Mechanistic Study on Electrical Performance Differences Between Sintered and Etched Foils in Aluminum Electrolytic Capacitors

Abstract In the manufacturing of anode foils for aluminum electrolytic capacitors, etched foils and sintered foils exhibit distinct differences in specific capacitance and voltage withstand characteristics due to variations in their manufacturing processes, with the underlying mechanism remaining unclear. This study investigated these differences by varying hydration pretreatment times and formation voltages. Results show etched foils, with tunnel pores, develop a dense, highly crystalline γ–Al₂O₃ phase in their oxide layer as voltage increases. This phase enhances voltage resistance by dispersing the electric field. However, the "inward growth" of this oxide increases dielectric thickness and blocks electrolyte channels, reducing specific capacitance at higher voltages. Conversely, sintered foils possess an aluminum particle packing structure enabling less constrained oxide growth. This results in a lower-density oxide with weaker voltage resistance. Critically, the sintered foil's loose oxide structure maintains a high specific surface area and reduces ion migration resistance, yielding significantly higher specific capacitance than etched foils. Analysis of oxide morphology, crystallinity, and pore evolution clarifies the intrinsic mechanisms for the performance differences, providing a theoretical basis for capacitor optimization.