DD240031A1 - AL-ALLOYING FOR CATALYST FILM IN ELECTROLYTE CAPACITORS - Google Patents

Abstract

The invention relates to an Al (MgMnCu) alloy, from which films can be produced by known processes for use in electrolytic capacitors, which can be getted and stabilized by conventional etching and stabilization processes and at which stable specific surface capacitance values of more than 390 mF / cm2 can be achieved.

Description

Field of application of the invention

The invention is applicable to the production of cathode foil for electrolytic capacitors, which can be stabilized by known etching methods and by conventional stabilization methods.

Characteristic of the known technical solutions

The capacitance of an electrolytic capacitor is determined by the capacitance of both the cathode and the anode. It is known that the higher the predetermined anode capacitance, the more the total capacitance of an electrolytic capacitor increases as the cathode capacitance increases.

From this one can deduce the tendency for a constant increase of the cathode capacitance with the transition to higher anode capacities.

The reactive surface of the cathode foil which has been achieved by a predominantly electrochemical roughening in order to achieve a high specific area capacity must be coated after etching and cleaning by known stabilization methods with a layer which has the lowest possible dielectric effect. This layer must ensure a constant capacity of the cathode foil during storage in air as well as in the operating electrolyte.

The thickness of the roughening is dependent on the composition and the respective microstructure state of the smooth foil, which is processed into cathode foil, given etching electrolytes and process parameters.

Since a defect-free barrier layer is not required, in addition to aluminum of lower purity, such as Al99.2 to Al99.8, Al alloys can be used in which high capacitance values can be achieved with still sufficient technological properties. These include AICu alloys with Cu contents between 0.15 to 5.7% by weight (DE-OS 2 841 539) and with 0.03 to 0.5% Cu and beryllium and titanium additives (DE-OS 2,841,539). OS 3 011 819) and an AICuTiB alloy with 0.1 to 1.0% Cu (JP 57-126942). However, the stated capacitance values of these Al-Cu alloys do not exceed 300 μΡ / cm ² .

Also known is a group of cathode foils based on AIMn. These include in the first place a pure AIMn alloy (DE-AS 2,102,702), in which, however, can be achieved only by a special manufacturing process in the hard state capacitance values of 350 pF / Cm ² (DE-AS 2,255,309). Alloys are known with a content of 0.2 to 2% Mn and a Si content of 0.03 to 1.0% (JP 57-126910) and with a content of 0.1 to 1.5% Mn and a Mg content of 0.1 to 1.3% (JP 57-126938), wherein the Cu content is present in each unavoidable order of magnitude. Further, an alloy having 0.2 to 0.8% Mn, 0.1-0.8% Fe and 0.2 to 0.8% Cu is known (JP 59-259944). With an AIMnCu alloy of unknown composition, stable specific area capacitance values of more than 500 μΡ / cm ² can be achieved with a special, but economically very expensive production method (DE-PS 3 242 622).

An AINiCu alloy (JP 57-126941) achieves a maximum specific areal capacity of 300 mF / citi ² and an AlV alloy (JP 57-126937) 215 MF / cm ² .

Finally, a capacity of 350 μΡ / cm ² and in the hard state of 380 μΡ / αη ^{2 is} achieved by an AIMgSi alloy due to finely divided Cu, Mg and Si-containing precipitates in the soft state.

For all the listed capacity values, except for AIMnCu, produced using an economically unacceptable technology, the unstabilized immediate values were listed, but these decrease with the shelf life.

Object of the invention

The aim of the invention is an Al alloy for cathode foil with stable capacitance values when stored in air and in the operating electrolyte , which exceed those of known cathode foils , ie above 390 μΡ / ηη \ ² . These capacitance values are expected to be achievable in a wide range of microstructural conditions allowing for greater technological tolerances in smooth film production.

The roughening should be uniform and not too deep, so that an unetched middle bar is maintained to ensure adequate mechanical characteristics.

The processing of the alloy to film from 50 μπι to 20μηι thickness should not require much more expensive technology compared to the films previously produced in the semifinished products.

Explanation of the essence of the invention

The invention has for its object to produce an alloy from which a cathode foil for electrolytic capacitors with a specific surface area capacity of more than 390 μΡ / cm ² can be produced without a much more expensive technology. The film produced from the alloy should be roughenable by known etching and stabilized with conventional stabilization methods and at the same time have to be used for the further processing of the film

Electrolytic capacitors required mechanical properties are maintained. According to the invention, the object is achieved by an alloy consisting of 0.01-1.2 mass% Mg, <0.05-0.8 mass% Cu, 0-0.8 mass% Mn and the Residual to 100 wt .-% Al, wherein between the Cu and the Mn content, a dependency ratio is such that the Cu content in the range of <0.1-0.8 Ma .-%, when the Mn Content is between 0 and 0.1 mass% and that the content of Cu is in the range of 0.15-0.8 mass% when the Mn content is between 0.1 and 0.8 mass%. -% lies. The alloy can be processed by addition of <0.2 wt .-% Ti to mold or continuous casting. The hardening behavior during cold rolling is similar to that of AIMn, so that subsequent to the hot rolling process, cold rolling at 50 μm to 30 μm can take place without intermediate annealing. Surprisingly, it has been found that even at 30 to 60% lower electricity quantities per unit area (compared to AIMn alloys), the alloy according to the invention gives stable specific area capacitance values of more than 400 μΡ / cm ² with otherwise identical etching and stabilization conditions.

The achievable etching structure is very finely distributed in the hard state and coarser with a uniform distribution of precipitation in the soft state, but in all cases of a depth that prevents local breakthroughs. This provides the basis for the etching of 50 μπη to 20 μηι thick films with sufficient mechanical properties.

The high capacitance values are due to never Mg- and Cu-containing phases, which can be in the form of precipitates as well as in the absence and low Mn levels as single-phase separations, ie as Guinier-Preston zones.

It is essential that with the alloy according to the invention under the given conditions, a suitable etch structure on the films can be achieved without local pitting and an additional uniform surface erosion occur.

The alloy can be made on the basis of Al 99.5 to Al99.9.

embodiment

The following alloys were melted

Table 1:

Composition in wt% Alloy Mg Cu Mn Si Fe Ti

No. 1, 0.85 0.27 0.004 0.043 0.15 0.007

No. 2 0.44 0.28 0.005 0.040 0.16 0.010

No. 3 0.26 0.30 0.41 0.046 0.18 0.018

No. 4 1.00 0.04 0.06 0.17 0.30 <0.2

These alloys were manufactured in block casting. After homogenization annealing, the material was hot rolled and then rolled to 50 μηη without intermediate annealing. In the hard state and according to the heat treatments shown in Table 2, the sheets were pickled, then the sheets of Alloys Nos. 1 to 3 were etched in a neutral chloride-containing electrolyte by the DC method (GS) and stabilized with a chromate-based stabilizing method

 Alloy # 4 was etched in 4% hydrochloric acid with AC (WS).

Table 2: Results after etching and stabilization

Alloy Heat Treatment Q _Current Type C _Flex Bend Tensile Strength

As / μΡ / cm ² (according to Satma PL 2) Ν / 1Ό mm

60 30 23

33 22 20

60 28

30

number 1 hard rolling Soft annealing Cold hardening 20 15 15 GS GS GS 405 418 395 19> 30 28 No. 2 hard rolling Soft annealing Cold hardening 18 15 15 GS GS GS 407 435 429 21> 30 28 No. 3 hard rolling soft annealing 20 15 GS GS 400 405 20> 30 No. 4 soft annealing 28 WS 430 > 30

Claims (3)

Invention claim: 1. Al alloy for cathode foil in electrolytic capacitors, characterized in that the alloy comprises 0.01-1.2% by mass Mg, <0.0-0.8 wt% Cu, 0-0.8 wt% Mn and the balance to 100 wt% of Al, with a dependency ratio between the Cu and Mn contents that the Cu content is in the range of <0.05-0.8 mass% when the Mn content is between 0 and 0.1 mass% and that the Cu content is in the range of 0 , 15-0.8 mass% is when the Mn content is between 0.1 and 0.8 mass%. 2. Al alloy according to item 1, characterized in that the Ti content is <0.2 wt .-%. 3. Al alloy according to item 1 and 2, characterized in that the alloy can be made of both pure and pure aluminum.