Selection of electrically conductive

Licari,J.J. Perkins,K.L. Caruso,S.V. Guidelines For The Selection of Electrically Conductive Adhesives for Hybrid Microcircuits, NASA CR-161978, 1981. 

To function as electrical conductors, epoxies and other polymer resins, because they are inherently insulators, must be filled with electrically conductive particles such as metals. The selection of electrically conductive or insulative adhesives is based largely on their conductivities or, conversely, on their volume resistivities. Electrically conductive adhesives should have low resistivities initially and retain those values on aging, moisture exposure, thermal cycling, and other operating and test conditions. The resistivities of metal-filled epoxy adhesives can range from... 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

The influence of other active components, such as 1, OH, H on a semiconductor sensor, with other conditions being the same, is comparable with the influence of atomic oxygen [50]. Contribution of N and OH is proportional to their relative contents (compared to that of atomic oxygen) in the atmosphere and may become essential at altitudes lower than 60 - 70 km. The use of selective detectors excludes the influence of atomic hydrogen. Studies of adsorption of water vapours on ZnO films [50] show that their influence is negligibly small at the film temperatures below 100°C. Variations of electric conductivity of the films under the influence of water vapours and of an atomic oxygen are comparable at the ratio of their concentrations [H20]/[0] = 10" . 

Electrochemical doping of insulating polymers has been attempted for polyacetylene, polypyrrole, poly-A/-vinyl carbazole and phthalocyaninato-poly-siloxane. Significantly, Shirota et al. [91] claim to have achieved the first synthesis of electrically conducting poly(vinyl ferrocene) by the method of electrochemical deposition (ECD) [91]. This is based on the insolubilization of doped polymers from a solution of neutral polymers. A typical procedure applied [91] for polyvinyl ferrocene is to dissolve the polymer in dichlorometh-ane and oxidize it anodically with Ag/Ag+ reference electrode under selective conditions. The modified polymer [91] (Fig. 28) is a partially oxidized mixed valence salt containing ferrocene and ferrocenium ion pendant groups with C104 as the counter anion. 

The discovery of electrical conductivity and superconductivity in crystalline materials derived from conventional molecular species effectively introduces a new area of synthetic chemistry. The conductivity is associated with specific molecular arrays and synthesis of the materials requires the ability to conceive and implement the preparation of a particular crystalline state. Molecular conductors are derived from pairs of redox reagents, an area where heterocyclic systems are well established. Placement of heteroatoms of selected electronegativity at chosen positions in a delocalized electron system offers a subtle and effective means for altering the orbital energies which ultimately control the electron transfer properties of redox reagents. 

In this review we shall focus on some of these new forms of solid carbon. The emphasis is on the physical properties of electrically conducting fullerides, fulleride polymers and nanotubes, but the neutral fullerene polymers, dimers and onion-like structures are also included for completeness. This paper is by no means a review of all important work in the domain. We fully realize that in choosing the material we had to be subjective and we selected material best known to us. A few other short reviews have been published recently on fullerene polymers on the optical properties of polymeric fullerenes [15] and on the physical properties of conducting fullerenes [16,17]. There are extensive recent reviews on the pressure and heat induced polymers [18]. We did not include in the paper the physical and chemical properties of alkali fullerides with variously charged monomer ions. These are the subject of other reviews and are described in detail in a recent monograph [19]. In particular, there are comprehensive reviews [20,21] on experiments and theories aimed at the understanding of the mechanism of superconductivity. 

The extraordinary mechanical, thermal and electrical properties of carbon nanotubes (CNT) have prompted intense research into a wide range of applications in structural materials, electronics, and chemical processing.Attempts have been made to develop advanced engineering materials with improved or novel properties through the incorporation of carbon nanotubes in selected matrices (polymers, metals and ceramics). But the use of carbon nanotubes to reinforce ceramic composites has not been very successful. So far, only modest improvements of properties were reported in CNTs reinforced silicon carbide and silicon nitride matrix composites, while a noticeable increase of the fracture toughness and of electrical conductivity has been achieved in CNTs reinforced alumina matrix composites. ... 

In this section we discuss three applications of electrically conductive adhesives die attach adhesives, anisotropically conductive adhesives for liquid crystal display (LCD) assembly, and conductive adhesives for surface-mounted assembly of packaged components on printed wiring boards (PWBs). These applications were selected based on overall... 

This principle makes it possible to predict the sign of conduction of a mixed-valence phase, to explain the appearance of electrical conduction, and to select reliably ways of preparing materials with prescribed thermoelectric properties. The problem of the simultaneous introduction of several impurities into a semiconductor is considered. The role of cation and anion vacancies is determined. The thermo-emf power is estimated from the possibility of the appearance of ions of "abnormaT valence and from the role of the resultant polar bonds. The limits of the validity of Vetwey s principle are considered. 

In this section, the preparation of electrically conductive polyvinyl acetate (PVA) nanofibres, using vapour phase chemical polymerisation of pyrrole onto the surface of the nanofibres, is investigated. PVA is highly biocompatible and nontoxic and was selected for this study because of its excellent chemical resistance and physical properties. 

The selection of polymeric matrix depends on the final application of electrically conductive composites. For a specific purpose, an optimal balance among mechanical, optical, thermal, ecological, and other properties must be maintained. Various classes of polymers have been used for composite preparation, such as soft elastomers and rubbers, linear or branched thermoplastics, or hard duromers as epoxies. All these materials cover a wide range of properties. The main physical and structural parameters that influence the final electrical behavior of multiphase materials are the polymer surface chemistry, degree of crystallinity, and the thermal and mechanical behavior. 

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