SU905341A1 - Method for electrochemically etching aluminium foil - Google Patents

Description

This invention relates to the electrochemical treatment of metals, in particular to the etching of aluminum foil used in the manufacture of aluminum capacitors. At present, in industrial conditions, the process of aluminum foil etching occurs in a dynamic mode for etching. The aluminum foil, which has undergone pre-treatment (trimming, is continuously immersed in a bath filled with electrolyte. A positive potential from the power source is applied to the foil through the contact roller and a negative potential to the cathode. When an electric current passes from the cathode through the electrolyte to the foil, etching occurs foil. The etching current density is 0.5 A / cm, the electrolyte temperature is 70 ° C. The density of the current flowing through the foil from the contact roller to the place of immersion of the foil in the cathode region varies from 100 to 1 AO / mm At this current density, a large amount of heat is released, which is removed by the flow of cooling water supplied through the P1 nebulizers. However, in places where there is not enough water, the foil can recrystallize. gas bubbles in the reaction zone, which are relatively slowly reaching the surface, while partially closing the active centers in the reaction zone. As a result, the process is slow and lasts 1.5 minutes. In addition, the etching current is supplied to the foil through the contact rollers by means of a sliding contact, as a result of which, when an elevated etching current is applied, it is possible to burn the foil and break it. This process makes it impossible to reduce the etching time without deterioration of the 3E electrical and mechanical parameters of the etched foil. Thus, the existing technological scheme does not allow to intensify the etching process, to increase the efficiency of the etching process. Improving the performance of the etching process is an acute problem in the industry, since with the increasing production of aluminum oxide capacitors, there is a shortage of etched aluminum foil, i.e., the production of capacitors is directly dependent on the production of foil processing. Also known is the method of electrochemical etching of aluminum foil in which the foil is clamped stationary in a contact device and voltage is applied from the positive power source to the foil through a contact device, and the negative pole of the power source is connected to the cathode plates located near the surface of the processed foil. The foil is etched at a current density of 0.06-1, A / cm2 at. Etching time is 1-15 minutes. Due to the fact that the foil is clamped motionless in the contact device, the likelihood of burning and breaking the foil due to the sliding contact, which occurs when using contact rollers to supply the etching current to the foil 2, is eliminated. However, the proposed method has a long etching time. Reducing the etching time can be achieved by increasing the etching current density, but using this etching method cannot increase the current density, since as the current density increases, there is an intense evolution of gas in the treatment zone, which covers the active areas located on the surface of the foil. The process flow slows down. Metal is removed over the surface of the foil, which leads to a decrease in its mechanical strength. In addition, although the foil is clamped in a stationary contact device, the foil area being processed remains incompletely fixed, which can cause the foil to rupture, short circuit, irregularity of etching due to deviation of the processed foil section in the case of using flow electrolyte. Closest to the invention is a method for the electrochemical etching of aluminum foil in a flowable electrolyte when the foil is moved in the vertical direction. Since the process is carried out at a current density of 75-1.5 A / cm, there is no foil burn when it contacts the contact rollers. . However, if in a known method, in order to intensify the process, a current density of up to 10 A / cm is used, for example, for a low-voltage foil for capacitors on If 200, then a burn-through of the foil occurs. The purpose of the invention is to intensify the process. This goal is achieved by the fact that according to the method of electrochemical etching of aluminum foil in a flowable electrolyte when the foil is moved in the vertical direction, the foil section being processed is clamped stationary in a contact device with a current of 2-10 A / cm across the entire perimeter of the surface being processed. Due to the fact that the foil is clamped fixedly, sliding contact and burning of the foil at high current density are eliminated due to the fact that the current density passing through the contact surface unit decreases, and the possibility of breaking the foil is prevented. short circuit The flow-through electrolyte (feed rate 2–4 m / s) circulating between the foil clamped in the fixed contact device and the cathode plates carries away the gas and heat released into the reaction zone, which ensures stable electrical and mechanical parameters of the etched foil at the current density pickling 2-10 A / cm. Etching current density less than 2 A / cm does not provide a reduction in etching time. When the current density is higher. 10 A / cm, the good quality of the etched foil is not maintained in accordance with ULV 045. + 27 TU, due to the fact that the gas 59 and heat that is intensively released during the process of the grass will not be sufficiently carried away from the reaction zone by the flow electrolyte maximum permissible flow rate at which the foil does not tear. The use of high current densities in this method does not lead to aluminum etching, since the etching process proceeds very quickly (c), and the gas and heat released in the etching zone is carried away by the electrolyte flow. FIG. 1 shows a diagram of an etching method for aluminum foil, a general view; in fig. 2 - contact device. The aluminum foil 1 fed from the coil is clamped in a fixed contact device, for example, a contact frame 2 located in an etching bath 3, and a portion of the foil to be processed, clamped in a contact frame, is arranged parallel to the flow direction of the electrolyte, which the pump serves at a speed of 3, 3 m / s between the foil 1 and the cathode plates 5 located at the opposite surfaces of the processed foil. The voltage from the positive pole of the power source 6 is fed to the foil 1 via contact 2, and the negative pole of the power source 6 is connected to the cathode plates 5. The gas and heat released in the recovery zone is circulated between the foil 1 and cathode plates 5. Etching time, electrolyte temperature 70-92 ° C. After the etching process is completed, the voltage is turned off, the electrolyte supply is stopped. The electrolyte enters the electrolyte regeneration sump 7 (not shown), in which the electrolyte is turned and returns to the cycle. Then the contact frame 2 is depressed. The foil 1 is drawn from the etching zone to the next process step. and then the cycle repeats c. The foil 1 is clamped from both surfaces by the side edges (no more than 15 mm wide) by two pairs of contact devices 2. At the same time, the upper and lower edges of the area being processed are fixed in strips of electrically insulating material, which simultaneously serve to direct the flow of electrolyte. in a way. 16, the area to be treated is fixed around the perimeter. The contact device 2, which clamp the foil and supply current to the foil, includes a pair of copper anodic contacts 8, which are located on one side of the foil plane, are conductive and coated with an insulating material that protects it from etching, and a pair of contacts 9 made of titanium, which are not wires and which mechanically press the foil to the anode contacts. The pair of anode contacts 9 is movable and has a stroke of 3 mm so that when the clip is removed (at this time the voltage is turned off), the next section of the foil to be processed is pulled. The clamping of the contact device can be carried out using a hydraulic, pneumatic or mechanical device, which develops the necessary compressive force to ensure reliable contact between the anode contacts and the foil. In tab. 1 shows the composition of the electrolyte according to the proposed and well-known methods. In tab. 2 - mode and results of processing on the proposed and known methods. As can be seen from the table, in order to obtain a specific capacitance of 308 µF / dm, it will take time kk s (anode current density 7, C A / inch, full processing 5.5 A / min per inch) , although the process is continuous, i.e., 8.5 times more than would be required if the process according to the invention is to be carried out, where only 5 s is required to obtain a 600 µF / dt capacity. In addition, the invention makes it possible to replace a foil OO mm thick, used according to the current technology for anodes, with a foil 0.05 mm thick, since the same capacity can be obtained on it, which is obtained on a foil 0.08 mm thick. mm, which leads to a saving of foil by 39. Compared with the known method 2, where the process lasts 115 minutes, the invention reduces the etching time by 20 times, and compared with the existing technology by 2-5 times.

7EPR 8

The aluminum foil processed corresponds to UMO0 5.427 TU and can

according to the invention, in their own element. to be used in the production of mechanical and mechanical parameters of capacitors.

Sodium sulphate sour polyethylene glycol (PEG-35)

Table 1

15-20

Oh, It0.0.5

119053

Claims (3)

1.Zakgeim L.N. Electrolytic capacitors. Gosenergoizdat, 1963, p. 150 .. 2. UK Patent No., cl. with 7B, pub. 1970. 3. US patent number 331616, cl. publish 196. Phi2.