Basic knowledge of ceramic chip capacitors

Material specifications of ceramic chip capacitors

Currently, chip capacitors use different material specifications such as NPO, X7R, Z5U, and Y5V. Different specifications have different uses. Below we will only introduce the performance and application of the commonly used NPO, X7R, Z5U, and Y5V, as well as the ordering matters that should be paid attention to in purchasing to attract everyone's attention. Different companies may have different naming methods for the above capacitors with different performances. Here we quote the naming method of our company Sanju Electronics. For products of other companies, please refer to the company's product manual.

The main difference between NPO, X7R, Z5U, and Y5V is that they have different filling media. Under the same volume, the capacity of the capacitors composed of different filling media is different, and the dielectric loss and capacity stability of the capacitors are also different. Therefore, when using capacitors, different capacitors should be selected according to the different functions of the capacitors in the circuit.

1. NPO capacitor

NPO is the most commonly used monolithic ceramic capacitor with temperature compensation characteristics. Its filling medium is composed of rubidium, samarium, and some other rare oxides.

NPO capacitors are one of the capacitors with the most stable capacitance and dielectric loss. When the temperature is from -55℃ to +125℃, the capacity changes by 0±30ppm/℃, and the capacity changes with frequency by less than ±0.3ΔC. The drift or hysteresis of NPO capacitor is less than ±0.05%, which is negligible compared with the film capacitor with a value greater than ±2%. The typical capacity changes with the service life by less than ±0.1%. The characteristics of the capacity and dielectric loss of NPO capacitors with different packaging forms are also different. The frequency characteristics of large package sizes are better than those of small package sizes. NPO capacitors are suitable for slot capacitors of oscillators and resonators, as well as coupling capacitors in high-frequency circuits.

2. X7R capacitors

X7R capacitors are called temperature-stable ceramic capacitors. When the temperature is from -55℃ to +125℃, the capacity changes by 15%. It should be noted that the capacity change of the capacitor is nonlinear at this time.

The capacity of X7R capacitors is different under different voltage and frequency conditions, and it also changes with time, changing by about 1%ΔC every 10 years, which is expressed as a change of about 5% in 10 years.

X7R capacitors are mainly used in industrial applications where the requirements are not high and the change in capacitance when the voltage changes is acceptable. Its main feature is that the capacitance can be made larger at the same volume.

Three Z5U capacitors

Z5U capacitors are called "universal" ceramic monolithic capacitors. The first thing to consider here is the operating temperature range. The main thing for Z5U capacitors is its small size and low cost. Among the above three ceramic monolithic capacitors, Z5U capacitors have the largest capacitance at the same volume. However, its capacitance is greatly affected by the environment and working conditions, and its aging rate can reach a maximum of 5% every 10 years.

Although its capacitance is unstable, it has a wide range of applications due to its small size, low equivalent series inductance (ESL) and equivalent series resistance (ESR), and good frequency response. Especially in the application of decoupling circuits.

Other technical indicators of Z5U capacitors are as follows:

Operating temperature range +10℃ --- +85℃

Temperature characteristics +22% ---- -56%

Dielectric loss maximum 4%

Four Y5V capacitors

Y5V capacitors are general-purpose capacitors with certain temperature limits. Their capacitance can vary from +22% to -82% in the range of -30℃ to 85℃.

The high dielectric constant of Y5V allows capacitors up to 4.7μF to be manufactured in a smaller physical size.

Other technical indicators of Y5V capacitors are as follows:

Operating temperature range -30℃ --- +85℃

Temperature characteristics +22% ---- -82%

Dielectric loss maximum 5%

The main characteristic parameters of capacitors:

(1) Capacitance and error: The maximum allowable deviation range between actual capacitance and nominal capacitance. The commonly used capacitance errors are: J grade ±5%, K grade ±10%, and M grade ±20%. The allowable

error of precision capacitors is smaller, while the error of electrolytic capacitors is larger. They use different error grades.

The accuracy grades of commonly used capacitors are expressed in the same way as resistors. Indicated by letters: D-class—±0.5%; F-class—±1%; G-class—±2%; J-class—±5%; K-class—±10%; M-class—±20%.

(2) Rated working voltage: The maximum DC voltage that a capacitor can withstand in a circuit to work stably and reliably for a long time, also known as withstand voltage. For devices with the same structure, dielectric and capacity, the higher the withstand voltage, the larger the volume.

(3) Temperature coefficient: The relative change in capacitance for every 1°C change in temperature within a certain temperature range. The smaller the temperature coefficient, the better.

(4) Insulation resistance: Used to indicate the size of leakage. Generally, small-capacity capacitors have a large insulation resistance of several hundred megohms or several thousand megohms. The insulation resistance of electrolytic capacitors is generally small. Relatively speaking, the larger the insulation resistance, the better, and the smaller the leakage.

(5) Loss: The energy consumed by the capacitor due to heat generation per unit time under the action of the electric field. These losses mainly come from dielectric loss and metal loss. It is usually expressed by the loss tangent value.

(6) Frequency characteristics: The property that the electrical parameters of a capacitor change with the frequency of the electric field. For capacitors working under high frequency conditions, the capacitance decreases accordingly because the dielectric constant is smaller at high frequency than at low frequency. The loss also increases with the increase of frequency. In addition, when working at high frequency, the distributed parameters of the capacitor, such as the electrode resistance, the resistance between the lead and the electrode, the electrode's own inductance, the lead inductance, etc., will affect the performance of the capacitor. All of these limit the frequency of use of the capacitor.

Different types of capacitors have different maximum operating frequencies. Small mica capacitors are within 250MHZ; disc-type ceramic capacitors are 300MHZ; round tube-type ceramic capacitors are 200MHZ; disc-type ceramic capacitors can reach 3000MHZ; small paper capacitors are 80MHZ; medium-sized paper capacitors are only 8MHZ.