Atomic insights into the sintering behaviour of Ag–Cu solid solution nanoparticles on Ag substrate

In electronic packaging industry, it has been reported that compared with nano silver and nano copper, the complementation and coordination of Ag and Cu components enable bimetallic nanomaterials enhanced anti-electromigration and oxidation inhibition characteristics. Ag–Cu solid solution nanoparticles (ACDS NPs) has become an emerging substitution and garnered widespread attention. This research presents the investigation into the size-dependent melting behaviour of ACDS NPs and the effect of elevated temperature during the pressure-free sintering with Ag substrate through molecular dynamics simulations. The melting points of ACDS NPs turn out to be in accordance with Gibbs Thomson equation, based on which the suitable sintering temperatures have been determined within 473 and 773 K. As demonstrated by dynamic trajectories at cross section while sintering, coalescence between NPs occurs with the atomic surface diffusion at the sintering neck along the vacancy concentration gradient. 623 K is estimated to be a threshold temperature of complete integration of NPs at which the crystallographic structure collapses during sintering and recrystallizes at the late sintering stage. The dominant sintering mechanisms transferred from surface diffusion and dislocation-based plastic deformation below 573 K to atomic diffusion above 623 K. Furthermore, the results present incontrovertible dominance of Shockley dislocations and interaction energy on determining mechanical properties of sintered atomistic system. It is also revealed that the systems sintered below 673 K yield significantly lower thermal conductivity attributing to the strong localization of heat carriers for intrinsic amorphous structure than crystalline counterparts above 723 K.