Evolution of the Microstructure of Sn58Bi Solder Paste with Sn-3.0Ag-0.5Cu Addition During Isothermal Aging

Journal article (2019)

Authors

Ruisheng Xu Harbin University of Science and Technology
Y. Liu Harbin University of Science and Technology, Electronic Components, Technology and Materials - EEMCS
H. Zhang Harbin University of Science and Technology, Electronic Components, Technology and Materials - EEMCS
Zhao Li Harbin University of Science and Technology
Fenglian Sun Harbin University of Science and Technology
Kouchi Zhang Electronic Components, Technology and Materials - EEMCS
Research Group
Electronic Components, Technology and Materials (EEMCS) (TU Delft)
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Published Date

2019

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Microelectronics

Research Group

Electronic Components, Technology and Materials

Abstract

Eutectic Sn58Bi (SnBi) solder paste mixed with 0 wt.%, 3 wt.%, 5 wt.%, 8 wt.% and 15 wt.% of Sn-3.0Ag-0.5Cu (SAC) paste was prepared by mechanical mixing. The effects of SAC paste additions on the microstructure evolution of SnBi-SAC/Cu composite solder joints during isothermal aging were investigated. The results indicated that the number of large Bi-rich phases decreased and the relative areas of β-Sn increased with increasing SAC content. Moreover, 1-μm Bi-rich particles were found near the Bi-rich phases. During the isothermal aging process, the diameter of the 1-μm Bi-rich particles in the solder bulk increased by about 50% with aging time by Ostwald ripening. The thickness of the interfacial intermetallic compound in all the solder joints increased slightly during the aging process. The formation of Cu6Sn5 was suppressed by the Bi-rich phases above the Cu6Sn5 layer with the aging time increasing. In addition, the solder bulk showed many cracks along the β-Sn grain boundaries after isothermal aging when the content of SAC paste was 5 wt.%. With 8 wt.% or 15 wt.% SAC, fractures were more obvious near the interface than away from the interface.

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