Modification and simulation of dielectric properties of glass/crystal phase-composites for LTCC-applications

摘要

Glass/crystal phase-composites (GCC) (also known as glass ceramic composites) for wiring carriers in microelectronics have been developed on the basis of Low Temperature Co-fired Ceramics (LTCC). Integration of microwave filters for mobile applications (f = 0,5...3 GHz) into multilayer LTCC-substrates leads to special requirements concerning substrate materials, especially with respect to their permittivities and dielectric losses. These properties vary strongly with the phase composition, determined by the sintering parameters. Software for calculating permittivity and dielectric loss according to the Effective-Medium-Theory (EMT) and the Effective-Field-Theory, better known as Maxwell-Garnett-Approach (MGA), of multiple phase materials is introduced. Applications on the base of CCC from 22La{sub}2O{sub}3-45B{sub}2O{sub}3-33TiO{sub}2 - glass and crystalline BaLa{sub}2Ti{sub}4O{sub}12 are demonstrated. The simulation of dielectric properties of the CCC from these initial phases coincides with the results from respective measurements. Sintering at elevated temperatures leads to phase transformations causing the appearance of more than two phases in the materials. In that case the type and the volume fractions of the resulting phases are necessary for the calculation of the dielectric properties. The needed parameters for the calculations have been made by means of a combination of appropriate methods, like XRD, REM and stoichometric calculations starting from the known chemical composition. The software presented extends the analytic capabilities for clarifying the phase composition of multiple phase CCC.