Six Common Failure Modes of Aluminum Electrolytic Capacitors

 

Aluminum Electrolytic Capacitor Concept

 

Aluminum electrolytic capacitor is made of aluminum cylinder as negative pole, which is filled with liquid electrolyte and inserted into a piece of bent aluminum tape as positive pole. It also needs to be processed by DC voltage, so that a layer of oxide film is formed on the positive pole piece to make the medium. It is characterized by large capacity, but leakage, poor stability, positive and negative polarity, suitable for power supply filtering or low frequency circuit.

 

The Common Failure Mode of Aluminum Electrolytic Capacitors

 

Capacitors have a failure time, and various types of capacitors, materials, structure, manufacturing process, performance and use of different environments, the failure mechanism is also different. Today, easy capacitance network will reveal the common failure mode of aluminum electrolytic capacitors: liquid leakage, explosion, open circuit, breakdown, electrical parameters deterioration.

 

Failure Mode and Its Cause Analysis

 

1、Liquid Leakage

 

Liquid leakage, is one of the reasons for the failure of capacitors, and aluminum electrolytic capacitors are no exception. Aluminum electrolytic capacitors whose working electrolyte is acidic, if overflow, it will seriously pollute and corrode other components and printed circuit boards around the capacitor. Meanwhile, inside the electrolytic capacitor, the working electrolyte gradually dries up due to leakage, losing the ability to repair the anodic oxide film media, leading to capacitor breakdown or deterioration of electrical parameters and failure. The causes of liquid leakage are many, such as:

 

①poor sealing of aluminum electrolytic capacitors; ② the use of rubber plug sealing aluminum electrolytic capacitors, then it may be used for too long, resulting in rubber aging, cracking and leakage phenomenon; ③ mechanical sealing process there are problems; ④ installation problems, the general manufacturer will take into account the problem of liquid leakage, they will be in the enterprise standard clearly stipulates that to be installed in a vertical position, and some companies have adopted the horizontal installation and so on.

 

2、Explosion

 

Aluminum electrolytic capacitors in the working voltage AC component is too large, or oxide film media have more defects, or the presence of chlorine, sulfate and other harmful anions, so that the leakage current is larger when the electrolytic action of the gas produced by the rate of faster, the longer the working time, the larger the leakage current, the more the gas in the shell, the higher the temperature. Capacitor metal shell inside and outside the air pressure difference will increase with the increase in working voltage and working time. If the seal is good, and there is no explosion-proof measures, the air pressure increases to a certain extent will cause the capacitor explosion.

 

At present, it has been widely used in explosion-proof shell structure, in the upper part of the metal shell to increase a pleated seam, high air pressure will be pleated top open, increasing the shell volume, thereby reducing air pressure, reducing the risk of explosion. In the use of overload voltage, such as adding capacitance, rapid charging and discharging of capacitors, applying reverse voltage, etc. are likely to make the capacitor explosion.

 

3、 Breakdown

 

Aluminum electrolytic capacitor breakdown is due to anodic alumina dielectric film rupture, resulting in the electrolyte directly in contact with the anode and caused. Aluminum oxide film may be due to a variety of materials, processes or environmental conditions and local damage. Under the action of the applied electric field, the oxygen ions provided by the working electrolyte can re-form the oxide film in the damaged area, so that the anodic oxide film can be filled and repaired. However, if there are impurity ions or other defects in the damaged area, so that the filling and repairing work cannot be perfected, micro-holes will be left on the anodic oxide film, and it may even become a penetration hole, so that the aluminum electrolytic capacitor will be broken down.

 

In addition, with the growth of the use and storage time, the electrolyte solvent is gradually consumed and volatilized, so that the acid value of the solution rises, and the corrosion of the oxide film layer occurs in the storage process. At the same time, due to the electrolyte aging and drying, under the action of the electric field has not been able to provide oxygen ions to repair the oxide film, thus losing the self-healing effect, the oxide film will lead to capacitor breakdown once damaged.

 

Process defects is also a major cause of aluminum electrolytic capacitor breakdown. Such as riveting process is not good, the lead foil strips on the burr serious injury to the oxide film, puncture parts of the leakage current is very large, localized overheating of the capacitor to produce thermal breakdown. In the use of over-temperature, over ripple current or over mechanical stress may make the capacitor breakdown failure.

 

 

Basic Model of Element                        Surface Mount Type

 

           

Radial Lead Type                          Snap-in Type

 

 

4、Burning

 

Aluminum electrolytic capacitor burns, generally caused by the following reasons: ① positive and negative reverse Aluminum electrolytic capacitor is a kind of capacitor with positive and negative poles, if the installation of aluminum electrolytic capacitor positive and negative poles connected to the wrong capacitor burn phenomenon; ② voltage is not enough When the voltage exceeds the aluminum electrolytic capacitor's own withstand voltage value, the capacitor burns phenomenon will occur; ③ unqualified quality of the aluminum electrolytic capacitors produced by a number of manufacturers are not qualified, may also trigger the capacitor's burn phenomenon; ③ quality is not qualified, may also lead to the capacitor's failure. Some manufacturers of aluminum electrolytic capacitors are unqualified, may also trigger the burning of the capacitor.

 

5、 Open Circuit

 

Aluminum electrolytic capacitors in the high temperature or hot and humid environment for a long period of time may appear open-circuit failure, the reason is that the anode lead foil suffered electrochemical corrosion and fracture. For high-voltage large-capacity capacitors, this failure mode is more.

 

In addition, when the anode lead foil and the anode foil are riveted together without adequate flattening, poor contact will cause the capacitor to experience intermittent open circuits. In use, it is possible for excessive mechanical stress to open the capacitor.

 

6、Deterioration of Electric Parameters

 

①Decrease in capacitance and increase in loss The capacitance of aluminum electrolytic capacitors decreases slowly in the early stage of operation, which is due to the continuous repair and thickening of the anodic oxide film of the working electrolyte during the load process. Aluminum electrolytic capacitors in the later stages of use, due to more electrolyte depletion, solution thickening, resistivity due to viscosity increase and rise, so that the equivalent series resistance of the working electrolyte increases, resulting in a significant increase in capacitor losses.

 

At the same time, the viscosity increases the electrolyte is difficult to fully contact the oxide film layer on the surface of the uneven aluminum foil by corrosion treatment, which makes the effective area of the pole plate of the aluminum electrolytic capacitor decreases, resulting in a sharp decline in capacitance. This is also the performance of capacitors near the end of their service life.

 

In addition, if the working electrolyte viscosity increases too much at low temperatures, it will also result in increased losses and a sharp drop in capacitance. In the use of over-temperature, too ripple current may make the capacity drop and loss increase.

 

②Leakage current increases Leakage current increases often lead to failure of aluminum electrolytic capacitors. Low level of technology, oxide film damage and contamination is serious, the work of the electrolyte formula is not good, the purity of raw materials is not high, the chemical and electrochemical properties of the electrolyte is difficult to long-term stability, aluminum foil purity is not high, impurity content and so on these factors may cause leakage current over the poor failure.

 

Aluminum electrolytic capacitors in the chloride ion staining serious, leakage current leads to stained parts of the oxide film decomposition, resulting in perforation, prompting further increase in current. In short, the presence of metal impurities in the aluminum foil will increase the leakage current of aluminum electrolytic capacitors, thereby shortening the life of the capacitor. In the use of overvoltage, etc. may increase the leakage current of the capacitor.

 

UF Capacitors History and Advantages

 

UF Capacitors is established since 1995, as one of the professional China Capacitor manufacturer in China,

we are strong in complete management, strict quality control system, and excellent sales service.UF Capacitors

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Our marketing position is to provide a superior alternative to first-tier brands such as TDK, Murata, AVX, EPCOS,Vishay, and Panasonic. We offer similar quality but at better prices, with faster lead times and excellent service. With extensive experience working with renowned international companies like GE, Philips, Jabil, and Flex, we have built a strong reputation.

 

UF Capacitors serves the consumer electronics, computing, communications, and industrial markets. As a professional Chinese electronic components manufacturer, we are dedicated to delivering high-quality electronic components,exceptional management, strict quality control systems, and excellent sales service. We strive to foster mutually beneficial partnerships and drive business growth.

 

 

SMD Electrolytic Capacitor Cross Reference
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