The first part of this thesis proposes a method to synthesize the T- and £S-prototype of band-pass filters using the two reflection zeros and the rolloff rate. According to the characteristics of passive components embedded in different substrates, £S-prototype band-pass filter is suitable for implementation on LTCC substrate, while T-prototype band-pass filter is suitable for implementation on organic substrate. The second part of this thesis employs the £S-prototype to design the LTCC band-pass filters. It has been found that mutual coupling and feedback elements can be used to create the multiple transmission zeros. With these synthesized transmission zeros, the stopband attenuation can be enhanced at several specific frequencies. For demonstration, this thesis implements the LTCC band-pass filters in 2.4 GHz ISM band and 3.5 GHz WiMAX band. The measured results show that insertion loss and return loss in the passband for these LTCC filters is less than 2 dB and more than 10 dB, respectively. In addition, these filters have the additional transmission zeros for enhancing the stopband attenuation. Moreover, miniaturization is also a key issue in implementing these LTCC filters. The 2.4 GHz and 3.5 GHz LTCC filter can meet the standard 1608 size and 2520 size, respectively, which are the smallest compared to the other LTCC filters reported for similar applications in the current literature and commercial media.

This thesis proposes an analytical method to synthesize bandpass filter with multiple transmission zeros. By using the six pre-determined parameters including two reflection zeros, two matching quality factors, and two transmission zeros, the method can exactly synthesize the corresponding prototype of second-order coupled-resonator bandpass filter. The synthesized filters not only can provide two pre-determined transmission zeros in the lower and upper side of the passband, but also can generate an extra transmission zero in the stopband. This thesis presents the prototypes of the bandpass filter and the methods of synthesis in detail. Finally this thesis implements compact LTCC bandpass filters by using the proposed synthesis method for 3.5 GHz WiMAX applications.

ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / This paper addresses the future military munitions' system requirements for antennas in terms of the existing versus new fabrication technology. The antenna requirements of the future smart munitions will be GPS for precision guidance and TM for system performance testing. The environmental requirements remain the same; large temperature operating range with operation at high temperatures and high shock capable. As usual, the munitions are getting smaller, frequency bandwidth is getting larger, and the cost of the antennas must be minimized in production quantities. In particular this paper compares the existing antenna fabrication technology of Teflon based dielectric printed circuits versus multilayer alumina in the green state, a technology that has been perfected for fabricating microwave integrated circuits (MIC's). The trade-offs that will be addressed are temperature, shock, cost, tunability, loss, size, dielectric constant, and frequency bandwidth. There has been a significant effort to miniaturize the GPS and TM antenna using higher dielectric constant materials. The most popular direction of this effort has been to use ceramic impregnated Teflon. The ultimate temperature performance is the material with a dielectric constant around 2 since this material exhibits a very low coefficient of change with temperature. Materials are available with nominal dielectric constants of 6 and 10 to reduce the size of the antenna but the coefficient of change with temperature is very large and leaves these materials marginal for military temperature ranges. There have also been two other problems with Teflon based printed circuit boards, forming and bonding the boards in a 3D shape and homogeneity of the dielectric constant in the board and after bonding. These problems usually make tuning a requirement and drive the cost of antenna fabrication up. There has been a revolution in MIC's. The circuits are now being made with multiple layers of ceramic (alumina) with interlayer conductive connections and a nominal dielectric constant of 10. The layers are formed in the green state and fired at high temperature and the resulting alumina substrate has a very low coefficient of change with temperature and low loss. Since this procedure is now beyond development, the cost is low and the volume capability is high. Another significant point is that the part can be any shape since the substrate is done in the green state (formable) and then fired.

Zugl.: Saarbrücken, Univ., Diss., 2009

In this thesis, a novel System-on-Package (SoP) antenna concept has been developed for 24 GHz automotive radar applications. High-performance applications such as automotive radars require miniaturization, excellent performance and a high level of integration. The multi-layer Low-temperature co-fired ceramic (LTCC) SOP approach is an effective solution to meet these stringent needs as it offers not only great capability of integrating embedded functions, but also the real estate efficiency and cost-savings. The antenna concept utilizes a mixed LTCC tape system and combines for the first time a fractal antenna array and an integrated grooved Fresnel lens. The overall gain of the system is 15 dB which includes a 6 dB gain enhancement due to the integration of the lens. The bandwidth is 1.8 GHz which is 7.5% of the center frequency. The three types of dielectric Fresnel lenses (grooved, multi-dielectric and perforated) have been investigated as gain enhancement and beam shaping components for high performance LTCC SoP applications. A high dielectric constant material has been utilized to realize the lenses in the LTCC medium. All three lenses perform well with significant gain enhancement (>6 dB) and beam shaping despite their compact sizes (2.4 cm x 2.4 cm). The excellent performance makes all three lenses highly suitable for high performance SoP applications with the grooved lens being most suitable due to the relative ease of fabrication.

Abstract In the interest of improving reliability, electrical monitoring methods were utilized to observe the degradation of electronics interconnections while simultaneously characterizing accelerated testing-induced changes in test structures by means of optical examination, X-ray, scanning acoustic microscopy and scanning electron microscopy. To improve the accuracy of lifetime prediction for the PCSB interconnections investigated in this work, a modified Engelmaier’s solder joint lifetime prediction model was recalibrated. The results show that with most of the presented lead-free (SAC387, SAC405, SAC-In) solder and structure combinations with a large global thermal mismatch (ΔCTE > 10 ppm/°C), lifetime was adequate in the presented TCT ranges of 0‒100 °C and −40‒125 °C, while the amount of non-preferred crack types, i.e. ceramic cracks, was minimized. Degradation of interconnections was characterized using RF measurements both during TCT and intermittently during TCT breaks. A grounded coplanar waveguide was arranged either in a straight back-to-back configuration or together with a filter module with a passband at 22‒24 GHz—both with two transitions—and characterized during cycling breaks up to 25 GHz and 30 GHz, respectively. Besides off-cycle measurements, in-cycle measurements were done on an antenna structure with an in-band at 10‒11 GHz, up to 14 GHz. The results show that the signal response was initially affected at some frequencies as short-duration (< 1 s) glitches in the monitored signal when measured during cycling in 0‒100 °C TCT. Later on the degradation could be observed in the whole frequency band as TCT was continued. Development of the semi-empirical lifetime prediction model for PCSB interconnections showed the temperature range dependency of the correction term to be a second order polynomial instead of a logarithmic one. For components with PCSB BGA, promising prediction results were achieved which differed from the realized lifetime by less than 0.5% at best. / Tiivistelmä Elektroniikkaliitosten rikkoontumisen seurantaan tarkoitettuja sähköisiä monitorointimenetelmiä kehitettiin samanaikaisesti karakterisoimalla testauksella liitoksiin aikaansaatuja muutoksia optisesti, akustisella mikroskoopilla sekä röntgen- ja pyyhkäisyelektronimikroskoopeilla. Liitosten eliniän ennustamiseen soveltuva muokattu Engelmaierin malli kalibroitiin PCSB-liitosten elinikäennusteen tarkkuuden parantamiseksi. Tulosten perusteella useimmille tässä työssä käytetyille lyijyttömille (SAC387, SAC405, SAC-In) juotteille ja suuren termisen epäsovituksen (ΔCTE > 10 ppm/°C) rakenneyhdistelmille eliniät lämpösyklaustesteissä 0‒100 °C ja −40‒125 °C alueilla olivat riittävät ja haitallisimpien murtumien, eli keraamimurtumien, määrä saatiin minimoiduksi. RF-mittauksia käytettiin liitosten vikaantumisen seurantaan sekä lämpösyklauksen aikana että syklausten välillä. Maadoitettua koplanaarista aaltojohtoa käytettiin joko suoraan perättäiskytkennässä tai suodatinmoduulin kanssa, jonka päästökaista oli 22–24 GHz. Rakenteet karakterisoitiin syklausten välillä 25 GHz ja 30 GHz asti tässä järjestyksessä. Näiden mittausten lisäksi 10–11 GHz kaistalla toimivaa antennirakennetta karakterisoitiin syklauksen aikana 14 GHz asti. Tulokset osoittavat, että signaalivasteen muutos ilmenee aluksi joillakin taajuuksilla lyhyinä, alle 1 s mittaisina häiriöpiikkeinä, 0‒100 °C syklauksen aikana. Syklauksen edetessä vasteen huononeminen havaitaan myöhemmin koko mittausalueella. Puolikokeellista elinikäennustemallia tarkasteltaessa havaittiin, että PCSB-liitosten lämpötila-alueesta riippuvia korjauskertoimia kuvasivat logaritmisen riippuvuuden sijaan parhaiten toisen asteen polynomifunktiot. PCSB BGA ‒rakenteille saadun ennusteen ja toteutuneen eliniän välinen ero oli pienimmillään alle 0.5 %.

Abstract The thesis describes electrically tunable microwave devices utilising low sintering temperature, screen printable Barium Strontium Titanate (BST) thick films. The work has been divided into two parts. In the first section, the fabrication and microwave characterisation of BST material based structures compatible with Low Temperature Cofired Ceramic technology (BST-LTCC) are presented. Three different fabrication techniques, namely: direct writing, screen printing and via filling techniques, were used for the realisation of the structures. A detailed description of these fabrication techniques is presented. The dielectric properties such as relative permittivity, static electric field dependent tunability and loss tangent of BST-LTCC structures at microwave frequencies were characterised using coplanar waveguide transmission line and capacitive element techniques. The measured dielectric properties of BST-LTCC structures realised with the different fabrication methods are presented, compared and discussed. The second section describes tunable microwave devices based on BST-LTCC structures. A frequency tunable folded slot antenna (FSA) with a screen printed, integrated BST varactor is presented. The resonant frequency of the FSA was tuned by 3.2% with the application of 200 V external bias voltage. The impact of the BST varactor on the total efficiency of the antenna was studied through comparison with a reference antenna not incorporating the BST varactor. A compact, frequency tunable ceramic planar inverted-F antenna (PIFA) utilising an integrated BST varactor for mobile terminal application is presented. The antenna's resonant frequency was tuned by 3% with an application of 200 V bias voltage. Frequency tunable antennas with a completely integrated electrically tunable BST varactor with silver metallisation are introduced in this work for the first time. The integration techniques which are described in this thesis have not been previously reported in scientific literature. The last part of the thesis presents a microwave delay line phase shifter operating at 3 GHz based on BST-LTCC structures. The figure of merit (FOM) of the phase shifter was measured to be 14.6 °/dB at 3 GHz and and the device employs a novel structure for its realisation that enabled the required bias voltage to be decreased, while still maintaining compliance with standard screen printing technology. The performance of the phase shifter is compared and discussed with other phase shifters realised with the BST thick film process. The applications of BST-LTCC structures were demonstrated through frequency tuning of antennas, varactors, and phase shifters. The low sintering temperature BST paste not only enables the use of highly conductive silver metallisation, but also makes the devices more compact and monolithic.

Abstract The recent trend in low temperature co-fired ceramic (LTCC) technology is to integrate more elements into multilayer modules. This thesis describes work specifically aimed at developing ferroelectric barium strontium titanate (BST) for integration into such modules. In particular, an objective was the development of a novel, electric field controlled, tunable component to be used at microwave frequencies (2–26 GHz). For the application envisaged, relative permittivity is required to be low (100–1000) and adjustable by a suitable applied electric field, the dissipation factor at room temperature must be low (~0.001) at 2–26 GHz, and most importantly, the sintering temperature must be suited to the LTCC technology (~900 °C) Initial work was focused on sol-gel derived Ba0.7Sr0.3TiO3 powders with boron oxide addition, which were sintered at 900 °C, the dissipation factor was 0.006. The dissipation factor was not low enough for the desired microwave application, and attention turned to powders prepared by the mixed-oxide route. The Ba0.7Sr0.3TiO3 powders, fluxed with the optimum amounts of boron oxide and lithium carbonate, could be sintered at 890 °C to the same density as is achieved with un-fluxed Ba0.7Sr0.3TiO3 sintered at 1360 °C. The dissipation factor for this fluxed powder was acceptably low, although permittivity was too high for the particular objective. Subsequently, research was on BST modified by magnesia, 0.4Ba0.55Sr0.45TiO3-0.6MgO (BSTM). With the optimum fluxing additives, the sintering temperature necessary to achieve a dense BSTM-based ceramic was reduced to 950 °C. The developed microstructure was good, and the relative permittivity and dissipation factor values (221, 0.0012 at 1 kHz) at room temperature indicated good microwave properties. Studies were also undertaken with organic-based tape-casting slurries, laminating procedures and burn-out and sintering schedules. Several kinds of tapes were fabricated and characterized. A test structure for the measurement of dielectric properties at 26 GHz of the optimized BSTM-based ceramic was constructed. The specimen was 50 μm thick layer of BST on an alumina substrate. The relative permittivity and tunability were 130 and >15 % at 4 V μm-1 at room temperature. A tunable phase-shifter was fabricated from the same BSTM-based tape using a novel gravure printing technique, and measurements at 26 GHz showed phase shift from 10 to 35° when the electric field was increased from 1 V μm-1 to 2.5 V μm-1. Some exploratory experiments are described to assess the compatibility of the developed BST-based LTCC with commercial LTCC and some electroceramics.

Abstract The thesis describes the development of a novel LTCC material system for RF and microwave telecommunication purposes. The work has been divided into three parts. In the first section, the compositional and firing properties of this novel LTCC dielectric have been studied as well as its thermomechanical and dielectric properties. The second section describes the multilayer component preparation procedure for the ceramic material including tape casting and lamination parameters and the selection of the conductor paste. In the last section, the novel LTCC material system has been used to demonstrate its properties in RF multilayer resonators and a bandpass filter. The dielectric material for the novel LTCC system was prepared using magnesium calcium titanate ceramic, the firing temperature of which was decreased to 900°C by the addition of a mixture of zinc oxide, silicon oxide and boron oxide. The powder was made without any prior glass preparation, which is an important process advantage of this composition. The fired microstructure was totally crystalline with high density (3.7 Mg m-3) and low porosity (0.5 %). The mechanical properties were virtually identical to the values of the commercial LTCCs, but the higher thermal expansivity makes it most compatible with alumina substrates. The dielectric values were also good. The permittivity was 8.5 and the dissipation factor (0.9·10-3 at 8 GHz) less than that of the commercial LTCCs. Furthermore, the temperature coefficient of the resonance frequency was demonstrated to be adjustable between the range of +8.8 ... -62 ppm/K with a simple compositional variation of titanium oxide. The slurry for the tape casting was prepared using poly(vinyl butyral) -base organic additives and the 110 μm thick tapes had a smooth surface (RA < 0.5 μm). The multilayer components were prepared using 20 MPa lamination pressure, 90°C temperature and 1 h dwell time. The most suitable conductor paste for this composition was found to be commercial silver paste (duPont 6160), which produced satisfactory inner and outer conductor patterns for multilayer components. Finally, resonators with a resonant frequency range of 1.7 ... 3.7 GHz were prepared together with a bandpass filter suitable for the next generation of telecommunication devices. This demonstration showed the potential of the developed novel LTCC material system at high RF frequencies.

Abstract It has been over a century since the Curie brothers discovered the piezoelectric effect. Since then our knowledge about this phenomena has been constantly growing, accompanied by a vast increase in its applications. Modern piezoelectric devices, especially those meant for use in personal equipment, can often have complicated shapes and electric circuits; therefore, a suitable and cost effective packaging method is needed. The recent introduction of self-constrained Low Temperature Co-fired Ceramic (LTCC) characterized by virtually no planar shrinkage has pushed the limits of this technology a step further. The practical lack of dimension change between “green” state and sintered ceramic has not only improved the design of multilayer smart packages but also allowed the embedding of other bulk materials within the LTCC and their co-firing in one sintering process. This thesis introduces a novel method of seamlessly embedding piezoelectric bulk structures in LTCC by co-firing or bonding with adhesive. Special attention is paid to the multistage lamination and post-firing poling of the piezoelectric ceramics. Examples of several structures from the main areas of piezoelectric applications are presented as proof of successful implementation of the new technique in the existing production environment. The performance of the structures is investigated and compared to structures manufactured using other methods. Integration of bulk piezoelectric structures through co-firing is a new technique with a wide area of applications, suitable for mass production using existing process flow. / Tiivistelmä Curien veljekset havaitsivat pietsosähköisen ilmiön jo yli sata vuotta sitten. Ilmiöön liittyvä tutkimustieto ja erityisesti siihen perustuvien sovellusten määrä on nykyisin valtava. Uusissa pietsosähköisissä komponenteissa ja varsinkin niissä, jotka on tarkoitettu henkilökohtaisissa laitteissa käytettäviksi, muodot samoinkuin elektroniikapiirit voivat olla monimutkaisia. Siksi tarvitaan tarkoituksenmukaista ja hinnaltaan edullista laitteen pakkausmenetelmää. Hiljattain kehitetyt itseohjautuvat matalan lämpötilan yhteissintattavat keraamit (LTCC), joiden planaarinen kutistuma on lähes olematon, ovat lisänneet LTCC-teknologian sovellusmahdollisuuksia. Muotoon valmistetun sintraamattoman ja lopullisen sintratun keraamin dimensioiden yhtäsuuruus ei ole ainoastaan parantanut älykkäiden monikerrospakkausten suunnittelua, vaan mahdollistanut myös erilaisten materiaalien ja komponenttien upottamisen LTCC-rakenteisiin ja niiden yhteissintrauksen. Väitöstyössä esitetään uusi menetelmä pietsosähköisten bulkrakenteiden upottamiseksi saumattomasti LTCC-rakenteisiin yhteissintrauksella tai liimaliitoksella. Erityistä huomiota on kiinnitetty monivaiheiseen laminointiin ja sintrauksen jälkeiseen pietsosähköisten keraamien polarisointiin. Työssä on esitetty esimerkkejä useista rakenteista pietsosähköisten sovellusten pääalueilta osoituksena uuden tekniikan onnistuneesta käyttöönottamisesta nykyisessä valmistusympäristössä. Tutkittujen uusien rakenteiden ja muilla menetelmillä valmistettujen rakenteiden ominaisuuksia on verrattu keskenään. Pietsosähköisten bulkrakenteiden integroiminen yhteissintrauksella on uusi tekniikka, joka mahdollistaa lukuisia sovelluksia ja soveltuu massatuotantoon olemassa olevilla prosseintilaitteistoilla.