Ceramic MEMS Designed for Wireless Pressure Monitoring in the Industrial Environment

This paper presents the design of a wireless pressure-monitoring system for harsh-environment applications. Two types of ceramic pressure sensors made with a low-temperature cofired ceramic (LTCC) were considered. The first type is a piezoresistive strain gauge pressure sensor. The second type is a capacitive pressure sensor, which is based on changes of the capacitance values between two electrodes: one electrode is fixed and the other is movable under an applied pressure. The design was primarily focused on low power consumption. Reliable operation in the presence of disturbances, like electromagnetic interference, parasitic capacitances, etc., proved to be contradictory constraints. A piezoresistive ceramic pressure sensor with a high bridge impedance was chosen for use in a wireless pressure-monitoring system and an acceptable solution using energy-harvesting techniques has been achieved. The described solution allows for the integration of a sensor element with an energy harvester that has a printed thick-film battery and complete electronics in a single substrate packaged inside a compact housing

Development of SiC-LC Resonant Wireless High Temperature Pressure Sensor

高温压力传感器在航天、航空、国防建设、能源开发等领域有广阔应用需求。传统硅材料在高于200℃后机械/电学性能均受到较大影响，无法满足高温应用要求。另一方面，传统高温传感器引线会导致电源、信号电路的温度升高问题，基于LC谐振的无线传感器能实现非接触式测量，达到电性连接、调理电路与高温热源之间物理隔离，提高传感器工作温度和稳定工作时间。因此，本论文提出一种SiC-LC谐振式无线高温压力传感器，主要研究工作如下： (1)根据LC谐振测量原理设计电感内置及电感外置两种敏感元件的结构方案，采用Silvaco软件对本体电容进行对比分析，得出电感内置结构具有本体电容小、谐振信号易于检测、制备工艺难度更低等...High temperature pressure sensor has broad application requirements in aerospace, aviation, national defense construction, energy development and other fields. Silicon material performance is greatly affected in the higher than 200℃ performance, can not meet the requirements of high temperature applications. At present, high temperature sensor will lead to power supply, signal circuit temperature...学位：工学硕士院系专业：航空航天学院_电气检测技术及仪器学号：1992014115289

Fabrication and characterization of free-standing thick-film piezoelectric cantilevers for energy harvesting

Research into energy harvesting from ambient vibration sources has attracted great interest over the last few years, largely as a result of advances in the areas of wireless technology and low power electronics. One of the mechanisms for converting mechanical vibration to electrical energy is the use of piezoelectric materials, typically operating as a cantilever in a bending mode, which generate a voltage across the electrodes when they are stressed. Typically, the piezoelectric materials are deposited on a non-electro-active substrate and are physically clamped at one end to a rigid base. The presence of the substrate does not contribute directly to the electrical output, but merely serves as a mechanical supporting platform, which can pose difficulties for integration with other microelectronic devices. The aim of this paper is to describe a novel thick-film free-standing cantilever structure that does not use a supporting platform and has the advantage of minimising the movement constraints on the piezoelectric material, thereby maximising the electrical output power. Two configurations of composite cantilever structure were investigated; unimorph and multimorph. A unimorph consists of a pair of silver/palladium (Ag/Pd) electrodes sandwiching a laminar layer of lead zirconate titanate (PZT). A multimorph is an extended version of the unimorph with two pairs of Ag/Pd electrodes and three laminar sections of PZT

Low cost fabrication processing for microwave and millimetre-wave passive components

Microwave and millimetre-wave technology has enabled many commercial applications to play a key role in the development of wireless communication. When dissipative attenuation is a critical factor, metal-pipe waveguides are essential in the development of microwave and millimetre-wave systems. However, their cost and weight may represent a limitation for their application. In the first part of this work two 3D printing technologies and electroless plating were employed to fabricate metal pipe rectangular waveguides in X and W-band. The performance for the fabricated waveguides was comparable to the one of commercially available equivalents, showing good impedance matching and low attenuation losses. Using these technologies, a high-performance inductive iris filter in W-band and a dielectric flap phase shifter in X-band were fabricated. Eventually the design and fabrication of a phased antenna array is reported. For microwave and millimetre-wave applications, system-on-substrate technology can be considered a very valuable alternative, where bulky coax and waveguide interconnects are replaced by low-loss transmission lines embedded into a multilayer substrate, which can include a wide range of components and subsystems. In the second part of this work the integration of RF MEMS with LTCC fabrication process is investigated. Three approaches to the manufacture of suspended structures were considered, based on laser micromachining, laser bending of aluminium foil and hybrid thick/thin film technology. Although the fabrication process posed many challenges, resulting in very poor yield, two of the solution investigated showed potential for the fabrication of low-cost RF MEMS fully integrated in LTCC technology. With the experience gained with laser machining, the rapid prototyping of high aspect ratio beams for silicon MEMS was also investigated. In the third part of this work, a statistical study based on the Taguchi design of experiment and analysis of variance was undertaken. The results show a performance comparable with standard cleanroom processing, but at a fraction of the processing costs and greater design flexibility, due to the lack of need for masks.Open Acces

Review of LTCC technology for millimeter waves and photonics

VTT Technical Research Centre of Finland Ltd. has developed and utilized Low Temperature Co-fired Ceramic (LTCC) technology for about 25 years. This paper presents our activities related to photonics and millimetre-waves, including also a relevant literature survey. First a short summary of the technology is given. Especially, the unique features of LTCC technology are described in more details. In addition, several examples have been given to show the validity of LTCC technology in these high-performance fields

Review of LTCC Technology for Millimeter Waves and Photonics

VTT Technical Research Centre of Finland Ltd. has developed and utilized Low Temperature Co-fired Ceramic (LTCC) technology for about 25 years. This paper presents our activities related to photonics and millimetre-waves, including also a relevant literature survey. First a short summary of the technology is given. Especially, the unique features of LTCC technology are described in more details. In addition, several examples have been given to show the validity of LTCC technology in these high-performance fields

Integrated sensors for process monitoring and health monitoring in microsystems

This thesis presents the development of integrated sensors for health monitoring in Microsystems, which is an emerging method for early diagnostics of status or “health” of electronic systems and devices under operation based on embedded tests. Thin film meander temperature sensors have been designed with a minimum footprint of 240 m × 250 m. A microsensor array has been used successfully for accurate temperature monitoring of laser assisted polymer bonding for MEMS packaging. Using a frame-shaped beam, the temperature at centre of bottom substrate was obtained to be ~50 ºC lower than that obtained using a top-hat beam. This is highly beneficial for packaging of temperature sensitive MEMS devices. Polymer based surface acoustic wave humidity sensors were designed and successfully fabricated on 128° cut lithium niobate substrates. Based on reflection signals, a sensitivity of 0.26 dB/RH% was achieved between 8.6 %RH and 90.6 %RH. Fabricated piezoresistive pressure sensors have also been hybrid integrated and electrically contacted using a wire bonding method. Integrated sensors based on both LiNbO3 and ZnO/Si substrates are proposed. Integrated sensors were successfully fabricated on a LiNbO3 substrate with a footprint of 13 mm × 12 mm, having multi monitoring functions for simultaneous temperature, measurement of humidity and pressure in the health monitoring applications

DESIGN, FABRICATION AND CHARACTERISATION OF FREE-STANDING THICK-FILM PIEZOELECTRIC CANTILEVERS FOR ENERGY HARVESTING

Research into energy harvesting from ambient vibration sources has attracted great interest over the last few years, largely due to the rapid development in the areas of wireless technology and low power electronics. One of the mechanisms for converting mechanical vibration to electrical energy is the use of piezoelectric materials, typically operating as a cantilever in a bending mode, which generate a voltage across the electrodes when they are stressed. Traditionally, the piezoelectric materials are deposited on a non-electro-active substrate and are physically clamped at one end to a rigid base, which serves as a mechanical supporting platform. In this research, a three dimensional thick-film structure in the form of a free-standing cantilever incorporated with piezoelectric materials is proposed. The advantages of this structure include minimising the movement constraints on the piezoelectric, thereby maximising the electrical output and offering the ability for integration with other microelectronic devices. A series of free-standing composite cantilevers in the form of unimorphs were fabricated and characterised for their mechanical and electric properties. The unimorph structure consists of a pair of silver/palladium (Ag/Pd) electrodes sandwiching a laminar layer of lead zirconate titanate (PZT). An extended version of this unimorph, in the form of multimorph was fabricated to improve the electrical output performance, by increasing the distance of the piezoelectric layer from the neutral axis of the structure. This research also discusses the possibility of using an array of free-standing cantilevers in harvesting vibration energy in a broader bandwidth from an unpredictable ambient environment