
Failing aluminum electrolytic capacitors can have significantly adverse effects on electronic circuits. Most technicians have seen the tale-tell signs – bulging, chemical leaks, and even tops that have blown off. When they fail, the circuits. . For the sake of this article, the part that causes an electrolytic capacitor to fail most often will be highlighted. Essentially, the capacitor consists of. . This blog is intended for experienced or supervised technicians. Always take appropriate safety precautions when dealing with live circuits. For informational purposes only. Utilize the concepts in this blog at your own risk. The. [pdf]
The vast majority of electrolytic capacitor failures are caused by one or more of the following mechanisms: dry-out of the electrolyte, loss of adhesion between the electrode and electrolyte, corrosion of the electrode, or breakdown of the dielectric.
It is important that designers understand what causes electrolytic capacitor degradation. When an electrolytic capacitor fails, it can be because of a short circuit, circuit damage, or even an explosion. Most electrolytic capacitor degradation results from a common failure mode: the vaporization or leakage of electrolyte.
Mica and tantalum capacitors are more likely to fail in the early period of use (early failure), while aluminum electrolytic capacitors are more likely to experience wear-out failure due to aging use. In the case of film capacitors, when a local short circuit failure occurs, the shorted area may temporarily self-heal.
The failure of the electrolytic capacitor in a circuit can cause a short circuit (due to mechanical failure), open circuit (manufacturing defect, mechanical failure), loss in capacitance, and high ESR. Short Circuit: Short circuits between the electrodes can occur due to vibration, shock, or stress on leads.
Failing aluminum electrolytic capacitors can have significantly adverse effects on electronic circuits. Most technicians have seen the tale-tell signs – bulging, chemical leaks, and even tops that have blown off. When they fail, the circuits that contain them no longer perform as designed – most often affecting power supplies.
The datasheet mentions the importance of careful handling, but doesn't seem to specify the failure modes in the case of mechanical abuse. In my experience, in general, reverse-installed electrolytic capacitors readily explode, as will capacitors which exceed their maximum (forward or reverse) voltage.

Power capacitors are electrical energy storage devices, thus you must always handle them with caution. Even if they are turned off for a long period of time, capacitors might still be charged with high voltage, and this may be lethal. For this reason, please be extremely careful when handling capacitors and electrically. . The most frequent risk factors which cause capacitor damage and possible failure of the internal protective devices are: 1. Exceeding the. . Never use capacitors that have dents of more than 1 mm depth or any other mechanical damage. This applies also in cases of leakage. To ensure the functionality of the overpressure disconnector, do not. . The capacitor manufacturer cannot predict every possible stress which a power capacitor may be subjected to, and which has to be taken into account in a proper design. This means that the user bears crucial co-responsibility.. [pdf]
The shelf life of most capacitors depends on environment factors such as humidity, temperature, and atmospheric pressure. Subjecting capacitors to harsh conditions can significantly affect their electrical properties, or even damage them completely.
Ceramic capacitors should be stored at temperature and humidity conditions specified by the manufacturer. Before using a capacitor, you should check the recommended shelf life, date of receipt, and inspect terminations. For most capacitors, the shelf life is significantly determined by storage conditions.
( 2 ) Operating temperature and applied ripple current shall be within the specification. qThe capacitor shall not be used in an ambient temperature which exceeds the operating temperature specified in the specification. wDo not apply excessive current which exceeds the allowable ripple current.
The electrical characteristics that are affected when these capacitors are stored for a long time without charge are equivalent series resistance (ESR), leakage current, and capacitance. ESR and leakage current increase while capacitance decreases. Nevertheless, the changes are small if these capacitors are stored at room temperature.
Before using a capacitor, it is important to check its receipt time. Some capacitors require reforming after they have been stored for an extended period of time without recharge. To maximize the life of capacitors, they should be stored under conditions specified by the manufacturer.
Subjecting capacitors to harsh conditions can significantly affect their electrical properties, or even damage them completely. The effect of environmental factors on the shelf life of capacitors varies depending on the chemical composition and construction of a capacitor.

Class-X and Class-Y capacitors are safety-certified and generally designed and used in AC line filtering in many electronic device applications. These safety capacitors are also known by other names, including EMI/RFI suppression capacitors and AC line filter safety capacitors. (EMI stands for electromagnetic interference. . Class-X and Class-Y capacitors are classified according to: 1. their peak voltage/rated voltage and 2. the peak impulse voltage that they can safely withstand. Tables 1 and 2. . Subclass X2 and Y2 are the most commonly used safety-certified capacitors. Depending upon your own application and requirements, they are. . Because Class-X and Class-Y capacitors must be connected directly to AC lines (line-to-neutral or line-to-ground) in order for them to perform their EMI and RFI filtering functions, they must be rated and certified as "safety. . All safety-certified capacitors should have the proper logo markings/symbols on their casing. See Figure 4 below for an example and see Figure 5 for a definition/description of these logos: [pdf]
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