Aluminium electrolytic capacitors with non-solid electrolyte have a wide range of styles, sizes and series Aluminum electrolytic capacitors are polarized whose (+) is made of a pure foil with an surface. The aluminum forms a very thin insulating layer of by that acts as the of the capacitor. A non-solid covers the rough surface of the oxide layer, serving in principle as the second electrode () (-) of the capacitor.

PRODUCT DATA SHEET 5 TYPICAL PROPERTIES: Typical property values of Silicone II* Aluminum & Metal sealant as supplied and cured are set forth in the tables below. Reference intensities; standard; x-ray diffraction. The Powder Diffraction File (PDF) is a con tinuing compilation of diffraction patterns gathered from many sources. Produced and published by the. JCPDS International Centre for Diffraction Data,1 the PDF is used for identification of crystalline materials.

A second aluminum foil called “cathode foil” contacts the electrolyte and serves as the electrical connection to the negative terminal of the capacitor. Aluminum electrolytic capacitors are divided into three subfamilies by the type of electrolyte: • non-solid (liquid, wet) aluminum electrolytic capacitors, •, and •. Aluminum electrolytic capacitors with non-solid electrolyte are the most inexpensive type and also those with widest range of sizes, capacitance and voltage values. They are made with capacitance values from 0.1 µF up to 2,700,000 µF (2.7 F), and rated voltages values from 4 V up to 630 V. The liquid electrolyte provides oxygen for re-forming or self-healing of the dielectric oxide layer.

However, it can evaporate through a temperature-dependent drying-out process, which causes electrical parameters to drift, limiting the service life time of the capacitors. Due to their relatively high capacitance values aluminum electrolytic capacitors have low values even at lower frequencies like. They are typically used in, and for smoothing and buffering rectified DC voltages in many electronic devices as well as in industrial power supplies and frequency converters as for, for, and in. Special types are used for energy storage, for example in or applications or for frequency coupling in audio applications. Aluminum electrolytic capacitors are polarized capacitors because of their anodization principle.

They can only be operated with voltage applied with the correct polarity. Operating the capacitor with wrong polarity or with voltage leads to a and can destroy the component.

The exceptions is the bipolar aluminum electrolytic capacitor, which has a back-to-back configuration of two anodes in one case and can be used in AC applications. Basic principle of anodic oxidation, in which, by applying a voltage with a current source, an oxide layer is formed on a metallic anode Electrolytic capacitors use a chemical feature of some special metals, earlier called 'valve metals'. Applying a positive voltage to the anode material in an electrolytic bath forms an insulating oxide layer with a thickness corresponding to the applied voltage. This oxide layer acts as the dielectric in an electrolytic capacitor. Al-e-cap with polymer and non-solid electrolyte (Hybrid polymer) Description of the materials • 1: Anode foil, 2: Anode oxide layer (dielectric), 3: Cathode foil, 4: Cathode oxide layer, 5: Non-solid electrolyte, 6: Paper spacer soaked with electrolyte, either non-solid or polymer, 7: Conducting polymer, 8: Manganese oxide (MnO 2), 9: Graphite, 10: Silver The following table shows an overview over the main characteristics of the different types of aluminum electrolytic capacitors. Comparisation of the parameters of the different aluminum electrolytic capacitors types Electrolyte Capacitance range (µF) Rated voltage range (V) Typical ESR 1) 100 kHz, 20 °C (mΩ) Typical ripple current 1) 100 kHz,105 °C (mA) Leakage current 1) after 2 minutes at 10 V (µA) Non-solid borax or organic 0.1–2,700,000 4–630 800 130.

Ultra-thin-cross-section of an etched pore in a low voltage anode foil, 100,000-fold magnification, light grey: aluminum, dark grey: amorphous aluminum oxide, white: pore in which the electrolyte is active The basic material of the anode for aluminum electrolytic capacitors is a foil with a thickness of ~ 20–100 µm made of aluminum with a high purity of at least 99.99%. This is etched (roughened) in an electrochemical process to increase the effective electrode surface. By etching the surface of the anode, depending on the required rated voltage, the surface area can be increased by a factor of approximately 200 with respect to a smooth surface. After etching the aluminum anode the roughed surface is 'anodic oxidized' or 'formed'. An electrically insulating oxide layer Al 2O 3 is thereby formed on the aluminum surface by application of a current in correct polarity if it is inserted in an electrolytic bath.

This oxide layer is the capacitor dielectric. This process of oxide formation is carried out in two reaction steps whereby the for this reaction has to come from the electrolyte.

First, a strongly exothermic reaction transforms the metallic aluminum (Al) into, Al(OH) 3: 2 Al + 6 H 2O → 2 Al(OH) 3 + 3 H 2 ↑ This reaction is accelerated by a high electric field and high temperatures, and is accompanied by a pressure buildup in the capacitor housing caused by the released gas. The gel-like Al(OH) 3, also called alumina trihydrate (ATH), is converted via a second reaction step (usually slowly over a few hours at room temperature, more rapidly in a few minutes at higher temperatures) into, Al 2O 3: 2 Al(OH) 3 → 2 AlO(OH) + 2 H 2O → Al 2O 3 + 3 H 2O The aluminum oxide serves as dielectric and also protects the metallic aluminum against aggressive chemical reactions from the electrolyte. However, the converted layer of aluminum oxide is usually not homogeneous.

It forms a complex multilayer structured laminate of amorphous, crystalline and porous crystalline aluminum oxide mostly covered with small residual parts of unconverted aluminum hydroxide. For this reason, in the formation of the anode foil, the oxide film is structured by a special chemical treatment so that either an amorphous oxide or a crystalline oxide is formed. The amorphous oxide variety yields higher mechanical and physical stability and fewer defects, thus increasing the long term stability and lowering the leakage current.

The thickness of the effective dielectric is proportional to the forming voltage Amorphous oxide has a dielectric ratio of ~ 1.4 nm/V. Compared to crystalline aluminum oxide, which has a dielectric ratio of ~1.0 nm/V, the amorphous variety has a 40% lower capacitance at the same anode surface. The disadvantage of crystalline oxide is its greater sensitivity to tensile stress, which may lead to microcracks when subjected to mechanical (winding) or thermal (soldering) stressors during the post-forming processes. The various properties of oxide structures affect the subsequent characteristics of the electrolytic capacitors.

Anode foils with amorphous oxide are primarily used for electrolytic capacitors with stable long-life characteristics, for capacitors with low leakage current values, and for e-caps with rated voltages up to about 100 volts. Capacitors with higher voltages, for example photoflash capacitors, usually containing anode foils with crystalline oxide. Because the thickness of the effective dielectric is proportional to the forming voltage, the dielectric thickness can be tailored to the rated voltage of the capacitor. For example, for low voltage types a 10 V electrolytic capacitor has a dielectric thickness of only about 0.014 µm, a 100 V electrolytic capacitor of only about 0.14 µm. Thus, the dielectric strength also influences the size of the capacitor. However, due to standardized safety margins the actual forming voltage of electrolytic capacitors is higher than the rated voltage of the component.

Aluminum anode foils are manufactured as so-called 'mother rolls' of about 500 mm in width. They are pre-formed for the desired rated voltage and with the desired oxide layer structure. To produce the capacitors, the anode widths and lengths, as required for a capacitor, have to be cut from the mother roll. Anode and cathode foils are manufactured as so called 'mother rolls', from which the widths and lengths are cut off, as required for capacitor production The second aluminum foil in the electrolytic capacitor, called the 'cathode foil', serves to make electrical contact with the electrolyte. This foil has a somewhat lower degree of purity, about 99.8%. It is always provided with a very thin oxide layer, which arises from the contact of the aluminum surface with the air in a natural way. In order to reduce the contact resistance to the electrolyte and to make it difficult for oxide formation during discharging, the cathode foil is alloyed with metals such as,,.

The cathode foil is also etched to enlarge the surface. Because of the extremely thin oxide layer, which corresponds to a voltage proof of about 1.5 V, their specific capacitance is, however, much higher than that of anode foils. To justify the need for a large surface capacitance of the cathode foil see the section on charge/discharge stability below. The cathode foils, as the anode foils, are manufactured as so-called 'mother rolls', from which widths and lengths are cut off, as required, for capacitor production.

Electrolyte [ ] The electrolytic capacitor got its name from the electrolyte, the conductive liquid inside the capacitor. As a liquid it can be adapted to the porous structure of the anode and the grown oxide layer with the same shape and form as a 'tailor-made' cathode. An electrolyte always consists of a mixture of and additives to meet given requirements. The main electrical property of the electrolyte is its conductivity, which is physically an -conductivity in liquids.

In addition to the good conductivity of operating electrolytes, various other requirements are, among other things, chemical stability, high, chemical compatibility with aluminum, low, low and low costs. The electrolyte should also provide oxygen for forming and self-healing processes, and all this within a temperature range as wide as possible. This diversity of requirements for the liquid electrolyte results in a wide variety of proprietary solutions. The electrolytic systems used today can be roughly summarized into three main groups: • Electrolytes based on ethylene glycol and boric acid. In these so-called glycol or electrolyte an unwanted chemical crystal water reaction occurs according to the scheme: 'acid + alcohol' gives 'ester + water'. These borax electrolytes are standard electrolytes, long in use, and with a water content between 5 and 20%.

They work at a maximum temperature of 85 °C or 105 °C in the entire voltage range up to 600 V. Even with these capacitors, the aggressiveness of the water must be prevented by appropriate measures. • Almost anhydrous electrolytes based on organic solvents, such as (DMF), (DMA), or (GBL). These capacitors with organic solvent electrolytes are suitable for temperature ranges from 105 °C, 125 °C or 150 °C, have low leakage current values and have very good long-term capacitor behavior. • Water based electrolytes with high water content, up to 70% water for so-called 'low-impedance', 'low-ESR' or 'high-ripple-current' electrolytic capacitors with rated voltages up to 100 V for low-cost mass-market applications. The aggressiveness of the water for aluminum must be prevented with suitable additives.

Since the amount of liquid electrolyte during the operating time of the capacitors decreases over time through self-healing and by diffusion through the seal, the electrical parameters of the capacitors may be adversely affected, limiting the service life or lifetime of 'wet' electrolytic capacitors, see the section on lifetime below. Separator [ ] The anode and cathode foils must be protected from direct contact with each other because such contact, even at relatively low voltages, may lead to a short circuit.

In case of direct contact of both foils the oxide layer on the anode surface gives no protection. A spacer or separator made of a special highly absorbent paper with high purity protects the two metal foils from direct contact.

This capacitor paper also serves as a reservoir for the electrolyte to extend the lifetime of the capacitor. The thickness of the spacer depends on the rated voltage of the electrolytic capacitor. It is up to 100 V between 30 and 75 µm. For higher voltages, several layers of paper (duplex paper) are used to increase the breakdown strength. Encapsulation [ ]. View of three different imprinted predetermined breaking points (pressure relief vents) on the bottom of cases of radial electrolytic capacitors The encapsulation of aluminum electrolytic capacitors is also made of aluminum in order to avoid reactions, normally with an aluminum case (can, tub). For radial electrolytic capacitors it is connected across the electrolyte with a non-defined resistance to the cathode (ground).

For axial electrolytic capacitors, however, the housing is specifically designed with a direct contact to the cathode. In case of a malfunction, overload or wrong polarity operating inside the electrolytic capacitor housing, substantial gas pressure can arise. The tubs are designed to open a pressure relief vent and release high pressure gas, including parts of the electrolyte. This vent protects against bursting, explosion or fly away of the metal tub. For smaller housings the pressure relief vent is carved in the bottom or the notch of the tub.

Larger capacitors like screw-terminal capacitors have a lockable overpressure vent and must be mounted in an upright position. Sealing [ ] The sealing materials of aluminum electrolytic capacitors depend on the different styles. For larger screw-terminal and snap-in capacitors the sealing washer is made of a plastic material. Axial electrolytic capacitors usually have a sealing washer made of phenolic resin laminated with a layer of rubber. Radial electrolytic capacitors use a rubber plug with a very dense structure. All sealing materials must be inert to the chemical parts of the electrolyte and may not contain soluble compounds that could lead to contamination of the electrolyte. To avoid leakage, the electrolyte must not be aggressive to the sealing material.

Production [ ]. Process flow diagram for production of radial aluminum electrolytic capacitors with non-solid electrolyte The production process start with mother rolls. First, the etched, roughened and pre-formed anode foil on the mother roll as well as the spacer paper and the cathode foil are cut to the required width. The foils are fed to an automatic winder, which makes a wound section in a consecutive operation involving three sequential steps: terminal welding, winding, and length cutting.

In the next production step the wound section fixed at the lead out terminals is soaked with electrolyte under vacuum impregnation. The impregnated winding is then built into an aluminum case, provided with a rubber sealing disc, and mechanically tightly sealed by curling. Thereafter, the capacitor is provided with an insulating shrink sleeve film. This optically ready capacitor is then contacted at rated voltage in a high temperature post-forming device for healing all the dielectric defects resulting from the cutting and winding procedure. Georgia Pacific Fast Beam Software Logo. After post-forming, a 100% final measurement of capacitance, leakage current, and impedance takes place. Taping closes the manufacturing process; the capacitors are ready for delivery.

Styles [ ] • Different styles of non-solid aluminum electrolytic capacitors •. Some various forms of historical anode structures. For all of these anodes the outer metallic container serves as the cathode The first common application of wet aluminum electrolytic capacitors was in large telephone exchanges, to reduce relay hash (noise) on the 48 volt DC power supply.

The development of AC-operated domestic radio receivers in the late 1920s created a demand for large-capacitance (for the time) and high-voltage capacitors for the technique, typically at least 4 microfarads and rated at around 500 volts DC. Waxed paper and oiled silk were available, but devices with that order of capacitance and voltage rating were bulky and prohibitively expensive. A 'dry' electrolytic capacitor with 100 µF and 150 V The ancestor of the modern electrolytic capacitor was patented by in 1925, who teamed with, the founder of the battery company that is now known as. Ruben's idea adopted the stacked construction of a. He introduced a separate second foil to contact the electrolyte adjacent the anode foil instead of using the electrolyte-filled container as the cathode of the capacitor.

The stacked second foil got its own terminal additional to the anode terminal and the container had no longer an electrical function. This type of electrolytic capacitor with one anode foil separated from a cathode foil by a liquid or gel-like electrolyte of a non-aqueous nature, which is therefore dry in the sense of having a very low water content, became known as the 'dry' type of electrolytic capacitor. This invention, together with the invention of wound foils separated with a paper spacer 1927 by A. Eckel, Hydra-Werke (Germany), reduced the size and the price significantly, which helped make the new radios affordable for a broader group of customers., whose first patent for electrolytic capacitors was filed in 1928, industrialized the new ideas for electrolytic capacitors and started large-scale commercial production in 1931 in the Cornell-Dubilier (CD) factory in Plainfield, New Jersey. At the same time in Berlin, Germany, the 'Hydra-Werke', an company, started the production of electrolytic capacitors in large quantities. Already in his patent application of 1886 Pollak wrote that the capacitance of the capacitor increased if the surface of the anode foil was roughened.

A number of methods have since been developed for roughening the anode surface, mechanical methods like sand blasting or scratching, and chemical etching with acids and acid salts forced by high currents. Some of these methods were developed in the CD factory between 1931 and 1938. Today (2014), electro-chemically etching of low voltage foils can achieve up to a 200 fold increase in surface area compared to a smooth surface. Progress relating to the etching process is the reason for the ongoing reduction in the dimensions of aluminum electrolytic capacitors over the past decades. Miniaturization of aluminum electrolytic capacitors from 1960 to 2005 in case 10x16mm up to factor ten The period after World War II is associated with a rapid development in radio and television technology as well as in industrial applications, which had great influence on production quantities but also on styles, sizes and series diversification of electrolytic capacitors.

New electrolytes based on organic liquids reduced leakage currents and ESR, broadened temperature ranges and increased lifetimes. Corrosion phenomena caused by chlorine and water could be avoided by a higher purity manufacturing processes and by using additives in the electrolytes. The development of in the early 1950s with as solid electrolyte, which has a 10 times better conductivity than all other types of non-solid electrolytes, also influenced the development of aluminum electrolytic capacitors.

In 1964 the first aluminum electrolytic capacitors with solid electrolyte () appeared on the market, developed. The decades from 1970 to 1990 were marked by the development of various new professional aluminum electrolytic capacitor series with f. e. Very low leakage currents or with long life characteristics or for higher temperatures up to 125 °C, which were specifically suited to certain industrial applications.

The great diversity of the many series of aluminum electrolytic capacitors with non-solid electrolytes up to now (2014) is an indicator of the adaptability of the capacitors to meet different industrial requirements. Conductivity of non-solid and solid electrolytes In 1983 a further reduction of the ESR was achieved by with its ' aluminum electrolytic capacitors. These capacitors use as solid organic conductor the charge transfer salt TTF-TCNQ (), which provided an improvement in conductivity by a factor of 10 with respect to the manganese dioxide electrolyte.

The ESR values of TCNQ-capacitors were significantly reduced by the discovery of by, and. The conductivity of conductive polymers such as or are better than that of TCNQ by a factor of 100 to 500, and are close to the conductivity of metals. In 1991 Panasonic put its 'SP-Cap', a polymer aluminum electrolytic capacitor, on the market. These electrolytic capacitors with polymer electrolytes achieved ESR values low enough to compete with (MLCCs). They were still less expensive than tantalum capacitors and were a short time later used in devices with a flat design, such as and. New water-based electrolytes were developed in Japan from the mid-1980s with the goal of reducing ESR for inexpensive non-solid electrolytic capacitors. Water is inexpensive, an effective solvent for electrolytes, and significantly improves the conductivity of the electrolyte.

The Japanese manufacturer was a leader in the development of new water-based electrolyte systems with enhanced conductivity in the late 1990s. The new series of non-solid capacitors with water-based electrolyte was called in the data sheets 'Low-ESR', 'Low-Impedance', 'Ultra-Low-Impedance' or 'High-Ripple Current' series. A stolen recipe of such a water-based electrolyte, in which important stabilizing substances were absent, led in the years 2000 to 2005 to the problem of mass-bursting capacitors in computers and power supplies, which became known under the term '. In these capacitors the water reacts quite aggressively and even violently with aluminum, accompanied by strong heat and gas development in the capacitor, and often leads to the explosion of the capacitor. Electrical parameters [ ]. Series-equivalent circuit model of an electrolytic capacitor The electrical characteristics of capacitors are harmonized by the international generic specification IEC 60384-1. In this standard, the electrical characteristics of capacitors are described by an idealized series-equivalent circuit with electrical components that model all ohmic losses, capacitive and inductive parameters of an electrolytic capacitor: • C, the capacitance of the capacitor, • R ESR, the, which summarizes all ohmic losses of the capacitor, usually abbreviated as 'ESR'.

• L ESL, the, which is the effective self-inductance of the capacitor, usually abbreviated as 'ESL'. • R leakage, the that represents the leakage current Capacitance standard values and tolerances [ ].

Typical capacitance as a function of temperature The basic unit of electrolytic capacitors capacitance is the (μF, or less correctly uF). The capacitance value specified in manufacturers' data sheets is called the rated capacitance C R or nominal capacitance C N and is the value for which the capacitor has been designed. Standardized measuring conditions for electrolytic capacitors are an measurement with 0.5 V at a frequency of 100/120 Hz and a temperature of 20 °C. The capacitance value of an electrolytic capacitor depends on the measuring frequency and temperature. The value at a measuring frequency of 1 kHz is about 10% less than the 100/120 Hz value.

Therefore, the capacitance values of electrolytic capacitors are not directly comparable and differ from those of or, whose capacitance is measured at 1 kHz or higher. Measured with an AC measuring method with 100/120 Hz the measured capacitance value is the closest value to the electrical charge stored in the capacitor. The stored charge is measured with a special discharge method and is called capacitance. The DC capacitance is about 10% higher than the 100/120 Hz AC capacitance.

Shola Ama In Return Rar Download there. The DC capacitance is of interest for discharge applications like. The percentage of allowed deviation of the measured capacitance from the rated value is called capacitance tolerance. Electrolytic capacitors are available in different tolerance series, whose values are specified in the specified in IEC 60063. For abbreviated marking in tight spaces, a letter code for each tolerance is specified in IEC 60062. • rated capacitance,, tolerance ±20%, letter code 'M' • rated capacitance,, tolerance ±20%, letter code 'M' • rated capacitance,, tolerance ±10%, letter code 'K' The required capacitance tolerance is determined by the particular application. Electrolytic capacitors that are often used for and capacitors do not need narrow tolerances because they are not used for accurate frequency applications, such as for. Rated and category voltage [ ].

Relation between rated and category voltage and rated and category temperature In IEC 60384-1 the allowed operating voltage is called the 'rated voltage' U R or the 'nominal voltage' U N. The rated voltage 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 electrolytic capacitors, which is directly proportional to the dielectric layer thickness, decreases with increasing temperature. For some applications it is important to use a high temperature range. Lowering the voltage applied at a higher temperature maintains safety margins. For some capacitor types, therefore, the IEC standard specifies a second 'temperature derated voltage' for a higher temperature range, the 'category voltage' U C. The category voltage is the maximum DC voltage, peak pulse voltage or superimposed AC voltage that may be applied continuously to a capacitor at any temperature within the category temperature range.

Surge voltage [ ] Aluminum electrolytic capacitors can be applied for a short time with an overvoltage, also called a surge voltage. The surge voltage indicates the maximum voltage value within the temperature range that may be applied during the lifetime at a frequency of 1000 cycles (with a dwell time of 30 seconds and a pause of 5 minutes and 30 seconds in each instance) without causing any visible damage to the capacitor or a capacitance change of more than 15%. For capacitors with a rated voltage of ≤ 315 volts the surge voltage is 1.15 times the rated voltage, and for capacitors with a rated voltage exceeding 315 volts the surge voltage is 1.10 times the rated voltage. Transient voltage [ ] Aluminum electrolytic capacitors with non-solid electrolyte are relatively insensitive to high and short-term transient voltages higher than the surge voltage, if the frequency and the energy content of the transients is low. This ability depends on the rated voltage and component size. Low energy transient voltages lead to a voltage limitation similar to a. The electrochemical oxide forming processes take place when voltage in correct polarity is applied and generates an additional oxide when transients arise.

This formation is accompanied with heat and hydrogen gas generation. This is tolerable if the energy content of the transient is low. However, when a transient peak voltage causes an electric field strength that is too high for the dielectric, it can directly cause a short circuit. An unambiguous and general specification of tolerable transients or peak voltages is not possible. In every case transients arise, the application has to be carefully approved. Electrolytic capacitors with solid electrolyte cannot withstand transients or peak voltages higher than the surge voltage. Transients for this type of electrolytic capacitor may destroy the component.

Reverse voltage [ ]. An exploded electrolytic capacitor on a PCB Electrolytic capacitors are polarized capacitors and generally require an anode electrode voltage to be positive relative to the cathode voltage. However, the cathode foil of aluminum electrolytic capacitors is provided with a very thin, natural air-originated oxide layer. This oxide layer has a voltage proof of approximately 1 to 1.5 V. Therefore, aluminum electrolytic capacitors with non-solid electrolyte can withstand a very small reverse voltage and, for example, can be measured with an AC voltage of about 0.5 V, as specified in relevant standards. At a reverse voltage lower than −1.5 V at room temperature, the cathode aluminum foil begins to build up an oxide layer corresponding to the applied voltage.

This is aligned with generating hydrogen gas with increasing pressure. At the same time the oxide layer on the anode foil begins dissolution of the oxide, which weakens the voltage proof. It is now a question of the outside circuit whether the increasing gas pressure from oxidization leads to bursting of the case, or the weakened anode oxide leads to a breakdown with a. If the outside circuit is high-ohmic the capacitor fails and the vent opens due to high gas pressure.

If the outside circuit is low-ohmic, an internal short circuit is more probable. In every case a reverse voltage lower than −1.5 V at room temperature may cause the component to catastrophically fail due to a dielectric breakdown or overpressure, which causes the capacitor to burst, often in a spectacularly dramatic fashion. Modern electrolytic capacitors have a safety vent that is typically either a scored section of the case or a specially designed end seal to vent the hot gas/liquid, but ruptures can still be dramatic.

To minimize the likelihood of a polarized electrolytic being incorrectly inserted into a circuit, polarity has to be very clearly indicated on the case, see the section headed 'Polarity marking'. Special bipolar capacitors designed for AC operation, usually referred to as 'bipolar', 'non-polarized' or 'NP' types, are available. In these, the capacitors have two anode foils of opposite polarity connected in series. On each of the alternate halves of the AC cycle, one anode acts as a blocking dielectric, preventing reverse voltage from damaging the opposite anode. But these bipolar electrolytic capacitors are not adaptable for main AC applications instead of power capacitors with metallized polymer film or paper dielectric. Impedance [ ].

During discharging the current flow direction in the capacitor changes, the cathode (-) gets an anode (+), two internal voltages with opposite polarity arise. The capacitor construction rule - C K >>C A - ensures no post-forming of the cathode foil during discharging.

Aluminum electrolytic capacitors with non-solid electrolytes always contain, in addition to the anode foil, a cathode foil that serves as electrical contact to the electrolyte. This cathode foil is provided with a very thin, natural, air-originated oxide layer, which act also as a dielectric.

Thus, the capacitor construction forms a series circuit of two capacitors, the capacitance of the anode foil C A and the cathode foil C K. As described above, the capacitance of the capacitor C e-cap is mainly determined by the anode capacitance C A when the cathode capacitance C K is approximately 10 times higher than the anode capacitance C A. Aluminum electrolytic capacitors with non-solid electrolytes normally can be charged up to the rated voltage without any current limitation.

This property is a result of the limited ion movability in the liquid electrolyte, which slows down the voltage ramp across the dielectric, and the capacitor's ESR. During discharging the internal construction of the capacitor reverses the internal polarity.

The cathode (-) gets an anode (+), and changes the current flow direction. Two voltages arise over these electrode. In principle the voltage distribution over both electrodes behaves as the reciprocally CV product of each electrode. The design rule of high cathode capacitance assures that the voltage appearing over the cathode during discharge is not higher than roughly 1.5 V, that is its natural air-originated voltage proof. No further post-forming of the cathode foil takes place, which may lead to capacitance degradation. Then the capacitors are discharge-proof.

Current surge, peak or pulse current [ ] Small (diameter. Main article: Dielectric absorption occurs when a capacitor that has remained charged for a long time discharges only incompletely when briefly discharged.

Although an ideal capacitor would reach zero volts after discharge, real capacitors develop a small voltage from time-delayed dipole discharging, a phenomenon that is also called, 'soakage' or 'battery action'. Values of dielectric absorption for some often used capacitors Type of capacitor Dielectric absorption Tantalum electrolytic capacitors with solid electrolyte 2 to 3%, 10% Aluminium electrolytic capacitor with non solid electrolyte 10 to 15% Dielectric absorption may be a problem in circuits using very small currents in electronic circuits, such as long- or circuits.

Dielectric absorption is not a problemIn in most applications of electrolytic capacitors supporting power supply lines. But especially for electrolytic capacitors with high rated voltage the voltage at the terminals generated by the dielectric absorption can be a safety risk to personnel or circuits. In order to prevent shocks most very large capacitors are shipped with shorting wires that need to be removed before use. Reliability, lifetime and failure modes [ ] Reliability (failure rate) [ ]. With times of 'early failures', 'random failures', and 'wear-out failures'. The time of random failures is the time of constant failure rate and corresponds with the lifetime of non-solid electrolytic capacitors.

The prediction of aluminum electrolytic capacitors is generally expressed as a λ, abbreviated FIT (Failures In Time). It is a measure of the number of failures per unit hour during the time of constant random failures in the. The flat part in the bathtub curve corresponds with the calculated lifetime or of non-solid electrolytic capacitors. The failure rate is used to calculate a survival probability for a desired lifetime of an electronic circuit in combination with other participating components. 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 components for 1 million hours, or 1 million components for 1000 hours (1 /1000 hours) each during the period of constant random failures. This failure rate model implicitly assumes the idea of 'random failure'. Individual components fail at random times but at a predictable rate.

Failures are short circuits, open circuits and degradation failures (exceeding specified limits of electrical parameters). The reciprocal value of FIT is the MTBF, the. The standard operating conditions for the failure rate FIT are 40 °C and 0.5 U R. For other conditions of applied voltage, current load, temperature, capacitance value, circuit resistance (for tantalum capacitors), mechanical influences and humidity the FIT figure can recalculated with acceleration factors standardized for industrial or military contexts. The higher the temperature and the applied voltage, the higher the failure rate. It is good to know that for capacitors with solid electrolytes the failure rate is often expressed as per cent failed components per thousand hours (n%/1000 h), and specified at reference conditions 85 °C and rated voltage U R. That is, 'n' number of failed components per 10 5 hours, or in FIT the ten-thousand-fold value per 10 9 hours but for different reference conditions.

For these other conditions the '%I1000 h' figure can be recalculated with acceleration factors standardized for industrial or military contexts. Most modern aluminum electrolytic capacitors with non-solid electrolytes nowadays are very reliable components with very low failure rates, with predicted life expectancies of decades under normal conditions.

It is best practice to have electrolytic capacitors pass a post-forming process step after production, similar to a ', so that early failures are eliminated during production. The FIT values given in data sheets are calculated from the long-time experience of the manufacturer, based on the lifetime test results. Typical reference failure rate values for aluminum electrolytic capacitors with non-solid electrolytes are for low voltages types (6.3–160 V) FIT rates in the range of 1 to 20 FIT and for high voltage types (>160–550 V) FIT rates in the range of 20 to 200 FIT.

Field failure rates for aluminum capacitors are in the range of 0.5 to 20 FIT. The data for the 'failure rate' specification are based on the results of lifetime testing (endurance testing).

In addition a 'field failure rate' is sometimes specified. This figures comes from big customers that noticed failures in the field out of their application.

Field failure rates could have much lower values. For aluminum electrolytic capacitors they are in the range of 0.5 to 20 FIT. The field failure rate values are in line with the usual orders of magnitude for electronic components. Lifetime, service life [ ]. Failed aluminum electrolytic capacitors with open vent caused by using a wrong electrolyte Aluminum electrolytic capacitors with non-solid electrolytes have, in terms of quality, a relatively negative public image. This is contrary to industrial experience, where electrolytic capacitors are considered to be reliable components if used within their specified specifications during the calculated lifetime. The negative public image might be, among other reasons, because failed electrolytic capacitors in devices are easily and immediately visible.

This is exceptional and not the case with other electronic components. As with any industrial product, specific causes of failure modes are known for aluminum electrolytic capacitors with non-solid electrolytes. They can be differentiated in failures causes by capacitor development and production, by device production, by capacitor application or by external influences during use. The capacitor manufacturing industries can only influence the first failure mode. Most manufacturers have had well-structured quality control departments for decades, supervising all development and manufacturing steps.

Failure mode flow charts demonstrate this. However, a typical physically or chemically caused major failure mode during application, like 'field crystallization' for tantalum capacitors, is not known for non-solid aluminum electrolytic capacitors. Capacitor behavior after storage or disuse [ ] In many quarters, electrolytic capacitors are considered very unreliable components when compared to other passives. This is partly a function of the history of these components. Capacitors manufactured during and before sometimes suffered from contamination during manual manufacturing, and in particular chlorine salts were often the reason for corrosive processes leading to high leakage currents.

Chlorine acts on aluminum as a catalyst for the formation of unstable oxide without becoming chemically bound itself. After World War II this problem was known but the measuring equipment was not accurate enough to detect chlorine in very low ppm concentration. The situation improved over the next 20 years and the capacitors became good enough for longer life applications. This lead in turn to a previously unnoticed water driven corrosion, which weakens the stable dielectric oxide layer during storage or disuse.

This leads to high leakage currents after storage. Most of the electrolytes in that time contain water, and many of the capacitors reach their end of life by drying out. Water driven corrosion was the reason for recommended precondition instructions. The first solution in the 1970s was the development of water-free electrolyte systems based on organic solvents. Their advantages, among other things were lower leakage currents and nearly unlimited shelf life. But now another problem was observed.

The growing mass production with automatic insertion machines requires a washing of the 's after soldering. The cleaning solutions contain chloroalkanes () agents. These halogens solutions sometimes permeate the sealing of the capacitors and start chlorine corrosion. Again there was a leakage current problem.

The use of CFCs as solvents for dry cleaning have been phased out, for example, by the directive on in 1994 and by the (VOC) directive of the in 1997. In the meantime electrolytic systems have been developed with additives to inhibit the reaction between anodic aluminum oxide and water, which solve most of the high leakage current problems after storage. The ability of non-solid aluminum electrolytic capacitors to have a stable behavior during longer storage times can be tested by using an accelerating test of storage the capacitors at its upper category temperature for a certain period, usually 1000 hours without voltage applied.

This 'shelf life test' is a good indicator for an inert chemically behavior of the electrolytic system against the dielectric aluminum oxide layer because all chemical reactions are accelerated by high temperatures. Nearly all today's series of capacitors fulfill the 1000 hours shelf life test, which is equivalent to a minimum five years of storage at room temperature. Modern electrolytic capacitors don't need preconditioning after such storage. However, many capacitor series are specified only for two years storage time, but the limit is set by oxidation of terminals and resulting solderability problems.

For restoring antique radio equipment using older electrolytic capacitors built in the 1970s or earlier, 'pre-conditioning' is often recommended. For this purpose, the rated voltage is applied to the capacitor via a series resistance of approximately 1 kΩ for a period of one hour.

Applying a voltage via a safety resistor repairs the oxide layer by self-healing, but slowly, minimizing internal heating. If capacitors still don't meet the leakage current requirements after preconditioning, it may be an indication of permanent damage. Additional information [ ] Capacitor symbols [ ]. Capacitor symbols Parallel connection [ ] Smaller or low voltage aluminum electrolytic capacitors may be connected in parallel without any safety correction action. Large sizes capacitors, especially large sizes and high voltage types, should be individually guarded against sudden energy charge of the whole capacitor bank due to a failed specimen.

Series connection [ ] Some applications like with DC-link for frequency controls in need higher voltages than electrolytic capacitors usually offer. For such applications electrolytic capacitors can be connected in series for increased voltage-withstanding capability. During charging, the voltage across each of the capacitors connected in series is proportional to the inverse of the individual capacitor's leakage current. Since every capacitor differs somewhat in individual leakage current, the capacitors with a higher leakage current will get less voltage.

The voltage balance over the series-connected capacitors is not symmetrical. Passive or active voltage balance has to be provided in order to stabilize the voltage over each individual capacitor. Imprinted markings [ ] Electrolytic capacitors, like most other electronic components, have imprinted markings to indicate the manufacturer, the type, the electrical and thermal characteristics, and the date of manufacture. In the ideal case, if they are large enough the capacitor should be marked with: • Manufacturer's name or trademark; • Manufacturer's type designation; • Polarity of the terminations (for polarized capacitors) • Rated capacitance; • Tolerance on rated capacitance • Rated voltage and nature of supply (AC or DC) • Climatic category or rated temperature; • Year and month (or week) of manufacture; Smaller capacitors use a shorthand notation to display all the relevant information in the limited space available.

The most commonly used format is: XYZ K/M VOLTS V, where XYZ represents the capacitance in µF, the letters K or M indicate the tolerance (±10% and ±20% respectively), and VOLTS V represents the rated voltage. Example: • A capacitor with the following text on its body: 10M 25 has a capacitance of 10 µF, tolerance K = ±10% with a rated voltage of 25 V. Capacitance, tolerance, and date of manufacture can also be identified with a short code according to IEC 60062. Examples of short-marking of the rated capacitance (microfarads): • µ47 = 0.47 µF, 4µ7 = 4.7 µF, 47µ = 47 µF The date of manufacture is often printed in accordance with international standards in abbreviated form. • Version 1: coding with year/week numeral code, '1208' is '2012, week number 8'. • Version 2: coding with year code/month code, Year code: 'R' = 2003, 'S'= 2004, 'T' = 2005, 'U' = 2006, 'V' = 2007, 'W' = 2008, 'X' = 2009, 'A' = 2010, 'B' = 2011, 'C' = 2012, 'D' = 2013, 'E' = 2014, 'F' = 2015 etc. Month code: '1' to '9' = Jan.

To Sept., 'O' = October, 'N' = November, 'D' = December 'C5' is then '2012, May' Polarity marking [ ] • Polarity marking for non-solid and solid aluminum electrolytic capacitors •. Polarity marking on a SMD-V-chip capacitor style electrolytic capacitors with non-solid electrolyte (vertical-chips, V-chips) have a colored filled half circle or a minus bar on the top case side visible to indicate the minus terminal side. Additionally, the insulating plate under the capacitor body uses two skewed edges to indicate that the negative terminal is on the complement position. Radial or single-ended electrolytic capacitor styles have a bar across the side of the capacitor to indicate the negative terminal side, and the negative terminal lead is shorter than the positive terminal lead. Axial electrolytic capacitor styles have a bar across or around the case pointing to the negative lead end to indicate the negative terminal. The positive terminal of the capacitor is on the side of the sealing.

The negative terminal lead is shorter than the positive terminal lead. On a it is customary to indicate the correct orientation by using a square through-hole pad for the positive lead and a round pad for the negative one. Standardization [ ] The standardization for all, components and related technologies follows the rules given by the (IEC), a, non-governmental international.

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