N-heterocyclic carbene–silver complexes: Potential conductive materials for silver pastes in electronic applications

New organosilver complexes, silver(I) tetraalkylbis(benzimidazolidene) halide [1a–3a] and silver(I) dimethyl-N,N′-hexyl(imidazolyl) bromide [4a], were synthesized and incorporated into electroconductive silver pastes. Complex 3a had a 15-fold higher conductivity than conventional silver salt pastes, specifically silver(I) hexanoate, and exhibited a smooth, homogeneous surface after reductive heat-treatment of the silver paste. While the conductivity of silver(I) hexanoate can be increased by up to 33% by the addition of a supporting silver source, such as Ag2O, the conductivity of 3a was markedly decreased by Ag2O treatment. Thus, 3a can be used in silver pastes with moderate conductivity and can reduce the amount of conventional silver supporting materials without loss of electroconductivity.

The new organometallic complex silver(I) tetraallylbis(benzimidazolidene) bromide (3a) was employed as a substitution material for an electroconductive silver paste. It was shown to have 15 times larger conductivity and a smooth homogeneous surface after reductive sintering of the silver paste compared to conventional silver paste materials, e.g. silver carboxylate/Ag2O or nanoparticles of silver salts in solvent media. This feasibility was demonstrated using the conductivity of the silver paste and its SEM image.Figure optionsDownload as PowerPoint slideResearch highlights
► In this study, the new NHC-Ag(I) complexes are synthesized, characterized and used as a substitution material for electroconductive silver paste.
► The complex, 3a has showed the higher conductivty than that of materials such as silver(I) hexanoate or mixture of silver hexanoate/Ag2O in solvent media.
► This experiment has demonstrated feasibility in organometallic silver(I) complexes being applied as electronic materials.