Effect of dispersant on the dispersion stability and film formation of Ni paste in Multi-layered ceramic capacitor

Abstract

MLCC is one of the condensers used electronic devices. It stores electricity and supplies stable electricity to an electric circuit. Recently the miniaturization of electronic components is strongly required to increase the packaging density as the integration and microminiaturization of electronic devices. Therefore scores of nano particle is used in MLCC process. Ni paste including nano particle is coated to form thin film and is followed by drying process. It is not easy to disperse nano particle and severe coating defects such as crack, curl, delamination, and deformation appear after drying process. These affect fatally final products. To control these types of coating defects, it is important to understand the microstructure of fluid as well as drying behavior because industrial coating fluid is complex fluid system containing particles, binders, additives, solvent and dispersant etc. In these components, dispersant can affect the microstructure of fluid and drying behavior even with small amount. Two types of paste showed different film uniformity after drying just changing 1wt% dispersant type. Furthermore dispersion stability and drying development showed reverse behavior. In order to analyze this phenomenon, in this study, we investigate the effect of dispersant on the dispersion stability and film formation. Four Ni paste and eight model suspensions including different dispersant types and particle types were prepared. We characterized the dispersion stability of fluid by observing sedimentation behavior and measuring rheological properties and adsorbed amount of dispersant. Furthermore drying behavior was characterized by measuring drying stress development. As a result, we understood mechanism of the phenomenon through analyzing relationship between dispersion stability, adsorption and drying stress.