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|Pressure Sintering of LTCC-Modules with Integrated Ferrite Layers|
|Keywords: Ferrite, Pressure Sintering, LTCC|
|Combining materials with different shrinkage characteristics in Low Temperature Co-Fired Ceramic (LTCC) laminates results in constrained sintering conditions. Lateral shrinkage is restricted and vertical shrinkage is increased to reach complete densification. In Glass Ceramic Composites (GCC) viscous rearrangement of crystalline particles in the viscous glassy phase counterbalances the restriction of only one shrinking direction. Complete densification is possible provided that the materials contain sufficient glassy phase. Low-sintering ferrite materials contain only small additive concentrations of typically less than 1 wt% to meet the requirements of high permeability. Complete densification can be reached at 900°C in a free sintering process. Contrary to glass-rich GCC, such LTCC compatible ferrite materials are not able to sufficiently densify under constrained conditions; sintering at 900 °C produces incompletely densified and porous materials. Applying pressure during sintering is a promising option to support the shrinkage in vertical direction and to obtain full densification of ferrite materials under constrained conditions. The sintering pressure required for full densification was determined for different ferrite materials in combined ferrite/alumina laminates. Using these sintering conditions combined ferrite/GCC laminates were produced. The resulting microstructures of both ferrite and GCC materials and the magnetic properties of the ferrite were investigated and compared to results of free sintering.|
Federal Institute for Material Research and Testing (BAM)