Design and Performance Evaluation of Sn58Bi/SAC305 Layered Composite Solder for Low-Temperature Applications
Abstract
:1. Introduction
2. Materials and Methods
2.1. Design Principles and Fabrication of Sn58Bi/SAC305 Layered Composite Solder
2.2. Microstructural and Elemental Distribution Characterization
2.3. Soldering Process and Joint Performance Evaluation
2.4. Synchrotron X-Ray Real-Time Imaging Experiment
2.5. Evaluation of Shear Properties of Solder Joints
3. Results and Discussion
3.1. Microstructure of Layered Composite Solder
3.2. In Situ Observation of Interfacial Fusion Dynamics During Reflow
3.3. Soldering Performance of Layered Composite Solder
3.3.1. Fusion Behavior of Sn58Bi/SAC305 Layered Solder After Soldering
3.3.2. Interface Structure and Bi-Rich Phase Distribution After Soldering
3.3.3. Changes in Interface IMC with Soldering Temperature
3.4. Shear Properties of Layered Composite Solder Joints
3.4.1. Shear Strength
3.4.2. Fracture Morphology
4. Conclusions
- (1)
- The alternating layers of SAC305 and Sn58Bi enable controlled element diffusion during reflow. Bi diffusion into SAC305 reduces segregation, while the partial dissolution of SAC305 into molten Sn58Bi forms a sub-eutectic structure. Synchrotron imaging reveals that cellular interfaces arise from compositional supercooling, driven by localized Bi enrichment and rapid solidification at the solid–liquid boundary.
- (2)
- The fusion degree of layered solder increases with temperature, transitioning from a partially mixed “unfused SAC305 zone + cellular boundary zone + reticulated SnBi zone” (160–180 °C) to a fully homogenized structure (200 °C). The refined distribution of Ag3Sn and Cu6Sn5 phases at elevated temperatures enhances grain boundary strengthening, while excessive IMC growth at 220 °C degrades joint reliability.
- (3)
- Although melt-cast solders perform well at lower temperatures, the 7-layer composite solder reaches a peak shear strength of 44.3 ± 0.8 MPa at 200 °C, slightly surpassing Sn58Bi (41.8 ± 1.1 MPa). This is due to its uniform phase dispersion and optimized IMC thickness, making it suitable for applications that require both low-temperature assembly and high-temperature reliability. Fracture analysis indicates mixed ductile–brittle modes, with crack initiation predominantly at solder/IMC interfaces or heterogeneous layer boundaries.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Element | Sn | Bi | Ag | Cu |
---|---|---|---|---|
Mass% | 66.2 | 32.2 | 1.4 | 0.2 |
Element | Sn | Ag | Cu | Bi |
---|---|---|---|---|
1 | 25.6 | 70.8 | 2.7 | 0.9 |
2 | 24.1 | 74.3 | 1.0 | 0.6 |
3 | 48.9 | 0.1 | 50.7 | 0.3 |
4 | 49.5 | 0.1 | 50.3 | 0.1 |
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Zhang, Z.; Zhang, D.; Li, C.; Yang, W.; Ma, H.; Ma, H.; Wang, Y. Design and Performance Evaluation of Sn58Bi/SAC305 Layered Composite Solder for Low-Temperature Applications. Metals 2025, 15, 185. https://doi.org/10.3390/met15020185
Zhang Z, Zhang D, Li C, Yang W, Ma H, Ma H, Wang Y. Design and Performance Evaluation of Sn58Bi/SAC305 Layered Composite Solder for Low-Temperature Applications. Metals. 2025; 15(2):185. https://doi.org/10.3390/met15020185
Chicago/Turabian StyleZhang, Zhongxu, Dan Zhang, Chenyu Li, Wenlong Yang, Haitao Ma, Haoran Ma, and Yunpeng Wang. 2025. "Design and Performance Evaluation of Sn58Bi/SAC305 Layered Composite Solder for Low-Temperature Applications" Metals 15, no. 2: 185. https://doi.org/10.3390/met15020185
APA StyleZhang, Z., Zhang, D., Li, C., Yang, W., Ma, H., Ma, H., & Wang, Y. (2025). Design and Performance Evaluation of Sn58Bi/SAC305 Layered Composite Solder for Low-Temperature Applications. Metals, 15(2), 185. https://doi.org/10.3390/met15020185