Pb-Sn Alloys Research Articles

A Computational-Experimental Investigation of the Mechanisms Responsible for the Enhanced CO2 Electrochemical Reduction of Dendritic Sn1Pb3 Alloy

The electrochemical conversion of CO2 into useful chemicals and fuels provides a means to recycle CO2 and achieve carbon balance.[1, 2] There are several value-added products that can be obtained from the electroreduction of CO2. Formic acid/formate is one of the useful products which has a strong market.[3] Formic acid/formate is widely used in several industrial sectors including pharmaceutical synthesis, pulp and paper production, textile finishing, as additive in animal feeds and as deicing agent.[4] In addition, formic acid/formate has been identified as a potentially hydrogen carrier and as a fuel for direct formate fuel cells (DFFC).[5, 6]Years of research have shown that various metals including Pb, Hg, Bi, and Sn produce HCOOH as a major product (high Faradic efficiency) during the electroreduction of CO2.[7-9] However, large onset potentials and high overpotentials should be applied when large current densities are achieved. Several investigations revealed that increasing the electrochemical active surface area of catalysts is effective to decrease the overpotenial.[10-12] However, Reducing the onset potential for CO2 electroreduction calls for more subtle manipulation of the catalyst composition since it is determined by the adsorption energies of reaction intermediates. Alloying with appropriate elements can affect the CO2 reduction onset potential.In this study, dendritic Sn-Pb alloy and Pb is investigated for CO2 electroreduction. The performances of these materials for the CO2 electroreduction will be evaluated. The DFT calculation results will be presented to explain the better performances of dendritic Sn1Pb3 alloy.

Electrochemical reduction of CO2 to Formic Acid on Pb-Sn Alloy Cathode

Carbon dioxide released to the atmosphere due to fossil combustion needs to be reduced to decrease the global warming effect. Electrochemical reduction of CO2 is one of promising technology to convert CO2 to various valuable compounds, reducing the amount of released CO2 to the atmosphere. Metal alloys are interesting material for cathode. In this preliminary work, a CO2 electrochemical reduction was performed on a Pb-Sn alloy cathode using catholyte of KHCO3 and NaHCO3 at various concentrations. An anode from Pt-Ir and H2SO4 0.1 M as anolyte were used in the experiment. The CO2 was bubbled into 400 mL catholyte at rate of 75 mL min-1. It was found that Pb-Sn alloy in KHCO3 electrolyte provides higher productivity and faradaic efficiency than in NaHCO3. Increasing overpotential from 0.1 V to 1 V increases both formic acid productivity and efficiency. The optimum amount of formic acid produced was 9400 μmol in catholyte KHCO3 0.5 M with faradaic efficiency of 67.19% and conversion of 0.326%.

Numerical modeling of a benchmark experiment on equiaxed solidification of a Sn–Pb alloy with electromagnetic stirring and natural convection

A three-phase volume averaged equiaxed model is applied to simulation of an experiment on solidification of the binary alloy Sn-10 wt.% Pb subjected to the electromagnetic stirring. The experiment, whose description was published earlier, was performed in a parallelepiped cavity under controlled cooling conditions and with real-time two-dimensional temperature measurement over a lateral surface of the cavity co-planar with direction of solidification. Applied numerical model treats motion of the liquid and equiaxed grains whose growth kinetics is taken into account and uses a double time step scheme to accelerate solution. Growth of columnar dendrite is not considered. It is shown that electromagnetic force acting in a direction opposite to the natural convection flow creates moderately turbulent flow in pure liquid which is treated with a realizable kε−ε model. It is demonstrated that calculated temperature distribution in the cavity well reproduces temperature maps reconstructed from thermocouples measurements throughout the experiment. Final macrosegregation map and distribution of density grain number are qualitatively similar to those obtained in the experiment. Variation of intensity of electromagnetic stirring in numerical model shows that this affects shape and localization of positive segregation region at the bottom of the cavity.

Experimental Investigations on Impact Toughness and Shear Strength of Lead Free Solder Alloy Sn–0.5Cu–3Bi–xAg

Lead is banned in alloy making citing toxicity concerns and environmental legislations. Researchers around the world were in search of new lead free solder alloys which could replace the old Sn–Pb alloy. Solder alloys are important electronic material used in electronics package industries. In this study, shear strength and impact toughness tests were conducted on Sn–0.5Cu–3Bi when different amounts of Ag (0.25, 0.5, 0.75, 1 wt%) is added. Shear strength test is done using micro force test system. Impact toughness test is done using Charpy impact test set up by finding the energy difference before and after impact. Ultimate shear stress is found to be increased from 17.3 to 23 MPa. Yield strength is found to be increased from 23.4 to 28 MPa. Impact toughness of the alloys increased from 10.4 to 11.3 J. EDAX analysis and mapping of the Sn–0.5Cu–3Bi–1Ag is also obtained Sn–0.5Cu–3Bi–1Ag is found to be having good improved shear strength and impact toughness than Sn–0.5Cu–3Bi.

Factorial design and design of experiments for developing novel lead free solder alloy with Sn, Cu and Ni

Inherent toxicity makes lead a banned material in solder alloy making process. Lead-tin alloy was a favorable alloy used for soldering in electronic packaging manufacturers. As a result of the ban on lead, electronics package industries were looking for novel lead free alloys which can substitute the conventional Sn-Pb alloy. Many alloys were discovered by the scientists. None of them were able to substitute the Sn-Pb alloy and become the market leader. In this paper a new composition with Sn, Cu and Ni is made to analyze which can potentially replace the lead containing solder alloy. Using the design of experiments method, the optimized composition of Cu and Ni is predicted. The full factorial design of experiments with two replications is used to find the optimized composition. Melting temperature, contact angle and hardness were taken as the critical output parameters. Results obtained shows that the optimum composition of Cu and Ni are 1 and 1% by wt.

Нарушение эффекта Кайзера при нагружении эвтектических сплавов сиcтемы Pb-Sn

This paper investigates acoustic emission under mechanical loading of Pb-Sn alloys. It is revealed that the Kaiser effect under repeated loading is not observed when certain concentrations of constituents lead to establishment of eutectic structures. The absence of acoustic emission memory effect in eutectic Pb alloys is explained. The proposed explanation is based on peculiar features of plastic flow caused by the motion of eutectic alpha- and beta-phase colonies at the joint interfaces.

Solidification Morphology and Bifurcation Predictions with the Maximum Entropy Production Rate Model

The use of the principle of maximum entropy generation per unit volume is a new approach in materials science that has implications for understanding the morphological evolution during solid–liquid interface growth, including bifurcations with or without diffuseness. A review based on a pre-publication arXiv preprint is first presented. A detailed comparison with experimental observations indicates that the Maximum Entropy Production Rate-density model (MEPR) can correctly predict bifurcations for dilute alloys during solidification. The model predicts a critical diffuseness of the interface at which a plane-front or any other form of diffuse interface will become unstable. A further confidence test for the model is offered in this article by comparing the predicted liquid diffusion coefficients to those obtained experimentally. A comparison of the experimentally determined solute diffusion constant in dilute binary Pb–Sn alloys with those predicted by the various solidification instability models (1953–2011) is additionally discussed. A good predictability is noted for the MEPR model when the interface diffuseness is small. In comparison, the more traditional interface break-down models have low predictiveness.

An Experimental Investigation on the Properties of Two Novel Ternary Solder Alloys Sn–0.5Cu–3Bi and Sn–1Cu–1Ni Replacing Lead

Lead is banned in the solder alloy composition, citing its inherent toxicity. The researchers were working towards the development of new lead free solder alloys which can replace the old Sn–Pb alloy. In the present paper two new solder alloys are introduced, Sn–0.5Cu–3Bi (96.5% Sn, 0.5% Cu, 3% Bi, all are % by wt) i.e. SCB305 and Sn–1Cu–1Ni (98% Sn–1% Cu–1% Ni) i.e. SCN110. The melting temperature of SCB305 and SCN110 are found to be 231.5 and 232.8°C, respectively. Therefore these two alloys can be used as solder material in electronic packages exposed to moderately higher temperature. Hardness of SCB305 and SCN110 are obtained as 19.8 and 16.1 HV. SCB305 and SCN110 have very good wetting characteristics with contact angle of 28.74° and good wetting characteristics with contact angle of 36.75°, respectively. Microstructure of SCB305 and SCN110 shows that Bi and Ni are evenly distributed in the Sn-matrix. The cost analysis revealed that SCB305 and SCN110 have cost of 23.05 and 20.65 $/kg. The properties of the new alloys were compared with that of SAC305 and SAC405. SCB305 and SCN110 are found to be perfect replacement of Sn–Pb alloy.

Experimental Investigations on Impact Toughness and Shear Strength of Novel Lead Free Solder Alloy Sn-1Cu-1Ni-XAg

Abstract Lead is known to be banned in alloy making, highlighting toxicity concerns and environmental legislations. Researchers and scholars around the globe were in immediate search of new lead free solder alloys which could potentially replace the old Sn-Pb alloy. In this comprehensive study, shear strength and impact toughness tests were conducted on Sn-1Cu-1Ni when different amounts of Ag (0.25, 0.5, 0.75 1 % by wt.) is added. Shear strength test is tested using micro force test system. Impact toughness test is analyzed using Charpy impact test set up by calculating the energy difference before and after impact. The study reveals that, Ultimate shear stress increased from 19 MPa to 21.3 MPa. Yield strength increased from 27.4 MPa to 29.7 Mpa. Impact toughness of the alloys increased from 9.4 J to 10.1 J. Thus, Sn-1Cu-1Ni-1Ag is found to have improved shear strength and impact toughness than Sn-1Cu-1Ni.

Sn-Mg lead-free solder alloy: Effect of solidification thermal parameters on microstructural features and microhardness

In the last decade, several studies have been developed on lead-free alloys as potential candidates to replace Sn–Pb alloys in soldering processes. Sn–Mg alloys arise as promising alternatives due to characteristics such as low melting point, low coefficient of thermal expansion, suitable mechanical properties, electrical resistivity and low cost of Mg as an alloying element. However, the literature is scarce on studies relating the microstructure features of unsteady state cooling conditions during solidification to the resulting properties of Sn–Mg alloys. It is of the utmost importance to know the influence of the solidification cooling rate on the representative length scale of the alloy microstructure, since it varies from about 0.4 to 8 °C s−1 in the soldering process. In the present study the Sn 2.1 wt%Mg eutectic alloy is solidified under unsteady state conditions over a nickel substrate for a range of solidification cooling rates from 0.5 to 12 °C s−1. The microstructure is shown to be formed by a mixture of β–Sn and fibrous Mg2Sn intermetallics (IMC) and an experimental growth law is proposed relating the interphase spacing between Mg2Sn fibers (λF) and the cooling rate. With the decrease in the cooling rate a pronounced decrease in the Mg2Sn IMC fraction is shown to occur; from about 46% to 23%. Consequently, hardness, that is shown to depend on both λF and Mg2Sn fraction, decreases significantly with the decrease in the solidification cooling rate.

Microstructure and mechanical property in laser welding-brazing of stainless steel and titanium alloy using 63Sn-37Pb alloy as filler metal

Laser welding-brazing of TC4 titanium (Ti) alloy to 304 stainless steel (SS) has been applied using 63Sn-37Pb alloy as filler metal. A new welding process for SS-Ti alloy joint was introduced on the basis of the controlling the formation of Ti–Fe intermetallics in the joint. One process was one pass welding involving creation of a joint with one fusion weld and one brazed weld separated by remaining unmelted SS. When laser beam on the SS side was 1.4 mm, SS would not be completely melted in joint. Through heat conduction of unmelted SS, the filler metal melted occurred at the SS-Ti alloy interface. A brazed weld was formed at the SS-Ti alloy interface with the main microstructure of Fe3Sn+Fe3Sn2, (βSn, Pb), (βSn)+Sn2Fe, and (βSn)+Sn3Ti2. The joint fractured at the brazed weld with the maximum tensile strength of 108 MPa.

Temperature and strain-rate dependent constitutive model for prediction of thermal cycling life

With temperature cycling as the characteristic working environment of aerospace electronic chips, various constitutive models have been proposed to predict the failure problems of solder joints. However, most researchers adopted only a set of constant parameters to describe the solder joint material properties throughout the temperature cycles, which is obviously unreasonable concerning the possible wide range of working temperature. In fact, with the changing temperature and strain rate, some material parameters will correspondingly evolve as observed in the experiments. In this paper, the framework of the Anand constitutive model is adopted to verify the effect of material parameters of different temperatures and strain rates on the mechanical properties of materials under the scenario of temperature cycling. The lead-containing solder alloy 63Sn37Pb material that is most widely used in aerospace is selected as the solder material for the interconnection structure. In addition, a typical plastic ball grid array (PBGA) packaging structure is used to analyze the influence of the constitutive model parameters on the PBGA thermal fatigue life. Based on experimental data, seven sets of constitutive model parameters with different temperatures (-55°C~125°C) under a region of low strain rate (1×10-4/s) were employed to compare the mechanical properties of the material under temperature cycling. The sensitivity analysis of material parameters is performed and the underlying mechanism are also explained so that the present study can promote the optimization of the constitutive model in numerical simulations in practice.

Measurement of Electrical Properties of Sn-Bi-In Alloys

The electrical properties of Sn-Bi-In ternary alloys were measured using the four-point probe method along three cross sections of the phase diagram (ratio of tin to bismuth 2:1, 1:1 and 1:2). The current–voltage relationship was measured for all the alloys from 38°C to 90°C. The variation of electrical resistivity with temperature was studied for all the ternary alloys and Pb-Sn binary alloys using the four-point probe method. The resistivity of ternary alloys was compared with Pb-Sn binary alloys. The resistivity of a few of the ternary alloys, 7Sn-3Bi-90In, 5Sn- 5Bi-90In and 3Sn-7Bi-90In, were close to the values of Pb-Sn alloys.

Influence of Indium on Microstructure and Properties of Sn-Pb Binary Alloy Applied in Photovoltaic Ribbon

In this work, the conductivity, melting point, microstructure, spreading behavior, and mechanical properties of three types of Sn-Pb-In(indium) alloys are investigated along with Sn60Pb40 alloy as a reference. The results show that the In element improves the comprehensive properties of the Sn-Pb alloys. The maximum conductivity of the Sn-Pb-In alloys is 7.08 MS/m when the content of the In element is 3 wt.%. With an increasing content of the In element, the melting points of the Sn-Pb-In alloys gradually decrease from 183 to 166 °C. The microstructures of the alloys are refined with the addition of In. The intermetallic compound (IMC) InSn4 is only found in Sn60Pb34In6, except for the α-Pb and β-Sn phases. A spread test shows that only IMC Cu6Sn5 is present at the Cu/solder interface of the solder joints. The Sn60Pb34In3 solder joint shows the highest ultimate tensile strength of 54 MPa. The microhardness of the alloys slightly increases from 12.76 HV0.05 to 13.56 HV0.05 with the In content increasing from 0 to 3 wt.%, while a sharp increase to 15.53 HV0.05 is observed when the amount of In exceeds 3 wt.%.

Theoretical study on Sn–Sb-based lead-free solder by ab initio molecular dynamics simulation

Abstract

Sustainable extraction of lead and re-use of valuable metals from lead-rich secondary materials

Traditional lead metallurgy, a highly complicated lead extraction process for valuable metal recovery, has exhausted resources and produced a variety of hazardous wastes that are extremely harmful to the environment and unfavorable to the sustainable development of the lead industry. Vacuum metallurgy has become a promising emerging technology contributing to refining primary metals and the recovery of secondary nonferrous metal wastes. The technology is therefore relevant in the context of a transition to a more environmentally friendly circular economy. There is a growing interest in using vacuum distillation for extraction of Pb and valuable metals recovery from lead-rich secondary materials including crude lead, waste Pb-Sn alloy (WPSA) and lead anode slime (LAS). Results indicated that vacuum extracted lead (99.5% Pb) was obtained from crude lead (92.88%) using the two stage high-low temperature vacuum distillation process. Removals of 99.99% for Cu, 99.50% for Sn, and 98.00% for Ag, were achieved respectively. The valuable metals of Ag, Cu and Sn were recovered and concentrated in the final residue. Vacuum separation results of WPSA demonstrated that the purity of Pb reached 99.4% and recovery of Sn was above 86.0%. A novel integrated smelting-vacuum method is proposed here to reuse LAS. Copper and Ag were successfully enriched in the residues whilst Pb was collected in volatiles. The appropriate vacuum process effectively extracted Pb whilst recycling valuable metals, in a sustainable and environmentally friendly manner.

Effect of Aging Treatment on Microstructural Evolution of Rapidly Solidified Eutectic Sn-Pb Alloy Powders

The microstructural stability of rapidly solidified eutectic Sn–Pb alloy solder powders was investigated through aging at room temperature (25 °C) and temperatures of 40 °C–120 °C. The coarsening behavior of the Pb-rich phase both at room and elevated temperatures was observed. The evident coarsening of the Pb-rich phase was detected upon storage after 40 days. At elevated temperatures, a similar sequence of Pb-rich phase coarsening was observed; however, it occurred substantially more quickly. Pb-rich coarsening rate kinetics at different temperatures were estimated using the Arrhenius equation. The apparent activation energy was 45.53 ± 4.23 KJ/mol, which indicates that grain boundary diffusion is a crucial mass transport mechanism controlling Pb-rich phase coarsening under annealing.

On understanding bandgap bowing and optoelectronic quality in Pb–Sn alloy hybrid perovskites

Experimental insights regarding bandgap evolution in hybrid perovskite alloys and the optimal small-bandgap absorber composition desired for next-generation perovskite tandems.

Technical and environmental assessment of selective recovery of tin and lead from waste solder alloy using direct anodic oxidation

The current study aimed the selective recovery of tin and lead from waste SnPb alloy obtained as a secondary stream in the recovery process of copper from waste printed circuit boards. The recovery of the two metals was achieved through selective direct anodic dissolution of the waste SnPb alloy samples in H2SO4 solutions coupled with the simultaneous electrowinning of a tin rich cathodic deposit. The optimal operating conditions were identified based on the influence of current density, H2SO4 concentration and electrolyte flow rate on the main technical performance indicators. The most favorable operating conditions for the electrochemical process were obtained at 0.5 M H2SO4 concentrations, 60 A/m2 current density and at a flow rate of 45 mL/min. Based on the experimental results the process was scaled-up, modeled and simulated using process flow modeling software CHEMCAD. The mass balance data corresponding to the recycling of 100 kg/h waste solder in the identified optimal operating conditions was used for the environmental assessment of the process. The General Effect Indices, for the input and output streams of the process, obtained through the Biwer-Heinzle method indicate that the developed recovery process it is not only efficient but environmental friendly as well.

Separation of metals from metal-rich particles of crushed waste printed circuit boards by low-pressure filtration

In recent years, recovery of metals from electronic waste (e-waste) within China has become increasingly important due to potential supply risk of strategic raw material and environmental concerns. Printed circuit boards (PCBs) contain lots of valuable metals together with plenty of hazardous materials, which are considered both an attractive secondary resource and an environmental contaminant. Pressure filtration is an effective and environmentally friendly method for separating and recycling comminuted PCBs. Present work is focused on the recovery of metals from PCBs by low-pressure filtration separation. A two-stage separation process was adopted to selectively recover Pb-Sn and Cu alloys at different temperatures. The results showed that the temperature and pressure had great influence on the recovery of metals in the separation process. After the two-stage separation process, the total recoveries of Pb, Sn, Cu and Zn were 79.96%, 89.91%, 88.80% and 68.57% respectively, when the temperature is 1350 °C and the pressure is 0.30 MPa. This is a high-efficiency, short-flow, clean-production, and environmental-friendliness that can improve the recovery of metals and realize the reuse of waste resources.