Sn58Bi Solder Joints Research Articles

Effect of Mo and ZrO2 nanoparticles addition on interfacial properties and shear strength of Sn58Bi/Cu solder joint

The influence of Mo and ZrO2 nanoparticles addition on the interfacial properties and shear strength of Sn58Bi solder joint was investigated. The interfacial microstructures of Sn58Bi/Cu, Sn58Bi + Mo/Cu and Sn58Bi + ZrO2/Cu solder joints were analysed using a scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX) and the X-ray diffraction (XRD). Intermetallic compounds (IMCs) of MoSn2 are detected in the Sn58Bi + Mo/Cu solder joint, while SnZr, Zr5Sn3, ZrCu and ZrSn2 are detected in Sn58Bi + ZrO2/Cu solder joint. IMC layers for both composite solders comprise of Cu6Sn5 and Cu3Sn. The SEM images of these layers were used to measure the IMC layer’s thickness. The average IMC layer’s thickness is 1.4431 µm for Sn58Bi + Mo/Cu and 0.9112 µm for Sn58Bi + ZrO2/Cu solder joints. Shear strength of the solder joints was investigated via the single shear lap test method. The average maximum load and shear stress of the Sn58Bi + Mo/Cu and Sn58Bi + ZrO2/Cu solder joints are increased by 33% and 69%, respectively, as compared to those of the Sn58Bi/Cu solder joint. By comparing both composite solder joints, the latter prevails better as adding smaller sized ZrO2 nanoparticles improves the interfacial properties granting a stronger solder joint.

Effects of TiC nanoparticle addition on microstructures and mechanical properties of Sn-58Bi solder joints

The Sn58Bi solder has gained significant attention in the electronic packaging industry owing to its low melting temperature and excellent mechanical properties. However, the brittleness of Sn58Bi solder presents challenges in practical applications. This study investigates the effect of adding titanium carbide (TiC) nanoparticles on the mechanical properties of Sn58Bi solder joints. The study examines the melting behavior, spreadability, microstructure, and mechanical properties of Sn58Bi-xTiC (x = 0, 0.05, 0.1, 0.2 wt%) composite solders. The results indicate that adding TiC nanoparticles has merely a minor effect on the melting point of the Sn58Bi solder. However, the presence of TiC nanoparticles refined the solder’s microstructure, reduced the thickness of the intermetallic compounds, and enhanced the spreadability and mechanical properties. The Sn58Bi-0.1TiC composite solder exhibits the most favorable properties, including a 28.6 % increase in fracture energy compared with that of Sn58Bi solder. Consequently, incorporating TiC nanoparticles enhances the performance of the Sn58Bi solder by improving its spreadability and reducing its brittleness. These results hold great potential for advancing the development of lead-free solders with improved reliability and performance in electronic applications. The findings of this study could pave the way for the practical and widespread use of Sn58Bi-xTiC composite solders, offering a viable alternative to lead-containing solders while maintaining excellent mechanical characteristics.

Ni and Ni–P substrates inhibit Bi phase segregation and IMC overgrowth during the soldering process of Sn–Bi solder

In this paper, presents surface modification of Cu substrates by electroplating or chemical plating to obtain high-quality Ni and Ni–P coatings. The Sn58Bi solder reactions with Cu, Ni, and Ni–P UBMs at 180 °C, 250 °C, and 320 °C, respectively. Research has found that Ni and Ni–P substrates can inhibit Bi phase segregation and interfacial IMC overgrowth in Sn–Bi solder joints. Bi phase segregation occurs during the transition from Cu6Sn5 to Cu3Sn. There is Bi segregation at the interface of Sn58Bi/Cu solder joints to Cu3Sn/Cu interface, and IMC grows rapidly. However, Ni/Cu and Ni–P/Cu substrates can not only suppress the Bi phase segregation behavior of Sn58Bi solder joints during soldering, but also slow down the excessive growth of interfacial IMC; Even under the harsh soldering process of up to 320 °C for 600 s, it still has an effective blocking effect. In addition, at 320 °C, when Sn58Bi solder react with Cu, the interface directly crosses Cu6Sn5 to generate Cu3Sn, which exhibits the morphology characteristics of Cu6Sn5 due to high thermal conditions. During the soldering, Ni atoms continuously diffuse towards the interface, and Ni3Sn4 (Ni/Cu) grows from needle like in the early stage of soldering to rod like, and finally to block like; The block like appearance of Ni3Sn4 (Ni–P/Cu) occurs earlier than that of Ni3Sn4 (Ni/Cu), because the presence of columnar Ni3P layers provides a wider diffusion channel for Ni atoms, but the overall growth size is smaller than that on Ni/Cu. A higher undercooling can promote the growth of interfacial IMC, including Cu6Sn5 and Ni3Sn4. At the same time, the Bi phase inside the Sn58Bi solder joint is coarsened, and the substrate Ni/Ni–P can eliminate interfacial brittleness after eliminating Bi segregation.

Effect of (111) oriented nanotwinned Cu substrate on the electromigration of Sn58Bi solder joint at high current density

Effect of (111) oriented nanotwinned Cu substrate on the electromigration of Sn58Bi solder joint at high current density

Research Overview on the Electromigration Reliability of SnBi Solder Alloy.

Due to the continuous miniaturization and high current-carrying demands in the field of integrated circuits, as well as the desire to save space and improve computational capabilities, there is a constant drive to reduce the size of integrated circuits. However, highly integrated circuits also bring about challenges such as high current density and excessive Joule heating, leading to a series of reliability issues caused by electromigration. Therefore, the service reliability of integrated circuits has always been a concern. Sn-based solders are widely recognized in the industry due to their availability, minimal technical issues during operation, and good compatibility with traditional solders. However, solders that are mostly Sn-based, such as SAC305 and SnZn, have a high melting point for sophisticated electronic circuits. When Bi is added, the melting point of the solder decreases but may also lead to problems related to electromigration reliability. This article reviews the general principles of electromigration in SnBi solder joints on Cu substrates with current flow, as well as the phenomena of whisker formation, voids/cracks, phase separation, and resistance increase caused by atomic migration due to electromigration. Furthermore, it explores methods to enhance the reliability of solder joint by additives including Fe, Ni, Ag, Zn, Co, RA (rare earth element), GNSs (graphene nanosheets), FNS (Fullerene) and Al2O3. Additionally, modifying the crystal orientation within the solder joint or introducing stress to the joint can also improve its reliability to some extent without changing the composition conditions. The corresponding mechanisms of reliability enhancement are also compared and discussed among the literature.

Fractography analysis of Sn-58Bi solder joint after addition of cobalt nanoparticles

Fractography analysis of Sn-58Bi solder joint after addition of cobalt nanoparticles

Effect of Trace Boron Nitride Nanoparticles on the Microstructure and Shear Properties of Sn58Bi Solder Joint

Effect of Trace Boron Nitride Nanoparticles on the Microstructure and Shear Properties of Sn58Bi Solder Joint

Thermal stability of epoxy-based Sn-58Bi solder joint

The epoxy(EP)-based Sn-58Bi solder paste consists of a curable flux and Sn-58Bi particles. In addition to its function as a flux, the curable flux forms a cured shell on the periphery of the solder joint. Under appropriate process parameters, the EP-based Sn-58Bi solder paste can form solder joints with a shell-core structure on the Cu substrate. Compared to conventional Sn-58Bi solder paste, the solder joint of EP-based Sn-58Bi solder paste has a higher heat resistance and joint strength. To investigate the heat resistance of the solder joint of EP-based Sn-58Bi solder paste, the thermal cycle test was carried out in the temperature range of 130-170°C. Metallographic microscopy and scanning electron microscopy (SEM) were used to observe the interfacial microstructure of the solder joints and to analyze the difference in the microstructure of the solder joints in relation to the thermal history. The results show that the solder joint interface of the EP-based Sn-58Bi solder paste is more stable than that of the conventional Sn-58Bi solder paste, indicating that the cured EP shell on the periphery of the solder joint can effectively improve the thermal stability of the solder joint.

Study on the properties of epoxy-based Sn[sbnd]58Bi solder joints

In electronic packaging technology, Sn58Bi alloy solder has the advantages of low-temperature soldering and high shear strength of solder joint. It has a wide range of application in the electronics industry for low-temperature soldering, especially for temperature-sensitive substrates. Epoxy-based Sn58Bi solder paste is a mixture of curable flux and Sn58Bi solder powder. During the soldering process, the curable flux, in addition to the functions of a conventional flux, forms a cured epoxy shell around the periphery of the solder joint, which can effectively improve the shear strength and thermal stability of the solder joint. In this study, a self-made epoxy-based Sn58Bi solder paste was prepared and the properties of the solder joints were investigated. The results show that epoxy-based Sn58Bi solder paste has better wettability than traditional Sn58Bi solder paste without epoxy resin. And the shear strength of epoxy-based Sn58Bi solder joint is about 25 % higher than that of traditional Sn58Bi solder joint. Furthermore, the electrical conductivity of epoxy-based Sn58Bi solder joint has the same order of magnitude as that of traditional Sn58Bi solder joint, which means that non-conductive epoxy resin has no effect on the electrical conductivity of the epoxy-based Sn58Bi solder joint.

Effect of Cu on the diffusion behavior of Bi in Sn matrix during electromigration

The segregation of Bi phase during current stressing deteriorates the mechanical property of Sn-58Bi solder joint. To improve the reliability of Sn-58Bi solder joint, a thorough understanding of the diffusion behavior of Bi elements is necessary. In this study, a Cu/SnBi/Sn-xCu/SnBi/Cu multi-layer solder joint structure was adopted to reveal the diffusion path of Bi element and the effect of Cu on the diffusion behavior of Bi during electromigration. The result showed that the Bi element diffused along the grain boundary. The presence of Cu had two competing mechanisms on the diffusion of Bi: it slowed the process by forming Cu6Sn5 intermetallic compounds that blocked and prolonged the diffusion path, yet also accelerated it by refining the Sn and creating more diffusion channels. A data processing method was used to estimate the diffusion rate of Bi and determine the dominant mechanism. The results indicated that the diffusion rate was accelerated by Cu doping, confirming that the dominant mechanism was the refining effect, which promoted the diffusion of Bi element.

Effect of multi-walled carbon nanotubes on the microstructure and properties of Sn-58Bi solder alloys

The influence of multi-walled carbon nanotube (MWCNT) content on the melting properties, wettability, microstructure, and intermetallic compounds (IMCs) of Sn-58Bi-xMWCNT (x = 0, 0.01, 0.02, 0.03, 0.05, and 0.10 wt.%) and the effects of MWCNT on the tensile strength of Cu/Sn-58Bi-xMWCNT/Cu solder joint were analyzed. The results show that MWCNT addition at a small trace amount into Sn-58Bi solder could increase the spreading area of Sn-58Bi solder, refine the solder matrix microstructure, inhibit the growth of interfacial IMCs, and significantly improve the tensile strength of Sn-58Bi solder joints. However, the melting point and melting range remained the same or slightly changed. The wettability of Sn-58Bi alloys increased first and then decreased with the addition of MWCNT. The spreading area and the tensile strength of solder joint were the maximum when the MWCNT content was 0.01 wt.%, and they were 42.23 mm2 and 50.07 MPa, respectively. The reason may be related to the improved microstructure of solder alloys and the morphology of IMCs due to MWCNT addition at trace level.

Preparation and performance of Sn-based composite solder joints by solid-liquid low-temperature solder bonding technology

In the era of big data, the advantages of 3D packaging are becoming increasingly significant. In addition, the mismatch between the coefficient of thermal expansion (CTE) of the PCB and BGA components leads to dynamic warpage of the system, and the expansion and innovation of low-temperature soldering have been a new trend. We developed a fully mixed solder joint of a SAC305(Sn-3.0Ag-0.5Cu wt.%) solder ball and Sn–58Bi(wt.%) solder paste by solid-liquid low-temperature solder bonding technology. The mixing degree and diffusion process of the two were calculated and simulated by mathematical calculation and COMSOL Multiphysics. The results show that a completely mixed solder joint can be obtained after reflow at 210 °C for 5 min. The average shear strength of the composite solder joints was 63.68 ± 1.12 MPa, which was about twice that of the single SAC305 and Sn58Bi solder joints, and the shear fracture was a composite mode of brittle and ductile fracture, which appeared in the IMC and the solder, respectively. After complete mixing, the solder wettability angle was less than 26.68°, with outstanding wetting properties. No phase transition occurred after aging, the distribution of each phase remained uniform, and no enrichment of the brittle phase was observed at the interface. The shear strength decreased slightly with aging time, and the reduction value was less than 10 MPa, which has good reliability.

Microstructure changes in Sn-Bi solder joints reinforced with Zn@Sn particles in thermal cycling and thermomigration

BackgroundIn the field of electronic packaging, Sn-58Bi solder paste is a promising low-temperature option for step soldering. However, the tendency for the Bi-rich phase to coarsen and segregate poses a significant challenge to the long-term reliability of the solder joints. MethodsThe Sn coated Zn (Zn@Sn) core-shell particles were prepared through a chemical plating process and incorporated into the Sn-58Bi low-temperature solder paste to enhance its reliability. The microstructural and mechanical characteristics of the solder joints were evaluated under thermal cycling and thermomigration conditions to assess their long-term service reliability. Significant findingsThe addition of Zn lowers the nucleation energy and promotes the refinement of the eutectic structure, avoiding a significant reduction in shear strength after thermal cycling. In thermomigration, the heat transfer Q* of Bi is calculated to be 22.5 kJ/mol. The Zn-rich phases hardly move and are evenly distributed within the solder joints, acting like a barrier to prevent the Bi phase diffusing from the hot end to the cold end.

Effects of alloying elements on the interfacial segregation of bismuth in tin-based solders

Sn-Bi solders are potential candidates for replacing traditional lead-based solders in electronic packaging due to their low melting points, superior wettability, and mechanical properties. The grain coarsening due to the interfacial Bi segregation is a vital issue that affects the reliability of Sn-Bi solder joints. Through first-principles calculations, this study systematically revealed the effects of different alloying elements on the interfacial segregation of Bi towards Sn(100) surface. Bi tends to segregate to the top-surface of Sn due to the formation of vacancies on Sn surface. However, doping alloying elements into the Sn-Bi solders could effectively suppress the interfacial Bi segregation. The presence of elements such as Pd, Pt, and Au located at the adjacent surface layer of Bi could inhibit the Bi precipitation, by apparently increasing the segregation energies of Bi to the Sn surface. The results can be interpreted by the enhanced bond orders and charge transfer between Bi, alloying elements, and their neighboring Sn atoms. This study could provide valuable insights into the design of multi-component Sn-Bi solders with minor alloying elements doping in the future.

Effect of Ni-modified reduced graphene oxide on the mechanical properties of Sn–58Bi solder joints

Sn–58Bi solder has great research value as a low-temperature solder. However, it still requires strengthening due to a lot of brittle Bi-phase, which reduces mechanical reliability. In this study, Ni-modified reduced graphene oxide (rGO@Ni) was prepared by heat reduction, and mechanical stirring was used to manufacture rGO@Ni-reinforced Sn–58Bi composite solder. The distribution, phase composition, and structural changes of graphene and Ni nanoparticles during enhancer synthesis were characterized in detail by Scanning Electron Microscope, Energy Dispersive Spectroscopy Raman and Fourier Transform Infrared spectra, X-ray Photoelectron Spectroscopy, X-ray Diffraction, and Transmission Electron Microscope. Besides, the morphology of intermetallic compound (IMC) layers of the composite solder/Cu interface was investigated. The thickness of the IMC layer decreases with the increase of rGO@Ni content. The microstructure analysis demonstrated that the rGO@Ni distributed near the IMC layer, which limits the diffusion of metal atoms and decreases the IMC layer's growth rate during the reflowing process. Besides, compared with Sn–58Bi solder alloys, the addition of 0.01 wt% rGO@Ni can increase the shear strength by up to 15%. However, when the content of rGO@Ni is more than 0.05 wt%, it agglomerates inside the composite solder, resulting in a decrease in the shear strength of the composite solder joint.

Effects of cobalt nanoparticle on microstructure of Sn58Bi solder joint

Effects of cobalt nanoparticle on microstructure of Sn58Bi solder joint

Effects of Sn-Ag-x leveling layers on the microstructure and shear behavior of Sn-58Bi solder joint under thermal cycling

Effects of Sn-Ag-x leveling layers on the microstructure and shear behavior of Sn-58Bi solder joint under thermal cycling

Diffusion Barrier Properties of the Intermetallic Compound Layers Formed in the Pt Nanoparticles Alloyed Sn-58Bi Solder Joints Reacted with ENIG and ENEPIG Surface Finishes

Pt-nanoparticle (NP)-alloyed Sn-58Bi solders were reacted with electroless nickel-immersion gold (ENIG) and electroless nickel-electroless palladium-immersion gold (ENEPIG) surface finishes. We investigated formation of intermetallic compounds (IMCs) and their diffusion barrier properties at reaction interfaces as functions of Pt NP content in the composite solders and duration of solid-state aging at 100 °C. At Sn-58Bi-xPt/ENIG interfaces, typical Ni3Sn4/Ni3P(P-rich layer) microstructure was formed. With the large consumption of the Ni-P layer, the Ni-P and Cu layers were intermixed and Cu atoms spread over the composite solder after 500 h of aging. By contrast, a (Pd,Ni)Sn4/thin Ni3Sn4 microstructure was observed at the Sn-58Bi-xPt/ENEPIG interfaces. The (Pd,Ni)Sn4 IMC effectively suppressed the consumption of the Ni-P layer and Ni3Sn4 growth, functioning as a good diffusion barrier. Therefore, the Sn-58Bi-xPt/ENEPIG joint survived 500 h of aging without microstructural degradation. Based on the experimental results and analysis of this study, Sn-58Bi-0.05Pt/ENEPIG is suggested as the optimum combination for future low-temperature soldering systems.

Correction: Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Correction: Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint

Effect of cobalt nanoparticles on mechanical properties of Sn–58Bi solder joint