Effect of particle size in Ni screen printing paste of incompatible polymer binders

Dispersion of nano-sized particles at high solid content has attracted attention in many industrial applications such as printed electronic products. However, the material design and processing heavily depends on experience with little quantitative measure. For fabrication of thinner dielectric layers, Ni size is getting smaller when used as an inner electrode in multilayer chip capacitor (MLCC). In the present study, we investigate the rheological properties and printing performance of the pastes with two different sizes of Ni particles in the same incompatible binder mixtures of ethyl cellulose (EC) and polyvinyl butyral (PVB). The difference in particle size causes different microstructural heterogeneity and highly nonlinear rheological properties upon the external flow field. The printing pattern and the surface profile are also analyzed by confocal images after screen printing. For smaller particle size of Ni, the more heterogeneous microstructure is observed with increasing PVB content, which is evidenced by the screen printing images as well as its rheological behavior. We explain the difference of spatial heterogeneity in terms of different interactions between particle–particle and particle–polymer. This work is believed to contribute to better design of inner electrodes and processing in MLCC manufacturing.