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SMD aluminum electrolytic capacitor solution

HITS:83     DATE:2020-09-19 17:10:34    
Nowadays, with the development of social economy and the improvement of high-tech standards, monolithic capacitors and high-voltage ceramic capacitors are becoming more and more popular in the daily lives of ordinary people, and they are inside the lighting fixtures. Because the metal material tantalum is used as the substance, there is no need to use lithium battery electrolyte like the general electrolysis method. In addition, SMD electrolytic capacitors do not need to be made of aluminum-plated capacitor paper like ordinary electrolytic capacitors, so there is basically no inductor itself, but it also limits its volume. It is used in areas with large-space filtering. For example, you can see the shadow of patch electrolytic capacitors around the CPU socket. It is mostly used with ceramic capacitors, electrolytic capacitors are used in conjunction with each other or used in areas where the working voltage and current are not large . File Directory 1. A detailed introduction to the plan of aluminum electrolytic capacitors Second, the advantages of post-chip aluminum electrolytic capacitors Three, the effect of aluminum electrolytic capacitors Fourth, the basic parameters of aluminum electrolytic capacitors Five, the characteristics of aluminum electrolytic capacitors Six, the structure of aluminum electrolytic capacitors Seven, the basic principle of aluminum electrolytic capacitors Eight, the development trend of aluminum electrolytic capacitors Article body 1. A detailed introduction to the plan of aluminum electrolytic capacitors An electrolytic capacitor is a capacitor made of an air oxide film produced by the electrolytic method as a material. The aluminum electrolytic capacitor uses high-purity aluminum as anodized, and an emulsion composed of ethylene glycol, glycerol, boron, and sodium hydroxide as the lithium battery electrolyte. The electrolysis method makes aluminum in the lithium battery electrolyte. The surface layer creates a layer of ultra-thin aluminum oxide film as a capacitor made of material. Electrolytic capacitors can be made very thin because the plastic film of the electrolytic medium can be made very thin, so a capacitor with a small size and a large volume can be made, which is a key part of a large space capacitor. However, electrolytic capacitors have many shortcomings, such as poor frequency well characteristics and temperature characteristics, and large leakage current and material damage. In addition, when the optical rotation is reversed or the working voltage applied on both sides exceeds the specification model, the safety factor will be destroyed, and the lithium battery electrolyte will be vaporized and exposed (ie, the alias is bluntly penetrating). External environmental factors will cause the deterioration of electrolytic capacitor characteristics, such as temperature, environmental humidity, standard pressure and vibration, etc. The hazards at the electrical equipment level include working voltage, ripple, current, and battery charging. Second, the advantages of aluminum electrolytic capacitors Compared with the traditional electrolytic capacitors, the post aluminum electrolytic capacitors use conductive fiber materials with high conductivity and high reliability as the solid electrolyte, instead of the lithium battery electrolyte of the traditional aluminum electrolytic capacitors. The high conductivity of the electrolyte solution, coupled with its unique overall design, greatly improves the defects of traditional liquid aluminum electrolytic capacitors, showing extremely excellent characteristics. 1. Idealized high frequency and low characteristic impedance characteristics. High polymer solid electrolytic capacitors have very low loss and have ideal high frequency and low characteristic impedance characteristics. Therefore, they are widely used in power circuits such as decoupling and filtering design schemes. The actual effect is ideal, especially for high frequency filtering. The actual effect is excellent. According to an experiment, it can be seen more vividly and eliminated that the high-frequency characteristics of high polymer solid aluminum electrolytic capacitors and general capacitors are significantly different. Type in the smooth power supply circuit to accumulate 1MHz (peak-to-peak working voltage: 8V) high-frequency electromagnetic interference, and filter with a 47UF high polymer solid electrolytic capacitor to reduce the noise to only 30mv peak-to-peak working voltage. . To achieve the same filtering effect, four 1000UF general-purpose liquid aluminum electrolytic capacitors must be connected in series, or three 100UF tantalum electrolytic capacitors must be connected in series. 2. Strong working ability to withstand large harmonic distortion current. The high polymer solid electrolytic capacitor material has the ability to withstand large harmonic distortion current, which is suitable for showing a large current in the power supply circuit of the switching power supply circuit in a short period of time. In a short period of time, the DC voltage will drop significantly, so it has a strong working ability to show high-frequency current and has very good instant response characteristics. 3. Smooth frequency characteristics and excellent temperature characteristics. The high polymer solid electrolytic capacitor with high polymer material has a flat capacity-frequency characteristic in the frequency range of 0, 1~10MHz. It also has excellent temperature characteristics, the general temperature changes from -55 degrees to 105 degrees, and the capacity is only changed -5% to 8%. The polymer material high polymer solid aluminum electrolytic capacitor also has long life, high reliability, and it is critical Used in computer motherboard bypass capacitors, DC/DCSPWM, small and medium-sized high-power resistors, switching power supply decoupling, high-frequency noise suppression power supply circuits and portable electronic products, etc. High polymer solid aluminum electrolytic capacitors are not easy to ignite, smoke, and explode because they use aluminum and conductive polymer materials and high polymer raw materials. Three, the effect of aluminum electrolytic capacitors An electrolytic capacitor is a capacitor made of an air oxide film produced by the electrolytic method as a material. The aluminum electrolytic capacitor uses high-purity aluminum as anodized, and an emulsion composed of ethylene glycol, glycerol, boron, and sodium hydroxide as the lithium battery electrolyte. The electrolysis method makes aluminum in the lithium battery electrolyte. The surface layer creates a layer of ultra-thin aluminum oxide film as a capacitor made of material. 1. Filtering effect In the circuit, the inverter circuit converts the communication AC into the DC power of the pulsating beverage, and after the inverter circuit is connected a large-volume electrolytic capacitor, using its battery charging characteristics, makes the pulsating beverage AC voltage after the rectifier become relative Relatively stable AC voltage. In detail, in order to better avoid changes in the operating voltage of each part of the power supply system due to load changes, the output terminal of the switching power supply and the input terminal of the switching power supply of the load are generally connected with tens to hundreds of microfarads. Capacitance. Because large-space electrolytic capacitors generally have certain inductors, high-frequency and single-pulse electromagnetic interference cannot be filtered out reasonably, so a capacitor with a volume of 0, 001--0, lpF is connected in series on both sides , To filter out the effects of high frequency and single pulse. 2. Coupling In the process of low-frequency data signal transmission and transformation, in order to avoid the mutual influence of the static operating points of the front and rear left and right secondary power circuits, capacitor coupling is often used. In order to better avoid excessive damage to the low frequency of the rhyme in the data signal, it is generally selected A large electrolytic capacitor. Fourth, the basic parameters of aluminum electrolytic capacitors 1. The height of the equivalent circuit connected in series with the ESR ESR is related to the structure of the electrolytic capacitor, the volume of the electrolytic capacitor, the working voltage, the frequency and the temperature. The lower the ESR, the better. When the rated current is fixed, the larger the volume, the lower the ESR. When the volume is fixed, the high rated current type can reduce the ESR. The ESR is high at low frequencies, and the ESR is low at high frequencies. High temperatures will also increase ESR. Many well-known brands of equivalent circuit series resistance ESR can be found in the test plan. 2. Leakage current Aluminium electrolytic capacitors all have power failure, which is determined by the physics structure. Not to mention, the leakage current is naturally as low as possible. The higher the volume of the electrolytic capacitor, the greater the leakage current; reducing the working standard voltage can reduce the leakage current. On the contrary, using a higher compression type will also help reduce leakage current. Combining the two main parameters above, it is indeed a simple and feasible method to preferentially select the high compression type under the same standard; reduce internal resistance, reduce leakage current, reduce damage angle, and increase service life. There are so many benefits, but the price is higher. There is a name, that is, when the electrolytic capacitor is working at a voltage much lower than the rated working standard voltage, because it is not possible to obtain a reasonable enough to maintain the depolarization effect between the electric level and the lithium battery electrolyte, it will cause the electric polarization of the electrolytic capacitor. Reduce the amount of ripple current, expand ESR, and embrittlement earlier. However, the prerequisite for this name is "far less than the rated working standard voltage". According to some long-term social experience, the 2/3 of the rated working standard voltage tolerance is all normal working standard voltages. , It is more effective and safe. In the amateur group, the leakage current to the electrolytic capacitor is roughly possible. Charge the battery with an electrolytic capacitor of the same volume under the working voltage according to the rated value, and then check the reduction level of the working voltage on both sides of the electrolytic capacitor after a period of time. The lower the operating voltage, the smaller the leakage current. 3. The main parameter of tolerance is the standard value ① electrostatic induction volume listed on the casing of electrolytic capacitor, which is indicated by uF. ②Working voltage (working voltage) is generally called WV, which should be the standard value of tolerance. In other words, the nominal voltage cannot be exceeded in the power supply circuit. ③Temperature: The most common temperature is 85 degrees and 105 degrees. Under high temperature standards (such as pure class A power amplifiers), the 105-degree tolerance should be selected. Under normal circumstances, the selection of the main parameter characteristics of the high temperature index for improvement is also proactive assistance. 4. Under the effect of electrostatic field, the kinetic energy consumed by the depletion capacitor due to hot per unit time is called depletion. All kinds of capacitors require a specified value of loss in a certain frequency range. The loss of a capacitor is mainly caused by dielectric loss, redox potential loss and a part of the capacitor's resistors of all metal materials. Under the effect of the DC power field, the loss of the electrolytic capacitor exists in the form of leakage conduction loss, which is generally small. Under the effect of the alternating electric field, the loss of the capacitor is not only related to the leakage conduction, but also created by regular electrical polarization. The whole process is relevant. 5. Harmonic distortion current: The harmonic distortion current is a very important main parameter for Shiji's low-pass filter. The amount of harmonic distortion current is as high as possible. Its height is related to the output power. The higher the frequency, the greater the amount of harmonic distortion current, and the lower the frequency, the smaller the amount of harmonic distortion current. Traditionally, people must have a high harmonic distortion current at low frequencies, and seek to obtain excellent high current charging and discharging characteristics, making the low frequency more solid, round and malleable, and its excellent operating driver characteristics ; In fact, the high harmonic distortion current at high frequency also greatly assists the sound quality, which can make the high frequency have a stronger broadening and reduce the roughness. 6. Frequency characteristics: With the increase in frequency, the capacity of general electrolytic capacitors shows a regularity of decrease. Five, the characteristics of aluminum electrolytic capacitors 1. There are optically active electrolytic capacitors Due to the internal structure of the optically active electrolytic capacitor, the two pins have positive and negative points. They cannot be reversed in the application. Otherwise, it will not only have all normal functions, but will continue to cause explosions. In order to alleviate this kind of damage, explosion-proof ports are set up on this type of electrolytic capacitors. The characteristic of the optically active electrolytic capacitor is that the volume can be very large, and the larger the volume, the larger the volume, and the larger the leakage current. 2. Non-optical electrolytic capacitors Non-optical electrolytic capacitors are also called double-optical electrolytic capacitors. Because of the use of double air oxide film structure engineering, non-optical electrolytic capacitors make the pins of electrolytic electrolytic capacitors non-optical, and save the electrolysis. Capacitors have the advantages of small size, large volume and low cost. The crossover capacitor of the crossover power circuit in the speaker is a non-optical electrolytic capacitor. 3. Tantalum electrolytic capacitors Tantalum electrolytic capacitors are packaged with waterproof and flame-retardant epoxy resin glue. They have small size, low leakage current and dielectric loss, good frequency and temperature characteristics, long life, high stability, good reliability, and a wide range of work In the temperature range, the characteristics are stable during long-term work and after being idle. It is suitable for top national defense, electronic computers, vehicles, communications, high-end electrical products and other industries. 4. Non-solid tantalum electrolytic capacitors It is a tubular semi-hermetic, optically active, non-solid electrolytic medium, calcined anodized tantalum electrolytic capacitor. It has the advantages of small size, low leakage current, high-quality characteristics, stability and reliability, and long life. Suitable for military and civilian electronic products such as communications and aerospace. 5. Solid tantalum electrolytic capacitor It is a plastic shell sealed solid electrolytic medium electrolytic electrolytic capacitor. It has the advantages of small size, wide working temperature, stable and reliable characteristics, and long life. It is universally applicable to military and civil instrument equipment and other electronic products. Six, the structure of aluminum electrolytic capacitors The elements of aluminum electrolytic capacitors are composed of high-purity aluminum platinum, and the middle of the positive and negative is made of electrolytic paper pre-impregnated with lithium battery electrolyte as the separated layer. The outside is composed of rubber plugs and aluminum shells, using aluminum shells. The purpose of the sealing gasket is to better maintain the internal elements and prevent the evaporation of the lithium battery electrolyte to ensure the service life of the product. The function of the pressure valve on the aluminum electrolytic capacitor is that when it is misused, such as when the negative working voltage is connected or the positive working voltage is too large, the internal working pressure will expand. In order to better avoid the explosion of the capacitor, a part of the capacitor is made very Thin to have the effect of a pressure valve. The pressure valve is located at the top of the capacitor, so when a capacitor with a pressure valve is used, there must be sufficient indoor space above it. Seven, the basic principle of aluminum electrolytic capacitors Electrolytic capacitors are generally made of metal material foil (aluminum/tantalum) as the positive electrode, and the insulating layer air oxide layer (aluminum oxide/tantalum pentametal oxide) of the metal material foil is used as the electrolytic medium. The electrolytic capacitor is due to its positive electrode. The difference is divided into aluminum electrolytic capacitors and tantalum electrolytic capacitors. The negative electrode of aluminum electrolytic capacitor is composed of plastic paper/plastic film or high polymer of electrolyte solution soaked in electrolyte solution (liquid electrolyte solution); the negative electrode of tantalum electrolytic capacitor is generally manganese dioxide. Because the electrolyte solution is used as the negative electrode (note the difference from the electrolytic medium), the electrolytic capacitor is famous for it. Eight, the development trend of aluminum electrolytic capacitors With the continuous development trend of electrolytic capacitor production technology, the continuous reduction of machine equipment manufacturing costs and raw material costs, the solution capacitor has also become a widely optimistic quality for manufacturers, and its development direction may also show the following types of development trends: 1. Reduced volume and flat design In recent years, with this point, the continuous increase in the specific capacitance of aluminum and platinum in capacitors has created the necessary conditions for the reduction of the volume of electrolytic capacitors and the reduction of costs. The compression strength of the foil is improved. The flat design of the capacitor at the end and the entire machinery Thin words set the standard. The development trend of aluminum platinum with high toughness and high specific volume has also led to the continuous reduction of capacitor volume and flat design. 2. Low characteristic impedance resistance, harmonic distortion current flow, long life The development and design of high-conductivity raw materials and ionic liquids has promoted the continuous improvement of the conductivity of the electrolyte solution. The density and characteristic impedance of the foil paper of the new solution capacitors are also continuing to decrease. The development trend of heat-resistant rubber seals for capacitors is that the capacitors are low. The characteristics of characteristic impedance, resistance to large harmonic distortion and long life are greatly improved. In the natural environment of high-temperature work, tens of thousands of hours of capacitor products also occur correspondingly. 3. The service life of limiting the temperature during work continues to increase With the development trend of the vehicle electronics industry, the service life of capacitors under restricted temperature operation has continued to improve. The service life of 125℃ capacitors has been increased from 1000~2000h to 3000~5000h, and the working temperature is limited to 150℃, and the service life is 1000 ~2000h aluminum electrolytic capacitors are also mass-produced. With the continuous development trend of the automotive industry, the use period of capacitors in limited work temperature will also develop further. 4. Solid state electricity
 
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