The CALPHAD method [1] was used for preliminary phase diagram calculations using thermodynamic database COST 531 [2] optimized for lead-free solders. The preliminary phase diagram cross-sections were respected in alloy preparation so that the compositions of the alloys were in different phase fields. The zinc composition varied approximately from 2 to 20 wt % and antimony from 6 to 75wt%. The alloys were annealed and after that investigated by light microscopy. The compositions of the equilibrated phases were obtained by means of EDX microanalysis. Thermal effects during melting and solidifying were experimentally studied by the DSC technique in the inert atmosphere using the different heating and cooling rates 1-10K/min. The liquidus and solidus were determined. The DSC signal was also simulated by method similar to approach given in literature [3]. The experimental DSC signal of each alloy was compared with a simulated curve. The experimental temperatures of phase transformations were found.