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.

With the increased deployment of power modules in demanding conditions, sintering materials, especially composite sintering materials, have raised growing interest due to their cost-effectiveness and suitability. Therefore, this study explores the viability of Cu–Ag composite sintering material, focusing on solvent influence through microstructure and mechanical behavior analysis. Micron-sized particle-based Cu–Ag composite pastes were designed and compared using eight solvents (four epoxy-free and four epoxy-added) based on fluidity and thermal stability. The sintered joints' performance, assessed through shear strength analysis, showed comparable values to pure silver sintering for both epoxy-free and epoxy-added samples. Optimized samples from each solvent system underwent reliability analysis, demonstrating that Cu–Ag joints with epoxy resin exhibited significantly higher shear strength after high-temperature storage and thermal cycling tests. Micromorphology and elemental composition analysis revealed differences in aging mechanisms, primarily attributed to variations in porosity due to oxide formation and pore filling by epoxy resin under different solvent systems. Further nanoindentation characterization of micromechanical properties, including hardness, modulus, and creep properties, during high-temperature aging, established constitutive models for insights into reliability evolution. In conclusion, the optimized epoxy-added Cu–Ag sintered joints proposed in this study demonstrated exceptional reliability and acceptable micromechanical properties, presenting a promising option for high-temperature power packaging.

With the advancement of power electronics, aluminum-clad copper thick bonding wires have garnered attentions due to superior electrical and thermal properties, making them well-suited for high-temperature and high-current applications. However, the impact remains unveiled of whether the growth of intermetallic compounds (IMCs) at the bonding interface presents critical challenges to the reliability of wedge wire bonds. Therefore, it is necessary to investigate the evolution behavior of Cu/Al IMCs in Al-clad copper wires. In this study, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were firstly employed to characterize the phase composition and growth behavior of Cu/Al intermetallic compounds (IMCs) at two distinct interfaces—the bonding interface and the core-shell interface—under various annealing conditions during high-temperature storage (HTS) tests, revealing a parabolic relationship between aging time and IMCs thickness. Subsequently, shear and pull tests of Al-clad copper bond wires were conducted to evaluate the bonding strength under different aging conditions, clarifying the correlation between various failure modes of the bonds and the evolution of IMCs at the bi-interfaces of this novel composite across different aging stages. Additionally, molecular dynamics (MD) simulations were employed to explore the diffusion behavior of Cu and Al atoms. It revealed that polycrystalline structures enhanced the mutual diffusion at the interface, with copper serving as the predominant element in the interdiffusion process. In conclusion, this study integrates experimental and numerical approaches to elucidate the growth mechanisms of Cu/Al intermetallic compounds and their effects on reliability, providing valuable guidance for optimizing the performance of composite bonding wires in high-temperature power device applications.

Copper sintering has gained great attention as a die-attach technology for power electronics because of its potential cost effectiveness and high reliability under harsh working conditions. However, the mechanism of how the intrinsic pores within such sintered joints influence the thermal and electrical properties still needs further investigation. The evolution of pores within such sintered joints is difficult for in-situ observation during the sintering process and reliability tests, while the porosity level greatly affects the thermal and electrical properties. In this work, four two-dimensional (2D) models with various random pore structures were established based on the Quartet Structure Generation Set (QSGS) algorithm. Then, finite element method (FEM) simulations were conducted to simulate the heat and current conduction in the sintered materials. Subsequently, the distribution of temperature as well as the electric potential in the porous sintered materials were further discussed. Lastly, both the thermal and the electrical conductivities were calculated, followed by a concluded parabolic relationship of thermal and electrical conductivities with the porosity. These findings offer insights into optimizing and predicting copper sintered joint performance and accelerate the wide application of copper sintering.