Study on Microstructure Control and Mechanism of Al-60wt%Sn Alloy Particles Fabricated by Pulsated Orifice Ejection Method

Advanced electronic packaging imposes high demands on core-shell solder balls, creating an urgent need for new preparation technologies. The pulsated orifice ejection method (POEM) offers particles with uniform size, high sphericity, and consistent thermal history, enabling flexible control of the microstructure through process parameters. In this study, POEM was used to prepare Al-60wt%Sn alloy particles by varying the melt superheat and particle size. By combining SEM, EDS, and DSC analysis with calculations of the cooling rate and internal temperature gradient of the droplets, a window diagram correlating melt superheat, droplet size, and particle microstructure was established. The results indicate that melt superheat and droplet size influence the liquid-liquid phase separation state and the migration behavior of the secondary-phase droplets by affecting the cooling rate and internal temperature gradient of the droplets. When the particle size is 285 and 320 μm, particles with uniform size, centered cores, and a perfect core-shell structure are obtained, meeting the requirements for advanced electronic packaging. This study provides valuable insights into the preparation of monotectic alloy particles with different structures and offers reliable results for understanding the formation mechanisms of core-shell structures in monotectic alloys.