Microstructure Of Sn Research Articles

Investigation on the Recrystallization and Nb3Sn Microstructure of Nb Alloys With Large Deformation During Heat Treatment

Investigation on the Recrystallization and Nb₃Sn Microstructure of Nb Alloys With Large Deformation During Heat Treatment

Effects of Different Zinc Content on Solidification, Microstructure, and Mechanical Properties in Tin–Bismuth Alloy

The present aims to evaluate the effect of adding Zn (0.5% and 9.0% in wt%) on phase transformation temperatures, microstructure coarsening, solidification parameters (cooling rate‐L and growth rate‐VL), macrosegregation, and mechanical properties of directionally solidified Sn‐34wt%Bi‐xZn alloys. The samples have been characterized by optical microscopy, scanning electron microscopy, X‐ray fluorescence, and X‐ray diffraction, in addition to Vickers microhardness and tensile tests. The CALPHAD method has been used for thermodynamic computations via Thermo‐calc software, in order to obtain thermodynamic data. The microstructure of Sn–Bi–Zn alloys is mainly dendritic, composed of a Sn‐rich matrix (β‐Sn) with Bi precipitates inside and surrounded by a Sn+Bi eutectic mixture of phases, predominantly observed at the coarse scale. Coarse Zn needles are also observed in the Sn‐34wt%Bi‐9wt%Zn alloy due to the high Zn content. On the whole, Zn provoked a coarsening of the dendritic arrangement. Moreover, Zn additions cause inverse segregation of Bi, as compared to the rather constant macrosegregation profile observed in the binary Sn–Bi alloy. On the whole, both additions of Zn (0.5 and 9.0) promoted increase in Vickers microhardness, yield strength (σY), and ultimate tensile strength (σu), however, causing an overall reduction in elongation‐to‐fracture (δ).

A viscoplastic approach to the chemomechanical behavior of Sn microstructure

A viscoplastic approach to the chemomechanical behavior of Sn microstructure

Effect of Ag addition on the microstructure and corrosion properties of Sn–9Zn lead-free solder

The effects of Ag addition on the microstructure of Sn–9Zn alloy and its corrosion behaviour in neutral and static 3.5 wt% NaCl solutions were investigated using surface characterization techniques and electrochemical techniques. The results show that in Sn–9Zn-xAg alloys, Ag reacts with Zn to form AgZn3 intermetallic compounds (IMCs), which refined the microstructure of the alloys and changed the corrosion mode of the alloy surfaces from pitting corrosion to surface corrosion. The addition of Ag effectively improved the corrosion passivation film structure and electron transfer characteristics of the alloy, increased the self-corrosion potential (Ecorr) and reduced the self-corrosion current (Icorr), thus improving the corrosion resistance of the alloy. The study explained and verified the corrosion mechanism of the alloy from both experimental and theoretical perspectives. It is concluded that Sn–9Zn-0.4Ag alloy shows relatively the best corrosion resistance.

Effect of Microwave Hybrid Heating on Mechanical Properties and Microstructure of Sn3.0Ag0.5Cu/Cu Solder Joints

Microwave hybrid heating (MHH) has become soldering’s alternative method for lead-free solder alloys due to its benefits towards modern microtechnology, such as shorter processing time, lower energy consumption and lower defect rate. Nonetheless, it still requires susceptors to improve its heating performance, such as SiC, which is known for its high loss factor under low microwave frequencies. In this study, the effect of microwave hybrid heating on mechanical properties, as well as the microstructure of solder joint between Sn3.0Ag0.5Cu (SAC305) solder alloy and Cu substrate was investigated. Solder joint was created using MHH with different soldering parameters (amount of SiC in a range of 3-7g and exposure time in a range of 7-10min) between SAC305 solder alloy (in the form of wire and paste) and Cu substrate. Then, a lap shear test was carried out following a standard of ASTM D1002 to determine solder joint strength. Characterization was made using an optical microscope and scanning electron microscopy. Results showed that solder wire produced the highest solder joint strength with the value of 115.45 MPa when using 3.05g of SiC for 8.92min soldering time. Meanwhile, the solder paste produced 109.76MPa solder joint strength when using 3.03 g of SiC for 9.39 min soldering time. The intermetallic compound (IMC) form was scallop-like Cu6Sn5, both solder/substrate joints with a thickness of 2.87 μm for solder wire and 3.62 μm for solder paste. Nonetheless, an excessive amount of SiC would generate more heat in MHH and increase the IMC thickness as well as reduce shear strength, which eventually decreases the solder joint stability.

Coupled effect of Ag and In addition on the microstructure and mechanical properties of Sn–Bi lead-free solder alloy

The microstructure and mechanical properties of Sn–Bi solder alloys with various Ag and In addition are comparatively investigated. The results illustrate that the tensile strength and ductility of the solder alloy could be dramatically enhanced with negligible loss of the plasticity. Especially, the Sn–Bi solder alloy with 0.4 wt. % Ag and 1.5 wt. % In exhibits the maximum tensile strength and elongation of 79.7 MPa and 45.9%, respectively. The microstructure of the Sn–Bi solder alloys is mainly composed of Bi-rich and β-Sn phases. With the addition of elements Ag and In, the microstructure is significantly refined, and the lamellar eutectic structure with thinner interlayer spacing could be detected. Element Ag tends to form Ag3Sn phase while element In solutes in the Sn matrix. The mechanical properties of the as-prepared Sn–Bi solder alloy are improved attributed to the precipitated-phase strengthening of the fined Ag3Sn phase and the refinement effect of In on coarse Bi-rich phase.

Microstructure evolution at the interface between Cu and eutectic Sn–Bi alloy with the addition of Ag or Ni

The study investigated the growth kinetics and rate-controlling processes of intermetallic layers formed at the interface between Cu and eutectic Sn–Bi alloys with Ag or Ni addition at solid-state temperatures. Isothermal sections of the equilibrium phase diagram were calculated to understand phase stability at the interface. The thicknesses of the intermetallic layers were plotted against annealing time, and a power function equation with an exponent slightly smaller than 0.25 described their relationship, indicating boundary diffusion with grain growth as the predominant control mechanism. The relationship between the exponent and annealing temperature suggested that the grain growth in the intermetallic layer followed an approximate parabolic law. The eutectic microstructure in Sn–57Bi–1Ag and Sn–57Bi–1Ni alloys changed with annealing, with differences in the Bi region width. However, the contact surface area between the Bi region and Cu6Sn5 compound was similar in both alloys. Activation enthalpies for the rate-controlling process of intermetallic layer growth were evaluated, providing insights into the energy barrier for atomic diffusion or transport across the interface.

Crack mechanism correlated with Sn grain orientations on Ni metal surface subjected to 1000 thermal shocks

With the rapid development of 3D packaging, it is of great practical significance to understand the failure mechanism of solder joints in heterogeneous integration devices. In this study, the grain orientation and microstructure evolution of SAC305 solder joints were investigated in thermal shock tests for fan-out wafer level packaging. The heterogenous evolution of microstructure in Sn–3Ag-0.5Cu (SAC305) solder joints was investigated using electron backscattered diffraction (EBSD) and nanoindentation analysis. When the thermal shock reaches 1000 cycles, the local deformation caused the heterolattices in the joint to rotate toward the corners due to the thermal expansion. During deformation, sub-grain formation is accompanied by an increase in dislocations, the accumulation of plastic slip, and the activation of slip systems. The energy stored by this deformation is released in the form of cracks. The work in this paper provides new insights into the early stages of grain orientation, microstructural deformations and the accumulation of stored energy associated with these deformations, providing a scientific basis for the application and failure analysis of large size fan-out welded joints in complex working conditions.

Effects of phosphorus and germanium on oxidation microstructure of Sn–0.7Cu lead-free solders

Effects of phosphorus and germanium on oxidation microstructure of Sn–0.7Cu lead-free solders

CALPHAD-guided optimization of the microstructure of Sn–Sb–Cu bearing alloys

The increasing Cu content of Sn–11Sb-xCu (wt.%, x = 0, 2, 4, 6) bearing alloys promotes the growth of ordered Sn3Sb2, and Sn3Sb2 with the maximum mean diameter (161.3–177.3 μm) is observed in Sn–11Sb–6Cu alloy. Gravity-driven aggregation of Sn3Sb2 occurs in the top region of Sn–11Sb ingot. The inhomogeneous distribution of Sn3Sb2 driven by density difference between Sn3Sb2 and matrix is suppressed with Cu addition due to the formation of Cu6Sn5 with a density of 8.06 g/cm3, and homogeneous microstructure is obtained in Sn–11Sb-xCu alloys (x = 2, 4, 6). Sn3Sb2 changes from regular cube morphology to irregular morphology with Cu content reaching 6 wt%. The relatively high Cu content in liquid leads to the nucleation of Cu6Sn5 around the liquid/Sn3Sb2 interface. Cu6Sn5 inside Sn3Sb2 can thus effectively affect the growth direction of Sn3Sb2, and finally lead to the formation of Sn3Sb2 with irregular morphology. The influence of Cu on microstructure evolution of Sn–Sb–Cu bearing alloys is revealed with the guidance of phase diagram calculation (CALPHAD), which can contribute to the further optimization of Sn–Sb–Cu and other bearing alloy.

Controlled Synthesis of Highly Active Nonstoichiometric Tin Phosphide/Carbon Composites for Electrocatalysis and Electrochemical Energy Storage Applications

Three types of new-structured phosphorized tin microspheres (Sn–P), phosphorized tin microsphere-carbon (Sn–P–C), and phosphorized tin nanoparticles embedded in interconnected porous carbon microspheres (Sn–P@PCMs) were prepared through a carbothermal reduction-assisted phosphorization strategy. The characterization of the formation mechanism and microstructure of Sn–P, Sn–P–C, and Sn–P@PCMs composites demonstrated that the controllable evaporation of coordinated phosphorus in the thermally unstable tin phosphide intermediate by accurate thermal treatment contributed to the formation of a ca. 3 wt % P-doped metallic tin structure featuring a nonstoichiometric SnxPy (y/x = 0.2) core, a Sn-rich phosphorized metallic (y/x = 0.05) shell, and an increased phosphorus concentration from the outer surface to the inner core. The as-prepared phosphorized tin-based composites were applied as counter electrode materials for dye-sensitized solar cells (DSSCs), in which the Sn–P–C counter electrode exhibited the lowest charge transfer resistance of 3.47 Ω and the assembled DSSCs delivered an optimum power conversion efficiency of 8.59%, superior to those of Pt-based cells (6.78 Ω and 7.46%, respectively). The unique bifunctional structure of the SnxPy conductive core coupled with the phosphorized metallic Snδ+ (0 < σ < 0.6) electrocatalytic shell accounts for its excellent electrocatalytic activity and electrical conductivity. In addition, the phosphorized tin-based composites were utilized as potential anodic material for lithium-ion batteries, in which the Sn–P@PCMs electrode showed a specific capacity of 743 mAh g–1 at 0.1C after 400 cycles and 435 mAh g–1 at 5C after 30 cycles. The superior Li-ion storage, cyclability, and rate performance of Sn–P@PCMs could be attributed to the incorporation of Sn–P nanoparticles into interconnected porous carbon microspheres that effectively buffered the large volumetric change and enhanced the electronic–ionic conductivity during the lithiation and delithiation process.

The microstructure, melting properties and wettability of Sn–3.5Ag–0.7Cu–xIn lead-free solder alloys

ABSTRACT In this work, Sn–3.5Ag–0.7Cu-xIn (SAC357-xIn) solder alloys were prepared using a high-frequency induction melting furnace and then treated under air cooling and water quenching, respectively. The evolution of the microstructure of the Sn–3.5Ag–0.7Cu–xIn lead-free solder alloys under the addition of indium and its effects on melting point, hardness and wettability were investigated. The results show that the addition of indium can remarkably affect the microstructures and melting properties of SAC357 alloys. When the content of indium increases from 0 to 5 wt.%, indium is conducive to the formation and growth of Ag3(Sn, In) and Cu6(Sn, In)5. The intermetallic compounds (IMCs) of In4Ag9 are first detected in the microstructure of SAC357-5In alloy. When the content of indium is 20 wt.%, β-Sn phases disappear and In0.2Sn0.8 IMCs become the main phase. With the cooling rate increasing, the phase compositions of as-prepared alloys are almost not changed, but the solidification structures obviously refine. Meanwhile, the melting temperatures of as-prepared alloys decrease and the microhardness values of the alloys increase. SAC357-20In solder alloy prepared by water quenching obtains the lowest melting temperature of 186.2°C and the maximum spreading rate of 2.71 cm2·g−1 at the soldering temperature of 280°C.

Electrical resistivity of Sn–3.0Ag–0.5Cu solder joint with the incorporation of carbon nanotubes

The main objective of this study is to investigate the electrical properties of Sn–3.0Ag–0.5Cu solder joint with the incorporation of carbon nanotube instead of solder bulk. Sn–3.0Ag–0.5Cu solder paste with the incorporation of carbon nanotube up to 0.04 wt% was fabricated by using mechanical mixing method. Fabricated solder pastes were then soldered on printed circuit board via reflow soldering at 260°C peak temperature. Electrical resistivity of Sn–3.0Ag–0.5Cu-carbon nanotube solder joints was measured by the four-point probe method at room temperature. Microstructure properties were observed by optical microscope and field emission scanning electron microscope. Electrical resistivity of Sn–3.0Ag–0.5Cu solder joint was found to increase with the incorporation carbon nanotube up to 0.03 wt% and slightly decrease at 0.04 wt%. Incorporation of carbon nanotube in the solder matrix apparently changes the microstructure of Sn–Ag–Cu solder alloys. Microstructural observation found that electrical resistivity correlated with the distribution area of eutectic phase in the solder matrix due to the existence of carbon nanotube. It was revealed that eutectic phase area increases with the increasing of carbon nanotube wt% up to 0.03 and then slightly decreases at the incorporation of 0.04 wt% carbon nanotube as parallel with the trend of electrical resistivity values.

Tensile deformation and microstructures of Sn–3.0Ag–0.5Cu solder joints: Effect of annealing temperature

The mechanical quality of solder joints plays an important role in determining the structural integrity of electronic interconnects. In this work, we study the annealing effects on the tensile deformation and microstructure of Sn-3.0Ag-0.5Cu (SAC305) solder joints. The annealing temperature is in a range of 75 °C to 230 °C, which covers both liquid and solid states of SAC305 solder material. There are three intermetallic compounds (IMCs) of Ag3Sn, Cu3Sn and Cu6Sn5 formed in the solder joints. The tensile strength of SAC305 solder joints decreases from 27.3 MPa to 18.9 MPa with the increase of the annealing temperature from 210 °C to 230 °C likely due to the decrease of the volume fractions of the IMC particles of Ag3Sn and Cu6Sn5 and the dislocation density. The average sizes of the IMC particles of Ag3Sn and Cu3Sn in the solder joints annealed at a temperature higher than the melting temperature are greater than the corresponding ones in the solder joints annealed at a temperature below the melting temperature.

Comprehensive comparative analysis of microstructure of Sn–Ag–Cu (SAC) solder joints by traditional reflow and thermo-compression bonding (TCB) processes

Thermo-compression bonding (TCB) process has been considered an emerging alternative to the conventional reflow process because of its significantly fast bonding time due to rapid ramping and its ability to fabricate ultra-fine pitch 3D stacked interconnections to achieve package miniaturization, as is necessary in high bandwidth memory (HBM) modules. Since the TCB-process bonded joints are usually followed by additional solder reflow processes for bonding of other components, no attention has been solely dedicated to the reliability of TCB-only bonded joints. In addition, there has not been any fundamental and comparative studies between the conventional reflow bonding and the TCB process. A recent study showed that the TCB joints could be vulnerable to thermal cycling and electro-migration (EM), and therefore risk exhibiting early failures. A significant difference in bonding processes between the two processes may affect solder grain and crystallographic characteristics, thus affecting the reliability performance. Here, we show that the Cu6Sn5 intermetallic compound (IMC) morphology at Sn–Ag–Cu (SAC-305) solder joint interfaces and the β-Sn crystallographic orientation of the solder joint could explain for the premature EM failure in TCB-utilized solder joints. The effect of the IMC layer of TCB-processed solder joints on the diffusion of Cu and Ni atoms at the solder/bond pad interfaces is presented. Furthermore, the thermomigration (TM) caused by Joule heating for TCB-utilized solder joints is discussed. Lastly, statistical studies using electron backscatter diffraction (EBSD) results reveal the higher lattice coherency of β-Sn crystallographic texture for TCB-processed solder joints.

Effect of aging temperature on microstructure and mechanical properties of Sn–9Zn–xZrC solder joints

The effect of aging temperature on microstructure and mechanical properties of Sn–9Zn–xZrC (x = 0, 0.06) solder joints was investigated. The results showed that the wettability of Sn–9Zn based alloys was improved by ZrC nanoparticles, the spreading areas of Sn–9Zn–xZrC (x = 0–0.12) were increased firstly then decreased with increasing ZrC content. The spreading area of Sn–9Zn was about 143.64 mm2 and reached maximum about 190.92 mm2 of Sn–9Zn–0.06ZrC. The microstructure of Sn–9Zn–0.06ZrC solder alloy consisted of β-Sn, Sn–Zn eutectic and intermetallic compounds (IMCs), and the microstructure of Sn–9Zn alloy was refined by adding appropriate amounts of ZrC nanoparticles. The interfacial IMCs at the β-Sn boundary in the Sn–9Zn–0.06ZrC solder joint was Cu5Zn8, and partial Cu5Zn8 was transformed to Cu6Sn5 during aging treatment. The IMCs layer thickness was dominated by aging temperature, and ZrC facilitated the IMCs layer growth. The tensile strength of Sn–9Zn based solder joints was enhanced by adding ZrC particles, and then are decreased simultaneously with increasing aging temperature. The fracture surface of Sn–9Zn joints after aging was mainly composed of uniform dimples, and the fracture mechanism of Sn–9Zn based solder joints was ductile fracture.

Properties and microstructure of Sn–0.7Cu–0.05Ni lead-free solders with rare earth Nd addition

The effects of rare earth Nd on the melting behavior, wettability, microstructure and mechanical properties of Sn–0.7Cu–0.05Ni solders have been investigated in this paper. The melting temperature was found to be slightly influenced with rare earth Nd addition. Results of wetting balance tests showed that adding a proper amount of Nd could substantially improve the wettability of Sn–Cu–Ni solders by decreasing the wetting time and increasing the wetting force. The morphology evolution of solder matrix indicated that Nd contributed to the refinement and uniformity of the microstructure when added within an appropriate range. It was because the fine NdSn3 particles formed primarily in the soldering process would act as heterogeneous nucleation sites during solidification. However, excessive addition of Nd was inadvisable due to the formation of large amounts of brittle and hard NdSn3 compounds with bulk shapes. Meanwhile, moderate amount of rare earth Nd could inhibit the growth of interfacial (Cu,Ni)6Sn5 IMCs during soldering. Results of micro-joints strength test also discovered that Sn–Cu–Ni–Nd soldered joints possessed sounder shear strength, which resulted from the refined microstructure and the improved solders/Cu interfacial morphology. These above results evaluated that the optimum content of Nd added into Sn–0.7Cu–0.05Ni solders was about 0.06 wt%.

Effects of Co addition on shear strength and interfacial microstructure of Sn–Zn–(Co)/Ni joints

Sn–9Zn solder alloyed with cobalt (0, 0.5, 3 wt%) was bonded to Ni pad at 250 °C for various durations, and the effects of Co on the microstructure evolution and the shear behavior of the Sn–Zn/Ni joints were investigated by microstructural observations and shear tests. The results reveal that Co improves the shear strength and the interfacial microstructure of the Sn–9Zn/Ni joints significantly. Co is not only a diffusion barrier that impedes Zn from gathering at the interfaces to form Ni5Zn21, but it reacts with Zn in the composite solders with 3 wt% Co adding to the Sn–9Zn solder. When preferential Ni5Zn21 is transformed into Ni2Sn2Zn at the Sn–Zn–Co/Ni interfaces, ductile ruptures occur as Ni2Sn2Zn has similar elastic modulus and connects firmly with the solder. Accordingly, the strength of the Sn–Zn–Co/Ni joints reaches the highest. Moreover, the shear strength of the Sn–Zn–3Co/Ni joints maintains above 35 MPa after 90 min soldering, on account of the Ni2Sn2Zn remaining uniform ripples and fracture surfaces appearing with homogeneous Ni2Sn2Zn dimples. Whereas, at the Sn–Zn/Ni joints, the thick Ni5Zn21 layer and pores intensify the stress concentration and lead to a lower strength. In general, the addition of Co refines the interfacial microstructure that the Sn–Zn–Co/Ni joints are uniformly stressed and achieve desirable strength.

Microstructure and reliability of Mo nanoparticle reinforced Sn–58Bi-based lead-free solder joints

ABSTRACTThe effect of Mo nanoparticles on the microstructure, wettability and mechanical properties of Sn–58Bi–xMo (x = 0–2.00) solder joints was investigated. The results showed that the optimal wettability of Sn–58Bi–0.25Mo solder was obtained and the microstructure was refined by adding small amounts of Mo. The intermetallic compounds (IMCs) thickness was increased from Sn–58Bi 2.17 µm to Sn–58Bi–2Mo 2.73 µm. The tensile strength of Sn–58Bi solder joint was improved by adding 0.25 wt-% Mo. The fracture mode of Sn–58Bi solder joint and Sn–58Bi–0.25Mo solder joint was brittle fracture and the mixed mode was ductile failure and brittle fracture, respectively. The microstructure of Sn–58Bi and Sn–58Bi–0.25Mo solder joints was coarsened, IMCs thickness was increased and the mechanical properties were deteriorated with increasing aging time.

Effect of deep cryogenic treatment on mechanical properties and microstructure of Sn3.0Ag0.5Cu solder

The effect of deep cryogenic treatment on the performance of steels and alloys has attracted wide attention in the past decades. Deep cryogenic treatment can improve the strength and hardness of steel at room temperature, provide microstructure stability and improve wear or fatigue resistance of material. In the current study, the effect of deep cryogenic treatment on the microstructure and mechanical properties of Sn3.0Ag0.5Cu solders are investigated. The influence to microstructure, tensile strength and ductility improvement are discussed. Experimental analysis shows that the tensile strength of Sn3.0Ag0.5Cu solder increases from 36.76 to 46.27 MPa after 600 h of deep cryogenic treatment at 77 K (− 196 °C), the observed strength-time relation is similar to the Taylor theory for the yield strength and dislocation density. Large particles presented in the fracture of Sn3.0Ag0.5Cu samples are caused by the high cooling rate as well as the concentration difference between the β-Sn and the eutectic system. The precipitated Ag3Sn particles exhibit relatively uniform distribution in deep cryogenic treated Sn-rich matrix, and the size of Ag3Sn particles becomes smaller with longer deep cryogenic treatment time. It is noted that deep cryogenic treatment can increase the internal stress and the dislocation density, higher dislocation density and good ductility lead to movement of the pre-existing dislocations and specific dislocation configurations. Microscopic experiments on solder joints were performed to investigate the microstructure change. The Intermetallic layers were measured which showed negligible change in thickness. A unified creep and plasticity constitutive model is proposed to simulate the stress–strain relationship under deep cryogenic treatment, the predictions show good agreement compared with experimental results.