Solderability and intermetallic compounds formation of Sn-9Zn-xAg lead-free solders wetted on Cu substrate

Abstract

The eutectic Sn-9Zn alloy was doped with Ag (0 wt.%-1 wt.%) to form Sn-9Zn-xAg lead-free solder alloys. The effect of the addition of Ag on the microstructure and solderability of this alloy was investigated and intermetallic compounds (IMCs) formed at the solder/Cu interface were also examined in this study. The results show that, due to the addition of Ag, the microstructure of the solder changes. When the quantity of Ag is lower than 0.3 wt.%, the needle-like Zn-rich phase decreases gradually. However, when the quantity of Ag is 0.5 wt.%-1 wt.%, Ag-Zn intermetallic compounds appear in the solder. In particular, adding 0.3 wt.% Ag improves the wetting behavior due to the better oxidation resistance of the Sn-9Zn solder. The addition of an excessive amount of Ag will deteriorate the wetting property because the glutinosity and fluidity of Sn-9Zn-(0.5, 1)Ag solder decrease. The results also indicate that the addition of Ag to the Sn-Zn solder leads to the precipitation of ε-AgZn 3 from the liquid solder on preformed interfacial intermetallics (Cu 5 Zn 8 ). The peripheral AgZn 3 , nodular on the Cu 5 Zn 8 IMCs layer, is likely to be generated by a peritectic reaction L + γ-Ag 5 Zn 8 → ε-AgZn 3 and the following crystallization of AgZn 3 .

Microstructures and properties of Sn58Bi, Sn35Bi0.3Ag, Sn35Bi1.0Ag solder and solder joints

“…6, the smaller the wetting angle, the better the wetting. With the same atmosphere and flux, the Sn35Bi1.0Ag solder shows the smallest wetting angle among the three solders, the wettability results reveals that with the addition of Ag, the wettability of solders can be improved obviously, which may be attributed to better oxidation-resistance of Ag, the enhancement on wettability can also be found in Sn9Zn solders bearing Ag [14]. Moreover, comparing with the wettability of these three solders with air atmosphere, with N 2 atmosphere, the wetting angles can be decreased significantly, which demonstrates that the N 2 atmosphere can improve the solderability of solders, which can be attributed to the N 2 can resist the oxidation of molten lead-free solders.…”

Silver(Ag) Improvements on The Structural, Creep Resistance and Electrical Conductivity Properties of Eutectic Sn-9Zn Alloys

“…The addition of an effective secondary step for the creation of Zn-based IMCs (Garcia et al, 2010, Liu et al, 2014 is the eutectic Sn-9Zn alloy. At the same time, Chen et al (Chen et al, 2009) studied the (0, 0.1, 0.3, 0.5, 1wt. percent) Ag-addition reinforcements on the microstructure and mechanical performance behavior of the Sn-9Zn solder alloy.…”