Phase Equilibria of the Cu-Sn-Ti Ternary System at 450 °C

Abstract

C1990HP is a kind of commercial Cu alloy containing 3.5 wt.% Ti. It has unique mechanical and physical properties. Thus, C1990HP is regarded as a highly promising lead-frame material in electronic packaging. Sn is a base element used for lead-free solders. The knowledge of the Cu-Sn-Ti phase equilibrium plays a crucial role in understanding the interfacial reactions between C1990HP and Sn-based solders, however the phase equilibria information of this system is still lacking. The isothermal section of the Cu-Sn-Ti ternary system at 450 °C was experimentally determined. The phase equilibrium results confirmed the existence of two kinds of ternary compounds τ₁-CuSnTi and τ₂-CuSn₃Ti₅, which are only stable within a narrow composition range. No additional ternary compounds were found. Moreover, the Sn₃Ti₅ and Sn₅Ti₆ binary phases have considerable solubility of Cu. Meanwhile, the isothermal section was found to contain 17 three-phase regions, 33 two-phase regions and 17 single-phase regions.