Effect Of Electrodeposition Metal Elements On Anodic Aluminum Foil For Aluminum Electrolytic Capacitor And Its Mechanism

Aluminum electrolytic capacitors have the advantages of small size,low price and good performance,and are widely used in various electronic products.With the continuous development of the electronics industry,the performance requirements of modern electronic equipment for aluminum electrolytic capacitors have further increased.Anode aluminum foil is the core material of aluminum electrolytic capacitors,and its specific surface area is directly related to the performance of the entire aluminum electrolytic capacitor.DC etching method is one of the commonly used surface expansion methods of anode aluminum foil,which can increase the specific surface area of the anode aluminum foil to a large extent,but there are problems such as too many types of craft,many parallel tunnels,and complicated equipment.Therefore,it is necessary to further study the DC electrochemical etching process of high-purity aluminum foil to improve the etching effect of the anode aluminum foil;increase the etching driving force of the aluminum foil,reduce or even eliminate the dependence of the anode aluminum foil on the external DC power supply during the etching process,and realize the spontaneous etching of aluminum foil thereby improving etching equipment and reducing business costs.We first study the effects of etching processes such as pretreatment,pitting generating,and pitting expansion on the DC etching behavior of non-electrodeposited aluminum foil to obtain better DC electrochemical etching process parameters.Then,an appropriate amount of metal elements Zn and Cu are electrodeposited on the surface of the high-purity aluminum foil to guide the generation of pitting,improve the uniformity of the pitting distribution,and reduce the merged pitting phenomenon of aluminum foil in the DC etching process.Finally,further increase the electrodeposition time,so that the aluminum foil forms an appropriate amount of microbatteries,improve the etching driving force,completely get rid of the external power supply,and realize spontaneous etching.Scanning electron microscopy,energy spectrum analysis,metallographic microscope,polarization curve,AC impedance,weight reduction,Thickness reduction and other testing and characterization methods were used to study the effect of electrodeposition of Zn and Cu on the etching process of high purity aluminum foil,and analyze the mechanism of electrodeposition metal elements in the pitting of aluminum foil,optimize the anode aluminum foil etching process.The main research content and results are as follows:?1?Study on the DC etching process and mechanism of non-electrodeposited aluminum foilAfter high-purity aluminum foil was pretreated in 0.5 mol/L Na OH solution and75?1 mol/L HCl solution,etched in a electrolyte with a temperature of 75°C and a H₂SO₄concentration of 3.8 mol/L,and expanded pitting in the 1 mol/L HCl at75?,can obtain better etching effect,under this condition,the density of the tunnels is higher,the thickness reduction is lower,and the mechanical strength is better.?2?Study on DC etching process and mechanism of high purity aluminum foil with electrodeposited Zn and CuUsing our electrodeposition method,both Zn and Cu can be successfully deposited on the surface of aluminum foil;After electrodepositing Zn or Cu on the surface of aluminum foil,since the standard electrode potentials of Zn and Cu are greater than that of Al,the metal and Al deposited on the surface of the aluminum foil form a coupling system,so that the deposited metal can guide the tunnels generation and reduce aluminum foil corrosion resistance to make the tunnels more evenly distributed.At the same electrodeposition time of 5 s,comparing with two types of electrodepositions,the electrodeposited Cu improves the DC etching effect of aluminum foil more obviously.?3?Study on self-etching process and mechanism of high-purity aluminum foil electrodeposited with Zn and CuAfter electrodepositing Zn or Cu on the surface of high purity aluminum foil for10s,it can be spontaneously etching in electrolyte.Compared with electrodeposited Zn,electrodeposited Cu aluminum foil has a stronger promotion effect on the etching impetus,and the time required for tunnels expanding is shorter.Self-etching method of electrodeposited Cu aluminum foil has greater application value.After Cu is electrodeposited on the surface of the aluminum foil,a Cu-Al microbattery is formed,which generates a corrosion current and increases the free corrosion current of the aluminum foil;electrodeposited Cu on the aluminum foil surface destroys the integrity of the aluminum foil passivation film,increases the active site of the aluminum foil surface,and reduces etching resistance.Under the dual action of improving etching driving force and reducing etching resistance,aluminum foil can spontaneously etch in electrolyte.