Do you know the structural characteristics of aluminum electrolytic capacitors?

The aluminum shell and the plastic cover are closed to form an electrolytic capacitor. Compared with other types of capacitors, aluminum electrolytic capacitors have the following obvious characteristics in structure:

(1) The working medium of aluminum electrolytic capacitors is to generate a very thin layer of aluminum oxide (Al2O3) on the surface of aluminum foil by anodizing. This oxide dielectric layer and the anode of the capacitor are combined into a complete system. Interdependent and cannot be independent of each other; what we usually call a capacitor, its electrodes and dielectrics are independent of each other.

The core of the aluminum electrolytic capacitor is made of four layers of anode aluminum foil, electrolytic paper, cathode aluminum foil, and electrolytic paper.

(2) The anode of the aluminum electrolytic capacitor is an aluminum foil with an Al2O3 dielectric layer on the surface, and the cathode is not the negative foil we are used to thinking, but the electrolyte of the capacitor.

(3) The negative foil plays the role of electrical extraction in the electrolytic capacitor, because the electrolyte as the cathode of the electrolytic capacitor cannot be directly connected to the external circuit, and an electrical path must be formed through another metal electrode and other parts of the circuit.

(4) The anode aluminum foil and cathode aluminum foil of aluminum electrolytic capacitors are usually corroded aluminum foils, and the actual surface area is much larger than its apparent surface area, which is also one of the reasons why aluminum electrolytic capacitors usually have large capacitance. Due to the use of aluminum foil with numerous micro-etched holes, a liquid electrolyte is usually required to more efficiently utilize its actual electrode area.

(5) Since the dielectric oxide film of aluminum electrolytic capacitors is obtained by anodic oxidation, and its thickness is proportional to the voltage applied by anodic oxidation, in principle, the thickness of the dielectric layer of aluminum electrolytic capacitors can be artificially reduced. Precise control.