Lead-free Solder Alloys Research Articles

Comparison of the Young’s modulus of the lead free solder alloy Sn-Ag3.8-Cu0.7 determined by hot tensile tests, ultrasonic measurements and [formula omitted]-Sn single crystal calculations

Sn-based solders are known for their tendency to form coarse grained microstructures. In combination with the high elastic anisotropy of β-Sn, the overall elastic properties and their interpretation require a careful discussion of the structure–property-relationship as elastic constants are often important input parameters for creep or fatigue models. This study therefore investigates the influence of microstructure and testing method on the Young’s modulus E for the widespread lead free solder alloy Sn-Ag3.8-Cu0.7 (SAC387) using bulk specimens. Due to its already high homologous temperature at room temperature (Thom≈ 0.6 = T/Tm for Tm being the melting temperature), hot tensile tests generally bear the risk of superimposed creep deformation. Mechanical testing becomes even more challenging, since yield strengths are usually low for these alloys. Consequently, in addition to the hot tensile tests executed for the engineering strain rate ϵ̇e=1⋅10−3 s−1, two supplemental methods are used to determine the Young’s modulus comprising of the dynamic resonance frequency measurement and the calculation of the Young’s modulus based on single crystal compliance data of the majority phase β-Sn.Young’s moduli yielded from dynamic resonance frequency measurement and calculations based on single crystal compliance data showed comparable results of (E35 °C≈ 55 GPa, E80 °C≈ 51 GPa and E125 °C≈ 48 GPa). Hot tensile tests showed similar data with the largest deviation at 80 °C, where E80 °C≈ 53 GPa was determined. These absolute values and their temperature dependence can be attributed to the microstructure of the cast specimens which show a general preferred orientation of β-Sn grains close to <110> after analysis via electron backscattered diffraction (EBSD). A comparison with literature data revealed significant differences in the Young’s moduli which are likely to be attributed to differences in the preferred orientation of β-Sn grains.

Effect of Composition on Structural, Mechanical, and Wetting Properties of Sn-40Bi-xAg Lead-Free Solder Alloys for Green Electronics

Effect of Composition on Structural, Mechanical, and Wetting Properties of Sn-40Bi-xAg Lead-Free Solder Alloys for Green Electronics

Effects of Bi Doping on Zn-Rich Phase Evolution and Physical and Chemical Properties of Sn-6.5Zn Lead-Free Solder Alloy

Effects of Bi Doping on Zn-Rich Phase Evolution and Physical and Chemical Properties of Sn-6.5Zn Lead-Free Solder Alloy

EBSD characterization of Ag3Sn phase transformation in Sn–Ag lead-free solder alloys: a comparative study before and after heat treatment

EBSD characterization of Ag3Sn phase transformation in Sn–Ag lead-free solder alloys: a comparative study before and after heat treatment

Investigation of the mechanical properties of lead-free Sn-58Bi solder alloy with cobalt addition through flux doping

PurposeThis study aims to investigate the effect of incorporating cobalt (Co) into Sn-58Bi alloy on its phase composition, tensile properties, hardness and thermal aging performances. The fracture morphologies of tensile-tested solders are also investigated to correlate the microstructural changes with tensile properties of the solder alloys. Then, the thermal aging performances of the solder alloys are investigated in terms of their intermetallic compound (IMC) layer morphology and thickness.Design/methodology/approachThe Sn-58Bi and Sn-58Bi-xCo, where x = 1.0, 1.5 and 2.0 Wt.%, were prepared using the flux doping technique. X-ray diffraction (XRD) is used to study the phase composition of the solder alloys, whereas scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are used to investigate the microstructure, fractography and compositions of the solders. Tensile properties such as ultimate tensile strength (UTS), Young’s modulus and elongation are tested using the tensile test, whereas the microhardness value is gained from the micro-Vickers hardness test. The morphology and thickness of the IMC layer at the solder’s joints are investigated by varying the thermally aging duration up to 56 days at 80°C.FindingsXRD analysis shows the presence of Co3Sn2 phase and confirms that Co was successfully incorporated via the flux doping technique. The microstructure of all Sn-58Bi-xCo solders did not differ significantly from Sn-58Bi solders. Sn-58Bi-2.0Co solder exhibited optimum properties among all compositions, with the highest UTS (87.89 ± 2.55 MPa) at 0.01 s−1 strain rate and the lowest IMC layer thickness at the interface after being thermally aged for 56 days (3.84 ± 0.67 µm).Originality/valueThe originality and value of this research lie in its novel exploration of the flux doping technique to introduce minor alloying of Co into Sn-58Bi solder alloys, providing new insights into enhancing the properties and performance of these solders. This new Sn-Bi-Co alloy has the potential to replace lead-containing solder alloy in low-temperature soldering.

Accelerated discovery of lead-free solder alloys with enhanced creep resistance via complementary machine learning strategy

Minor alloying is an effective method to improve the performance of lead-free solder alloys. In this study, we propose a complementary Machine Learning (ML) strategy for minor alloying to design solder alloys with enhanced creep resistance. Two ML models, leveraging compositional and knowledge-aware features, respectively, were constructed to predict the creep stress exponent of Sn–Ag–Cu (SAC)-based solder alloys. Five new solder alloys were designed and experimentally evaluated by screening the virtual sample space consisting of the critical elements, including Bi, In, and Ni, affecting the creep resistance of SAC solder alloys with the ML model. The creep resistance of the designed alloys was characterized using nanoindentation tests. Notably, the creep stress exponent of SAC387-3 wt % Bi-0.4 wt% Ni was determined to be 12.82 at room temperature, indicating a significant 33.9% decrease in creep strain rate compared to the SAC387 alloy. This study demonstrates the potential of the ML approach to design solder alloys with enhanced creep resistance.

Investigation of the Impacts of Solder Alloy Composition and Temperature Profile on Fatigue Life of Ball Grid Array Solder Joints Under Accelerated Thermal Cycling

Abstract This study investigated the thermal fatigue reliability of ball grid array (BGA) solder joints under accelerated thermal cycling, considering the impacts of solder alloy and temperature profile. Applying the Darveaux solder joint reliability assessment, simulations consider lead-based (63Sn37Pb and 62Sn36Pb2Ag) and lead-free (SAC105, SAC305, and SAC405) solder alloys under temperature profiles: 0°C (Tmin) to 100°C (Tmax), −40°C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C. Results indicate that SAC305 exhibited the highest equivalent stress, while 63Sn37Pb demonstrated the highest plastic strain and creep strain energy density. SAC105 displayed the lowest stress and strain parameters. Moreover, increasing the thermal cycling temperature range intensifies stress, strain, and damage parameters, with −40 °C to 150 °C showing the highest magnitudes. SAC405 exhibited superior thermal fatigue life compared to other alloys, with its cycles to failure outperforming 63Sn37Pb, SAC105, 63Sn36Pb2Ag, and SAC305 by 16832, 11992, 6218, and 3601 cycles, respectively. Lower temperature ranges enhance thermal fatigue life, with 0 °C to 100 °C recording 8%, 33%, and 53% higher life than −40 °C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C, respectively. Notably, higher silver content and lower temperature ranges were associated with increased thermal fatigue life, providing valuable insights for BGA solder joint reliability enhancement.

Effect of Bi on the Tensile and Viscoplastic Behavior of Sn-Ag-Cu-Bi Alloys Used for Microelectronics Applications

Sn-Ag-Cu-Bi (SAC-Bi) alloys are gaining popularity as a potential replacement for current lead-free solder alloys in microelectronic packages. In this study, the tensile and viscoplastic behaviors of eight SAC-Bi alloys with 0, 1 wt.%, 2 wt.%, and 3 wt.% Bi content were investigated. The samples of these eight alloys were cast, aged at room temperature, 75 °C and 125 °C, and tensile-tested at rates of 0.1/s, 0.01/s, and 0.001/s in ambient and elevated temperature environments to facilitate the quantification of viscoplasticity using the Anand viscoplastic model. The Anand parameters of all eight alloys in the as-cast and aged conditions were determined. Tensile strength was found to increase with the addition of Bi. Additionally, alloys containing 2 and 3 wt.% Bi showed a 5 to 10% increase in tensile strength after isothermal aging of 90 days at 125 °C. On the contrary, the tensile strength of alloys with up to 1 wt.% Bi decreased by 22 to 48% after such aging. Using a Scanning Electron Microscope (SEM) and energy dispersive spectroscopy (EDS), the microstructure of the alloys was characterized. The aging-induced property changes in the samples were correlated to strengthening by Bi solute atoms for alloys with 1 wt.% Bi and the formation of Bi precipitation for alloys with 2 wt.% and 3 wt.% Bi.

Simulation and Prediction of Creep Rate, Activation Energy, and Rupture Time of Sn94Sb5Ag1 Lead-Free Solder Alloy Using Artificial Neural Network Modeling

Simulation and Prediction of Creep Rate, Activation Energy, and Rupture Time of Sn94Sb5Ag1 Lead-Free Solder Alloy Using Artificial Neural Network Modeling

Effect of temperature on joint quality in wave soldering of Sn-9Zn-2.5Bi-1.5In lead-free solder alloy

SnZn (tin‑zinc) solder has been regarded as a promising lead-free solder material with a low melting point of 198 °C, serving as a suitable alternative to both SnPb solder due to its lack of hazardous substances and Sn-Ag-Cu solder because of the high cost associated with silver. Nonetheless, its susceptibility to oxidation hinders solderability and increases soldering defects such as bridging, insufficient fillings, and voids, limiting its use in commercial production. Devices designed with through-hole technology, in contrast to surface-mounted ones, continue to exhibit superior interconnection reliability in such applications. In this investigation on wave soldering, a newly developed lead-free solder, composed of 87% tin, 9% zinc, 2.5% bismuth, and 1.5% indium by weight, was employed under two conditions related to nitrogen content: 1) Ensuring that static oxygen content remained below 3000 ppm. 2) Maintaining soldering section oxygen content below 600 ppm at a conveyor speed of 1200 mm/min. The soldering results were examined at various temperatures of preheating and soldering. It proves that the measured peak temperature of liquid solder TpL over 230 °C makes the bridging defect rate lower than 0.30%. Additionally, setting the peak temperature of solder joint TpZ above 220 °C, along with specific preheating temperatures (105/115/135/145 °C), archives 100% vertical filling without significant voids in the solder joints. Moreover, optimizing wave soldering settings, specifically adjusting the wave soldering setting temperature Ts to 235 °C, conveyor speed vc to 1000 mm/min, resolves soldering defects associated with Sn-9Zn-2.5Bi-1.5In alloy in wave process. Relevance summary1.TpL surpasses 230 °C, the total number of bridging defects per board decreases to fewer than 6, approximately 0.30%. TpZ values of 220 °C or higher results in 100% vertical fill and no significant large voids, demonstrating optimal filling effects2.Under the conditions of TS = 235 °C and vc = 1000 mm/min yield TpL > 230 °C and TpZ > 210.9 °C, it leads to a reduction in bridging defects.3.To maintain flux efficiency and minimize internal voids, an optimal selection of preheating temperatures (105/115/135/145 °C) is demonstrated.4.An integrated nitrogen content-controlled system is utilized to eliminate oxygen from the solder pot, aiming to prevent oxidation.

Investigating the electromigration resistance of composite lead-free solder alloy containing cobalt particles

Investigating the electromigration resistance of composite lead-free solder alloy containing cobalt particles

Solder joint reliability performance study and shear characterization of low-Ag SAC lead-free solders for handheld application

As handheld electronic products move toward smaller and thinner form factor, the demand of high reliability under stringent field usage also increasing. Drop test, based on the JEDEC JESD22-B111A, accompanied with temperature cycling (TC) test, based on JEDEC JESD22-A104F, are two of the most critical board-level reliability tests for handheld makers. In terms of solder joint reliability (SJR), total 7 candidates of LF35-liked lead-free solder alloys are investigated for its drop performance, and TC reliability evaluation. Among 7 solders, leg 4 and 5 exhibit both decent drop and TC behavior, which are likely owing to the silver (Ag) precipitation hardening and bismuth (Bi) solid solution hardening effect respectively. In addition, the shearing mechanical characterization of 7 solder alloys are being studied. Shear strength of leg 4 and 5 shows higher strength value than others. In terms of failure analysis under drop test, three main fracture modes are observed, including via cracking at PCB side, solder/intermetallic compound (IMC) cracking at package side, and Cu trace broken at package side. Furthermore, in terms of failure modes of TC test, solder/IMC cracking at package side are the main fracture modes. In summary, this study provides an overall reliability performance mapping for 7 solders, and list out a table comprising of shear strength, void% analysis, TC reliability, and drop reliability performance for each LF35 solders which lays out potential future solder alloy to meet higher handheld phone drop reliability margin.

Microstructural Examination and Thermodynamic Analysis of Sn-1.5Ag-0.5Cu-x mass% Ni Lead-Free Solder Alloys

The diminutive additions of nickel (Ni) element have been fused to Sn-1.5Ag-0.5 mass% Cu (SAC155) lead-free solder alloy. The study was examined experimentally and computationally (using JMatPro software program) the microstructural features, thermal behavior, density, thermal diffusivity, and conductivity as well as tensile stress strain of the Sn-1.5Ag-0.5Cu-x mass %Ni (x = 0.00, 0.05, 0.10, 0.20, and 0.50) solder alloys (SAC155-xNi). The fusing additions of Ni have a little impact on the melting point of SAC155 alloy which increasing from 502 to 504.2K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$504.2 K$$\\end{document}. The microstructure of SAC155 solder alloy included coarse grains of β-Sn besides, large eutectic regions, and embedded IMCs of Ag3Sn and Cu6Sn5. The computed values of Gibbs free energy (G) during solidification of the β-Sn phase, Ag3Sn, and Sn3Sn4 IMCs show the stability at -130.7×103J.kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$- 130.7 \ imes 10^{3} {\ ext{J}}{\ ext{.kg}}^{ - 1}$$\\end{document}, -157.7×103J.kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$- 157.7 \ imes 10^{3} {\ ext{J}}{\ ext{.kg}}^{ - 1}$$\\end{document}, and -377.13×103J.kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$- 377.13 \ imes 10^{3} {\ ext{J}}{\ ext{.kg}}^{ - 1}$$\\end{document}, respectively. The SAC155-xNi alloys involved finer β-Sn grains, large fibrous eutectic regions, (Cu,Ni)6Sn5 and (Cu,Ni)3Sn4 IMCs. The G of Cu6Sn5 decreased from -233.1×103J.kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$- 233.1 \ imes 10^{3} {\ ext{J}}{\ ext{.kg}}^{ - 1}$$\\end{document} to -317.9×103J.kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$- 317.9 \ imes 10^{3} {\ ext{ J}}{\ ext{.kg}}^{ - 1}$$\\end{document} when Ni content increased up to 0.25 mass %, then stable and steady at -318.4×103J.kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$- 318.4 \ imes 10^{3} {\ ext{J}}{\ ext{.kg}}^{ - 1}$$\\end{document} with more addition of Ni element. The formation of the (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4 IMCs is motivated by the lowest Gibbs free energy, especially when Ni mass% is added to a sufficient level. The measured and computed values of specific heat at constant pressure (Cp) of SAC155-xNi alloys show a good matching especially at lower temperatures and a little mismatch at high temperatures which decreases with increasing Ni content. The activation energy of atomic arrangement (Q) increased from 11.36 to 13.41kJ.mole-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$13.41 {\ ext{kJ}}{\ ext{.mole}}^{ - 1}$$\\end{document} with increasing Ni content in SAC155-xNi alloys. Thermal diffusivity (α) and conductivity (κ) of SAC155-xNi gradually decreased with increasing temperature in the range from 303 to 423 K and/or Ni content in alloys. The measured values of (κ) are slightly lower than the computed value at similar temperatures of the SAC155-xNi alloys. The decrease in (κ) may be assigned to scattering the electrons or reducing the phonon contributions due to the presence of various solute atoms and different IMCs. The results of stress-strain graphs reveal the enhancement of YS and UTS for all Ni-containing alloys. The improvement of the yield stress (YS) and ultimate tensile strength (UTS) of Ni-containing alloys is attributed to the uniform distribution of the IMCs, the reduction of β-Sn grain size, and the smoothed enlargement of the eutectic region.

Synthesis and Characterization of Zn-xFe high Temperature Solder Alloy

This study aims to develop a lead-free high-temperature solder alloy using Zn and Fe, investigating how varying Fe content impacts microstructure, melting behaviour, and properties. Alloys of Zn-xFe (x = 0, 0.005, 0.01) were fabricated via melting and casting. Increasing Fe content reduced hardness and electrical conductivity, with significant microstructural changes observed. Compared to a Zn-xMo study, our results outperformed in mechanical characteristics. Zn-0.01 Fe emerged as the optimal composition, exhibiting the highest melting temperature (425.81°C), ultimate tensile strength (41.88 MPa), while displaying lower hardness and conductivity. Its microstructure boasted smaller grain boundaries, contributing to superior mechanical properties.

EBSD characterization of graphene nano sheet reinforced Sn–Ag solder alloy composites

This research explores the effects of incorporating Graphene Nano Sheets (GNS) on the microstructural characteristics and mechanical behavior of Sn–Ag solder alloys. The research was driven by the need for environmentally friendly, lead-free solder alloys with enhanced mechanical and thermal properties. The methodology involved incorporating graphene into the Sn–Ag alloy through stir casting, followed by a series of surface preparation techniques. The composite samples were then examined using EBSD to analyze crystallographic orientations and SEM/EDS for surface morphology and elemental composition. XRD provided insights into phase transformations and structural changes. Key findings reveal that the addition of GNS significantly refines the grain structure of the Sn–Ag alloy, leading to a bimodal grain size distribution. This refinement is attributed to the role of GNS as a nucleation site during solidification. Moreover, the study demonstrates a pronounced alteration in the texture of the material, with an increase in low-angle grain boundaries post-GNS addition. This texture change is indicative of enhanced mechanical properties. The results also show a shift in the orientation distribution function (ODF), suggesting a stronger crystallographic orientation due to GNS. These findings suggest that GNS incorporation could lead to improved mechanical and thermal properties in Sn–Ag solder, making them suitable for high-performance electronic applications. The study concludes that GNS not only serves as an effective reinforcement in Sn–Ag solder alloys but also significantly alters their microstructural and textural characteristics, contributing to the alloy's potential application in environmentally conscious electronic manufacturing.

Correlation of microstructure with thermal and tensile creep properties of novel Sn-5Sb-0.5Cu alloy reinforced with Co particles for soldering applications

The present research examined how cobalt microalloying additions of 0.25, 0.5, 0.75, and 1 weight percent affected the microstructural properties, thermal features, and tensile creep characteristics of eutectic Sn-5 wt% Sb- 0.5 wt% Cu (SSC) lead-free solder alloy. According to the results, cobalt additions of 0.25, 0.5, and 0.75 wt% did not affect SbSn phase but significantly refined β-Sn grains, facilitating the formation of fine fibers (Cu,Co)6Sn5 together with plate-like CoSn3 phases, and preventing the formation of Cu6Sn5 phases. Furthermore, a large amount of cobalt (1 wt%) addition accumulated in the coarsening of the CoSn3 phase. Additions of 0.25 wt% Co, 0.75 wt% Co, and 1 wt% Co did not affect the melting temperatures, but pasty ranges had been slightly lowered, which may enhance the thermal characteristics. Addition of 0.5 wt% Co had unfavorable effects on both melting point and pasty range. This has significant effects on solder reliability and electronic service performance. In terms of creep behavior, the SSC-0.75 wt% Co specimens displayed the highest creep resistance because of the fine dispersion of intermetallic compounds (IMCs) and extended the creep-rupture life to a level that is 3.0 times greater than the SSC baseline. Lower creep resistance was observed in SSC-0.25 wt% Co specimens, which was mostly due to the smaller volume fraction of the precipitate phases and the absence of the CoSn3 phase. Depending on the determined stress exponents and activation energies, it is suggested that the dominant deformation mechanism in SSC-xCo solders is the dislocation climb controlled by short-circuit pipe diffusion across the whole temperature range that was examined.

Mechanical Properties of Doped Solder SAC-Q for High Strain Rate Testing at Extreme Surrounding Temperatures for 6 Months of Isothermal Aging

Abstract In various industries, including automobile industry, oil and gas, aerospace, and medical technology, electronic components are subjected to significant strain during shocks, vibrations, and drop conditions. Electronic components of this type are frequently subjected to extreme temperatures ranging from –65 °C to 200 °C. These electronic equipment are frequently subjected to strain rates of 1 to 100 sec−1 in sensitive conditions. SAC-Q, SAC-R, Innolot, and other doped SAC solder alloys have recently been introduced to electronic components and packages. SAC-Q refers to the addition of Bi to the Sn-Ag-Cu composition. The mechanical characteristic results and statistics for lead-free solder alloys are particularly important for increasing electronic package stability and high-temperature storage and strain rates. Furthermore, the mechanical characteristics of solder alloys can be dramatically altered owing to thermal aging, which causes microstructure alteration. For high-temperature aging for longer durations and testing at extremely low to very high working temperatures, SAC-Q solder alloy data is not available. The SAC-Q solder material was tested and studied at working temperatures ranging from −65 °C to 200 °C, with strain rates of up to 75 sec−1, for this study. A comparison was also done with the SAC305 solder, which had been thermally aged and tested under identical conditions. Isothermal aging specimens were kept at 100 °C for up to 180 days following manufacturing and reflowing when tensile studies were conducted at various operating temperatures. This study develops and describes stress–strain curves for a wide variety of strain rates and test temperatures. In addition, the test results and data collected were matched to the Anand viscoplasticity model, and Anand constants were calculated by estimating high strain rate behavior throughout a wide range of operating temperatures and stress levels. In addition, for BGA package assembly with PCB, FE analysis was performed for drop/shock events. For varied aging circumstances of SAC-Q solder ball joints, hysteresis stress–strain curves and plastic work density curves are generated.

The Influence of Reflowing Process on Electrodeposited Sn-Cu-Ni Lead-Free Solder Alloy.

Sn-Cu-Ni lead-free solder alloy electrodeposited on copper substrate from a deep eutectic solvent (DES)-based electrolyte under direct current (DC) and pulsed current (PC) was subjected to a reflowing process at the industrial company MIBATRON S.R.L. (Otopeni, Romania). The alteration of the alloy's composition and anti-corrosive properties upon exposure to the reflow process were investigated via Scanning Electron Microscopy (SEM-EDX), X-ray diffraction (XRD), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Corrosion studies conducted in sodium chloride solution revealed that the system obtained under the DC plating mode (Sn-Cu-Ni-DC) exhibited enhanced anti-corrosive properties compared to the system obtained under PC (Sn-Cu-Ni-PC) after reflowing. However, prior to reflowing, the opposite effect was observed, with Sn-Cu-Ni-PC showing improved anti-corrosive properties. These changes in anti-corrosive behavior were attributed to the modification of the alloy's composition during the reflowing process.

Effect of alloying elements on microstructural and electrical property in Sn–Cu–Bi lead-free solder alloys

Sn–0.7Cu eutectic alloy is a low-cost alloy with moderate melting point and wetting that appears to be adequate for some applications. Lead-free Sn–0.7Cu joint solders on copper substrate were investigated in this study. To enhance the performance of the alloy, many previous studies verified the importance of adding bismuth to the eutectic alloy. (84.3Sn–0.7Cu–15Bi) ternary alloy is regarded as a potential substitute for hazardous Sn–Pb solders, possessing a melting point of 206 °C. The effects of incorporating selenium, zinc, or indium on the electrical characteristics, crystal structure and microstructure of the tin copper-bismuth alloy were examined. Phase identification of the base solder and various newly developed alloys was performed by X-ray diffraction tests and an LCR meter was used to measure the electrical resistance of the prepared samples. The unit cell volume, and lattice parameters of the tetragonal Sn base were altered, along with the electrical characteristics of the base solder alloy. According to the test results, the best addition was by indium since it reduced the grain size of the base solder alloy. Smaller grain size improves the mechanical properties of the solder. Furthermore, indium addition increased the electrical conductivity of the base solder alloy compared to other alloying additions.

Electrical Resistivity of Lead-Free Solders Reinforced by Carbon Nanospheres

Electrical resistivity of the nanocomposites Sn96.5Ag3Cu0.5 and Sn95,5Ag3,8Cu0,7 lead-free solder alloys with minor admixtures of carbon nanospheres (0.05 wt%) was measured in a wide temperature range, including a melting-solidification region. Influence of the carbon nanospheres content on electrical resistivity values has been analyzed. Carbon nanospheres were obtained by electrical discharge method from diesel fuel, cyclohexane, and aviation kerosene. The matrix samples were produced by planar flow casting technique in the form of thin ribbons. Electrical resistivity measurements were performed using four-probe method. Hysteresis between the heating and cooling electrical resistivity curves relates to the non-equilibrium solidification.