Synthesis, characterisation and formation mechanism of Sn-0.75 Cu solder nanoparticles by pulsed wire discharge

Pulsed wire discharge is used to produce Sn-0.75 Cu nanoparticles (NPs) from Sn-0.75 Cu solder wire in argon ambient. The energy stored in the capacitor (W), which is in the multiple of the sublimation energy of the wire, is discharged through the wire at different pressure of argon. All the particles are spherical in shape with minimum mean particle size of about 28 nm. Deposited energy to the wire increases with increase in W and time to melt of the wire after the injection of current reduces with increase in capacitor voltage. XRD shows peaks corresponding to Sn with no presence of Cu for all the cases. EDAX confirms the presence of Cu. Reduction in melting point of NPs with decreasing size is observed with theoretical and DSC study. Reduction in particle size is observed with increasing energy ratio, K (ratio of W to sublimation energy of the wire) and/or decreasing pressure, P of Argon gas; confirmed with experimental measurement of particle size done with transmission electron microscope (TEM) micrographs and, theoretical calculation of activation energy and nucleation rate of NPs formation.