Why do electrolytic capacitor explode?

1. Electrolytic capacitor

Electrolytic capacitor are capacitor in which an oxide layer formed on an electrode by an electrolyte acts as an insulating layer, and usually has a larger capacity. Electrolyte is a liquid, jelly-like substance rich in ions. Most electrolytic capacitor are polarized, that is, when working, the voltage of the positive electrode of the capacitor must always be higher than the voltage of the negative electrode.

The high capacity of electrolytic capacitor has also been sacrificed for many other characteristics, such as large leakage current, large equivalent series inductance and resistance, large capacitance error, and short life.

In addition to polar electrolytic capacitor, there are also non-polar electrolytic capacitor.

(Non-polar and polar electrolytic capacitor)

The inside of the electrolytic capacitor may be liquid electrolyte or solid polymer, and the electrode material is usually aluminum (Aluminum) or tantalum (Tandalum).

(Internal structure of electrolytic capacitor)

Dissecting the electrolytic capacitor, you can clearly see its basic structure. In order to prevent the evaporation and leakage of the electrolyte, the capacitor pin part is fixed with sealing rubber.

Of course, the figure also shows the difference in the internal volume of electrolytic capacitor with and without polarity. Under the same capacity and withstand voltage level, non-polar electrolytic capacitor are about twice as large as those with polarity.

(Internal structure of non-polar and polar electrolytic capacitor)

This difference is mainly due to the large difference in the area of the internal electrodes of the two capacitor. The left side of the figure below is a non-polarized capacitor electrode, and the right side is a polarized electrode. In addition to the difference in area, the thickness of the two electrodes is also different, and the thickness of the polar capacitor electrode is thinner.

(Different widths of aluminum electrolytic capacitor)