During last few decades, emerging environmental regulations worldwide, more notably in Europe and Japan, have targeted the elimination of Pb usage in electronic assemblies due to the inherent toxicity of this element.This situation drives to the replacement of the SnPb solder alloy of eutectic composition commonly used as joining material to suitable lead-free solders for microelectronic assembly. Sn-based alloys containing Ag, Cu, Bi, and Zn are potential lead-free solders, usually close to the binary or ternary eutectic composition. For this reason a great effort was directed to establish reliable thermophysical data fundamental to interpret the solidification process and fluidity of alloys belonging to these systems. In this work, an analysis of the solidification process of pure Sn, binary SnAg, SnCu, SnBi, SnZn, SnPb and ternary SnAgCu eutectic alloys was carried out using computer aided-cooling curve analysis and differential scanning calorimetry.Fil: Morando, Carina Noemi. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Fornaro, Osvaldo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Garbellini, Olga. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Palacio, Hugo Anibal. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentin
Sn-Pb solders, particularly Sn-37 %Pb eutectic alloy, have been widely used as low temperature joining alloys for some time. However, the restriction of Pb use in industry has been strongly promoted to protect the environment and establishing a Pb-free solder has become a critical issue and an important task for material engineers. New solders must fulfil several requirements; in particular they must be corrosion resistant. In the present work, the corrosion behaviour of five Pb-free solders was studied in a 0.1 M NaCl aqueous solution by means of polarization measurements (corrosion potential measurements, potentiodynamic polarization curves and linear polarization resistance tests), and compare to that of a conventional Sn-37 %Pb solder alloy and pure Sn. The results show that the Sn-3.5 %Ag-0.9 %Cu, Sn-3.5 %Ag and Sn-0.7 %Cu solders have the best resistance to localized as well as to general corrosion, similar to that obtained for the Sn-37 %Pb solder and pure Sn. The Sn-57 %Bi solder has poorer corrosion properties but its behaviour is still acceptable, because it passivates and shows a relatively low corrosion rate. In all these cases the corrosion resistance is good due to the content of noble elements (Ag, Cu, Pb and Bi) in the alloys. On the other hand, the Sn-9 %Zn is definitely the one that exhibits the worst behaviour, not only to localize but also to general corrosion, due to the addition of a less noble material to the Sn matrix.
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