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The purpose of this paper was to determine the complex permittivity of bismuth strontium manganites (Bi_1−xSr_xMnO₃) in the 8‐12 GHz range by using perturbation of Ag thick film microstrip ring resonator (MSRR) due to superstrate of both bulk and thick film.

The BSM ceramics were synthesized by simple low cost solid state reaction method and their fritless thick films were fabricated by screen printing technique on alumina substrate. A comparison has been made between the X band response of Ag thick film microstrip ring resonator due to perturbation of bulk and thick film Bi_1−xSr_xMnO₃ ceramic.

The bulk and thick film superstrate decreases the resonance frequency of MSRR. In this technique even minor change in the properties of superstrate material changes the MSRR response. Variation of strontium content also influences microwave conductivity and penetration depth of bulk and thick films.

The microwave complex permittivity decreases with increase in Sr content in bismuth manganite and it is higher for bulk as compared to its thick films. The superstrate on Ag thick film microstrip ring resonator is an efficient tool capable of detecting the composition dependent changes in microwave properties of ceramic bulk and thick films.

The Benelux chapter has made a habit of organising meetings with a scientific and commercial accent more or less alternately. This approach has proven to be successful in the past three years. The 1986 Autumn meeting will be another display meeting. A number of papers will be presented by suppliers of materials and equipment for the hybrid and surface mounting industry. In a 300 m2 exhibition room about 25 companies will display their products. The programme of the day leaves ample opportunity for meeting colleagues and suppliers. The meeting will be held in the ‘Jaarbeurs Vergadercentrum’ in Utrecht on 16 October from 9.30–17.00. The annual ISHM‐Benelux general membership meeting will precede the lectures.

This paper aims to study the structural, electrical and microwave properties of (Sr_0.6Ca_0.4) (Co_yMn_1−y) O₃ (0.2 ≤ y ≤ 1.0) thick-film ceramics.

The thick films of (Sr_0.6Ca_0.4) (Co_yMn_1−y) O₃ (0.2 ≤ y ≤ 1.0) on the alumina substrate have been delineated using screen printing technique. The structural analysis was carried out using an X-ray diffraction method and scanning electron microscopy. The direct current (DC) electrical resistivity is measured using a two-probe method. Microwave absorption was studied in the 8-18 GHz frequency range by using the Waveguide Reflectometer Method. The permittivity and permeability in the 8-18 GHz frequency range were measured by using Voltage Standing Wave Ratio slotted section method.

The thick films have orthorhombic perovskite structure with dominant (020) plane. By using first-principle calculation method, theoretical and experimental lattice parameter and cell volume of (Sr_0.6Ca_0.4) (Co_yMn_1−y) O₃ are matched with each other. The cobalt content changes the morphology from plates to needles. The DC electrical resistivity increases with increase in Co content and decreases with increase in temperature. (Sr_0.6Ca_0.4) (Co_yMn_1−y) O₃ thick film shows 75 per cent microwave absorption both in the X band and Ku band. The microwave permittivity and permeability decreases with increase in frequency and Co content.

Structural, electrical and microwave properties of (Sr_0.6Ca_0.4) (Co_yMn_1−y) O₃ (0.2 ≤ y ≤ 1.0). Thick film ceramics on alumina substrate is reported for the first time.

This paper presents the results of an investigation into alternative substrate materials to alumina and the associated techniques necessary to utilise them in microwave integrated circuits (MICs). The major driving force for this work was to reduce MIC processing costs without significantly degrading the RF performance. Different glass ceramic systems were assessed and 6–18 GHz gain modules were produced on the most promising of these materials. One glass ceramic material, CMA6, with a dielectric content of 6 • 4, showed a comparable measured gain to that obtained for alumina circuits between 6 and 15 GHz. Cost analysis indicated that, with the reductions in material costs and yield improvements on using glass ceramic substrates, a cost saving of approximately 12% per module is feasible.

The purpose of this paper is to describe the use of copper‐substituted nickel manganite thick film and bulk ceramic superstrate on Ag thick film microstrip straight resonator (MSR), to modify its response and measure complex permittivity as a function of copper.

The glass frit free (fritless) copper‐substituted nickel manganite thick films were formulated on alumina substrate by screen printing technique from the powder synthesized by oxalic precursor method. A comparison has been made between the X band response of Ag thick film MSR due to perturbation of bulk and thick film Ni_(1−x)Cu_xMn₂O₄ (0≤x≤1) ceramic. The shift has been used to measure the permittivity of the ceramic. The dielectric constants obtained by superstrate technique on Ag thick film microstrip component are comparable to those obtained from theoretical calculations.

The resonance frequency of MSR shifts towards lower frequency due to the presence of Ni_(1−x)Cu_xMn₂O₄ (0≤x≤1) ceramic as superstrate. The dielectric constant of bulk and thick film match well with the theoretical values. The dielectric constant increases with copper concentration and shows reduction of power gain of MSR. The peak output (power gain) of MSR due to thick film NiMn₂O₄ increases by 10.19 per cent with decrease in bandwidth and increase in the quality factor with copper concentration.

The superstrate on Ag thick film straight resonator is an efficient tool capable of detecting the composition‐dependent changes in microwave properties of ceramic thick films. These Ni_(1−x)Cu_xMn₂O₄ ceramic being thermistor materials apart from modifying the response can also be used as power sensors providing cost‐effective miniaturization.

This paper aims to report on fabrication procedure and presents microstructure and dielectric behaviour of LiZn_0.92Cu_0.08PO₄ ceramic material with Li₂CO₃ as a sintering aid.

Substrates based on LiZn_0.92Cu_0.08PO₄ with Li₂CO₃ addition were prepared via solid-state synthesis, doping, milling, pressing and sintering. Characterization of the composition, microstructure and dielectric properties was performed using X-ray diffractometry, energy dispersive spectroscopy, scanning electron microscopy, impedance spectroscopy in the 100 Hz to 2 MHz range and time-domain spectroscopy in the 0.1–3 THz range.

Doped LiZnPO₄ ceramic, which exhibits a low dielectric constant of 5.9 at 1 THz and low sintering temperature of 800 °C, suitable for low temperature co-fired ceramics (LTCC) technology, was successfully prepared. However, further studies are needed to lower dielectric losses by optimising the doping level, synthesis and sintering conditions.

Search for new low dielectric constant materials applicable in LTCC technology and optimization of processing are essential tasks for developing modern microwave circuits. The dielectric characterization of doped LiZnPO₄ ceramic in the terahertz range, which was performed for the first time, is crucial for potential millimetre-wave applications of this substrate material.

Recent developments in microwave GaAs technology are yielding devices with higher power capabilities and increased levels of integration. The mechanical and thermal properties of GaAs and other microwave materials play a key role in the design and assembly of microwave power circuits. Thermal management is a critical element of microwave power circuit design. Thermal properties of microwave materials are discussed and compared with standard microelectronic materials. Material selection criteria are described. Assembly and packaging techniques also affect the overall performance of the GaAs power circuit. The high operating frequencies of microwave circuits make ordinary circuit elements, such as wire bonds and printed conductors, reactive. In addition, electrical performance criteria, such as high current or low impedance, create unique assembly demands. The successful development of a GaAs‐based microwave product is dependent on careful attention to the material properties and precise assembly methods. Techniques of automated assembly and processing are discussed, with ah eye towards maintaining high quality and reliability.

Packages for multichip modules in military airborne applications must hava some fundamental characteristics: high thermal conductivity, low density, good mechanical properties and a coefficient of thermal expansion nearly equal to that of the microelectronic substrate installed in the package. In many cases, the substrate is alumina with a CTE of 6.5 ppm/°C. Materials such as aluminium, titanium or Kovar fulfil only part of the above requirements. This is critical when large packages are used, such as in electronic warfare systems where modules include wideband RF circuits with large alumina substrates next to dense digital circuits. The solution is then aluminium/ silicon carbide (Al/SiC). The aim of the paper is to present the development and qualification of large packages combining both RF and digital circuitry. The size taken into account in the study is 220 × 220 mm: it covers most of the electronic needs in terms of surface. Various aspects have been analysed from the perspective of the package manufacturer and the end‐user. The interest of Al/SiC is shown by a thermal analysis of a conduction cooled module with different core materials: the reduction in temperature gradient, which for some components reaches 20° C, has a strong effect on the module reliability. The different technological choices, for a first type of packages, are described: an Al/SiC baseplate with an iron‐nickel alloy for the ring and the lid, brazed feedthroughs (within the Al/SiC baseplate) and connectors, surface treatment, ring brazing material, lid welding technique. A second type of packages is also presented: the main difference lies in the interconnections. RF ceramic (HTCC) inserts are introduced in the ring frame. Various RF measurements show the interest of the different package technologies, especially the ceramic inserts with very good results up to 20 GHz.

The purpose of this paper was to investigate the influence of non-uniform temperature distribution inside a box furnace during the firing process on electrical properties of the low-temperature co-fired ceramic (LTCC) materials used in radio frequency (RF)/microwave applications.

The authors studied the change in dielectric constant of two popular LTCC materials (DP 951 and DP 9K7) depending on the position of their samples inside the box furnace. Before firing of the samples, temperature distribution inside the box furnace was determined. The dielectric constant was measured using the method of two microstrip lines.

The findings showed that non-uniform temperature distribution with spatial difference of 6°C can result in 3-4 per cent change of the dielectric constant. It was also found that dielectric constant of the two tested materials shows disparate behavior under the same temperature distribution inside the box furnace.

The dielectric constant of the substrate materials is crucial for RF/microwave applications. Therefore, it was shown that 3-4 per cent deviation in dielectric constant can result in considerable detuning of microwave circuits and antennas.

To the best of the authors’ knowledge, the quantitative description of the impact of temperature distribution inside a box furnace on electrical properties of the LTCC materials has never been published in the open literature. The findings should be helpful when optimizing production process for high yield of reliable LTCC components like filters, baluns and chip antennas.

The low-temperature co-fired ceramics (LTCC) microfluidic-microwave devices fabrication requires careful consideration of two main factors: the accuracy of deposition of conductive paths and the modification needed to the standard process of the LTCC technology. Neither of them are well-described in the literature.

The first part of this paper deals with the individual impact of screen parameters such as aperture, photosensitive emulsion thickness and mounting angle on the precision of the screen-printed conductive paths fabrication. For the quantitative analysis purposes, the design of experiment method with Taguchi orthogonal array and analysis of variance was used. The second part contains the characterization of the complex permittivity measured for different values of LTCC substrates lamination pressure.

It can be concluded, that the combination of aperture, equal to 24 µm, emulsion thickness 20 µm and mounting angle 22.5° ensures the highest quality of printed conductive metallization. Furthermore, the obtained results indicate, that the modification of the lamination pressure does not affect significantly the dielectric parameters of the LTCC substrates.

This paper shows two aspects of the fabrication of the microfluidic-microwave LTCC devices. First, the resolution of the applied metallization is critical in manufacturing high-frequency structures. The obtained experimental results have shown that optimal screen parameters, in terms of conductive pattern quality, can be found. Second, the received outcomes indicate that the changes in the lamination pressure do not affect significantly the electrical parameters of the substrate. Hence, this effect does not need to be taken into account.