Tailoring microstructure and mechanical properties of sintered Cu nanoparticles
Leiming Du, Gerald J.K. Schaffar, Weiping Jiao, Kai Liu, René H. Poelma, Verena Maier‐Kiener, Jiajie Fan, Daniel Kiener, W.D. van Driel, Xuejun Fan, Guoqi Zhang
Abstract
This study investigates the microstructure evolution and mechanical behavior of bimodal-sized sintered copper (Cu) nanoparticles (NPs) under varying sintering pressures. Micro-pillar compression tests reveal a transition from collapse-dominated to compaction-driven deformation as sintering pressure increases. Transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD) analyses identify a two-stage deformation mechanism—initial pore compaction followed by intragranular slip—fundamentally distinct from bulk Cu. Molecular dynamics (MD) simulations further reveal that large particles promote dislocation-mediated plasticity by accommodating intragranular slip, while small particles enhance load transfer through localized shear-compaction, together enabling uniform strain distribution and supporting the experimentally observed strain accommodation. The resulting microstructure achieves a combination of high yield strength (up to 320 MPa) and low elastic modulus (20 GPa), offering a compliant yet robust response. These findings elucidate a unique processing–structure–property relationship and provide a rational basis for designing porous metal interconnects capable of withstanding thermomechanical stresses in advanced electronic packaging.