Phase Structure, Microstructure and Properties of Ternary Sn-Bi-Ag Solder Alloy

被引：0
作者：
Bai H. [1 ]
Xu F. [1 ]
Sha W. [1 ]
Chen D. [1 ,2 ]
Yan J. [1 ,2 ]
Gan Y. [1 ,2 ]
机构：
[1] College of Materials Science and Engineering, Kunming University of Science and Technology, Kunming
[2] Yunnan Tin Industry Tin Material Co., Ltd., Kunming
来源：
Xiyou Jinshu/Chinese Journal of Rare Metals | 2019年 / 43卷 / 01期
关键词：
Lead-free solder; Sn-Bi-Ag phase diagram; Tensile strength; Wettability;
D O I：
10.13373/j.cnki.cjrm.XY17120010
中图分类号：
学科分类号：
摘要：
In many cases, due to the soldering device was sensitive to temperature, low temperature welding was necessary. The eutectic temperature of Sn-Bi binary alloy was 139 ℃, and it could meet the requirements of low-temperature solder. Though the addition of Bi would make the material brittle, the intermetallic compound Ag3Sn by adding a small amount of Ag could improve brittleness of the alloy. The specimens with 99.95% purity of tin, bismuth and silver were melted in a certain proportion to form a certain shape. The phases, organization, melting point, microstructure, chemical composition, tensile strength and weldability of the samples were measured by X-ray diffraction (XRD), optical microscope (OM), thermal analyzer, scanning electron microscope (SEM), universal material testing machine and solder ability tester. The effects of Bi and Ag on phase composition, microstructure, melting point and weld ability were studied.The cooling and solidification process of SnBiAg three-phase diagram was analyzed. The results showed that the main crystalline phases of SnBiAg alloy were B-Sn phase with BCC structure and Bi phase with rhombic layered structure according to the XRD test. During the cooling and solidification process, the β-Sn phase was precipitated, and the Ag3Sn and Bi phases were subsequently precipitated. With the increase of Bi phase, Sn phase decreased and Ag3Sn phase was basically unchanged. The result was consistent with the phase equilibrium principle, the Sn phase and Bi phase did not change, and Ag3Sn phase increased with the increase of Ag content. As Bi content increased, the melting point decreased slightly, Bi phase changed from strip to lump, and the overall wettability became worse. As the Ag content increased, the segregation of Bi could be reduced, the melting point remained unchanged and the wettability was improved. Finally, the better alloy formula was Sn-38Bi-0.7Ag. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.
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页码：44 / 51
页数：7
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