Tibor Rovensky

Influence of various multilayer LTCC systems on dielectric properties’ stability in GHz frequency range

Purpose The purpose of this paper is to create multilayer substrate (composite) from various low temperature co-fired ceramic (LTCC) substrates by their mutual combinations and to analyse influence of these multilayer substrates on dielectric properties in GHz frequency range. Design/methodology/approach GreenTape 951, GreenTape 9K7 and Murata LFC were used to create compound multilayer substrates that include three layers: middle layer is from Murata LFC, and both upper and bottom layers are either from GreenTape 951 or GreenTape 9K7. Shrinkage in all x-, y- and z-axes of all substrates including multilayer substrates were analysed, and influence of different shrinkage on dielectric properties was examined by microstrip ring resonators applied on all mentioned of substrates. Findings The middle layer of Murata LFC has significant influence on shrinkage value of composites which has a good repeatability and minimalizes problems with design of multilayer LTCC devices. Impact of middle layer from Murata LFC on dielectric constant is not significant, but on the other hand Q factor (loss tangent) of these composites is increased according to inhomogeneity between single LTCC layers, especially at frequency around 6 GHz. Originality/value The novelty of this work lies in creating multilayers systems from different types of LTCC substrates to find combination with the most suitable physical and dielectric properties for various purposes in GHz range applications.

Impact analysis of LTCC materials on microstrip filters’ behaviour up to 13 GHz

Purpose – The purpose of this paper is to consider the adequacy of various microstrip filters’ behaviour based on different low-temperature co-fired ceramic (LTCC) dielectrics in the high frequency (HF) area up to 13 GHz. Design/methodology/approach – Low pass, band pass and band stop filters for ultra-wideband radar systems were designed, simulated, fabricated and measured using three various dielectric substrates: Dupont GreenTape 951, Dupont GreenTape 9K7 and Murata LFC. Findings – It is not possible to unambiguously determine the most suitable LTCC dielectric for these filter design because, in general, all designed filters fulfilled requirements (attenuation, cut off frequencies) with minimal divergences, but temperature-stable dielectric and physical properties of Murata LFC make them a promising ceramic for HF application (repeatability of realised experiments). Originality/value – The novelty of this work lies in unconventional usage of LTCC as material with defined dielectric properties proper fo...

Influence of firing profile on microstructural and dielectric properties of LTCC substrates

Purpose The purpose of this paper is to analyse the influence of various firing profiles on microstructural and dielectric properties of low-temperature, co-fired ceramic (LTCC) substrates in a GHz frequency range. According these analyses, sintering process can be controlled and modified to achieve better performance of devices fabricated from LTCC substrates. Design/methodology/approach Samples from LTCC substrates GreenTape 951 and GreenTape 9K7 were sintered by four firing profiles. Basic firing profile recommended by the manufacturer was modified by increasing the peak temperature or the dwell time at the peak temperature. The influence of firing profile on microstructural properties was analysed according to measurements by X-ray diffractometer (application of the Cu K-alpha radiation and the Bragg-Brentano method), and the influence on dielectric properties (dielectric constant and dielectric losses) was analysed according to measurements by split cylinder resonator method at 9.7 and 12.5 GHz. Findings Rising of the peak temperature or extension of dwell time at this temperature has influence on all analysed properties of LTCC substrates. Size of crystallites can be changed by modification of firing profile as well as microdeformation. In addition, dielectric properties can be changed too by modification of the firing profile. Correlation between microdeformation and dielectric losses was observed. Originality/value The novelty of this work lies in finding the mutual relationship between changes in microstructural (size of grains and microdeformation) and dielectric properties (dielectric constant and dielectric losses) caused by different firing profiles.

Design of narrow-band 2.4 – 2.5 GHz notch filter using various materials

This paper deals with design, simulation and measurement of narrow-band notch filter from 2.4 GHz to 2.5 GHz using five dielectric materials with various dielectric constants (glass microfiber, ceramic reinforced PTFE, hydrocarbon or epoxy based material). This paper presents filters based on microstrip line structure with half wavelength L - resonators and bandstop characteristic. Various dimensions of each structure were designed due to characteristic of used dielectrics, characterised by dielectric constant εr. The scattering parameters at various frequencies are investigating by modelling this structure with linear network analyses and electromagnetic simulation provides by Ansoft Designer simulating tool from ANSYS and measurement was done by VNA (Vector Network Analyzer). This article presents results of simulation and real measurement of scattering parameters of designed microstrip line structure. This paper refers how used dielectric materials (Rogers RO3003C, Rogers RO4003C, RT/duroid 5880, RT/duroid 6010LM and FR4) influence quality of designed notch filter and which of used material is the most suitable for purpose of high frequency filter using microstrip transmission lines.

Stability of miniaturized non-trimmed thick- and thin-film resistors

Abstract This paper is focused on reliability tests of non-trimmed miniaturized thin-film and thick-film resistors. Thick-film resistors are screen printed by polymer paste on LTCC (Low Temperature Co-fired Ceramic) substrate by two different approaches. Nonstandard precise screen printing process provide tolerance of resistivity less than 5% and thus further trimming is not necessary. OhmegaPly material with Nickel Phosphorous (NiP) metal alloy is used for thin-film resistors fabricated by subtractive process. Miniaturized resistors have dimensions 0.5 × 0.5 mm, and thus 1 square, with thickness 1 μm for thin-film and 20 μm for thick-film resistors. Stability of miniaturized resistors were tested by humidity test, thermal shocks, long-term thermal ageing, direct current stress, current pulses and simulation of soldering process using VPS (Vapour Phase Soldering). Resistivity of resistors is measured by four wire method before and after each set of test and relative change of resistivity is plotted in graphs. Influence of every test on each type of resistor is analysed.

Influence of accelerating ageing on LTCC and PCB substrates' dielectric properties in GHz area

This paper is focused on investigating stability of dielectric properties, dielectric constant and loss tangent, after exposing dielectric materials to accelerated ageing tests. Two types of Low Temperature Co-fire Ceramics (LTCC) substrates and four types of printed circuit boards (PCB) substrates were exposed to temperature loads. DuPont GreenTape 951 and DuPont GreenTape 9K7 represent LTCC substrates and Rogers 3003C, Rogers 4003, Rogers RT/duroid 5880 and Rogers RT/duroid 6010/LM represent PCB substrates. Thermal shock chamber and temperature humidity chambers provided two types of accelerating ageing test, temperature cycling and High Temperature Operation Life (HTOL) tests. Dielectric properties of these LTCC and PCB substrates were measured by combination of Vector Network Analyzer (VNA) and split cylinder resonator. This measuring method provided dielectric properties at two frequencies, which depend on concrete material, the first frequency is around 10 GHz and second about 12.5 GHz. Preliminary results show better stability of LTCC substrates after accelerating ageing test. It is caused by composition of these substrates which minimalizes moisture absorption, because moisture has major impact on degradation of dielectric properties.

A new approach to construction of extended kit for M-Sequence UWB sensor system based on LTCC

Purpose The purpose of this paper is to introduce modified in–phase and quadrature components (I–Q) demodulator based on low temperature co-fired ceramics (LTCC) dielectric substrate GreenTape 951PX for M-Sequence ultra-wide band (UWB) sensor system. Design/methodology/approach Microstrip low pass (LP) and band pass (BP) filters for UWB sensor systems with required properties (for both filters, minimum attenuation is −40dB in stopband, bandwidth of pass band is 6 to 8.5 GHz for BP filter and cutoff frequency is 2.5 GHz for LP filter) were designed, simulated, fabricated and measured using dielectric substrates Du Pont GreenTape 951 PX. The developed microstrip filters were integrated with all parts of I–Q demodulator on one multilayer structure based on LTCC substrate Du Pont GreenTape 951 PX. Findings Both type of microstrip filters integrated in the I– Q demodulator achieved better transmission characteristics in comparison with commercial available filters. It was shown that LTCC technology based on GreenTape 951PX proves good stability in gigahertz frequency and suitability for fabrication of I–Q demodulator with a multilayer approach. Originality/value The novelty of this work lies in substituting commercially available LP and BP filters used in I– Q demodulator by microstrip LP and BP filters with better performance and furthermore the I– Q demodulator is fabricated based on LTCC instead of previously used PCB.

Measuring of dielectric properties by microstrip resonators in the GHz frequency

This paper presents analysis of four different (Rogers RO3003C, Rogers RO4403C, Rogers RT/duroid 5880, Rogers RT/duroid RO6010LM) Printed Circuit Boards (PCB) from the dielectric properties point of view in High Frequency (HF) area. Measuring of dielectric properties is provided by ring resonator and T-resonator. Both resonators are designed by self-created software tool and these microstrip structures are applied on PCB by common etching process. Microstrip resonators are designed to provide numerous data points over a broad frequency range. Fabricated resonators are measured by combination of Vector Network Analyser (VNA) and test probe station. Measured scattering parameters are used as input parameters for calculating dielectric constant and Q factor of measured dielectric substrate. Determined dielectric properties are plotted in graphs in frequency range from 1 GHz to 10 GHz.