A Basic Description of Ceramic Capacitors

Ⅰ. The definition of ceramic capacitors

Ceramic capacitors are capacitors with ceramic dielectric as the dielectric material. Ceramic is a well-known insulator and was one of the first materials used to make capacitors. Ceramic capacitors come in a variety of geometries, some of which have been eliminated due to size, parasitics, or electrical characteristics, such as ceramic tubular capacitors and barrier capacitors. Multilayer ceramic capacitors (MLCC) and ceramic disc capacitors are two of the most widely used types of ceramic capacitors in modern electronics.

Ⅱ. The history of ceramic capacitors

In 1900, Italian Lombardi invented ceramic dielectric capacitors. In the late 1930s, he discovered that the dielectric constant could be multiplied by adding titanates to the ceramic, thus creating less expensive ceramic capacitors.

Around 1940, people discovered that the main raw material of ceramic capacitors, BaTiO3, was insulating, and they began to use ceramic capacitors for small and extremely high military electronic equipment.

Around 1960, ceramic laminate capacitors became commercially available.

By 1970, with the advancement of hybrid ICs, computers, and portable electronic equipment, ceramic capacitors also developed rapidly and became an indispensable part of electronic equipment. Ceramic dielectric capacitors currently account for about 70% of the total capacitor market.

Ⅲ. The working principle of ceramic capacitors

Ceramic capacitors are made by extruding high dielectric constant capacitor ceramic materials such as barium titanate and titanium oxide into round tubes, discs or discs as the medium, and then plating silver on the ceramics as electrodes by firing infiltration. It is divided into high-frequency porcelain and low-frequency porcelain, because the capacitance is directly related to the dielectric constant. On the positive side of the electrolyte, the thickness of alumina is set smaller than that of ceramic material, so we can get higher capacitance density. A capacitor is a container that can store electricity. Its basic principle is to use air or other materials as an insulator between two parallel metal sheets.

We connect a piece of metal to the positive terminal of the battery and another piece to the negative terminal, and the metal can store charge. This kind of device that can store electric charge is called a capacitor. Capacitor capacity is proportional to the area of the metal sheet, inversely proportional to the distance between the two metal sheets, and related to the dielectric constant of the insulator between the two metal sheets.

Low-frequency ceramic capacitors are used to bypass or block DC in occasions that do not require high stability and loss or in circuits with low operating frequencies. It is easily broken down by pulse voltage, so it cannot be used in pulse circuits.

Ⅳ. The role of ceramic capacitors

1. Rectification

It refers to turning on or off a semi-closed conductor switching element, such as a transistor or a thyristor, within a predetermined time to switch the polarity of direct current and control the flow and flow of power. This technology is widely used in the fields of power electronics, motor drive and power conversion, and realizes efficient, stable and controllable power transmission and utilization. Through rectification, we can convert alternating current into direct current to meet the power needs of various electronic devices.

2. Timing

Capacitors are used in conjunction with resistors. The time constant of the circuit is an important parameter for charging and discharging the capacitor. It determines the speed and duration of the circuit's response. The larger the time constant, the slower the response and the longer it takes for the circuit to reach steady state. Therefore, in the design of timing circuits, we need to select appropriate capacitors and resistors according to specific application requirements to achieve the desired timing effect.

3. Energy storage

Energy storage is the storage of electrical energy. For example, camera flashes, heating equipment, etc. all need power support. Now the energy storage level of some capacitors is almost the same as that of lithium batteries. The energy stored in a capacitor can even be used by a mobile phone for a whole day.

4. Filtering

For DIY enthusiasts, it is very important to understand the basic principles of electronic equipment and the functions of components. On graphics cards, capacitors play a crucial role. Capacitors are components in electronic devices that store electrical energy, maintain a steady current flow, and provide the required power. Therefore, choosing the right capacitor and understanding its effect on the graphics card are crucial to building an efficient and stable DIY computer.

5. DC blocking

It can block the passage of direct current and allow the passage of alternating current. It can effectively isolate the DC component in the power supply and protect the circuit from damage caused by DC current. In various power applications, DC blocking components ensure circuit stability and safety.

6. Coupling

As a connection between two circuits, it allows AC signals to pass and be transmitted to the next stage of the circuit. This connection mode can ensure the integrity of the signal, and can realize the stable transmission of the signal. In electronic systems, coupling is very important because it can make the whole system more stable and reliable. Different coupling methods have different characteristics and applications, and a suitable coupling method needs to be selected according to specific requirements.

7. Tuning

Tuning is the process of making systematic adjustments to a frequency-dependent circuit. This involves fine frequency matching of the electronic components in the device to ensure proper operation and optimum performance. In electronic products such as mobile phones, radios, and televisions, tuning is a very important link. By tuning, we can ensure that these devices are receiving and sending signals accurately, allowing us to hear or see audio and video content clearly. In the tuning process, we need to use professional tools and techniques to fine-tune the electronic components in the circuit to achieve the best frequency matching effect. This work requires a high degree of professional knowledge and skills to ensure the performance and stability of the equipment.

8. Temperature compensation

Temperature compensation is an electronic technique used to account for the effects of insufficient adaptation of other components to temperature. It improves the stability and performance of the circuit by adjusting the parameters of the components in the circuit to achieve compensation for temperature changes. Temperature compensation technology is widely used in various electronic equipment, such as communication equipment, computer, industrial control and other fields.

9. Suppression of excess capacitance

It is precisely because the capacitor is a product that stores electrical energy, so in the circuit, it can easily remove those short excess pulse signals, and then absorb the excess electricity generated by the voltage fluctuation in the circuit to form a new circuit.

10. Bypass (decoupling)

It provides a low impedance path for some parallel components in the AC circuit. In the circuit design, the function of the bypass capacitor is to effectively reduce the interference and influence of the power supply on the signal and ensure the stable transmission of the signal. In addition, the bypass capacitor can also reduce the internal resistance of the power supply, reduce the energy loss inside the power supply, and improve the stability and reliability of the circuit. Therefore, in electronic equipment, bypass capacitors are widely used. It is one of the important components to ensure the normal operation of equipment and stable signal transmission.

Ⅴ. The failure mechanism of ceramic capacitors

Multilayer ceramic capacitors have high reliability and can be used stably for a long time. But if there are defects in the device itself or introduced in the assembly process, it will have a serious impact on its reliability. The common failure mechanisms of ceramic capacitors are as follows:

1. Dielectric breakdown

Dielectric breakdown may be caused by an overvoltage condition or by an incoming defect in the capacitor itself.

2. Cracks caused by temperature shock and mechanical stress

Temperature shock mainly occurs during the capacitor welding process, and improper repair is also an important cause of temperature shock cracks. Multilayer ceramic capacitors are characterized by being able to withstand large compressive stresses, but have poor resistance to bending. Any operation that may cause bending deformation of the capacitor during the assembly process may lead to cracking of the capacitor.

Common sources of stress are: different expansion coefficients between ceramic capacitors and printed circuit board materials; mechanical bending of printed circuit boards; assembly-induced stress and mechanical shock or vibration.

The effects of mechanical fracture in ceramic capacitors will take time to show up. For example, if a ceramic capacitor breaks due to board bending. Then when the bending force is removed, the ceramic capacitor will return to its normal position, which may not cause significant electrical degradation. However, the two polar plates of ceramic capacitors are inserted in parallel and staggered, as long as there is a slight misalignment, it will cause increased leakage or short circuit.

3. Inrush current

Excessive current exceeds the instantaneous power dissipation capacity of the local area of the medium, which will cause thermal runaway and cause the capacitor to burn out.

4. Defects of the incoming material itself

(1) Layered

The sintering process of multilayer ceramic capacitors is to stack multiple layers of materials together for high-temperature co-firing, and the sintering temperature is as high as 1000°C. If the sintering process is not good, it is easy to cause delamination. Delamination, like voids and cracks, is an important inherent defect of multilayer ceramic capacitors, which will adversely affect the performance of capacitors.

(2) Holes in the ceramic medium

Voids in the dielectric can easily lead to leakage and reduce the dielectric strength. Leakage can easily lead to local overheating in the capacitor. Due to the positive feedback of thermoelectricity, the insulation performance of the ceramic dielectric is further reduced, resulting in an increase in leakage at this position of the capacitor. This process occurs cyclically and keeps deteriorating, which may lead to parameter drift of the capacitor (decrease of insulation resistance, increase of loss, etc.), or lead to dielectric breakdown of the capacitor, so that the current at both ends of the capacitor is too large, which may cause explosion or even combustion, etc. Serious consequences of overheating and burning.

Ⅵ. How to test ceramic chip capacitors

Ceramic disc capacitors are units used in the computer industry to control voltage for various dielectric functions. The ceramic layer is designed to dissipate the heat generated by the high voltage while protecting the internal and external environment from damage. Volumetric efficiency is inversely proportional to the stability and accuracy of these capacitors, making testing difficult.

Step 1: Ceramic capacitors must be tested as they will short out if exposed to high voltage. If this happens, your display may flicker or go blank. This problem can be solved by removing all ceramic capacitors. Ceramic capacitors, on the other hand, can be tested if you have the right tools.

Step 2: If you are measuring ceramic capacitors, use a wireless multimeter. Capacitors work properly when the voltage is constant. However, if the output of the ohmmeter and the digital capacitance do not match the voltage of the capacitor, you will not be able to calculate it accurately. Therefore the second option is preferable.

Step 3: Use an analog insulation tester if you want to locate a short circuit or evaluate a condition where an optical capacitance meter fails to produce a shortened reading. For a 12V output, set the analog meter to 10 KΩ. Ceramic capacitors to be tested require this stage. If you do want to stop removing the capacitors and test on the board, you can also use both methods to improve measurement accuracy.