Ceramic Capacitor - Construction and Styles

Construction and Styles

Ceramic capacitors are composed of a mixture of finely ground granules of paraelectric or ferroelectric materials, modified by a lot of accurate mixes, which are necessary to achieve the capacitor’s desired characteristics, see chapter "Application classes for ceramic capacitors". From these powder mixtures, the ceramic of the capacitor is sintered at high temperatures. The ceramic forms the dielectric of the capacitor and serves as a carrier of the metallic electrodes. The minimum thickness of the dielectric layer, which today (2012) is in the size range of 1 micron or smaller, is limited downwards by the grain size of the ceramic powder. Upwards, the thickness of the ceramic dielectric is determined by the dielectric strength of the desired capacitor. On the ceramic layer, the electrodes of the capacitor are deposited by metallization. For multilayer ceramic capacitors, alternating metallized ceramic layers, as many as necessary, are stacked one above the other. The outstanding metallization of the electrodes at two sides of the body are then contacted with the contacting terminal. A lacquer or ceramic coating protects the capacitor against ambient influences like moisture.

Ceramic capacitors come in various shapes and styles. Some of the most commonly used styles are:

• Multilayer ceramic chip capacitor (MLCC), rectangular block, for surface mounting
• Ceramic disc capacitor, single layer disc, resin coated, with through-hole leads
• Feedthrough ceramic capacitor, with a defined value of capacitance, which is used for bypass purposes in high-frequency circuits. Tube shape, inner metallization contacted with a lead, outer metallization for soldering
• Ceramic power capacitors, larger ceramic bodies in different shapes for high voltage applications