The low temperature exothermic sintering of formic acid treated Cu nanoparticles for conductive ink

In this study, we present a new simple method using formic acid pretreatment to achieve low temperature sintering of Cu nanoparticles, and the Cu nanoparticles have been successfully prepared with a modified polyol method. For formic acid pretreatment, the spherical Cu nanoparticles with an average size of 30 nm were saturated with a mixed solution of formic acid and absolute ethanol directly. The surface composition analysis indicated that the initial oxide on the surface of Cu nanoparticles was completely removed, and formate was generated as a by-product which could decompose at low temperature. According to the thermal analysis results, it was found that the sintering temperature of Cu nanoparticles with formic acid pretreatment was reduced to 160 °C. And the corresponding microstructures further demonstrated that the emerging small exothermic peak of thermal curve over the temperature range between 120 and 160 °C was caused by the formation of sintering necks. The formic acid treated Cu nanoparticle films sintered at 260 and 320 °C exhibited an electrical resistivity of 6.1 and 3.6 μΩ cm respectively.