There is a new class of organic/inorganic materials 'midway' between silicone and silica. They consist of a 'cage' of Si and O atoms to which different functional groups and atoms can be added for different properties. One of them apparently has a high affinity for tin and the idea is that if it is added to solder spheres in solder paste, these particles can result in dispersion strengthening of the solder if they can pin the grain boundaries.
Normally, I would expect the particles to float to the top when the solder melted and not remain in the solder. Is there something 'special' about nano-particles (these may be in the 7-500 angstrom range) that would allow them to remain in the melt and perhaps move to the grain boundaries during solidification?