Sn Bi Research Articles

Hot compression deformation behavior and dynamic recrystallization of a precipitate-free Mg–Bi–Sn alloy

The addition of Sn improves the properties of Mg–Bi-based alloys, and can potentially overcome the high-temperature limitations of magnesium (Mg) alloys. However, high-Sn alloying leads to stress concentration during hot extrusion. Hence, in this study, the dynamic recrystallization (DRX) mechanism and hot-deformation behavior of a novel precipitate-free Mg–0.25Bi–0.25Sn alloy during hot compression conducted at 250–400 °C with strain rate of 0.001–1 s−1 were examined in detail by constructing processing maps and deriving constitutive equation. The obtained correlation coefficient was 0.99113, indicating that the proposed method can adequately predict the hot deformation behavior of the studied alloy. The calculated average activation energy was 143.0336 kJ/mol. According to the processing maps, the ideal processing areas corresponded to the conditions of 300–400 °C/0.001 s−1/1 s−1 and 400 °C/0.1 s−1. In addition, a transformation of prismatic <a> slip to pyramidal II <c+a> slip was observed at 350 °C, and the continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) processes occurred during hot compression. The classification of the dominant DRX mechanisms was based on the Zener–Hollomon parameter (Z). Under high-Z deformation conditions, CDRX and DDRX occurred simultaneously; however, CDRX was the predominant process. Under medium-Z deformation conditions, DDRX was the only DRX process. Under low-Z deformation conditions, DDRX dominated over the DRX mechanism and was partially accompanied by CDRX.

Hot tear cracks on the suppression of Sn–Bi alloy for low-temperature assembly

PurposeIn the electronic assembly industry, low-temperature soldering holds great potential to be used in surface mounting technology. Tin–bismuth (Sn–Bi) eutectic alloys are lead-free solders applied in consumer electronics because of their low melting point, high strength and low cost. This paper aims to investigate how to address the problem of hot tear crack formation during Sn–Bi low-temperature solder (LTS) in the mass production of consumer electronics.Design/methodology/approachThis paper explored the development of hot tear cracks during Sn–Bi soldering in the fabrication of flip chip ball grid arrays. Experiments were designed to simulate various conditions encountered in Sn–Bi soldering. Quantitative analysis was conducted on the number of hot tear cracks observed in different alloy compositions and solder volumes to explore the primary cause of hot tear cracks and possible methods to suppress crack formation.FindingsHot tear cracks existed in Sn–Bi solders with different bismuth (Bi) contents, but increasing the solder volume reduced the number of hot tear cracks. Experiments were designed to test the degree of chip transient thermal warpage with temperature change, and, according to the results, glue was dispensed in specific areas to reduce chip warpage deformation. Finally, the results of combined process experiments pointed to an effective method of low-temperature soldering to suppress hot tear cracks.Research limitations/implicationsThe study focuses on Sn–Bi solders only without other solder pastes such as SAC305 or Sn–Zn series.Practical implicationsWith the growing popularity of smart electronics, especially in intelligent terminals, new energy vehicles electronics, solar photovoltaic and other field, there will be more and more demand for low- temperature, energy-saving, lead-free solders. Therefore, this study will help the industry to roll out LTS (Sn–Bi) solutions rapidly.Social implicationsIn the long term, lean and green manufacturing is expected to be essential for maintaining an advanced manufacturing industry across the world. Developing new LTSs and soldering processes is the most effective, direct solution for energy conservation and emission mitigation. With the growing popularity of smart electronics, especially in intelligent terminals, new energy vehicles and solar photovoltaics, there would be an increased demand for low-temperature, energy-saving, lead-free techniques.Originality/valueAlthough there are many methods that can be used to suppress hot tear cracks, there is little research on how to control the hot tear cracks caused by the low-temperature soldering of Sn–Bi in laptop applications. The authors studied the hot tear cracks that developed during the world’s first mass production of 50 million personal laptops based on low-temperature Sn–Bi alloy solder pastes. By controlling the Bi content, redesigning the solder paste printing process (e.g. through a printer’s stencil) and adding dispensing processes, the authors obtained reliable and stable experimental data and conclusions.

High stability In–Sn–Bi multi-element alloy anode for Mg ion batteries

In this work, the electrochemical properties of micron In–Sn–Bi alloy electrodes for rechargeable magnesium batteries (RMBs) are evaluated. Compared with the low stability pure Bi anode, In–Sn–Bi alloy anodes show high reversible specific capacity and high cycle stability. Among the studied alloys, In10Sn10Bi80 electrode shows high reversible specific capacity up to 260 mAh g−1, good rate performance and excellent cycle stability (capacity retention above 98% after 80 cycles). The synergistic effects coming from the multi-phase structure have been clarified. The multi-phase structure resists the volume change and structural collapse and then guarantee the good cycle stability compared with that of pure Bi. Additionally, benefited by the fast kinetics of magnesiation/de-magnesiation of the dispersed Bi-rich phase, the reversibility of magnesiation/de-magnesiation of In and Sn are also realized. The multi-phase & fine-substructure design of the electrode materials is promising for the application in RMBs.

Clean and efficient recovery of In–Sn and In–Sn–Bi lead-free brazing materials by vacuum volatilization and thermodynamic modeling

In this study, a novel method was proposed for the clean and efficient recovery of high-value-added In–Sn and In–Sn–Bi alloys. Vacuum volatilization of the In–Sn binary alloy was conducted in a temperature range of 1373–1573 K with a system pressure of 5 Pa. The results showed that In and Sn were effectively separated. The Sn content in the residue was 99.9908%, and the In content in the volatile fraction reached 99.66%. Vacuum volatilization of the In–Sn–Bi ternary alloy was conducted out at 1073–1373 K and 5 Pa. The results showed that Bi could be separated from In and Sn, the Bi content in the residue decreased from 32.5% to 3.88%, and the Bi content in the volatile fraction reached 95.67%. The residual In–Sn alloy could be effectively separated by vacuum volatilization. The MIVM, M-MIVM, Wilson equation and NRTL were used to calculate and analyze the activity and activity coefficients of In–Sn, In–Bi, Sn–Bi and In–Sn–Bi alloy elements, respectively, and the results showed that M-MIVM had the highest prediction accuracy. The vapor-liquid equilibrium (VLE) data of the In–Sn, In–Bi, Sn–Bi, and In–Sn–Bi alloys were predicted, and the corresponding VLE phase diagrams were plotted based on the M-MIVM and VLE theory. The predicted VLE values were in good agreement with the corresponding experimental data determined in this study, indicating that the M-MIVM was reliable for indium-based alloys. The results of this work provided reliable experimental data and a thermodynamic model for the VLE study of In-based alloys, opening a new technique for the clean and efficient recycling of binary and multicomponent In-based alloys.

Investigation of Sn–Bi–In ternary solders with compositions varying from In–Sn eutectic to 59 °C ternary eutectic point

Investigation of Sn–Bi–In ternary solders with compositions varying from In–Sn eutectic to 59 °C ternary eutectic point

Characterization and investigation of performance of Sn–Bi alloy used as a thermal interface material

Characterization and investigation of performance of Sn–Bi alloy used as a thermal interface material

Preparation and performance of Sn-based composite solder joints by solid-liquid low-temperature solder bonding technology

In the era of big data, the advantages of 3D packaging are becoming increasingly significant. In addition, the mismatch between the coefficient of thermal expansion (CTE) of the PCB and BGA components leads to dynamic warpage of the system, and the expansion and innovation of low-temperature soldering have been a new trend. We developed a fully mixed solder joint of a SAC305(Sn-3.0Ag-0.5Cu wt.%) solder ball and Sn–58Bi(wt.%) solder paste by solid-liquid low-temperature solder bonding technology. The mixing degree and diffusion process of the two were calculated and simulated by mathematical calculation and COMSOL Multiphysics. The results show that a completely mixed solder joint can be obtained after reflow at 210 °C for 5 min. The average shear strength of the composite solder joints was 63.68 ± 1.12 MPa, which was about twice that of the single SAC305 and Sn58Bi solder joints, and the shear fracture was a composite mode of brittle and ductile fracture, which appeared in the IMC and the solder, respectively. After complete mixing, the solder wettability angle was less than 26.68°, with outstanding wetting properties. No phase transition occurred after aging, the distribution of each phase remained uniform, and no enrichment of the brittle phase was observed at the interface. The shear strength decreased slightly with aging time, and the reduction value was less than 10 MPa, which has good reliability.

Bimetallic Bi–Sn micro-/nanospheres@cellulose nanocrystal derived carbon aerogel composite anode for high-performance Mg-ion batteries

Magnesium-ion batteries (MIBs) have recently received widespread attention for energy storage. Nevertheless, the development of suitable anode materials remains significant challenges. Herein, a novel bimetallic Bi–Sn micro-/nanospheres homogenously embedded in cellulose nanocrystal derived carbon aerogel (CNC-CA@Bi–Sn) composite was constructed through a facile ion-induced gelation and in-situ thermal reduction processes. As an anode for MIBs, the CNC-CA@Bi–Sn electrode delivered high reversible specific capacity of 334 mAh g−1 after 100 cycles at 100 mA g−1, superior rate performance and long cycling lifespan with a reversible capacity of 187 mAh g−1 (ultralow capacity fade rate of 0.099% per cycle) at high current density of 1000 mA g−1 for 500 cycles. The excellent electrochemical performance should be attributed to the synergetic effects of unique three-dimensional (3D) nanoporous structure, dual phase microstructure and rich phase boundaries, biphase-based and carbon buffering matrices, which could effectively accommodate the large volume changes during the demagnesiation/magnesiation processes, significantly shorten diffusion lengths and improve the diffusion kinetics of Mg2+. This work provided a promising strategy for the design and synthesis of Bi–Sn biphasic material coupling with 3D carbon aerogel, which could be extended to other novel electrodes for high-performance MIBs.

Effect of Ni-modified reduced graphene oxide on the mechanical properties of Sn–58Bi solder joints

Sn–58Bi solder has great research value as a low-temperature solder. However, it still requires strengthening due to a lot of brittle Bi-phase, which reduces mechanical reliability. In this study, Ni-modified reduced graphene oxide (rGO@Ni) was prepared by heat reduction, and mechanical stirring was used to manufacture rGO@Ni-reinforced Sn–58Bi composite solder. The distribution, phase composition, and structural changes of graphene and Ni nanoparticles during enhancer synthesis were characterized in detail by Scanning Electron Microscope, Energy Dispersive Spectroscopy Raman and Fourier Transform Infrared spectra, X-ray Photoelectron Spectroscopy, X-ray Diffraction, and Transmission Electron Microscope. Besides, the morphology of intermetallic compound (IMC) layers of the composite solder/Cu interface was investigated. The thickness of the IMC layer decreases with the increase of rGO@Ni content. The microstructure analysis demonstrated that the rGO@Ni distributed near the IMC layer, which limits the diffusion of metal atoms and decreases the IMC layer's growth rate during the reflowing process. Besides, compared with Sn–58Bi solder alloys, the addition of 0.01 wt% rGO@Ni can increase the shear strength by up to 15%. However, when the content of rGO@Ni is more than 0.05 wt%, it agglomerates inside the composite solder, resulting in a decrease in the shear strength of the composite solder joint.

Microstructure and tensile properties of Sn–Bi–Co solder alloy

Microstructure and tensile properties of Sn–Bi–Co solder alloy

Phase characteristic and segregation related with corrosion on hypereutectic Sn–Bi solder under thermal storage and cycling corrosion test

Hypereutectic Sn-58%wt Bi solders were synthesized to observe phase change, corrosion and electrical endurance by various thermal storages. Initially, Cu6Sn5 IMC layer thickness is linear growth by Sn reacting with Cu joint, following, the Cu3Sn IMC starts to grow when the Cu6Sn5 is thicker enough to obstruct Cu inter-diffusing into solder. The segregation of Bi concentration gradient in eutectic phase is mitigated by homogenization treatment but corrosion resistance is deteriorated. Lump shape of SnO2 corrosive byproduct is initially observed, then the flower shape of Bi3O2 is found after Sn corroding completely. Moreover, phase change of solder related with current endurance is studied.

Surface tension of liquid mixtures and metal alloys. Positive and negative temperature coefficients in alloys with remarkably high surface density

The effect of temperature on the surface tension is examined in liquid alloys that combine a positive or negative temperature coefficient with gravity limitation of the surface concentration in the surface-active metal constituent. This is a restriction that is likely to occur in alloys where the metal with lower surface tension is much denser than the other component. Since there is a surface tension increase due to diminished segregation, the resultant temperature coefficient will depend on the superposition of two independent effects. Working in the framework of Butler’s thermodynamics for ideal surface phases, equations and methods of analysis are obtained to describe both effects. These developments are illustrated with alloys where the surface density is likely to attain the bulk density at certain compositions, namely the Al–Zn alloys that exhibits a negative temperature coefficient and the Sn–Bi, Ga–Bi, Ga-Pb and Cu–Pb alloys that present composition ranges with positive temperature coefficients. The specific concave down dγ/dT curves of liquid alloys are theoretically predicted. Furthermore, good estimates are obtained for systems with positive and negative temperature coefficients, except within a 50 K interval of phase transitions, or for systems showing large deviations from ideal behaviour.

Microalloying effects of Sb and Ag on the microstructural evolution of eutectic Sn–Bi alloys

Microalloying effects of Sb and Ag on the microstructural evolution of eutectic Sn–Bi alloys

Interfacial Microstructure and Shear Strength Improvements of Babbitt–Steel Bimetal Composites Using Sn–Bi Interlayer via Liquid–Solid Casting

To enhance the performance of Babbitt–steel bimetallic composites, bismuth (Bi) was incorporated into the Tin (Sn)-interlayer. Babbitt–steel bimetallic composites were created using the liquid–solid compound casting method in this study. Sn–Bi interlayer alloys with varying levels of Bi (1, 2, 3, and 4 wt.%) were created. The Babbitt-steel bimetallic composite’s bonding strength and interfacial microstructure were examined in relation to Sn-Bi interlayer alloys. The structure of the interface layer at the Babbitt–steel interface’s edge and center are significantly altered when Bi is added to the Sn interlayer. The relatively higher cooling rate near the edge led to the formation of clear unsolved Sn/Sn–Bi interlayers. Otherwise, the Sn–Bi interlayers in the middle were completely dissolved. By increasing the amount of Bi in the Sn–Bi interlayer alloy, the interfacial hardness of Babbitt-steel bimetallic composites increases by increasing Bi content in Sn–Bi interlayer alloy. Babbitt-steel bimetal composites’ shear strength increased to 28.27 MPa by adding Bi to the Sn interlayer using 1 wt.% alloying, with a 10.3% increase when compared with the reference pure Sn interlayer. Future research that aims to improve the production of Babbitt-steel bimetallic composites with high-quality and long-lasting bi-metal bonding ought to take into consideration the ideal pouring temperature, the preheating of the mold, and the addition of a minor amount of Bi (Bi ≤ 1) to the Sn-interlayer.

BEHAVIOR OF HEAVY METALS IN SOIL-CONDENSATE-PLANTS SYSTEM IN THE ULAN-UDE LANDFILLS

The impact of waste dumps on environmental components, i.e., soil, evaporating soil water (condensate) and plants is studied. It has been revealed that industrial and municipal waste dumps continue to affect significantly the environment after their closure. The behavior of heavy metals (Pb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg, and Cr) in soils, plants, and condensate in landfill areas and beyond them (the background) has been studied in detail. It has been found out that soils, plants and condensate at landfills are enriched in heavy metals as compared to the background sites. The degree of soil contamination at waste dumps depends on the reclamation stage of the latter. The landfill soils exceed the norms of maximum permissible concentrations for heavy metals by 1.1–90 times. Concentrations of heavy metals in plants exceed the background values from 1.1 to 104 times at all dumps. The maximum level of heavy metals in plants is exceeded for Zn, Cd, Cr. In the condensate sampled at the dumps, MPC is exceeded for Cu, Zn, and Hg. Based on the analysis results, the geochemical rows of heavy metal distribution in different landfill environments were compiled: in plants – Zn Cu Cr Ni Pb Cd Co Hg Sn Bi; in condensate – Zn Cu Ni Cr Pb Sn Co Hg Sb Cd Bi; in the soil – Zn Cr Cu Ni Pb Co Sb = Sn Cd. The distribution of heavy metals in the condensate and plants is similar. In these environments, contribution of Zn and Cu is more than 80%, contribution of Cr, Ni, Pb varies from 1 to 10%; contribution of Cd, Co, Sb, Sn, Bi, Hg is less than 1%. Heavy metals are distributed in soil according to a different pattern: the main contributors are Zn and Cr (their input is more than 50%), then go Ni, Cu, Co, and Pb (their content in soil varies from 1 to 50%), followed by Sb, Sn, and Cd (their content is less than 1%). Total pollution indices (Zc) of the soil, condensate and plants have been calculated for each landfill. Based on Zc, the landfills were grouped in a ranking series, which can form the basis for assigning the sequence of landfill reclamation measures.

Preparation of Microencapsulated Low‐Melting‐Point Sn–Bi Alloy for Latent Heat Storage

Low‐melting‐point SnBi alloy is a good phase change material (PCM) with high thermal conductivity and good stability for heat storage over 100 °C, which can be used for waste heat recovery and solar thermal storage. To solve the critical leakage problem and increase the heat transfer area of PCM, the fabrication of microcapsules of SnBi that are encapsulated by the stable SnO2 oxide shell is reported. The microcapsules are prepared by a two‐step method, in which the SnBi alloy microspheres are first treated by hot water or vapor and second heat treated under an oxygen atmosphere. The SnBi@SnO2 microcapsules are well sealed, and can endure a melting–solidification thermal cycle over 100 cycles with good stability. The microcapsules have a melting point of around 139 °C and an enthalpy of around 43 J g−1, similar to the theoretical values of SnBi. The simple preparation method and good thermal properties of the microcapsules ensures their application in heat storage and thermal management.

Alloying effects on inhibiting hydrogen evolution of Zn metal anode in rechargeable aqueous batteries

Alloying strategy is a feasible avenue to inhabiting the hydrogen reaction evolution (HER) of Zn anode. However, the general rule to select doping element is still unclear. In this study, the effects of Sn, Bi, Ag, and Co alloying on HER of Zn anode were investigated by experiments and DFT calculations. It is found that the doping of Sn or Bi is beneficial for inhabiting the HER compared with that of Ag or Co doping. The Gibbs free energy change (ΔG H *) and Zn atom binding energy calculations confirm that both Sn and Bi doping can inhabit the HER and dendrite formation. The Bader charge analyses indicate that Sn and Bi gain trivial electrons from neighbor Zn atoms. Bond length calculations show that the Sn and Bi will introduce local distortion into surrounding Zn atoms. The effects of alloying doping on the work functions of Zn anodes indicate that the Sn doping and Bi doping both have lower work functions than those of doping Ag and Co doping. Thus, it is proposed that the elemental doping with less charge transfer, inducing large local distortion and reducing the work function might be beneficial to inhabiting HER of Zn anode. • Doping of Sn or Bi is beneficial for inhabiting the HER of Zn anode. • Sn and Bi gain trivial electrons from neighbor Zn atoms compared with Ag and Co. • Sn and Bi doping introduce local distortion into surrounding Zn atoms. • Sn and Bi doping have lower work functions than those of Ag and Co doping.

Experimental investigation of melt infiltration and solidification in a pre-heated particle bed

Fluid infiltration, solidification, and remelting in a particle bed are complex phenomena that can occur in the lower head of a reactor pressure vessel (an in-vessel phenomenon) or in the reactor cavity below the vessel (an ex-vessel phenomenon) during a severe accident in a nuclear power plant. When the non-homogeneous corium, consisting of metal and oxide components, reheats, the lower-melting metals will melt first and move downward to the bottom of the reactor pressure vessel. This will change the global debris bed configuration and its physical and chemical properties, and thereby actively influence the accident progression, specifically the mode and timing of possible vessel failure and the melt characteristics upon release. Similar ex-vessel debris can form on the cavity floor below the vessel, which can threaten containment integrity if stable cooling is not established. In this paper, we present an experimental program employing recently constructed MRSPOD (multicomponent remelting, relocation, and solidification in porous debris) facility that mainly investigates melt infiltration, solidification, remelting, and relocation in a particulate debris bed. The facility uses a 12 × 130 cm2 (OD × Length) quartz tube in a cylindrical furnace and allows a debris bed to be configured, heated, and/or pressurized prior to fluid infiltration through the bed. The MRSPOD experiments were instrumented with thermocouples (TCs), fiber Bragg grating (FBG) sensors, laser sensor, video, and infrared cameras, which are essential in describing the overall melt infiltration and solidification behavior. Here, a eutectic Sn–Bi melt with superheat temperature between 50 and 70 °C is poured into a preheated particle bed consisting of 1.5-mm spherical particles made of either copper (Cu), Sn-coated Cu, stainless steel (SS), Sn-coated SS, and/or glass beads to study the effect of thermal properties and wettability on the melt infiltration. Moreover, melt infiltration into a single-layer, multi-layer, and two-columnar particle beds is performed. Measurements from TCs, FBGs, and observations from video cameras have revealed a non-linear kinetics of melt infiltration. Moreover, the extracted ingots after the experiments have shown the complex infiltration process under similar test conditions.

Reliability of laser soldering using low melting temperature eutectic Sn Bi solder and electroless Ni-electroless Pd-immersion Au-finished Cu pad

The demand for flexible wearable devices/substrates with miniaturization and improved integration in microelectronic devices has intensified the research interest in low-temperature laser soldering processes as an alternative to conventional reflow soldering processes owing to their advantages, such as local heating, non-contact heating, and short bonding time. In this study, we compared and evaluated the reliability of laser soldered and conventional reflow soldered joints using representative low melting temperature eutectic Sn Bi solder and thin electroless Ni-electroless Pd-immersion Au (ENEPIG)-finished Cu pads. Laser soldering was performed using various laser powers (130, 150, and 170 W) and times (2 and 4 s). Furthermore, an aging test was performed at 110 °C for 2000 h to evaluate the long-term reliability of the soldered joints. The mechanical properties, including the top and cross-sectional views and fracture surfaces, of the soldered joints were analyzed by conducting shear tests after aging. During laser soldering, various intermetallic compounds (IMCs) were formed at the joints depending on the applied energy. The metallization layer and Cu reacted with Sn in the solder after different aging durations, and additional IMCs were formed and grown. After aging for 2000 h, the shear strength decreased, and the interfacial IMC thickness increased. As the aging time increased, the fracture mode changed from an initial ductile fracture to brittle fracture (between the solder and IMCs and/or between IMCs and the Cu pad). The reflow soldered joints exhibited stable shear strength, resulting in ductile fracture until aging for 500 h. However, the shear strength decreased sharply after aging for 1000 and 2000 h, and Bi-segregation was observed after aging for 1000 h, resulting in inferior long-term reliability. After laser soldering at 150 and 170 W for 4 s, the strength of the samples decreased sharply after aging for 1000 and 250 h, respectively, and Bi-segregation was observed after aging for 2000 h. The shear strength of the sample laser soldered at 170 W for 2 s gradually decreased with increasing aging time and maintained a stable shear strength until aging for 2000 h. Therefore, laser soldering at 170 W for 2 s was considered as the optimal condition for long-term reliability. • Soldering properties of laser soldered Sn-58Bi/Au/Pd/Ni-finished Cu joints evaluated. • Laser soldering results were compared with conventional reflow soldered joints. • Various IMCs were formed depending on laser power and irradiation time. • Laser conditions with low applied energy displayed superior long-term reliability. • Selection of the optimal laser conditions is crucial to ensure reliable solder joints.

Correction: Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Correction: Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint