WEE Technology Company Limited - WEE are Capacitors Specialist

Metal film capacitor, structure and characteristics of several common capacitors

Capacitors are commonly used electronic components in electronic equipment. In the previous article, we understand why capacitors can be connected with alternating current and blocking direct current and many kinds of capacitors are also mentioned, but there is no detailed description of various capacitors. Next, we briefly introduce the structure and characteristics of several common capacitors for your reference.

1. Aluminum electrolytic capacitor:

It is made of aluminum cylinder as negative electrode, which is filled with liquid electrolyte and inserted with a bent aluminum strip as cathode. It also needs to be treated by DC voltage to form a layer of oxide film on the positive plate as the medium. It is characterized by large capacity, but large leakage, poor stability and positive and negative polarity. It is suitable for power filter or low frequency circuit. When using, the positive and negative pole should not be reversed.

2. Tantalum niobium electrolytic capacitor:

The anode is made of tantalum or tantalum oxide. Its characteristics are: small volume, large capacity, stable performance, long life, high insulation resistance. Good temperature performance, used in higher requirements of equipment.

3. Ceramic capacitor:

Use ceramics as the medium. Silver coating was sprayed on both sides of the ceramic substrate, and then the silver film was fired as the electrode plate. Its characteristics are: small size, good heat resistance, small loss, high insulation resistance, but small capacity, suitable for high frequency circuit. Ferroelectric ceramics are suitable for low frequency circuits because of their large capacitance, high loss and high temperature coefficient.

4. Mica capacitor:

The electrode plate is made by metal foil or spraying silver layer on mica sheet. The electrode plate is laminated with mica layer by layer, and then it is made by die casting in Bakelite powder or sealing in epoxy resin. It is characterized by small dielectric loss and large insulation resistance. Low temperature coefficient, suitable for high frequency circuit.

5. Film capacitor:

The structure is the same as that of paper capacitor, and the medium is polyester or polystyrene. Polyester film capacitor, with high dielectric constant, small volume, large capacity and good stability, is suitable for bypass capacitor. Polystyrene film capacitor, with low dielectric loss, high insulation resistance and high temperature coefficient, can be used in high frequency circuit.

6. Paper capacitor:

The electrode is made of two pieces of metal foil, sandwiched in a very thin capacitor paper, rolled into a cylindrical or flat cylindrical core, and then sealed in a metal shell or insulating material shell. It is characterized by small volume and large capacity. But the inherent inductance and loss are relatively large, suitable for low-frequency circuit.

7. Metallized paper capacitor:

The structure is basically the same as the paper capacitor. It is covered with a layer of metal film on the capacitor paper to replace the metal foil. It is small in size and large in capacitance. It is generally used in low-frequency circuits.

8. Oil impregnated paper capacitor:
it is to immerse paper capacitor in specially treated oil to enhance its withstand voltage. It is characterized by large capacitance, high voltage withstand, but large volume. In addition, in practical application, firstly, different types of capacitors should be selected according to different uses; secondly, the nominal capacity of capacitors, allowable error, withstand voltage value, leakage resistance and other technical parameters should be considered; thirdly, for electrolytic capacitors with positive and negative polarity, the positive and negative electrodes should not be connected in reverse when welding.