Abstract:
Effect of Ni content on melting point and microstructure of Sn-8Sb-4Cu-
xNi (
x=0, 0.5, 1 and 2, mass fraction) solders were investigated. 304 stainless steel were joined by Sn-8Sb-4Cu-
xNi solders, and interfacial microstructure and shearing property of the solder joints were analyzed. The results showed that all of the Sn-8Sb-4Cu-
xNi with different Ni content are near eutectic solders, with a melting point of 245 ℃. The microstructure of Sn-8Sb-4Cu solder was consisted of α phase, Sb
2Sn
3 + Cu
6Sn
5+Sn composite phase and Cu
6(Sn,Sb)
5 phase. After the addition of Ni, the bulk Cu
6(Sn,Sb)
5 transformed into fine and uniformly distributed (Cu,Ni)
6(Sn,Sb)
5. When Ni content was less than 1%, the amount of composite phase and (Cu,Ni)
6(Sn,Sb)
5 phase increased with the increasing of Ni content. When Ni content increased to 2%, the amount of composite phase and (Cu,Ni)
6(Sn,Sb)
5 phase decreased with the increasing of Ni content, however, Ni content in the (Cu,Ni)
6(Sn,Sb)
5 phase increases to be comparable to Cu. A diffusion layer with a thickness of about 1.5 μm formed at the Sn-8Sb-4Cu-
xNi/304 interface, which was identified to be Fe
2Sn by EDS. Only Cu
6Sn
5 type intermetallic compounds formed in the solders of 304/Sn-8Sb-4Cu-
xNi/304 joints. The addition of Ni element improved the shear strength of 304/Sn-8Sb-4Cu-
xNi/304 brazed joints, and the maximum shear strength of 67 MPa was achieved when the Ni content was 0.5%, which was 60% higher compared to the Ni-free brazing material. The shear fracture locations of all joints were located in the soldering seam.