In the present study, the influence of single-walled carbon nanotubes (SWCNTs) of 93% purity on the phase formation, microstructural characteristics and mechanical behaviour of conventional solder alloys (63Sn/37Pb and Sn/3.8Ag/0.7Cu) was studied. The composite solder specimens were prepared by mechanical mixing of SWCNTs with solder powders. The homogenous powder mixture was compacted, sintered and extruded at room temperature. The composite solder alloy was characterized by XRD and SEM to identify the phase formation and morphological features. The mechanical properties such as microhardness, tensile strength and percentage elongation of the nanocomposite solders were evaluated as a function of SWCNT addition. The addition of SWCNTs was observed to influence the grain size and interfacial reaction kinetics of solder alloys. This work describes the physical and microstructural properties of the 63Sn-37Pb and Sn-3.8Ag-0.7Cu solder material alloyed with different weight proportions of SWCNTs. In particular, the melting behaviour and mechanical properties of SWCNT-reinforced composite solders are discussed. (c) 2005 Elsevier B.V All rights reserved.