Research Of Etching Process On Extending Surface Area Of High Voltage Anode Foil For Aluminum Electrolytic Capacitors

High pressure anode electronic aluminum foil is high-end products of aluminum foil, it is widely applied to the electrolytic capacitor materials which is an important component electronic industry. At present, with miniaturization and high-integration development of electronic products, the market demands for higher performance for aluminum electrolytic capacitors, in other words, we should try to reduce the size of aluminum electrolytic capacitors under the premise of ensuring the performance (high capacitance). Therefore, study of electrolytic capacitor miniaturization (That is to achieve high capacitance) is not only the key to develop high performance electrical products, but also high capacitance research is the hotspot in this field. The surface corrosion of anode aluminum foil is an effective method to improve the specific capacitance of electrolytic capacitors. In this paper, the effects of aluminum foil DC corrosion process on the specific capacitance were investigated, influences of inhibitor on the specific capacitance had been researched to obtain the large surface area of etched foils. To some extent, aluminum foils are increased the specific capacitance while maintaining a good surface quality of aluminum foil.Influence of prophase pretreatment, composite of etching solution and concentration, corrosion time, corrosion temperature, current density and sustained-release of inhibitor in acid etching system are investigated with analytical techniques such as analysis of weightlessness, polarization curve(Tafle), electrochemical impedance spectrum(EIS), optical microscopy(OM), scanning electron microscopy(SEM). In the end, appropriate corrosion process parameters had been obtained in high anode aluminum foils through the analysis of relevant experimental results.As to the surface corrosion of high voltage anode aluminum foil, direct current (DC) electrochemical pitting technology was used and the better electric pitting conditions are decided by orthogonal test and single factor test. The electric etching conditions are:etching solution being2mol/LHCl+0.6mol/LH3PO4+1.5mol/LH2SO4, direct current density being0.3A/cm2, etching time being60s, etching temperature being70℃etching temperature.The results indicated that impact of the current density on capacitance of the etched foils was the greatest in the corrosion process factors, second was etching temperature and etching time. While the current density was smaller, the pit density was lower and the pit size was bigger, on the contrary, the pit density became higher and the pit size changed smaller when current density was larger. Etching temperature and etching time mainly affected the length and growth.The experimental results showed that effect of the current density on the further growth of etched pit was greater in the process of electrochemical tunnel-widening. The appropriate current density made for the growth of longitudinal direction of the pitting, at the same time, the preferable result of extending the coverage of aluminum foils was achieved in the end. A preferable technology for tunnel-widening was:at60℃, in1mol/LHCl of solution, with0.15A/cm2-0.25A/cm2current density and etching80s-90s.On the basis of previous experiments, effect of corrosion inhibitor on the specific capacitance of high-voltage anode foil was investigated. By adding corrosion inhibitor in etching solutions, the etched foil were maintained the original pit density and distribution of the pit tended to be uniform, furthermore, phenomenon of excessive corrosion of etched foil reduced and weight loss decreases. In the work, effects of polyethylene glycol, thiocarbamide, triethylene tetramine, polyvinylpyrrolidone corrosion inhibitor on the specific capacitance of high-voltage anode foil was investigated and the corrosion inhibitor behaviors of mixed inhibitor for aluminum foil were studied preliminarily by adding different composition mixed inhibitors. Relatively non-add corrosion inhibitor, weight loss of etched foil tended to the appropriate, density and distribution of pit became more uniform, therefore, the true surface and the specific capacitance of aluminum foils could further increased.Corrosion inhibitor absorbed on the surface of the aluminum foil through adsorption behavior, then, a protective layer was formed on surface of the aluminum foil, which could preferably prevent the aluminum foil and corrosive media contact and would take the part in corrosion inhibition behaviors. For compound corrosion inhibitor, it played the role in corrosion inhibition behaviors by synergy.