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:In this study, Ag3Sn nanoparticles were synthesized using the redox method and incorporated into SAC305 solder at varymg mass ratios (0, 0. 1 %,0.15%,0.2%)to investigate their impact on the microstructure, wettabihty, and rehabihty of the solder. The physical phase and morphology of the Ag3Sn nanoparticles were characterized by X-ray diffractometer and scanning e!ectron microscope, whUe the microstructure of the solder jonis was observed using a metallograplic microscope. Subsequently, the solder jonis were aged at 150 C for different durations(0, 50, 100, 150, 200 h), and the interfacaal intermetalic compound (IMC) layer thickness was measured usng Image J software to caiculate the growth coefticienr. Resuits indicate that the addition of an appropriate amount ofAg3Sn nanoparticles to SAC305 solder enhances wettabiiity, refines the microstructure, and inhibits IMC layer growth. As aging progresses, the Cu6Sn5 nntermetanic compound layer transitions from scalloped to pknar, accompaned by the appearance of the Cu3Sn nntermetanic compound aye. The optimal performance was observed with the addition of 0. 15 w. % Ag3Sn nanopartides to SAC305 solder, r esulting n improved wettabiity(spreading area of 167. 447 mm2), minimal growth coefficient(0. 04), and enhanced microstructural refinement [ABSTRACT FROM AUTHOR]

In this study, the interfacial structure and abnormal long-term increase of tensile strength in the interfacial intermetallic compounds (IMCs) between SnAg3Cu0.5 solder and Cu substrates during isothermal aging were investigated. After reflow soldering, the IMC layer at the interface was thin and scallop-type. The interfacial layer became thicker with the increase in aging time. After 200 h of aging at 150 °C, the thickness of the interface gradually increased to 3.93 μm and the interface became smooth. Compared with the unaged Cu-Sn interface, the aged joint interface contained more Cu3Sn. The top of the IMC being reflown was relatively smooth, but became denser and prismatic in shape after 200 h of aging at 150 °C. The tensile strength of the joint, immediately after the reflow, reached 81.93 MPa. The tensile properties of the solder joints weakened and then strengthened as they aged. After 200 h of aging at 150 °C, the tensile strength was 83.86 MPa, which exceeded that of the unaged solder joint interface, because the fracture mode of the solder joints changed during aging. [ABSTRACT FROM AUTHOR]

In this study, Bi, Sb, and Ni were incorporated into Sn3.0Ag0.5Cu (SAC305) solder to enhance its properties. The composite solders SAC305- x Bi-2.0Sb-0.1Ni (x = 2.5, 3.0, 3.5 wt%) were systematically investigated for their microstructure, thermal characteristics, wettability, thermal aging behavior, intermetallic compound (IMC) formation at interfaces, and mechanical properties of solder joints. The results demonstrated that the combined addition of Bi, Sb, and Ni effectively suppressed IMC growth within the solder matrix, leading to microstructure refinement. Increasing Bi content expanded the spreading area, thereby enhancing wettability. During thermal aging, the growth rate of solder joint interfaces decreased as the Bi content increased up to 3.5 wt%. Electron backscatter diffraction (EBSD) analysis indicated that these alloying elements reduce slip and deformation in the Sn matrix of SAC305-3.5Bi-2.0Sb-0.1Ni solder. Moreover, the tensile strength of solder joints consistently increased with the incorporation of these elements. • Adding Bi, Sb, and Ni to SAC305 solder refines microstructure and improves overall properties, including wettability and thermal properties. • Increased Bi content in the solder alloy enhances spreading area and wettability, while broadening the melting range and reducing subcooling. • Higher Bi content decreases the growth coefficient of the solder joint interface during heat aging, forming a "Bi barrier layer. • The alloying elements increase the tensile strength of solder joints, with improved resistance to slip and deformation, transitioning to a mixed fracture mechanism. [ABSTRACT FROM AUTHOR]

The majority of studies on high-reliability solder alloys have focused on the six-element system of Sn, Ag, Cu, Bi, Sb, and Ni. However, there is limited research on the influence of Co element within this system. In this study, a Sn 3.0Ag 0.5Cu Bi Sb Ni xCo (x = 0 wt%, 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%) alloy (referred to as SACBSN-xCo alloy) was prepared using a melting method. The mechanical properties of SACBSN-xCo alloy solder joints were evaluated through ultimate shear strength testing. The composition analysis of the alloy, phase composition examination, intermetallic compound (IMC) investigation and interfacial layer morphology analysis were conducted using ICP, XRD, SEM and EDS techniques respectively. Furthermore, the evolution process of solder structure and solder joint interface layer under different aging times was observed in detail. Results indicate that with the addition of Co element in the alloy solder system two heat release peaks appear during the solidification process; specifically when adding 0.05 wt% Co element content to the mixture it reduces supercooling degree by 15.17 °C to only 1.03 °C; Moreover wettability improvement can be achieved to some extent when adding either 0.02 wt% or 0.05 wt% Co content. The addition of trace Co can inhibit the excessive growth of IMC in the solder alloy matrix and refine the alloy structure. It can promote the growth of Cu 6 Sn 5 -based IMCs and inhibit the growth of Cu 3 Sn layer in intermetallic compound layer (IMCs). In addition, the mechanical properties and thermal fatigue stability of the solder joints are steadily improved by Co element. After adding Co element, the shear strength of the alloy solder joint is increased by about 14.84 %. After aging at 150 °C for 25 days, the shear strength of SACBSN-xCo alloy solder joints is increased by about 20.4 %, which significantly improves the thermal fatigue stability of the solder joints after high temperature aging treatment. The results show that when Co content is 0.05 wt%, the alloy solder has better comprehensive properties. • The addition of Co element can increase the nucleation point in the solder matrix, refine the structure, reduce the formation of large size intermetallic compounds and inhibit their overgrowth during high temperature treatment. • The addition of Co element can increase the nucleation density of IMC, and promote the growth of Cu6Sn5-based IMCs. Thicker Cu6Sn5-based IMCs act as a good diffusion barrier, preventing the mutual diffusion of Sn and Cu atoms. Thus impeding the growth of the Cu3Sn layer. • The addition of Co can effectively improve the shear resistance of the solder joint, and make the shear resistance of the solder joint show excellent stability in the process of high temperature aging treatment. [ABSTRACT FROM AUTHOR]

Ag-containing solder alloys are widely used in high-end electronic soldering processes to improve the reliability of electronic components. This study investigates the precipitation process of Ag 3 Sn during solidification. The precipitation of β-Sn, Ag 3 Sn, and η′-Cu 6 Sn 5 in SnAg3Cu0.5/Cu solder joints during solidification was examined using Thermo-Calc (2020a). Furthermore, the crystallographic structure of Ag 3 Sn/β-Sn and Ag 3 Sn/η′-Cu 6 Sn 5 was analyzed by transmission electron microscopy. The results showed that, below 217.1 °C, the η-Cu 6 Sn 5 phase begins to precipitate: β-Sn + Ag 3 Sn+η-Cu 6 Sn 5. At the Ag 3 Sn / β-Sn interface, the angle between (1 ‾ 2 1 ‾) A g 3 S n and (10 1 ‾) β − S n planes was measured to be 176.4°, with a mismatch of 26.47 %. The Ag 3 Sn / Cu 6 Sn 5 interface exhibited a specific crystallographic relationship of [ 223 ] A g 3 S n // [ 1 ‾ 12 ] C u 6 S n 5 , with an angle between (21 2 ‾) A g 3 S n and [ 402 ] C u 6 S n 5 planes of 101.5°. The growth patterns of β-Sn, Ag 3 Sn, and Cu 6 Sn 5 phases during isothermal aging were further investigated according to their interface orientation relationship, providing a basis for improving the stability of the soldering process. • Precipitation of β-Sn occurred when the temperature is cooled below 220.0 °C. Ag 3 Sn and η′-Cu 6 Sn 5 were distributed in blocks, with η′-Cu 6 Sn 5 possessing a large size. • The Ag 3 Sn / β-Sn exhibited [ 141 ] β − S n // [ 012 ] A g 3 S n relationship and 176.4° angle between (1 ‾ 2 1 ‾) A g 3 S n and (10 1 ‾) β − S n . • The Ag 3 Sn / Cu 6 Sn 5 exhibited [ 223 ] A g 3 S n // [ 1 ‾ 12 ] C u 6 S n 5 relationship and 36.1° angle between (21 2 ‾) A g 3 S n and (402) C u 6 S n 5 . [ABSTRACT FROM AUTHOR]

Recently multi-alloying has been used for optimization of the SnAgCu (SAC) solder. To comprehensively reveal the effects of multi-alloying on mechanical property of the SAC solder, in this study the Sb, Bi, Ni, In and Ce elements were added into the Sn-3.8Ag-0.7Cu (wt%) solder, then the deformation and fracture behaviors of the multi-alloyed SAC solder (MAS) and MAS/Cu solder joint were in-situ observed and compared with the SAC. The results reveal that more intermetallic compounds (IMCs) and some Bi particles are formed in the MAS, while the (Cu,Ni) 6 Sn 5 IMC in the MAS is refined. Due to the solid solution strengthening and precipitation strengthening, yield strength of the MAS increases by about 25 % compared with the SAC. Under tensile stress, severe slip and grain rotation occurs in the SAC solder, while plastic deformation of the MAS is restrained to a high extent by the dispersed particles within it. The MAS fractures in a tearing mechanism without obvious necking, but still shows a relative high elongation (~35 %), and the MAS has superior creep resistance since the dislocation motion and grain rotation are restrained. The deformation mismatch between the MAS and the Cu substrate is less serious, and the IMC at the MAS/Cu interface are less likely to fracture, resulting in a higher tensile strength (~160 MPa). Multi-alloying is recommended to improve the strength and creep resistance of the SAC. • The deformation behaviors of the multi-alloyed SAC solder (MAS) are investigated. • In-situ observation was employed to show the dynamic deformation process. • The grain rotation and strain localization are restrained in the MAS. • The MAS fractures at a strain of 35 % without necking. • The MAS shows much higher creep resistance than the SAC. [ABSTRACT FROM AUTHOR]

[Display omitted] • A model of nucleation and growth of intermetallic compounds during welding was proposed. • The diffusion coefficient decreases exponentially during the nucleation and growth of intermetallic compounds until thin layers are formed. • The diffusion patterns between matrix and different intermetallic compounds are different. In this study, the formation and growth of intermetallic compounds (IMC) at Sn/Cu interface were studied by using the molecular dynamics method of modified embedded atom method (MEAM) potential combined with practical experiments. The formation and growth process models of IMC layer at the initial stage of soldering were improved, and the growth trend and mechanism of IMC layer were analyzed. Further analysis of diffusivity shows that the diffusivity changes exponentially during welding and is related to the nucleation and growth of intermetallic compounds. Thus, this study provides valuable insights for the subsequent study on the initial stage of Sn/Cu interface and Sn/Cu solder joint reliability. [ABSTRACT FROM AUTHOR]

Herein, we prove that alloying of reactive nanoparticles can improve nanoparticles/β-Sn interfacial bonding and influence the solder alloy's melting point. Furthermore, the alloying effect can enhance the creep resistance of solder alloy. 0-0.5 wt% Ag nanoparticles (NPs) were added to Sn3.0Ag0.5Cu (SAC305) solder paste by mechanical stirring for the preparation of composite solder alloys, which were then extracted from the composite solder pastes. The joints were observed by scanning electron microscope and transmission electron microscope. The elementary composition of the prepared alloys was analyzed by electron dispersive spectrometer. The melting properties of alloys were tested by differential scanning calorimeter. The influences of Ag NPs as reactive nanophase on solder microstructure and melting properties were studied. The results indicated the existence of transition layer at the interface between Ag NPs and β-Sn. Additionally, the interfacial bonding improved after Ag NPs converted to Ag 3 Sn NPs. Due to Ag NPs alloying and solder alloy microstructure refinement being affected, melting points of alloys increased with 0-0.2 wt% addition of Ag NPs and decreased with 0.2–0.5 wt% addition. • A transition layer 2–4 nm wide is obtained at "Ag nanoparticles/β-Sn" interface. • Ag nanoparticles are transformed into Ag 3 Sn nanoparticles after welding. • The interfacial bonding of "nanoparticles/β-Sn" interface improves post alloying. • The alloying effect can influence the composite solder alloy's melting point. [ABSTRACT FROM AUTHOR]