Development of Pb-free Solder Alloys and Their Cast Products

采用OCC（热模连铸技术）工艺和OSC工艺对无铅钎料合金进行了国际联合研究。OCC工艺是一种单向凝固方法，它允许产生具有单向凝固组织的单晶材料或铸造产品。OCC工艺制备的铋锌单晶线由于生长取向的不同，在变形过程中表现出各向异性。解理角大于60度的金属丝基本上没有延展性。另一方面，当解理角小于50度时，线材表现出显著的伸长行为。有可能改善材料的机械性能，改变凝固组织，允许进一步的变形加工。以OCC铸线为原料，采用槽形轧制变形法制备了Sn-Bi共晶合金焊料细丝。研究还发现，OCC工艺对于制备凝固过程中容易偏析的合金是一种有吸引力的方法。这些发现表明，OCC工艺可用于生产低温无铅焊丝，否则使用传统方法（如铸锭铸造或常规铸造，然后进行轧制和拉伸或挤压）难以生产。

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.