Ag Sinter Bonding to Si Substrate via Temporal Formation and Decomposition of Ag Carboxylate

This paper demonstrates the in situ sinter bonding of Ag microparticle pastes to a Si substrate via the temporal formation and decomposition of Ag carboxylate on the surface of Ag microparticles. This was proposed via the investigation of Ag sinter bonding using the redox reaction between Ag₂O and ethylene glycol, which achieved a bonding strength above 30 MPa even for the bonding temperature at 220 °C. Thermal analysis was used to identify the product of the redox reaction between Ag₂O and ethylene glycol and determine the bonding temperature because the final reaction facilitates the interfacial sinter bonding with the substrate. Fourier-transform infrared spectroscopy and nuclear magnetic resonance results indicated the in situ formation of Ag salts of carboxylic acids, such as Ag oxalate on the surface of Ag microparticles. Therefore, the sinter bonding process enabled by the in situ formation and subsequent decomposition of these Ag salts was investigated using Ag microparticles and oxalic acid. Observations of the surface and interfacial morphology of the Ag particles after heating revealed the formation of Ag nanoparticles on the surfaces of the microparticles and the formation of sintering necks between the particles. The bonding experiments demonstrated a significant increase in strength with the addition of oxalic acid to the Ag paste due to the enhanced interfacial sinter bonding with the substrate. The in situ formation and decomposition of Ag salts are promising strategies for improving sintered bonds in electronic devices because they can provide enhanced localized sinter bonding using stable insert materials.