Cu-Ag composite pastes consisting of carboxylate-capped Ag nanoparticles, spray-pyrolyzed Ag submicron particles, and copper formate were developed in this study for low-temperature low-pressure bonding. The joints between the Cu, Ni/Au, and Ag finished substrates can be well formed at temperatures as low as 160 °C under a load pressure of 1.6 MPa. The joints with Cu substrates possess 18.0 MPa bonding strength, while those with Ag surface finish could be enhanced to 23.3 MPa. When subject to sintering under 10 MPa at 160 °C, the electrical resistivity of the sintered structure on metal-coated polymeric substrates was around 11~17 μΩ-cm and did not differ too much when subjected to harsh reliability tests such as mechanical bending and thermal cycling tests, as well as electrical current stressing. This low-temperature, low-pressure nanocomposite paste shows great potential as interconnect materials for microelectronics or flexible device assembly.
Keywords: flexible substrate; low temperature bonding; nanocomposite; reliability.