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Cap, IR and DF versus Temperature Graph
The following chart graphically displays:
- Capacitance versus Temperature
- Insulation Resistance versus Temperature
- Dissipation Factor versus Temperature
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Mica Paper and Mylar Film Information
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Mica Paper |
Reconstituted Mica Paper Information
The dielectric material used in the design and construction of mica paper capacitors is reconstituted mica paper, which is impregnated with a polymer resin, i.e., polyester, epoxy, or silicone. The "National Electrical Manufacturers Association" defines mica paper as flexible, continuous, and uniform layers of mica reconstituted into a paper-like, electrical insulating material composed entirely of small, thin, overlapping flakes or platelets, which have sufficient strength to be self-supporting and capable of being wound into roll form for commercial use. Capacitor grade mica paper does not contain binders, adhesives, foreign matter, or coloring agents, and is substantially free of any substance that will adversely affect its performance.
Capacitor-grade reconstituted mica paper is manufactured from natural muscovite mica (K2 Al4 [Si6 Al2 O20] (OH, F)4). This mica is subjected to a process in which it is heated to approximately 870°C. This heat causes the mica crystal to partially dehydrate and release a portion of the water which is bonded naturally in the crystal. When this occurs, the mica partially exfoliates, resulting in smaller particles. The heated mica is then quenched in a mild alkaline solution, cooled, drained, and subjected to a weak sulfuric acid solution. The chemical reaction between the caustic and the acid generates a gas between the laminae, which causes the mica to expand greatly. The mica is then ground to produce small particles. The mica is screened in the presence of large amounts of water on separating screens to select the desired particle size distribution to produce the paper desired. This "pulp" is then transferred to a specially modified paper machine for sheet forming and drying. The particular design of the head box and drying belts and/or drums are generally proprietary to the individual mica paper manufacturers. The van der Waals' forces between the crystal surfaces of the mica platelets in close proximity hold the layer together. Reconstituted mica paper can range in thicknesses from 12.7 µm (0.0005") to 50.8 µm (0.002").
Mylar Film Information
CEI uses high-quality Type C (capacitor grade) Mylar Film to produce a variety of Mylar Film capacitors. Mylar film is produced from high-quality polyester resins under very controlled conditions. Consequently, it has outstanding dielectric, electrical, and physical properties. Various thicknesses are available for the voltage rating of the capacitor. This material is readily available and is an excellent choice for high-voltage capacitors. Capacitors that are produced with Mylar film are generally rated for use up to 85°C. If you have any questions about the dielectrics that are available for our high-quality, high-reliability capacitors, please contact our sales department or visit our directory for a complete listing of our International Sales Representatives.
Note: Mylar is registered trademark of the E.I. Dupont Corporation
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Automatic Film
Winder |
PTFE Film Information
The dielectric material used in the design and construction of PTFE film capacitors is tetrafluoroethylene (TFE) film. This type of film can be manufactured with several basic processes: casting, extrusion, or skiving, that is, shaved continuously from the surface of a cylindrical block of molded resin. Casting is the preferred process for the thin, multilaminar TFE film that is used in CEI's lower voltage high temperature capacitor products. The casting process includes deposition of extremely small particles of TFE (average diameter is approximately 0.2 µm) from an aqueous suspension to form a continuous thin film on a belt, heating and sintering, and fusing at temperatures > 370°C. The casting process provides uniform tensile strength and elongation in linear and transverse directions, and a smooth surface profile. TFE film can be metalized by vacuum depositing pure aluminum on one surface. TFE can range in thicknesses from 6.3 µm (0.00025") to 127.0 µm ( 0.005").
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Electrical Tape
Various adhesive-backed electrical tapes are used at CEI as an outer layer of insulation on the "wrap and fill" capacitors. Polyester film, glass cloth, or polyimide film can be selected for each application.
Polyester Film Electrical Tape
Acrylic or thermosetting rubber adhesives can be selected for the polyester films. The adhesive-backed polyester films are UL-recognized for use at temperatures not to exceed 130°C. The acrylic-backed polyester film meets the flame retardancy requirements of UL 510. The thermosetting rubber-backed polyester film meets the requirements of MIL-I-15126F (Type MFT-3.5). CEI has traditionally used yellow polyester tapes. The acrylic-backed polyester tape is also available in white, blue, green, black, or red. If you need a different color, let us know.
Glass Cloth Electrical Tape
The glass cloth tape has a thermosetting rubber adhesive backing and is UL-recognized for use at temperatures not to exceed 150°C. It meets the requirements of MIL-I-15126F (Type GFT).
Polyimide Film Electrical Tape
Various adhesive-backed electrical tapes are used at CEI as an outer layer of insulation on the "wrap and fill" capacitors. Polyester film, glass cloth, or polyimide film can be selected for each application. The polyimide film tape has a silicone adhesive backing, has an operating temperature of 180°C, is recognized by Underwriters Laboratory (UL) and the Canadian Standards Acceptance (CSA) Program, and meets the requirements of MIL-P-46112 (Type 1).
If you have any questions about the types of electrical tapes that are available for our high-quality, high-reliability capacitors, please contact our sales department or visit our directory for a complete listing of our International Sales Representatives.
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Aluminum Foil |
Capacitor-Grade Aluminum Foil
The foil used in the design and construction of our reconstituted mica paper capacitors and PTFE film capacitors is capacitor grade aluminum foil. This type of foil conforms to ASTM B373. CEI uses foil thicknesses that typically range from 5.0 µm (0.0002") to 12.7 µm (0.0005"). Other types of foil, including tin, can also be used.
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Solder Information
Soldering:
As defined by ANSI J-STD-001B, almost all of CEI's high-voltage capacitors, assemblies, and modules are categorized as Class 3 products (High Performance Products). Therefore, they require high-quality solder joints and connections, each of which requires the selection and use of the appropriate electronic grade solder. The solder alloys used at CEI comply with ANSI J-STD-006 and include various types of eutectic solders, high-temperature solders, and solder pastes. CEI's Design Engineers will be happy to work with you to develop soldering hierarchies for your special application.
Flux:
As defined by ANSI J-STD-001B, almost all of CEI's high voltage capacitors, assemblies, and modules are categorized as Class 3 products (High Performance Electronic Products). Therefore, they require high quality solder joints and connections, each of which requires the selection and use of the appropriate flux. The rosin-based fluxes that are used at CEI comply with ANSI J-STD-004. Various types of flux, for example, ROL0, ROL1, are available for your application. CEI's design engineers will be happy to work with you to select the appropriate solder and flux for your special application.
Pretinning / Tinning:
CEI pretins/tins many types of wires, leads, and terminals used in the fabrication of our capacitors, assemblies, and modules. Our experienced and highly skilled equipment operators take pride in their ability to precisely pretin or tin each part with advanced ultrasonic solder pots, dynamic flow solder pots, and traditional solder pots. A variety of solders that comply with ANSI J-STD-006 are used for these processes. You can easily specify the type of solder for your tinned wires, leads, terminals or you can contact our Sales Dept. for assistance.
Resistance Spot Welding:
As defined by ANSI J-STD-001B, almost all of our high-voltage capacitors, assemblies, and modules are categorized as Class 3 products (High Performance Electronic Products). Therefore, they require high-quality solder joints and connections. One of the joining techniques CEI uses is a resistance spot welding process (letter designation RSW as defined by ANSI/AWS A3.0). This includes the use of two opposing electrodes that contact the metals to be joined and resistance heating them to produce a spot weld, which creates a high strength bond. Our technicians are well known for their ability to create high-quality electrical connections that are appropriate for the high-voltage capacitors, assemblies, and modules that we manufacture. If you have any questions about this type of advanced manufacturing process, please contact our Sales Dept. for assistance.
As always, please contact our Sales Dept. if you have any questions about the types of solders, flux, pretinning / tinning or resistance spot welding applications that are available for our high-quality, high-reliability capacitors and modules. For a full listing of our sales representatives, please visit our directory.
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