High-Speed Thermo-Compression Sinter-Bonding Properties in Air of a Paste Containing Dendritic Cu Particles Having Oxalate Skins

To enhance the sinter-bonding speed of Cu dendrite particle-based paste, the particles were surface-treated with oxalic acid solution. This treatment transitioned the particle surface from an oxide layer to a CuC 2 O 4 phase, which suppressed the oxidation of Cu until thermal decomposition between 284-315 °C generating Cu nanoparticles. Using the surface-treated Cu dendrite particle-based paste, sinter bonding at 320 °C under 5 MPa pressure in air provided a sufficient shear strength of 23.4 MPa in just 60 s, reaching the maximum of 28.7 MPa after 180 s. The in situ generated Cu nanoparticles from the thermal decomposition of CuC₂O₄ directly contributed to the very rapid sintering-bonding behavior at 320 °C. However, the bondings at 300 °C and 350 °C showed poorer bonding characteristics than that of before treatment, indicating that the surface treatment strategy for forming CuC₂O4 skins is effectively implemented by appropriately setting the following sinter-bonding temperature.