Interface reaction systematics in the Cu/In–48Sn/Cu system bonded by diffusion soldering

• Published in: Intermetallics Vol. 15; no. 7; pp. 912 - 917
• Main Authors: Sommadossi, S., Guillermet, A. Fernández
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2007
• Subjects: A. Intermetallics, miscellaneous; B. Phase identification; B. Phase transformations; C. Joining; D. Phase interfaces; B. Phase identification; B. Phase transformations; D. Phase interfaces; A. Intermetallics, miscellaneous; C. Joining
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2006.10.050

An alternative lead-free solder alloy In–48 at%Sn with a melting point of 120 °C and its implementation to bond Cu substrates in a diffusion soldering joining method are presented. According to the EPMA, TEM/EDX and electron diffraction analyses, two different behaviors were observed in the interconnection zone depending on the temperature range: (i) a single layer consisting of η phase below 200 °C; (ii) a Cu-poor region consisting of η phase and a Cu-rich layer formed by a mixture of thin alternate regions of ζ-Cu 10Sn 3 and δ-Cu 7In 3 phases perpendicular to the interconnection plane above 200 °C. The η layer shows two morphologies: large grains and fine grains at the η/In–48Sn (liquid) and at the η/Cu-rich interfaces, respectively. Additionally, the η region shows a gradual change in composition, suggesting a change from the Cu 6Sn 5 to the Cu 2In structures. Thermal stability tests indicate that the thermal resistance of the bonds is about 750 °C.