Film coatings as an encapsulation process for polymer electronics

For improved reliability of microelectronics an encapsulation of sensitive structures is crucial, this is true especially for polymer electronics, where oxygen diffusion and water vapour ingress do dramatically influence the electrical performance. For the protection of semiconducting polymers within organic LEDs a glass layer is the method of choice, providing optimized sealing except for the edge areas. Disadvantage of glass as a sealing material is its rigidity and its sensitivity against mechanical stress. For the realization of low cost applications as smart labels / RF ID tags that need to operate within harsh environment also, besides barrier properties also mechanical protection is needed to ensure device functionality. Various approaches are taken to apply such barrier layers, typically CVD/PVD or spin coating are used, to yield thin, homogeneous layers of encapsulants of 1 to 5 µm thickness. For the high speed encapsulation of large areas also lamination is discussed, where multilayer films are applied using temperature and pressure, layer thickness is in the range of 5 to 30 µm. As a further technology, suited for the deposition of low viscosity liquid barrier materials, film coating processes are proposed. Focus of the technology development described is the application of homogeneous coating on large areas. Expected advantage is the contactless application at high speed on large area substrates, especially useful on substrates showing a 3D topography, as present with devices integrating heterogeneous structures as OSC, printed passives or coils. At Fraunhofer IZM film coating equipment has been installed and first evaluations show promising results. With an ORMOCER® material supplied by Fraunhofer ISC a coating of PET films was demonstrated resulting in a homogeneous coating with a minimum thickness below 10 µm.