Crystal Structure of Cu-Sn-In Alloys Around the η-Phase Field Studied by Neutron Diffraction

• Published in: Journal of electronic materials 2012-11, Vol.41 (11), p.3223-3231
• Main Authors: Aurelio, G., Sommadossi, S.A., Cuello, G.J.
• Format: Article
• Language: English
• Subjects: Alloys; BONDING; Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: structure, mechanical and thermal properties; Constitution; Copper; COPPER TIN ALLOYS; CRYSTAL STRUCTURE; Electron probes; Electronics and Microelectronics; Exact sciences and technology; Instrumentation; INTERMETALLIC COMPOUNDS; Materials Science; NEUTRON DIFFRACTION; Neutron diffraction and scattering; Optical and Electronic Materials; PHASES; Physics; QUENCHING MECHANISMS; SCANNING ELECTRON MICROSCOPY; Single-crystal and powder diffraction; Solid State Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; TERNARY PHASE DIAGRAMS; Ternary systems
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-012-2193-4

Study of the Cu-Sn-In ternary system has become quite important in recent years, due to new environmental regulations increasingly restricting use of Pb for bonding technologies in electronic devices. A key relevant issue concerns the intermetallic phases which grow in the bonding zone and strongly affect its quality and performance. In this work, we focus on the η-phase (Cu 2 In or Cu 6 Sn 5 ) that exists in both end binaries and as a ternary phase. We present a neutron diffraction study of the constitution and crystallography of a series of alloys around the 60 at.% Cu composition, and with In contents ranging from 0 at.% to 25 at.%, quenched from 300°C. The alloys were characterized by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and high-resolution neutron diffraction (ND). Rietveld refinement of ND data allowed improvement of the currently available model for site occupancies in the hexagonal η-phase in the binary Cu-Sn as well as in ternary alloys. For the first time, structural data are reported for the ternary Cu-Sn-In η-phase as a function of composition, information that is of fundamental technological importance as well as valuable for ongoing modeling of the ternary phase diagram.