Copper ink has been prepared by mixing copper(II) formate and 2-ethyl-1-hexylammonium bicarbonate (EHABC) to overcome some weak points such as aggregation and degradation of copper nano-type ink. Ink was coated on glass substrate and calcined at $110^{circ}C$ to $150^{circ}C$ to generate electrically conductive copper film under two different atmospheres such as nitrogen gas and gaseous mixture of formic acid and methanol. The lowest resistivity of $1.88{mu}{Omega}{cdot}cm$ of copper film was obtained at $150^{circ}C$ in gaseous formic acid condition. The long-term resistivity shows to increase from $1.88{mu}{Omega}{cdot}cm$ to $2.61{mu}{Omega}{cdot}cm$ after one month.