PROBIEN   20416
INSTITUTO DE INVESTIGACION Y DESARROLLO EN INGENIERIA DE PROCESOS, BIOTECNOLOGIA Y ENERGIAS ALTERNATIVAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Interface Reaction Systematics in the Cu/In-48Sn/Cu System Bonded by Diffusion Soldering
Autor/es:
S. SOMMADOSSI , A. FERNÁNDEZ GUILLERMET
Lugar:
Nürnberg, Germany
Reunión:
Conferencia; EUROMAT 2007 The Federation of European Materials Societies; 2007
Institución organizadora:
The Federation of European Materials Societies FEMS
Resumen:
 The alternative lead-free solder alloy In-48at.%Sn with a melting point of 120°C and its implementation to bond Cu substrates in a diffusion soldering joining method is presented. According with 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 ç phase below 200 °C; (ii) a Cu-poor region consisting of eta phase and a Cu-rich layer formed by a mixture of thin alternate regions psi-Cu10Sn3 y delta-Cu7In3 phases perpendicular to the interconnection plane above 200 °C. The eta layer shows two morphologies: large and fine grains at the ç/In-48Sn(liquid) and at the eta/Cu-rich interfaces, respectively. Additionally, the eta region shows a gradual change in composition, suggesting a change from the Cu6Sn5 to the Cu2In structures. Thermal stability tests indicate that the thermal resistance of the bonds is about 750 °C. The thickness of the Cu-rich layer shows a constant growth rate (linear growth) at constant temperature. The temperature dependence of the growth rate constant of the Cu-rich layer is described by an Arrhenius relationship with an activation energy equal to 121 kJ/mol and a pre-exponential factor of about 57 m/s.The tensile and shear strengths and the (nanoindentation) hardness were measured to characterize the mechanical behaviour of the joints. The results show that the Cu-rich layer has better mechanical properties than the eta layer, which can withstand stresses above 155 MPa. The ultimate shear strength of the joints improves almost 3 times when the eta phase is converted into the Cu-rich layer by a solid-solid diffusion reaction process. The hardness measurements indicate that the most brittle layer is the eta layer.