Sn-Bi Alloys Research Articles

Doping Process of 2D Materials Based on the Selective Migration of Dopants to the Interface of Liquid Metals

The introduction of trace impurities within the doping processes of semiconductors is still a technological challenge for the electronics industries. By taking advantage of the selective enrichment of liquid metal interfaces, and harvesting the doped metal oxide semiconductor layers, the complexity of the process can be mitigated and a high degree of control over the outcomes can be achieved. Here, a mechanism of natural filtering for the preparation of doped 2D semiconducting sheets based on the different migration tendencies of metallic elements in the bulk competing for enriching the interfaces is proposed. As a model, liquid metal alloys with different weight ratios of Sn and Bi in the bulk are employed for harvesting Bi2 O3 -doped SnO nanosheets. In this model, Sn shows a much stronger tendency than Bi to occupy surface sites of the Bi-Sn alloys, even at the very high concentrations of Bi in the bulk. This provides the opportunity for creating SnO 2D sheets with tightly controlled Bi2 O3 dopants. By way of example, it is demonstrated how such nanosheets could be made selective to both reducing and oxidizing environmental gases. The process demonstrated here offers significant opportunities for future synthesis and fabrication processes in the electronics industries.

Improvements of microstructure and hardness of lead-free solders doped with Mo nanoparticles

Two kinds of composite lead-free solders were prepared by adding Mo nanoparticles in Sn3.0Ag0.5Cu and Sn58Bi alloys, respectively. It was found that the microstructures of both composite solders were refined and the hardnesses of solders were significantly enhanced due to the addition of Mo nanoparticles. The mechanism of the effects of Mo nanoparticles on the microstructure and hardness was analyzed.

Perovskite solar cell based on double-layer Ag/SnBi alloy as cathode

Herein, a low-melting point tin-bismuth (SnBi) alloy film combined with a silver layer was introduced to fabricate the inverted planar perovskite solar cells. SnBi alloy was prepared by high temperature melting method and was characterized by metallurgical microscope, XRD, SEM, DTA, XPS methods. The influence of silver thickness on the performance of perovskite solar cells was studied. The optimized perovskite solar cells based on 20 nm Ag and 80 nm SnBi show a power conversion efficiency of 13.52%, involving a 19.6% increase compared to the control device. The double-layer electrode can not only reduce the charge transfer resistance, increase the extraction efficiency of the charge, improve the photovoltaic performance of the device, but also improve the stability of the device in the environment.

Improvement on the mechanical properties of eutectic Sn58Bi alloy with porous Cu addition during isothermal aging

A comparison of the microstructure, interfacial IMC layer, shear behavior and hardness of the Sn58Bi, SnBi@110P-Cu/Cu and SnBi@500P-Cu/Cu solder joints was carried out during isothermal aging in this study. Experimental results reveal that the regions enclosed by Cu frames in SnBi@110P-Cu/Cu exhibit more refined microstructure and higher hardness before and after aging. In contrast, the hardness of the aged SnBi@500P-Cu solder bulk is closer to the SnBi eutectic solder due to their similar microstructure. With the aging time prolonging, β-Sn and Bi-rich phases do not only coarsen in solder joints, but also lead to the rise of the thickness of the interfacial IMC layers. The addition of porous Cu can suppress the formation of voids at the soldering interface and improves the shear strength of the SnBi/Cu solder joints during the aging process. The shear strength of the SnBi@500P-Cu/Cu solder joint is higher than the other two before and after aging.

Local solidification thermal parameters affecting the eutectic extent in Sn-Cu and Sn-Bi solder alloys

PurposeOverall, selection maps about the extent of the eutectic growth projects the solidification velocities leading to given microstructures. This is because of limitations of most of the set of results when obtained for single thermal gradients within the experimental spectrum. In these cases, associations only with the solidification velocity could give the false impression that reaching a given velocity would be enough to reproduce a result. However, that velocity must necessarily be accompanied by a specific thermal gradient during transient solidification. Therefore, the purpose of this paper is to not only project velocity but also include the gradients acting for each velocity.Design/methodology/approachCompilation of solidification velocity, v, thermal gradient, G, and cooling rate, Ṫ, data for Sn-Cu and Sn-Bi solder alloys of interest is presented. These data are placed in the form of coupled growth zones according to the correlated microstructures in the literature. In addition, results generated in this work for Sn-(0.5, 0.7, 2.0, 2.8)% Cu and Sn-(34, 52, 58)% Bi alloys solidified under non-stationary conditions are added.FindingsWhen analyzing the cooling rate (Ṫ = G.v) and velocity separately, in or around the eutectic composition, a consensus cannot be reached on the resulting microstructure. The (v vs. G) + cooling rate diagrams allow comprehensive analyzes of the combined v and G effects on the subsequent microstructure of the Sn-Cu and Sn-Bi alloys.Originality/valueThe present paper is devoted to the establishment of (v vs. G) + cooling rate diagrams. These plots may allow comprehensive analyses of the combined v and G effects on the subsequent microstructure of the Sn-Cu and Sn-Bi alloys. This microstructure-processing mapping approach is promising to predict phase competition and resulting microstructures in soldering of Sn-Cu and Sn-Bi alloys. These two classes of alloys are of interest to the soldering industry, whereas manipulation of their microstructures is considered of utmost importance for the metallurgical quality of the product.

An examination of strain weakening and self-annealing in a Bi-Sn alloy processed by high-pressure torsion

The high pressure torsion (HPT) process was performed on a Bi-Sn eutectic alloy up to 10 revolutions and the materials were stored at room temperature for durations up to 91 days in order to investigate the strain weakening and self-annealing behaviour of the alloy. The results show that HPT processing leads to significant grain refinement and enhanced superplasticity in the alloy. When the material is stored at room temperature, the grain size increases and the microhardness also increases producing a near linear relationship between grain size and microhardncess. This effect is attributed to the enhanced creep behaviour of the Bi-Sn alloy after HPT processing.

Enhanced electrochemical properties of lithium-tin liquid metal battery via the introduction of bismuth cathode material

The performance of a liquid metal battery can be significantly enhanced by lowering the cell operating temperature through alloying of the cell components. The effect of alloying pure tin metal, a cathode material for liquid metal batteries, on electrochemical properties is investigated by preparing a Li|Sn-Bi (Sn:Bi = 56:44 at%) battery cell. The Li|Sn-Bi cell achieves mean voltages of 0.856 and 0.683 V during charging and discharging, respectively, at 100 mA cm−2, which are 0.039 and 0.067 V higher than those of the Li|Sn cell. The Li|Sn-Bi cell exhibits a high rate capability owing to the low charge-transfer resistance between the liquid electrodes and liquid electrolytes. The charge and discharge capacity losses are 6.5% and 18.6%, respectively, at 1000 mA cm−2 compared with those at 100 mA cm−2. The Li|Sn-Bi cell can be discharged even at 1000 mA cm−2 owing to an increase in the mean discharge voltage by the alloying of tin with bismuth. The Li|Sn-Bi cell also exhibits improved cycle performance, with a capacity retention of 94.2% after 1000 cycles and a capacity decay of 0.0065% per cycle. This is attributed to the lack of formation of intermetallic byproducts between Bi and the stainless steel case and suppression of the side reaction between Sn and stainless steel by bismuth in the Sn-Bi lamellar microstructure. Thus, using a Sn-Bi alloy as the positive material significantly improves battery performance, making the Li|Sn-Bi cell a good candidate for stationary storage applications.

Improvements in mechanical properties of Sn–Bi alloys with addition of Zn and In

In order to improve the mechanical properties after thermal aging of an Sn–45Bi–2.6Zn (SBZ) alloy, which we had proposed in a previous study, in this study, we prepared Sn–Bi–Zn–In alloys and investigated the effects of the addition of In and Zn on their microstructure and mechanical properties before and after thermal aging. We found that the addition of In suppressed the microstructural coarsening of SBZ during thermal aging and can potentially help reduce the brittleness of Sn–Bi alloys. Moreover, the addition of In had significant effect on the elongation of SBZ. We theorized that the segregation of Zn at the Sn/Bi phase boundary and the formation of a solid solution of In in the Sn phase are responsible for this result. Thus, the investigated alloys have potential for use as lead-free solder materials in the electronics industry. • The addition of Zn and In in a trace amount was effective in suppressing the microstructural coarsening of Sn–Bi alloys during thermal aging. Moreover, the addition of In had a significant effect on the elongation of the alloys. •The segregation of Zn at the Sn/Bi phase boundary and the formation of a solid solution of In in the Sn phase are responsible for the phenomenon of microstructural retention during thermal aging.

Metallization of polymers by cold spraying with low melting point powders

Polymers and polymer composites have been increasingly used due to their low density and high specific strength; however, their low electrical conductivity has limited their further application. Cold spray has recently been proven to be a feasible approach to metallize polymers. Previous results have shown that tin can be cold sprayed onto polymeric substrates when spraying with a low-pressure cold spray system at gas temperatures close to the melting point of tin. The successful deposition of tin was partly attributed to the tin reaching its incipient melting point. In this work, three low melting point metal powders, namely, Sn, Sn-Zn alloy, and Sn-Bi alloy, were cold sprayed onto five widely used engineering polymers . Different combinations of gas temperature and gas pressure were assessed. Results show that decreasing the melting points of the feedstock powders can improve their deposition efficiency on polymeric substrates, due to a higher degree of particle melting. Among the five polymers, the high-toughness ultra high molecular weight polyethylene and polycarbonate were relatively difficult to metallize. • SnZn and SnBi powders with lower melting points than Sn were cold sprayed on polymeric substrates. • Five common engineering thermoplastic polymers (ABS, Nylon, PC, PE, and PP) were metallized using low melting point powders. • Particle melting facilitated the deposition and inter-particle bonding, resulting in high deposition efficiency. • SnBi coatings exhibit higher adhesion to ABS than Sn when spraying at 300°C and 60 psi.

Experimental Determination of the Activities of Liquid Bi-Sn Alloys

The paper addresses the measurement of the partial molar Gibbs energy ( $$\Delta {\stackrel{-}{G}}_{Bi},\Delta {\stackrel{-}{G}}_{Sn}$$ ), thermodynamic activity ( $${a}_{Bi},{a}_{Sn}$$ ) and the activity coefficient ( $${\gamma }_{Bi ,}{\gamma }_{Sn}$$ ) of the Bi-Sn binary system at 600 and 903 K. The experiments were carried out in an H-shaped electrochemical cell based on the measurement of electromotive force with the reversible electrode–solid electrolyte. The measuring electrode was made of Bix-Sn1−x alloys with x ranging from 0.1 to 0.9, step 0.1. The reference electrode was manufactured from pure bismuth, while the electrolyte was a mixture of 17% moles KCl and 83% moles SnCl2 (selected because it contains free ions Sn and the melting temperature of the electrolyte (563 K). To obtain reliable experimental data, each measurement was repeated five times and the standard deviation/error was calculated. Based on error propagation law, the mathematical expression of the compound uncertainty for each quantity addressed in the paper was derived. An innovative derivation is presented for the compound uncertainty (uc) of γSn. The values of the $$\Delta {\stackrel{-}{G}}_{Bi},\Delta {\stackrel{-}{G}}_{Sn}$$ , aBi, aSn, γBi and γSn are accompanied by their expanded uncertainty having a 95% confidence level. The novelties addressed in the paper are the values of ΔGBi, ΔGSn, aBi, aSn, γBi and γSn in the Bi-Sn binary system at 600 and 903 K.

Thermomechanical fatigue resistance of low temperature solder for multiwire interconnects in photovoltaic modules

Novel interconnect technologies leveraging low melting temperature solders, such as multiwire interconnects, are being deployed in photovoltaic (PV) modules for improved reliability through interconnect redundancy and lower thermal loads during interconnection and lamination. However, the equivalency of standardized accelerated testing to field conditions has not yet been established for these emerging technologies. In this study, the thermomechanical fatigue resistance of low temperature solder alloys is investigated and compared to that of conventional SnPb to assess the acceleration behavior of these alloys. While InSn is shown to have sufficient thermomechanical fatigue resistance on the order of that of SnPb, these results indicate Sn–Bi alloys may have poor thermomechanical fatigue resistance at field conditions. The results also show that Sn–Bi alloys have thermal cycling acceleration factors of less than one. This indicates that the standardized accelerated thermal cycling test, such as that in IEC 61215, will produce misleading results for Sn–Bi alloys and that unique testing is required for this PV module architecture. Though accelerated thermal cycling may be a meaningful qualification test for SnPb solder joints, these results suggest that mechanical loading may be a more appropriate test for Sn–Bi multiwire interconnects. This is due to the distinct processing and geometry of multiwire interconnects which may allow for mechanical, rather than strictly metallurgical interconnections.

Determination of bulk and surface properties of liquid Bi-Sn alloys using an improved quasi-lattice theory

Abstract The thermodynamic properties of Bi-Sn were studied at 600 and 900 K using a quasi-lattice theory. After successful fitting of Gibbs free energies of mixing and thermodynamic activities, the fitting parameters were used to investigate the enthalpy of mixing, the entropy of mixing, concentration fluctuations, Warren-Cowley short-range-order parameter, surface concentrations and surface tensions of the binary systems. Positive and symmetrically shaped enthalpies of mixing were observed in all composition range, while negative excess entropies of mixing were observed. Bi-Sn showed a slight preference for like-atoms as nearest neighbours in all composition range. The nature of atomic order in Bi-Sn at 600 and 900 K appeared similar. The highest tendency for homocoordination exists at composition where mole fraction of Bi is about 40%. It was also observed that Bi (whose surface tension is lower than that of Sn) has the highest surface enrichment in the Bi-Sn systems. Unlike many previous applications of the quasi-lattice theory where constant values were used to approximate coordination numbers, temperature and composition-dependent coordination numbers were applied in this work.

Analysis of Sn-Bi Solders: X-ray Micro Computed Tomography Imaging and Microstructure Characterization in Relation to Properties and Liquid Phase Healing Potential.

This work provides an analysis of X-ray micro computed tomography data of Sn-xBi solders with x = 20, 30, 35, 47, 58 wt.% Bi. The eutectic thickness, fraction of eutectic and primary phase are analyzed. Furthermore, the 3D data is evaluated by means of morphology parameters, such as, shape complexity, flatness, elongation and mean intercept length tensor. The investigated alloys are categorized in three groups based on their morphology, which are described as “complex dominant”, “complex- equiaxed” and “mixed”. The mechanical behavior of Sn-Bi alloys in the semi-solid configuration and the correlation with microstructural parameters are discussed. A varying degree of geometric anisotropy of the investigated alloys is found through the mean intercept length tensor. Representative volume element models for finite element simulations (RVE-FEM) are created from tomography data of each alloy to analyze a correlation of geometric and elastic anisotropy. The simulations reveal an elastic isotropic behavior due to the small difference of elastic constants of primary and eutectic phase. A discussion of properties in the semi-solid state and liquid phase healing is provided.

Based on the technology of electromagnetic force driving and differential pressure control for producing solder balls

Uniform solder balls are widely used in 3D Printing and electronic packaging. Therefore, it needs a simple method for producing uniform solder balls at a higher quality. In this article, a novel and simple method was presented to produce uniform solder balls by the technology of electromagnetic force driving and differential pressure control. The results indicated that the uniform solder balls of Sn-58Bi alloy could be produced by two different modes of differential pressure control. The solder balls with a spherical degree between 0 and 3% and diameter with a mean variation of 4% were produced at different diameter and reasonable test parameters.

Сверхпроводимость эвтектического сплава Bi-Sn

We present results of studies of superconductivity in a binary Bi-Sn alloy of the eutectic composition (57 wt.% Bi, 43 wt.% Sn). Temperature and field dependences of the dc magnetization were measured within a temperature range from 1.8 to 20 K in magnetic fields up to 20 kOe using a Quantum Design MPMS3 SQUID magnetometer. A two-stage phase transition with temperatures of the diamagnetism onset of 8.55 and 5.1 K was observed. A phase diagram was constructed. The coherence length for the first stage was estimated. The field dependence of the irreversibility temperature was found. Critical dependencies showed a positive curvature which was treated within the framework of the proximity effect model.

Microstructure and mechanical properties of Sn–58Bi eutectic alloy with Cu/P addition

Sn–(58-x) Bi–x Cu/P ternary alloys were prepared by downward continuous casting, and the microstructure of the alloy was characterized using scanning electron microscopy (SEM), x-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The results show that the addition of Cu and P can refine the eutectic structure and form rod-shaped Cu6Sn5 and P3Sn4 phases distributed in Sn matrix. The refined eutectic structure can be observed in Sn–(58-x) Bi–x Cu/P alloys, and this results in the elongation at break increases up. In addition, the wettability of Sn–58Bi alloy increases on Cu substrate with the addition of Cu and P elements. The improvement of the wettability of Sn–58Bi alloy by the addition of Cu element can be attributed to the increase of Cu-Sn IMC nucleation and growth rate. The addition of P element in Sn–58Bi alloy can improve its anti-oxidation performance, which is beneficial to the improvement of its wettability.

Surface Properties of Indium, Tin, Bismuth, and Binary In–Bi and Sn–Bi Alloys

Surface Properties of Indium, Tin, Bismuth, and Binary In–Bi and Sn–Bi Alloys

Enhancement of electrochemical and thermal bonding reliability by forming a Cu3Sn intermetallic compound using Cu and Sn–58Bi

Cu–Cu bonding was successfully achieved through the transient liquid phase sintering (TLPS) bonding method using Cu and an eutectic Sn–Bi alloy. The bonding process was performed for total bonding process time of 2 h under a pressureless condition in air. The bonding temperature was 220 °C considering that the Cu6Sn5 intermetallic compound (IMC) and Bi react at 195.9 °C to transform into Cu3Sn and a liquid. The shear strength of Cu-70(Sn–58Bi) was approximately 22.06 MPa with the formation of the Cu3Sn. The residual eutectic Sn–Bi structure remained at Cu-90(Sn–58Bi), and the voids were largely observed at Cu-50(Sn–58Bi). In case of Cu-70(Sn–58Bi) and Cu-50(Sn–58Bi), the remelting temperature increased to 270 °C by the IMC reaction between Cu and Sn. On the other hand, the remelting temperature of Cu-90(Sn–58Bi) joint remained at 139 °C due to residual eutectic Sn–Bi structure. The salt spray test was conducted at 35 °C under the 5% NaCl condition for 24, 48, and 96 h to evaluate the bonding reliability under the salt spray condition. The corrosion behavior was evaluated using the electrochemical impedance spectroscopy measuring method. In addition, the thermal bonding reliability was investigated through a high-temperature storage test at 200 °C for 100, 500, and 1000 h. Analysis results of the experiment showed that the electrochemical and thermal bonding reliabilities were improved with the Cu3Sn formation owing to its high resistance properties under the salt spray and high-temperature conditions.

Nanoscale Visualization of Phase Transition in Melting of Sn-Bi Particles by In situ Hard X-ray Ptychographic Coherent Diffraction Imaging.

The phase transition in the melting of Sn–Bi eutectic solder alloy particles was observed by in situ hard X-ray ptychographic coherent diffraction imaging with a pin-point heating system. Ptychographic diffraction patterns of micrometer-sized Sn–Bi particles were collected at temperatures from room temperature to 540 K. The projection images of each particle were reconstructed at a spatial resolution of 25 nm, showing differences in the phase shifts due to two crystal phases in the Sn–Bi alloy system and the Sn/Bi oxides at the surface. By quantitatively evaluating the Bi content, it became clear that the nonuniformity of the composition of Sn and Bi at the single-particle level exists when the particles are synthesized by centrifugal atomization.

Comparative Evaluation of Bismuth-Silver and Bismuth-Tin Alloys for Plug and Abandonment

Summary As an alternative to cement, the feasibility of bismuth-tin (BiSn; contains 58 wt% Bi and 42 wt% Sn, abbreviations are not in stoichiometric ratio) as a low melting-point plug has been tested by Zhang et al. (2020) for rigless plug-and-abandonment (P&A) service of offshore wells. Similar to BiSn, bismuth-silver (BiAg; contains 97.5 wt% Bi and 2.5 wt% Ag, abbreviations are not in stoichiometric ratio) also exhibits desirable properties compared with Portland cement. However, because of its greater melting point, BiAg has potentially a wider application than BiSn, especially in deep formations. In the present study, we investigate the feasibility of BiAg alloy for P&A. The bond quality of the alloy-shale cores is evaluated through shear, tensile, push-out, and permeability tests, and compared with those of BiSn alloy-shale and cement-shale cores. To avoid phase change-induced shale damage at elevated temperature while setting BiAg plugs, water was first extracted with supercritical carbon dioxide (CO2). For shear and tensile tests with pinhole-anchored BiAg, the ultimate strength and modulus were measured as a function of anchor points at different temperatures (21, 80, and 110°C). For the push-out tests, shale samples of smooth, rough, and pinholed surfaces were prepared with the BiAg alloy plug. In general, we find that, without anchors, bond failure precedes shale failure. Results for cement-shale cores are also reported for comparison. We contrast the performance of BiAg and BiSn alloys at 21, 65, 80, and 110°C to determine the crossover temperature for deployment suitability.