Characteristics of Zn-Al-Cu Alloys for High Temperature Solder Application

Melting range, microstructure, mechanical properties and spreadabililty of Zn-(4∼6 mass%)Al-(1∼6 mass%)Cu alloys were investigated. Liquidus temperature was targeted between 655 and 675 K, and solidus temperature was targeted to 645 K. The liquidus temperature of the Zn-Al-Cu solders increased with Cu contents, but it decreased with Al contents. Microstructures of the Zn-Al-Cu solders consisted of primary ε-phase (CuZn4), η-phase (Zn matrix), α-η eutectic phase (Zn-Al eutectic) and ε-η eutectic phase (Zn-Cu eutectic), irrespective of the Al and Cu contents. Increasing the Al and Cu contents, hardness and tensile strength increased, but elongation decreased. The Al content played an important role in improving the spread ratio, the Cu content had no significant influence on the spread ratio.