High-temperature polymers, dielectric applications

Fully imidized aromatic thermoplastic polyimides (TPI) are linear polymers with good thermomechanical performance, used in high-temperature (>230°C) applications. Pis based on aromatic diamines and dianhydrides exhibit excellent heat resistance. In addition to their outstanding high-temperature resistance (Sancaktar et al. 1984 Sancaktar and Schenck 1985 Sancaktar and Dembosky 1986), toughness and good dielectric properties, low flammability, and high radiation resistance are desirable characteristics for this class of adhesives. 

Much attention has been paid to the synthesis of fluorine-containing condensation polymers because of their unique properties (43) and different classes of polymers including polyethers, polyesters, polycarbonates, polyamides, polyurethanes, polyimides, polybenzimidazoles, and epoxy prepolymers containing pendent or backbone-incorporated bis-trifluoromethyl groups have been developed. These polymers exhibit promise as film formers, gas separation membranes, seals, soluble polymers, coatings, adhesives, and in other high temperature applications (103,104). Such polymers show increased solubility, glass-transition temperature, flame resistance, thermal stability, oxidation and environmental stability, decreased color, crystallinity, dielectric constant, and water absorption. 

Electrical Properties. Polysulfones offer excellent electrical insulative capabilities 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 GHz (microwave) frequency range. This performance is retained over a wide temperature range and has permitted applications 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 applications. 

Silicon Nitride. Silicon nitride produced by high-temperature (>700 °C) CVD is a dense, stable, adherent dielectric that is useful as a passivation or protective coating, interlevel metal dielectric layer, and antireflection coating in solar cells and photodetectors. However, these applications often demand low deposition temperatures (<400 °C) so that low-melting-point substrates or films (e.g., Al or polymers) can be coated. Therefore, considerable effort has been expended to form high-quality silicon nitride films by PECVD. 

From the area of polymer dielectrics, a sample is presented here using a commercially available and (from many microelectronic applications) well-known high-temperature polyimide. The deposition and the subsequent curing process have been described in Section 18.2.3, resulting in a 190 nm thick insulating film that showed a good chemical resistance towards diluted developer solution and acetone, so that the cathode-sputtered Au drain and source contacts can be structured as described in Section 18.2.1. The 30 nm thick pentacene layer is thermally evaporated at a deposition rate of about 0.1 nm/s and a process pressure of 1 x 10 mbar. 

High-temperature resists have been formulated from a group of polyesters based on styrylpyridine, which are thermally stable up to 450°C. Such resists have found applications as fine-line solder masks or when the polymer is intended as a permanent eomponent of the final deviee, he it as insulator, interlayer dielectric, or a-particle harrier. ... 

Polyethersulfone Thermoplastic aromatic polymer has good heat and fire resistance, transparency, dielectric properties, dimensional stability, rigidity, and toughness, but poor solvent and stress cracking resistance, processibility, and weatherability. Processed by injection, blow, and compression molding and extrusion. Used in high temperature applications, electrical devices, medical devices, housings, and aircraft and auto parts. Also called PES. 

We have been designing films for low-k applications by using ethylene oxide/propylene oxide triblock copolymers as templates in porous films (5). The goal of this research is to discover polymers that phase separate from the matrix by forming small, isolated domains. The polymers are then removed in a high temperature step to generate the final porous material with a low dielectric... 

Melamine fibres are primarily known for their inherent thermal resistance and outstanding heat blocking capability in direct flame applications. This high stability is due to the cross-linked nature of the polymer and the low thermal conductivity of melamine resin. The dielectric properties and its cross-sectional shape and distribution make melamine ideal for high temperature filtration applications. It is sometimes blended with aramid or other high strength fibres to increase final fabric strength. 

Obtained copoly and block-copolyestersulfoneketones, as well as polyaiylates based of dichloranhydrides of phthalic acids and chloranhy-dride of 3,5-dibromine- -oxybenzoic acid and copolyester with groups of terephthaloyl-bis(w-oxybenzoic) acid possess high mechanical and dielectric properties, thermal and fire resistance and also the chemical stability. The regularities of acceptor-catalyst method of polycondensation and high-temperature polycondensation when synthesizing named polymers have been studied and the relations between the composition, structure and properties of polymers obtained have been established. The synthesized here block-copolyesters and copolyesters can find application in various fields of modem industry (automobile, radioelectronic, electrotechnique, avia, electronic, chemical and others) as thermal resistant constmction and layered (film) materials. 

Poly(p-xylene). A linear polymer consisting of directly linked / -xylene units in the macromolecular chain. Applications high-temperature dielectric films or coatings for special purpuses. Trade name Parylene (USA). 

Symposium on Advanced Dielectrics, Piezoelectric, Ferroelectric, and Multiferroic Materials Geopolymers and other Inorganic Polymers Materials for Solid State Lighting Advanced Sensor Technology for High-Temperature Applications... 

May, R. Victrex aromatic polymers for high temperature application. Proc. 7 Annu Des. Ing. Conf., Birmingham, 25-27 Sept, 1984 Kempston, 1984. P. 313-318. Shinyama, K., Fujita, S. Dielectric and thermal properties of irradiated polyetheretherketone IEEE Trans. Dielec, and Elec. Insul.. 2001. 8, N 3, c. 538-542. Hamciuc, Comeliu, Bruma, Maria, Klapper, Marcus Sulfonated poly(ether-ketone)s containing hexafluoroisopropylidene groups J. Macromol. Sci. A. 2001. 38, N 7, P. 659-671. 

Polymers with the highest dielectric strength, between 30 and 70 mV/m, have been used in a range of critical applications, as listed in Table 5.6, which shows that these polymers also have excellent arcing properties and are used in critical electrical applications, such as connectors, high-temperature insulators, cable coverings, switch gear components, and electronic components. 

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