| POLYMERS Vol.70 No.6 |
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COVER STORY
5G! Gather Round, Everyone |
| COVER STORY: Highlight Reviews |
| Interlayer Dielectrics for Printed-Wiring Boards: Thermosetting Resin | Mitsuru UEDA |
| <Abstract> The fifth-generation mobile communication system (5G) using the high frequency range is expected to be capable of the next generation of ultra-high-speed transmission and large-capacity transmission. Here, we will take up the interlayer dielectrics with low dielectric constant and low dielectric dissipation factor for printed-wiring boards supporting 5G, outline its necessity and material molecular design, and then introduce recent development of poly(aryl ether)s and modified polyimides as thermoset resins. Keywords: Fifth-Generation Mobile Communication System / Interlayer Dielectrics / Printed-Wiring Boards / Low Dielectric Constant / Low Dielectric Dissipation Factor / Thermosetting Resin / Poly(Aryl Ether) / Modified Polyimide |
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| LCP Materials for 5G Application | Akihiro NAGAE |
| <Abstract> 5G, which is the next-generation communication standard, has started, and demand of high-performance electric devices corresponding to high-frequency communication is increasing. Liquid crystalline polymer (LCP) is used as a major material for connectors and is known to have excellent heat resistance, flow ability and dimensional accuracy. Recently, control of dielectric properties is required for connector materials and I introduce the new LCP materials with excellent dielectric property. Keywords: Liquid Crystalline Polymer / Connector / Dielectric Property |
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| COVER STORY: Topics and Products |
| Development of Large Particle Size AlN Filler by Combustion Synthesis | Kazuto HARADA |
| <Abstract> Large particle size AlN fillers were produced using the heat of formation of combustion synthesis. Samples with different amounts of heat generated were synthesized by changing the ratio of Al and AlN in the raw material. The synthesized sample was crushed and then classified to produce AlN powders having particle sizes of 60 μm (D50). As a result of measuring the specific surface area of the AlN powder, the specific surface area decreased as the amount of heat generated increased. In addition, SEM observation confirmed that the crystal particles became larger. In order to evaluate the properties as a filler, a composite material of silicon oil and a sample was prepared, thermal conductivity and the change in viscosity with filler content was investigated. The AlN powders with a small specific surface area had better filling properties than the AlN powders with a large specific surface area, and thermal conductivity has a manifested high performance of 3.1 W/mK. Keywords: Aluminum Nitride / AlN Filler / Combustion Synthesis / SHS |
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| Material Design of Dielectric Particle Dispersed Polymer Composites | Yusuke IMAI |
| <Abstract> Polymer composites filled with inorganic particles are promising as dielectric material for high frequency application. Inorganic particles are dispersed in polymer matrix to control dielectric and thermal properties of the composites. Small particle size causes an increase of dielectric loss. The complex dielectric property of the composites can be estimated by Bruggeman effective medium theory if sufficiently large particles are used. Particles with anisotropic shape such as whisker shape can improve the temperature coefficient of the dielectric constant and the thermal expansion coefficient. Anisotropic particle shape is also effective for the improvement of thermal conductivity. Hollow particles can be utilized to improve temperature dependent properties while suppressing increase of the dielectric constant. Keywords: Composites / Bruggeman Theory / Whisker / Hollow Particle |
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| Technique for Reducing Conductor Loss of Transmission Line - Copper Wiring Fabrication on Smooth Surface | Jun SHIRAKAMI |
| <Abstract> A Cu micro strip transmission line was fabricated on the flat surface of typical polyimide film by using newly developed silver-seed plating technique. The transmission loss (S21) of the fabricated line showed almost same the same properties as one fabricated with commercial Cu laminated LCP film, even though the dielectric characteristics of those substrates are very different. As a result, the importance of surface flatness and smoothness of conductor lines for low loss signal transmission is confirmed, as predicted by theory. The Silver-seed plating technique which enables wiring formation on a flat and smooth surface, can be expected to be useful for wiring formation for high-speed transmission. Keywords: Silver-Seed Cu Plating / Transmission Loss / Flatness / Smoothness |
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| Computer Simulation of Dielectric Properties | Takashi MIYAKE |
| <Abstract> The computational approach is getting more and more to be a conventional tool for predicting materials properties. Here, we review computational methods for calculating the dielectric function. The imaginary part of the dielectric function originates from response to the external field. In GHz and THz region, orientation polarization and ionic polarization are main contributions, respectively. In the higher frequency region, the electronic polarization becomes dominant. When we consider the real part of the dielectric function, however, we cannot neglect the electronic polarization even though we are interested in GHz-THz region only, because the real and imaginary parts are related to each other through the Kramers-Kronig relation. For electronic polarization, first-principles calculation based on the Kubo-Greenwood formula is available. We present the calculation of the dielectric funtion of crystalline silicon as an example. The dielectric function, originated from ionic and orientation polarizations, can be evaluated by molecular dynamics simulation using the autocorrelation function of dipole moments. Finally, we introduce MateriApps, which is a portal site of materials science simulation. Keywords: Dielectric Function / Computer Simulation / First-Principles Calculation |
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| Complex Permittivity Measurement Methods of the Substrate Materials for Next-Generation Wireless Communication Systems | Yoshinori KOGAMI |
| <Abstract> Two complex permittivity evaluation techniques for dielectric substrates and films, which are developed as the circuit boad material used in next-generation wireless communication systems, or 5G and 6G, are introduced. One is the cylindrical cavity resonator method for the measurement of in-plane direction permittivity, another one is the balanced-type circular disk resonator method for in-vertical direction measurement. Keywords: Next-Generation Wireless Communication / Dielectric Substrates and Films / Complex Permittivity / Resonator Method |
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| Polymer Science and I: A Personal Account |
| My Apology and Appreciation to the Society of Polymer Science, Japan | Yosuke NIKO |
| <Abstract> In the past decade, I have made some immature and ridiculous comments in the conference of polymer science. In this article, I would like to show how I have dealt with and tried to recover from my mistakes while presenting a part of my research on the development of dye-loaded nanoparticles. |
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| Front-Line Polymer Science |
| Photo-Reworkable Adhesives and Photoresponsive Pressure-Sensitive Adhesives | Takahiro YAMAMOTO |
| <Abstract> This article describes recent progress in the development of photo-reworkable adhesives and photoresponsive pressure-sensitive adhesives. Light-induced solid-liquid transition of low-molecular-weight photochromic compouds, such as azobenzenes and anthracenes could be firstly applied for the development of photo-reworkable adhesives whose adhesion strength was tunable by light. While showing good debonding performance upon photoinduced liquefaction, adhesion strength has been remarkably improved by using polymers with photochromic parts in the side chains. Photoinduced solid-liquid transition behavior and photunable adhesion properties were extensively investigated in terms of an influence of the main chain structure, molecular weight, and architectures of the photochromic polymers. On the other hand, pressure sensitive adhesion could be modulated by means of photoplasticization which is photoinduced reduction of glass transition temperature of polymers using photochemical phase transition of photochromic liquid crystals. In addition, a photoreversibly curable pressure sensitive adhesive which has two adhesion states could be recently developed by employing a liquid crystal exhibiting a highly ordered smectic phase. Keywords: Adhesion / Pressure-Sensitive Adhesion / Photoplasticization / Photoliquefaction / Azobenzene / Photochromic Compounds |
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