What are the selection skills of chip capacitors?

SMD capacitors have a larger volume, larger series resistance, larger inductive reactance, and are sensitive to temperature. It is suitable for occasions where the temperature changes little and the working frequency is not high (not higher than 25kHz), and it can be used for low-frequency filtering (the parallel filtering effect of the chip capacitor is low at high frequency). Chip capacitors have polarity, and the correct polarity must be ensured during installation, otherwise there is a danger of explosion.

Compared with chip capacitors, tantalum chip capacitors have obvious advantages in series resistance, inductance, and temperature stability. However, it operates at a lower voltage. 1.3 times the rated voltage of the chip capacitor is used as the surge voltage of the capacitor. When the working voltage is higher than 160V, it is the rated working voltage +50V as the surge voltage. Voltage. When the capacitor is in the surge voltage, the current will be very large, usually 10~15 times of the normal situation, if the time is too long, it will burst open. Therefore, in general, the voltage of aluminum capacitors should be selected slightly higher, and the actual working voltage should be 70~80% of the nominal voltage.

The applicable guidelines for chip capacitors are as follows:

1. The voltage value of the chip capacitor in the filter circuit is 1.2--1.5 times the noise peak value according to the specific situation, not according to the rated value of the filter circuit;

2. There shall be no pads and vias directly below the chip capacitor.

3. SMD capacitors must not be in direct contact with surrounding heating elements.

4. SMD capacitors are divided into positive and negative poles. Reverse voltage and AC voltage should not be applied. Non-polar capacitors should be used where reverse voltage may occur.

5. Chip capacitors should not be used where fast charge and discharge are required, and specially designed capacitors with longer life should be selected.

6. Overvoltage should not be used.

(1). The sewing voltage after the superimposed DC voltage Yuwenbo voltage is lower than the rated value.

(2). When two or more chip capacitors are connected in series, a balanced resistor should be considered, so that the voltage on each capacitor is within its rated range.