Thermal Expansion, Electrical Resistivity, and Spreading Area of Sn-Zn-In Alloys

Abstract

Thermal expansion and electrical resistivity of alloys based on Sn-Zn eutectic with 0.5, 1.0, 1.5, and 4.0 wt.% additions of In were studied. Thermal expansion measurements were performed using thermomechanical analysis tester over 223-373 K temperature range. Electrical resistivity measurements were performed with four-probe method over 298-423 K temperature range. The electrical resistivity of alloys increases linearly with temperature and concentration of In; also coefficient of thermal expansion of the studied alloys increases with In concentration. Scanning electron microscopy revealed simple eutectic microstructure with In dissolved in Sn-rich matrix. The results obtained were compared with the available literature data. Spreading tests on Cu of Sn-8.8Zn alloys with 0.5, 1.0, and 1.5 at.% of In were performed. Wetting tests were performed at 250°C, by sessile drop method, by means of flux, and wetting times were 3, 8, 15, 30, and 60 min. In general, no clear effect of wetting time on spreading was observed.

Effect of Indium Additions on the Formation of Interfacial Intermetallic Phases and the Wettability at Sn-Zn-In/Cu Interfaces

“…For the alloys in the present study, the wetting angle seems to be practically independent of wetting time. Similarly, we earlier [15] observed, with the use of the same flux as in this study, that the spreading area does not increase over time. Figure 1(a), based on the example of an alloy containing 1.5% of In, illustrates that the spreading area increases with increasing temperature…”

“…For longer wetting times, the thickness of the -Cu 5 Zn 8 phase continues to increase, while -CuZn 4 in the case of Sn-Zn/Cu couples begins to disappear and grows very little in the case of Sn-Zn-1.5% In/Cu couples. Moreover, just 0.5% of In is sufficient to keep the -CuZn 4 stable even after 60 min of wetting (Figures 6 and 7), as we observed earlier [15]. The bright spots between the -CuZn 4 and -Cu 5 Zn 8 in Figure 6 are, according to EDS analysis, composed mostly of Sn with In content somewhat higher than the In content in the Sn-Zn-In solder.…”

“…Earlier [15], we found that the spreading area increases with In content over a relatively short wetting time, but for longer wetting times this effect was absent.…”

“…The addition of indium may lower the melting temperature of solders but also improve the wettability and durability of solder joints [12]. We earlier investigated the effect of indium addition on the properties of soldered joints: Cu/SnAgCu + In [13], Ni/Sn-Zn + In [14], and to some extent Cu/Sn-Zn + In [15,16]. In the case of Cu/SnAgCu + In [13], it was found that the Cu 6 Sn 5 was formed at the solder/Cu interface for solders with low In concentration, whereas for high In concentrations it was the Cu 41 In 11 phase that developed.…”

Effect of Cu Addition to Zn-12Al Alloy on Thermal Properties and Wettability on Cu and Al Substrates

“…Kang et al [12] observed a similar effect of increased electrical resistivity with the addition of Cu in alloys. The Zn-Al-Cu solder exhibited an electrical resistivity of 5.5 to 7.0 lX cm at room temperature, which was lower than that of the Sn-37Pb solder (14.25 lX cm [18] ). The obtained electrical resistivity and CTE for ZnAl with Cu are similar to those for ZnAl with Ag, [6] which were 24.03, 25.27, and 29.75 cm 3 /mol for 0.5, 1.0, and 1.5 pct Ag, respectively.…”