In conclusion, aluminum foil and other metal foils are widely used in capacitors due to their favorable electrical properties, processing characteristics, and cost-effectiveness.
Why do aluminum electrolytic capacitors have colossal capacitance?
Aluminum electrolytic capacitor construction delivers colossal capacitance because etching the foils can increase surface area more than 100 times and the aluminum-oxide dielectric is less than a micrometer thick. Thus the resulting capacitor has very large plate area and the plates are intensely close together.
1. General Description of Aluminum Electrolytic Capacitors An aluminum electrolytic capacitor consists of cathode aluminum foil, capacitor paper (electrolytic paper), electrolyte, and an aluminum oxide film, which acts as the dielectric, formed on the anode foil surface.
A 0.05~0.11 mm thick anode foil and a 0.02~0.05 mm thick cathode foil are continuously etched electrochemically in a chloride solution with an AC or DC current. This enlarges the effective surface area of the aluminum foils to attain smaller capacitor sizes. The process develops aluminum oxide (Al203) to form a capacitor dielectric.
Can aluminum electrolytic capacitors be applied for a short time?
Aluminum electrolytic capacitors can be applied for a short time with an overvoltage, also called a surge voltage.
The cathode foil has a capacitance (Cc) that uses the oxide layer, which formed by the forming voltage or formed naturally during storage (generally 1V or less), as a dielectric. According to the construction of aluminum electrolytic capacitors, Ca and Cc are connected in a series.
Furthermore, the PL Law (Product Liability) has been enforced, therefore, safety is regarded as important more than before. For such reasons, aluminum electrolytic capacitors that are used in power supplies are required to have the following features: miniature, light in weight, thin, extended life and high reliability, chip type, and safer.