Process Chain Development for the Realization of Embedded Capacitors Using Polymer-based Nanocomposites Filled with Bimodal Barium Titanate

Polymer based barium titanate composites have the potential for application as active material in embedded capacitors within a modern printed circuit board (PCB) delivering high permittivity values and low loss factors. Polymer-based composites allow for the use of polymer processing techniques, which are compatible to the established PCB-materials and processes. In this work, a process chain, starting with a material optimization of the initially used nano-sized barium titanate, followed by polymer matrix composite (PMC) formation and screen printing as shaping method is presented. Finally the resulting capacitor's characteristic properties are shown. With respect to the optimization of each individual process step, the flow behaviour of the uncured PMC, the shaping process and the resulting dielectric properties were determined extensively. A PMC with a bimodal barium titanate filler load of 74 wt% allowed for a dielectric layer formation via screen printing. After capacitor mounting and PMC curing an initial capacity density of 13.3 pF/mm(2) was achieved. Thermal cycling between -60 degrees C and 80 degrees C caused a decay of capacity density.