Retarding the Cu5Zn8 phase fracture at the Sn–9 wt.% Zn/Cu interface

Cu5Zn8 phase was formed at the Sn–9 wt.% Zn/Cu interface after reflow, but this phase fractured very severely during subsequent solid-state annealing. By reducing the cooling rate of the reflow process, a thicker Cu5Zn8 phase was formed and the phase fracture was retarded during subsequent annealing, which retained the integrity of the Cu5Zn8 phase at the interface. The improvement in the Cu5Zn8 phase integrity was attributed to the maintenance of a local equilibrium at the interface.