LTCC substrates based on low dielectric permittivity diopside-glass composite

Implementation of LTCC (low temperature coflred ceramics) technology for advanced substrates and packages destined for microwave circuits creates several challenges related to proper choice of materials and processing parameters. In this paper, a new low dielectric permittivity material based on a diopside-glass composite was developed, characterized and applied for fabrication of LTCC substrates. For comparison, properties of pure diopside ceramic were also investigated. Heating microscope studies were used for determination of sintering conditions. Microstructure of laminates was examined by optical and scanning electron microscopy. Measurements of dielectric properties carried out in the temperature range from 25 to 150°C at frequencies 100 Hz-2 MHz revealed low dielectric permittivity of the substrates at a level of 7.2-7.9. Analysis of test LTCC structures with screen printed patterns of conductive paths with different width proved good compatibility of the developed material with co-sintered layers made of commercial AgPd pastes.