Fabrication of Ni electrode films by sintering Ni nanoparticle pastes: Compositional dependence of specific resistance and optimal composition

Ultra-thin nickel films are essential for the internal electrodes of the high density multi-layered ceramic capacitors (MLCCs) used in a variety of electronic devices. In this study, Ni electrode films were fabricated by sintering Ni nanoparticle pastes prepared by mechanically stirring mixtures of Ni nanoparticles (d = 40-150 nm), dispersant, binder, and solvent. Paste compositions were varied by using three solvents, two binders, one dispersant, and different amounts of nickel nanoparticles. In total 36 pastes and electrode films were prepared. The electrode film defects such as voids in films and exfoliation (film loss due to lack of adhesion to substrate) were noted, and film thicknesses and specific resistances (ρ) were measured. Voids were observed in all samples whereas exfoliations were observed only for several samples. Ni electrode film thicknesses and ρ values ranged from 2 to 7 μm and from 10^-5 to 10^-4 Ω cm, respectively, depending on paste composition. Based on considerations of ρ values, an optimal composition was determined. Of the three solvents and two binders used, terpineol and EC produced better quality films with lower ρ values and without exfoliation, suggesting that they are probably the most suitable for fabricating internal electrodes for high density MLCCs.