Morphology-dependent indentation response of pressure-assisted sintered Cu for power electronic packaging

Abstract

Sintered copper (Cu) particles are widely used in catalysis, biomedical devices, energy systems and electronic packaging, yet the role of particle morphology in governing their mechanical response remains insufficiently resolved. Here, we investigate porous sintered Cu produced from monomodal spherical, bimodal spherical and flake-shaped particles by combining nanoindentation, scanning electron microscopy (SEM) and molecular dynamics (MD) simulations. Both spherical and Berkovich indenters were used to interrogate morphology-dependent deformation mechanisms. The bimodal spherical network exhibited the highest elastic modulus, whereas the monomodal spherical network showed the highest indentation yield strength. In contrast, the flake-derived network displayed substantially reduced elastic modulus and strength due to weak through-thickness connectivity. Correlative SEM images and MD simulations reveal morphology-dependent deformation mechanisms: distributed neck plasticity in the monomodal network, hierarchical load sharing between coarse and fine particles in the bimodal network, and anisotropic strain localization along interlamellar interfaces in the flake-derived network. Indenter geometry further modulates the response, with spherical indentation promoting distributed compaction and Berkovich indentation promoting stress concentration at weak interfaces. These findings highlight particle morphology as a critical factor governing the topology-dependent mechanical performance of porous sintered Cu.