Synergistic enhancement of strength−ductility in Sn1.0Ag0.5Cu composite solder via surface-modified nano-sized ZrO2 and micro-sized T-ZnOw hybrid reinforcements

• A novel SnAgCu composite solder with hybrid nano-ZrO2 and micro-T-ZnOw reinforcements was successfully fabricated via ultrasonic-assisted casting. • Surface modification of reinforcements using pyrolysis method ensured a clean interface with no gaps or new phases, promoting atomic inter-diffusion. • The composite solder exhibited a high proportion of eutectic structures and minimal coarse IMCs, enhancing mechanical properties. • Optimal Zn/Zr molar ratio of 2:3 yielded a 30.5% increase in ultimate tensile strength and 47.4% increase in elongation compared to plain Sn1.0Ag0.5Cu solder.