Materials for inductive and microwave function integration in LTCC-technology multichip modules

Low Temperature cofired ceramics technology (LTCC) receives considerable industrial interest as a multichip module integration technology, particularly because its very good performance-cost combination. The integration potential of the LTCC technology will be significantly extended with the availability of LTCC-compatible low firing magnetic materials that will enable the integration of high frequency inductive functions. In this article the preparation of low firing cobalt containing hexagonal ferrite materials of the Z-structure (Ba₃Co₂Fe₂₄O₄₁, or Co-Z) is described using a PbO-WO₃ eutectic mixture as liquid phase sintering additive. Layers from the previous materials are prepared by the slip-casting technique and cofired with commercially available, low dielectric constant, LTCC tapes. Crack free multilayer structures are achieved after firing at 950-1000°C.