Gold/Tin (Au80/Sn20) eutectic alloy is one of the most widely used high-performance solder materials, valued for its excellent thermal and electrical conductivity, corrosion resistance, and mechanical stability. Its ability to form strong, hermetic joints makes it indispensable in microelectronics, optoelectronics, and aerospace packaging applications.
Material Overview
Composed of 80 % gold and 20 % tin by weight, the Au80/Sn20 alloy is a eutectic system with a sharp melting point of 280 °C. The alloy’s microstructure consists primarily of a eutectic mixture of Au5Sn (ζ′ phase) and AuSn (δ phase), forming a lamellar structure that contributes to both high strength and good thermal fatigue resistance. The fine-scale eutectic morphology ensures low voiding and uniform bonding interfaces. Mechanical studies have shown that hardness and elastic modulus can be enhanced through rapid solidification techniques, with values increasing from 1.67 to 2.17 GPa and from 70.6 to 83.2 GPa respectively as cooling rates increase (Zeng et al., 2019). In addition, controlled annealing reduces internal stresses and improves ductility, facilitating fine stamping and precision joining processes (Yao et al., 2019).
Applications and Advantages
Au80/Sn20 alloy is extensively used in semiconductor die attach, photonics packaging, hermetic sealing, and medical device assembly. Its high wetting capability on ceramics and metals ensures excellent adhesion and minimal oxidation during reflow soldering. In microelectronic systems, Au–Sn joints exhibit outstanding thermal conductivity (~57 W·m−1·K−1) and strong creep resistance under cyclic temperature variations (Arabi et al., 2016). The alloy’s chemical inertness and long-term reliability make it particularly suitable for space and defense electronics where performance under extreme conditions is critical. Advanced processing techniques, including co-electroplating and vacuum suction casting, further enhance compositional uniformity and bonding precision (Sun & Ivey, 2001; Ma, 2013).
Goodfellow Availability
Goodfellow supplies Gold/Tin (Au80/Sn20) alloy in high-purity form for advanced electronic, optical, and hermetic sealing applications. Available in customized geometries such as foils, preforms, or rods, the alloy meets the stringent requirements of precision joining and high-reliability packaging.
Explore Gold/Tin Au80/Sn20 and other advanced materials in Goodfellow’s online catalogue: Goodfellow product finder.
References
- Zeng, X., Ma, Y., Liu, W., Huang, Y., Tang, S., & Chen, B. (2019). Effect of suction casting process on microstructure and mechanical properties of Au80Sn20 alloy flake. Materials Research Express, 6(5), 056515. https://doi.org/10.1088/2053-1591/ab15e7
- Yao, Y., Liu, W., Ma, Y., Huang, Y., Tang, S., & Chen, B. (2019). Investigation of stamping and heat treatment processes on the microstructure and blanking characteristics of Au80Sn20 eutectic alloy. Materials Research Express, 6(4), 045512. https://doi.org/10.1088/2053-1591/ab07fb
- Arabi, F., Théolier, L., Martineau, D., Deletage, J. Y., Medina, M., & Woirgard, E. (2016). Power electronic assemblies: Thermo-mechanical degradations of gold–tin solder for attaching devices. Microelectronics Reliability, 64, 268–275. https://doi.org/10.1016/j.microrel.2016.07.028
- Sun, W., & Ivey, D. G. (2001). Microstructural study of co-electroplated Au/Sn alloys. Journal of Materials Science, 36(5), 1117–1124. https://doi.org/10.1023/A:1004805512535
- Ma, Y. (2013). Research progress in preparation and application of Au80Sn20 solder alloy. Materials Review, 27(1), 56–62.