Microscale mechanical properties in sintered copper nanoparticles

Abstract

This study investigates the size-dependent mechanical behavior and deformation mechanisms of sintered copper (Cu) nanoparticles (NPs) through micro-pillar (2–6 μ m diameter) compression tests, scanning electron microscopy (SEM), transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD) analysis and molecular dynamics (MD) simulations. In-situ micro-pillar compression tests reveal a 25.9% reduction in yield strength (812 ±64 MPa to 643 ±47 MPa) with increasing pillar size, attributed to dislocation starvation in smaller pillars and porosity-driven strain localization in larger ones. TKD quantifies dynamic grain refinement (24.9% reduction in grain size) and geometrically necessary dislocation (GND) density escalation (74.8%), driven by stress gradients and grain boundary-mediated plasticity. Nanoindentation-derived elastic modulus (48.3 ±11.1 GPa) exceeds micropillar values (29.5–33.9 GPa), reflecting substrate constraints in bulk testing. Microstructural analysis identifies a transition from shear banding in high-porosity pillars to uniform plasticity in denser systems, mediated by texture evolution (Brass/S components) and Schmid factor redistribution (62% increase in high-slip-activity grains). MD simulations of pressure-sintered Cu NPs elucidate atomic-scale mechanisms: dislocation nucleation at sintering necks, pore collapse-induced strain localization, and grain boundary sliding. These findings establish a multiscale framework linking porosity, grain refinement, and dislocation dynamics to mechanical performance, emphasizing microstructural optimization for enhanced reliability in microelectronic applications. The integration of MD simulations bridges atomic-scale mechanisms to microscale deformation, providing actionable insights for tailoring sintered Cu NPs via reduced porosity and controlled grain boundary architectures.

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