A ceramic capacitor, also known as a ceramic dielectric vessel or a monolithic capacitor, is a capacitor that uses a ceramic material as a dielectric. Ceramics have the characteristics of high dielectric constant, so that such capacitors can achieve a large capacitance in a small volume. The basic structure of ceramic capacitors consists of two metal electrode layers, usually silver, coated on both sides of the ceramic matrix, and then through high temperature sintering process to make the metal layer and the ceramic tightly combined to form the structure of the capacitor. The exterior of the capacitor will usually have lead wires for easy welding and may be coated with a protective coating or coated with epoxy resin to increase its stability and durability.

Ceramic capacitors are widely used in various electronic circuits, such as decoupling, filtering, bypass, coupling, timing and oscillation circuits, because of their miniaturization, high voltage resistance, good frequency characteristics, low cost and wide selection range of temperature coefficient and dielectric constant. They can have different shape structures, including round sheet, tubular, rectangular, sheet and through-core capacitors, to adapt to the needs of different applications.

Basic knowledge of ceramic capacitors

Different types and applications

Ceramic capacitors are mainly divided into two categories according to their medium characteristics and application needs, namely Class I (Class 1) ceramic capacitors and Class II (Class 2) ceramic capacitors, each class has its specific application.

Class I Ceramic Capacitor (Class 1)

• Dielectric type: This class of capacitors uses ceramic materials with a linear capacitance-temperature coefficient, such as NP0, SL0, COG, etc., which has a low dielectric constant (about 101 to 102 magnitude).

• Features: Extremely high stability, low dielectric loss and a capacitance value that is almost unaffected by temperature, suitable for applications requiring a high degree of stability.

• Applications: High precision filtering, high frequency oscillation circuit, timing circuit, temperature compensation network, high frequency communication equipment and other applications requiring high capacitance stability.

Class II Ceramic Capacitor (Class 2)

• Type of medium: Use ferroelectric ceramic materials with nonlinear capacitance-temperature coefficient, such as X7R, X5R, Y5U, Y5V, etc., with high dielectric constant (order of 103 to 104).

• Features: It has a high capacitance density, which means that a larger capacitance value can be obtained in the same volume, but the capacitance value varies greatly with temperature, voltage and time.

• Applications: coupling, decoupling, filtering, bypass, energy storage, etc., do not require high capacitance accuracy, but require high capacitance value applications. Commonly found in power filters, audio equipment, household appliances, switching power supplies and general electronic equipment.

Other categories and applications

• Shape and package: Ceramic capacitors come in a variety of shapes and packages, including round sheet, tubular, rectangular, sheet (SMD patch type) and through-core capacitors, suitable for different types of circuit board design and installation requirements.

• Voltage level: According to different operating voltage requirements, ceramic capacitors are divided into high voltage and low voltage types, suitable for different voltage levels of circuit applications.

• Special applications: Some ceramic capacitors are designed for specific extreme environments or performance requirements, such as high heat resistance, high frequency, low ESL (equivalent series inductance) and low ESR (equivalent series resistance), etc., to meet the needs of professional fields.

Structure, manufacturing materials and technology

Ceramic capacitor consists of ceramic dielectric sheet, internal and external electrode layer on layer, after high temperature sintering. The electrode material is mostly silver-palladium alloy to ensure good electrical conductivity and oxidation resistance. The manufacturing process involves several steps such as fine ceramic powder preparation, multi-layer overprinting, cutting, electrode sintering, etc., which requires very high process control.

Common faults of ceramic capacitors and their causes

Why does ceramic capacitor overvoltage breakdown?

Ceramic capacitor overvoltage breakdown mainly occurs when the voltage under the capacitor exceeds its rated voltage limit. In this case, the electric field strength exceeds the maximum value that the dielectric material can withstand, resulting in partial discharge of the dielectric layer, which leads to dielectric breakdown and permanent damage to the capacitor.

Why do ceramic capacitors with large capacity make a sound when applying voltage (piezoelectric effect explained)?

Large capacity ceramic capacitors may sound due to piezoelectric effect when voltage is applied. The piezoelectric effect refers to the fact that certain materials produce electrical charges when subjected to mechanical stress, and vice versa. When a voltage is applied to a capacitor, a small deformation of the dielectric material produces sound waves, which produce sound. This phenomenon is more significant in capacitors with high capacitance values, because they usually use ceramic materials with stronger piezoelectric properties.

What are the problems of using monolithic ceramic capacitors over rated voltage?

If monolithic ceramic capacitors exceed the rated voltage, the first thing they face is the risk of overvoltage breakdown, which may lead to immediate capacitor failure. In addition, long-term overload may also accelerate the aging process of the capacitor, reduce the service life, and even cause damage to other components in the circuit.

What is the difference between ceramic capacitor and monolithic capacitor and can it be used interchangeably?

Although ceramic capacitors and monolithic capacitors belong to the category of ceramic capacitors, there are some differences in structure, performance characteristics and application scenarios. Here are the main differences between them and considerations for their interchangeability:

The difference:

1. Structure:

Ceramic capacitor is usually made of a layer of ceramic dielectric plate coated with metal film (such as silver) and sintered, and its structure is relatively simple.

Monolithic capacitors (also known as multi-layer ceramic capacitors, MLCC) consist of multiple layers of ceramic media and metal internal electrodes, which are alternately stacked and sintered into a whole through high temperature, so that higher capacitance can be achieved at the same volume.

2. Size and capacity:

• Monolithic capacitors, due to their multi-layer structure, are able to achieve greater capacitance in a smaller volume, and the size is usually smaller than that of a chip capacitor of the same capacity.
• Chip capacitors are relatively low in capacity, but their size and voltage rating may be more flexible.

3. Stability and accuracy:

• Monolithic capacitors usually have higher stability and accuracy because of their structure and materials, and are suitable for occasions where the stability and accuracy of the capacitance value are required.  
• Chip capacitors may be slightly less stable, but they perform well in high-frequency applications.

Frequency response and application:

Monolithic capacitors are suitable for high frequency circuit applications due to their high quality factor and wide frequency response range.

Ceramic capacitors also have good high-frequency characteristics and are suitable for high-frequency oscillation, resonance, decoupling and other circuits.

Is it interchangeable:

• In the case of low requirements, the ceramic capacitor and the monolithic capacitor can be used interchangeably. For example, if the circuit design does not require high accuracy and stability of the capacitor, and the operating frequency is less than 1MHz, the two can be replaced if the capacity and voltage withstand conditions are met.

• In high frequency circuits or applications requiring higher accuracy, it is best to use monolithic capacitors because their performance is superior, especially in terms of stability, high frequency response and accuracy.

• Taking into account space limitations, if the design space is sufficient, and the performance requirements of the capacitor are not particularly strict, the ceramic capacitor can be replaced with a monolithic capacitor, and vice versa, but pay attention to the physical size and installation of the capacitor.

Fault treatment of ceramic capacitors

How to deal with the sudden stop of ceramic capacitor insurance?

When the fuse is blown due to the fault of the capacitor, first disconnect the power supply and use a multimeter to check whether the capacitor has short circuit or leakage phenomenon. After confirming the fault, replace the new capacitor with the same specification, and check whether there is the root cause of overvoltage or overcurrent in the circuit to avoid repeated failures.

How to detect and deal with the problem of voltage series tripping?

Voltage series trip is usually due to the existence of a short circuit or leakage in the capacitor in the circuit, resulting in an abnormal increase in current. When processing, the capacitors in series should be detected one by one, and the actual capacitance value and loss Angle tangent value should be measured using a bridge or a professional capacitance tester, and the faulty capacitor should be found and replaced.

What emergency measures should be taken if ceramic capacitors burn and catch fire?

Once a burning capacitor is found, the first priority is to quickly cut off the power supply, use a dry powder fire extinguisher or a carbon dioxide fire extinguisher to extinguish the flame, and avoid the use of water to prevent the risk of electric shock. Then, it is necessary to thoroughly check whether the circuit design and capacitor selection are wrong, and ensure safety before restarting the system.

Defect causes and solutions of ceramic capacitors

Common causes of defects in ceramic chip capacitors

Including PCBA (printed circuit board assembly) bow bending deformation, pad design asymmetry, thermal expansion coefficient mismatch. Solving these problems requires optimizing PCB design, ensuring uniform and symmetrical solder joints, and selecting capacitor materials that match the thermal expansion coefficient of the board.

Solve the failure caused by assembly stress, thermal shock and mechanical vibration

Using flexible circuit board design, increasing buffer materials and improving packaging technology can effectively reduce the negative impact of these external factors on capacitors.

Failure and reliability analysis of ceramic capacitors

Effect of temperature shock and mechanical stress on capacitance

Extreme temperature changes can cause the material inside the capacitor to expand and shrink unevenly, leading to cracks; Mechanical stress can cause physical damage during welding or transportation. Improving the design standards of capacitors, such as using high-temperature resistant materials and strengthening structural design, is a key countermeasure.

Protection against inrush current

The surge current will reduce the insulation of the capacitor, by adding a transient voltage suppression diode (TVS) or varistor protection element in the circuit, can effectively absorb the overvoltage, protect the capacitor from damage.

Use and maintenance of ceramic capacitors

Can expired ceramic capacitors still be used?

The expiration date of the capacitor mainly affects the consistency of its initial performance, and the expired capacitor does not mean immediate failure, but the performance may decline. It is recommended to avoid using expired products in critical applications.

Correct storage conditions

Should be stored in a dry, ventilated, non-corrosive gas environment, temperature control between -25°C and +35°C, humidity does not exceed 60%RH, avoid direct sunlight.

Common ceramic capacitor material types and characteristics

• Y5V: Low cost, high capacity, but large capacitance drift when the temperature changes.

• X5R: Moderate cost, slightly lower capacity than Y5V, better temperature characteristics.

• X7R: Good temperature stability, small capacity change, suitable for stabilizing the circuit.

• NPO/CC1: High stability, low loss for high frequency, high precision applications.