Fraunhofer Institute for Mechanics of Materials IWM
Fraunhofer Institute for Mechanics of Materials IWM

Ceramic sheets and multilayer ceramic structures

© Fraunhofer IWM

Tape casting

 

It used to be that numerical simulations for ceramic sheet producers were rarely used to improve the production process. For this reason, the Fraunhofer IWM developed a linked simulation model at the microstructure and tape caster level so that predictions can be made about the ceramic casting process, including the calculation of the particle orientation in the casting slurry and in the resulting product. This allows the process management for tape casting to be optimized for cost efficiency. Waste can be reduced, desired gradients in the particle distribution can be precisely adjusted or the alignment of elongated or platelet-like targeted particles can be improved or avoided – depending on the respective application.

  • Wonisch, A.; Polfer, P.; Kraft, T.; Dellert, A.; Heunisch, A.; Roosen, A.; A comprehensive simulation scheme for tape casting: from flow behavior to anisotropy development, Journal of American Ceramic Society 94/7 (2011) 2053-2060 Link
  • Fu, Z.; Polver, P.; Kraft, T.; Roosen, A.; Three-dimensional shrinkage behavior of green tapes derived from spherical-shaped powders: Experimentical studies and numerical simulations; Journal of the European Ceramic Society 35 (2015) 2413–2425  Link

© Fraunhofer IWM

Predictions of distortion due to sintering in multilayer ceramic structures

 

Ceramic multilayer structures are the basis for a wide variety of applications such as sensors or microelectronic circuits. Several ceramic sheets printed with varying precious metal pastes are stacked on top of one another, laminated and sintered together. One recurring problem is component distortion, which evolves during sintering due to varying degrees of shrinkage of the different materials. Through the application of detailed sinter models and simulations at the Fraunhofer IWM, foundations have been developed so that unwanted warping can be minimized through targeted material and design improvements - even in difficult cases of complex, imprinted multilayer composites.

  • Schmidt, I.; Kraft, T.; Simulation of the co-sintering of composite structures, International journal materials research 101/8 (2010) 933-941 Link

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© Fraunhofer IWM

Reducing structural widths for screen printing of ceramic multi-layer circuits

 

Ceramic multi-layer circuit carriers are found in microwave circuits, pacemakers, sensors and WLAN units, as well as in several other industrial applications. The fine conductive tracks are applied to the circuit boards via screen printing. A metal paste containing fine aluminum or silver particles is printed through a template corresponding to the desired form on the surface and afterwards sintered together with the ceramic foil using relatively low temperatures. At the Fraunhofer IWM, simulation models have been developed and are in use that provide full descriptions of the paste’s flow behavior during the screen printing process. Detailed studies show that hydrophobic coatings on the underside of the screen greatly improve paste detachment while a separate coating of the top side of the screen is not required. This facilitates the development of appropriately coated screens and adapted, matching pastes by the industrial partner, leading to a reduction of structure widths from approx. 80 µm to 20 µm.

  • Schwanke, D.; Pohlner, J.; Wonisch, A.; Kraft, T.; Geng, J.; Enhancement of fine line print resolution due to coating of screen fabrics, Journal of Microelectronics and Electronic Packaging 6(1) (2009) 13-19 Link

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