Patent ID: 7169209

Claim:
Metal alloy particles containing substantially no lead, each exhibiting a plurality of different melting points, as measured by differential scanning calorimetry (DSC) and identified as temperatures at which endothermic peaks are observed in the DSC, said plurality of different melting points including an original lowest melting point (a) and a highest melting point, wherein, when the metal alloy particles are subjected to DSC, at least one exothermic peak is observed in the DSC, wherein each of said metal alloy particles exhibits said original lowest melting point (a) at least at a surface portion thereof, wherein, when each metal alloy particle is heated at a temperature equal to or higher than said original lowest melting point (a) to melt at least a surface portion of each metal alloy particle which exhibits said original lowest melting point (a), followed by cooling to room temperature to thereby solidify the melted portion of each metal alloy particle, the resultant solid metal alloy particle having experienced the melting and solidification exhibits an elevated lowest melting point (a′) higher than said original lowest melting point (a), and wherein each metal alloy particle comprises (i) a lowest melting point alloy phase exhibiting said original lowest melting point (a) within the range of from 40 to 250° C., and (ii) a high melting point alloy phase exhibiting a melting point higher than 250° C., said lowest melting point alloy phase (i) being positioned within a distance of 0.2 r from the surface of said particle, wherein r represents the radius of said metal alloy particle.