The composite approach is used to develop particle reinforced brazing filler metals and solders with tailored properties. For some applications the dimension of the particles and/or the brazing gap thickness has to be downscaled. Especially in case of microjoints, nanoparticles offer a possibility to modify the filler properties within a small volume. The experience gained by the development of composite fillers with microsized particles help by designing the nanocomposite fillers. However, a number of aspects have to be considered when downscaling from micro- to nanoparticle composite solders:
- the processing methods resulting in an uniform distribution of microparticles in a filler metal are do not ensure a homogenous distribution of nanoparticles in this filler (are not directly transferable)
- high specific surface area of nanoparticles increases the particle reactivity and may change the chemical composition of the base filler metal,
- even fine reaction layers (e.g. sub microns region) are in case of nanoparticles sufficient to converse them completely into reaction products,
- with the smaller size of particles added the viscosity of the liquid filer metal may increased by agglomerates of the reinforcement particles
- the “reinforcement” mechanisms differ for the micro- and nanosized particles.
Examples from own research are shown to illustrate these aspects.