Characteristics and applications of chip capacitors

Characteristics of chip capacitors

(1) The allowable large deviation range between the actual capacitance of the chip capacitor and the nominal capacitance. The generally used capacity errors are: J class ±5%, K class ±10%, M class ±20%, and the allowable precision capacitor The error is small, and the error of electrolytic capacitors is large. They use different error levels. Commonly used capacitors and resistors are expressed in the same way. They are expressed by letters: Class D—±0.5%; Class F—±1%; Class G— ±2%; Class J—±5%; Class K—±10%; Class M—±20%.

(2) The capacitor can work stably for a long time in the circuit. The voltage it bears is called the withstand voltage. For devices with the same structure, medium, and capacity, the higher the withstand voltage, the larger the volume.

(3) Within the temperature range that can be withstood, the temperature coefficient of the relative change of capacitance for every 1°C change in temperature, the smaller the better.

(4) It is used to indicate the magnitude of leakage. SMD capacitors are generally small-capacity capacitors with large insulation resistance. In a few hundred megaohms or several gigaohms, the insulation resistance of electrolytic capacitors is generally small. Relatively speaking, the insulation resistance The bigger the better, the leakage is also small.

(5) Under the action of an electric field, the energy consumed by the capacitor in a unit of time heating, these losses mainly come from dielectric loss and metal loss, usually expressed by the loss tangent value.

(6) The property that the electrical parameters of the chip capacitor change with the frequency of the electric field. For capacitors operating under high frequency conditions, since the dielectric constant is smaller at high frequencies than at low frequencies, the capacitance is also reduced accordingly, and the loss increases with the increase in frequency. In addition, when operating at high frequencies, the distribution of capacitors Parameters, such as pole piece resistance, resistance between lead and pole piece, pole piece's own inductance, lead inductance, etc., will affect the performance of the capacitor. All of these limit the frequency of use of capacitors.

The role of chip capacitors

It is mainly to eliminate the crosstalk of various high-frequency signals generated by the chip itself to other chips, so that each chip module can work normally without interference. In high-frequency electronic oscillation circuits, chip capacitors and crystal oscillators and other components form an oscillation circuit to provide various circuits with the required clock frequency.

Chip capacitors include chip ceramic capacitors, chip tantalum capacitors, and chip aluminum electrolytic capacitors. SMD ceramic capacitors have no polarity and small capacity. They can generally withstand very high temperatures and voltages, and are often used for high-frequency filtering. Ceramic capacitors look a bit like chip resistors, but there is no number representing the size of the chip capacitors.

SMD capacitors are characterized by long life, high temperature resistance, high accuracy, and excellent performance in filtering high-frequency waves. However, they have smaller capacity, more expensive than aluminum capacitors, and relatively weak withstand voltage and current capabilities. It is used in small-capacity low-frequency filter circuits.

Compared with ceramic capacitors, chip capacitors have capacitance and withstand voltage marks on their surface, and their surface colors are usually yellow and black.

SMD aluminum electrolytic capacitors have a larger capacity than SMD tantalum capacitors, which are more common in graphics cards.