A phenomenological study of a Sn–Ag–Al composite solder reinforced with Mg–MWCNT: Improved electrical conductivity and thermo-physical performance

Abstract A Sn–Ag–Al composite solder alloy reinforced with Mg–multi-walled carbon nanotubes (MWCNT) was prepared using a powder metallurgy (P/M) method. The electrical resistivity of the Sn–Ag–Al–Mg–MWCNT composite solder alloy decreased to 21.91 × 10 − 6  Ω·cm when the Sn–Ag–Al conventional solder alloy (36.15 × 10 − 6  Ω·cm) was reinforced with 2.87 wt% Mg and 0.60 wt% MWCNT (3.47 wt% Mg–MWCNT). The reinforcement by the Mg–MWCNT also provided relatively lower density (6.53 g/cm 3 ) to the composite solder alloy compared to the conventional solder alloy (7.34 g/cm 3 ). The onset melting temperature of the quinary solder alloy was 204.2 °C, which was 10.0 °C lower than that of the ternary solder alloy at 214.2 °C. The wettability of the composite solder powders after reflow on the quartz substrate was increased due to the improved solder fluidity aided by the MWCNT bundle. The improved electrical and thermo-physical performance was induced by a combination of interactions driven by ionic and covalent bonds between the Mg atoms and the MWCNT, and by intermetallic compound formation between the Mg atoms and the other solder constituents.