Sn Ag Research Articles

A synchronous improvement of strength and elongation caused by solid solution in low-silver SAC solder with superior necking resistance properties

The current SAC(Sn–Ag–Cu) solder often experiences rapid degradation of mechanical properties at high temperatures and is prone to fracture under dynamic loads, thus failing to meet the interconnection requirements of industrial electronic products that operate under high power and vibration loads. In light of this, this paper aims to enhance the overall performance of the alloy by reducing the fraction of the second phase in SAC305 alloy, altering the type of second-phase particles, and strengthening the matrix β-Sn phase. Additionally, based on thermodynamic calculations of phase diagrams, the internal phases and elemental solid solubility of the alloy under different temperature conditions are accurately designed, thereby improving the alloy's strength while maintaining its elongation almost unchanged. The experimental results indicate that the designed Sn1.0Ag0.7Cu–3Bi4In1.5Sb alloy exhibits a higher rate sensitivity factor m (0.0559), which is more than double that of the Sn1.0Ag0.7Cu–5Bi4In3Sb alloy (0.0239). This improvement is primarily attributed to the enhanced interaction between the matrix β-Sn and the solid solution effect. Larger compound phases, such as Cu6Sn5 and Ag3Sn, only play a role in the low-rate loading region. Additionally, the alloy demonstrates strong temperature dependence, which is also related to the dissolution of the In element in the matrix β-Sn. The solid solution of the In element significantly enhances the high-temperature elongation rate of the alloy, increasing from 11.9% at low temperatures to 21.3% at high temperatures. The successful development and implementation of this research provides a new solution for interconnection of electronic devices under high-speed dynamic loading and high-temperature service.

Comments on: “Low temperature engineering feasibility of high reflective Ag–Sn films from experimental and thermodynamic views” [Mater. Phys. Chem. 254 (2020) 123490]

In this communication, some aspects of a paper published recently by Gao et al. Mater. Phys. Chem. 254 (2020) 123490 (here Gao et al. (2020) [4] are discussed. In this paper, some erroneous interpretation and citation of previously published work and false considerations concerning the phase formation in Ag–Sn thin layers are outlined.

Eutectic Solidification Morphologies in Rapidly Solidified Hypereutectic Sn–Ag Solder Alloy

The effect of rapid solidification upon hypereutectic Sn–Ag solder alloy has been investigated using a 6.5 m drop tube. Powder sizes ranging from > 850 to < 38 μm were produced, with equivalent cooling rates of 250 to 14,800 K s−1 for 850 and 38 μm droplets, respectively. At all cooling rates investigated, dendritic β-Sn was observed as the primary solidification phase, not proeutectic Ag3Sn as predicted by the phase diagram. The volume fraction of interdendritic eutectic was observed to decrease with increasing cooling rate, with the Ag concentration in the residual interdendritic liquid estimated at 12.5–15 wt pct Ag, far in excess of the eutectic concentration of 3.8 wt pct. Much of the Ag3Sn observed within the eutectic had a blocky, divorced eutectic appearance. A model is proposed which can explain these observations in terms of sluggish nucleation of the Ag3Sn intermetallic, coupled with a metastable phase diagram that permits significant supersaturation of Ag at modest undercooling.

Effect of Ni-RGO nanosheets on the creep behavior of Sn–Ag–Cu composite solder joints

Creep damage of Sn–Ag–Cu micro-joints is inevitable in service, even at room temperature. In this study, Ni-decorated reduced graphene oxide (Ni-RGO) nanosheets were rationally selected as a promising reinforcement in Sn-3.0Ag-0.5Cu (SAC305) solder to improve creep resistance. Tensile creep tests were conducted on the Ni-RGO reinforced SAC305 micro-joints under 8–14 MPa stress at 100–150 °C by dynamic mechanical analysis (DMA) equipment. Micrography and fractography were observed using FESEM. The stress exponent (n) increased from 5.83 to 6.37, and the activation energy (Q) rose from 68.80 to 75.41 kJ/mol as 0.10 wt% Ni-RGO nanosheets were added into the SAC305 solder, indicating the occurrence of diffusion mechanism. By adding a trace amount of Ni-RGO nanosheets (no more than 0.10 wt%), the crack initiation was prone to occur at the wave-valley of the continuous scallop shaped interface, where the diffusion of vacancies occurred, resulting in hybrid-fracture features of quasi-cleavage and dimples. It can be concluded that the inclusion of trace amounts of Ni-RGO nanosheets can enhance the creep resistance of SAC305 micro-joints during service.

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

Synthesis and structural characteristics of AgxSn1–xO2 nanocomposites and their sensing performance toward methane, hydrogen, and carbon monoxide

The physical features and potential applications of metal oxide semiconductor nanomaterials can be influenced by doping, heat treatment, and applied synthesis techniques. Herein, a simple hydrothermal method was used to synthesize AgxSn1–xO2 nanocomposites (x=0, 0.05, 0.2, 0.4, 0.5, and 1). The crystal structure, surface morphology, chemical bonding, surface area, and oxidation states are investigated. FTIR, XRD, HR-TEM, SEM, and XPS techniques were used to characterize the AgxSn1–xO2 nanocomposites, while the electrical resistivity measurement was conducted to assess their gas-sensing characteristics. The findings demonstrate that Ag atoms are evenly distributed inside the tetragonal SnO2 lattice up to x=0.4, meanwhile, a further increase in x leads to the growth of a cubic Ag2O phase alongside the SnO2 phase. The crystallite size of the SnO2 phase was increased as the Ag concentration increased, whereas reduced for the Ag2O phase. The pure SnO2 phase exhibits spherical nanoparticles, whereas the AgxSn1–xO2 nanocomposites (x > 0) have a morphology of nanosheets and nanoplates. The average BET surface area was improved to 358 m2/g by increasing the Ag content up to x=0.2. The XPS confirms the presence of various oxides such as Sn 3d, O 1 s, and Ag 3d. The AgxSn1–xO2 nanocomposites were employed as electrical sensors to detect CH4, H2, and CO gases at an operating temperature range of 200–400 °C. The Ag0.2Sn0.8O2 nanocomposites show the best response/recovery time towards CH4 at 200 °C. The AgxSn1–xO2 composite exhibits a good response towards CH4 compared to H2, and CO gases.

Combined effect of Ag element and temperature gradient on the formation of highly orientated Sn grains in micro solder joints

Sn–Ag solders are widely used for advanced electronic packaging. The combined effect of Ag element and temperature gradient (TG) on the formation of Sn grains in Cu/Sn-xAg/Cu micro solder joints was elucidated systematically. Numerous small-sized β-Sn grains were formed in both Cu/Sn/Cu and Cu/Sn-0.5Ag/Cu micro solder joints after reflow with or without TG. The Cu/Sn-0.5Ag/Cu joint was found to have more twinning β-Sn structures. The formation of the multiple β-Sn grains in these two joints was attributed to the presence of multiple tetrahedral metastable short-range order (SRO) structures which acted as nuclei for the nucleation and growth of β-Sn. The existence of TG slightly enhanced the preferred orientation characteristics of Sn grains. For the joints with Ag content was or higher than 2 wt%, several Sn grains were formed without TG, while a single or highly oriented Sn grains were observed with TG. The number and orientation of Sn grains were affected by the combined effect of Ag element and TG significantly. The β-Sn grains formed without TG were based on the {101} type cyclic twinning configuration clusters that stabilized by Ag atoms and acted as nuclei. The formation of a single or highly preferred β-Sn grains was benefit from the combined effect of Ag element and TG. The results provide theoretical guidance for optimizing the composition of Sn–Ag solders and controlling the microstructure of the joints, thereby contributing to the advancement of electronic packaging technologies.

Interfacial wetting and reacting between pyrolytic graphite and Sn–Ag–Cu–Al alloy under ultrasonication at a low temperature

Poor wetting and bonding serve as significant challenges in the joining of carbon materials at low temperatures. In this work, the ultrasonically assisted hot dipping of pyrolytic graphite was investigated in a SnAgCu–2Al liquid metal at a low temperature of 250 °C in air. During the ultrasonic-assisted hot-dipping process, the filler metal filled into the surface grooves of pyrolytic graphite. A closely contacting interface formed between the pyrolytic graphite and the filler metal. Interlayer penetration induced by the cavitation effect, and the amount and depth of penetration increased with ultrasonication time. A transition layer of Al2O3 was formed at the interface between pyrolytic graphite and the filler metal. Large amounts of O atoms were induced at the interface during the ultrasonically assisted hot-dipping process, and the reaction of Al and O preferentially occurred between the liquid metal and solid C. This was consistent with the thermodynamic calculation results. The joining of metallizing-pyrolytic graphite was achieved by soldering at same temperature of 250 °C in air, where the highest joint strength could reach 17.52 MPa, achieving a joining module with a high thermal conductivity of 392 W/(m·K) and reaching 90 % of the base material.

Measurement of Diffusion Coefficients and Assessment of Atomic Mobilities in HCP Mg-Ag-Sn Alloys

Reliable thermodynamic and kinetic databases are essential for designing and developing novel magnesium (Mg) alloys for elevated-temperature applications in the automotive and aerospace industries. This study investigated diffusion behaviors of HCP Mg-Ag-Sn alloys by four sets of three diffusion couples annealed at 450, 500, and 550 °C, respectively. Interdiffusion and impurity diffusion coefficients at the three annealing temperatures were extracted using the forward-simulation method. The determined diffusion coefficients, combined with prior results in the literature, were then used to assess atomic mobilities for the HCP phase of the Mg-Ag-Sn system. This assessment was conducted using the DICTRA and the TCMG5 thermodynamic database within the Thermo-Calc software. Comprehensive comparisons between calculated and experimental diffusion coefficients yielded an excellent agreement. The atomic mobilities were also further validated by appropriate predictions of concentration profiles and diffusion paths observed in independent diffusion couple experiments performed at 525 °C for 18 hrs. It has been found that the addition of Sn and Ag both increase the diffusivity of Ag in HCP Mg and Sn in HCP Mg in the stable temperature range of HCP Mg, respectively. This improved understanding of the kinetics in the Mg-Ag-Sn ternary system is essential for controlling diffusion-dependent properties such as coarsening and, therefore, the mechanical properties of Mg-Ag-Sn alloys at elevated temperatures.

Microstructural Evolution and Phase Transformation on Sn–Ag Solder Alloys under High‐Temperature Conditions Focusing on Ag3Sn Phase

This study investigates the microstructural and phase transformations in Sn–Ag solder alloys under high‐temperature conditions, utilizing X‐ray diffraction, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses. Analytical techniques are employed pre‐ and postcontrolled thermal cycling from 30 to 180 °C, aimed at emulating solder reflow processes. The analysis at room temperature demonstrates pronounced crystalline peaks, suggesting a preferred orientation within the crystal structure. Upon heating, peak broadening suggests grain growth and the onset of recrystallization. SEM and energy‐dispersive spectroscopy analyses corroborate these findings, displaying a fine‐grained, well‐distributed microstructure with a homogenous composition of Sn and Ag elements. EBSD provides insights into the orientation and texture of grains, revealing a weak‐to‐moderate texture across the phases. Postexperiment data indicate a dominant presence of larger grains and significant variation in grain size, with an area‐weighted mean grain size of 68.47 μm and a standard deviation of 8.68 μm; this suggests significant grain growth and coarsening of the Ag3Sn intermetallic compounds. These structural evolutions have crucial implications for the mechanical properties and reliability of the solder alloy in electronic assemblies, underscoring the need for further exploration of lead‐free solder materials in the electronics industry.

Influence of bismuth addition on the physical and mechanical properties of low silver/lead-free Sn-Ag-Cu solder

The Sn–Ag–Cu (SAC) solders with low Ag content have been identified as promising candidates to replace the traditional Sn–Pb solder for flip-chip interconnects. This study examines the impact of incorporating Bi element on the microstructure, thermal behavior, and mechanical performance of low-silver-content Sn-1.5Ag-0.7Cu (SAC157) solder alloy. Besides using the conventional cross-sectioned microstructure image, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and tensile stress- strain techniques were used to investigate the microstructure, thermal and mechanical properties after the addition of Bi, respectively. The results demonstrate that adding of Bi could refine the microstructure, optimize the thermal properties, and improve the tensile strength. Meanwhile, the ductility of the solder alloys reduced evidently in comparison to the Sn-1.5Ag-0.7Cu solder. From the microstructural analysis, 0.5 wt % Bi addition to SAC157 significantly enhanced the solid solution effect of Bi and refined β-Sn dendrite, as well as extended the eutectic area. Moreover, as the Bi addition increases to 5 wt %, finely dispersed bismuth precipitates within the β-Sn matrix, along with an enlarged eutectic area, lead to a remarkable enhancement in both ultimate tensile strength and yield strength. The electrical resistivity was characterized by the four-point probe technique. The results show that the electrical resistivity of Bi-modified SAC157 solder alloy decrease from 13.9 to 9.8 μΩ cm with the addition of 5 wt % Bi. These improvements can be attributed to the solid-solution and precipitation strengthening effects induced by the presence of bismuth. The results confirmed that the developed material is applicable as a potential high strength solder material in the context of advanced interconnecting applications.

Reactive diffusion at the interface between Cu and Sn–Ag alloys

This study investigates the microstructural evolution and growth behavior of intermetallic compound (IMC) layers in the Cu/(Sn-yAg, y = 0.29–2.00 wt%) system during isothermal aging within the temperature range of 433–473 K. Through systematic variations in Ag content, aging temperature, and time, the fundamental mechanisms governing IMC formation and growth in Cu/(Sn–Ag) solder joints are elucidated. The results demonstrate that IMC growth kinetics follow a power-law relationship, with IMC layer thickness increasing systematically with annealing time. The addition of Ag significantly influences IMC nucleation and growth, with higher Ag content correlating with faster growth rates. Furthermore, the temperature dependence of IMC growth rates is investigated, revealing higher temperatures leading to increased growth rates, indicative of boundary diffusion-controlled growth. By calculating activation enthalpies, values of 36.4 kJ/mol for Sn-2.00Ag and 30.2 kJ/mol for Sn-0.50Ag were obtained, providing quantitative insights into the faster growth rate of intermetallic compound thickness in the Cu/(Sn-2.00Ag) diffusion couple within the experimental temperature range. These findings offer valuable insights into factors affecting the reliability and performance of solder joints in electronic packaging applications.

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.

Effects of aging time and temperature on shear properties of Sn–Zn and Sn–Ag–Cu solder joints

Effects of aging time and temperature on shear properties of Sn–Zn and Sn–Ag–Cu solder joints

Synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve tribological properties of M50 bearing steel with microporous channels

Purpose This paper aims to study the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve the tribological properties of M50 bearing steel with microporous channels. Design/methodology/approach M50 matrix self-lubricating composites (MMSC) were designed and prepared by filling Sn–Ag–Cu and MXene–Ti3C2 in the microporous channels of M50 bearing steel. The tribology performance testing of as-prepared samples was executed with a multifunction tribometer. The optimum hole size and lubricant content, as well as self-lubricating mechanism of MMSC, were studied. Findings The tribological properties of MMSC are strongly dependent on the synergistic lubrication effect of MXene–Ti3C2 and Sn–Ag–Cu. When the hole size of microchannel is 1 mm and the content of MXene–Ti3C2 in mixed lubricant is 4 wt.%, MMSC shows the lowest friction coefficient and wear rate. The Sn–Ag–Cu and MXene–Ti3C2 are extruded from the microporous channels and spread to the friction interface, and a relatively complete lubricating film is formed at the friction interface. Meanwhile, the synergistic lubrication of Sn–Ag–Cu and MXene–Ti3C2 can improve the stability of the lubricating film, thus the excellent tribological property of MMSC is obtained. Originality/value The results help in deep understanding of the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 on the tribological properties of M50 bearing steel. This work also provides a useful reference for the tribological design of mechanical components by combining surface texture with solid lubrication. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0381/

Influence of Ti2SnC content on arc erosion resistance in Ag–Ti2SnC composites

Abstract In this work, an Ag–Ti2SnC composite was fabricated by the hot-pressing sintering method, and the erosion behavior of Ag–Ti2SnC with volume percentages of 10–40% was studied at a load voltage of 10 kV. The arc life and breakdown current were observed at about 31–36 ms and 39 A, respectively. The cathode spot traveled the fastest on the surface of the Ag–40 vol% Ti2SnC composite. Due to emission center model, the temperature of the minor protrusions on the cathode surface increased, resulting in Ag ions, Ti ions, and Sn ions being generated. Combining with the ionized oxygen, Ag2O, AgO, TiO2, and SnO2 were formed on the eroded Ag–Ti2SnC surface after arc erosion. The research results will broaden the application range of Ag–Ti2SnC electrical contact material and enrich the arc erosion mechanism.

Influence of carbon nanotubes on the morphology of Cu6Sn5 in Cu/(Sn–Ag–Cu) solder joints

This study delves into the intricate interaction between multi-walled carbon nanotubes (MWCNTs) and the Sn–Ag–Cu solder system, highlighting its relevance in lead-free soldering applications. Reflow and isothermal aging induce the formation of intermetallic layers at the joint interface, including Cu6Sn5, Cu3Sn, and irregularly shaped Ag3Sn particles. The addition of MWCNTs leads to the flattening of Cu6Sn5 grains, restraining their growth and potentially improving mechanical strength. Notably, MWCNTs exhibit a relatively high affinity with Ag3Sn. Grain size distribution analysis indicates that MWCNTs reduce particle size, effectively suppressing intermetallic compound growth. Over time, grain size increases due to simultaneous coarsening and growth during isothermal aging. In the growth kinetics analysis of intermetallic compounds in SAC305-MWCNTs solder joints, stable behavior is observed for Cu3Sn growth, driven by solid-state diffusion between Cu6Sn5 and Cu. In contrast, Cu6Sn5 exhibits significant variations in growth behavior with temperature changes. Furthermore, the evaluation of activation enthalpy for Cu3Sn growth in the Cu/(SAC305-MWCNTs) and Cu/SAC305 diffusion couples reveals similar n and k values of the power function for the layer growth, indicating a comparable rate-controlling process for Cu3Sn growth. The presence of MWCNTs in the solder does not significantly influence the rate-controlling process or activation enthalpy for Cu3Sn growth, contrasting with the observed effects on Cu6Sn5 growth. This study provides valuable insights into the interactions within the SAC305-MWCNTs solder system, offering significant implications for lead-free soldering applications.

Enhancing performance of Sn–Ag–Cu alloy through germanium additions: Investigating microstructure, thermal characteristics, and mechanical properties

The conflict between strength and ductility has been a longstanding dilemma for metallic alloys. In this study, we introduce an innovative approach to significantly improve the overall performance concerning ultimate tensile strength (UTS) and elongation (EL%). This research explores the effects of adding germanium (Ge) into Sn− 2.0Ag− 0.7Cu (SAC207) solder alloys, delving into its impact on microstructure, thermal properties, ductility, and ultimate tensile strength. The findings revealed that adding Ge substantially reduces the eutectic temperature and undercooling within the solder, concurrently refining the β-Sn phase while expanding the eutectic regions. Furthermore, the formation of Ge phases within the solder matrix noticeably influences its mechanical properties. It is notable that introducing 0.5 wt% Ge into SAC 207 alloy leads to exceptional enhancements in both strength and ductility, with a remarkable tensile strength of 56.5 MPa and an elongation of 58.3%. These notable improvements can be attributed to the creation of a heterogeneous microstructure fortified by grain boundary strengthening, solid solution enhancement, and precipitation strengthening effects in solder alloys. The valuable insights gleaned from this research have significant implications for the advancement of the SAC 207 alloy in various applications and optimizing its manufacturing processes.

Effect of Minor Sb Additions on Thermal Properties, Microstructure and Microhardness of Sn–Ag–Cu High-Temperature Solder Alloys

Effect of Minor Sb Additions on Thermal Properties, Microstructure and Microhardness of Sn–Ag–Cu High-Temperature Solder Alloys

Ultrasonic-assisted soldering of Si and Cu joint with SnAgTi solder in air

The reliable connection of single crystal Si and Cu at low temperature is widely utilized and plays a crucial role in the field of electronic packaging. In this study, Sn–Ag–Ti active filler is ultrasonically coated onto the Si surface to facilitate the subsequent ultrasonic soldering process to realize the bonding of Cu to pre-metallized Si. Furthermore, a detailed analysis was conducted on the influence of ultrasonic time on both the bonding mechanism and mechanical properties of the joint. The results revealed that Ti–Sn compound within the solder decomposed with ultrasonic action duration time of 20 s, resulting that Ti elements enriched at the Si/solder interface and reacted with SiO2 to form a mixture comprising TiO2 and SiTi phase. It contributed to higher strength (43.9 MPa) at the Si/solder interface. Additionally, it has been found that microstructure and property at the Cu/solder interface were directly affected by ultrasonic time. Specifically, when subjected to 3 s of ultrasonic action, poor load-bearing capacity exhibited by thin infiltration layers caused fracture at the Cu/solder interface; When the ultrasonic action time is 6 s, the joint strength reaches its maximum value of 41.3 MPa, leading to fracture occurring within the Si material. However, when the ultrasonic holding time is extended to 20 s, the joint strength decreases to 20.3 MPa. This phenomenon arises from impaired plasticity of Cu6Sn5 near the Cu–Sn layer, which is attributed to the presence of attached dendritic Cu6Sn5 phases and shed bulk Cu6Sn5 that are prone to crack initiation. This research presents a promising approach for ceramic/metal heterogeneous joining.