Structural model of low-voltage etched foil for aluminum electrolytic capacitor

Abstract: The structure-property characteristics of high-performance low-voltage etched foils of Japan were analyzed and the structural model was discussed in detail. The mercury porosimeter measurements and electrical performance test of solid-state aluminum electrolytic capacitor were adopted to verify the model. The results show that the performance difference between U179H and LT23B etched foils is mainly due to their different pore-throat structures. To maintain electrical neutrality, Cl- ions tend to accumulate at the corners of the pits, leading to pit initiation at weak points near the corners. Moreover, Cl- ions with high concentration facilitate the formation of AlCl3 salt film, which makes the sidewalls near the pitting point passivated and the internal pits structure kept the cubic structure. Consequently, a narrow channel is formed at the junction of the cubic etched cell, which affects the specific capacitance of the etched foil and the rate of capacitance withdrawing of the solid aluminum electrolytic capacitor. Therefore, it is a strategy to improve the performance of low-voltage etched foil by reducing the pore-throat ratio.

Keywords: aluminum electrolytic capacitor; low-voltage etched foil; structural model; pore-throat ratio; specific capacitance; rate of capacitance withdrawing

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