Aluminum foil for electronic power capacitors
Aluminum foil for electronic power capacitors is a key material for manufacturing electrodes for various capacitors. Leveraging its excellent conductivity, electrochemical properties, and ease of processing, high-purity aluminum provides energy storage and filtering functions in electronic devices and power systems. This type of aluminum foil is typically divided into anode and cathode foils, with thicknesses ranging from 4 to 100 μm. The anode foil undergoes corrosion and chemical conversion treatment to form a porous oxide film as a dielectric layer, while the cathode foil requires a smooth surface and high purity to conduct current. The material is often high-purity aluminum with a purity of over 99.9%, such as grades 1060, 1145, and 1235. The stable electrochemical performance is ensured by strictly controlling the content of impurities such as iron and silicon (≤0.03%).
The production process for aluminum foil used in electronic power capacitors requires precision steps, including smelting, casting, cold rolling, intermediate annealing, finish rolling, and surface treatment. First, high-purity aluminum ingots are heated to 700-750°C in a smelting furnace to melt. Refining agents are added to remove hydrogen and non-metallic inclusions, raising the purity of the molten aluminum to over 99.97%. A continuous casting and rolling process is then used to produce aluminum strip with a thickness of 6-10mm. During the casting and rolling process, the cooling rate and rolling force are controlled to ensure uniform and segregation-free microstructure. Cold rolling is a key step in achieving ultra-thin aluminum foil. The strip is gradually thinned to the target thickness through multiple cold rolling passes, with a reduction of 20%-30% per pass. Specialized rolling oil is used for lubrication and cooling to prevent surface scratches and maintain a thickness tolerance of ±0.2μm . Intermediate annealing is performed during the cold rolling process. The aluminum foil is heated to 300-400 °C, held at this temperature for 2-4 hours, and then slowly cooled to eliminate work hardening, restore the material’s plasticity, and ensure smooth subsequent rolling. After finishing, the anode foil undergoes corrosion treatment. Through electrochemical or chemical methods, a porous structure is formed on the surface to increase the specific surface area (up to 50-100 times the initial area). Subsequently, a chemical conversion treatment is performed to form a uniform oxide film ( Al₂O₃ ) on the surface as a dielectric. The thickness of the oxide film is controlled to 0.01-0.1μm according to the withstand voltage requirements . The cathode foil undergoes surface treatment such as cleaning and drying to remove oil and impurities and ensure conductivity.
The performance characteristics of aluminum foil used in electronic power capacitors directly determine the quality of the capacitors. First, high purity is a basic requirement. Aluminum foil with a purity of ≥99.9% has excellent conductivity and electrochemical stability, can reduce leakage current caused by impurities (≤0.1μA/cm²), and improve the insulation performance of the capacitor. The iron content must be controlled at 0.01%. The following requirements apply: silicon content ≤ 0.02%; secondly, a uniform microstructure is crucial. By controlling the rolling and annealing processes, the aluminum foil grains are made small and uniform (average grain size ≤ 15μm), avoiding inconsistent oxide film thickness during corrosion and chemical formation due to uneven structure, and ensuring a withstand voltage deviation of ≤ 5%; thirdly, good ductility ensures the production and processing of ultra-thin aluminum foil. The elongation must be ≥ 3%, which can withstand large deformations during cold rolling without breaking, while facilitating subsequent corrosion and forming; fourthly, the surface quality is excellent. The surface roughness of the anode foil Ra ≤ 0.2μm ensures a uniform distribution of the porous structure after corrosion, thereby improving the specific capacity; the surface of the cathode foil is free of oil stains and oxidation spots, and the contact resistance is ≤ 10mΩ, which is conducive to current conduction; fifthly, the electrochemical performance is stable. The oxide film formed on the anode foil after chemical formation has a high breakdown voltage (≥ 500V/μm) and low leakage current. The performance change rate after 1000 hours at 85°C is ≤ 10%, ensuring the service life of the capacitor.
Aluminum foil for electronic power capacitors is a core material for various capacitor types across various application scenarios. In the consumer electronics sector, power management modules in smartphones and laptops utilize small aluminum electrolytic capacitors with 4-10μm anode and cathode foils, achieving miniaturization and high capacity (up to 1000μF). In the power system sector, high-voltage reactive power compensation capacitors utilize thick anode foils of 50-100μm. By optimizing the corrosion process, the specific capacity is increased to meet high voltage (above 10kV) and large capacity requirements. In the home appliance sector, compressor starting circuits in air conditioners and refrigerators utilize electrolytic capacitors with 10-30μm aluminum foil, balancing cost and performance. In the new energy vehicle sector, DC link capacitors in onboard chargers and inverters utilize high-voltage aluminum foil (breakdown voltage ≥ 600V) to ensure high power output . In the industrial sector, filter capacitors in inverters and UPS power supplies utilize wide-width aluminum foil (≥ 600mm), increasing capacity by increasing surface area and ensuring stable equipment operation. With the development of new energy and smart grids, the application of aluminum foil for electronic power capacitors in high voltage and high frequency fields is also increasing.
Industry trends indicate that aluminum foil for electronic power capacitors is trending towards ultra-thinness, high specific capacitance, and high-temperature resistance. Continuous breakthroughs in ultra-thin aluminum foil production technology have enabled the stable production of aluminum foil below 4μm, suitable for miniaturized, high-capacity capacitors. By utilizing high-precision cold rolling mills and new rolling oils, thickness tolerances can be controlled to ±0.1μm. High-specific capacitance aluminum foil, through optimized etching processes (such as bipolar etching), increases surface area by over 30% at the same thickness, boosting capacitor capacity by 20%, meeting the high-capacity demands of electronic products. High-temperature-resistant aluminum foil, by adding trace alloying elements (such as titanium and zirconium) to enhance the thermal stability of the oxide film, achieves a leakage current increase of ≤15% at 125°C, making it suitable for high-temperature applications such as new energy vehicles. Furthermore, the promotion of green production processes, including the use of environmentally friendly rolling oils and cleaning agents, reduces volatile organic compound emissions, increasing the aluminum foil recycling rate to over 95%. In the future, with the rapid development of new energy and electronic information industries, the demand for high-performance aluminum foil for electronic power capacitors will continue to grow, driving the industry to make greater breakthroughs in material research and development, process innovation and performance improvement.
