Al/Sn-Bi core–shell spheres, which have potential for use in advanced electronic packaging, were fabricated in one step via phase separation by spraying liquid (Al0.345Bi0.655)67.8Sn32.2 alloy into silicone oil. The core–shell spheres changed morphology from three-layer to concentric or eccentric dual-layer type with decreasing melt superheat and increasing oil temperature. The spheres are Al-rich in the core, covered with a Sn-Bi-rich periphery, showing a two-stage melting behavior suitable for electronic packaging. The (Al0.345 Bi0.655)67.8Sn32.2 alloy was identified through thermal analysis to undergo liquid-phase separation, monotectic reaction, and eutectic reaction one after another during cooling. Finally, the solidification path of (Al0.345Bi0.655)67.8 Sn32.2 alloy was analyzed and was schematically illustrated.