Employing metal nanoparticles in the soldering process is currently in the focus of research for prospective applications in the next generation of miniaturized electronic devices. The benefits gained from the addition of nanosized metallic inclusions, such as improved mechanical reliability with respect to time and temperature, are well in line with a major interest in the development of improved solder joint components. The main research activity is focused on nanocomposite lead-free solder pastes, which consist of microsized solder powder, flux, and some amount of nanosized metallic inclusions. The behavior of metal nanoparticles in the bulk solder as well as their effect on the microstructure and properties of the produced solder joints are relatively well established. However, there is only little information on the problem that a significant amount of these nanosized inclusions is removed from the solder joint together with the flux during the reflow process. It should also be noted that the high chemical activity of metal nanoparticles and existing special guidelines for their safe handling and disposal essentially complicate a possible industrial application of SAC nanopowders or nanocomposite solders.

The present research is focused on two main strategies. The first strategy is to replace commonly used metal nanoparticles in the soldering process by nanoparticles with a metal core and an oxide shell. This outer shell should prevent an immediate oxidation of the metal in air. The second strategy is to produce solder joints by using fluxes doped with various amount of nanoparticles together with a lead-free Sn-Ag-Cu solder foil. It is expected that the flux doped with metal nanoparticles can be successfully used to cause in-situ targeted alloying at the solder/substrate interface. It has been shown in the literature that the effects obtained by nanosized additions are strongly dependent on the type of nanoparticles employed. There are strong indications that the rejection of nanosized metallic inclusions by the liquid solder during reflow could play a crucial role. Therefore, the behavior of various metal nanoparticles with oxide shell in flux will be investigated. Finally, the mechanical reliability of produced hybrid solder/doped flux/substrate joints will be investigated with respect to time, temperature, and high current density. The obtained experimental results will be compared with data obtained by Finite Element Analysis (FEM). This project will provide essential information for a deeper understanding and for possible advanced simulations of processes in materials with metal nanoparticle inclusions during reflow, as well as it will provide a link between the features of the employed nano-structured components, the reflow process and the mechanical reliability of the end product.