The development trend for diagnostics is reducing the diameter of coaxial signal cables that comprise the probe cable. The thinner super-fine coaxial cable which is offering superior electronic and mechanical properties, such as 75% IACS (International Annealed Copper Standard, electrical conductivity) and 700 ~ 800 MPa in tensile strength has to be developed. Three binary systems, Cu-Ag, Cu-Zr and Ag-Zr were thermodynamically optimized in the present study. Integration of optimized binary phase diagram can give useful information to predict the possible phases for the ternary Cu-Ag-Zr during manufacturing process. The large Cu5Zr particles were found at grain boundaries of as-cast alloys, which results from the strong affinity between Cu and Zr as well as no solubility of Zr in the Cu matrix. This coarse Cu5Zr phase was not dissolved fully during homogenization resides within the microstructure. Therefore, this phase induces decreasing in tensile strength after ageing.