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Published online by Cambridge University Press: 10 February 2011
Very fine oxide dispersoids have been incorporated into solder alloys to create a new, improved solder structure with an ultrafine grain size of ˜200 -500 nm and significantly enhanced mechanical properties. The microstructure is seen to be quite stable upon high temperature exposure (e.g.. 120°C), which is attributed to the presence of very fine dispersoid particles which impede grain boundary sliding and dislocation movement. As much as three orders of magnitude reduction in the steady state creep rate has been achieved. The new solders also exhibit improved (4–5 times higher) tensile strength at low strain rates and improved ductility under high strain rate deformation. It is demonstrated that with a dispersion of TiO2 particles, the Pb-Sn eutectic solder with a low melting point of 183°C can be made more creep-resistant than the 80Au-2OSn eutectic solder with a much higher melting point of 278°C. The new creep-resistant solders can be useful for optical or optoelectronic packaging in which the dimensional stability of the assembled structure is essential.