Aluminum electrolytic capacitors development prospects?
For now the production, the aluminum electrolytic capacitors occupy second place in the capacitor. Originally these capacitors are generally DC capacitor, but has now grown from DC to AC, the development from low to high, the development from low to high pressure, from the universal to the development of special type, developed from the general structure of the piece, flat, books type and other structures. Its capacity limit has been extended to about 4F, frequency of use has reached 30kHz, has reached operating temperature range -55 ℃ -125 ℃, and some even as high as 150 ℃, rated voltage has reached 700V. In short, the development of an aluminum electrolytic capacitor more widely. These developments led to the following basis:
1, in the material, now with aluminum foil on the composition and structure are very elegant. No longer require high purity, e.g., the anode foil, which require high purity to be appropriate. In order to improve the starting points of corrosion, mechanical strength and dielectric properties of the oxide film, foil to the appropriate contain some impurities. And some use foil. In structure, low pressure foils, does not require a large percentage of a cubic structure accounted for, but for high pressure foils, this structure requires an account for more than 80% 90%. Cathode foil.
In order to improve its specific volume is required grain randomly oriented trash content certain alloy foil. There are three components working electrolyte composition. I.e. the solvent, solute and additives, have long been applied as the electrolyte, which component is ethylene glycol, glycerin, boric acid and ammonia. Since the development of an aluminum electrolytic capacitor, which can not meet the requirements of the electrolytic solution has, therefore produce many new electrolytic solution, in order to reduce the capacitor's operating temperature range (e.g. -55 ℃ --l25 ℃). These new electrolyte formula principle is: ① mixing two solvents. In order to achieve complementarity. ② by two weak acid, to provide the required two anionic groups. ③ alkali, such as an organic amine, to adjust the pH value and the electrolyte sparking voltage. Changes its resistivity. Improved electrolyte additives ④ characteristics, such as to prevent the aluminum oxide film hydration of phosphoric acid or a salt thereof, the hydrogen-absorbing dinitrobenzene, etc., to improve the sparking voltage of the electrolytic solution of ethylene oxide.
2, in the process, in addition to already realize mechanization and automation of production outside the progress in the process of aluminum electrolytic capacitors are mainly corrosion phase enabling two processes. Corrosion of aluminum foil, not only has a high coefficient (low-voltage capacitor foil has reached 100, the high pressure by up to 25), and can be based on the performance requirements of the capacitor, the corrosion of aluminum foil with different morphologies potholes. The etching process is an etching solution type, concentration, temperature, original foil composition, structure, surface state, the speed of the corrosion process and foil type power, waveform, frequency, voltage, etc. of dynamic equilibrium process. The question is how to draw the best out of homeostasis and how to determine the mass balance in accordance with the requirements. So, right now etching process can not be said to have reached the best condition.
Now forming process may have created high-quality dielectric oxide film,
3, but also according to different requirements, create a different dielectric oxide film, for example, the DC capacitor, produce γ and γ 'type crystalline alumina film, AC capacitors, for the amorphous film. Forming greatest progress process of aluminum hydroxide is capable of dielectric film into an aluminum oxide film, and can form a waterproof layer on its surface. In addition, but also to eliminate defects and cracks dielectric film.
4, in the structure, the structure of the aluminum electrolytic capacitor has been diversified, in addition to the outer liquid aluminum electrolytic capacitor. There are solid electrolytic capacitors. There are two main forms of its structure, one is shaped foil winding, and the other is a sintered porous block of aluminum, the use of solid electrolyte is mainly MnO2. Aluminum electrolytic capacitor structure has diversified, such as dual anode structure of the cathode structure, the book structure, triangular structure, piece structure. Appear among chip electrolytic capacitors aluminum electrolytic capacitor is also - progress. Because if there is no high hematocrit of aluminum foil, high temperature electrolyte, excellent sealing structure and fine processing technology, it is difficult to make a desirable piece of aluminum electrolytic capacitors, the purpose, the chip rate is still in the relatively low level.
