What are the reasons for the capacity degradation of aluminum electrolytic capacitors?

Summary: What are the reasons for the capacity degradation of aluminum electrolytic capa...
What are the reasons for the capacity degradation of aluminum electrolytic capacitors? Aluminum electrolytic capacitors are widely used in consumer electronics, industrial control, communication products, computers and peripheral products, instrumentation, automotive industry and other products. They are one of the main irreplaceable members of the capacitor family. The basic structure of an aluminum electrolytic capacitor is that there is an aluminum shell on the outside, and the sealed aluminum shell contains electronic aluminum foil, electrolytic paper, electrolyte, etc., and leads out two positive and negative electrodes.


Due to the complexity of the structure and manufacturing process of aluminum electrolytic capacitors, some problems will inevitably occur during production, storage, and use, such as capacity attenuation and increased loss. It is generally believed that there are three main reasons for the capacity attenuation of aluminum electrolytic capacitors:


1. Poor contact between the guide pin and the aluminum foil leads to an increase in contact resistance and a decrease in capacity, such as excessive riveting thickness, too much powder in the anode aluminum foil, and lubrication at the rivet needle and rivet hole;


2. Insufficient electrolyte impregnated in the anode foil or cathode foil leads to the incomplete extraction of the capacity and the capacity attenuation, such as high electrolyte viscosity, poor permeability, incomplete impregnation or too long drying time, poor sealing performance, electrolyte volatilization or loss And other reasons;


3. Poor control of product aging process parameters leads to thickening of the anode or cathode foil oxide film, resulting in capacity degradation, such as the aging voltage or temperature is too high, the aging process is subject to reverse voltage due to operating errors.


The capacity of aluminum electrolytic capacitors decreased significantly in the later period of use, mainly due to the loss of electrolyte, the increase in viscosity of the electrolyte, and the increase in resistivity due to the increase in viscosity, which increased the equivalent series resistance of the working electrolyte and also caused The capacitor loss has increased significantly.


The increased viscosity of the electrolyte reduces the ability to repair the oxide film surface, so that the effective area of ​​the capacitor plate is reduced, causing the capacity of the aluminum electrolytic capacitor to drop sharply, which is also the performance of the capacitor's service life near the end. In addition, the low temperature performance of the working electrolyte of some systems is not good, and the viscosity is too large, which will cause the equivalent series resistance to increase sharply, which will increase the loss and reduce the capacitance, which is easy to cause early failure under severe cold work.


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