Pressureless low-temperature sintering of plasma activated Ag nanoparticles for high-power device packaging

[Display omitted] •Controllable O2 plasma activation method was proposed to reduce organics on Ag NPs.•Effective activation depth of plasma and optimum process parameters were revealed.•Robust bonding joints with lower porosity were fabricated by O2 plasma activation.•Shear strength and thermal conductivity of the joints were significantly improved.•O2 plasma activation method can provide driving force for pre-sintering of NPs. A controllable plasma-activated method to achieve pressureless sintering of Ag nanoparticles is proposed for low-temperature bonding. O2 plasma activation is employed to effectively decompose organics coated on the nanoparticles prior to sintering, avoiding the loose interfacial microstructures. Therefore, robust bonding Cu-Cu joints with high shear strength (>20 MPa) can be formed at a low temperature of 200 °C without requiring additional pressure. This rapid and controllable activation method significantly enhances the sinterability of the Ag particles, leading to a dense microstructure. The improved thermal conductivity is three times higher than the one prepared without plasma activation.