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Typical SEM images of solder joints with: (a) interfacial morphology of Sn–58Bi/Cu, (b) EDS line scan of Sn–58Bi/Cu, (c) interfacial morphology of Sn–57Bi–1.0Cu/Cu, (d) EDS line scan of Sn–57Bi–1.0Cu/Cu, (e) interfacial morphology of Sn–57.9Bi–0.1P/Cu, (f) EDS line scan of Sn–57.9Bi–0.1P/Cu.
Source publication
Sn–(58-x) Bi–x Cu/P ternary alloys were prepared by downward continuous casting, and the microstructure of the alloy was characterized using scanning electron microscopy (SEM), x-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The results show that the addition of Cu and P can refine the eutectic structure and form rod-shaped...
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Citations
... %) irregular eutectic dendrites [14]. [15][16][17]. ...
Sn-based lead-free solder alloys have been explored extensively as an alternative to the conventional Sn–Pb solder alloys. While the miniaturization of electronic devices and the growth of appliance area, the corrosion resistance of solder alloys play a crucial element in the reliability of electronic devices in a prolonged period of service. This paper determines the corrosion effect of Sn-Bi solder lead-free solder, particularly immersed in alkaline solution which is potassium hydroxide. Morphological and elemental analyses reveal the formation of oxides on the surface after immersion after using a scanning electron microscope, dispersive energy X-ray and X-ray diffraction. The result of morphology reveals that the Sn matrix in plateau indicated dark contrast while Bi-rich in the lamellar eutectic structure indicated in light contrast appearance. In addition, phase and elemental analyses revealed the formation of mixed corrosion products of SnO, SnO 2 and Bi 2 O 3 on the surface after testing. It is hoped that this finding will provide some helpful evidence in clarifying the corrosion progress of lead-free solder alloys. Furthermore, the remaining corrosion potential and current of Sn-Bi in 6 M potassium hydroxide solutions in this research are proposed.
... The coarsening of Bi phase is considered as the main reason for the deterioration of the mechanical properties of SnBi solder joint. Especially under the isothermal aging condition, the mechanical performances of solder joint degrade sharply, which limits the further application of SnBi solder in electronic packaging industry [8][9][10][11]. ...
A comparison of the microstructure, interfacial IMC layer, shear behavior and hardness of the Sn58Bi, [email protected]/Cu and [email protected]/Cu solder joints was carried out during isothermal aging in this study. Experimental results reveal that the regions enclosed by Cu frames in [email protected]/Cu exhibit more refined microstructure and higher hardness before and after aging. In contrast, the hardness of the aged [email protected] solder bulk is closer to the SnBi eutectic solder due to their similar microstructure. With the aging time prolonging, β-Sn and Bi-rich phases do not only coarsen in solder joints, but also lead to the rise of the thickness of the interfacial IMC layers. The addition of porous Cu can suppress the formation of voids at the soldering interface and improves the shear strength of the SnBi/Cu solder joints during the aging process. The shear strength of the [email protected]/Cu solder joint is higher than the other two before and after aging.
The Cu/Sn58Bi/Cu and Cu/Sn58Bi-0.6B4C/Cu joints were prepared by transient liquid phase (TLP) bonding technology to verify the reliability of low-temperature connection joints. Intermetallic compound (IMC) evolution at the interface under different isothermal aging times was analyzed, and the mechanical properties of the joints were tested. The results show that two kinds of IMC, lamellar Cu3Sn and fan-shaped Cu6Sn5, are formed on both sides of the joint. With increasing soldering time, the thickness for both kinds of IMC become thicker, and it is significantly thicker for the IMC near the cold end. Furthermore, the IMC growth rate of the Cu/Sn58Bi-0.6B4C/Cu solder joint is significantly lower. When the isothermal aging time reaches 36 h, the Cu/Sn58Bi/Cu joint has been almost composed of IMC, while it needs a longer time for the Cu/Sn58Bi-0.6B4C/Cu joint. The growth of Cu3Sn IMC is in line with parabolic law, being mainly controlled by volume diffusion near the hot end, while the grain boundary diffusion significantly affects it at the cold end. The joints shear strength decreases gradually with extending bonding time, but it is always higher for the Cu/Sn58Bi-0.6B4C/Cu joint. When the heating time is not long, the fracture mainly appears at the Bi-rich phase in the solder matrix. With increasing bonding time, the location of fracture gradually transformed from the Cu6Sn5 grains to the junction of the two IMC and Cu3Sn grains, along with the intercrystalline fracture and transcrystalline fracture. In summary, B4C nanoparticles can significantly improve the joint reliability and enhance its mechanical properties.
