Inkjet printing of multi-layered, via-free conductive coils for inductive sensing applications

A new fabrication technique based on the combined printing of Ag-nanoparticles and dielectric material was developed. The processing, composed of inkjet printing and intense pulsed light sintering/curing, enables a fast, controllable and highly-adaptable structuring of 3D conductor/insulator structures on various types of substrates including ones with low-temperature stability and flexible ones. With this process the classical vias of the multi-layer structure are replaced by a direct connection between the layers achieved by an absence of insulation material at designated areas providing a fast and efficient method for multilayer prototyping. For testing and demonstration a multilayer planar coil structure was fabricated with an overall thickness of 30 µm on the PET substrate. The electromagnetic properties of the structures were successfully tested and verified by comparing several experiments to finite element method simulations. The theoretical simulations show an excellent match with experimental measurements of several structures thus giving confidence in the reliability of the proposed process.