Microstructure and Mechanical Properties of Sn-8.55Zn-1Ag-XAl Solder Alloys

Abstract

The microstructure and mechanical properties of as cast lead-free solders including eutectic Sn-9Zn, Sn-8.55Zn-1Ag and Sn-8.55Zn-1Ag-XAl (X ¼ 0:01$0:45 mass%) alloys were investigated. Microstructures of the Sn-Zn-Ag-XAl alloys consist of AgZn 3 compound, Zn-rich phase, Al-rich segregation and hypoeutectic phase. The addition of Al dramatically improves the 0.2% offset yield stress, Vickers hardness, ultimate tensile stress (UTS) and total tensile strain of the Sn-8.55Zn-1Ag-XAl alloys. The increase in the Al content of the Sn-8.55Zn-1Ag-XAl alloy from 0.01 to 0.45 mass% increases the average yield stress from 49.9 to 54.0 MPa ($47:6 MPa for eutectic Sn-9Zn) and the Vickers hardness from 17.0 to 18.3 Hv ($16:8 Hv for eutectic Sn-9Zn). The average values of UTS of the Sn-8.55Zn-1Ag-XAl alloys with X ¼ 0:01, 0.1, 0.25 and 0.45 mass% Al are 55, 58, 55 and 60 MPa, respectively, while those of the tensile strain are 47%, 52%, 58% and 45%, respectively (52 MPa and 50% for the eutectic Sn-9Zn alloy). Fracture mechanisms of the Sn-8.55Zn-1Ag-XAl alloys are correlated with the Zn-rich phase and Al segregation.

Effects of small additions of Ag, Al, and Ga on the structure and properties of the Sn–9Zn eutectic alloy

“…The fractographs of the Sn-9Zn-0.45Al alloy show large cup and cone fracture size because stress concentration occurred at the grain boundaries or the interface between segregation and the matrix. This result is in agreement with an earlier finding of Cheng and Lin [30]. It believed that the Ag-Zn compound, the Al-rich phase and the grain boundary can all provide the origin for the fracture behavior of the alloys.…”

Microstructural evolution of ɛ-AgZn3 and η-Zn phases in Sn–8.5Zn–0.5Ag–0.01Al–0.1Ga solder during aging treatment

“…The phases Sn (2 1 1), Sn (2 2 0), Zn (0 0 2), Zn (1 0 0), Zn (1 0 1), AgZn 3 (1 0 1) and AgZn 3 (0 0 2) were observed. The diffraction patterns are similar to those of Sn-Zn-Ag-Al alloys [7]. The peak intensity of Zn increases with aging time.…”

“…The research aiming at solving these problems is in need. Small alloying addition of Ag, Al and Ga had been selected to improve the wettability [2][3][4], oxidation resistance [5,6], mechanical properties [7][8][9][10], and lower the melting point [11][12][13] of Sn-Zn solder alloys. * Corresponding author.…”

Thermal and mechanical properties of Sn–Zn–Bi lead-free solder alloys

“…Sn-Zn solders posses several fascinating features such as low cost as well as low reflow temperature of 220 • C. In addition, Sn-9Zn eutectic alloy has a melting temperature (198 • C) close to that of Sn-Pb eutectic alloy (183 • C), and offers better mechanical properties than the conventional Sn-Pb solders [4,5]. In spite of the Zn in Sn-Zn system is easily oxidized to form certain corrosion products (e.g., Zn oxide/hydroxide and ZnCl 2 ) which leads to poor wettability and reduces the reliability of solder joints, certain Sn-Zn composition region can act as a sacrificed anode with a good anticorrosive property for the ferrous base metals [6][7][8][9][10].…”