Some different capacitors for electronic equipmentare manufactured in many forms, styles, lengths, girths, and from many materials. They all contain at least two (called 'plates') separated by an layer (called the ). Capacitors are widely used as parts of in many common electrical devices.Capacitors, together with, and, belong to the group of ' used in.

1. Standard Values Of Ceramic Capacitors
2. Ceramic Capacitor Values
3. Standard Capacitor Sizes

Standard Values Of Ceramic Capacitors

Although, in absolute figures, the most common capacitors are integrated capacitors (e.g. In or structures), this article is concentrated on the various styles of capacitors as discrete components.Small capacitors are used in electronic devices to couple signals between stages of amplifiers, as components of electric filters and tuned circuits, or as parts of power supply systems to smooth rectified current. Larger capacitors are used for energy storage in such applications as strobe lights, as parts of some types of electric motors, or for correction in AC power distribution systems. Standard capacitors have a fixed value of, but adjustable capacitors are frequently used in tuned circuits.

If there are only two digits listed, the number is simply the capacitance in pF. Thus, the digits 22 indicate a 22 pF capacitor. This shows how some common capacitor values are represented using this notation: You may also see a letter printed on the capacitor to indicate the tolerance. Capacitors are routinely marked with at least their capacitance value; many capacitors are also marked with value tolerance notation, and a breakdown voltage.

Different types are used depending on required capacitance, working voltage, current handling capacity, and other properties. Schematic of double layer capacitor.1. IHP Inner Helmholtz Layer2. OHP Outer Helmholtz Layer3. Diffuse layer4. Solvated ions5.

Specifically adsorptive ions (Pseudocapacitance)6. Solvent molecule.Another type – the capacitor – makes use of two other storage principles to store electric energy. In contrast to ceramic, film, and, (also known as electrical double-layer capacitors (EDLC) or ultracapacitors) do not have a conventional dielectric. The capacitance value of an electrochemical capacitor is determined by two high-capacity storage principles.

These principles are:. storage within achieved on the between the surface of the and the (double-layer capacitance); and. storage achieved by a by specifically adsorpted with (pseudocapacitance). Unlike batteries, in these reactions, the ions simply cling to the atomic structure of an electrode without making or breaking chemical bonds, and no or negligibly small chemical modifications are involved in charge/discharge.The ratio of the storage resulting from each principle can vary greatly, depending on electrode design and electrolyte composition. Pseudocapacitance can increase the capacitance value by as much as an order of magnitude over that of the double-layer by itself. Common capacitors and their names Capacitors are divided into two mechanical groups: Fixed capacitors with fixed capacitance values and variable capacitors with variable (trimmer) or adjustable (tunable) capacitance values.The most important group is the fixed capacitors. Many got their names from the dielectric.

For a systematic classification these characteristics can't be used, because one of the oldest, the electrolytic capacitor, is named instead by its cathode construction. Charge storage principles of different capacitor types and their inherent voltage progressionThe most common dielectrics are:. Ceramics. Plastic films. layer on metal (, ). Natural materials like,All of them store their electrical charge statically within an between two (parallel) electrodes.Beneath this conventional capacitors a family of electrochemical capacitors called was developed. Supercapacitors don't have a conventional dielectric.

They store their electrical charge statically in and faradaically at the surface of electrodes. with static in a and. with (faradaic charge transfer) in a.

or with both storage principles together in.The most important material parameters of the different dielectrics used and the appr. Helmholtz-layer thickness are given in the table below.Key parameters Capacitor styleDielectricRelativePermittivityat 1 kHzMaximum/realized.dielectric strengthV/µmMinimum thicknessof the dielectricµm,Class 112–40. Main article:A is a non-polarized fixed capacitor made out of two or more alternating layers of ceramic and metal in which the ceramic material acts as the dielectric and the metal acts as the electrodes.

The ceramic material is a mixture of finely ground granules of or materials, modified by mixed that are necessary to achieve the capacitor's desired characteristics. The electrical behavior of the ceramic material is divided into two stability classes:. ceramic capacitors with high stability and low losses compensating the influence of temperature in resonant circuit application.

Common / code abbreviations are /NP0, P2G/N150, R2G/N220, U2J/N750 etc. ceramic capacitors with high for buffer, by-pass and coupling applications Common EIA/IEC code abbreviations are: X7R/2XI, Z5U/E26, Y5V/2F4, X7S/2C1, etc.The great plasticity of ceramic raw material works well for many special applications and enables an enormous diversity of styles, shapes and great dimensional spread of ceramic capacitors.

The smallest discrete capacitor, for instance, is a '01005' chip capacitor with the dimension of only 0.4 mm × 0.2 mm.The construction of ceramic multilayer capacitors with mostly alternating layers results in single capacitors connected in parallel. This configuration increases capacitance and decreases all losses and parasitic. Three examples of different film capacitor configurations for increasing surge current ratingsor plastic film capacitors are non-polarized capacitors with an insulating plastic film as the dielectric. The dielectric films are drawn to a thin layer, provided with metallic electrodes and wound into a cylindrical winding. The electrodes of film capacitors may be metallized aluminum or zinc, applied on one or both sides of the plastic film, resulting in metallized film capacitors or a separate metallic foil overlying the film, called film/foil capacitors.Metallized film capacitors offer self-healing properties. Dielectric breakdowns or shorts between the electrodes do not destroy the component. The metallized construction makes it possible to produce wound capacitors with larger capacitance values (up to 100 µF and larger) in smaller cases than within film/foil construction.Film/foil capacitors or metal foil capacitors use two plastic films as the dielectric.

Each film is covered with a thin metal foil, mostly aluminium, to form the electrodes. The advantage of this construction is the ease of connecting the metal foil electrodes, along with an excellent current pulse strength.A key advantage of every film capacitor's internal construction is direct contact to the electrodes on both ends of the winding. This contact keeps all current paths very short. The design behaves like a large number of individual capacitors connected in parallel, thus reducing the internal losses.

The inherent geometry of film capacitor structure results in low ohmic losses and a low parasitic inductance, which makes them suitable for applications with high surge currents and for AC power applications, or for applications at higher frequencies.The plastic films used as the dielectric for film capacitors are (PP), (PET), (PPS), (PEN), and or (PTFE). Polypropylene film material with a market share of something about 50% and Polyester film with something about 40% are the most used film materials. The rest of something about 10% will be used by all other materials including PPS and paper with roughly 3%, each. Characteristics of plastic film materials for film capacitorsFilm material, abbreviated codesFilm characteristicsPETPENPPSPPRelative permittivity at 1 kHz3.33.03.02.2Minimum film thickness (µm)0.7–0.90.9–1.41.22.4–3.0Moisture absorption (%)low0.40.05. MKV power capacitor, double-sided metallized paper (field-free mechanical carrier of the electrodes), polypropylene film (dielectric), windings impregnated with insulating oilA related type is the.

The materials and construction techniques used for large power film capacitors mostly are similar to those of ordinary film capacitors. However, capacitors with high to very high power ratings for applications in power systems and electrical installations are often classified separately, for historical reasons. The standardization of ordinary film capacitors is oriented on electrical and mechanical parameters. The standardization of power capacitors by contrast emphasizes the safety of personnel and equipment, as given by the local regulating authority.As modern electronic equipment gained the capacity to handle power levels that were previously the exclusive domain of 'electrical power' components, the distinction between the 'electronic' and 'electrical' power ratings blurred. Historically, the boundary between these two families was approximately at a reactive power of 200 volt-amperes.Film power capacitors mostly use polypropylene film as the dielectric. Other types include metallized paper capacitors (MP capacitors) and mixed dielectric film capacitors with polypropylene dielectrics.

MP capacitors serve for cost applications and as field-free carrier electrodes (soggy foil capacitors) for high AC or high current pulse loads. Windings can be filled with an insulating oil or with to reduce air bubbles, thereby preventing short circuits.They find use as converters to change voltage, current or frequency, to store or deliver abruptly electric energy or to improve the power factor. The rated voltage range of these capacitors is from approximately 120 V AC (capacitive lighting ballasts) to 100 kV.

Power film capacitors for applications in power systems, electrical installations and plants. Electrolytic capacitors diversificationhave a metallic anode covered with an oxidized layer used as dielectric.

The second electrode is a non-solid (wet) or solid electrolyte. Electrolytic capacitors are polarized. Three families are available, categorized according to their dielectric. with as dielectric. with as dielectric. with as dielectric.The anode is highly roughened to increase the surface area.

This and the relatively high permittivity of the oxide layer gives these capacitors very high capacitance per unit volume compared with film- or ceramic capacitors.The permittivity of tantalum pentoxide is approximately three times higher than aluminium oxide, producing significantly smaller components. However, permittivity determines only the dimensions. Electrical parameters, especially, are established by the electrolyte's material and composition. Three general types of electrolytes are used:. non solid (wet, liquid)—conductivity approximately 10 mS/cm and are the lowest cost. solid manganese oxide—conductivity approximately 100 mS/cm offer high quality and stability.

solid conductive polymer ( or )—conductivity approximately 100.500 S/cm, offer ESR values as low as. Classification of supercapacitors into classes regarding to IEC 62391-1, IEC 62567and DIN EN 61881-3 standardsSupercapacitors (SC), comprise a family of. Supercapacitor, sometimes called ultracapacitor is a generic term for (EDLC), and hybrid capacitors. They don't have a conventional solid. The capacitance value of an electrochemical capacitor is determined by two storage principles, both of which contribute to the total capacitance of the capacitor:. – Storage is achieved by separation of charge in a at the between the surface of a conductor and an electrolytic solution. The distance of separation of charge in a double-layer is on the order of a few (0.3–0.8 ).

This storage is in origin. – Storage is achieved by, electrosorbtion or on the surface of the electrode or by specifically adsorpted that results in a reversible. The pseudocapacitance is faradaic in origin.The ratio of the storage resulting from each principle can vary greatly, depending on electrode design and electrolyte composition. Vacuum capacitor with uranium glass encapsulationVariable capacitors may have their capacitance changed by mechanical motion. Generally two versions of variable capacitors has to be to distinguished.

Tuning capacitor – variable capacitor for intentionally and repeatedly tuning an oscillator circuit in a radio or another tuned circuit. Trimmer capacitor – small variable capacitor usually for one-time oscillator circuit internal adjustmentVariable capacitors include capacitors that use a mechanical construction to change the distance between the plates, or the amount of plate surface area which overlaps. They mostly use air as dielectric medium.Semiconductive are not capacitors in the sense of passive components but can change their capacitance as a function of the applied reverse bias voltage and are used like a variable capacitor.

They have replaced much of the tuning and trimmer capacitors. Variable capacitors. Trimmer capacitor for surface mountingComparison of types Features and applications as well as disadvantages of capacitorsCapacitor typeDielectricFeatures/applicationsDisadvantagesCeramic capacitorsCeramic Class 1 capacitorsceramic mixture of modified by additivesPredictable and low change with.

Excellent high characteristics with low losses. For temperature compensation in application. Available in voltages up to 15,000 VLow ceramic, capacitors with low, larger dimensions than Class 2 capacitorsCeramic Class 2 capacitorsceramic mixture of and suitable additivesHigh permittivity, high volumetric efficiency, smaller dimensions than Class 1 capacitors. For buffer, by-pass and coupling applications.

Available in voltages up to 50,000 V.Lower stability and higher losses than Class 1. Capacitance changes with change in applied voltage, with frequency and with aging effects. SlightlyFilm capacitorsMetallized film capacitorsPP, PET, PEN, PPS, (PTFE)Metallized film capacitors are significantly smaller in size than film/foil versions and have self-healing properties.Thin metallized electrodes limit the maximum carrying capability respectively the maximum possible pulse voltage.Film/foil film capacitorsPP, PET, PTFEFilm/foil film capacitors have the highest surge ratings/pulse voltage, respectively. Peak currents are higher than for metallized types.No self-healing properties: internal short may be disabling.

Larger dimensions than metallized alternative.Polypropylene (PP) film capacitorsMost popular film capacitor dielectric. Predictable linear and low capacitance change with operating temperature. Suitable for applications in Class-1 frequency-determining circuits and precision analog applications. Very narrow capacitances. Extremely low dissipation factor. Low moisture absorption, therefore suitable for 'naked' designs with no coating. High insulation resistance.

Usable in high power applications such as snubber or IGBT. Used also in applications, such as in motors.

Very low dielectric losses. High frequency and high power applications such as. Widely used for safety/EMI suppression, including connection to power supply mains.Maximum operating temperature of 105 °C. Relatively low permittivity of 2.2. PP film capacitors tend to be larger than other film capacitors. More susceptible to damage from transient over-voltages or voltage reversals than oil-impregnated MKV-capacitors for applications.Polyester (PET) film(Mylar) capacitorsPolyethylene terephthalate, (Hostaphan®, Mylar®)Smaller in size than functionally comparable polypropylene film capacitors.

Low moisture absorption. Have almost completely replaced metallized paper and polystyrene film for most DC applications.

Mainly used for general purpose applications or semi-critical circuits with operating temperatures up to 125 °C. Operating voltages up to 60,000 V DC.Usable at low (AC power) frequencies. Limited use in power electronics due to higher losses with increasing temperature and frequency.Polyethylene naphthalate(PEN) film capacitors(Kaladex®)Better stability at high temperatures than PET.

More suitable for high temperature applications and for SMD packaging. Mainly used for non-critical filtering, coupling and decoupling, because temperature dependencies are not significant.Lower relative permittivity and lower dielectric strength imply larger dimensions for a given capacitance and rated voltage than PET.Polyphenylene Sulfide (PPS)film capacitorsPolyphenylene (Torelina®)Small temperature dependence over the entire temperature range and a narrow frequency dependence in a wide frequency range. Dissipation factor is quite small and stable.

Operating temperatures up to 270 °C. Suitable for SMD. Tolerate increased reflow soldering temperatures for lead-free soldering mandated by theAbove 100 °C, the dissipation factor increases, increasing component temperature, but can operate without degradation. Cost is usually higher than PP.Polytetrafluoroethylene (PTFE)( film) capacitors(Teflon®)Lowest loss solid dielectric.

Operating temperatures up to 250 °C. Extremely high insulation resistance. Good stability. Used in mission-critical applications.Large size (due to low dielectric constant). Higher cost than other film capacitors.Polycarbonate (PC)film capacitorsAlmost completely replaced by PPLimited manufacturersPolystyrene (PS)film capacitors(Styroflex)Good thermal stability, high insulation, low distortion but unsuited to and now almost completely replaced by PETLimited manufacturersPolysulphone film capacitorsSimilar to polycarbonate. Withstand full voltage at comparatively higher temperatures.Only development, no series found (2012)Polyamide film capacitorsOperating temperatures of up to 200 °C. High insulation resistance.

Good stability. Low dissipation factor.Only development, no series found (2012)Polyimide film(Kapton) capacitors(Kapton)Highest dielectric strength of any known plastic film dielectric.Only development, no series found (2012)Film-based power capacitorsMetallized paper power capacitorsimpregnated with insulating oil or epoxy resinSelf-healing properties. Originally impregnated with wax, oil or epoxy. Oil-Kraft paper version used in certain applications. Mostly replaced by PP.Large size. Highly, absorbing from the despite plastic enclosures and impregnates.

Moisture increases dielectric losses and decreases resistance.Paper film/foil power capacitorsimpregnated with oilPaper covered with metal foils as electrodes. Intermittent duty, high discharge applications.Physically large and heavy. Significantly lower energy density than PP dielectric. Not self-healing. Potential catastrophic failure due to high stored energy.PP dielectric,field-free paperpower capacitors(MKV power capacitors)Double-sided (field-free) metallized paper as electrode carrier. PP as dielectic, impregnated with insulating oil, epoxy resin or insulating gasSelf-healing.

Very low losses. High insulation resistance. High inrush current strength.

High thermal stability. Heavy duty applications such as commutating with high reactive power, high frequencies and a high peak current load and other AC applications.Physically larger than PP power capacitors.Single- or double-sidedmetallized PP power capacitorsPP as dielectric, impregnated with insulating oil, epoxy resin or insulating gasHighest capacitance per volume power capacitor. Broad range of applications such as general-purpose, AC capacitors, smoothing or filtering, DC links, snubbing or clamping, damping AC, series resonant DC circuits, DC discharge, AC commutation, AC power factor correction.critical for reliable high voltage operation and very high inrush current loads, limited heat resistance (105 °C)PP film/foil power capacitorsImpregnated PP or insulating gas, insulating oil, epoxy resin or insulating gasHighest inrush current strengthLarger than the PP metallized versions. Not self-healing.Electrolytic capacitorsElectrolytic capacitorswith non solid(wet, liquid)electrolyteAluminum oxideAl 2O 3Very large capacitance to volume ratio. Capacitance values up to 2,700,000 µF/6.3 V.

Voltage up to 550 V. Lowest cost per capacitance/voltage values. Used where low losses and high capacitance stability are not of major importance, especially for lower frequencies, such as by-pass, coupling, smoothing and buffer applications in power supplies and DC-links.Polarized. Significant leakage.

Ceramic Capacitor Values

Relatively high ESR and ESL values, limiting high ripple current and high frequency applications. Lifetime calculation required because drying out phenomenon. Vent or burst when overloaded, overheated or connected wrong polarized. Water based electrolyte may vent at end-of-life, showing failures like 'Tantalum pentoxideTa 2O 5Wet tantalum electrolytic capacitors (wet slug) Lowest leakage among electrolytics. Voltage up to 630 V (tantalum film) or 125 V (tantalum sinter body). Hermetically sealed.

Stable and reliable. Military and space applications.Polarized. Violent explosion when voltage, ripple current or slew rates are exceeded, or under reverse voltage. Expensive.Electrolytic capacitorswith solid electrolyteAluminum oxideAl2O3Tantalum pentoxideTa 2O 5,Niobium pentoxideNb2O5Tantalum and niobium with smaller dimensions for a given capacitance/voltage vs aluminum. Stable electrical parameters. Good long-term high temperature performance.

Lower ESR lower than non-solid (wet) electrolytics.Polarized. Low voltage and limited, transient, reverse or surge voltage tolerance. Possible combustion upon failure. ESR much higher than conductive polymer electrolytics. Manganese expected to be replaced by polymer.Electrolytic capacitorswith solid electrolyteAluminum oxideAl2O3,Tantalum pentoxideTa 2O 5,Niobium pentoxideNb2O5Greatly reduced ESR compared with manganese or non-solid (wet) elelectrolytics. Higher ripple current ratings.

Extended operational life. Stable electrical parameters.

Used for smoothing and buffering in smaller power supplies especially in SMD.Polarized. Highest leakage current among electrolytics. Higher prices than non-solid or manganese dioxide. Voltage limited to about 100 V. Explodes when voltage, current, or slew rates are exceeded or under reverse voltage.SupercapacitorsSupercapacitorsPseudocapacitorsHelmholtz double-layer plus faradaic pseudo-capacitanceEnergy density typically tens to hundreds of times greater than conventional electrolytics. More comparable to batteries than to other capacitors. Large capacitance/volume ratio.

Relatively low ESR. Thousands of farads. RAM memory backup. Temporary power during battery replacement. Rapidly absorbs/delivers much larger currents than batteries. Hundreds of thousands of charge/discharge cycles.

Hybrid vehicles. Low operating voltage per cell. (Stacked cells provide higher operating voltage.) Relatively high cost.Hybrid capacitors(LIC)Helmholtz double-layer plus faradaic pseudo-capacitance. Anode doped with ions.Higher operating voltage.

Higher energy density than common EDLCs, but smaller than (LIB). No thermal runaway reactions.Polarized. Low operating voltage per cell.

(Stacked cells provide higher operating voltage.) Relatively high cost.Miscellaneous capacitorsAir gap capacitorsLow dielectric loss. Used for resonating HF circuits for high power HF welding.Physically large.

Relatively low capacitance.Vacuum capacitorsExtremely low losses. Used for high voltage, high power RF applications, such as transmitters and induction heating. Self-healing if current is limited.Very high cost. Relatively low capacitance.SF6-gas filled capacitorsgasHigh precision.

Extremely low losses. Very high stability. Up to 1600 kV rated voltage. Used as capacitance standard in measuring bridge circuits.Very high costMetallized mica (Silver mica) capacitorsVery high stability.

Used for HF and low VHF RF circuits and as capacitance standard in measuring bridge circuits. Mostly replaced by Class 1 ceramic capacitorsHigher cost than class 1 ceramic capacitorsGlass capacitorsBetter stability and frequency than silver mica. Resistant to nuclear radiation.

Operating temperature: −75 °C to +200 °C and even short overexposure to +250 °C.Higher cost than class 1 ceramicIntegrated capacitorsThin (down to 100 µm). Smaller footprint than most MLCC. Very high stability up to 200 °C. High reliabilityCustomized productionVariable capacitorsAir gap tuning capacitorsAirCircular or various logarithmic cuts of the rotor electrode for different capacitance curves. Split rotor or stator cut for symmetric adjustment. Axis for noise reduced adjustment. For high professional devices.Large dimensions.

High cost.Vacuum tuning capacitorsVacuumExtremely low losses. Used for high voltage, high power RF applications, such as transmitters and induction heating. Self-healing if arc-over current is limited.Very high cost. Large dimensions.SF6 gas filled tuning capacitorSF6Extremely low losses. Used for very high voltage high power RF applications.Very high cost, fragile, large dimensionsAir gap trimmer capacitorsAirMostly replaced by semiconductive variable capacitance diodesHigh costCeramic trimmer capacitorsClass 1 ceramicLinear and stable frequency behavior over wide temperature rangeHigh costElectrical characteristics Series-equivalent circuit. Series-equivalent circuit model of a capacitorDiscrete capacitors deviate from the ideal capacitor. An ideal capacitor only stores and releases electrical energy, with no dissipation.

Capacitor components have losses and parasitic inductive parts. These imperfections in material and construction can have positive implications such as linear frequency and temperature behavior in class 1 ceramic capacitors. Conversely, negative implications include the non-linear, voltage-dependent capacitance in class 2 ceramic capacitors or the insufficient dielectric insulation of capacitors leading to leakage currents.All properties can be defined and specified by a series equivalent circuit composed out of an idealized capacitance and additional electrical components which model all losses and inductive parameters of a capacitor. Frequency dependence of capacitance for film capacitors with different film materialsFor electrolytic capacitors with non-solid electrolyte, mechanical motion of the occurs. Their movability is limited so that at higher frequencies not all areas of the roughened anode structure are covered with charge-carrying ions.

As higher the anode structure is roughened as more the capacitance value decreases with increasing frequency. Low voltage types with highly roughened anodes display capacitance at 100 kHz approximately 10 to 20% of the value measured at 100 Hz.Voltage dependence Capacitance may also change with applied voltage. This effect is more prevalent in class 2 ceramic capacitors. The permittivity of ferroelectric class 2 material depends on the applied voltage.

Higher applied voltage lowers permittivity. The change of capacitance can drop to 80% of the value measured with the standardized measuring voltage of 0.5 or 1.0 V. This behavior is a small source of non-linearity in low-distortion filters and other analog applications. In audio applications this can cause distortion (measured using ).Film capacitors and electrolytic capacitors have no significant voltage dependence. Voltage dependence of capacitance for some different class 2 ceramic capacitors. Relation between rated and category temperature range and applied voltageThe voltage at which the dielectric becomes conductive is called the breakdown voltage, and is given by the product of the dielectric strength and the separation between the electrodes. The dielectric strength depends on temperature, frequency, shape of the electrodes, etc.

Because a breakdown in a capacitor normally is a short circuit and destroys the component, the operating voltage is lower than the breakdown voltage. The operating voltage is specified such that the voltage may be applied continuously throughout the life of the capacitor.In IEC/EN 60384-1 the allowed operating voltage is called 'rated voltage' or 'nominal voltage'.

The rated voltage (UR) is the maximum DC voltage or peak pulse voltage that may be applied continuously at any temperature within the rated temperature range.The voltage proof of nearly all capacitors decreases with increasing temperature. Some applications require a higher temperature range.

Lowering the voltage applied at a higher temperature maintains safety margins. For some capacitor types therefore the IEC standard specify a second 'temperature derated voltage' for a higher temperature range, the 'category voltage'. The category voltage (UC) is the maximum DC voltage or peak pulse voltage that may be applied continuously to a capacitor at any temperature within the category temperature range.The relation between both voltages and temperatures is given in the picture right.Impedance. Limiting conditions for capacitors operating with AC loadsAn AC load only can be applied to a non-polarized capacitor. Capacitors for AC applications are primarily film capacitors, metallized paper capacitors, ceramic capacitors and bipolar electrolytic capacitors.The rated AC load for an AC capacitor is the maximum sinusoidal effective AC current (rms) which may be applied continuously to a capacitor within the specified temperature range. In the datasheets the AC load may be expressed as. rated AC voltage at low frequencies,.

rated reactive power at intermediate frequencies,. reduced AC voltage or rated AC current at high frequencies. Solid, polymerFor electrolytic capacitors the insulation resistance of the dielectric is termed 'leakage current'. This is represented by the resistor R leak in parallel with the capacitor in the series-equivalent circuit of electrolytic capacitors.

This resistance between the terminals of a capacitor is also finite. R leak is lower for electrolytics than for ceramic or film capacitors.The leakage current includes all weak imperfections of the dielectric caused by unwanted chemical processes and mechanical damage. It is also the DC current that can pass through the dielectric after applying a voltage. It depends on the interval without voltage applied (storage time), the thermic stress from soldering, on voltage applied, on temperature of the capacitor, and on measuring time.The leakage current drops in the first minutes after applying DC voltage. In this period the dielectric oxide layer can self-repair weaknesses by building up new layers.

The time required depends generally on the electrolyte. Solid electrolytes drop faster than non-solid electrolytes but remain at a slightly higher level.The leakage current in non-solid electrolytic capacitors as well as in manganese oxide solid tantalum capacitors decreases with voltage-connected time due to self-healing effects. Although electrolytics leakage current is higher than current flow over insulation resistance in ceramic or film capacitors, the self-discharge of modern non solid electrolytic capacitors takes several weeks.A particular problem with electrolytic capacitors is storage time. Higher leakage current can be the result of longer storage times. These behaviors are limited to electrolytes with a high percentage of water. Organic solvents such as do not have high leakage with longer storage times.Leakage current is normally measured 2 or 5 minutes after applying rated voltage.Microphonics All ferroelectric materials exhibit a piezoelectric effect.

Because Class 2 ceramic capacitors use ferroelectric ceramics dielectric, these types of capacitors may have electrical effects called. Microphonics (microphony) describes how electronic components transform mechanical into an undesired electrical signal. The dielectric may absorb mechanical forces from shock or vibration by changing thickness and changing the electrode separation, affecting the capacitance, which in turn induces an AC current.

The resulting interference is especially problematic in audio applications, potentially causing feedback or unintended recording.In the reverse microphonic effect, varying the electric field between the capacitor plates exerts a physical force, turning them into an audio speaker. High current impulse loads or high ripple currents can generate audible sound from the capacitor itself, draining energy and stressing the dielectric. Dielectric absorption (soakage).

Aging of different Class 2 ceramic capacitors compared with NP0-Class 1 ceramic capacitorIn Class 2 ceramic capacitors, capacitance decreases over time. This behavior is called 'aging'.

This aging occurs in ferroelectric dielectrics, where domains of polarization in the dielectric contribute to the total polarization. Degradation of polarized domains in the dielectric decreases permittivity and therefore capacitance over time.

The aging follows a logarithmic law. This defines the decrease of capacitance as constant percentage for a time decade after the soldering recovery time at a defined temperature, for example, in the period from 1 to 10 hours at 20 °C. As the law is logarithmic, the percentage loss of capacitance will twice between 1 h and 100 h and 3 times between 1 h and 1,000 h and so on. Aging is fastest near the beginning, and the absolute capacitance value stabilizes over time.The rate of aging of Class 2 ceramic capacitors depends mainly on its materials. Generally, the higher the temperature dependence of the ceramic, the higher the aging percentage.

The typical aging of X7R ceramic capacitors is about 2.5% per decade. The aging rate of Z5U ceramic capacitors is significantly higher and can be up to 7% per decade.The aging process of Class 2 ceramic capacitors may be reversed by heating the component above the.Class 1 ceramic capacitors and film capacitors do not have ferroelectric-related aging.

Environmental influences such as higher temperature, high humidity and mechanical stress can, over a longer period, lead to a small irreversible change in the capacitance value sometimes called aging, too.The change of capacitance for P 100 and N 470 Class 1 ceramic capacitors is lower than 1%, for capacitors with N 750 to N 1500 ceramics it is ≤ 2%. Film capacitors may lose capacitance due to self-healing processes or gain it due to humidity influences. Typical changes over 2 years at 40 °C are, for example, ±3% for PE film capacitors and ±1% PP film capacitors.Life time. The electrical values of electrolytic capacitors with non-solid electrolyte changes over the time due to evaporation of electrolyte. Reaching specified limits of the parameters the capacitors will be count as 'wear out failure'.Electrolytic capacitors with non-solid electrolyte age as the electrolyte evaporates.

This evaporation depends on temperature and the current load the capacitors experience. Electrolyte escape influences capacitance and ESR. Capacitance decreases and the ESR increases over time. In contrast to ceramic, film and electrolytic capacitors with solid electrolytes, 'wet' electrolytic capacitors reach a specified 'end of life' reaching a specified maximum change of capacitance or ESR. End of life, 'load life' or 'lifetime' can be estimated either by formula or diagrams or roughly by a so-called '10-degree-law'. A typical specification for an electrolytic capacitor states a lifetime of 2,000 hours at 85 °C, doubling for every 10 degrees lower temperature, achieving lifespan of approximately 15 years at room temperature.Supercapacitors also experience electrolyte evaporation over time. Estimation is similar to wet electrolytic capacitors.

Additional to temperature the voltage and current load influence the life time. Lower voltage than rated voltage and lower current loads as well as lower temperature extend the life time.Failure rate. The life time (load life) of capacitors correspondents with the time of constant random failure rate shown in the. For electrolytic capacitors with non-solid electrolyte and supercapacitors ends this time with the beginning of wear out failures due to evaporation of electrolyteCapacitors are components with low, achieving life expectancies of decades under normal conditions.

Most capacitors pass a test at the end of production similar to a ', so that early failures are found during production, reducing the number of post-shipment failures.Reliability for capacitors is usually specified in numbers of (FIT) during the period of constant random failures. FIT is the number of failures that can be expected in one billion (10 9) component-hours of operation at fixed working conditions (e.g. 1000 devices for 1 million hours, or 1 million devices for 1000 hours each, at 40 °C and 0.5 U R). For other conditions of applied voltage, current load, temperature, mechanical influences and humidity the FIT can recalculated with terms standardized for industrial or military contexts.Additional information Soldering Capacitors may experience changes to electrical parameters due to environmental influences like soldering, mechanical stress factors (vibration, shock) and humidity. The greatest stress factor is soldering. The heat of the solder bath, especially for SMD capacitors, can cause ceramic capacitors to change contact resistance between terminals and electrodes; in film capacitors, the film may shrink, and in wet electrolytic capacitors the electrolyte may boil.

Standard Capacitor Sizes

A recovery period enables characteristics to stabilize after soldering; some types may require up to 24 hours. Some properties may change irreversibly by a few per cent from soldering.Electrolytic behavior from storage or disuse Electrolytic capacitors with non-solid electrolyte are 'aged' during manufacturing by applying rated voltage at high temperature for a sufficient time to repair all cracks and weaknesses that may have occurred during production. Some electrolytes with a high water content react quite aggressively or even violently with unprotected aluminum. This leads to a 'storage' or 'disuse' problem of electrolytic capacitors manufactured before the 1980s. Chemical processes weaken the oxide layer when these capacitors are not used for too long. New electrolytes with 'inhibitors' or 'passivators' were developed during the 1980s to solve this problem.As of 2012 the standard storage time for electronic components of two years at room temperature substantiates (cased) by the oxidation of the terminals will be specified for electrolytic capacitors with non-solid electrolytes, too.

Special series for 125 °C with organic solvents like are specified up to 10 years storage time ensure without pre-condition the proper electrical behavior of the capacitors.For antique radio equipment, 'pre-conditioning' of older electrolytic capacitors may be recommended. This involves applying the operating voltage for some 10 minutes over a current limiting resistor to the terminals of the capacitor. Capacitor symbols Markings Imprinted Capacitors, like most other electronic components and if enough space is available, have imprinted markings to indicate manufacturer, type, electrical and thermal characteristics, and date of manufacture. Supercapacitors are marked at the cathode ( minus) sideMarket segments Discrete capacitors today are industrial products produced in very large quantities for use in electronic and in electrical equipment. Globally, the market for fixed capacitors was estimated at approximately US$18 billion in 2008 for 1,400 billion (1.4 × 10 12) pieces. This market is dominated by ceramic capacitors with estimate of approximately one trillion (1 × 10 12) items per year.Detailed estimated figures in value for the main capacitor families are:. —US$8.3 billion (46%);.

—US$3.9 billion (22%);. and Paper capacitors—US$2.6 billion, (15%);. —US$2.2 billion (12%);. —US$0.3 billion (2%); and. Others like and —US$0.7 billion (3%).All other capacitor types are negligible in terms of value and quantity compared with the above types.See also.