Electrical Insulation and Dielectric Materials

Electrical insulation and dielectric materials includes various forms of materials that surround and protect electrical conductors and prevent unwanted current flow, leakage, or crosstalk.

 

Electrical Specifications

Electrical specifications include electrical resistivity, dielectric strength, and dielectric constant.

  

Resistivity is the longitudinal electrical resistance (ohm-cm) of a uniform sample of unit length and unit cross-sectional area.

  

Dielectric strength is the maximum voltage field that electrical insulation and dielectric materials can withstand before electrical breakdown occurs.

  

Dielectric constant is the relative permittivity of a material compared to a vacuum or free space. k = εr = ε / εo= where ε is the absolute permittivity of the material and εo is the absolute permittivity of a vacuum 8.85 x 10-12 F/m.

  

Material Forms

Electrical insulation and dielectric materials are available in many different material forms.

 

Adhesive - Adhesives are organic or inorganic chemical compounds for joining components. They require clean surfaces that are compatible with the adhesive.

 

Bar Stock - Stock products are available in the form of a bar or rod, usually with a square cross-section. Stock forms can be processed in rectangular, oval, hexagonal, or other shapes.

 

Blanket / batt - Blankets or batts (batting) are made of thick layers of woven and/or nonwoven fabric sheets.

 

Block - Blocks are building materials or masonry units consisting of fired ceramic or cement materials with a regular shape. Blocks usually have a rectangular shape, although specialized shapes are used for paving, refractory, decorative and other specialized applications. Refractory or fireclay blocks are manufactured from temperature resistant materials. Refractory blocks are stacked to form an insulating furnace, boiler, or other thermal process vessel wall. The refractory blocks are usually cemented together with a refractory mortar. Blocks are similar to bricks but typically smaller in overall dimensions.

 

Braided product - Braided products are used for tubular composite structures, thermal insulation fabrics, and in other applications.

  

Ceramic / inorganic - Ceramic or inorganic materials include aluminum oxide, quartz, silicates, cements, boron nitride in the form of coatings, raw material (pellet, liquid, molding compound), semi-finished stock, or fabricated parts.

 

Coating - Coatings are thin films deposited upon materials to add or enhance desired properties. They provide color, conductivity, corrosion resistance, etc.

  

Composite - Composite materials consist of fibers or particulates that are bonded together. They are filled with a reinforcing a resin or ceramic matrix. Composites can also consist of a multi-layered laminate.

 

Dielectric coating (Encapsulant, Conformal, etc.) - Dielectric coatings such as encapsulants are compounds that are used to seal or cover an element or circuit. Typically, encapsulant layers are less than 100 mils thick.

 

Fabricated part / shaped stock - Electrical insulation materials are available as finished or semi-finished shapes such as rods, bars, plates, post insulators, pads, tubes, substrates, or other shapes.

Electrical Insulation and Dielectric Materials

 

Film / sheet - Material is supplied or available in the form of sheets or films. Sheets have a thickness between 0.006" and 0.250" and are 24" inches (609.6 mm) or more in width. Sheets are typically formed to precise thicknesses and/or width requirements.

 

Gap filling sealant / gasket - Gap filling or underfill compounds are used to fill gaps or spaces between two surfaces that are to be bonded or sealed. Flexible sheet materials, as well as sealants or form-in-place compounds (FIP) such as liquid and viscous materials, are used to fill gaps between seams; or on surfaces, to contain fluids, prevent leaks, and prevent infiltration of unwanted material.

  

Grease / gel - Greases, gels and lubricating pastes are thick, high-viscosity products that do not run or flow off surfaces. Greases often consist of oil thickened with a sodium or calcium soap complex, or non-soap thickener. Greases contain extremely small, uniformly-dispersed particles of soap and/or non-soap thickeners in which surface tension and/or other internal forces hold the liquid. Non-soap thickeners are particles of synthetic, inorganic, or organic polymer materials dispersed in liquid lubricants to form greases. "White" or Lithium greases use a lithium soap complex thickener.

 

Hollow / tubular stock - Material is supplied or available in the form of tubes, pipes, or hollow stock with an open internal bore.

 

Industrial fluids - Industrial fluids include lubricants, coolants, metal working fluids, refrigerants, dielectric greases, transformer oils, base oils, and fuel or oil additives.

 

Knitted product - Knitted products consist of continuous fibers that are processed into a knitted structure with either two or three dimensions. Knitting provides a more conformable structure than weaving, which is valuable for contoured surfaces.

 

Lubricant - Industrial lubricants are fluids, oils, greases, waxes, and other compounds designed to reduce friction, binding, or wear, exclude water, or provide other specialized characteristics.

 

Metal working fluid - Metal working fluids are straight oils, soluble oils, semi-synthetic, and synthetic fluids that facilitate a wide variety of operations involving the working or modification of metals by metal removal, forming, or heat treating processes. Metal removal fluids are used in machining or metal cutting, grinding, lapping, and honing operations. They are also used in stamping, forging, drawing, coining, rolling, piercing, cold heading, and wire/bar/rod drawing operations. Metal protecting fluids are used primarily for fingerprint displacing and indoor/outdoor storage. Metal treating fluids are used primarily for metal quenching operations. Drawing and forming fluids are similar or identical in composition to metal cutting fluids, but are used in different ways.

 

Nonwoven product - Nonwoven products are textile or fiber-based materials shaped into mats of randomly oriented fibers, felt, needle punched cloth, spun bound, or meltblown structures.

 

Plate / board (e.g., fiberboard) - Stock products are available in the form of a solid plate, slab, board, or substrate. The board or plate may consist of a ceramic fiberboard product, a dense sintered ceramic plate, or a precast cement bonded slab.

 

Polymer (plastic / elastomer) - Products are polymer-based materials such as a plastics or elastomers in the form of coatings, raw materials (pellets, liquids, molding compounds), semi-finished stock, or fabricated parts.

  

Potting compound - Potting compounds are dielectric resins that are used to fill a container or pocket with the electronic component. The potting compound fills all of the spaces or gaps between the electrical or electronic component and the container. The container or pocket wall remains as part of the product after potting.

  

Powder / grain - Stock products are available in particulate forms such as a powder, abrasive grains, or fused and crushed aggregates.

  

Precursor - Stock or standard products are available in the form of a liquid, solid or gaseous chemical precursor.

  

Rod stock - Stock products are available in the form of a rod or a bar with a round cross-section.

  

Rope / cordage - Products that are made from twisted or braided rope or cordage. Heat-insulating rope or braid is used to provide a thermal seal around doors or other openings in furnace walls.

 

Roving / yarn - Roving is made of tows, untwisted bundles of continuous filaments. Yarn is made of continuous, often plied strands of natural or man-made fibers or filaments.

  

Sleeving / wrap - Sleeves or wraps are flexible, fibrous refractory products for insulating pipes, tubes, ducts, and other process components.

  

Tape - Products are specialized tapes for electrical and electronic applications. Examples include double-sided thermal interface tapes and electrically-insulating or dielectric tapes.

  

Tile - Tile consists of a flat, thin ceramic shape usually with beveled edges for lining or covering a surface. Tile may have square, rectangular, hexagonal, triangular, round or custom shapes. Tiles often have a protective glaze to create a waterproof or water resistance surface. Tile can be smooth and glossy for wall applications, or anti-slip textured with a matt finish for floor applications.

  

Varnish / impregnating resin - Specialized materials are available for applications that require a low viscosity resin or varnish for coil impregnation or Litz wire coating. The resin may infiltrate the coil or electrical device through capillary action, trickle application, or with vacuum assistance.

  

Wafer / substrate - Ceramic products are available as thin substrates and wafers for semiconductor, thin and thick film deposition, and optoelectronic applications. The ceramic material may be a dielectric insulator, a semiconductor, or a semi-insulator. Wafers for semiconductor applications usually consist of round substrates that are precision polished and planarized.

  

Webbing (ribbon / strap) - Products including woven ribbons, webbing, strapping or tape.

 

Woven product - Woven products are used for composite tooling and the formation of structures. Continuous fibers are processed into two or three-dimensional structures by weaving fibers on a loom.

  

Features

  

Electrical Insulation and Dielectric Materials

Electronics / semiconductors - Products are specialized for electronics applications. Examples include semiconductor molding compounds, die bonding compounds, ceramic substrates or wafers, potting or encapsulating compounds, conductive adhesives, and dielectric sealants.

  

Electrical power / HV - High voltage porcelain post insulators, resins, compounds and plastic composites are suitable for electrical power or high voltage applications such as generator or motor assemblies, coil or transformer manufacturing, and switch or circuit breaker insulation.

  

Glaze / protective coating - Products are ceramic or refractory bodies that use or are available with a glaze (fused glass enamel), metallized coating, plastic coating, or other protective coatings. The coating may seal porosity, improve water or chemical resistance, or enhance joining to metals or other materials.

  

Flame retardant / UL 94V-0 rated - The material is flame retardant in accordance with Underwriters Laboratories, Inc. (UL) Flame Class 94V-0, or other equivalent ISO standards. Materials will reduce the spread of flame or resist ignition when exposed to high temperatures, or insulate the substrate and delay damage to it.

  

Metallized / electrode - The ceramic surface is coated with a thin metal layer applied by plating, thin film, fired-on coating, or other process. The coatings maybe continuous or selectively patterned on the surface or thru vias.

  

Applications

Electrical insulation and dielectric materials are used in a variety of applications and industries. Some products are used in electronics or semiconductors, electrical power products or high voltage (HV) applications, glazes and protective coatings, or flame retardant materials. Electrical insulation and dielectric materials may also be metalized or compliant with MIL-SPEC standards.

 

Standards

Single crystal materials and electrical insulation and dielectric materials that meet standards from Underwriters Laboratories, Inc. (UL) are also available.  

 

  • ASTM D6343 - This standard is a compilation of test methods for evaluating properties of thermally conductive electrical insulation sheet materials to be used for dielectric applications.
  • ADS TS324 - Test for Electrical Connectors Insulation resistance.
  • ASTM D1830 - This test method provides a procedure for evaluating thermal endurance of flexible sheet materials by determining dielectric breakdown voltage at room temperature after aging in air at selected elevated temperatures. 

References

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