Reactions of Sn-4.0Ag-0.5Cu on Cu and Electroless Ni Substrate in Premelting Soldering Process

• Published in: Journal of electronic materials 2013-06, Vol.42 (6), p.1254-1259
• Main Authors: Chung, C. Key, Chen, Y. J., Yang, T. L., Kao, C. R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Brazing. Soldering; Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: structure, mechanical and thermal properties; Diffusion in solids; Electronics; Electronics and Microelectronics; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; General studies of phase transitions; Instrumentation; Joining, thermal cutting: metallurgical aspects; Lead free solders; Materials Science; Metals. Metallurgy; Nanostructured materials; Nucleation; Optical and Electronic Materials; Physics; Soldering; Solid State Physics; Solid-solid transitions; Specific phase transitions; Transport properties of condensed matter (nonelectronic)
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-013-2582-3

Early formation of Cu 6 Sn 5 and (Ni,Cu) 6 Sn 5 during soldering was investigated. Sn 4.0 Ag 0.5 Cu solder on Cu and electroless Ni-Au substrate was quenched in ice water after the initial stage of melting, and the solder–substrate interface was analyzed by transmission electron microscopy and energy-dispersive x-ray spectroscopy. At the contacting point, Cu 3 Sn and Cu 6 Sn 5 were found at the solder–Cu substrate interface, while (Ni,Cu) 6 Sn 5 and Ni 2 SnP were identified at the solder–electroless Ni interface. The contacting points were confirmed as the sites of heterogeneous nucleation. TEM analysis suggested that the nucleation of both intermetallic compounds can be attributed to diffusion-induced crystallization. Details of the early interfacial reactions are discussed.