| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 97 === The lead-free stannum system is mainly applied in the electronic packaging industry. The ductility is decreased when the excessive Zn and Bi content is assed in the Sn-Zn binary alloys, and low ductility is detrimental to the electronic seal industry. The influence of high Zn and Bi elements content is still unknown. However, the low ductility property may be available in manufacturing precision casting wax molding mold. In this study, the influence of high Zn and Bi content in Sn-xZn (x = 14, 17, 20, 23, 26 wt.%) binary alloys system, Sn-9Zn-11Bi and Sn-yZn-zBi (y = 20, 23, 26 wt.%, z = 8, 11 wt.%) ternary alloys system on microstructures, coagulation behaviors, electric conduction, chip breaking and the stretching mechanical property are investigated. Because the thermal conduction and the electric conduction are similarly in metals, this research measures the electric conductivity to estimate the thermal conduction.
The experimental results show that the Zn-rich area fraction is increased, whereas the ductility is decreased with Zn content in the Sn-xZn binary alloys system. There is no obvious influence on the tensile strength. The liquid-solid coexistence interval and the melting point of high Zn content specimens is better than the low Zn content specimens.
The Zn-rich area fraction is increased, whereas the melting point and the ductility are decreased with increasing Bi content in the Sn-yZn-zBi trinary alloys system. There is no more obvious influence on the elongation, electric conduction and tensile strength when increasing more Bi content. But the tensile strength is decreased with adding excessively Bi content in the Sn-26Zn-xBi system.
The Zn-rich area rate, chip breaking property, and tensile strength are increased with increasing Zn content in the Sn-yZn-zBi trinary alloys system. Because the ductility of all the Sn-yZn-zBi alloys below 4%, it has no obvious influence on ductility. It should be noted that the ductility is zero for the low Zn-content, high Bi-content of Sn-9Zn-11Bi alloy. It has no obvious influence on the liquid-solid coexistence interval and melting point, but the melting point is decreased with increasing Zn content in Sn-yZn-11Bi system.
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