Overview: This article overviews ceramic capacitors, highlighting their types, including multilayer and ceramic disc capacitors. It explores its construction, key features, and applications and addresses their challenges.

Ceramic capacitors are one of the most widely used types of capacitors in modern electronics due to their reliability, compact size, and excellent performance characteristics.

What is a ceramic capacitor?

A ceramic capacitor is an electronic component used in electrical circuits to store and release electrical energy that uses a ceramic material as its dielectric. It is a fixed-value capacitor that consists of two or more alternating layers of ceramic and metal electrodes. The composition of the ceramic material defines the electrical behavior and applications of the capacitor. 

It is a passive component that does not amplify or control current flow like active components such as transistors or integrated circuits. Instead, ceramic capacitors temporarily store electric charge and release it when needed.

Classification of Ceramic Capacitor

Ceramic capacitors come in various shapes and sizes, including disc, chip, and leaded styles. The choice of the capacitor depends on the circuits' requirements and the characteristics of the components. Several ceramic capacitors are available the two main types are:

Disc Ceramic Capacitor

As the name implies, the capacitor is placed around a ceramic disc, and the leads are then bonded, as shown in Fig. 1. The overall capacitor is coated to protect it mechanically and from moisture and other contaminants. They are often used as safety capacitors in electromagnetic interference suppression applications.

Fig. 1 Diagrammatic illustration of disc ceramic capacitor. Source: Rakesh Kumar, Ph.D.

Multilayer Ceramic Capacitor (MLCC)

As the name implies, these capacitors use multilayers to achieve higher capacitance levels within a small volume. Capacitance is dependent upon various factors, including the surface area of plates. Hence, using multiple layers, as shown in Fig. 2, within the capacitor makes it possible to increase the level of capacitance, which is a very important factor for surface-mount capacitors. 

Fig. 2 Diagrammatic illustration of multilayer ceramic capacitor structure. Source: MDPI

These capacitors are intended for use within the automated means of production. They are often supplied in reels or contained in a hopper on the placement machine. 

Composition

Many different types of ceramic are available, each having specific properties like high stability, tolerance, and high volumetric capacity. Ceramic capacitors are made from ceramic material, typically composed of a mixture of ceramic and metal, which are layered to produce a sandwich-like structure. The ceramic material acts as the dielectric non-conductive substance that separates the two metal plates within the capacitor. The dielectric materials properties determine the capacitance of the capacitor, measuring its ability to store electrical charge.

Manufacturing Process

The ceramic powder is mixed with a binding material and solvents to form a slurry. The slurry is tape-cast into thin sheets. Multiple layers are stacked and sintered at high temperatures. External electrodes are added, and packaging is done. The manufacturing process is illustrated in Fig. 3.

Fig. 3  Diagrammatic illustration of manufacturing process. Source: MDPI

Key Features of Ceramic Capacitors

They have advantages, including high reliability, low parasitic inductance, and low equivalent series resistance.

  • They are available in various working voltages, from a few volts for transistor design up to kilovolts and even more where high voltages are to be used. Voltage ratings generally range from 16 V to 450 V.
  • MLCCs offer high capacitance values in very small packages, making them ideal for high-density applications. They have high-frequency performance and are used in the microwave region.
  • They are not polarised like electrolytic capacitors and can be oriented either way around in a circuit.
  • They have wide capacitance values ranging from a few pF to 0.1  F or more (typically from 10 pF to 3.3 µF).
  • They provide accurate and stable performance across varying conditions.
  • They can withstand temperatures up to 105° C.

Application

They are known for their small physical size, low cost, and wide range of capacitance values, making them suitable for various electronic applications. They are used for filtering, decoupling, noise reduction, and smoothing out electrical signals and for coupling and blocking direct current in circuits. More commonly, high-tolerant varieties are used in filter and oscillator circuits. They are used in many modern wireless circuit applications. Surface mount types are more commonly used in RF circuits as they offer very low values of unwanted inductance.

Challenges

They have limitations, such as the capacitance variation with temperature and voltage, and are not ideal for high-precision applications. Electrical circuits with higher voltage ratings require larger physical sizes. It has larger temperature coefficient compared to some other capacitor types and higher tolerance values.

A Ceramic Capacitor to Consider

C3225X7S2A475K200AB

The C3225X7S2A475K200AB, as shown in Fig. 4, is a multilayer ceramic capacitor manufactured by TDK Corporation. This capacitor offers specific electrical characteristics and physical properties that make it suitable for various electronic applications.

Fig. 4 The C3225X7S2A475K200AB ceramic capacitor from TDK corporation. Source: oemsecrets

Specifications

  • Capacitance: 4.7 μF
  • Voltage Rating: 100 V DC
  • Tolerance: ±10%
  • Dielectric Type: X7S

The X7S dielectric type indicates that this capacitor maintains its rated capacitance over a temperature range of -55° C to +125° C, with a capacitance change of ±22% or less. These capacitors are known for their superior mechanical strength, high reliability, and monolithic structure.

These features contribute to the capacitor's ability to maintain stable performance in challenging environments and over long periods of operation. Various factors should be considered when designing circuits with this capacitor, including its temperature coefficient, frequency response, and voltage rating factors, to ensure optimal performance for specific applications.

Summarizing the Key Points

  • Ceramic capacitors are widely used in electronics due to their reliability, compact size, and excellent performance, making them essential components in various applications.
  • Multilayer ceramic capacitors offer high capacitance in small packages, are ideal for high-density applications, and are suitable for automated production processes.
  • Applications of ceramic capacitors range from filtering and decoupling to noise reduction and coupling in circuits, making them versatile for modern electronic devices and RF circuits

Reference

Covaci, Corina, and Aurel Gontean. “‘Singing’ Multilayer Ceramic Capacitors and Mitigation Methods—A Review.” Sensors 22, no. 10 (May 19, 2022): 3869.
https://doi.org/10.3390/s22103869

Laadjal, Khaled, and Antonio J. Marques Cardoso. “Multilayer Ceramic Capacitors: An Overview of Failure Mechanisms, Perspectives, and Challenges.” Electronics 12, no. 6 (March 8, 2023): 1297. https://doi.org/10.3390/electronics12061297

oemsecrets - “C3225X7S2A475K200AB - Compare Distributor Prices & Inventory | Oemsecrets.Com.” oemsecrets.com, n.d.
https://www.oemsecrets.com/compare/C3225X7S2A475K200AB