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lord83铜虫 (小有名气)
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各位大大，帮忙翻译三段话，关于电子陶瓷的，不甚感谢
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he microwave devices have been traditionally machined from metal, and coaxial RF connections are provided with connectors generally leading to expensive heavy and bulky packages. These metal packages cannot meet the market demand for portable and low cost modules with multiple external I/Os. Additionally, electronic circuits for the automotive industry, entertainment electronics and telecommunications have to handle today a steady increasing amount of functions occupying as tiny space as possible. In the development of complex miniaturised circuits, flexible glass ceramic tapes, so called low temperature cofired ceramic (LTCC) tapes, play a decisive role as a base material. The LTCCs have been used for the past 15 years or so, and have become crucial in the development of various modules and substrates.3–5 This technology combines many thin layers of ceramic and conductors resulting in multilayer LTCC modules and have been generally used in the form of a three-dimensional (3D) wiring circuit board today, using low permittivity dielectric compositions. Additionally, it enables in a versatile mix of passive microwave components such as microstrips, strip lines, antennas, filters, resonators, capacitors, inductors, phase shifters and dividers making possible a whole matrix of design that are not practical on regular alumina or any soft substrates. Furthermore, these integrated components are interconnected with 3D strip line circuitry.3,6,7 Among the various components which could be realised in LTCC packages, the resonators and internal capacitors are important in terms of the latest technology. The internal capacitors are required to realise decoupling capacitors monolithically in LTCC packages, and the resonators are needed for filters of quarter wavelengths on the LTCC layer. The appropriate relative permittivity range for the resonators and the internal capacitors is 20–100 or even more.8,9 The embedding of these passive elements into a module also decreases its footstep saving top surface for discrete active components assemblies. The low sintering temperature provided by the LTCC technology is the key issue enabling its advantageous utilisation for today’s packaging concepts in microelectronic and microsystems and in microwave modules. Since the LTCC tapes can be sintered at low temperatures, the embedded microwave components and transmission lines can be fabricated using highly conductive and inexpensive metals such as silver or copper with low conductor loss and low electrical resistance at high frequencies. This is an advantage over other ceramic technologies. Furthermore, through materials’ research novel LTCCs with low dielectric loss, tan d (or high Q), and temperature compensated relative permittivity have been developed. If low thermal expansion (close to that of silicon), high strength and high thermal conductivity of the LTCCs are also taken into account, this technology can be seen very desirable even against polymer materials especially for low loss, high frequency circuits required for high speed data communications. The main purpose of this paper is to gather together the research carried out, discuss the performances available with different materials’ combinations and guideline further development required. A comparison of the material properties of a range of LTCC tape systems and some well known commercially available RF and microwave substrate and printed circuit board (PCB) materials are given in Table 1. For applicational reasons, low permittivity materials enabling fabrication of devices for high speed applications, are especially discussed. Additionally, the high relative permittivity, low dielectric loss and temperature stability of the electrical properties enabling microwave filters, with convenient size and impedance matching, low insertion loss, steep cutoff of the performance curve and operational stability against ambient change,10 are presented. The number of papers published and patents filed increased exponentially as shown in Fig. 1. |
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2楼2009-10-15 16:00:53
lord83
铜虫 (小有名气)
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3楼2009-10-16 16:20:42
