Mono-sized balls of the eutectic Sn-38w/o Pb alloy were produced by controlling the break-up of a continuous laminar jet into uniform droplets and by rapidly solidifying the droplets in a silicone oil bath. Though other sizes are possible, the process parameters were selected to produce droplets of a fixed diameter between 700 and 800 μm. The use of silicone oil assured fast cooling and minimum droplet merging. The balls showed high sphericity ; narrow size distribution (within ± 5% of the target diameter) ; and a uniform, rapidly solidified microstructure. They also showed uniform re-melting characteristics due to their homogeneous microstructures. The present study suggests that the mono-sized Sn-Pb alloy balls, produced by the Uniform-Droplet Spray (UDS) process, may be applicable to the manufacture of ball grid array (BGA) type multimodule integrated-circuit (IC) packaging.