Obtenção de substratos dielétricos multicamadas à base de silicato de cálcio com inserções de h-BN via tape casting

Abstract

In recent years, considerable progress in microwave telecommunications, satellite transmission systems and dense microelectronic circuits has resulted in a growing demand for new low dielectric loss materials. Ceramic substrates for these purposes should have low dielectric constant and low dielectric loss under high operating frequencies, in addition to high relative thermal conductivity. In view of this, the objective of the present work was to obtain multilayer calcium silicate ceramic substrates with h-BN insertions (1 wt. %, 3 wt. % and 5 wt. %) conformed by tape casting in order to evaluate their use as high frequency substrates. The viscosity of the ceramic suspensions was analyzed by rheological tests and the green ceramic tapes were subjected to thermogravimetric analysis (ATG). these tapes were laminated in 6 layers and then sintered at three temperatures: 950 ° C, 1000 ° C and 1050 ° C. The Sintered laminates were characterized by X-ray diffraction, Raman spectroscopy, density and porosity, and field emission scanning electron microscopy (SEM-FEG). Finally, dielectric properties of green and sintered laminates were obtained. Reflection peaks concerning wolastonite and cristobalite phases were found in all compositions, as well as a characteristic hexagonal boron nitride peak in compositions containing h-BN, overlapping a characteristic wollastonite peak. Raman spectroscopy confirmed the phases found in X-ray diffraction, with characteristic peaks of the wollastonite, cristobalite and h-BN phases. The high relative apparent porosity values found in all compositions determined the low relative dielectric constant values (between 1.99 and 2.35), In general, the obtained compositions showed low dielectric losses, mainly in the samples containing h-BN, and this was evident in a wide frequency range, from 0.1 GHz to 1.5 GHz. The Compositions containing 3 wt. % and 5 wt. % of h-BN showed dielectric losses in the order of 10-4, thus having great potential for application as high frequency substrates.