WEE Technology Company Limited - WEE are Capacitors Specialist

5. Open circuit

The open circuit failure of aluminum electrolytic capacitor may occur when it works in high temperature or hot humid environment for a long time. The reason is that the anode lead-out foil is broken due to electrochemical corrosion. For high voltage and large capacity capacitors, there are many such failure modes. In addition, if the anode lead-out foil and anode foil are riveted, the capacitor will open intermittently due to poor contact. In use, over mechanical stress may cuase the open circuit of the capacitor.

6. Deterioration of electrical parameters

① Decrease of capacitance and increase of loss

The capacitance of aluminum electrolytic capacitor decreases slowly in the early stage of operation, which is due to the continuous repair of working electrolyte and thickening of anodic oxide film during the loading process. In the later stage of use of aluminum electrolytic capacitor, due to the loss of electrolyte and the thickening of solution, the resistivity increases due to the increase of viscosity, resulting in the increase of equivalent series resistance of working electrolyte, resulting in the obvious increase of capacitor loss. At the same time, the electrolyte with increased viscosity is difficult to fully contact the oxide film on the surface of the corroded uneven aluminum foil, which makes the effective area of the electrode plate of the aluminum electrolytic capacitor decrease and the capacitance drops sharply. This is also the performance of the capacitor near the end of its service life.

In addition, if the viscosity of working electrolyte increases too much at low temperature, the loss will increase and the capacitance will drop sharply. In use, over temperature and ripple current may make the capacitance decrease and loss increase.

② Leakage current increases

The increase of leakage current often leads to the failure of aluminum electrolytic capacitor. Low process level, serious damage and contamination of oxide film, poor formulation of working electrolyte, low purity of raw materials, difficulty in long-term stability of chemical and electrochemical properties of electrolyte, low purity of aluminum foil and high content of impurities, etc., all of these factors may cause leakage current out of tolerance. The chloride ion contamination in aluminum electrolytic capacitor is serious. The leakage current leads to the decomposition of oxide film at the contaminated part, resulting in perforation, which further increases the current. In a word, the existence of metal impurities in aluminum foil will increase the leakage current of aluminum electrolytic capacitor, thus shortening the life of capacitor.