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{{Short description|Ways electronic components fail and prevention measures}}
{{Use
{{Use dmy dates|date=March 2020}}
[[File:Failed SMPS controller IC ISL6251.jpg|thumb|Failed [[integrated circuit|IC]] in a laptop. Wrong input voltage has caused massive overheating of the chip and melted the plastic casing.]]▼
▲[[File:Failed SMPS controller IC ISL6251.jpg|thumb|Failed [[integrated circuit|IC]] in a laptop. Wrong input
'''Electronic components''' have a wide range of '''[[failure mode]]s'''. These can be classified in various ways, such as by time or cause. Failures can be caused by excess temperature, excess current or voltage, [[ionizing radiation]], mechanical shock, stress or impact, and many other causes. In semiconductor devices, problems in the device package may cause failures due to contamination, mechanical stress of the device, or open or short circuits. ▼
▲
Failures most commonly occur at near the beginning and near the ending of the lifetime of the parts, resulting in the [[bathtub curve]] graph of [[failure rate]]s. [[Burn-in]] procedures are used to detect early failures. In semiconductor devices, [[parasitic structure]]s, irrelevant for normal operation, become important in the context of failures; they can be both a source and protection against failure.▼
▲Failures most commonly occur
Applications such as aerospace systems, life support systems, telecommunications, railway signals, and computers use great numbers of individual electronic components. Analysis of the statistical properties of failures can give guidance in designs to establish a given level of reliability. For example, power-handling ability of a resistor may be greatly derated when applied in high-altitude aircraft to obtain adequate service life; a part intended for a telephone switch that must run for decades has different reliability requirements than a part for a [[proximity fuze]] that must only operate for a few seconds. ▼
▲Applications such as aerospace systems, life support systems, telecommunications, railway signals, and computers use great numbers of individual electronic components. Analysis of the statistical properties of failures can give guidance in designs to establish a given level of reliability. For example, the power-handling ability of a resistor may be greatly derated when applied in high-altitude aircraft to obtain adequate service life
A sudden fail-open fault can cause multiple secondary failures if it is fast and the circuit contains an [[inductance]]; this causes large voltage spikes, which may exceed 500 volts. A broken metallisation on a chip may thus cause secondary overvoltage damage.<ref name="istfa2001">[http://books.google.com/books?id=-jlSjurXBc0C&pg=PA267&dq=resistor+failure&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&num=50&as_brr=3&cd=16#v=onepage&q=resistor%20failure&f=false STFA 2001: proceedings of the 27th International Symposium for Testing and Failure Analysis]: 11–15 November 2001, Santa Clara Convention Center, Santa Clara, California, p. 267 ISBN 0-87170-746-2</ref> [[Thermal runaway]] can cause sudden failures including melting, fire or explosions.▼
▲A sudden fail-open fault can cause multiple secondary failures if it is fast and the circuit contains an [[inductance]]; this causes large [[voltage
==Packaging failures==
<!-- This section seems to be written primarily about failure modes of military hermetic components but doesn't really apply to most modern electronics which are plastic, ie glass metal interfaces and atmosphere within cavities are not found in most modern electronics -->
The majority of electronic parts failures are [[electronic packaging|packaging]]-related.{{Citation needed|date=April 2011}} Packaging, as the barrier between electronic parts and the environment, is very susceptible to environmental factors. [[Thermal expansion]] produces mechanical stresses that may cause [[material fatigue]], especially when the thermal expansion coefficients of the materials are different. Humidity and aggressive chemicals can cause corrosion of the packaging materials and leads, potentially breaking them and damaging the inside parts, leading to electrical failure. Exceeding the allowed environmental temperature range can cause overstressing of wire bonds, thus tearing the connections loose, cracking the semiconductor dies, or causing packaging cracks. Humidity
During encapsulation, bonding wires can be severed, shorted, or touch the chip die, usually at the edge. Dies can crack due to mechanical overstress or thermal shock; defects introduced during processing, like scribing, can develop into fractures. Lead frames may contain excessive material or burrs, causing shorts. Ionic contaminants like [[alkali metal]]s and [[halogen]]s can migrate from the packaging materials to the semiconductor dies, causing corrosion or parameter deterioration. Glass-metal seals commonly fail by forming radial cracks that originate at the pin-glass interface and permeate outwards; other causes include a weak oxide layer on the interface and poor formation of a glass meniscus around the pin.<ref name="elecmatpack"/>
Various gases may be present in the package cavity, either as impurities trapped during manufacturing, due to [[outgassing]] of the materials used, or chemical reactions, as is when the packaging material gets overheated (the products are often ionic and facilitate corrosion with delayed failure). To detect this, [[helium]] is often in the inert atmosphere inside the packaging as a [[tracer gas]] to detect leaks during testing. Carbon dioxide and hydrogen may form from organic materials, moisture is outgassed by polymers and amine-cured epoxies outgas [[ammonia]]. Formation of cracks and intermetallic growth in die attachments may lead to the formation of voids and delamination, impairing heat transfer from the chip die to the substrate and heatsink and causing a thermal failure. As some semiconductors like silicon and [[gallium arsenide]] are infrared-transparent, infrared microscopy can check the integrity of die bonding and under-die structures.<ref name="elecmatpack"/>
[[Red phosphorus]], used as a
==Contact failures==
Electrical contacts exhibit [[contact resistance]], the magnitude of which is governed by surface structure and the composition of surface layers.<ref>{{cite journal| last1=Zhai| first1=C. |display-authors=etal|title= Stress-Dependent Electrical Contact Resistance at Fractal Rough Surfaces| journal= Journal of Engineering Mechanics| year=2015| volume=143 |issue=3 | pages=B4015001 | doi= 10.1061/(ASCE)EM.1943-7889.0000967}}</ref> Ideally contact resistance should be low and stable, however weak contact pressure, [[mechanical vibration]], and corrosion can alter contact resistance significantly, leading to [[resistive heating]] and circuit failure.
Soldered joints can fail in many ways like [[electromigration]] and formation of brittle [[intermetallic]] layers. Some failures show only at extreme joint temperatures, hindering troubleshooting. Thermal expansion mismatch between the printed circuit board material and its packaging strains the part-to-board bonds; while leaded parts can absorb the strain by bending, leadless parts rely on the solder to absorb stresses. Thermal cycling may lead to fatigue cracking of the solder joints, especially with [[elasticity (physics)|elastic]] solders; various approaches are used to mitigate such incidents. Loose particles, like bonding wire and weld flash, can form in the device cavity and migrate inside the packaging, causing often intermittent and shock-sensitive shorts. Corrosion may cause buildup of oxides and other nonconductive products on the contact surfaces. When closed, these then show unacceptably high resistance; they may also migrate and cause shorts.<ref name="elecmatpack"/> [[Tin whisker]]s can form on tin-coated metals like the internal side of the packagings; loose whiskers then can cause intermittent short circuits inside the packaging. [[Cable]]s, in addition to the methods described above, may fail by fraying and fire damage.▼
▲Soldered joints can fail in many ways
==Printed circuit board failures==
[[File:PCB corrosion.jpg|thumb|right|Severe PCB corrosion from a [[Battery leakage|leaky]] PCB mounted Ni-Cd battery]]
[[Printed circuit board]]s (PCBs) are vulnerable to environmental influences; for example, the traces are corrosion-prone and may be improperly etched leaving partial shorts or may crack under mechanical loads, while the [[via (electronics)|vias]] may be insufficiently plated through
Above the [[glass transition temperature]] of PCBs, the resin matrix softens and becomes susceptible to contaminant diffusion. For example, polyglycols from the [[
[[Conductive anodic
==Relay and switch failures==
Every time the contacts of
| author-first=Ragnar
▲Every time the contacts of an electromechanical [[relay]] or [[contactor]] are opened or closed, there is a certain amount of wear. An [[electric arc]] occurs between the contact points (electrodes) both during the transition from closed to open (break) or from open to closed (make). The arc caused during the contact break (break arc) is akin to [[arc welding]], as the break arc is typically more energetic and more destructive.<ref>{{cite book
| author-last
| author-link=Ragnar Holm
| title = Electric Contacts Handbook
| pages =
| publisher = Springer-Verlag, Berlin / Göttingen / Heidelberg
| year = 1958
| doi =
| isbn =
}}</ref> The heat and current of the electrical arc across the contacts creates specific cone & crater formations from metal migration. In addition to the physical contact damage, there appears also a coating of carbon and other matter. This degradation
}}</ref>▼
▲The heat and current of the electrical arc across the contacts creates specific cone & crater formations from metal migration. In addition to the physical contact damage, there appears also a coating of carbon and other matter. This degradation drastically limits the overall operating life of a relay or contactor to a range of perhaps 100,000 operations, a level representing 1% or less than the mechanical life expectancy of the same device.<ref>{{cite web | title = Lab Note #105 ''Contact Life - Unsuppressed vs. Suppressed Arcing'' | author= | publisher = Arc Suppression Technologies | date = August 2011 | url = http://arcsuppressiontechnologies.com/Documents/Lab%20Note%20107%20-%20AUG2011%20-%20Relay%20Life%201M.pdf | accessdate = March 10, 2012}}</ref>
==Semiconductor failures==
{{See also|Reliability (semiconductor)}}
Many failures
Examples of semiconductor failures relating to semiconductor crystals include:
* [[Nucleation]] and growth of [[dislocation]]s. This requires an existing defect in the crystal, as is done by radiation, and is accelerated by heat, high current density and emitted light. With LEDs, [[gallium arsenide]] and [[aluminium gallium arsenide]] are more susceptible to this than [[gallium arsenide phosphide]] and [[indium phosphide]]; [[gallium nitride]] and [[indium gallium nitride]] are insensitive to this defect.▼
* Accumulation of [[charge carrier]]s trapped in the [[gate oxide]] of [[MOSFET]]s. This introduces permanent gate [[biasing]], influencing the transistor's threshold voltage; it may be caused by [[hot carrier injection]], [[ionizing radiation]] or
▲*[[Nucleation]] and growth of [[dislocation]]s. This requires an existing defect in the crystal, as is done by radiation, and is accelerated by heat, high current density and emitted light. With LEDs, [[gallium arsenide]] and [[aluminium gallium arsenide]] are more susceptible to this than [[gallium arsenide phosphide]] and [[indium phosphide]]; [[gallium nitride]] and [[indium gallium nitride]] are insensitive to this defect.
* Migration of charge carriers from [[floating gate]]s. This limits the lifetime of stored data in [[EEPROM]] and [[flash
▲*Accumulation of [[charge carrier]]s trapped in the [[gate oxide]] of [[MOSFET]]s. This introduces permanent gate [[biasing]], influencing the transistor's threshold voltage; it may be caused by [[hot carrier injection]], [[ionizing radiation]] or nominal use. With [[EEPROM]] cells, this is the major factor limiting the number of erase-write cycles.
* Improper [[Passivation (chemistry)|passivation]]. [[Corrosion]] is a significant source of delayed failures; semiconductors, metallic interconnects, and passivation glasses are all susceptible. The surface of semiconductors subjected to moisture has an oxide layer; the liberated hydrogen reacts with deeper layers of the material, yielding volatile [[hydride]]s.<ref>{{cite book|url=
▲*Migration of charge carriers from [[floating gate]]s. This limits the lifetime of stored data in [[EEPROM]] and flash EPROM structures.
* Laser marking of plastic-encapsulated packages may damage the chip if glass spheres in the packaging line up and direct the laser to the chip.<ref name="istfa2008"/><!--[[User:Kvng/RTH]]-->
▲*Improper passivation. [[Corrosion]] is a significant source of delayed failures; semiconductors, metallic interconnects, and passivation glasses are all susceptible. The surface of semiconductors subjected to moisture has an oxide layer; the liberated hydrogen reacts with deeper layers of the material, yielding volatile [[hydride]]s.<ref>{{cite book|url=http://books.google.com/?id=lg8ZuZPYG5oC&pg=PA251&dq=semiconductor+failure+microphotograph&cd=41#v=onepage&q=|page=251 |title=Corrosion and reliability of electronic materials and devices: proceedings of the Fourth International Symposium|publisher=The Electrochemical Society|year=1999|isbn=1-56677-252-4}}</ref>
===Parameter failures===
[[Via (electronics)|Vias]] are a common source of unwanted serial resistance on chips; defective vias show unacceptably high resistance and therefore increase propagation delays. As their resistivity drops with increasing temperature, degradation of the maximum operating frequency of the chip the other way is an indicator of such a fault. ''Mousebites'' are regions where metallization has a decreased width; such defects usually do not show during electrical testing but present a major reliability risk. Increased current density in the mousebite can aggravate electromigration problems; a large degree of voiding is needed to create a temperature-sensitive propagation delay.<ref name="micfailanal">[
Sometimes, circuit tolerances can make erratic behaviour difficult to trace; for example, a weak driver transistor, a higher series resistance and the capacitance of the gate of the subsequent transistor may be within tolerance but can significantly increase signal [[propagation delay]]. These can manifest only at specific environmental conditions, high clock speeds, low power supply voltages, and sometimes specific circuit signal states; significant variations can occur on a single die.<ref name="micfailanal"/> Overstress-induced damage like ohmic shunts or a reduced transistor output current can increase such delays, leading to erratic behavior. As propagation delays depend heavily on supply voltage, tolerance-bound fluctuations of the latter can trigger such behavior.
[[Gallium arsenide]] [[monolithic microwave integrated circuit]]s can have these failures:<ref name="nasammic4">[http://parts.jpl.nasa.gov/mmic/4.PDF Chapter 4. Basic Failure Modes and Mechanisms], S. Kayali</ref>
* Degradation of I<sub>DSS</sub>
* Degradation in gate [[leakage current]]. This occurs at accelerated life tests or high temperatures and is suspected to be caused by surface-state effects.
* Degradation in [[Threshold voltage|pinch-off voltage]]. This is a common failure mode for gallium arsenide devices operating at high temperature, and primarily stems from semiconductor-metal interactions and degradation of gate metal structures, with hydrogen being another reason. It can be hindered by a suitable [[barrier metal]] between the contacts and gallium arsenide.
* Increase in drain-to-source resistance. It is observed in high-temperature devices, and is caused by metal-semiconductor interactions, gate sinking and ohmic contact degradation.
===Metallisation failures===
[[File:Failed transistor.jpg|thumb|right|Micro-photograph of a failed TO3 power transistor due to short circuit]]
Metallisation failures are more common and serious causes of FET transistor degradation than material processes; [[amorphous]] materials have no grain boundaries, hindering interdiffusion and corrosion.<ref name="semidevrel">{{cite book|url=
* [[Electromigration]] moving atoms out of active regions, causing dislocations and point defects acting as nonradiative recombination centers producing heat. This may occur with aluminium gates in [[MESFET]]s with [[
* Mechanical stresses, high currents, and corrosive environments forming of [[whisker (metallurgy)|whiskers]] and short circuits. These effects can occur both within packaging and on [[circuit board]]s.
* Formation of silicon nodules. [[Aluminium interconnects]] may be silicon-doped to saturation during deposition to prevent alloy spikes. During thermal cycling, the silicon atoms may migrate and clump together forming nodules that act as voids, increasing local resistance and lowering device lifetime.<ref name="elecmatpack"/>
* [[Ohmic contact]] degradation between metallisation and semiconductor layers. With gallium arsenide, a layer of gold-germanium alloy (sometimes with nickel) is used to achieve low contact resistance; an ohmic contact is formed by diffusion of germanium, forming a thin, highly n-doped region under the metal facilitating the connection, leaving gold deposited over it. Gallium atoms may migrate through this layer and get scavenged by the gold above, creating a defect-rich gallium-depleted zone under the contact; gold and oxygen then migrate oppositely, resulting in increased resistance of the ohmic contact and depletion of effective doping level.<ref name="semidevrel"/> Formation of [[intermetallic]] compounds also plays a role in this failure mode.
===Electrical overstress===
Most stress-related semiconductor failures are electrothermal in nature microscopically; locally increased temperatures can lead to immediate failure by melting or vaporising metallisation layers, melting the semiconductor or by changing structures. Diffusion and electromigration tend to be accelerated by high temperatures, shortening the lifetime of the device; damage to junctions not leading to immediate failure may manifest as altered [[
* [[Thermal runaway]], where clusters in the substrate cause localised loss of [[thermal conductivity]], leading to damage producing more heat; the most common causes are voids caused by incomplete [[soldering]], electromigration effects and [[Kirkendall voiding]]. Clustered distribution of current density over the junction or [[current filament]]s lead to [[current crowding]] localised hot spots, which may evolve to a thermal runaway.
* [[Reverse bias]]. Some semiconductor devices are diode junction-based and are nominally rectifiers; however, the reverse-breakdown mode may be at a very low voltage, with a moderate reverse bias voltage causing immediate degradation and vastly accelerated failure. 5 V is a maximum reverse-bias voltage for typical LEDs, with some types having lower figures.
* Severely overloaded [[Zener diode]]s in reverse bias shorting. A sufficiently high voltage causes avalanche breakdown of the Zener junction; that and a large current being passed through the diode causes extreme localised heating, melting the junction and metallisation and forming a silicon-aluminium alloy that shorts the terminals. This is sometimes intentionally used as a method of hardwiring connections via fuses.<ref name="analogart"/>
* [[Latchup]]s (when the device is subjected to an over- or undervoltage pulse); a [[parasitic structure]] acting as a triggered [[Silicon-controlled rectifier|SCR]] then may cause an overcurrent-based failure. In ICs, latchups are classified as internal (like [[transmission line]] reflections and [[ground bounce]]s) or external (like signals introduced via I/O pins and [[cosmic ray]]s); external latchups can be triggered by an electrostatic discharge while internal latchups cannot. Latchups can be triggered by charge carriers injected into chip substrate or another latchup; the [[JEDEC78]] standard tests susceptibility to latchups.<ref name="micfailanal"/>
====Electrostatic discharge====
{{Main|Electrostatic discharge}}
Electrostatic discharge (ESD) is a subclass of electrical overstress and may cause immediate device failure, permanent parameter shifts and latent damage causing increased degradation rate. It has at least one of three components, localized heat generation, high current density and high electric field gradient; prolonged presence of currents of several amperes transfer energy to the device structure to cause damage. ESD in real circuits causes a [[damped wave]] with rapidly alternating polarity, the junctions stressed in the same manner; it has four basic mechanisms:<ref name="esdprotcmos">
* Oxide breakdown occurring at field strengths above 6–10 MV/cm.
* Junction damage manifesting as reverse-bias leakage increases to the point of shorting.
* Metallisation and polysilicon burnout, where damage is limited to metal and [[polysilicon]] interconnects, thin film resistors and diffused resistors.
* Charge injection, where hot carriers generated by avalanche breakdown are injected into the oxide layer.
Catastrophic ESD failure modes include:
* Junction burnout, where a conductive path forms through the junction and shorts it
* Metallisation burnout, where melting or vaporizing of a part of the metal interconnect interrupts it
* Oxide punch-through, formation of a conductive path through the insulating layer between two conductors or semiconductors; the [[gate oxide]]s are thinnest and therefore most sensitive. The damaged transistor shows a low-ohmic junction between gate and drain terminals.
A parametric failure only shifts the device parameters and may manifest in [[stress testing]]; sometimes, the degree of damage can lower over time. Latent ESD failure modes occur in a delayed fashion and include:
* Insulator damage by weakening of the insulator structures.
* Junction damage by lowering minority carrier lifetimes, increasing forward-bias resistance and increasing reverse-bias leakage.
* Metallisation damage by conductor weakening.
Catastrophic failures require the highest discharge voltages, are the easiest to test for and are rarest to occur. Parametric failures occur at intermediate discharge voltages and occur more often, with latent failures the most common. For each parametric failure, there are 4–10 latent ones.<ref name="contesd">{{cite book|url=
The [[gate oxide]] of some [[MOSFET]]s can be damaged by 50 volts of potential, the gate isolated from the junction and potential accumulating on it causing extreme stress on the thin dielectric layer; stressed oxide can shatter and fail immediately. The gate oxide itself does not fail immediately but can be accelerated by [[stress induced leakage current]], the oxide damage leading to a delayed failure after prolonged operation hours; on-chip capacitors using oxide or nitride dielectrics are also vulnerable. Smaller structures are more vulnerable because of their lower [[capacitance]], meaning the same amount of charge carriers charges the capacitor to a higher voltage. All thin layers of dielectrics are vulnerable; hence, chips made by processes employing thicker oxide layers are less vulnerable.<ref name="analogart">{{cite book|url=
Current-induced failures are more common in bipolar junction devices, where Schottky and PN junctions are predominant. The high power of the discharge, above 5 kilowatts for less than a microsecond, can melt and vaporise materials. Thin-film resistors may have their value altered by a discharge path forming across them, or having part of the thin film vaporized; this can be problematic in precision applications where such values are critical.<ref name="esdaz">{{cite book|url=
Newer CMOS [[output buffer]]s using lightly doped [[silicide]] drains are more ESD sensitive; the N-channel driver usually suffers damage in the oxide layer or n+/p well junction. This is
==Passive element failures==
===Resistors===
{{Main
[[File:Resistor damaged arcing.jpg|thumb|right|A resistor removed from a high voltage tube circuit shows damage from voltaic arcing on the resistive metal oxide layer.]]
Resistors can fail open or short, alongside their value changing under environmental conditions and outside performance limits. Examples of resistor failures include:
* Manufacturing defects causing intermittent problems. For example, improperly crimped caps on carbon or metal resistors can loosen and lose contact, and the resistor-to-cap resistance can change the values of the resistor<ref name="elecmatpack">
* Surface-mount resistors delaminating where dissimilar materials join, like between the ceramic substrate and the resistive layer.<ref name="cashistfail">
▲*Manufacturing defects causing intermittent problems. For example, improperly crimped caps on carbon or metal resistors can loosen and lose contact, and the resistor-to-cap resistance can change the values of the resistor<ref name="elecmatpack">[http://books.google.com/books?id=c2YxCCaM9RIC&pg=PA970&dq=resistor+failure&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&num=50&as_brr=3&cd=7#v=onepage&q=resistor%20failure&f=false Electronic Materials Handbook: Packaging] By Merrill L. Minges, ASM International. Handbook Committee, 1989, p. 970 ISBN 0-87170-285-1</ref>
* Nichrome thin-film resistors in integrated circuits attacked by phosphorus from the passivation glass, corroding them and increasing their resistance.<ref name="hybmictech">{{cite book|author1=James J. Licari|author2=Leonard R. Enlow|title=Hybrid Microcircuit Technology Handbook, 2nd Edition: Materials, Processes, Design, Testing and Production|url=https://books.google.com/books?id=VrFtH-xsu3sC&pg=PA506|year=2008|publisher=Elsevier Science|isbn=978-0-08-094659-7|page=506}}</ref>
▲*Surface-mount resistors delaminating where dissimilar materials join, like between the ceramic substrate and the resistive layer.<ref name="cashistfail">[http://books.google.com/books?id=Fk1rMBUO6AAC&printsec=frontcover#v=onepage&q=resistor&f=false Handbook of case histories in failure analysis, Volume 2] By Khlefa Alarbe Esaklul, ASM International,1993 ISBN 0-87170-495-1</ref>
* SMD resistors with silver metallization of contacts suffering open-circuit failure in a [[sulfur]]-rich environment, due to a buildup of [[silver sulfide]].<ref name="micelfailanal">
* Copper dendrites growing from [[Copper(II) oxide]] present in some materials (like the layer facilitating adhesion of metallization to a ceramic substrate) and bridging the trimming kerf slot.<ref name="istfa2008">{{cite book|author=ASM International|title=Thirty-fourth International Symposium for Testing and Failure Analysis|url=https://books.google.com/books?id=-FTgcUOx8GYC&pg=PA61|year=2008|publisher=ASM International|isbn=978-1-61503-091-0|page=61}}</ref>
▲*SMD resistors with silver metallization of contacts suffering open-circuit failure in a [[sulfur]]-rich environment, due to buildup of [[silver sulfide]].<ref name="micelfailanal">[http://books.google.com/books?id=OauJoOB8zl4C&pg=PA161&dq=resistor+failure&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&num=50&as_brr=3&cd=9#v=onepage&q=resistor%20failure&f=false Microelectronic failure analysis: desk reference: 2002 supplement] By Thomas W. Lee, ASM International, 2002, p. 161 ISBN 0-87170-769-1</ref>
====Potentiometers and trimmers====
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{{main|Capacitor}}
Capacitors are characterized by their [[capacitance]], parasitic resistance in series and parallel, [[breakdown voltage]] and [[dissipation factor]]; both parasitic parameters are often frequency- and voltage-dependent. 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.{{Citation needed|date=April 2011}} Some examples of capacitor failures include:
* [[Dielectric breakdown]] due to overvoltage or aging of the dielectric, occurring when breakdown voltage falls below operating voltage. Some types of capacitors
* Electrode materials migrating across the dielectric, forming conductive paths.<ref name="elecmatpack"/>▼
▲*[[Dielectric breakdown]] due to overvoltage or aging of the dielectric, occurring when breakdown voltage falls below operating voltage. Some types of capacitors have their internal arcing vaporizing parts of the electrodes around the failed spot to self-heal; others form a conductive pathway through the dielectric, leading to shorting or partial loss of dielectric resistance.<ref name="elecmatpack"/>
* Leads separated from the capacitor by rough handling during storage, assembly or operation, leading to an open failure. The failure can occur invisibly inside the packaging and is measurable.<ref name="elecmatpack"/>▼
▲*Electrode materials migrating across the dielectric, forming conductive paths.<ref name="elecmatpack"/>
* Increase of [[dissipation factor]] due to contamination of capacitor materials, particularly from flux and solvent residues.<ref name="elecmatpack"/>▼
▲*Leads separated from the capacitor by rough handling during storage, assembly or operation, leading to an open failure. The failure can occur invisibly inside the packaging and is measurable.<ref name="elecmatpack"/>
▲*Increase of [[dissipation factor]] due to contamination of capacitor materials, particularly from flux and solvent residues.<ref name="elecmatpack"/>
====Electrolytic capacitors====
In addition to the problems listed above, [[electrolytic capacitor]]s suffer from these failures:
* Aluminium versions having their electrolyte dry out for a gradual leakage, equivalent series resistance and loss of capacitance. Power dissipation by high ripple currents and internal resistances cause an increase of the capacitor's internal temperature beyond specifications, accelerating the deterioration rate; such capacitors usually fail short.<ref name="elecmatpack"/>
* Electrolyte contamination (like from moisture) corroding the electrodes, leading to capacitance loss and shorts.<ref name="elecmatpack"/>
* Electrolytes evolving a gas, increasing pressure inside the capacitor housing and sometimes causing an explosion; an example is the [[capacitor plague]].{{citation needed|date=September 2011}}
* [[Tantalum capacitor|Tantalum versions]] being electrically overstressed, permanently degrading the dielectric and sometimes causing open or short failure.<ref name="elecmatpack"/> Sites that have failed this way are usually visible as a discolored dielectric or as a locally melted anode.<ref name="micelfailanal"/>
===Metal oxide varistors===
{{Main|Varistor}}
Metal oxide [[varistor]]s typically have lower resistance as they heat up; if connected directly across a power bus, for protection against [[
==MEMS failures==
[[Microelectromechanical systems]] suffer from various types of failures:
* [[Stiction]] causing moving parts to stick; an external impulse sometimes restores functionality. Non-stick coatings, reduction of contact area, and increased awareness mitigate the problem in contemporary systems.<ref name="micfailanal"/>
* Particles migrating in the system and blocking their movements. Conductive particles may short out circuits like electrostatic actuators. [[Wear]] damages the surfaces and releases debris that can be a source of particle contamination.
* [[Fracture]]s causing loss of mechanical parts.
* [[Material fatigue]] inducing cracks in moving structures.
* Dielectric charging leading to change of functionality and at some point parameter failures.<ref name="memsdielcharging">Herfst, R.W., Steeneken, P.G., Schmitz, J., Time and voltage dependence of dielectric charging in RF MEMS capacitive switches, (2007) Annual Proceedings – Reliability Physics (Symposium), art. no. 4227667, pp. 417–421.
==Recreating failure modes==
In order to reduce failures, a precise knowledge of bond strength quality measurement during product design and subsequent manufacture is of vital importance. The best place to start is with the failure mode. This is based on the assumption that there is a particular failure mode, or range of modes, that may occur within a product. It is therefore reasonable to assume that the bond test should replicate the mode, or modes of interest. However, exact replication is not always possible. The test load must be applied to some part of the sample and transferred through the sample to the bond. If this part of the sample is the only option and is weaker than the bond itself, the sample will fail before the bond.<ref name="sykes">{{cite web |url=http://www.xyztec.com/bondtesting/ |title=Why test bonds? |first=Bob |last=Sykes |publisher=Global SMT & Packaging magazine |date=June 2010 |access-date=20 June 2014 |archive-date=3 July 2018 |archive-url=https://web.archive.org/web/20180703163225/https://www.xyztec.com/bondtesting/ |url-status=dead }}</ref>
==See also==
* [[Reliability (semiconductor)]]
==References==
{{
==Further reading==
*Herfst, R.W., Steeneken, P.G., Schmitz, J., Time and voltage dependence of dielectric charging in RF MEMS capacitive switches, (2007) Annual Proceedings – Reliability Physics (Symposium), art. no. 4227667, pp. 417–421.
==External links==
* http://www.esda.org - ESD Association
{{Electronic systems}}
[[Category:Semiconductor device defects]]
[[Category:
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