Electronic applications, thermally

For semiconductor electronic applications, thermal oxides on SiC are employed as a masking material for ion implantation and dry etching, as a gate insulator for field-effect devices, and as a surface passivation. Oxidation can also be used to etch the surface of SiC, as well as for polarity determination and for the delineation of defects and boundaries in SiC [1]. The slow oxidation rate of deposited SiC has been used for local oxidation inhibition of silicon [2]. 

Metallo-organic CVD (MOCVD) is a specialized area of CVD, which is a relatively newcomer, as its first reported use was in the 1960s for the deposition of indium phosphide and indium anti-monide. These early experiments demonstrated that deposition of critical semiconductor materials could be obtained at lower temperature than conventional thermal CVD and that epitaxial growth could be successfully achieved. The quality and complexity of the equipment and the diversity and purity of the precursor chemicals have steadily improved since then and MOCVD is now used on a large scale, particularly in semiconductor and opto-electronic applications.91P1... 

Apart from the promising electrochemical properties that will be exhaustively discussed through this chapter, carbon nanotubes have become a hot research topic due to their outstanding electronic, mechanical, thermal, optical and chemical properties and their biocompatibility. Near- and long-term innovative applications can be foreseen including nanoelectronic and nanoelectromechanical devices, held emitters, probes, sensors and actuators as well as novel materials for mechanical reinforcement, fuel cells, batteries, energy storage, (bio)chemical separation, purification and catalysis [20]. 

Polyimides (PI) were among the earliest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, structure variations, and ultimately products and applications. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as structural composites, eg, over a ton of polyimide film is presendy used on the NASA shutde orbiter. Work continues on these materials, including the more recent electronic applications. 

Epoxies. The unique chemical and physical properties such as excellent chemical and corrosion resistances, electrical and physical properties, excellent adhesion, thermal insulation, low shrinkage, and reasonable material cost have made epoxy resins (qv) very attractive in electronic applications. 

Foams have a large variety of applications. Solid foams are widely used as insulating materials. Due to the presence of air bubbles they have a low thermal conductivity. Polyurethane foams and Styrofoam are examples. Styrofoam is also used as a packing material. The light weight of polymer foams makes them attractive as filling materials to stabilize otherwise hollow structures. A natural solid foam is pumice stone. Metal foams are used in the automotive and aerospace industry as light and stable materials [567], Ceramic foams are developed for electronic applications as piezoelectric transducers and low dielectric constant substrates [568],... 

The branched polysilanes show a broad emission peak around 450 nm, where the large red shift in the fluorescence spectra is due to the influence of aryl substituents and the introduction of branched points. For (opto)electronic applications, the UV irradiation and thermal stability are crucial to device stability. Branched polysilanes have better thermostability and are more resistant to UV irradiation than are linear polysilanes. 

Both polyimides and epoxy have found widespread use in many diverse industries. Polyim-ides, due to their excellent thermal and chemical stability and low dielectric constant, have become a favorite of the electronics industry. This broad class of polymers has found widespread use in a variety of electronic applications and the low cost has made epoxy popular as matrix materials in composites, adhesives and coatings. 

In addition to joining, adhesives in electrical applications may be required to conduct heat, conduct or isolate electricity, provide shock mounting, seal, protect substrates, etc. Thermal and chemical resistance, weathering, and structural compatibility must also be considered in diverse electrical and electronic applications. Of course, the choice of adhesive will also be governed by application methods, cure temperature, processing speed, and overall economic cost. 

Thermal conductivity is also important in highly integrated electronic applications where the heat generated by components must be transferred to a heat pipe or by some other means outside the electronic package. Thermal conductivity within adhesive systems is also a means of reducing exotherm and stresses that could develop during the curing cycle or other excursions to elevated temperatures. 

The values are within the limits for electronic application. The seal is thermally stable up to 180 °C. The investigations show that by tailoring chemical structures of sol-gel derived organically modified hetero polysiloxanes, mechanical and adhesive structures can be tailored for needs of application. 

Because of their toughness, flexibility and remarkable thermal stability, linear all-aromatic polyimides are excellent candidate film and coating materials for advanced electronic circuitry and wire coating applications. In past years, however, the inherent insolubility (1-2) of these polymers has somewhat limited their usefulness for electronic applications. 

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