PP7X (PP78A & PP78R)

This natural mineral insulator has outstanding dielectric properties that are ideal for long-life high-stability capacitors with low loss at all frequencies, and high dielectric strength. This type of capacitor is used particularly for high frequency and delay line applications, oscillating circuits, emission devices and calibrators.

Mica dielectric capacitor technology allows for several custom design applications including: 

• High voltage capacitors (up to 50 kV)
• High temperature capacitors (up to 250°C)
• Precision capacitors (up to ± 0.1%)
• High stability capacitors (– 20 + 30 ppm/°C)
• High frequency capacitors ( up to several GHz). 

The majority of these capacitors are manufactured to comply to specifications NF-C-83120;MIL-C-5 and MIL-PRF-39001 standards.

Mica capacitors are noted for the following characteristics:

• Temperature performance
• Low loss at all frequencies
• High dielectric strength
• Stability over time

Silver mica capacitors provide superior stability and low loss when used in RF power circuits that require low pico farad (pF) and nano farad (nF) ranges. Older silver mica capacitors were manufactured in layers of mica and silver, but the layering allowed room for air gaps that reduced the stability and could also create stress fractures in the assembly.

Modern manufacturing uses silver plated to mica layers, eliminating the gaps. When the desired number of layers is obtained, the assembly is coated in an epoxy or ceramic resin. The coating reduces fracturing of the layers and seals the assembly from moisture and particles that could interfere with the capacitance value.

Mica capacitors are useful in circuits for ripple filtering and are often found in time constant, coupling or resonance circuits. In addition to radio circuits, they are used in TV transmitters and Cable TV amplification circuits. Mica is also a superior choice in high-voltage inversion and power conversion for energy absorbing snubber applications with capacitances of up to 10 nF.

Standard silver mica capacitors are normally designed to handle voltages from 100 to 1000 volts. High-voltage RF transmitter applications can call for higher tolerances. Mica capacitors are available for voltages up to 20kV.

Our expert engineering team can create the mica capacitor with the characteristics you require. Send us your drawing or file and we will work with you to manufacture the correct size, lead style and capacitance you desire.

Plastics come in such a wide range that they can cater to most of our technical needs. They can be used in high-temperature applications (Teflon), power (polypropylene), energy conversion (polyester), and for functions requiring high stability (polycarbonate). 

The product range extends from capacitor outputs for implementation on printed circuits, to metal housings with terminal output for power capacitors in wired circuits. Surface mounted devices (SMD) and film capacitors withstanding high temperatures are also manufactured.

The metalized film consists of an extremely thin layer (some hundredths μm) of zinc or aluminum deposited by evaporation under vacuum on the dielectric.
The nature, thickness and geometry of the metalized layer modify the properties of the capacitors, especially as far as permissible peak or effective current is concerned.
 

Metalized film capacitors are smaller than film-foil capacitors. 

Self-healing is a fundamental property of these capacitors. When a dielectric breakdown occurs between the metal layers, due to a dielectric failure, an electrical arc causes local vapor deposition of the metallization which results in an insulating metallic oxide. Thus regenerated, the capacitor is once again operational.
 

The self-healing operation generally requires only a very small amount of energy (5 to 15 μJoules) and is performed in several μseconds (< 50). However, a minimu amount of energy is required below which self-healing operations are unpredictable. This energy is calculated in relation to the capacitance value and the load voltage: E = 1 / 2 CV2.

Various dielectrics used have been paper, paper-polyester, polyester, polysulfone, polystyrene, polypropylene, TFE fluorocarbon, polyvinylidene, fluoride, and others.
 

Capacitors have been produced using discrete foil and metalized electrode systems. Impregnants employed include mineral oil, wax, Vitamin Q® silicone
oil and various so-called solid impregnants. 

Capacitor housings include drawn and fabricated metal shells in standard, rectangular, and special shapes, glass and ceramic tubes, cast epoxy housings, molded housings, plastic-film tubes, plastic-film wraps, and epoxy and resin coatings. Where required, special mounting studs and brackets have been furnished.
 

Capacitance tolerances to meet specific applications needs are available within the limits of the capacitor construction. Units with matched capacitor sections, multiple sections of different dielectrics, pulse forming networks, capacitor networks, capacitor standards, or other application specific capacitors, are available to meet your circuit needs.
 

Special paper and film-type capacitors have been provided with capacitance ratings from 0.0001 μF to 2000 μF and with voltage ratings from 30 VDC to 30,000
VDC. Capacitors have been supplied to operate over the temperature range of -65°C to +250°C.

The rigid quality control exercised by Exxelia Electronics Inc. on all its standard production is also applied to custom-fabricated capacitors. Where necessary, special testing is done to verify requirements, such as low dielectric absorption, ultra-high insulation resistance, low dissipation factor, stability under temperature cycling or under specified environmental conditions, etc. If you have the need for special capacitor designs utilizing paper or film dielectrics, Exxelia will be glad to make recommendations on how best to meet your application needs.