Abstract: Soldering process was performed by wetting test machine ST50. The microstructures of Sn-9Zn-3Bi/Cu joint were investigated under 170℃ thermal exposure conditions. The results show that a continuous single layer of Cu5Zn8 intermetallic compound appears when aging within 200h and three layers are formed after aging for 500h and 1000h. From the Cu substrate, they are Cu-Sn layer, Cu-Zn layer, Sn-Cu layer, respectively. The total intermetallic compound layers thicken while the thickness of Cu-Zn compound layer decreases with increasing exposure time. It indicates that the Cu-Zn compounds are not stable during long-term aging.
Microstructures of Sn-9Zn-3Bi solder/Cu joint during long-term aging at 170 ℃
Abstract:
Soldering process was performed by wetting test machine ST50. The microstructures of Sn-9Zn-3Bi/Cu joint were investigated under 170 ℃ thermal exposure conditions. The results show that a continuous single layer of Cu5Zn8 intermetallic compound appears when aging within 200 h and three layers are formed after aging for 500 h and 1 000 h. From the Cu substrate, they are Cu-Sn layer, Cu-Zn layer, Sn-Cu layer, respectively. The total intermetallic compound layers thicken while the thickness of Cu-Zn compound layer decreases with increasing exposure time. It indicates that the Cu-Zn compounds are not stable during long-term aging.
图1 Sn-9Zn-3Bi/Cu接头 在250 ℃下钎焊30 s后的微观结构 Fig.2 Microstructure of interface between Sn-9Zn-3Bi solder and Cu substrate after soldering at 250 ℃ for 30 s
图2 Sn-9Zn-3Bi/Cu接头在250 ℃下 钎焊30 s后的EPMA线扫描分析 Fig.2 EPMA line analysis of Sn-9Zn-3Bi/Cu joint after soldering at 250 ℃ for 30 s (a)—EPMA line analysis of Cu, Sn; (b)—EPMA line analysis of Zn, O, Bi
图3 Sn-9Zn-3Bi/Cu接头在170 ℃下时效后的微观结构 Fig.3 Microstructures of Sn-9Zn-3Bi/ Cu joint after aging at 170 ℃ for different durations (a)—100 h; (b)—200 h; (c)—500 h; (d)—1 000 h (1—Cu-Sn; 2—Cu-Zn; 3—Sn-Cu)
图4 Sn-9Zn-3Bi/Cu接头在170 ℃下时效1000 h的EPMA面扫描分析 Fig.4 EPMA mapping analysis of Sn-9Zn-3Bi/Cu joint after aging at 170 ℃ for 1 000 h (a)—Morphology; (b)—Cu; (c)—Sn; (d)—Zn (1—Cu-Sn; 2—Cu-Zn; 3—Sn-Cu)
表1 Sn-9Zn-3Bi/Cu接头在170 ℃下时效1 000 h后的电子探针元素分析 Table 1 EPMA element analysis of Sn-9Zn-3Bi/Cu joint aging at 170 ℃ for 1000 h
图6 Sn-Zn-Bi/Cu接头时效1 000 h后 界面处元素的等点浓度分布 Fig.6 Element concentration profiles of Sn-9Zn-3Bi/Cu joint interface after aging for 1 000 h along constant trace