Multilayer ceramic capacitors are available in a variety of physical sizes and configurations, including leaded devices and surface mounted chips. Leaded styles include molded and conformally coated parts with axial and radial leads. However, the basic capacitor element is similar for all styles. It is called a chip and consists of formulated dielectric materials which have been cast into thin layers, interspersed with metal electrodes alternately exposed on opposite edges of the laminated structure. The entire structure is fired at high temperature to produce a monolithic block which provides high capacitance values in a small physical volume. After firing, conductive terminations are applied to opposite ends of the chip to make contact with the exposed electrodes. Termination materials and methods vary depending on the intended use.

TEMPERATURE CHARACTERISTICS Ceramic dielectric materials can be formulated with Class III: General purpose capacitors, suitable a wide range of characteristics. The EIA standard for by-pass coupling or other applications in which ceramic dielectric capacitors (RS-198) divides ceramic dielectric losses, high insulation resistance and dielectrics into the following classes: stability of capacitance characteristics are of little or no importance. Class III capacitors are similar to Class I: Temperature compensating capacitors, II capacitors except for temperature characteristics, suitable for resonant circuit application or other appliwhich are greater than � 15%. Class III capacitors cations where high Q and stability of capacitance charhave the highest volumetric efficiency and poorest acteristics are required. Class I capacitors have stability of any type. predictable temperature coefficients and are not affected by voltage, frequency or time. They are made KEMET leaded ceramic capacitors are offered in from materials which are not ferro-electric, yielding the three most popular temperature characteristics: superior stability but low volumetric efficiency. Class I C0G: Class I, with a temperature coefficient 0 � capacitors are the most stable type available, but have 30 ppm per degree C over an operating the lowest volumetric efficiency. temperature range + 125�C (Also known as "NP0"). Class II: Stable capacitors, suitable for bypass X7R: Class II, with a maximum capacitance or coupling applications or frequency discriminating change � 15% over an operating temperature circuits where Q and stability of capacitance charrange + 125�C. acteristics are not of major importance. Class II Z5U: Class III, with a maximum capacitance capacitors have temperature characteristics � 15% change of over an operating temor less. They are made from materials which are perature range + 85�C. ferro-electric, yielding higher volumetric efficiency but less stability. Class II capacitors are affected by Specified electrical limits for these three temperature temperature, voltage, frequency and time. characteristics are shown in Table 1.

Dissipation Factor: Measured at following conditions. � 1 kHz and 1 vrms if capacitance >1000pF 1 MHz and 1 vrms if capacitance � 1 kHz and 1 vrms* or if extended cap range 0.5 vrms � 1 kHz and 0.5 vrms Dielectric Stength: 2.5 times rated DC voltage. Insulation Resistance (IR): At rated DC voltage, whichever of the two is smaller Temperature Characteristics: Range, �C Capacitance Change without DC voltage

ELECTRICAL CHARACTERISTICS The fundamental electrical properties of multilayer ceramic capacitors are as follows: Polarity: Multilayer ceramic capacitors are not polar, and may be used with DC voltage applied in either direction. Rated Voltage: This term refers to the maximum continuous DC working voltage permissible across the entire operating temperature range. Multilayer ceramic capacitors are not extremely sensitive to voltage, and brief applications of voltage above rated will not result in immediate failure. However, reliability will be reduced by exposure to sustained voltages above rated. Capacitance: The standard unit of capacitance is the farad. For practical capacitors, it is usually expressed in microfarads (10-6 farad), nanofarads (10-9 farad), or picofarads (10-12 farad). Standard measurement conditions are as follows: Class I (up to 1,000 pF): Class I (over 1,000 pF): Class II: Class III: 1MHz and 1.2 VRMS maximum. 1kHz and 1.2 VRMS maximum. 1 kHz and � 0.2 VRMS. 1 kHz and � 0.1 VRMS. The variation of a capacitor's impedance with frequency determines its effectiveness in many applications. Dissipation Factor: Dissipation Factor (DF) is a measure of the losses in a capacitor under AC application. It is the ratio of the equivalent series resistance to the capacitive reactance, and is usually expressed in percent. It is usually measured simultaneously with capacitance, and under the same conditions. The vector diagram in Figure 2 illustrates the relationship between DF, ESR, and impedance. The reciprocal of the dissipation factor is called the "Q", or quality factor. For convenience, the "Q" factor is often used for very low values of dissipation factor. DF is sometimes called the "loss tangent" or "tangent as derived from this diagram.

Like all other practical capacitors, multilayer ceramic capacitors also have resistance and inductance. A simplified schematic for the equivalent circuit is shown in Figure 1. Other significant electrical characteristics resulting from these additional properties are as follows:

Insulation Resistance: Insulation Resistance (IR) is the DC resistance measured across the terminals of a capacitor, represented by the parallel resistance (Rp) shown in Figure 1. For a given dielectric type, electrode area increases with capacitance, resulting in a decrease in the insulation resistance. Consequently, insulation resistance is usually specified as the "RC" (IR x C) product, in terms of ohm-farads or megohm-microfarads. The insulation resistance for a specific capacitance value is determined by dividing this product by the capacitance. However, as the nominal capacitance values become small, the insulation resistance calculated from the RC product reaches values which are impractical. Consequently, IR specifications usually include both a minimum RC product and a maximum limit on the IR calculated from that value. For example, a typical IR specification might read "1,000 megohm-microfarads or 100 gigohms, whichever is less." Insulation Resistance is the measure of a capacitor to resist the flow of DC leakage current. It is sometimes referred to as "leakage resistance." The DC leakage current may be calculated by dividing the applied voltage by the insulation resistance (Ohm's Law). Dielectric Withstanding Voltage: Dielectric withstanding voltage (DWV) is the peak voltage which a capacitor is designed to withstand for short periods of time without damage. All KEMET multilayer ceramic capacitors will withstand a test voltage 2.5 x the rated voltage for 60 seconds. KEMET specification limits for these characteristics at standard measurement conditions are shown in Table 1 on page 4. Variations in these properties caused by changing conditions of temperature, voltage, frequency, and time are covered in the following sections.

Impedance: Since the parallel resistance (Rp) is normally very high, the total impedance of the capacitor is:

TABLE 1 EIA TEMPERATURE CHARACTERISTIC CODES FOR CLASS I DIELECTRICS Significant Figure of Temperature Coefficient

* These symetrical tolerances apply to a two-point measurement of temperature coefficient: one at 25�C and one at 85�C. Some deviation is permitted at lower temperatures. For example, the PPM tolerance for / -72 PPM.