Microstructure and properties of Sn58Bi/Ni solder joint modified by Mg particles

Abstract

In this paper, various mass fractions (0, 0.1, 0.2, 0.4, 0.6, 0.8 wt%) of Mg particles were added to the Sn58Bi solder to achieve the purpose of modification, through which the Ni substrate was connected successfully through bonding at 250 °C for 2 min. Meanwhile, the microstructure, interfacial IMC, and properties of the joint were focused on. The experimental results indicated that the appropriate addition of Mg particles is able to decrease the melting point of the solder quite slightly and significantly improve the wettability of the solder on the Ni substrate. When the content of Mg is less than 0.4 wt%, the presence of MgO on the surface does not affect the normal use of solder. Likewise, Mg particles are capable of refining the microstructure of the solder and reducing the thickness of the interfacial Ni3Sn4 IMC layer and the grain size. Accordingly, the mechanical property of the joint is markedly enhanced by 53.48%, whose fracture is mainly characterized by brittle fracture, and the Mg2Sn phase plays the central role of strengthening. In a word, it is the Sn58Bi-0.4Mg/Ni solder joint that processes the best combination performance.

Keywords

• Sn58Bi solder
• Mg particles
• Solder joints
• Interfacial IMC
• Mechanical properties