The global semiconductor industry is projected to become a trillion-dollar industry by 2030. This is historic considering that it took the industry 55 years to reach half a trillion dollars in size and will take just another 10 years to double in size to a trillion dollars. Advanced packaging as it relates to heterogeneous integration will play an important role in making this happen.
Emerging distributed and edge computing applications require unprecedented compute and communications capabilities. Using emerging applications as the primary driver leading to system scaling with power, performance, form-factor, cost, and reliability as the key metrics, integration strategies need to exploit Monolithic 3D (M3D) integration using Back-End-Of-Line (BEOL) integration of sequential silicon and non-silicon materials and devices, Wafer-to-Wafer (W2W) and Die-to-Wafer (D2W) Bonding using BEOL I/Os and Vias for 3D Heterogeneous Integration (HI), and Embedded Dies with 3D connectivity for Heterogeneous Integration. Co-integration of electronics and photonics within the interposer along with optical TSVs becomes necessary to facilitate direct communication to the modulators and photodetectors placed near logic/memory, which can then support the high bandwidth required. Wireless communication at the edge requires supporting large bandwidth, which can be enabled through 6G frequencies in the sub-Terahertz frequency range. This requires integration of high frequency composite materials and III-V semiconductor integrated circuits (IC) into a heterogeneous stack using active interposers with embedded dies and 3D vertical interconnections.
Radically new heterogeneous integration strategies as described require new materials with significantly improved properties as well as new methods for synthesis and integration into complex monolithic 3D and heterogeneously integrated systems. Examples include ultra-low dielectric constant materials, ultra-low loss dielectric materials, thermal interface materials, magnetic materials, thermal insulation materials, heat spreading materials, dry films, liquid materials, 2D materials, low loss optical waveguide materials, and many more, which need to co-exist as part of a vertical stack. This talk will provide details on the current and future material availability and requirements based on a 10-year outlook

BaMg2Al6Si9O30-based ceramics could be synthesized by using the traditional solid reaction methods sintering at 1325 °C–1350 °C for 5 h. The BaAl2Si2O8 and BaMg2Al6Si9O30 phases coexisted in BaMg2Al6Si9O30 ceramic with the raw material of uncalcined MgO, and the BaMg2Al6Si9O30 single-phase ceramic could be obtained by the raw material of calcined MgO due to MgO reacted easily with water vapour in the air to form Mg(OH)2. BaMg2Al6Si9O30 single-phase ceramic exhibited the hexagonal crystal structure with P6/mcc space group and dense microstructure. The BaMg2Al6Si9O30 single-phase ceramic exhibited ultralow εr (5.68 at 14.05 GHz), moderate Q×f value (28534 GHz at 14.05 GHz), and self near-zero τf value (‒7.35 ppm/°C). The ultralow εr (< 6) was attributed to low ionic polarizability of the primitive unit cell, and the Q×f values were closely related to the roundness of [Si4Al(1)2O18] inner rings. The stable and highly symmetrical hexagonal crystal structure with six-membered double-inner rings of [Si/Al(1)O4] tetrahedron caused the self near-zero τf value of BaMg2Al6Si9O30 single-phase ceramic, and the its τf value could be adjusted by controlling the length and strength of Si/Al-O1 bond. Moreover, the near-zero average temperature coefficient of thermal expansion (+1.89 ppm/°C) at 30 °C‒1000 °C and rare negative temperature coefficient of thermal expansion (‒9.43 ppm/°C) at 655 °C‒710 °C were obtained at BaMg2Al6Si9O30 single-phase ceramic. The rare near-zero and negative thermal expansions of the BaMg2Al6Si9O30 single-phase ceramic were mainly related to the strong Si/Al-O bonds with high relative covalency and 2 coordinate O(1) allowing longitudinal vibrations. The study on temperature-stable ultralow-εr BaMg2Al6Si9O30-based ceramics demonstrated the possibility of co-regulating microwave dielectric properties and linear thermal expansion coefficient, which provided a reference for cooperative optimization of microwave dielectric properties and thermal expansion of microwave dielectric ceramics.

Matched termination is an important part of the passive waveguide components. It is typically used at the end of a waveguide transmission line to prevent reflections and improve signal quality. Waveguide terminations (loads) are commonly used in microwave and RF applications. In traditional microwave architectures, usually, waveguide termination consists of a standard rectangular waveguide made by a lossy resistive material, and ended by shorting metallic plate. These types of terminations are used, to dissipate the energy as heat. However, these terminations may increase the size and the weight of the overall system. New alternative solution consists in developing terminations based on 3D-printing of materials. Designing such terminations is very challenging since it should meet the requirements imposed by the system. These requirements include many parameters such as the absorption, the power handling capability in addition to the cost, the size and the weight that have to be minimized. 3D-printing is a shaping process that enables the production of complex geometries. It allows to find best compromise between requirements.
In this paper, a comparison study has been made between different existing and new shapes of waveguide terminations. Indeed, 3D printing of absorbers makes it possible to study not only standard shapes (wedge, pyramid, tongue) but also more complex topologies such as exponential ones. These shapes have been designed and simulated using CST MWS®.
The loads have been printed using the carbon-filled PolyLactic Acid, conductive PLA from ProtoPasta. Since the terminations has been characterized in the X-band (from 8GHz to 12GHz), the rectangular waveguide standard WR-90 has been selected. The classical wedge shape has been used as a reference. First, all loads have been simulated with the same length and two parameters have been compared: the absorption level (level of |S11|) and the dissipated power density. This study shows that the concave exponential pyramidal shape has the better absorption level and the convex exponential pyramidal shape has the better dissipated power density level. These two loads have been printed in order to measure their properties. A good agreement between the simulated and measured reflection coefficient has been obtained. Furthermore, a study of material structuring based on the honeycomb hexagonal structure has been investigated in order to vary the effective properties. In the final paper, the detailed methodology and the simulated and measured results will be presented in order to show how 3D-printing can allow controlling mass, weight, absorption level and power behaviour.

Previously we have demonstrated the ferroelectric to paraelectric transition behavior for the
(Sr2Ta2O7)100-x (La2Ti2O7)x (STLTO) perovskite compounds of compositions x between 0 and 5 in the form of ceramics. These new layered-type perovskite ferroelectrics materials were achieved with the objective to tailor the Curie temperature at ambient temperature. A maximum tunability, of the permittivity under dc bias at room temperature, was found for the composition x = 1.65. With the objective to manufacture miniature microwave agile devices, the next step of our study was then to obtain the STLTO compounds, in particular the composition x = 1.65, in the form of thin films for which the applied bias voltage controlling the tunability can be low due to the thickness of the layers of the order of a few hundred nanometers.
To investigate translating this composition to thin films a homemade oxide target, having the composition STLTO x = 1.65 in solid solution, was produced by a solid-state chemical synthesis route. Films were deposited by reactive magnetron radio-frequency sputtering while varying the deposition conditions and monitoring final composition, structure, phase, and dielectric properties. The films deposited from this target are identified as being tetragonal tungsten bronze type (TTB) compounds, arising when the films are strontium-deficient (ratio Sr/Ta close to 0.5). All films are characterized by moderate permittivities (typically < 100) and low losses (in the range of few 10-3), and this x = 1.65 TTB-STLTO composition is tunable with a (modest) tunability (9 %) at room temperature and low frequency (10 kHz).
Therefore, in an attempt to overcome this Sr deficiency to achieve perovskite STLTO films, another homemade strontium-enriched oxide target has been produced with the composition
(Sr1.4Ta0.6O2.9 )100-x (La2Ti2O7)x, having an initial Sr/Ta ratio of 2.33. Several depositions from this target have been performed. Structural (XRD), morphological (SEM), compositional (EDS) and optical
(UV-Visible transmittance) techniques were used to characterize the films. Finding the films deposited under the current deposition conditions contain multiple phases with Sr/Ta ratios that vary between ~1-1.2, a bandgap energy ~5 eV, and a morphology that varies depending on which substrate the film was deposited. An LCR bridge was used to determine the dielectric properties of the films in lower frequencies (kHz) via Metal-Insulator-Metal structures on conductive Nb:STO substrates. The films exhibit low permittivities between 10-30, with losses 10-1-10-2, low sensitivity to increased temperature, and no tunability with applied bias.

Lithium-ion batteries are widely used in electric vehicles, energy storage plants and portable electronic devices. However, traditional lithium-ion batteries using organic liquid electrolytes have problems such as insufficient energy density and frequent safety accidents, which makes it difficult to meet the growing demand for high-performance batteries. However, lithium-ion batteries using solid electrolytes are expected to fundamentally solve the safety problems of traditional liquid electrolyte batteries. Among them, garnet oxide Li7La3Zr2O12 solid electrolyte has been widely concerned for its wide electrochemical window, good chemical stability and thermal stability. However, problems such as low ionic conductivity at room temperature and high resistance at the contact interface with electrodes hinder the commercialization of this electrolyte, and further improvement is needed.
In this paper, single element, double element doped Li7La3Zr2O12 based solid electrolytes were synthesized by solid phase reaction sintering method. The method and mechanism of electrochemical performance optimization of Li7La3Zr2O12 based electrolytes were explored through element doping.
First, the effects of sintering process (sintering temperature and time) on the structure and properties of Li7-3xGaxLa3Zr2O12(LGxLZO x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) solid electrolytes doped with Ga were investigated systematically. With the increase of x, the phase structure of LGxLZO prefired powder changes from tetragonal to cubic phase, and the phase structure of all LGxLZO ceramics after sintering is cubic phase. Compared with Li7La3Zr2O12 ceramics, the average grain size of LGxLZO ceramics doped with Ga is reduced. The ionic conductivity of LGxLZO ceramics firstly increases and then decreases with the increase of x. When x = 0.25, the ionic conductivity of the ceramics sintered at 1230 ℃ for 4 h reaches the maximum.
Secondly, Ga and Ta co-doped Li6.25-yGaxLa3Zr2-yTayO12(LGLZTyO) solid electrolytes were prepared, and the effects of x = 0.25, y = 0.2, 0.4, 0.6 doping, sintering process (sintering temperature and time) on the properties of LGLZTyO were investigated. The density of ceramics increases with the increase of y, and the relative density of LGLZTyO ceramics reaches the maximum when y = 0.6. The ionic conductivity of LGLZTyO ceramics decreases with y increasing. When y = 0.2, the ionic conductivity of ceramics sintered at 1230 ℃ for 4 h is the highest. Li/ Li6.25-yGa0.25La3Zr2-yTayO12 /Li batteries with the highest separation conductivities were selected, which showed good polarization voltage and more stable cycle than Ga single doped lithium symmetric batteries

0.9BaTiO3–0.1Bi0.5Na0.5TiO3–Nb2O5–MgO (BTBNTNbMg) ceramics were synthesized by solid-state reaction, and the microstructure, bonding and dielectric properties were studied. The results show that all samples retain the characteristics of core-shell structure and have pseudocubic perovskite structure and a small amount of secondary phase at the sintering temperature of 1200°C. The samples are all dense structures with an average grain size of about 500 nm. The 0.9BT–0.1BNTNb20 and 0.9BT–0.1BNTNb40Mg15 ceramics meet EIA X8R specifications at –55°C to 150°C and have the best dielectric properties. For samples doped with Nb2O5 and MgO, as the amount of Nb increases, the dielectric constant decreases, and the dependence of the capacitance change rate on temperature becomes less obvious in the high temperature region. The dielectric constant of 0.9BT–0.1BNTNb40Mg15 at 25°C is 1027 and the dielectric loss is 1.37%, but the dielectric loss increases when the temperature increases.

In this study, we synthesize the Mg4Nb2O9 ceramics by the solid state reaction method with TiO2 additive, in order to study the microwave and structure properties of that mixture. The Mg4Nb2O9 ceramics can transform into Mg5Nb4O15 phase due to additive TiO2, and the Mg5Nb4O15 phase of the samples is increasing with TiO2 additive increasing, which is due to TiO2 dissolving into ceramic and replacing Nb-ion site. The microstructure of samples shows that TiO2 additive can reduce the sintering temperature, improve the grain growth and increase more Mg5Nb4O15 phase. Because the TiO2 additive can be inducing the phase transformation, the Qxf -values of mixture are rapidly decreasing with TiO2 increasing: but the K-values of samples show small fluctuation with TiO2 additive increasing.

Precious metals and oxides were applied to external silver pastes for LTCC applications. Solder wetting property of thick-film electrodes, Ag-Pt < Ag < Ag-Pd < Ag/Pd, is inversely proportional to the upward floating behavior of inorganic binders. Excellent solder leaching resistance of Ag-Pd and Ag/Pd thick-film electrodes (240℃ & 260℃, 180s; 280℃, 90s) is mainly related to the formation of PdSn2 IMC. The growth of IMCs in thick-film electrodes is mainly dominated by volume diffusion (n < 0.5). The growth activation energy of IMCs in thick-films containing Ag/Pd (25.08 kJ/mol) is higher than that in thick-films containing Ag-Pd (16.68 kJ/mol), which slows down the growth of interfacial IMCs and inhibits the leaching of silver in thick-film electrodes. The introduction of oxides, especially CuO additives, can control the flotation of inorganic binders in LTCC external electrode paste, optimize the metal surface state of thick-film conductors, and improve the solderability of thick-film conductors. Moreover, the thick-films can withstand 180 s of soldering at 280℃, with excellent solder leaching resistance, significantly improving the soldering characteristics of thick-film electrodes. This work provides valuable guidance for the design of components in external electrode paste for LTCC applications.

The permittivity of the perovskite dielectric material (Ba,Sr)TiO3 can be adjusted across a wide
range due to cation displacement in a quasi-static electric field. This property makes thin film
metal-insulator-metal (MIM) tunable capacitors, based on (Ba,Sr)TiO3, suitable for various
applications in microwave microelectronics, including phase shifters, delay lines, tunable
resonators, and filters. However, conventional MIM varactors suffer from performance
limitations at frequencies above 1 GHz. The issue lies in the incoherent interface between the
metallic electrode and the dielectric layer, resulting in a polycrystalline defect-rich and lossy
dielectric (Ba,Sr)TiO3 layer. The thickness of this dielectric layer must be thicker than 300 nm
to avoid high leakage currents along grain boundaries. As a consequence, large tuning voltages
of about 20 V are required.
To overcome these limitations, we propose an epitaxial all-oxide varactor as a solution. Our
all-oxide thin film varactors based on (Ba,Sr)TiO3 are grown epitaxially using pulsed laser
deposition, with a highly conducting oxide, SrMoO3, serving as the bottom electrode. This
oxide bottom electrode can be grown beyond several micrometers, effectively reaching the skin
depth at application frequencies of up to 10 GHz. The all-oxide varactors exhibit low losses at
high frequencies (1–3 GHz) and can be effectively tuned at a Li-ion battery voltage of 3.7 V[1].
Notably, a leakage current density, as low as 1 A/m2
, is achieved for a dielectric layer below
50 nm when 1 at. % of Mn doping is used. Moreover, we demonstrate the successful
transferability of our material technology to Si substrates, making our novel concept of alloxide varactors highly relevant for high-performance agile devices, requiring low tuning
voltages and boasting ultra-low power consumption.

Information and communication technologies (ICT) are the foundation of growth and development in the modern global economy. They are striving to bring robust connectivity to all corners of the globe, driving both innovation and ways in which technologies can be used to improve economic and social development towards a smart society. The Microwave Liquid Crystal Technology is a very promising candidate to cope with the demands of reconfigurable systems in a broad frequency range from 30GHz to 300GHz. Besides the improvement of the material itself, the development of new and the optimization of components and systems strongly relies on advanced packaging technologies. The combination of fine-pitch microelectronics and a liquid dielectric pose relevant research questions. The advancements of the microwave liquid crystal (LC) technology is reviewed in this talk. After a brief introduction into the fundamentals, different realizations of packages are discussed in detail. High-performance metallic waveguide phase shifters and low-profile planar delay-line phase shifter stacks are investigated not only for phase shifting performance, but also for system parameters such as phase shifter figure of merit and response times. Here, the very thin planar devices show advantages over bulky waveguide phase shifters at the cost of higher insertion loss. A closer look into application scenarios of LC-based reconfigurable planar antenna systems (a) for terrestrial as well as for non-terrestrial communication and (b) for the application of intelligent reflective surfaces will complement the discussion.

Future radar systems will operate in the mm-wave and sub-terahertz regime to achieve high miniaturization and support range resolutions in the order of 1cm. Sub-terahertz devices require new antenna and packaging technologies supporting upcoming frequency regulations while maintaining low overall system cost. In this paper experimental measurements and three-dimensional electromagnetic simulations are applied to characterize the material properties of glass, antennas on glass and mm-wave interconnects between silicon-based device and glass in D-band. Furthermore, a radar system with glass antennas operating at 120GHz is presented. The achieved results indicate the commercial potential for antennas on glass in sub-terahertz systems.​

For applications such as high-speed transmission, 5G communication, and new optical devices, a substrate that does not absorb moisture, has small CTE, and has less warpage is required. This presentation will show direct wet Cu metallization on Glass TGV (thru-glass via) technology for antenna, RF device, and optical platform solution applications without any PVD seed layer.
It is believed that conformal metallization on glass with the highly conductive thick Cu material is
expected to enhance the performance of RF electronic & optical devices in the IoT era..

TOPICS
- Glass TGV properties
- Glass TGV applications
- Glass TGV strong area
- Glass TGV metallization process
- Direct wet Cu metallization / plating process & performance

Abstract

Multilayer ceramic (MLC) technologies (Low-Temperature Co-fired Ceramics-LTCC and High-Temperature Co-fired Ceramics-HTCC) have decades of success stories in electronic packaging and continued support roles for various applications1. Recently, Ultra-low temperature co-fired ceramic (ULTCC) technologies gaining more and more attractive academic research on materials and applications representing the possibilities of green and circular economic aspects and initiatives. Ultra-low temperature (400-700°C)2,3 beyond HTCC (1000-1600°C) and LTCC (800-950°C) fabrication provide the first step to reducing the energy of production of MLC components. The Ultra-low fabrication concept further increases the recycling possibilities and reaches a circular economic concept to implement resource reuse and non-toxic, cleaner production using fewer resources. Removal of hazardous materials in electronic components; For example, using Pb/Co-based glass in LTCC materials and paste raw materials (RoHS regulations). Herein, presenting a new composition of lithium aluminium silicate-based glass ceramics sintered at 650°C with dense microstructure (average ρ ~ 2.5 g/cm3 and average water absorption ~ 0.7 vol% @ room temperature) and low and tunable coefficient of thermal expansion of about 4.6 ppm/K (average CTE @ 30-400°C). Moreover, the sintered samples show low average relative permittivity of 5.85 and moderate dielectric loss of 0.008 at 13 GHz. Newly developed ULTCC material is initially tested for the integration feasibility with Ag as an electrode by a hybrid approach of ULTCC and Ag particle sintering together and post-XRD analysis. More additional research in the direction of tape casting, conductor paste development and semiconductor integrations will be done at Fraunhofer IKTS together with industrial partners to reach higher Technology Readiness Levels (above 4).

Keywords

HTCC, LTCC, ULTCC, CTE, Relative permittivity, Dielectric loss, MLC, Microstructure, XRD

References
1- J. Varghese, N. Joseph, H. Jantunen, Multilayer glass-ceramics/Ceramic composite substrates, Encyclopedia of Materials: Technical Ceramics and Glasses, Volume 3, 2021, page 437-451.
2- J. Varghese, K. Reinhardt, S. Körner, S. Ziesche and U. Partsch, ULTCC Materials, tapes and pastes firable at 650 °C, iMAPS CICMT 2022-Ceramic Interconnect and Ceramic Microsystems Technologies, Vienna, July 13-15, 2022.
3- J. Varghese, MoO3, PZ29 and TiO2 based ultra-low fabrication temperature glass ceramics for future microelectronic devices, Doctoral thesis C 700, 2019, University of Oulu, Finland.

For decades radomes, and other electromagnetic (EM) structures, have posed challenges to rf engineers stemming in large part from their impedance mismatch to free space. This has introduced design constraints to adapt to environmental, mechanical, structural, and EM conditions. Other applications include antenna efficiency enhancement and EM wave absorption. Here, we report the impedance-engineering of rf magnetoceramics, and their composites, that relieve many of these constraints including that of free-space impedance matching. We process samples through conventional ceramic processing and characterize these using x-ray diffraction, electron microscopy, and vibrating sample magnetometry. Measurement of dispersive properties, i.e., complex permittivity and permeability, using a vector network analyzer. We demonstrate free-space impedance matching in several systems, including magneto-dielectric materials of three types: spinel-based, hexagonal-based, and composite materials, specifically, heavy-ion substituted hexaferrites, low loss Z + Y-type hexaferrite composites, and Co2Z hexaferrite–BaTiO3 composites. We describe here the processing details of how one realizes broadband impedance matching to free space (to within +/-1%) over the VHF and UHF bands. Each of these systems offers enormous potential for many rf applications.

In this paper, dense xNaCl-(1-x)Ni0.5Zn0.5Fe2O4 (Abbreviated as NaCl-NZO), xH3BO3 -(0.8-x)Ni0.5Zn0.5Fe2O4-0.2NaCl (Abbreviated as HB-NZO-NaCl) composites were prepared by cold sintering process as a function of x values, to explore the magnetic and dielectric properties. Among them, the optimal cold sintering conditions were 200℃/30min/500MPa with a relative density of 93% for NaCl-NZO and 120℃/30min/300MPa for HB-NZO-NaCl with a relative density of 95% respectively. No other secondary phases were detected by X-Ray diffraction, scanning electron microscopy, and Raman spectra. 0.5NaCl-0.5NZO composite ceramic exhibited er = 7.8@100 MHz, tan d = 0.05@100 MHz, μ= 3.3@100 MHz, and magnetic tan d = 0.002[KS1] @100 MHz. 0.3HB-0.5NZO-0.2NaCl composite ceramic had er = 5.9@100 MHz, tan d = 0.02@100 MHz, μ= 5.1@100 MHz, and magnetic tan d = 5 × 10-4@100 MHz. It has potential application prospects in 5G communication for the isomagnetic dielectric composite ceramic of 0.3HB-0.5NZO-0.2NaCl as a radio antenna.

Microwave (MW) dielectric ceramics are used in numerous electronic components for modern wireless communication systems, including antennas, resonators, capacitors and filters. However, classic MW ceramics are manufactured by an energy-intensive, high-temperature (> 1000 °C) sintering technology and thus are difficult to co-sinter with low melting point and base metal electrodes and directly integrate with polymers
Cold sintering is able to densify ceramics at < 200 °C via a combination of external pressure and a transient liquid phase, reducing the energy consumed and facilitating greater integration with dissimilar materials. This presentation outlines the mechanism of cold sintering and reports on the development of new materials and progress towards component/device fabrication.
The use of multimaterial 3D printing is also discussed for the developed of integrated devices using low temperature, conventionally sintered ceramics such as silver molybdate as well as polymer-ceramic composites.

The order/disorder transition had been recognized to indicate great effects on improving Q value in Ba(M’1/3M”2/3)O3 microwave dielectric ceramics. In the present work, the concept of ordered domain engineering has been proposed and developed for the synergistic modification of physical properties in Ba(M’1/3M”2/3)O3 complex perovskite ceramics, where three primary parameters - ordering degree, ordered domain size and its distribution, and ordered domain boundary type are optimized through designing and controlling the sintering and post-densification annealing processes. Not only the Q value but also the temperature coefficient of resonant frequency, resistivity, thermal conductivity, dielectric strength and energy storage density could be synergistically modulated in complex perovskite ceramics by the means of ordered domain engineering. Three typical complex perovskites Ba(Mg1/3Nb2/3)O3, Ba(Co1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3, have been investigated as the model materials with the different relation between the densification temperature Ts and order/disorder transition temperature To-d: To-d is much higher than Ts, To-d is close to Ts, and To-d is apparently lower than Ts. The well-ordered structure is expected in the as-sintered Ba(Mg1/3Nb2/3)O3 ceramics, and it is not the case for Ba(Zn1/3Nb2/3)O3 ceramics, and a post-densification annealing process at lower temperature is necessary to effectively improve the ordering degree and obtain uniform ordered structure. While, the well-ordered structure could only be expected for Ba(Co1/3Nb2/3)O3 ceramics by carefully designing and controlling the sintering and post-densification annealing processes. Anywhere, the synergistical modification of physical properties in all these typical complex perovskites could be achieved by ordered domain engineering based on designing and controlling the sintering and post-densification annealing processes.

Today, electromagnetic absorbers for a microwave application are the subject of several studies with the aim of proposing new absorbers that have an increasingly larger operating bandwidth with an increasingly smaller thickness.
In this work, we propose a new flexible absorber material based on silicone foam filled with carbon fibers, and presented in the form of periodic structures. The originality of this proposal lies in the combination of two simple manufacturing concepts: on the one hand, a very simple method of preparing the flexible silicone foam, and on the other hand, the simple periodic structuring of the absorber.
This new absorber can be considered as an organic metamaterial; which allows to overcome the metallization used to make standard metamaterial absorbers. In fact, this metallization is often susceptible to corrosion and represents a limitation for the use of metamaterial. Moreover, our proposed absorber makes it possible to combine the absorption due to the resonant frequencies of the metamaterial, and the dielectric losses of the composite, to obtain a broadband absorber. To do so, a silicone foam, with a density of 0.33 g.cm-3, loaded with 2% of carbon fibers of 12 mm length, was used. After a parametric study of the absorber, using the dielectric properties of the composite, the proposed absorber structure is composed of a continuous layer of the composite with a thickness of 6 mm, associated with parallelepipedal structures (14 x 14 x 10 mm3) deposited on it; the total thickness of the absorber is 16 mm. The simulation of this absorber predicts a reflection coefficient lower than – 10 dB between 4 and 18 GHz, which is confirmed by the measurement, in the anechoic chamber, of the produced absorber. These results confirm the potential of the proposed material and structure for the achievement of a flexible, lightweight and broadband, organic metamaterial absorber.

Beyond 5G (B5G) communication technology requires high-performance devices capable of operating at microwave/mm-wave frequencies and managing massive quantities of data with minimal signal latency. These one-of-a-kind and cutting-edge technologies necessitate the usage of dielectric materials that possess specific properties and functionalities, including low dielectric constant, ultra-low loss (power dissipation), and thermal management capabilities. Polyphase ceramics or hybrid dielectric composites consisting of both inorganic and organic phases are potential materials systems that can fulfill various requirements. Cordierite (Mg2Al4Si5O18) and forsterite (Mg2SiO4) are selected as major inorganic phases based on their limited polarizations and minimal power dissipation at ultra-high frequencies. Polyimides (PI) are employed for ceramic-polymer hybrid materials approach.
Hydrothermally synthesized nanoparticles of cordierite and forsterite were advantageous in the processing of both ceramic-ceramic and ceramic-polymer composites. The fully densified cordierite-forsterite ceramic-ceramic composites were obtained at relatively low temperatures. The post-annealing process allowed for tailoring the dielectric constant and TCF of polyphase composites through phase evolution. Composites of forsterite and polyimide (PI) are also promising substrate materials for 5G/B5G communication devices. In the processing of forsterite-PI low-k, low-loss ceramic-polymer composites, surface engineering for the forsterite nanoparticles played a crucial role in dispersing the high-concentration forsterite nanofillers in the forsterite-PI composites, which had a direct impact on the reduction in loss tangents.

Frequency in wireless communication is increasing with density of communication system. For this reason, generated heat is accumulated in the systems and then it is becoming a serious problem. Silicon nitride is a significantly effective material for its higher thermal conductivity and fracture strength. Aluminum nitride has also higher thermal conductivity. Kume et.al had a discussion about dielectric loss for the aluminum nitride, and its variation by sintering aids was discussed (1)(2). In comparison with aluminum nitride, thermal conductivity of the silicon nitride is lower, but it has a higher fracture strength than aluminum nitride. Therefore, silicon nitride is expected to use as heat dissipation for the active circuit substrate of the wireless communication. In this paper, three type of silicon nitride, which made varying thermal conductivity, were prepared and their thermal conductivities are introduced, in addition, analysis by synchrotron radiation scattering, direct heat conductive measurement, infrared and Raman scattering, and their dielectric properties are referred.

(1)S.Kume et.al, J. Eur. Ceram. Soc. Vol27, (2007), 2967-2971
(2)S. Kume et.al, J. Eur. Ceram. Soc. Vol26, (2006), 1831-1834

5G networks, beginning to come online around the world and providing more connectivity and an ever-increasing number of wireless devices and sensors, requires miniaturized antennas to operate, especially dielectric resonator antennas (DRA) working at about 3.5 GHz. In this work, utilization of dielectric resonator made of tetragonal tungsten bronze (TTB) phase β’-SrTa2O6 ceramics, with both high permittivity and low losses, is explored.

A sintering study of SrTa2O6 ceramics via a pressureless solid-state reactive sintering process is conducted, producing both β- and β’-SrTa2O6 polymorphs. While monitoring phase purity to reduce dielectric losses, the β-SrTa2O6 ceramics obtain relative densities of about 73%, whereas the β’-SrTa2O6 ceramics achieve much higher relative densities approaching 90%. Dielectric characterizations are performed between 3-5 GHz using a resonant cavity, establishing a significant difference in the permittivity of the two polymorphs. β-SrTa2O6 ceramics exhibit relative permittivites around 21-22 and dielectric losses of 7x10-3 or higher. On the other hand, the β’-SrTa2O6 ceramics possess relative permittivities between 80-100, dielectric losses around 4x10-3, and a temperature coefficient of 280 ppm/̊.

Utilizing the measured dielectric properties, the performance of a protype dielectric resonator antenna is modeled via multi-physics software. A β’-SrTa2O6 ceramic resonator is then integrated onto a demonstrator and near-field base measurements are performed. With a resonant frequency of 4.0 GHz, the DRA achieves a bandwidth of 7.1% at -6 dB and a total efficiency of 91%. These measurements provide an excellent match to the modeled antenna validating the measured dielectric properties. The high total efficiency of the β’-SrTa2O6 integrated DRA prototype demonstrates the potential of this material for miniaturized DRA applications.

Future electronic and telecommunication systems must meet stringent requirements in terms of technical performance and reliability but also sustainability and eco-friendliness. The environmental impact associated with petroleum-based polymers used as binders or matrix materials in composites has sparked interest in exploring alternative materials that offer improved sustainability and reduced ecological footprint. Biomaterials, derived from renewable resources, exhibit biodegradability, recyclability and reduced dependence on fossil fuels. By adopting biomaterials as matrix materials in composites, they can contribute to more sustainable manufacturing processes and facilitate the transition towards a greener future.

However, it is crucial for biomaterials to meet various technical characteristics, particularly in terms of feasible electrical properties such as low permittivity and losses for future 5G/6G applications. In this review, we focus on the utilization of biomaterials as eco-friendly matrix materials in composites. We discuss and compare their properties with commonly used polymers, considering their electrical performance and other relevant technical characteristics.

By exploring the use of biomaterials as matrix materials in composites, we aim to highlight their potential as sustainable alternatives and evaluate their suitability for high-frequency applications. This review contributes to the ongoing research and development efforts in utilizing biomaterials for eco-friendly and high-performance composites in the field of electronics and telecommunications.

This paper focuses on improving the shielding properties of graphene-based polymer composites (GBPCs) by uniformly dispersing graphene flakes in the polymer matrix. The shielding properties are evaluated via microwave measurements of sheet resistance and its surface uniformity. An inverted single dielectric resonator (iSiPDR) [1][2] mounted in a two-dimensional (2D) motorized translation stage is applied, with a metal reference plate serving as the sample holder. The scanning procedure involves moving a sample over a grid of points with spatial resolution, here set to 2 mm. Microwave transmission curve is captured at each point of the grid, and resonant frequency and Q-factor are extracted. Changes in these values between an empty and sample-loaded device are used to determine resistivity, surface resistance and conductivity [3] of the GBPC.
A thermoplastic polymer, acrylonitrile-butadiene-styrene (ABS), is used as the matrix of the nanocomposite, while graphene nanoplatelets (GNP) are used as the filler in different loadings: 5, 10 and 15 wt%. The results from four compounding methods are compared, based on [4]:

• Simple dry mixing process via a 3D mixer: Both components in powder form are dryly mixed using a 3D mixing process.
• Twin-screw extrusion mixing process: single crossing: First, a pre-mixture of the materials is prepared using a 3D mixer, which is then fed into a twin-screw extruder. Both components are homogenized in the extruder at the flow temperature, resulting in a filament.
• Twin-screw extrusion mixing process: double-crossing: First, a pre-mixture of the materials is prepared using a 3D mixer, which is then fed into a twin-screw extruder. Both components are homogenized in the extruder at the flow temperature, resulting in a filament. The filament is pelletized. The obtained pellets are fed back into the extruder to obtain another filament, which is then cut into pellets again.
• The solution mixing process involved dissolving the polymer (ABS) using a solvent (acetone) and mixing graphene in the dissolved ABS suspension. The material is then evaporated from the solvent.
Experimental results for a number of large ABS/GNP composites panels (10 cm x 10 cm) will be presented at the conference, demonstrating the effect of the manufacturing process parameters on panel inhomogeneities that can degrade the shielding performance of these materials.

[1] [8] M. Olszewska–Placha et al., 24th Intl. Microwave & Radar Conf. (MIKON), 2022, doi: 10.23919/MIKON54314.2022.9924947.
[2] https://www.innoradar.eu/resultbykeyword/qwed
[3] https://qwed.eu/resonators_sipdr.html
[4] K. Zeranska et al., ACS Applied Electronic Materials 2022, DOI: 10.1021/acsaelm.2c00722

The connectivity of constituting phases plays an important role in the physical properties of composites and porous materials, while it is still overlooked in many cases. In the present work, CaTiO3 is used as the model material to clarify the effect of ceramic connectivity on the microwave dielectric properties of porous ceramics. CaTiO3-A and CaTiO3-B porous ceramics are prepared by partial sintering at 700–1200 oC and sintering at the optimum temperature of 1350 oC with the aid of porogen, respectively. With increasing the sintering temperature from 700 to 1000 oC, the relative density of CaTiO3-A ceramics maintains around 58%, while their er, Qf, and tf increase dramatically (20.4–48.2, 968–4,237 GHz, and 443.9–724.2 ppm/oC). The three parameters are even higher in CaTiO3-B ceramic with a similar relative density of 54.1% (69.1, 5,658 GHz, and 782.9 ppm/oC). The huge variation in microwave dielectric properties is attributed to the significantly improved ceramic connectivity with sintering temperature observed from microstructure analysis. Finite element analysis further reveals that the ceramic connectivity plays the dominant role in the microwave dielectric properties by deciding the electric field distribution in CaTiO3 phase and pores and hence their contribution to dielectric response. The exponent 'a' in exponential dielectric mixing rule is employed to describe the ceramic connectivity, and the trinary relationship among the microwave dielectric properties, constitution, and microstructure of porous ceramics is well constructed. This relationship can be extended to ceramic-polymer and ceramic-ceramic composites, which brings new perspectives for designing such microwave dielectric materials.

The growing demand for increased energy management efficiency has led to the establishment of programs which support research and innovation such as [1][2]. The implementation of the work done in this paper follows the I4Bags [3] project, which focuses on demonstrating the versatility of low-energy ion implantation (LEII) protocols [4] as a tool to locally modify the electronic, electrochemical, and electrical properties of thin-film semiconductor batteries (TFSSBs). One of the goals is to increase the gravimetric capacity and improve their stability. The current research has been carried out on the quantitative and qualitative characterization of graphite cathodes. These cathodes are then subjected to LEII, whereby the solid-electrolyte interphase (SEI) boundary is transformed. The effect of SEI has been studied in the already completed twin project NanoBat [5].

The carbon coatings were produced using magnetron sputtering plasma deposition [6] on quartz wafer, then were implanted by N or Ar multicharged ions, having an energy range from 20 to 40 keV. The fluence range was from 5E15 to 1E17 ions/cm2. Measurement of the thickness of those carbon layers was performed by mechanical profilometers, and the results are on the order of several hundred nm. This is essential information for obtaining sheet resistance with the resonant methods we used: including 5 GHz single-post dielectric resonator (SiPDR) and 10 GHz inverted SiPDR (iSiPDR), where the measurement procedure is described in [7] and [8], respectively. LEII is then performed on the sample-under-test (SUT). As a consequence, we observe a decrease in sheet resistance of 1 or 2 orders of magnitude after implantation.

Two-dimensional maps of the sheet resistance and conductivity will be presented at the conference. They will be discussed depending on the thickness of the deposited carbon and before and after the LEII performed with selected ions. To validate the results obtained, they will be compared for three different measurement methods: fast 4-point electrical measurements, 5 GHz SiPDR, and 10 GHz scanner iSiPDR. By utilizing LEII's potential for modification, TFSSB has a chance to revolutionize various industries promoting a green and efficient future.

[1] https://research-and-innovation.ec.europa.eu/funding/funding-opportunities/funding-programmes-and-open-calls/horizon-2020_en
[2] https://www.m-era.net
[3] https://qwed.eu/i4bags.html
[4] https://www.ionics-group.com/en
[5] L. Nowicki et al., 24th Intl. Microwave & Radar Conf. (MIKON), 2022, doi: 10.23919/MIKON54314.2022.9924916
[6] https://www.materianova.be/en/technology/processes/dry-surface-treatment/vacuum-plasma-deposition-pvd/
[7] J. Krupka and J. Mazierska, IEEE Trans. Instr. Meas., 2007, doi: 10.1109/TIM.2007.903647.
[8] M. Olszewska–Placha et al., 24th Intl. Microwave & Radar Conf. (MIKON), 2022, doi: 10.23919/MIKON54314.2022.9924947.

Alongside the three materials mentioned above, fergusonite-structured LnNbO4 (Ln=La, Sm, Nd etc.) ceramics have attracted attention due to their high quality factor Q and εr ~ 20. Any abrupt change in temperature coefficient of resonant frequency (TCF) is normally attributed to a change in τɛ usually caused by a structural phase transition. Phase transition which show an increase εr are commonplace in ferroic materials as commonly observed for paraelectric to ferroelectric/antiferroelectric, ferroelectric to ferroelectric, octahedral tilt and paraelastic to ferroelastic transformations. However, LnNbO4 microwave dielectric ceramics undergo a ferroelastic phase transition from monoclinic fergusonite to tetragonal scheelite structure and an anomalous dielectric valley values were observed at phase transition temperature (PTT). Assuming a linear increase in polarizability, the minimum value εr at the PTT was predicted from the Clausius–Mosotti relation and Shannon’s additive rule. Compared with ferroelectrics, relaxors, antiferroelectrics, ferroelastics, paraelectrics and linear dielectrics, the behaviour of εr in LnNbO4 vs temperature is anomalous and may have novel applications in temperature stable composite ceramics.

Relative permittivity (εr) at microwave frequencies determines the practical applications of microwave dielectric ceramics (MWDCs). The Clausius-Mossotti equation combining with additivity rule of dielectric polarizability (αD) is the most widely used method for εr prediction. The accuracy and the universality of the prediction depend on the αD data. The most influential αD database was put forward by Shannon, but it is facing three challenges in 5G era: (1) Few data, (2) Simplistic relation and (3) Low frequency (kHz ~ MHz) oriented. Here, based on the measured permittivities of 334 MWDCs, we optimized the αD database by the four-stage multiple linear regression (MLR) method. The MLR optimization enlarged the amount of data from 68 to 141, R2 was improved from 0. 9712 to 0.9946, and RMSE was reduced from 3.0162 Å3 to 1.3112 Å3. Based on the MLR optimized results, we employed machine learning (ML) method to establish the quantitative relation between the αD value and basic properties of ion, extending the amount of data substantially to 915, which covers 92 elements and still has good accuracy. Model analysis found that low atomic number (N), high valence state (V), low coordination number (CN) and high ionic radius (IR) usually accompany with low αD value normally, but not always. The positive cubic law of “αD ~ IR3 is valid for the IR change caused by the N, when the ions with the same V and CN; but the law is invalid for the IR change caused by CN, when the ions with the same V and N. The results and methodology would be of significance in the dielectric ceramics field.