ECIA 521

INTRODUCTION

Ceramic capacitors are those wherein the dielectric material -isa high-temperature, sintered, inorganic compound. As a generalrule, these materials are based on mixtures of complex titanate orniobate compounds, including barium titanate, calcium titanate,strontium titanate, etc. Stannate and zirconate compounds are alsoused. Because of the great variety of electrical characteristicsfound in ceramic capacitors, the Electronic Industries Association(EIA) has categorized ceramic capacitors into four classes.

Class I capacitors are those of the stable andtemperature-compensating type. They are available in a wide rangeof temperature coefficients (TC) with relatively linearcharacteristics. They are suited for applications where low-lossesand high-stability are required. The capacitance ranges availablein Class I are much lower than in the other classes.

Class II capacitors are typically more complex in formulation.They may be ferroelectric compounds, often based on barium titanatepossessing a high dielectric constant. They are classified ashaving a semistable temperature characteristic and used over a widetemperature range.

Class III capacitors are also typically based on more complexformulations. Class III capacitors have the highest dielectricconstant of all ceramic capacitors. They are the mostvolumetrically efficient of the standard ceramic dielectric types.They are used over a moderate temperature range in applicationswhere high capacitance is required,but where moderate losses andcapacitance changes can be tolerated.

Class IV capacitors are restricted to reduced titanate orbarrier layer dielectrics. These capacitors have the highestapparent dielectric constant. The high dielectric constant isdeveloped by creating a thin reoxidized dielectric layer, a PNsemiconductor junction, and/or a thin intergranular insulatinglayer. They exhibit the same TC characteristics as the oxidizedceramic formulation

All class of ceramic capacitors are available in a variety ofphysical forms, ranging from disc or rectangular single layer tomultilayer types. Tubular types, feedthrough styles, or variationsof these are also produced. In all their variations, ceramicdielectric capacitors are used more than any other singledielectric family. High usage is the result of low cost, wide rangof characteristics, good volumetric efficiency, excellenthigh-frequency capabilities, and inherent reliability.

Edition:

93

Published:

11/01/1993

ANSI:

ANSI Approved

Number of Pages:

27

File Size:

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