Zn-Al-Mg-Ga alloys as Pb-free solder for die-attaching use

Zn-based alloys have been investigated to replace Pb-5% Sn solder for die-attaching use. We have found that a Zn-4%Al-3%Mg-3%Ga alloy has a 300 °C solidus and a 347 °C liquidus. A die-attaching test was done with preforms of this alloy, Ag-plated lead-frames, and Au-plated dummy dies. Good die-attaching with a small amount of voids can be achieved at 320 °C or higher. In subsequent reliability tests, no failure was observed until 1000 cycles between -65 °C and 150 °C or until 1000 h at 85 °C and 85% humidity. Although the poor workability and poor ability of stress relaxation at room temperature of this alloy may somewhat limit its application areas, this solder is the first Pb-free solder for die-attaching use to our knowledge.