Analysis The importance of Water Sanitation and Hygiene (WASH) projects for the protection of health is embedded in the sustainable development goals. However, within the development and humanitarian fields sustainability of WASH projects is still a challenge with 30–50% of projects failing within two to five years of implementation. Though failure is not linked to any one source, a common theme speaks to a greater need for community engagement and integration of the wants and needs of the end-user in the design process. Social marketing, with its focus on the consumer and use of commercial marketing strategies to achieve behavior change is a promising approach that can be integrated into ongoing WASH initiatives to meet program outcomes and to achieve long-term sustainability. Priority audience Primary audience includes technicians who manufacture and repair pitcher pumps. Secondary audience includes community members in Toamasina, Madagascar, who will experience a decrease in exposure to lead through their water supply. Behavioral objectives Decrease exposure to lead (Pb) introduced through the use of a decentralized, self-supply water system, the pitcher pump. Specifically, decrease use of leaded components in the manufacturing and repair of pitcher-pumps Strategy/Intervention Development of the intervention followed the social marketing process including conducting a situational analysis, identification and selection of a behavioral focus and priority population, formative research, development of an integrated marketing strategy, pretesting the strategy, followed by campaign implementation, and monitoring and evaluation. An intervention focused on building a sense of community and introducing the element of professionalism for the pump manufacturers was developed, consisting of personalized one-on-one outreach to raise awareness of the health topic, followed by skill building trainings on how to make the switch to non-leaded components. This was coupled with tangible products that created a new professional network, documentation of work, and backing of work by trusted government entities. Evaluation Methods and Results Using the theory of planned behavior, a pre/post-test summative evaluation was developed. Preliminary results indicate that pump technicians no longer use lead in pumps unless specifically requested by the pump owners. These results indicate a positive shift towards the use of lead-free components with project follow-up and analysis ongoing. Recommendations for Social Marketing Practice Use of social marketing within the WASH sector is lacking. This paper demonstrates the integration of social marketing in an ongoing WASH project. Through a description of each step of the process, our experiences in implementing it and the lessons learned, we hope to guide future integration. Additionally, this paper demonstrates the convergence of engineers and social marketers working collaboratively on an interdisciplinary team and how this served to enhance project understanding, aid in building local partnerships and help with long-term sustainability.

Effect of the Microstructure of ZnO Thin Films Prepared by PLD on Their Performance as Toxic Gas Sensors

In 2008, the modified European Restriction of Hazardous Substances (RoHS) directive prohibited the use of hazardous substances such as lead, cadmium, and mercury. As such, an urgent need for lead-free components emerged in Europe. In this frame, we have decided to study the microstructure influence of zinc oxide thin films on the detection of hydrogen sulfide (H2S). Zinc oxide thin films were deposited by PLD on silicon substrates under different conditions to modify the microstructure. In order to compare our demonstrators to current commercial semiconductor gas sensors, measurements under H2S were also performed with sensors from Figaro and Winsen corporations. Gas sensors were therefore implemented by using commercial cases in view to test them with Simtronics gas detector DG477. The good sensitivity values measured at T = 400 °C under 100 ppm H2S, and response times as low as 30 s, definitely confirm that ZnO thin films could be developed for commercial sensors.

Fundamental analysis of lead-free CsGeI3 perovskite solar cell

The perovskite solar cells have shown notable improvement in efficiency and stability among all solar cells. Research on perovskite solar cells began in 2009 and has focused on understanding and improving their conversion efficiency made over the past 6 years. In 2014, they showed efficiencies of around 15.9%. Most recently, they showed an efficiency of 25%. However, there are lot of problems with lead-based perovskite solar cells. Being toxic to the environment, there should be an alternative like germanium, which has excellent optical properties but practically it has low efficiency as well as poor stability compared to lead-based perovskite solar cells. Therefore, it becomes essential to invent alternatives that offer comparable efficiency and stability like Pb-based solar cells. The completely Pb-free cesium germanium triiodide (CsGeI3) heterostructure perovskite solar cell was simulated and conversion efficiency of 12.2% was achieved with significantly improved device parameters. To optimize lead-free components, the influence of the defect density and doping concentration of absorber layer are investigated. The solar cell capacitance simulator (SCAPS) simulation results succeed in achieving the highest power conversion efficiency in an all-inorganic non-toxic CsGeI3 based solar cell. The obtained performance metric values are PCE = 12.2%, FF = 70.6%, Jsc = 20.6 mA / cm2 and Voc = 0.84 V.

A Fix for Fixtures: Addressing Lead Contamination in West African Drinking Water.

A Fix for Fixtures: Addressing Lead Contamination in West African Drinking Water.

Midstream Players Determine Population-Level Behavior Change: Social Marketing Research to Increase Demand for Lead-Free Components in Pitcher Pumps in Madagascar.

Lead (Pb) exposure through water contamination is an important issue at the intersection of public health and water, sanitation, and hygiene (WASH). Behavior-change programs designed to address this pressing problem rarely take a behavioral-science-informed approach, nor do they consider the role of intermediate players who often influence and support behavior change. Social marketing segments the population and focuses on the consumer/user throughout program development and implementation. To illustrate the social marketing process, this cross-sectional, qualitative design study investigates the use of Pb in the construction and maintenance of household pitcher pumps for potable water in Madagascar. A sample of 18 technicians were interviewed on their current practices, motivators, barriers, and communication channels for knowledge exchange. The results reveal the importance of peers, those considered experts or “market mavens”, and the need for information on the dangers of Pb as an outdated practice for any future intervention. This study advances the notion of a design shift within engineering WASH projects, whereby social/behavioral approaches are used to consider the needs, concerns, and current behaviors of the consumer. We also advocate for engaging intermediate players who often influence behavior change in the rollout of an engineering innovation.

Comparative study on the performance of piezo-active 1–3-type composites with lead-free components

Piezoelectric properties and related figures of merit are studied in novel 1–3-type composites based on ferroelectric domain-engineered lead-free single crystal with the relatively large longitudinal piezoelectric coefficient [Formula: see text]. Relationships between the piezoelectric properties and the set of figures of merit are analyzed for the 1–3 and 1–3–0 composites that contain the same single-crystal and polymer components. For a composite characterized by 1–3–0 connectivity, an influence of a porous piezo-passive matrix on the figures of merit and their volume-fraction behavior is considered additionally. A large anisotropy of figures of merit is observed in the 1–3–0 composite with specific porous matrices. A diagram is put forward to show volume-fraction regions of the large anisotropy of figures of merit of the studied 1–3–0 composite. Due to large figures of merit and their considerable anisotropy, the studied lead-free composites can be applied in piezoelectric energy-harvesting systems, sensors, transducers, and so on.

Occurrence of Lead and Other Toxic Metals Derived from Drinking-Water Systems in Three West African Countries.

Background:Exposure to toxic metals (TMs) such as lead can cause lifelong neurodevelopmental impairment and other adverse outcomes. TMs enter drinking water from human activity, geogenic contamination, and corrosion of water system components. Several studies report TM contamination in piped systems and private wells in high-income countries (HICs). However, few robust studies report on TM contamination in low- and middle-income countries (LMICs).Objectives:We characterized the occurrence and investigated sources of TM contamination in 261 rural water systems in three West African LMICs to inform prevention and management.Methods:Water samples were collected from 261 community water systems (handpumps and public taps) across rural Ghana, Mali, and Niger. Scrapings were collected from accessible components of a subset of these systems using a drill with acid-washed diamond-tipped bits. Samples were analyzed by inductively coupled plasma (ICP) mass spectrometry or ICP optical emission spectroscopy.Results:Of the TMs studied, lead most frequently occurred at levels of concern in sampled water system components and water samples. Lead mass fractions exceeded International Plumbing Code (IPC) recommended limits (0.25% wt/wt) for components in 82% (107/130) of systems tested; brass components proved most problematic, with 72% (26/36) exceeding IPC limits. Presence of a brass component in a water system increased expected lead concentrations in drinking-water samples by 3.8 times. Overall, lead exceeded World Health Organization (WHO) guideline values in 9% (24/261) of drinking-water samples across countries; these results are broadly comparable to results observed in many HICs. Results did not vary significantly by geography or system type.Discussion:Ensuring use of lead-free () components in new water systems and progressively remediating existing systems could reduce drinking-water lead exposures and improve health outcomes for millions. However, reflexive decommissioning of existing systems may deprive users of sufficient water for health or drive them to riskier sources. Because supply chains for many water system components are global, TM monitoring, prevention, and management may be warranted in other LMICs beyond the study area as well. https://doi.org/10.1289/EHP7804

Fabrication and electrical characterization of a eco-friendly capacitive component: Bi(Co2/3V1/3)O3

A lead-free electronic component Bi(Co2/3 V1/3)O3 has been fabricated using conventional solid-state technique. The conducting, capacitive and resistive properties of the synthesized element have extensively been investigated. An analysis of X-ray diffraction (XRD) data shows the formation of the electronic component in orthorhombic crystal symmetry. The uniform distribution of grains on the specimen surface has been identified through scanning electron microiscope (SEM). Detailed analysis of dielectric parameters (εr,tanδ) substantiate the component as a dielectric. Study of impedance data reveals the contributions of bulk as well as grain boundary on the capacitive and resistive properties of the fabricated sample. The frequency and temperature-dependent ac conductivity spectrum obey Jonscher's power law. The existence of a negative temperature coefficient of resistance (NTCR) behaviour can be implied from the reduced grain resistance with temperature. The hysteresis loop (P-E) confirms the presence of ferroelectric property in the compound. The fabricated compound shows higher dielectric constant, low loss at high temperature (>200 °C), eco-friendly and can sustain in harsh environment ((>300 °C) thus it can be a stronger contender for functional devices.

Failure mechanism of lead-free component boards in thermomechanical test based on recrystallization enhanced cracking

The purpose of this paper is to make a comprehensive understanding of the trends between the lifetime and the thermomechanical test setup parameters, based on the physical failure mechanism of SnAgCu solder interconnections in the component boards. The thermomechanical tests, including thermal cycling and thermal shock, were employed to investigate the failure of the component boards under different loading conditions. The in situ observation during the thermomechanical tests was employed to study the microstructure evolution and the crack propagation of solder interconnections. Electrical failures of the component boards under all setup conditions are mainly caused by the cracks, which propagate along the continuous network of the high-angle grain boundaries produced by the distinguished recrystallization of solder interconnections. The propagation of cracks is highly dependent on the expansion of the recrystallized volume in the solder interconnections. In addition, the expansion of the recrystallization would be influenced by the setup parameters of the thermomechanical test. The paper discusses the relationship among the four factors of the lifetime, the crack growth, the restoration phenomenon and the test setup parameters, in order to explain the complicated trend between the component board lifetime and the setup parameters.

Micro-stereolithography of KNN-based lead-free piezoceramics

The additive manufacturing technique of micro-stereolithography (µSL) is applied to fabricate alkaline niobate (K0.48Na0.52NbO3, KNN) based lead-free piezoceramics. Complex KNN-based piezoceramic green parts with fine dimensional characteristics, such as a piezoceramic transducer array and a hollow hemisphere, have been printed. The two-step debinding and sintering processes are employed to obtain crack-free dense KNN ceramics with complex shapes. These printed KNN ceramics exhibit superior piezoelectric and ferroelectric performance (εr = 2150, d33 = 170 pC/N, Pr = 12.1 μC/cm2, EC = 6.1 kV/cm, and TC = 230 °C), which are comparable to those of KNN piezoceramics made by traditional methods. These results suggest that the µSL technique may serve as an alternative method to manufacture KNN lead-free piezoceramic components, especially for the application with complex architectures.

Investigation of Sr1-xCaxTiO3 ceramics dedicated to high-frequency lead-free components

Lead–free Sr[Formula: see text]CaxTiO3 ([Formula: see text]) ceramics were synthesized via a solid state reaction technique at room temperature. The effects of ionic substitutions in A-sites between strontium and calcium on the structural and dielectric properties were investigated. XRD technique was used to identify the crystal structure and to demonstrate the phase purity. SEM observations have shown homogeneous morphologies for all samples. Dielectric measurements were investigated for a wide range of frequency (100[Formula: see text]Hz–1[Formula: see text]GHz) and temperature (25[Formula: see text]C–250[Formula: see text]C). Strontium substitution by calcium has not only led to a decrease in the dielectric permittivity value, but also to the loss tangent value by a considerable factor. Interesting values of the quality factor and the quite constant value [Formula: see text] in extended frequency and temperature ranges show that SCT ceramic could be a real candidate for the development of monolithic ceramic capacitors dedicated to high-frequency lead-free components and/or to extremely high-temperature environments.

Applications of lead-free piezoelectric materials

Abstract

High voltage generation from lead-free magnetoelectric coaxial nanotube arrays and their applications in nano energy harvesters

Harvesting energy from surrounding vibrations and developing self-powered portable devices for wireless and mobile electronics have recently become popular. Here the authors demonstrate the synthesis of piezoelectric energy harvesters based on nanotube arrays by a wet chemical route, which requires no sophisticated instruments. The energy harvester gives an output voltage of 400 mV. Harvesting energy from a sinusoidal magnetic field is another interesting phenomenon for which the authors fabricated a magnetoelectric energy harvester based on piezoelectric–magnetostrictive coaxial nanotube arrays. Piezoelectric K0.5Na0.5NbO3 (KNN) is fabricated as the shell and magnetostrictive CoFe2O4 (CFO) as the core of the composite coaxial nanotubes. The delivered voltages are as high as 300 mV at 500 Hz and at a weak ac magnetic field of 100 Oe. Further tailoring of the thickness of the piezoelectric and magnetic layers can enhance the output voltage by several orders. Easy, single-step wet chemical synthesis enhances the industrial upscaling potential of these nanotubes as energy harvesters. In view of the excellent properties reported here, the lead-free piezoelectric component (KNN) in this nanocomposite should be explored for eco-friendly piezoelectric as well as magnetoelectric power generators in nanoelectromechanical systems (NEMS).

Reflow Optimization Process: Thermal Stress Using Numerical Analysis and Intermetallic Spallation in Backwards Compatibility Solder Joints

This study applies the reflow optimization process to investigate the phenomenon of spalling in aerospace backward compatibility solder joints when utilized with a Ni substrate [electroless nickel immersion gold, printed circuit board surface finish, and ball grid array (BGA) pads]. The backward compatibility assembly comprised a lead-free tin–silver–copper (96.5Sn3.0Ag0.5Cu/SAC 305 alloy) solder ball assembled with tin–lead paste. The soldering of the lead-free BGA was conducted using two reflow temperature profiles and two conveyor speeds under a nitrogen atmosphere in a full convection reflow oven. The optimized reflow profile has peak temperatures ranging from 237.06 to 237.09°C for 68.94–69.36 s. Scanning electron microscope reveals intermetallic compound formation with maximum thicknesses which are lower than 12 μm as per aerospace requirement. Intermetallic compound spalling of solder ball interface components was not observed. However, spalling between printed circuit board and solder bulk was noted. Nevertheless, at both reflow temperature profiles, the composition and phase distribution of the lead-free BGA ball and tin–lead solder paste were fairly uniform across all joints. This work also presents a finite element-based simulation of backward compatibility assembly in reflow process. A growing number of manufacturers are changing their components to lead-free types without notifying customers. If an aerospace production line is still running a tin–lead-based process, understanding how these lead-free components are processed with tin–lead solder becomes essential. This paper will serve as a reference for manufacturing engineers, particularly those involved in surface mount technology application.

High-Performance Lead-Free Electroplated Composite Bearing Overlay for Heavy Duty Applications

Material selection for engine internal components, e.g., bearings, is becoming increasingly more complex and demanding as the operating environments become more aggressive with the introduction of new technologies for the reduction of CO2 emissions. Historically, engine bearings contained lead, which has excellent fundamental bearing properties such as compatibility (run satisfactorily under conditions of marginal lubrication), conformability (deform and accept small scale geometrical inaccuracies of the crankshaft), and embeddability (tolerance to dirt and other foreign materials) while being readily alloyed to achieve good wear and fatigue resistance. However, facing new challenges, many original equipment manufacturers have started development programs to replace lead-containing with lead-free engine components in order to comply with new end-of-life vehicle directives or anticipated future directives. For more than 15 years, MAHLE has been successfully supplying the light, medium, and heavy duty market, with premium electroplated leaded composite bearings, which are designed to improve wear resistance. Some of this market now demands a switch to lead-free materials, while maintaining or exceeding its aforementioned requirements on bearing material properties. Composites of hard particles in a softer metal matrix are in this context ideally suited bearing materials as they can be tailored to obtain the optimal mix between soft and hard properties for the individual application. Typical hard particles that are commonly used comprise of metal oxides, nitrides or carbides. In addition to higher load carrying capabilities and longer service life, new engine technology trends demand that bearings also must operate under mixed or boundary lubrication conditions without having any adverse effect on the performance and integrity of the engine system. Boundary lubrication is commonly observed upon starting the engine before the elastohydrodynamic oil film is fully established. In this state, load is carried by surface asperities rather than by the lubricant. So far, the incorporation and even distribution of the hard particles into an electroplated lead-free matrix was not achievable using conventional direct current electroplating techniques. MAHLE, therefore, has developed a patented pulse plating technique in order to incorporate hard particles into the overlay metal matrix. The refined and modified crystal structure of the resulting lead-free overlay, with incorporated hard particles, yields a premium electroplated bearing with superior wear and fatigue resistance. Corresponding rig and engine test results have been completed to support the material development.

Synthesis and characterization of lead-free ternary component BST–BCT–BZT ceramic capacitors

Polycrystalline sample of lead-free 1/3( Ba 0.70 Sr 0.30 TiO 3) + 1/3( Ba 0.70 Ca 0.30 TiO 3) + 1/3( BaZr 0.20 Ti 0.80 O 3)( BST - BCT - BZT ) ceramic was synthesized by solid state reaction method. Phase purity and crystal structure of as-synthesized materials was confirmed by X-ray diffraction (XRD). Temperature-dependent dielectric permittivity studies demonstrated frequency-independent behavior, indicating that the studied sample has typical diffuse phase transition behavior with partial thermal hysteresis. A ferroelectric phase transition between cubic and tetragonal phase was noticed near room temperature (~ 330 K). Bulk P–E hysteresis loop showed a saturation polarization of 20.4 μC/cm2 and a coercive field of ~ 12.78 kV/cm at a maximum electric field of ~ 115 kV/cm. High dielectric constant (ε ~ 5773), low dielectric loss (tan δ ~ 0.03) were recorded at room temperature. Discharge energy density of 0.44 J/cm3 and charge energy density of 1.40 J/cm3 were calculated from nonlinear ferroelectric hysteresis loop at maximum electric field. Dielectric constant at variable temperatures and electric fields, ferroelectric to paraelectric phase transition and energy storage properties were thoroughly discussed.

Standards for Tin Whisker Test Methods on Lead-Free Components

Tin whiskers are widely recognized as being a reliability threat to lead-free electronic components. The current standards to assess the tin whisker susceptibility of lead-free finishes in electronic components are problematic. Key problems include lack of data collection, lack of agreement on proper techniques for measuring whisker length, lack of established acceleration transforms for prescribed tests, and disagreement over acceptance criteria. This paper overviews the tin whisker standards and then describes the problems listed above. Recommendations for improvements are then presented and discussed.