JP3770825B2 - Aluminum hard foil for electrolytic capacitors - Google Patents

Description

【００５０】

【００５１】

【００５２】
〔化成処理および静電容量の測定〕
アジピン酸アンモニウム水溶液中で２０Ｖの直流を印可して化成処理を施し、硼酸アンモニウム水溶液中で静電容量を測定した。
【００５３】
結果を表２に示す。表２中の静電容量の値は、試料番号１３の静電容量を１００として相対値（％）で表示した。
【００５４】
【表１】

【００５５】
【表２】

【００５６】
表２の結果から、組成並びにＦｅを含む金属間化合物の最大径が本発明範囲でしかも単体ＳｉおよびＳｉを含む金属間化合物の観察されない本発明に係る硬質箔（試料番号１〜６）は、静電容量の高いことが判る。一方、均質化処理条件および熱間圧延条件は本発明範囲であるが、組成が本発明範囲を外れる硬質箔（試料番号７〜１０）は、静電容量が低いことが判る。また、組成は本発明範囲でも熱間圧延条件が本発明範囲を外れる硬質箔（試料番号１１〜１３）は、Ｆｅを含む金属間化合物の最大径が本発明範囲を外れるかもしくは単体ＳｉおよびＳｉを含む金属間化合物の存在が観察されて静電容量が低いことが判る。
【００５７】
【発明の効果】
以上説明したように、本発明の電解コンデンサ用アルミニウム硬質箔は、数種の包晶系元素およびＮｉの含有量を特定範囲とし、Ｆｅを含む金属間化合物の最大径を規制し、単体ＳｉおよびＳｉを含む金属間化合物が実質的に存在しないようにするだけで高い静電容量の箔が得られ、経済的でしかもコンデンサを小型化できる効果を有する。
【００５８】
また、本発明の硬質箔を冷間圧延にて製造するための圧延素材としての薄板の製造方法は、数種の包晶系元素の含有量を特定範囲とし、均質化処理の温度条件と熱間圧延の最終直前パス（Ｆ２パス）および最終パス（Ｆ１パス）の温度条件を管理するだけであるから、生産工程を簡略化できる効果と静電容量の高い電解コンデンサ用アルミニウム硬質箔が得られる効果を有する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum hard foil for high capacitance after AC electrolytic etching electrolytic capacitor.
[0002]
[Prior art]
Aluminum can be easily expanded by piercing a large number of micropores by chemical or electrochemical etching, and when the anodized process called chemical conversion treatment is applied to the aluminum whose surface area has been expanded, Can be used.
[0003]
The electrochemical etching is roughly classified into direct current etching and alternating current etching. Usually, an aluminum foil for an aluminum electrolytic capacitor anode for low pressure or medium and low pressure is formed by using an alternating current etching method to form a micropore. Perforated into a capacitor foil with a high capacitance.
[0004]
By the way, the foil which can obtain a still higher electrostatic capacity is calculated | required from recent miniaturization inclination.
[0005]
In JP-A-5-5145, 15 elements such as Zn, Mn, Cu, Fe, Si, Ga, Pb, Mg, B, V, Ti, Zr, Ni, Cr, and P are controlled and high static. Techniques for obtaining electric capacity have been proposed.
[0006]
[Problems to be solved by the invention]
However, the aluminum alloy foil for electrolytic capacitors disclosed in the above publication has an excessive number of control elements, which hinders productivity.
[0007]
That is, an object of the present invention is to provide an aluminum hard foil for an electrolytic capacitor that has a small number of control elements and can provide a high capacitance.
[0008]
[Means for Solving the Problems]
As a result of various studies to achieve the above-mentioned object, the present inventors have specified a small amount of a trace element as a specific amount, specified the maximum diameter of an intermetallic compound containing Fe, and further, between a single Si or Si-containing metal It has been found that a hard foil substantially free of a compound can obtain a high capacitance by alternating current electrolytic etching.
[0009]
In addition, a thin plate for making this hard foil by cold rolling is a homogenizing treatment of a slab having a specific composition under specific conditions, and an intermetallic compound containing an Al-Fe compound and elemental Si or Si in the process of hot rolling. It was found that a hard foil having a high electrostatic capacity can be obtained by subsequent cold rolling when the precipitation of is restricted.
[0010]
The present invention has been completed based on these novel findings.
[0011]
That is, the aluminum hard foil for electrolytic capacitors according to the present invention has a Cu content of 5 to 20 ppm, a V + Cr + Ni + Zr content of 1 to 6 ppm, and a Ni + Zr content of 0.05 to 1.5 ppm, with the balance being Al and It is an inevitable impurity, the Al content is 99.98% or more of the foil mass, the maximum diameter of the intermetallic compound containing Fe is 20 nm (nanometer) or less, and between the Si containing Si and the Si containing Si The compound is observed substantially at 230,000 times and is not substantially detected.
[0012]
In the present invention, the total amount of V, Cr, Ni, and Zr is defined within a specific range as a small number of trace elements that have a strong influence on AC etching, and for both Ni and Zr that have particularly strong effects, the total amount of both is further determined. Hard foils that are defined within a specific range, regulate the size of intermetallic compounds containing Fe, and that do not substantially observe the intermetallic compounds containing simple Si and Si are etched pits by suppressing self-corrosion by AC etching. A foil having a high electrostatic capacity can be obtained.
[0013]
A preferable method for producing a thin plate as a material for cold rolling for forming the hard foil of the present invention by cold rolling is to heat a slab having the composition defined for the foil in the present invention to a temperature of 530 to 570 ° C. for 3 hours or more. After holding and homogenizing, when a hot-rolled sheet is obtained by hot rolling of a plurality of passes, a fire having a temperature of 385 ° C. or higher in the final pass F1 of this hot rolling and the pass F2 immediately before the final pass. the rolled sheet and fire-rolled sheet temperature two hundred and seventy-five to three hundred twenty ° C. final immediately preceding path F2, then after the temperature of 230 ° C. or less of the fire-rolled sheet by final path F1, shall be the thin cold rolled to a desired thickness.
[0014]
In the above method , a slab composition, slab homogenization treatment conditions, and hot-rolled sheet temperature conditions in hot rolling are defined as described above, thereby obtaining a thin sheet with an appropriate intermetallic compound precipitation state. By further cold rolling this thin plate to obtain a hard foil, a hard foil having a high electrostatic capacity can be obtained by AC etching.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Conventionally, aluminum foils for electrolytic capacitors that are generally used include elements such as Si, Fe, Cu, Zn, Ga, W, Co, Ni, Ti, and V in the process of smelting, refining, and melting aluminum. Is mixed as an impurity or added as a significant element, but the content of these elements can be adjusted by combining various grades of aluminum. The aluminum alloy foil finally obtained has various characteristics by adding and blending a specific element as a significant element after adjusting impurities.
[0016]
One of the characteristics of the aluminum hard foil for an electrolytic capacitor in the present invention is an alloy composition prepared by adjusting the impurity elements as described above and adding a significant element. In particular, the aluminum content of the hard foil in the present invention, that is, the aluminum purity, is 99.98% or more in consideration of the solubility of the foil during AC etching. However, the Cu content is specified as 5 to 20 ppm .
[0017]
Below, the reason for limitation is demonstrated about the structure of the hard foil of this invention.
<Al: 99.98% or more>
When the aluminum content, that is, the aluminum purity is less than the lower limit value, an excessive amount of Al—Fe-based and / or Al—Fe—Si-based intermetallic compounds is generated in the slab homogenization treatment and / or hot rolling. Since these intermetallic compounds have a potential difference with the aluminum alloy matrix, preferential dissolution of the matrix proceeds excessively around the intermetallic compounds during AC etching, and the etching pits collapse and the capacitance decreases.
[0018]
<Cu: 5 to 20 ppm>
Cu has the effect of suppressing the preferential dissolution around the compound by making the matrix surface potential noble and reducing the potential difference between the intermetallic compound and the matrix. When the Cu content is less than the lower limit, the above effects are small and the capacitance is low. Moreover, when Cu content exceeds an upper limit, excessive melt | dissolution of foil will arise and an electrostatic capacitance will fall. This decrease in capacity seems to be caused by the fact that the Al—Cu-based intermetallic compound is generated excessively, the preferential dissolution around the intermetallic compound proceeds excessively, and the etching pits drop off.
[0019]
<V + Cr + Ni + Zr: 1-6 ppm and Ni + Zr: 0.05-1.5 ppm>
High-purity aluminum ingots are produced by refining electrolytic primary ingots. For this purification, the three-layer electrolytic method and the crystal fractionation method are widely adopted, but the crystal fractionation method is a method that utilizes the phenomenon that when a molten aluminum is cooled, it begins to crystallize from a high purity aluminum primary crystal, and at low cost. It has become mainstream.
[0020]
Here, in this crystal fractionation method, peritectic elements such as V, Cr, Zr and the like are concentrated to purified aluminum contrary to the above phenomenon. In the present invention, peritectic elements such as V, Cr, and Zr and Ni are intentionally used as a trace alloy component rather than as impurities, so that the use of aluminum metal as a raw material by the crystal fractionation method is cost effective. Even more advantageous. For fine adjustment of the composition, a master alloy of each element is used as necessary.
[0021]
Regarding the contents of V, Cr, Ni, and Zr, the total amount of the four components V + Cr + Ni + Zr is set within the range of 1 to 6 ppm, and the total amount of Ni and Zr Ni + Zr is set within the range of 0.05 to 1.5 ppm. To do.
[0022]
For the formation of etching pits during AC etching, a better result can be obtained when these four elements are included together than when they are contained alone. This is because, in the homogenization treatment, in addition to precipitation of Al—Fe and / or Al—Fe—Si intermetallic compounds, it is complicated such as Al—Fe— (V, Cr, Ni, Zr) -X. Intermetallic compounds are deposited at the same time, and various potential differences exist between such a complex compound and the matrix. As a result, good etching pits can be formed by alternating current etching and high capacitance can be obtained. Seem.
[0023]
That is, the content of V, Cr, Ni and Zr is for obtaining a high capacitance, and if the amount is less than the lower limit, the above effect is small. If the upper limit is exceeded, the amount of self-corrosion of the matrix increases and etching pits are generated. It collapses and the capacitance decreases. Further, since Ni and Zr have particularly strong etching pit forming ability among the above four elements, the content of Ni + Zr is regulated to 0.05 to 1.5 ppm. If the amount is less than the lower limit, the amount of complex compounds produced is small and a high capacitance cannot be obtained. If the amount exceeds the upper limit, the amount of self-corrosion of the matrix increases, etching pits collapse, and the capacitance decreases.
[0024]
Elements such as Mo, Nb, Sc, Ta, Ti, and W exist as peritectic elements other than V, Cr, and Zr. However, these elements originally have a small content and have a great influence on the formation of etching pits. However, it is preferable to make each element less than 0.5 ppm each together with other inevitable impurities.
[0025]
<Maximum diameter of intermetallic compound containing Fe: 20 nm or less>
The potential of the intermetallic compound containing Fe is more noble than the matrix. When a hard foil containing such a compound is AC-etched, the periphery of this compound becomes the starting point of the etching pit. Therefore, it is preferable to make many exist finely, and the size of the intermetallic compound containing Fe is 20 nm or less at the maximum diameter. If there are those exceeding 20 nm, the number of fine compounds deposited decreases and the number of etching pits to be formed also decreases, so that a high capacitance cannot be obtained.
[0026]
<Substance Si and Si-containing intermetallic compounds are not substantially detected>
In the present invention, an intermetallic compound containing Si refers to an Al—Si based compound, and does not include an Al—Fe—Si based compound. Al-Si-based compounds and Al-Fe-Si-based compounds have different influences on etching pit formation in AC etching. This difference in influence seems to be caused by the difference in potential difference with respect to the matrix. According to the results of experiments conducted by the present inventors, simple intermetallic compounds containing Si and Si have obtained knowledge that pit collapses occur around them due to alternating current etching, even if they are slightly present, and the capacitance is reduced. Therefore, it was decided not to be detected substantially. In the detection, it was decided that when observed with a transmission microscope at a magnification of 230,000, it was not substantially detected that it was not observed.
[0027]
The aluminum hard foil for electrolytic capacitors of the present invention can be made, for example, as follows.
[0028]
A high-purity aluminum ingot purified by a purification method such as a crystal fractionation method or a three-layer electrolysis method is used, and if necessary, a return material, a mother alloy, etc. are used to adjust the alloy elements and melt. When melting, degassing is performed, and the slab is cast by semi-continuous casting after filtering the molten metal.
[0029]
After the obtained slab is chamfered, it is heated and held at a temperature of 530 to 570 ° C. for 3 hours or more to perform a homogenization treatment, thereby removing casting distortion, eliminating casting segregation, and presenting the maximum in the slab. Crystallized material of about 30 nm is dissolved. If necessary, as part of the homogenization treatment, further cold rolling is performed to pulverize the crystallized product so that the maximum size is 20 nm or less.
[0030]
In the homogenization treatment, an appropriate amount is deposited as an intermetallic compound of Al-Fe system and Al-Fe- (V, Cr, Ni, Zr) -X system (X is another metal). Thereby, an etching pit is positively formed also around the crystallized substance and the precipitate at the time of AC etching, and the electrostatic capacity is improved.
[0031]
The above-mentioned effects can be obtained by setting the holding time at the homogenization temperature to 3 hours or more. Holding for more than 20 hours is economically disadvantageous.
[0032]
If the homogenization treatment temperature is lower than the lower limit, an excess of compounds enters the temperature region where Al—Fe and Al—Fe— (V, Cr, Ni, Zr) —X intermetallic compounds are rapidly precipitated. Therefore, the periphery of the compound is excessively dissolved in AC etching, causing pit collapse and lowering the capacitance.
[0033]
When the homogenization temperature exceeds the upper limit value, the intermetallic compound is excessively dissolved to reduce the amount of the precipitated compound, and it is reprecipitated in each rolling pass of the next hot rolling, and participates in the formation of etching pits. The distribution of the compound becomes irregular and the capacitance is lowered. Also, the oxide film on the surface of the slab is formed thick, and the oxide film needs to be removed by alkali cleaning, resulting in a decrease in productivity.
[0034]
The slab after the homogenization treatment is hot-rolled. The slab may be reheated from the homogenization temperature to the hot rolling start temperature after cooling, or if it is not cooled, it is subjected to hot rolling as it is or heated to the hot rolling start temperature as necessary. May be performed.
[0035]
In hot rolling, a hot rolled sheet having a thickness of 3 to 10 mm is formed by a plurality of passes. Precipitation hardly proceeds because the slab temperature is high at the initial stage of hot rolling.
[0036]
As the hot rolling pass progresses, the volume per unit length of the slab decreases and the cooling effect of the rolling roll increases. Since precipitation starts with the temperature drop of the hot rolled sheet, the temperature of the hot rolled sheet is controlled particularly at the end of hot rolling, and the Al-Fe and Al-Fe- (V, Cr, Ni, Zr) -X series are controlled. This limits the excessive precipitation of intermetallic compounds.
[0037]
That is, the hot-rolled sheet temperature on the entrance side of the last pass F2 immediately before the final pass F1 is rolled at 385 ° C. or higher, and the hot-rolled sheet is rapidly cooled with the rolling roll of the last pass F2 and the temperature is 275 to 320. ℃. In the high temperature range of 385 ° C. or higher, excessive precipitation of the intermetallic compound can be suppressed in combination with strain release, and in the temperature range of 320 ° C. or lower, the intermetallic compound is difficult to precipitate because the temperature is low. Again, precipitation can be limited. In other words, the temperature range of 385 to 320 ° C. at which the intermetallic compound is likely to precipitate is rapidly cooled by the F2 pass rolling roll to suppress the precipitation.
[0038]
The reason why the lower limit of the hot-rolled plate temperature after the last pass F2 is 275 ° C. is as follows. That is, at a temperature of 275 ° C. or higher, it is possible to suppress the precipitation of intermetallic compounds containing simple Si and Si. That is, setting the outlet temperature of the last pass F2 immediately before to 275 to 320 ° C. limits the excessive precipitation of Al—Fe and Al—Fe— (V, Cr, Ni, Zr) —X intermetallic compounds. Moreover, it is for suppressing precipitation of the intermetallic compound containing simple substance Si and Si.
[0039]
The entrance temperature of the final pass F1 after the last pass F2 is defined by the exit temperature of the last pass F2. In the final pass F1, the F1 outlet temperature is set to 230 ° C. or lower by quenching with a rolling roll. In a low temperature range of 230 ° C. or lower, since the temperature is low, it becomes difficult for the intermetallic compound containing simple Si and Si to precipitate, and the precipitation can be limited. The rolling reduction of the last pass F2 and the final pass F1 is not particularly limited, but generally 30 to 80% is preferable.
[0040]
By hot rolling under the above conditions, the thickness of the hot-rolled sheet is set to 3 to 9 mm, and in the next step, it is formed into a thin sheet of the present invention having a desired thickness by cold rolling. The thickness of the thin plate may be arbitrarily determined in consideration of handling and the like, and is generally 0.2 to 0.6 mm.
[0041]
This thin plate is further cold-rolled to form an aluminum hard foil for electrolytic capacitors. The thickness of this hard foil is approximately 80 to 120 μm. In cold rolling to a hard foil, recrystallization is not performed between rolling passes. Heating at a low temperature lower than the recrystallization temperature between rolling passes is preferable because part of the strain is released and softens, so that the rolling reduction can be increased in the subsequent rolling pass. The hard foil rolled to the product thickness may be heated and held at a low temperature below the recrystallization temperature in order to make the rolling strain uniform last if necessary.
[0042]
【Example】
A refined aluminum ingot purified by the crystal fractionation method, a refined aluminum ingot purified by the three-layer electrolytic method, a return material and a mother alloy were used for melting.
[0043]
A 530 mm thick slab was cast from the resulting molten metal by a semi-continuous casting method. The composition of the slab is shown in Table 1. In Table 1, the underlined numerical values are outside the scope of the present invention. Although omitted in Table 1, for all slabs, Si: 40 to 50 ppm, Fe: 35 to 50 ppm, Cu: 7 to 15 ppm, Al purity: 99.98% or more, and other impurity elements are each It was 0.5 ppm or less.
[0044]
The slab was cut by 15 mm and then heated and held at a temperature of 560 ° C. for 10 hours as a homogenization treatment, and hot rolled from this temperature to obtain a hot rolled sheet having a thickness of 100 mm. At this time, the temperature of the hot rolled sheet was 470 ° C.
[0045]
Further, the hot rolling was continued, and rolling was performed while variously changing the inlet side temperature and the outlet side temperature of the last pass (F2 pass) and the final pass (F1 pass). The plate thickness on the F2 pass entry side was 25 mm, the plate thickness on the F2 pass exit side was 15 mm, and the plate thickness on the F1 pass exit side was 6 mm.
[0046]
The obtained hot-rolled plate was cooled to room temperature and then cold-rolled to obtain a thin plate sample having a thickness of 90 μm.
[0047]
About each obtained sample, the maximum diameter of the intermetallic compound containing Fe, the presence or absence of the intermetallic compound containing simple substance Si and Si, and the electrostatic capacitance were measured. The results are shown in Table 2. In Table 2, the underlined matters are outside the scope of the present invention.
[0048]
In addition, each said measurement was performed with the following method.
<Maximum diameter of intermetallic compound containing Fe, presence or absence of intermetallic compound containing simple Si and Si>
A field emission transmission electron microscope was used. As the observation location, 20 visual fields of each sample were randomly selected, and the magnification was 230,000 times. The compounds were identified by EDX (energy dispersive X-ray spectroscopy).
[0049]

[0050]

[0051]

[0052]
[Chemical conversion treatment and capacitance measurement]
Chemical conversion treatment was performed by applying a direct current of 20 V in an aqueous solution of ammonium adipate, and the capacitance was measured in an aqueous solution of ammonium borate.
[0053]
The results are shown in Table 2. The capacitance values in Table 2 were expressed as relative values (%), with the capacitance of sample number 13 being 100.
[0054]
[Table 1]

[0055]
[Table 2]

[0056]
From the results of Table 2, the hard foils (sample numbers 1 to 6) according to the present invention in which the composition and the maximum diameter of the intermetallic compound containing Fe are within the scope of the present invention and the intermetallic compound containing simple Si and Si are not observed, It can be seen that the capacitance is high. On the other hand, the homogenization treatment conditions and the hot rolling conditions are within the scope of the present invention, but it can be seen that hard foils (sample numbers 7 to 10) whose composition is outside the scope of the present invention have a low capacitance. In addition, the hard foils (sample numbers 11 to 13) whose composition is within the scope of the present invention and the hot rolling conditions deviate from the scope of the present invention are those in which the maximum diameter of the intermetallic compound containing Fe deviates from the scope of the present invention. It can be seen that the presence of an intermetallic compound containing is low and the capacitance is low.
[0057]
【The invention's effect】
As described above, the aluminum hard foil for an electrolytic capacitor of the present invention has a specific range of content of several peritectic elements and Ni, regulates the maximum diameter of an intermetallic compound containing Fe, and contains simple Si and A foil having a high capacitance can be obtained simply by making the intermetallic compound containing Si substantially absent, and it is economical and has the effect of miniaturizing the capacitor.
[0058]
In addition, the method for producing a thin plate as a rolling material for producing the hard foil of the present invention by cold rolling has a specific range of contents of several peritectic elements, temperature conditions and heat of homogenization treatment Since only the temperature conditions of the last pass (F2 pass) and the final pass (F1 pass) of the intermediate rolling are managed, the effect of simplifying the production process and an aluminum hard foil for electrolytic capacitors with high capacitance can be obtained. Has an effect.

Claims (1)

By weight, the following composition:
Cu: 5 to 20 ppm,
V + Cr + Ni + Zr: 1 to 6 ppm, where Ni + Zr: 0.05 to 1.5 ppm, and the balance: Al and unavoidable impurities, where Al: 99.98% or more of the foil mass, and the maximum diameter of the intermetallic compound containing Fe is An aluminum hard foil for an electrolytic capacitor, characterized in that it is 20 nm or less, and simple substance Si and an intermetallic compound containing Si are not substantially detected by observation at 230,000 times.