New Trends in Electronic Foil Technology Development in China

The development of aluminum electrolytic capacitors in China is also very fast. According to statistics, the output in 1997 was about 15 billion, and it is estimated that it may have exceeded 20 billion in the near future. From the perspective of the development of China's electronics industry, the output of aluminum electrolytic capacitors will be greatly improved in recent years. At present, China's aluminum foil used in electrolytic capacitors is partially made of domestic foil, and a considerable part of it is still imported. In order to change this situation, domestic manufacturers have done a lot of work in localization. Not long ago, the high-voltage aluminum foil research project for the use of aluminum electrolytic capacitors in the southwest was successfully developed. The quality of the products has reached the international advanced level and can completely replace imports. It should be said that after more than 10 years of development, especially in the last five or six years, the quality of electronic aluminum foil in China has greatly improved.

The aluminum foil used in electrolytic capacitors belongs to the category of electronic aluminum foil, which is a corrosive material that operates under polar conditions. Different polarity electronic aluminum foils require different types of corrosion. The high-voltage anode foil is corroded in the column hole, the low-voltage anode foil is spongy, and the anode foil in the middle-pressure section is corrugated.

Prior to the 1980s, most of electrolytic capacitors used manual chemical etching. After the 1980s, they used electrochemical electrochemical corrosion. The purity of aluminum foil used for manual etching is low (99.3% to 99.7%), and the requirements for the quality of aluminum foil processing are not high. Linkage electrochemical corrosion requires higher and higher purity of aluminum foil, and more and more precision is required for the processing quality of aluminum foil. From the aspect of the purity of aluminum, the purity of aluminum was 99.99% in the 1980s, and the purity of aluminum has reached 99.993% so far. This is the demand for electrode foils and the progress in the aluminum processing industry.

The increase in the purity of the aluminum foil naturally brings about a good influence on the quality of the electrode foil, but on the other hand, the cost is increasing. At the same time, corrosive media are constantly changing, some media concentrations are increasing, and some media types are changing. These are all unfavorable to environmental protection work, which leads to heavy environmental protection tasks for production companies, which may require the purity of aluminum to be reduced. From the latest composition analysis of Japanese aluminum foil, it has been found that there is a trend in this area.

The improvement of the quality of corroded foils is inseparable from the progress made in the quality of aluminum foils. From the perspective of Japanese patents, the peak period of patents for negative foils was 1980s, and there are two peaks for anode foils: one peak. About 1977 to 1978, another peak around 1983. The peak period of these patents indicates that the technology is rapidly advancing.

From a worldwide perspective, the development trend of electronic aluminum foil is roughly as follows:

High-voltage anode foil

High-voltage anode foil can be divided into two categories, one is high-quality high-voltage foil; the other is ordinary high-voltage foil.

The characteristics of high-quality high-voltage anode foils are "two high and one thin", namely high purity, high cubic texture and thin surface oxide film. These products are of high quality but costly. The purity of aluminum is >99.99% and the cubic texture is 96%. Vacuum heat treatment is performed under conditions of 10-3 Pa to 10-5 Pa.

Ordinary high-voltage anode foil is an economical and practical high-voltage anode foil with an aluminum purity of >99.98%, a cubic texture of >92%, and a vacuum heat treatment at 10-1 to 10-2 Pa.

Low-voltage anode foil

The process of low-voltage anode foils is relatively complicated, and we think that it is not possible to adopt a method to meet the requirements of each segment voltage, which can be roughly divided as follows.

For low-voltage foils of less than 35Vf, the corrosion of hard, high-purity aluminum foils should be developed. The characteristic is that the hard-state can provide a large number of corroded fine cores and etched channels. As for DC corrosion and AC corrosion, which kind of power source is better to be studied. Industry insiders believe that the specific volume of the method can be increased by 5μF/cm2 compared to the soft-state method.

Low pressure foils larger than 50Vf and soft high-purity aluminum foils provide conditions in which many crystal planes are poorly oriented, and it is possible to obtain corrosion foils with large etching holes.

Negative foil

Negative foils also have soft and hard states. Japan is dominated by soft electrochemical corrosion, and Western Europe is dominated by hard chemical corrosion. Both have their own advantages and disadvantages. The high purity aluminum foil (>99.85%) in the soft state has no copper and is of high quality and high cost. The hard state is a low purity copper containing aluminum foil, which has low cost and is easy to improve. . In order to develop a negative electrode foil having a moderate electrostatic capacity and a low cost, copper-free or low-copper negative electrode, an alloy such as AL-Fe or AL-Mg can be used. The high-purity low-copper aluminum foil, which is based on high-purity aluminum and added with trace amounts of copper as a corrosion core, can have a specific volume comparable to that of a high-purity soft electrochemical electrochemical method. Due to its low cost, it should be welcomed by the market.