Aluminum electrolytic capacitors in China are also developing rapidly. According to statistics, the output of 1997 is about15 billion, and it is estimated that it may exceed 20 billion in the near future. Judging from the development of China's electronic industry, the output of aluminum electrolytic capacitors will be greatly improved in recent years. At present, some aluminum foils for electrolytic capacitors in China are made in China, and quite a few are imported. In order to change this situation, domestic manufacturers have done a lot of work in localization. Not long ago, the research project of high-voltage aluminum foil for southwest aluminum electrolytic capacitor was successfully developed, and the product quality reached the international advanced level, which can completely replace imports. It should be said that after 10 years of development, especially in the last five or six years, the quality of electronic aluminum foil in China has been greatly improved.
Aluminum foil for electrolytic capacitors belongs to the category of electronic aluminum foil, which is a corrosive material working under polar conditions. Electronic aluminum foils with different polarities need different corrosion types. The high-voltage anode foil was corroded by columnar holes, the low-voltage anode foil was corroded by sponge, and the middle-voltage anode foil was corroded by insects. Before 1980' s, electrolytic capacitors mostly used artificial chemical corrosion, and after 1980' s, combined electrochemical corrosion was used. The purity of aluminum foil used for manual corrosion is low (99. 3%~99。 7%), the processing quality of aluminum foil is not high. Linkage electrochemical corrosion requires higher and higher purity of aluminum foil and higher and higher processing quality of aluminum foil. In terms of the purity of aluminum, the purity of aluminum in the 1980s was 99. 99%, so far the purity of aluminum has reached 99. 993%。 This is the requirement of electrode foil, and the technology of aluminum processing industry is progressing.
The improvement of aluminum foil purity will certainly have a good impact on the quality improvement of electrode foil, but on the other hand, the cost is also increasing. At the same time, the corrosive media are constantly changing, the concentration of some media is constantly increasing, and the types of some media are constantly changing, which is not conducive to environmental protection work, resulting in heavy environmental protection tasks for production enterprises, and may require reducing the purity of aluminum. From the latest composition analysis of Japanese aluminum foil, it is found that there is a trend in this regard.
The improvement of the quality of corroded foil is inseparable from the improvement of the quality of aluminum foil. According to Japanese patent, the patent peak of negative foil was in 1980s, and the patent peak of positive foil was two: one was about 1977 ~ 1978, and the other was about 1983. The peak of these patents shows that technology has made rapid progress.
From a global perspective, the development trend of electronic aluminum foil is roughly as follows: negative foil also has soft state and hard state. Japan is dominated by soft electrochemical corrosion, while western Europe is dominated by hard chemical corrosion. Both of them have their own advantages and disadvantages. High purity aluminum foil (>: 99 .85%) is copper-free, with excellent quality and high cost. Low purity aluminum foil containing copper is used in hard state, which is low in cost and easy to improve specific volume. In order to develop copper-free or low-copper anode foil with medium electrostatic capacity and low cost, Al-Fe, Al-Mg and other alloys can be used.