Enhancing post-bonding oxidation resistance of low-pressure Cu sintered joints via residual reductant retention

Abstract Cu sinter bonding using fine particles is a promising technology for advanced semiconductor packaging requiring enhanced thermal reliability. However, oxidation during the bonding and subsequent high-temperature exposure critically degrades joint integrity. Conventional oxidation mitigation methods employing either high bonding pressures or protective atmospheres present practical limitations for applications. This study demonstrates a low-pressure bonding approach utilizing submicron Cu particles mixed with reducing solvent-based pastes to impart oxidation resistance through the intentional retention of residual solvents in the sintered structure. We systematically investigated the effect of bonding atmosphere (either air or nitrogen) on the post-bonding oxidation resistance during prolonged exposure to ambient air at 250 °C. Joints bonded in air rapidly oxidized, forming continuous Cu 2 O layers accompanied by severe mechanical degradation and a tenfold increase in electrical resistivity. In contrast, joints bonded under nitrogen exhibited remarkable oxidation resistance due to suppressed solvent combustion, resulting in residual solvent preservation within the sintered matrix. Thermal and microstructural analyses confirmed that these retained solvents actively inhibited oxidation during subsequent high-temperature storage. The preserved metallic Cu network ensured sustained mechanical integrity and electrical conduction. This low-pressure approach effectively leverages residual reducing solvents, demonstrating substantial potential for achieving oxidation-resistant Cu sintered joints suitable for highly reliable next-generation semiconductor packages.