The electrolytic capacitor is a kind of capacitor. The metal foil is a positive electrode (aluminum or tantalum), the oxide film (aluminum oxide or tantalum pentoxide) which is in close contact with the positive electrode is a dielectric, and the cathode is made of a conductive material or an electrolyte (the electrolyte may be a liquid or Solid) is composed of other materials. Since the electrolyte is the main part of the cathode, the electrolytic capacitor is named after it. At the same time, the electrolytic capacitors are not connected correctly. Aluminum electrolytic capacitors can be divided into four categories: lead-type aluminum electrolytic capacitors; horn-type aluminum electrolytic capacitors; bolt-type aluminum electrolytic capacitors; solid aluminum electrolytic capacitors.
1, characteristics
Characteristics of electrolytic capacitors: The capacitance per unit volume is very large, tens to hundreds of times larger than other types of capacitors.
Electrolytic capacitors feature two: the rated capacity can be very large, can easily achieve tens of thousands of μf or even a few f (but not with the double layer capacitance).
Electrolytic capacitors have three characteristics: the price is overwhelmingly superior to other types, because the constituent materials of electrolytic capacitors are common industrial materials, such as aluminum. The equipment for manufacturing electrolytic capacitors is also an ordinary industrial equipment, which can be mass-produced and has relatively low cost. Common Japanese electrolytic capacitors are NipponChemi-con (Black King Kong), Nichicon (Nijikang), Rubycon (Ruby), Matsushita (Panasonic, changed from 2005 to Panasonic), Hitachi (Hitachi), ELNA (Elna, commonly known as As a representative, the Taiwanese capacitors are represented by LELON, SUSCON, TEAPO, CAPXON, Hong Kong: SAMXON, and domestic TH ( Huayu), capsun (green barium capacitor), Beryl (emerald), Acon (central), Chang (Warway), Xunda (Xunda), etc., Europe and the United States to ELEBASIC, ITEDCON, KENDEIL, CDE, BHC, EVERALPHA to represent.
2, the principle
Electrolytic capacitors are usually made of metal foil (aluminum/bismuth) as a positive electrode, an insulating oxide layer of aluminum foil (aluminum oxide/yttrium oxide) as a dielectric, and electrolytic capacitors are divided into aluminum electrolytic capacitors and tantalum electrolysis by their positive electrodes. Capacitor. The negative electrode of the aluminum electrolytic capacitor is composed of a thin paper/film or an electrolyte polymer immersed in an electrolyte liquid (liquid electrolyte); the negative electrode of the tantalum electrolytic capacitor is usually manganese dioxide. Since the electrolyte is used as the negative electrode (note that it is distinguished from the dielectric), the electrolytic capacitor is named after it.
3, application
Polar electrolytic capacitors usually function as power supply filtering, decoupling, signal coupling, time constant setting, and DC blocking in power supply circuits or intermediate frequency and low frequency circuits. Generally, it can not be used in the AC power supply circuit. When used as a filter capacitor in the DC power supply circuit, the anode (positive electrode) should be connected to the positive terminal of the power supply voltage, and the cathode (negative electrode) should be connected to the negative terminal of the power supply voltage. Otherwise it will damage the capacitor.
Non-polar electrolytic capacitors are commonly used in speaker divider circuits, television S correction circuits, and start-up circuits for single-phase motors.
Electrolytic capacitors are widely used in household appliances and various electronic products. Their capacities range from 1 to 1000 μF and rated operating voltages range from 6.3 to 450V. The disadvantage is that the dielectric loss and the capacity error are large (the maximum allowable deviation is +100%, -20%), the high temperature resistance is poor, and the storage time is long and easy to be invalid.
The polarity of the electrolytic capacitor, pay attention to observe that there is a "-" on the side of the electrolytic capacitor, which is the negative pole. If the positive and negative electrodes are not indicated on the electrolytic capacitor, it can also be judged according to the length of its lead. The long leg is the positive pole and the short leg. It is the negative electrode.
4. Development
In terms of current production, aluminum electrolytic capacitors occupy the second place in capacitors. These capacitors were originally general DC capacitors, but now they have evolved from DC to AC, from low temperature to high temperature, from low voltage to high voltage, from general to special, from general structure to chip, flat, books. Structure and so on. Its upper limit capacity has been extended to about 4F, the frequency of use has reached 30kHz, the operating temperature range has reached -55 °C -125 °C, and some even up to 150 °C, the rated voltage has reached 700V. In short, the development of aluminum electrolytic capacitors is becoming more widespread. The basis for these developments is as follows:
1. In terms of materials, the aluminum foil used now is very elegant in composition and structure. High purity is no longer required, for example, for anode foils, which are required to be of high purity. In order to improve the initial corrosion point, mechanical strength and properties of the dielectric oxide film, the foil should contain some impurities. And some use alloy foil. In terms of structure, for the low-pressure foil, the proportion of the cubic structure is not required to be large, but for the high-pressure foil, the structure is required to account for 80% to 90% or more. In order to increase the specific volume of the cathode foil, an alloy aluminum foil having a certain amount of impurities having a regular orientation of crystal grains is required. The working electrolyte consists of three components. That is, solvents, solutes, and additives, such as electrolytes that have been used for a long period of time, are composed of ethylene glycol, glycerin, boric acid, and aqueous ammonia. Due to the development of aluminum electrolytic capacitors, this electrolyte is far from satisfactory, so many new electrolytes have been produced to reduce the operating temperature range of the capacitor (eg -55 ° C - l25 ° C). The formulation principle of these new electrolytes is: 1 mixed with two solvents. To achieve complementarity. 2 Two weak acids are used to provide the two anionic groups required. 3 add alkali, such as organic amine, to adjust the pH of the electrolyte and flash voltage. Change its resistivity. 4 Additives which improve the characteristics of the electrolyte, such as phosphoric acid or a salt thereof for preventing hydration of the aluminum oxide film, dinitrobenzene which absorbs hydrogen, and the like, and an ethylene oxide which increases the flashover voltage of the electrolyte.
2. In terms of process, in addition to the mechanization and automation of production, the progress of aluminum electrolytic capacitors in the process is mainly the two processes of corrosive phase forming. The corrosion coefficient of aluminum foil is not only high (low-voltage capacitor foil has reached 100, high voltage is up to 25), and aluminum foil with different pothole morphology can be etched according to the performance requirements of the capacitor. The etching process is a kind of corrosive liquid type, concentration, temperature, original foil composition, structure, surface state, foil speed during corrosion, and dynamic balance process of power source type, waveform, frequency, voltage, etc. The question is how to get the best dynamic balance and how to determine the most balanced balance according to the requirements. Therefore, it cannot be said that the current corrosion process has reached the optimum state.
Nowadays, the energization process can produce high-quality dielectric oxide film, and different dielectric oxide films can be manufactured according to different requirements. For example, for DC capacitors, γ and γ'-type crystalline aluminum oxide films are fabricated, and the exchange is performed. The capacitor is an amorphous film. The greatest advancement in the energization process is the ability to convert an aluminum hydroxide film into a dielectric aluminum oxide film and form a water repellent layer on its surface. In addition, defects and cracks in the dielectric film can be eliminated.
3. In terms of structure, the structure of aluminum electrolytic capacitors has been diversified, except for the above liquid aluminum electrolytic capacitors. There are also solid aluminum electrolytic capacitors. There are two main structural forms, one is a foil-wound shape, and the other is an aluminum powder sintered porous block, and the solid electrolyte used is mainly MnO2. The structure of aluminum electrolytic capacitors has been diversified, such as double anode structure, cathode structure, book type structure, triangular structure, and chip structure. Among them, the appearance of chip aluminum electrolytic capacitors is another progress of aluminum electrolytic capacitors. Because there is no high specific volume aluminum foil, high temperature resistant electrolyte, excellent sealing structure and fine processing technology, it is difficult to produce a suitable chip aluminum electrolytic capacitor. The purpose is to compare the chip rate. Low level.
5, the future
Huayu Electronics' TH brand 700V electrolytic capacitor and ultra-large high-voltage large-capacity 100*270mm have been developed. The material used by Capsun and TDK for the YDK-700V capacitor is 820V, which has been applied to the Japanese capsun group. It is extremely epoch-making, which means that the 537V after 380V rectification will no longer need to connect two 400Vs. The performance of aluminum electrolytic capacitors in the future will further develop with the advancement of technology. The normal capacitance of the 700V100uf is usually 35*80-100MM or 50*80-96MM at around $22. Currently used in the world's top capsun, YAMAHA audio is widely exported to high-end hotels in Europe and America. The price of 1200 US dollars to millions of dollars is expensive, and it is mostly used in noble families and hotels. Small-capacity and large-capacity supercapacitors are also being developed.
The test method and test conditions for the leakage current of aluminum electrolytic capacitors are as follows: at 25 ° C, the capacitor to be tested is connected in series with a 1000 Ω protection resistor to the rated voltage to measure the leakage current. After applying the voltage for 5 min, the leakage current does not exceed the maximum value of the specification as qualified. Small-capacity aluminum electrolytic capacitors can use 1min test results. Large-capacity aluminum electrolytic capacitors will require longer test time. As can be seen from the characteristic curve, the current will infinitely approach the final "leakage current" value - supplemental oxidation The current value required for the aluminum medium. The dissipation factor (DF) of an electrolytic capacitor can be understood as the reactive power of the electrolytic capacitor and the active power of the equivalent series resistance (ESR) under the excitation of the alternating current. Obviously, this is the ratio of capacitive reactance to equivalent series resistance (ESR). The RC circuit in the AC circuit, and this ratio is very similar to the opposite side of the trigonometric function - the tangent function. Therefore, the loss factor of the electrolytic capacitor (referred to as DF) is also referred to as loss tangent in many technical documents. The voltage indexes of aluminum electrolytic capacitors mainly include rated DC voltage, rated surge voltage, instantaneous overvoltage and reverse voltage.
Rated DC Voltage VR The rated DC voltage VR is the continuous operating voltage allowed for the capacitor within the rated temperature range. It includes the sum of the DC voltage and the ripple voltage or continuous pulse voltage between the two electrodes of the capacitor. Typically, the rated voltage of the tantalum capacitor is indicated on the surface of the capacitor. Usually rated voltage ≤ 100VT491B107M004AT is a "low voltage" tantalum capacitor, and rated voltage ≥ 150V is a "high voltage" capacitor
1, characteristics
Characteristics of electrolytic capacitors: The capacitance per unit volume is very large, tens to hundreds of times larger than other types of capacitors.
Electrolytic capacitors feature two: the rated capacity can be very large, can easily achieve tens of thousands of μf or even a few f (but not with the double layer capacitance).
Electrolytic capacitors have three characteristics: the price is overwhelmingly superior to other types, because the constituent materials of electrolytic capacitors are common industrial materials, such as aluminum. The equipment for manufacturing electrolytic capacitors is also an ordinary industrial equipment, which can be mass-produced and has relatively low cost. Common Japanese electrolytic capacitors are NipponChemi-con (Black King Kong), Nichicon (Nijikang), Rubycon (Ruby), Matsushita (Panasonic, changed from 2005 to Panasonic), Hitachi (Hitachi), ELNA (Elna, commonly known as As a representative, the Taiwanese capacitors are represented by LELON, SUSCON, TEAPO, CAPXON, Hong Kong: SAMXON, and domestic TH ( Huayu), capsun (green barium capacitor), Beryl (emerald), Acon (central), Chang (Warway), Xunda (Xunda), etc., Europe and the United States to ELEBASIC, ITEDCON, KENDEIL, CDE, BHC, EVERALPHA to represent.
2, the principle
Electrolytic capacitors are usually made of metal foil (aluminum/bismuth) as a positive electrode, an insulating oxide layer of aluminum foil (aluminum oxide/yttrium oxide) as a dielectric, and electrolytic capacitors are divided into aluminum electrolytic capacitors and tantalum electrolysis by their positive electrodes. Capacitor. The negative electrode of the aluminum electrolytic capacitor is composed of a thin paper/film or an electrolyte polymer immersed in an electrolyte liquid (liquid electrolyte); the negative electrode of the tantalum electrolytic capacitor is usually manganese dioxide. Since the electrolyte is used as the negative electrode (note that it is distinguished from the dielectric), the electrolytic capacitor is named after it.
3, application
Polar electrolytic capacitors usually function as power supply filtering, decoupling, signal coupling, time constant setting, and DC blocking in power supply circuits or intermediate frequency and low frequency circuits. Generally, it can not be used in the AC power supply circuit. When used as a filter capacitor in the DC power supply circuit, the anode (positive electrode) should be connected to the positive terminal of the power supply voltage, and the cathode (negative electrode) should be connected to the negative terminal of the power supply voltage. Otherwise it will damage the capacitor.
Non-polar electrolytic capacitors are commonly used in speaker divider circuits, television S correction circuits, and start-up circuits for single-phase motors.
Electrolytic capacitors are widely used in household appliances and various electronic products. Their capacities range from 1 to 1000 μF and rated operating voltages range from 6.3 to 450V. The disadvantage is that the dielectric loss and the capacity error are large (the maximum allowable deviation is +100%, -20%), the high temperature resistance is poor, and the storage time is long and easy to be invalid.
The polarity of the electrolytic capacitor, pay attention to observe that there is a "-" on the side of the electrolytic capacitor, which is the negative pole. If the positive and negative electrodes are not indicated on the electrolytic capacitor, it can also be judged according to the length of its lead. The long leg is the positive pole and the short leg. It is the negative electrode.
4. Development
In terms of current production, aluminum electrolytic capacitors occupy the second place in capacitors. These capacitors were originally general DC capacitors, but now they have evolved from DC to AC, from low temperature to high temperature, from low voltage to high voltage, from general to special, from general structure to chip, flat, books. Structure and so on. Its upper limit capacity has been extended to about 4F, the frequency of use has reached 30kHz, the operating temperature range has reached -55 °C -125 °C, and some even up to 150 °C, the rated voltage has reached 700V. In short, the development of aluminum electrolytic capacitors is becoming more widespread. The basis for these developments is as follows:
1. In terms of materials, the aluminum foil used now is very elegant in composition and structure. High purity is no longer required, for example, for anode foils, which are required to be of high purity. In order to improve the initial corrosion point, mechanical strength and properties of the dielectric oxide film, the foil should contain some impurities. And some use alloy foil. In terms of structure, for the low-pressure foil, the proportion of the cubic structure is not required to be large, but for the high-pressure foil, the structure is required to account for 80% to 90% or more. In order to increase the specific volume of the cathode foil, an alloy aluminum foil having a certain amount of impurities having a regular orientation of crystal grains is required. The working electrolyte consists of three components. That is, solvents, solutes, and additives, such as electrolytes that have been used for a long period of time, are composed of ethylene glycol, glycerin, boric acid, and aqueous ammonia. Due to the development of aluminum electrolytic capacitors, this electrolyte is far from satisfactory, so many new electrolytes have been produced to reduce the operating temperature range of the capacitor (eg -55 ° C - l25 ° C). The formulation principle of these new electrolytes is: 1 mixed with two solvents. To achieve complementarity. 2 Two weak acids are used to provide the two anionic groups required. 3 add alkali, such as organic amine, to adjust the pH of the electrolyte and flash voltage. Change its resistivity. 4 Additives which improve the characteristics of the electrolyte, such as phosphoric acid or a salt thereof for preventing hydration of the aluminum oxide film, dinitrobenzene which absorbs hydrogen, and the like, and an ethylene oxide which increases the flashover voltage of the electrolyte.
2. In terms of process, in addition to the mechanization and automation of production, the progress of aluminum electrolytic capacitors in the process is mainly the two processes of corrosive phase forming. The corrosion coefficient of aluminum foil is not only high (low-voltage capacitor foil has reached 100, high voltage is up to 25), and aluminum foil with different pothole morphology can be etched according to the performance requirements of the capacitor. The etching process is a kind of corrosive liquid type, concentration, temperature, original foil composition, structure, surface state, foil speed during corrosion, and dynamic balance process of power source type, waveform, frequency, voltage, etc. The question is how to get the best dynamic balance and how to determine the most balanced balance according to the requirements. Therefore, it cannot be said that the current corrosion process has reached the optimum state.
Nowadays, the energization process can produce high-quality dielectric oxide film, and different dielectric oxide films can be manufactured according to different requirements. For example, for DC capacitors, γ and γ'-type crystalline aluminum oxide films are fabricated, and the exchange is performed. The capacitor is an amorphous film. The greatest advancement in the energization process is the ability to convert an aluminum hydroxide film into a dielectric aluminum oxide film and form a water repellent layer on its surface. In addition, defects and cracks in the dielectric film can be eliminated.
3. In terms of structure, the structure of aluminum electrolytic capacitors has been diversified, except for the above liquid aluminum electrolytic capacitors. There are also solid aluminum electrolytic capacitors. There are two main structural forms, one is a foil-wound shape, and the other is an aluminum powder sintered porous block, and the solid electrolyte used is mainly MnO2. The structure of aluminum electrolytic capacitors has been diversified, such as double anode structure, cathode structure, book type structure, triangular structure, and chip structure. Among them, the appearance of chip aluminum electrolytic capacitors is another progress of aluminum electrolytic capacitors. Because there is no high specific volume aluminum foil, high temperature resistant electrolyte, excellent sealing structure and fine processing technology, it is difficult to produce a suitable chip aluminum electrolytic capacitor. The purpose is to compare the chip rate. Low level.
5, the future
Huayu Electronics' TH brand 700V electrolytic capacitor and ultra-large high-voltage large-capacity 100*270mm have been developed. The material used by Capsun and TDK for the YDK-700V capacitor is 820V, which has been applied to the Japanese capsun group. It is extremely epoch-making, which means that the 537V after 380V rectification will no longer need to connect two 400Vs. The performance of aluminum electrolytic capacitors in the future will further develop with the advancement of technology. The normal capacitance of the 700V100uf is usually 35*80-100MM or 50*80-96MM at around $22. Currently used in the world's top capsun, YAMAHA audio is widely exported to high-end hotels in Europe and America. The price of 1200 US dollars to millions of dollars is expensive, and it is mostly used in noble families and hotels. Small-capacity and large-capacity supercapacitors are also being developed.
The test method and test conditions for the leakage current of aluminum electrolytic capacitors are as follows: at 25 ° C, the capacitor to be tested is connected in series with a 1000 Ω protection resistor to the rated voltage to measure the leakage current. After applying the voltage for 5 min, the leakage current does not exceed the maximum value of the specification as qualified. Small-capacity aluminum electrolytic capacitors can use 1min test results. Large-capacity aluminum electrolytic capacitors will require longer test time. As can be seen from the characteristic curve, the current will infinitely approach the final "leakage current" value - supplemental oxidation The current value required for the aluminum medium. The dissipation factor (DF) of an electrolytic capacitor can be understood as the reactive power of the electrolytic capacitor and the active power of the equivalent series resistance (ESR) under the excitation of the alternating current. Obviously, this is the ratio of capacitive reactance to equivalent series resistance (ESR). The RC circuit in the AC circuit, and this ratio is very similar to the opposite side of the trigonometric function - the tangent function. Therefore, the loss factor of the electrolytic capacitor (referred to as DF) is also referred to as loss tangent in many technical documents. The voltage indexes of aluminum electrolytic capacitors mainly include rated DC voltage, rated surge voltage, instantaneous overvoltage and reverse voltage.
Rated DC Voltage VR The rated DC voltage VR is the continuous operating voltage allowed for the capacitor within the rated temperature range. It includes the sum of the DC voltage and the ripple voltage or continuous pulse voltage between the two electrodes of the capacitor. Typically, the rated voltage of the tantalum capacitor is indicated on the surface of the capacitor. Usually rated voltage ≤ 100VT491B107M004AT is a "low voltage" tantalum capacitor, and rated voltage ≥ 150V is a "high voltage" capacitor
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