Conductive adhesives with self-organized silver particles

Common available conductive adhesives are filled with about 70-90 weight percent of silver particles. There is the technical need to lower the filler content for decreasing the viscosity and the pressure to finally decrease the costs for the highly expensive silver. Our approach to decrease the silver content with at the same time similar conductivity was to use nano-sized silver particles with different modified surfaces to obtain self-organized distribution of the silver particles in the liquid adhesive film followed by conventional curing techniques like temperature or UV curing. Through the self-organization, a bridging of the particles should be achieved which gives a similar conductivity as in highly filled commercial adhesives which follows percolation theory. The influence of the surface modification on the strength of the interaction between differently modified silver particles and the distribution in the liquid adhesive was simulated with Dissipative Particle Dynamics (DPD). Surface modification was verified with surface enhanced Raman spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS). The distribution of the silver particles in the cured adhesive film was investigated with scanning electron microscopy (SEM).