Low-Temperature and High-Speed Pressure-Assisted Sinter Bonding Using Ag Derived by the Redox Reaction of Ethylene Glycol-Based Ag₂O Paste

To accomplish a high-speed bonding process of dies for the formation of a bondline with mechanical reliability at high temperatures and excellent thermal conductance, pressure-assisted sinter bonding between an Ag-finished die and a substrate was carried out at a low temperature of 200 °C in air using a paste of Ag₂O particles with ethylene glycol (EG) as the solvent. The Ag₂O particles were synthesized as submicrometer-sized particles via a wet process in 5 min. Ag₂O thermally decomposes above 400 °C; however, mixing with EG lowered the reaction temperature of the redox reaction in the paste to 164–195 °C, which enabled sinter bonding, using the reduced Ag around this temperature range. Therefore, bonding under 5 MPa at 200 °C provided sufficient shear strength > 20 MPa after a short bonding time of only 30 s. The increase in bonding time to 3 min transformed the bondline structure into near-full density; however, this did not increase the strength because of insufficient sintering near the upper interface around the edges of the bondline by outgassing during the redox reaction. Graphic Abstract: [Figure not available: see fulltext.].