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Structurally, capacitors consist of electrodes separated by a dielectric, connecting leads, and housing; deterioration of any of these may cause parameter shifts or failure. Shorted failures and leakage due to increase of parallel parasitic resistance are the most common failure modes of capacitors, followed by open failures.
Failed aluminium electrolytic capacitors with open vents in the top of the can, and visible dried electrolyte residue (reddish-brown color) The capacitor plague was a problem related to a higher-than-expected failure rate of non-solid aluminium electrolytic capacitors between 1999 and 2007, especially those from some Taiwanese manufacturers, [1] [2] due to faulty electrolyte composition that ...
Leakage increases power consumption and if sufficiently large can cause complete circuit failure. Leakage is currently one of the main factors limiting increased computer processor performance. Efforts to minimize leakage include the use of strained silicon , high-κ dielectrics , and/or stronger dopant levels in the semiconductor.
If the failure is a short circuit (the most common occurrence), and current is not limited to a safe value, catastrophic thermal runaway may occur. This failure can even result in the capacitor forcefully ejecting its burning core. Tantalum electrolytic capacitors with solid electrolyte are marked at their positive terminal with a bar or a "+".
When subjected to reversed polarity (even briefly), the capacitor depolarizes and the dielectric oxide layer breaks down, which can cause it to fail even when later operated with correct polarity. If the failure is a short circuit (the most common occurrence), and current is not limited to a safe value, catastrophic thermal runaway may occur.
A discharged or partially charged capacitor appears as a short circuit to the source when the source voltage is higher than the potential of the capacitor. A fully discharged capacitor will take approximately 5 RC time periods to fully charge; during the charging period, instantaneous current can exceed steady-state current by a substantial ...
Some capacitors have a "pressure-sensitive interrupter" design that causes them to fail before internal pressures can cause serious injury. One such design causes the top of the capacitor to expand and break internal wiring. [7] Over many years of use the capacitance of the capacitor drops; this is known as a "weak capacitor".
Corona can progressively damage the insulation inside these devices, leading to equipment failure. Elastomer items such as O-rings can suffer ozone cracking. Plastic film capacitors operating at mains voltage can suffer progressive loss of capacitance as corona discharges cause local vaporization of the metallization. [8]