Recently, the sintered nanoparticle has received an attention as a replacement for high temperature lead-based solder in the electronic device packaging due to its great thermal conductivity, mechanical properties and high melting temperature. However, there are still some problems such as controlling the thickness and the formation of unexpected voids caused by evaporation of solvent. In this study, nanoporous Cu (NPC) bonding process was developed to achieve a Cu-Cu bonding without solvent and flux. NPC sheet was fabricated by dealloying from cold-rolled Mn-Cu precursor. The effect of bonding temperatures (200–400 °C), pressure (2.5–20 MPa), and atmospheres (N2 and formic acid) on the joint strength of NPC bonding was investigated. The bonding mechanism was investigated by fracture surface of NPC bonding, as well as cross-sectional sample. These results revealed that the NPC bonding was closely related with the oxide layer formed on the NPC surface due to the interruption of diffusion between NPC and substrate.