Scientific Events

Sintered copper (Cu) nanoparticles have emerged as a promising substitute for sintered silver (Ag) nanoparticles in power electronics packaging, offering comparable electrical and thermal conductivities, superior mechanical strength, and lower cost. However, the complex interactions between microstructure evolution, interfacial bonding, and mechanical performance during sintering remain insufficiently understood. This research investigates the mechanical behavior, fracture mechanisms, and reliability of sintered Cu nanoparticles through a combination of microscale experiments and multiscale modeling. The studies revealed the anisotropic fracture toughness of sintered Cu nanoparticles, developed an Anand viscoplastic model to describe high-temperature deformation, and quantified interfacial strength while elucidating the effects of oxidation on bonding quality. Furthermore, the influence of particle morphology on mechanical properties was examined using micro-cantilever bending tests and phase-field fracture simulations. Overall, this work advances the understanding of sintered Cu nanoparticles and supports the development of reliable and cost-effective interconnect materials for next-generation power electronics. [more]

Recent studies have shown that the passage of an electric current pulse may both propagate [1,2] and close a crack and heal a metallic material [3]. Specifically, experiments on thin Al foils containing edge cracks have proved that the self-induced electromagnetic forces, spontaneously generated upon passage of an electric current across a crack in a sample, alone could cause crack propagation without melting of the crack tip [1]. The critical current density required for crack propagation reduces in the presence of an external magnetic field [4] as well as mechanical load [5]. On the other hand, if an electric current pulse of large pulse width is passed through an electrically and thermally resistive material, such as stainless steel, containing a short crack, the crack may completely close, and the material can heal through the solid-state diffusion bonding process [3]. Here, we discuss the reasons behind crack propagation upon application of electric current and then explore the mechanics as well as microstructural attributes responsible for a transition from flaw propagation to flaw healing upon passage of an electric current pulse. Furthermore, the recovery of the mechanical properties of the material upon electric current-induced healing will also be discussed. [more]