The structure of the electrolytic capacitor

The structure of the aluminum electrolytic capacitor, electrolytic capacitors are usually refers to refers to by an aluminum foil winding structure of core, impregnation liquid electrolyte ( Pay attention to distinguish between the dielectric and electrolytes) , raises two end and coating in the sealed metal case. Look from the exterior, core and paper condenser core is similar, but its structure is different, it is composed of an anode foil, separated so saturated with the electrolyte and cathode foil laminated paper roll, foil is usually high purity aluminum foil, in order to increase the surface area of the contact with the electrolyte, and on the smooth surface of the aluminum foil with the corrosion method, the etching of many tiny strip channel. Capacity of the surface seems to be determined by the between the two foil extremely, capacity is actually determined by between electrolyte and anode foil, the anode surface layer is anode foil; The dielectric is anode foil insulation on the surface of the aluminum oxide film; Real cathode plane should be a conductive liquid electrolyte, and the cathode foil is only have the effect of connection electrolyte and end lead. Aluminum electrolytic capacitor production process: a) Anode and cathode foil etching are usually of high purity aluminum foil ( 0. 02 ~ 0. 1 mm thick) Need to increase, in order to increase capacity, foil the effective surface area, using corrosion method was carried out on the surface of aluminum foil in contact with the electrolyte etching ( Tens of thousands of tiny strips) 。 For low voltage capacitor, the increase of surface area can be by etching, 100 times of high pressure is generally for 20 ~ 25 times, namely high voltage capacitor is smaller than the corrosion coefficient of low voltage capacitor, this is due to the high pressure of oxide film thicker, part of the cover after the corrosion of micro ups and downs, reduces the effective surface area. b） Form adhered on the surface of the anode foil capacitance of the dielectric, the dielectric is a thin layer of aluminum oxide ( 氧化铝) , it is by electrochemical method in the anode foil surface by & other; Form Forming” Process of generation. The thickness of the alumina associated with the forming voltage ( 1. 4 to 1. 5nm/V） , usually forming voltage and working voltage have a ratio, the ratio of aluminum capacitor coefficient is small, is 1. 2 ~ 2 ( Solid tantalum capacitors for 3 ~ 5) , so, if there is a 450 v rated voltage aluminum capacitor, if the ratio is 1. 4, the forming voltage is 450 & times; 1. 4 = 600 v, so that the thickness of oxide film is about 1. 5nm× 600 = 900 nm, the thickness is less than one percent of the diameter of a human hair. Formation process reduced the effective surface area of foil. Because of the micro strip channel will be covered by oxide, channel etching type can be adjust through the choice of foil and etching process. In this way, the low pressure channel type and thin oxide anode has a fine, and there is a roughness to the high voltage anode channel type and thickness of oxide film, cathode foil without form, so it also maintain a large surface area and depth of etching. c) Slice of aluminum foil with a rolled up 40 ~ 50 cm wide strip, after etching and forming process, according to the final condenser height specifications cut into the required width. d） Core slice, the aluminum foil bag wiht a layer of isolation on a winding machine according to the paper, the anode foil, another layer of isolation, cathode foil composite paper and winding pillars core structure, and on the outside on the roll of a strip of pressure-sensitive deployed to prevent core. Separated as anode foil and paper liner layer between the cathode foil, foil can be used to prevent two electrode contact and short circuit, at the same time as the carrier of adsorption and accumulation of liquid electrolyte. Or in front of the core package winding winding process, aluminum pad to elicit riveted to the two electrode foil, lead to the end of the capacitance is very behind with convenient. Best riveting method is controlled by microprocessor positioning of cold pressure welding, to ensure that the core in the process of parasitic inductance is less than 2 nh, older riveting method is to pass through the aluminum foil, folded, cold pressure welding to reduce the possibility of a short circuit failure, and under the high ripple current application has good features, and the old riveting way under the charge and discharge applications often make individual connection failure. e) The expansion of the connection terminal aluminum pad which leads to the piece is the terminal capacitance. For the axial lead of the structure of the capacitor, the cathode mat in front of the seal and metal shell welded together. f) Injection liquid electrolyte in core filled with separated paper working electrolyte fully absorbed into the capillary and etching in the pipeline. The injection process is the core of dipping in the electrolyte and heating ( Or heating) Vacuum - forced circulation processing, for small capacity, merely dipping absorption. The electrolyte consists of different chemical composition, according to the different voltage and temperature range application environment, its composition is also different.
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