Physical and Electrical Characteristics of Silver-Copper Nanopaste as Alternative Die-Attach

A silver-copper (Ag-Cu) nanopaste that formulated by mixing Ag and Cu nanoparticles with an organic binder and solvent system for high-temperature die-attach application has been reported. Various weight percent of Cu nanoparticles (20-80 wt%) was loaded in the nanopaste, in order to investigate its effect on physical and electrical properties of the sintered nanopaste at 380 °C without application of external pressure. X-ray diffraction results showed that Ag₉₇Cu₃, Ag₁Cu₉₉, and CuO phases were formed in sintered nanopaste. Porosity of the sintered nanopaste was increased as the loading of Cu increased. A reversed trend has been recorded in the density of the sintered samples. Surface micrographs and topographs were examined by scanning electron microscope and atomic force microscope, respectively. The structural properties obtained from both characterizations were in agreement. Electrical study showed that the sintered nanopaste has electrical conductivity ranging between 2.27×10⁵ and 0.81×10⁵ (Ω-cm)^-1 with a reducing value as the loading of Cu increases. These values, supported by other complementary characterizations results, have demonstrated that this nanopaste is able to be considered as the alternative die-attach material for high-temperature applications.