Development of Pb-free Solder Alloys and Their Cast Products

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The international joint research was done for the purpose of the lead-free solder alloy using the OCC (heated-mold continuous casting technique) process and the OSC process.The OCC process is a unidirectional solidification method, which permits the generation of single crystal materials or cast products with a unidirectionally solidified structure. Bismuth and Zinc single crystal wires produce by OCC process, exhibited anisotropy during deformation due to differences in growth orientation. Wires with cleavage angles greater than about 60 degree exhibit essentially zero ductility. On the other hand, wires with cleavage angles less than about 50 degree, exhibited remarkable elongation behavior. It is possible to improve the mechanical property of materials altering the solidification structure, permitting further deformation processing. For example, Sn-Bi eutectic alloy solder thin wire was fabricated by grooved rolling deformation process from the OCC cast wires. It was also found, the OCC process was an attractive atractive for the manufacture of alloys, which are prone to segregation during solidification.These findings suggest that the OCC process could be useful for the production of low-temperature lead-free solder wires which are otherwise difficult to produce using conventional methods such as ingot casting or conventional casting followed by rolling and drawing or extrusion.