Reasons affecting the life of metallized film capacitors

Many customers will respond, how to purchase the same metallized film capacitors, some are very durable, and have a long life, but some have a short life. This is because the life of the film capacitor is affected by many aspects. Knowing the factors that influence the influence and taking measures can improve the life of the capacitor.

The size of the metallized film capacitor is determined by the size of the thin film metal layer. Therefore, the main reason for the decrease in capacity is that the metal plating is affected by various external factors and the area is reduced. Under normal circumstances, there are three main reasons that affect the service life of metallized film capacitors:

1. The voltage is too high.

2. For high frequency. (high frequency, large dielectric loss, thermal breakdown)

3. The ambient temperature is high.

The metallized film capacitor is directly coated with a metal film on the medium as an electrode, that is, a metalized dielectric capacitor. Since the electrode is a metal film plated in the form of steam, it is much thinner than the mechanically produced aluminum foil. This type of capacitor is characterized by self-healing. If the voltage is too high, causing a certain point in the internal dielectric of the capacitor to be broken, the short-circuit current will cause the metal film at the damage of the medium to evaporate. Even if the metal film capacitor is self-healing, if the breakdown range is too large, it will affect the capacitance of the capacitor, which will also affect the life of the capacitor.

During the capacitor manufacturing process, a small amount of air exists between the layers, which is difficult to completely eliminate. Therefore, when the capacitor is in operation, the air may be ionized by the electric field. Ozone is produced after air ionization. Ozone is an unstable gas. It is self-divided into oxygen at room temperature and is a strong oxidant. Oxidation can be completed instantaneously at low concentrations. The metal plating of the metallized film capacitor is oxidized immediately after encountering the oxygen of the ozone to form a transparent non-conductive metal oxide, resulting in a decrease in the capacity of the capacitor. Therefore, reducing the air between the layers can reduce the capacitance decay. When the air between the membrane layers is invaded by the external water, the breakdown potential of the air is lowered, the air ionization is increased upward, a large amount of ozone is generated, and the metal plating layer of the metallized film capacitor is oxidized, and the capacity of the capacitor is rapidly decreased.