Sintered Cu nanoparticles (Cu NPs) are promising interconnection materials for high-temperature power electronics, yet how their authentic three-dimensional pore architecture governs microscale deformation remains unclear. Here, synchrotron nano-computed tomography (nano-CT) was combined with in-situ micropillar compression, explicit dynamic elastoplastic finite element analysis, and TEM/TKD characterization to interrogate sintered Cu NPs. The nano-CT voxel size was 45 nm, and the reconstructed volume corresponded to a cylinder 16 µm in diameter and 10 µm in height. The average sectional porosity was 12.44%, with a systematic discrepancy between two-dimensional and three-dimensional porosity quantification. During loading, the porosity decreased to 9.55% while the pore aspect ratio increased from 1.82–2.35. Finite element analysis further showed pronounced pore-adjacent stress/strain localization at the elastic–plastic transition, with local stress and equivalent plastic strain reaching 650 MPa and 1.7 × 10⁻², compared with 250 MPa and 1.1 × 10⁻³ in adjacent regions. The GND density increased by 95.9% at a compressive strain of 26%, linking pore-induced strain gradients to dislocation accumulation. These results quantitatively connect authentic three-dimensional pore architecture, local deformation localization, and dislocation-mediated strengthening in sintered Cu NPs. Highlights Synchrotron nano-CT (45 nm voxel size) reconstructed a 16 × 10 µm cylindrical volume of sintered Cu NPs and resolved the authentic 3D pore network. Sectional porosity was 12.44%, and 2D/3D quantification showed a systematic discrepancy, with porosity decreasing to 9.55% and pore aspect ratio increasing from 1.82 to 2.35 during compression. Pore-adjacent localization was quantified at the elastic–plastic transition, with local stress/PEEQ reaching 650 MPa and 1.7 × 10⁻² versus 250 MPa and 1.1 × 10⁻³ in adjacent regions. A 95.9% increase in GND density at 26% compressive strain links pore-induced strain gradients to dislocation accumulation and strain-gradient-driven strengthening.

Sintered materials have been widely applied, as an alternative to soldering, for power electronics packaging. One key issue for such die-attach material is to characterize the actual porosity, which is difficult to obtain through SEM cross-section analysis. Therefore, in this work, the optimized Quartet Structure Generation Set (QSGS) algorithm was applied to sintered copper joints under various porosity levels to reconstruct 3D porous structures based on 2D SEM images. Firstly, copper joints with varying porosities were fabricated under different sintering conditions. Reconstructed 3D porous copper models were then generated through the QSGS algorithm to match experimental observations, including porosity and pore size. Finite element analysis (FEA) simulations were further conducted to explore the effects of pores on thermal and electrical performance. This work provides a method for accurately predicting the thermoelectric properties of sintered copper joints and insights for optimizing copper sintering in power electronics applications.

While silver-based sintered materials are limited by cost and electromigration, and copper faces challenges with oxidation at high temperatures, Cu-based composite sintering materials offer promising alternative solutions. This review examines recent advances in Cu-based composite sintered materials for die-attach in power electronics packaging, focusing on their mechanical, thermal, electrical properties, and reliability. This review systematically categorizes such compounding strategies, including direct mixing, core-shell structures, and alloying, analyzing the impact on composite properties. Furthermore, the reliability of Cu-based composite sintered joints is evaluated, addressing high-temperature storage, thermal cycling, corrosion, and electrochemical migration. Challenges such as oxidation resistance, process optimization, and cost-effectiveness are discussed, together with future research directions. This work aims to support researchers in advancing Cu-based composite sintering materials research and development, broadening material options for high-temperature power electronics packaging applications.