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MLCC Property Definitions

Capacitance and Tolerance
A capacitance is the electric capacity of a capacitor, i.e. the amount of electrically charged carriers it can store. Tolerance is the permissible relative deviation of the capacitance from the rated value.

Dielectric Materials
The choice of dielectric material is usually determined by the required capacitance-temperature stability. Class I capacitors or temperature compensating capacitors have predictable temperature coefficients and in general do not have an aging characteristic. The most popular class I multiplayer ceramic capacitors are COG (NP0) temperature compensating capacitors. EIA Class 2 capacitors typically are based on the chemistry of barium titanate and provide a wide range of capacitance values and temperature stability. The most commonly used Class 2 dielectrics are X7R and Y5V.

Working Voltage (WV)
The working voltage is the maximum continuous voltage that should be applied to a capacitor. The capacitor is designed for a particular working voltage, which it must stand up to without adverse effect during continuous operation. Rated voltages for DC and AC operation are usually not the same.

Temperature Coefficient (T.C.)
The temperature coefficient shows the fraction by which the capacitance changes with temperature expressed as parts per million per degree centigrade (PPM/C), or as a percent change over a specified temperature range. TC can be positive or negative.

Dissipation Factor (D.F.)
The dissipation factor loss tangent is the quotient of the active and reactive components of the impedance. DF is the measurement of dielectric losses and is dependent on temperature and frequency. Dielectric loss is the result of the changing polarization of the dielectric caused by alternating fields. They are transformed into oscillations and thus produce frictional heat.

Insulation Resistance (I.R.)
Insulation resistance is a measure of the resistance to a DC current flow through the capacitor under steady state conditions. Good insulation resistance is necessary for capacitors which are used to block off DC voltage and for storage capacitors in which a particular voltage rate has to remain unchanged for a longer period of time.

Equivalent Series Resistance (ESR)
ESR is a measure of all losses both series and parallel in a capacitor at a given frequency so that the equivalent circuit is reduced to a simple R-C series connection.

Dielectric Strength
Dielectric strength is an expression of the ability of a material to withstand an electrical stress. Although dielectric strength is usually expressed in volts, it is actually dependent on the thickness of the dielectric and thus is also a more generically a function of volts/mil.

Capacitor Classifications

Multi-layer ceramic capacitors are available in wide range of characteristics. Electronic Industries Association (EIA) and the military have established categories to help divide the basic characteristics into more easily specified classes. The basic industry specification for ceramic capacitors is EIA RS-198 and as noted in the general section, it specifies temperature-compensating capacitors as Class I Capacitors. These are specified by the military under specification MIL-C-20. General Purpose capacitors with non-linear temperature coefficients are called Class II Capacitors by the EIA and specified by the military under MIL-C-11015 and MIL-C-39014. The new high reliability military specification, MIL-C-123 covers both Class I and Class II dielectrics.

Class I
Class I Capacitors or temperature-compensating capacitors are usually made from mixtures of titanates where barium titanate is normally not a major part of mix. They have predictable temperature coefficients and in general, do not have aging characteristics. Thus they are the most stable capacitors available. Normally the T.C.s of Class I temperature-compensating capacitors are NPO (± 30 PPM/°C)

Class II
General Purpose ceramic capacitors are called Class II Capacitors and have become extremely popular because of the high capacitance values available in very small sizes. These capacitors are ferroelectrics and vary in capacitance value under the influence of the environmental and electrical operating conditions. Class II Capacitors are affected by temperature, voltage, frequency and time. Temperature effects for Class II ceramic capacitors are exhibited as non-linear capacitance changes with temperature. Industry standards for Mid-K dielectrics, such as X7R and High-K dielectrics, such as Z5U and Y5V are defined as Class II formulations.

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