Wire insulation dielectric constant

Electrical Properties. CeUular polymers have two important electrical appHcations (22). One takes advantage of the combination of inherent toughness and moisture resistance of polymers along with the decreased dielectric constant and dissipation factor of the foamed state to use ceUular polymers as electrical-wire insulation (97). The other combines the low dissipation factor and the rigidity of plastic foams in the constmction of radar domes. Polyurethane foams have been used as high voltage electrical insulation (213). 

The dielectric constant of a compound is increased by small amounts of absorbed water hence wire insulation for communications generally must have a dielectric constant as stable as possible in the presence of water or moisture. 

Power factor, like the dielectric constant, is a property that represents a power loss that takes place when a wire insulation becomes the dielectric of a condenser because of a surrounding sheath or other conducting medium. 

Electrical Properties. Polysulfones offer excellent electrical insulative capabiUties and other electrical properties as can be seen from the data in Table 7. The resins exhibit low dielectric constants and dissipation factors even in the GH2 (microwave) frequency range. This performance is retained over a wide temperature range and has permitted appHcations such as printed wiring board substrates, electronic connectors, lighting sockets, business machine components, and automotive fuse housings, to name a few. The desirable electrical properties along with the inherent flame retardancy of polysulfones make these polymers prime candidates in many high temperature electrical and electronic appHcations. 

Wire and cable insulation based on vulcanizates of PZ has also been studied. Again, low fire risk was the target property, and this was achieved. The need to vulcanize the coating, somewhat modest tensile properties, tensile strength of 5.2 to 12.2 MPa (760 to 1770 psi), and high dielectric constant (4—5 at 10,000 Hz) limited interest in this appHcation (19). 

If the wire is to be used to carry much higher frequency currents, the design problem in geometry and plastic selection becomes more complicated. The dielectric constant and dielectric loss values for the plastics become important in the design. At a frequency of one megahertz the effect of the dielectric on the power transmission behavior of the wire is substantial and, even at frequencies of 10 to 100 kilohertz, the insulation on the wire must be considered in the design as a major electrical element in the circuit. More on the subject of insulation will be following this section. 

Dielectric constant/loss The value of the dielectric constant is important in the wire because of the effect that it has in coupling currents in one set of wires into another set of wires. The higher the dielectric constant, the higher the value capacitor that is formed between two wires. The capacitor thus formed is a signal carrying device at the frequencies used in communications and a signal can be capacitively coupled from one circuit to another. PE is the preferred choice for insulation of communication wire because of its low dielectric constant that minimizes the intercircuit coupling effect usually referred to as cross-talk. 

The polarity of EVAs leads to an increase in loss factors and dielectric constants but the insulating properties allow their use for wire coating. For example, between 10% and 30% VA ... 

Two other important electrical properties must be taken into consideration when polymers are used as insulation for a high-voltage power cable or electronic wires. ° These are the dielectric constant and the dielectric loss factor, which characterize the energy dissipation in the insulation, the capacitance, the impedance, and the attenuation. 

High water absorption is die other problem with insulation materials, because it causes corrosion of metal wiring and instability of electrical properties such as the dielectric constant. Conventional polyimides have relatively high water absorption because of tiie presence of polar imide rings. However, the water absorption decreases when fluorine is introduced into polyimide molecules because of the former s hydrophobic nature. ... 

As the size of microchips evolves from 130nm to 90nm or smaller, the increasing packing density between multilevel interconnects will lead to severe RC delay, power consumption and wire cross talk, which are the major factors limiting device performance. As a consequence, the design of novel semiconductor materials with desired chemical and physical properties has stimulated intense experimental and theoretical efforts. For example, there have been ongoing activities to develop materials with low dielectric constants (k) to replace the current silicon dioxide (k = 4.0) wire insulator. A particularly active area of research in the past few... 

The electrical properties of polymers are important in many applications [1]. The most widespread electrical application of polymers is the insulation of cables. In recent years, high-performance polymers have become important in the electronics industry as encapsulants for electronic components, as interlayer dielectrics, and as printed wiring board materials. The dielectric constant (or permittivity) and the dissipation factor (or power factor or electrical loss tangent) tan 8, which are dimensionless quantities, are the key electrical properties. 

Electrical Communications Low dielectric constant High volume/surface resistivity High dielectric breakdown voltage Flame resistance, thermal stability Wire and cable insulation, connectors... 

The dielectric constant of rigid PU foams Rigid polyurethane foam (PUF) preinsulated pipes for district heating systems need measuring systems to detect leakage in a pipeline network while it is in use. One of such systems measures the absorption of a reflected pulse, transmitted via a copper wire embedded in the PUF insulation. Information about the dielectric constant and loss factor of these foams as a function of the foam density and the MDI index (see 4.1.3) was necessary to calibrate such a system. 

The dielectric constant of LCP films is typically 2.7 to 3.0, making them attractive for high speed electronic circuit substrates. Tlie dielectric strength of over 7,000V per mil combined with very low moisture absorption (less than 0.2 percent by weight) meets requirements for electric wire and cable insulation. 

Silica is a material with a low dielectric constant of k—4.0. In order to increase the packing density between multilevel interconnects, new. ultralow-k materials are needed. Because k decreases with decreasing density, crystalline and noncrystalline porous silicas with DK as low as A <2.0 were introduced to replace the current wire insulators in microelectronics for multilayer deviees. Because of their low density, ordered mesoporous materials are used for practical purposes. ... 

Table 10.8 shows electric strengths. Table 10.9 shows volume resistivities, Table 10.10 shows dielectric constants, and Table 10.11 shows dissipation factors for coatings using most of the available resins. Magnet wire insulation is an important use for organic coatings. National Electrical Manufacturer s Association (NEMA) standards and manufacturers trade names for various wire enamels are shown in Table 10.12. This information can be used to guide the selection of coatings. However, it is important to remember the aforementioned warnings about blends of various resins and the effects on performance properties.

Telecommimication cables establish a wired connection between users to allow data transmission and audiovisual commimication. The main characteristics required from the polymer insulation are a low dielectric constant and low dissipation factor. As the best dielectric properties are given by air, the dielectric losses can be reduced drastically by expanding the insulation (30-50% vol.% inert gas) this is called cellular insulation, as opposed to solid insulation. 

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