One-Step Fabrication of Al/Sn-Bi Core–Shell Spheres via Phase Separation

• Published in: Journal of electronic materials 2011-12, Vol.40 (12), p.2458-2464
• Main Authors: Dai, R., Zhang, S.G., Li, J.G.
• Format: Article
• Language: English
• Subjects: Alloys; Aluminum; Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Cooling; Cross-disciplinary physics: materials science; rheology; Eccentrics; Electronics; Electronics and Microelectronics; Electronics packaging; Exact sciences and technology; Instrumentation; Liquids; Materials; Materials Science; Methods of nanofabrication; Microelectronic fabrication (materials and surfaces technology); Morphology; Optical and Electronic Materials; Phase separation; Phase transitions; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Soldering; Solid State Physics; Tin
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-011-1779-6

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 (Al 0.345 Bi 0.655 ) 67.8 Sn 32.2 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 (Al 0.345 Bi 0.655 ) 67.8 Sn 32.2 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 (Al 0.345 Bi 0.655 ) 67.8 Sn 32.2 alloy was analyzed and was schematically illustrated.