The formation of Cu-Cu joints by low temperature sintering Cu NPs with copper formate layer and its oxidation enhancement

Highly conductive and robust Cu-Cu jonts are achieved by the low temperature sintering of Cu nanoparticles (Cu NPs) with a formic acid treatment. When sintered at 300 °C, the Cu-Cu joints exhibited a low resistivity of 4.79 µΩ·cm with a shear strength larger than 30 MPa. In addition, unique oxidation-enhancing effect of Cu-Cu joints is discovered in thermal storage experiments. When thermal storage at 50 h, the strength of the joints increases to 39.25 MPa, while the resistivity is only increased by a factor of 5.78. This discovery provides a potential packaging enhancement process for practical application of electronic devices.