The Microstructure and Mechanical Property of the High Entropy Alloy as a low Temperature Solder

In this paper, we studied the high entropy alloy (HEA) of SnBiInZn as a low temperature solder with a melting point about 80 °C. The microstructure of the HEA solder is very complicated. There are three phases at least in the solder, including Bi-rich phase, Sn-rich phase and InBi phase. The wetting reaction between the solder and Cu substrate was conducted at 100 °C and 120 °C. The wetting angle ranges from 30 to 40 degrees, indicating that the solder has a good wetting ability even at such low soldering temperature. The scallop and finger shape intermetallic compounds were determined to be Cu ₆ Sn ₅ . The thickness measurement of the IMC layer shows that the interfacial reaction rate is very slow. The shear stress ranges from 19 MPa to 28 MPa, which indicates that the solder joint is strong enough for electronic packaging technology.