Study of a complex of physical, crystallographic and mechanical properties of aluminum foil for electrolytic capacitors

Abstract

The results of studies of the complex of physical, crystallographic and mechanical properties of aluminum foil for low-voltage and high-voltage electrolytic capacitors made of high-purity aluminum (99.99% Al) are presented. A comparative analysis of technological schemes for the production of foil for lowvoltage and high-voltage applications is given, the main differences in the schemes are shown, and the results are presented for the physical parameter: the value of specific capacitance, crystallographic characteristics (structure and predominant texture), mechanical properties (tensile strength and relative elongation). Low-voltage foil after electrochemical etching has a fine etching relief, which can cause the danger of its smoothing after the next operation of the electronic processing of molding — the creation of an oxide film of the dielectric. The required surface topography can be achieved at high total degrees of cold deformation, amounting to 98.8%, without intermediate annealing, obtaining a structure that is fibrous along the rolling direction with a predominant deformation texture {011} and pole density according to the results obtained (5.2). On the contrary, high-voltage foil after electrochemical etching has a rougher relief, and here the risk of surface smoothing after the molding operation is minimal, since the dielectric oxide film being formed is actually superimposed and duplicated along the trajectory of the resulting relief. The latter can be achieved by using a foil after recrystallization (intermediate) and final annealing to obtain an average grain size of about 72 microns, a predominantly near-cubic texture of the {420} foil, and a pole density of 2.4 obtained results. At the same time, high values of specific capacitance can be observed in the studied range: at forming voltages of 30 and 450 V, the value of specific capacitance is 1750 and 29 μF/dm2 for low-voltage and high-voltage foils, respectively.