Ceramic Capacitor Working, Construction and Applications

The Capacitor is an electrical device that stores energy in the form of an electric field. It consists of two metal plates separated by a dielectric or non-conducting substance. The capacitor types broadly divided based on fixed capacitance and variable capacitance. The most important are the fixed capacitance capacitors, but capacitors with variable capacitance also exist. These include rotary or trimmer capacitors. Capacitors with fixed capacitance are divided into film capacitors, ceramic capacitors, electrolytic, and superconductor capacitors. Follow the link to know more Different types of capacitors. The ceramic capacitor described in more detail in this article.

Different Types Of Capacitors
Different Types Of Capacitors

Ceramic Capacitor Polarity and Symbol

Ceramic capacitors are most commonly found in every electrical device and it uses a ceramic material as the dielectric. The ceramic capacitor is a non-polarity device, that means they do no have polarities. So we can connect it in any direction on a circuit board.

For this reason, they are generally much safer than electrolytic capacitors. Here is the symbol for a non-polarised capacitor given below. Many types of capacitors, such as the tantalum bead do not have a polarity.

Ceramic Capacitor Polarity and Symbol
Ceramic Capacitor Polarity and Symbol

Construction and Properties of Ceramic Capacitors

Ceramic capacitors are available in three types, although other styles are available:

  • Leaded disc ceramic capacitors for through hole mounting which is resin coated.
  • Surface mount Multi-Layer Ceramic Capacitors (MLCC).
  • Special type microwave bare lead-less disc ceramic capacitors that are intended to sit in a slot on the PCB.
Different Types Of Ceramic Capacitors
Different Types Of Ceramic Capacitors

Ceramic disc capacitors are made by coating a ceramic disc with silver contacts on both sides as shown above illustrates. Ceramic disc capacitors have a capacitance value about10pF to 100μF with a wide variety of voltage ratings, between 16V to 15 KV and more.

In order to gain higher capacitances, these devices can be made from multiple layers. The MLCCs are made with Paraelectric and Ferroelectric materials mix and alternatively layered with metal contacts.

After completion of the layering process, the device is brought to a high temperature and the mixture is sintered, resulting in a ceramic material of desired properties. Finally, the resulting capacitor basically consists of many smaller capacitors connected in parallel, this leads to increase in capacitance.

The MLCCs consist of more than 500 layers, with the minimum layer thickness of approximately 0.5 microns. As technology progresses, the thickness of the layer decreases and capacitance increases in the same volume.

Ceramic capacitor dielectrics vary from one manufacturer to another, but common compounds include titanium dioxide, Strontium Titanate, and Barium Titanate.

Based on the working temperature range, temperature drift, tolerance different ceramic capacitor classes is defined.

Class 1 Ceramic Capacitors

With respect to temperature, these are the most stable capacitors. They have nearly linear characteristics.

The most common compounds used as the dielectrics are

  • Magnesium Titanate for a positive temperature coefficient.
  • Calcium Titanate for capacitors with a negative temperature coefficient.

Class 2 Ceramic Capacitors

Class 2 capacitors exhibit better performance with respect to volumetric efficiency, but this is at the cost of lower accuracy and stability. As a result, they are normally used for decoupling, coupling and bypass applications where accuracy is not of prime importance.

  • Temperature range: -50C to +85C
  • Dissipation factor: 2.5%.
  • Accuracy: average to poor

Class 3 Ceramic Capacitors

Class 3 ceramic capacitors offer high volumetric efficiency with poor accuracy and a low dissipation factor. It cannot withstand high voltages. The dielectric used is often Barium Titanate.

  • Class 3 capacitor will change its capacitance by -22% to +50%
  • Temperature range of +10C to +55C.
  • Dissipation factor: 3 to 5%.
  • It will have a fairly poor accuracy (commonly, 20%, or -20/+80%).

Class 3 type are typically used for decoupling or in other power supply applications where accuracy is not an issue.

Ceramic Disc Capacitor Values

Ceramic disc capacitor code normally consists of a three digit number followed by a letter. It is very easy to decode to find the capacitor value.

Ceramic Disc Capacitor Values
Ceramic Disc Capacitor Values

The first two significant digits signify the first two digits of the actual capacitance value, which is 47 (the above capacitor).

The third digit is the multiplier (3), which is ×1000. The letter J implies the tolerance of ±5 %. Since this is the EIA coding system, the value will be in picofarads. Therefore, the value of the capacitor above is 47000 pF ±5 %.

EIA Coding System Table
EIA Coding System Table

For example, if a capacitor is marked as 484N, its value is 480000 pF ±30%.

Applications of Ceramic Capacitors

  • Ceramic capacitors are majorly used in the resonant circuit in transmitter stations.
  • Class 2 high-power capacitors are used in high voltage laser power supplies, power circuit breakers, induction furnaces etc.
  • Surface mount capacitors are often used in printed circuit boards and high-density applications.
  • Ceramic capacitors can also be used as a general purpose capacitor, because of their non-polarity and are available in a large variety of capacitances, voltage ratings, and sizes.
  • Ceramic disc capacitors are used across brush DC motors to minimize RF noise.
  • MLCC used in printed circuit boards (PCB) are rated for voltages from only a few volts up to several hundreds of volts, depending on the application.

From the above information finally, we can conclude that these capacitors employ Ceramic as the dielectric. Due to their non-polarity property, they can connect in any direction on a circuit board. We hope that you have got a better understanding of this concept. Furthermore, any doubts regarding this concept or to implement electronic engineering projects, please give your feedback by commenting in the comment section below. Here is a question for you, what are the different types of Ceramic Capacitor?

2 Comments

  1. Dear sir
    which capacitor gets weaker along with time and could cause damage to the surround components in a printed circuit board..?
    1. Electrolytic cap
    2. Mylar cap
    3. Ceramic cap
    4. Or others ?
    Thank you

    1. Hi Mahien
      I sincerely appreciate your kind response regarding my article
      In aluminium capacitors will induce more leakage current, due to the aluminium oxide layer slowly dissolving into the liquid electrolyte. As this happens, the leakage current of the capacitor can be high, especially when it is first energized. As a result, the part may heat up and, in extreme situations, may experience thermal runaway and failure. Aluminum capacitors that have been in storage for a long time need to be reformed by the application of voltage. This should restore the oxide layer and reduce the leakage current to acceptable levels.Soldering can also be critical to aluminium capacitors. Aluminum SMTs are on the topside of the board and are exposed to heat during the soldering process.

      This heat, which will probably be the highest temperature the capacitor will be exposed to during its lifetime, can induce failures.

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