Coating Conformal

Parylene s use in the medical field is linked to electronics. Certain pacemaker manufacturers use it as a protective conformal coating on pacemaker circuitry (69). The coated circuitry is sealed in a metal can, so that the parylene coating serves only as a backup should the primary barrier leak. There is also interest in its use as an electrode insulation in the fabrication of miniature electrodes for long-term implantation to record or to stimulate neurons in the central or peripheral nervous system, as the "front end" of experimental neural prostheses (70). One report describes the 3-yr survival of functioning parylene-coated electrodes in the brain of a monkey (71). 

Conformal coatings are protective coatings appHed to circuit board assembHes. They protect the interconnect conductors, solder joints, components, and the board itself they reduce permeabiHty to moisture, hostile chemical vapors, and solvents in the coating. Use of conformal coatings eliminates dendritic growth between conductors, conductor bridging from moisture condensation, and reduction in insulation resistance by water absorption. 

The critical property for conformal coatings is resistance to chemicals, moisture, and abrasion. Other properties, such as the coefficient of thermal expansion, thermal conductivity, flexibiHty, and modulus of elasticity, are significant only in particular appHcations. The dielectric constant and loss tangent of the conformal coating are important for high speed appHcations. 

Ion plating is used to deposit hard coatings of compound materials, adherent metal coatings, optical coatings having high densities, and conformal coatings on complex surfaces. 

Union Carbide Corp. Parylene conformal coatings, photoresists, developers, etchants, solder masks, potting compounds... 

Conap unit of American Cyanamid potting compounds, conformal coatings... 

Du Pont Co. conformal coatings, photoresists, manufacturing aids, electronic functional coating compounds... 

Numerous protective conformal coatings are also used ia the hybrid circuit iadustry. Most of the criteria that pertain to use ia ptinted wiring also apply here (4). 

Mewtonian andMon-Mewtonian Materials. A Newtonian material s viscosity is shear-independent, whereas non-Newtonian materials are shear-dependent (Eig. 7). Eor most potting materials, a Newtonian material is preferred because the material is required to flow under all electronic components, but not be susceptible to shear. However, when flowable material is used for conformal coating appHcations, a non-Newtonian material with thixotropy agent added is desired since the material should flow on the electronic substrate but stop at the edge without creeping or mnover at the circuitry. 

Impreg na.tion Coa.ting. Impregnation coating is performed by saturation of the component with a low viscosity resia a thin film is coated on the component surface. This process is usually used with a cavity-filling or conformal coating process. 

Printed circuit board component such as laminates, conformal coatings, solder masks, masking tapes, component attachment adhesives, vibration dampers and photoresists. 

Also called conformal coating. It encloses a product in a closed envelope of plastic by immersing the product (solenoids, ornament, sensors, motor components, integrated circuits, and other articles.) in an unheated or... 

Teramura Y, Iwata H (2010) Bioartificial pancreas microencapsulation and conformal coating of islet of Langerhans. Adv Drug Deliv Rev 62 827-840... 

Jin, S.H., et ah, Conformal coating of titanium suboxide on carbon nanotube networks by atomic layer deposition for inverted organic photovoltaic cells. Carbon, 2012. 50(12) p. 4483-4488. 

J. W. Elam, D. Routkevitch, P. P. Mardilovich, and S. M. George, Conformal coating on ultrahigh-aspect-ratio nanopores of anodic alumina by atomic layer deposition, CherrL Mater. 15, 3507 (2003). 

Electronics and electrical (wires and cables, shrinkable tubing, displays, conformal coatings, adhesives, and battery separators)... 

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