Markus Eberstein

LTCC glass-ceramic composites for microwave application

Advanced materials of rare earth derived glass and reactive bonded glass-ceramic composites are exceptionally interesting for 1C packaging, radar, antennas and wireless technologies for the next generation of miniature electronic devices. Glass ceramic composites in the system 1:1:4 BaO-Nd 2 O 3 -TiO 2 and modified rare earth glasses based on boron oxide for passive integration in LTCC demonstrate excellent dielectric properties in the middle permittivity F range of 20/70 with high quality factor Q and low temperature coefficient TCf at microwave frequencies. Depending on the glass-ceramic system, concentration, significant processing parameters e.g. powder preparation techniques and sintering of dense composite at temperatures < 900 C were achieved. Dielectric properties were studied by a cavity resonator method at frequencies 1-6 GHz in correlation of the crystalline microstructure. This work was supported by tridimensional modeling systems to estimate dielectric behavior of multiphase glass ceramic composites.

LTCC-Modules with Integrated Ferrite Layers-Strategies for Material Development and Co-Sintering

The integration of passive components (resistors, capacitors, inductors) into LTCC modules is a challenging task in multilayer ceramics technology. We report on multilayer assemblies consisting of ...

Kinetic Modeling of LTCC Shrinkage : Effect of Alumina Content

We studied sintering of LTCC-type glass matrix composites (GMCs) consisting of small glass and alumina particles of equal size. Primarily, crystals act as rigid inclusions, decelerating the densification rate. In later stages, they also dissolve, partially increasing the viscosity. Release of alumina finally induces crystallization of alumosilicates, which enables post-firing stability. To study both effects, two model GMCs were prepared: an α-Al 2 O 3 + barium alumoborosilicate glass (BABS)-GMC, which shows neither significant dissolution nor crystallization, and an α-Al 2 O 3 + calcium alumoborosilicate glass (CABS)-GMC, which dissolves readily and promotes crystallization. The kinetics of shrinkage for both GMC were modeled by utilizing Frenkel theory for the early stage and Mackenzie-Shuttleworth theory for the late stage, assuming that sintering is superimposed by the weighted contributions of triparticle glass-crystal clusters, their random occurrence (ideal mixing), and a shrinkage rate controlled by the GMC effective viscosity. In agreement with modeling, the experimental results showed that the shrinkage rate of BABS-GMC decreases progressively for crystal volume fractions Φ > 0.15. The attainable shrinkage is reduced by up to 8% for Φ = 0.45. For the CABS-GMC with Φ = 0.25, a reduction of Φ to 0.20 was evident due to partial α-Al 2 O 3 dissolution. This effect was found able to increase the sintering temperature by ∼50-60 K.