Fabrication of reliable Cu-Cu joints by low temperature bonding isopropanol stabilized Cu nanoparticles in air

We proposed a novel Cu-Cu bonding approach by low temperature bonding isopropanol (IPA) stabilized Cu nanoparticles (NPs) in air. The synthesized Cu NPs with the diameter size of about 6.5 nm have good anti-oxidative properties, and IPA has low boiling point (160 °C) and reductive ability, providing the favorable conditions for low temperature bonding in air. Consequently, reliable Cu-Cu joints with high strength (>25 MPa) are fabricated after bonding at 250 °C and 275 °C in air, and the bonded Cu NP layers are copper crystals without oxidation. Moreover, the fracture surfaces of Cu-Cu joints also display obvious ductile deformations and sintering characteristics.