Polymerizable Ceramic Ink System for Thin Inkjet-Printed Dielectric Layers

An innovative ceramic ink system for thin inkjet-printed dielectric layers is presented, with which it is possible to avoid undesired drying effects. This system contains surface-modified Ba_0.6Sr_0.4TiO₃ (BST) particles, a cross-linking agent, and a thermal radical initiator. The polymerization starts immediately after the ink drop contacts the heated substrate and therefore leads to very homogeneous topographies. Since an organic/inorganic composite ink is used, no sintering is needed after printing and thus printing on flexible substrates is possible. A comparison of the printing and drying behavior between modified and nonmodified BST with the described ink system is performed. The successful surface modification is confirmed via X-ray photoelectron spectroscopy (XPS). Topographies of different printed structures are compared by white light interferometry, the occurring polymerization is confirmed by measurements with an oscillatory rheometer, layer thicknesses are determined by scanning electron microscopy (SEM) images, and the capacitance of a printed capacitor is measured via impedance spectroscopy. It is successfully shown that the developed ink system enables the production of thin ceramic layers (<1 μm) with very homogeneous topographies since undesired drying effects can be avoided. The printed dielectric layers on flexible substrates have a high ceramic content and a high permittivity of 40.