Ultrafast Sinter Bonding Between Cu Finishes Under Moderate Compression Using In Situ Derived Ag Formed via Low-Temperature Decomposition of Ag₂O in the Bonding Paste

To accomplish rapid chip attachment and produce a bondline between Cu finishes that provides both high-temperature thermo-mechanical reliability and superior thermal conductance, compression-assisted sinter bonding at 300 ℃ was performed in air through the in situ formation of active Ag atoms by the decomposition of 200 nm Ag₂O during a redox reaction in the bonding paste. The remarkable sinterability of the generated Ag atoms and the effect of the reducing agent, which was added to the paste to remove the oxide layer on the Cu finish, induced extremely rapid sinter bonding between Cu finishes. Accordingly, the bonding under compression of 2 and 5 MPa resulted in a sufficient shear strength exceeding 27.0 MPa with a dense bondline microstructure even after a significantly short bonding time of 30 s. Transmission electron microscopy revealed that the bonding between the bondline and Cu finish was accomplished through the overlapping of Ag and Cu lattices by inter-diffusion of Ag and Cu atoms without the formation of any compound. Therefore, high-speed chip attachment was successfully achieved even for low-cost Cu finishes. Graphical Abstract: [Figure not available: see fulltext.]