The full name of SMD capacitor is multilayer ceramic capacitor, which is equivalent to insulator and can interrupt DC circuit. SMD capacitor is one of the most commonly used electronic components in SMT processing industry. The SMD capacitors are mainly divided into NPO capacitors, X7R capacitors, Z5U capacitors and Y5V capacitors, etc. The difference between them lies in the different filling media (materials). Under the same volume, the capacitors composed of filling media have different capacities. The resulting dielectric loss and capacity stability of capacitors are different. Therefore, when using capacitors, different capacitors should be elected according to their different functions in the circuit. Then today Xiaobian will explain the internal characteristics of NPO(COG), X7R, Z5U and Y5V capacitors.
1. NPO(COG) capacitor
NPO is the most commonly used monolithic ceramic capacitor with compensation characteristics, and its filling medium is composed of some rare oxides. One of the capacitors with the most stable capacitance and dielectric loss. When the temperature is from -55℃ to 125℃, the capacitance becomes 0 30 ppm/℃, and the change of capacitance with frequency is less than 0.3 △ C. The drift or hysteresis of NPO capacitor is less than 0.05%, and the film capacitor with a relative value of more than 2% can be ignored. The service life change of its typical capacity is less than 0.1%. The capacitance and dielectric loss of NPO capacitors are different according to different packaging forms and different frequency characteristics. The frequency characteristics of large packaging size are better than those of small packaging size.
Second, X7R capacitor
X7R capacitor is called temperature stable ceramic capacitor. When the temperature drops from -55℃ to 125℃, its capacity changes by 15%. It should be noted that the capacity changes of the capacitor are nonlinear at this time. Its capacity is different under different voltage and frequency conditions, and it also changes with time, changing about 1% δ c every 10 years, which shows that it changes about 5% in 10 years.
X7R capacitors are mainly used in industrial applications with low requirements, and when the voltage changes, the capacity changes are acceptable. Its main feature is that the capacitance can be made larger under the same volume. The following table shows the selectable capacity range of X7R capacitor.
Iii. Z5U capacitor
Z5U capacitor is called general ceramic monolithic capacitor. The first thing to consider here is the use temperature range. Z5U capacitors are mainly small in size and low in cost. The Z5U capacitor has the maximum capacitance under the same volume of the above three ceramic monolithic capacitors. However, its capacitance is greatly affected by environment and working conditions, and its aging rate can be reduced by 5% every 10 years.
Although its capacity is unstable, it has a wide range of applications due to its small size, small equivalent series inductance, low equivalent series resistance and good frequency response. Especially in the application of decoupling circuit.
Iv. Y5V capacitor
Y5V capacitor is a general capacitor with certain temperature limit, and its capacity change can reach -82% in the range of -30℃ to 85℃. The high dielectric constant of Y5V allows a 4.7μF capacitor to be fabricated in a smaller physical size.
