Development of a microwave sintered TiO2 reinforced Sn–0.7wt%Cu–0.05wt%Ni alloy

• Microwave sintered composite solder sample fabrication processes were discussed.
• Effects of sintering on thermal properties of composite solders were studied.
• Effects of sintering on hardness and density of composite solders were studied.
• Microstructure characterization of microwave sintered samples was detailed.
• A hypothesis of improved thermal and mechanical properties of solders is discussed.

The use of reinforcing nano-size ceramic particulates is a promising method to improve the mechanical and thermal properties of lead-free solder materials. In addition, advanced fabrication processes routes such as microwave sintering powder metallurgy (PM) enhance properties in the fabrication of composite solders. To elucidate the mechanisms underlying the improvements in mechanical and thermal properties, Sn–Cu–Ni with TiO2 nano-composite additions, fabricated via a microwave sintering PM method, were investigated using state-of-the-art characterization techniques. Synchrotron micro-X-ray fluorescence (XRF) results detected trace Ti in the solder matrix. This was consistent with X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) results which indicated that nano crystals were within the Sn matrix. It is possible these nano crystal form due to the migration of Ti during the rapid high energy microwave heating. A hypothesis of improved thermal and mechanical properties of nano-composite solders is discussed based on the results and the microwave sintering PM route was discussed as a promising method for next generation lead-free solder processing.