The possible forms of failure are:
1. The water film is condensed on the surface of the capacitor shell. It should be because the humidity in the air is too high, which will cause the insulation resistance of the capacitor surface to decrease. Compared with the semi-hermetic structure capacitor, moisture will also penetrate into the capacitor dielectric, resulting in a decrease in the insulation resistance of the capacitor dielectric.
2. When the inorganic dielectric capacitor is working under the high temperature condition of the semi-hermetic capacitor, the water molecules infiltrating into the capacitor will produce electrolysis. Silver ions will migrate on the surface and inside of the inorganic medium, which will cause the leakage current to increase. In severe cases, it will be completely short-circuited and the capacitor will break down.
Ion migration will seriously damage the silver layer on the surface of the positive electrode, and make the capacitor without dielectric (the loss of the metal part increases, the equivalent series resistance increases, and the loss tangent value of the capacitor increases)
Key point: The phenomenon of failure caused by the migration of silver ions, silver electrode low-frequency ceramic monolithic capacitor is much more serious than other types, because of the manufacturing process and structure of this type of capacitor.
3. When working under high humidity conditions, semi-hermetic ceramic capacitor have a common serious problem that breakdown failure occurs.
The migration of silver ions causes serious distortion of the fringe electric field between the capacitor, and also due to the condensation of water film on the surface of the ceramic medium in a high-humidity environment, the surface arc flashover phenomenon occurs under the working conditions of the capacitor.
4. When wave soldering laminated ceramic capacitor, the electrode ends may be melted by the solder. The main reason is that the wave-soldering laminated ceramic capacitor has been in contact with high-temperature solder for too long.
5. The first cause of failure of ceramic capacitor is the migration of silver ions in ceramic capacitor and the resulting accelerated aging of titanium-containing ceramic dielectrics.
In order to improve the stability of monolithic capacitor, silver-palladium electrodes were used instead and 1% of 5# glass powder was added to the material formula. The energy dissipation promotes the sintering and densification of the porcelain, which improves the performance of the product by level 1 to 2.
6. After the laminated ceramic capacitor is mechanically broken, the electrode insulation distance of the fracture will be less than the breakdown voltage, which will cause arc discharge between more than one electrode and completely damage the laminated ceramic capacitor.
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