Aluminum electrolytic capacitor and preparation method thereof

Abstract

The invention relates to the field of aluminum electrolytic capacitors, in particular to an aluminum electrolytic capacitor and a preparation method thereof, and the method comprises the steps: cutting a formed anode foil into an aluminum foil sheet with the required width; performing surface cutting and / or edge re-formation treatment on the aluminum foil; and preparing the aluminum electrolytic capacitor based on the re-formed aluminum foil. The preparation method can solve the problem that the oxidation film formed by repairing the cutting section and the edge through the electrolyte in the aging process after the formed foil and the laminated foil are cut is not better than the original oxidation film in voltage resistance and quality, reduces the breakdown probability of the cutting section and the edge of the aluminum electrolytic capacitor, reduces the leakage current concentration of the cutting section and the edge, reduces the gas production, and effectively prolongs the service life.

Description

Technical Field

[0001] The present invention relates to the field of aluminum electrolytic capacitors, and in particular to an aluminum electrolytic capacitor and a preparation method thereof. Background Art

[0002] Aluminum electrolytic capacitors are mainly made of anode foil and cathode foil wrapped with electrolytic paper, which are then impregnated with electrolyte and encapsulated in an aluminum shell. As a core material that affects the performance of aluminum electrolytic capacitors, the anode foil needs to be cut into the required width in advance according to the different sizes of aluminum electrolytic capacitors. The cut section will expose the base aluminum of the sandwich layer in the middle and damage the intact oxide film on the edge. The exposed cut section and the edge of the damaged oxide film, as well as the oxide film damage caused by the winding, assembly and other manufacturing processes, will be repaired by the electrolyte in the subsequent process of making the finished product for aging, and the oxide film will be regenerated on the section to cover. However, because the electrolyte has a certain flash voltage, the highest aging voltage used in the aging process is usually much lower than the original formation voltage of the anode foil. Therefore, the exposed cut section and the edge of the damaged oxide film, as well as the oxide film damage caused by the winding, assembly and other manufacturing processes, the oxide film formed by the electrolyte repair cannot reach the original formation voltage of the anode foil. The quality of the formed oxide film is also worse than the oxide film formed by the formation liquid, which makes the aluminum electrolytic capacitor prone to breakdown at the cut section or edge during the later use process. Moreover, because the formation voltage and formation quality of the oxide film on the cut section and edge of the chemical foil are worse than those on the surface of the chemical foil, the leakage current is concentrated on the cut section and edge during use, causing a large leakage current of the capacitor, resulting in increased heating of the capacitor and increased gas production, which greatly shortens the service life of the aluminum electrolytic capacitor. In particular, when cutting a laminated foil with a higher specific volume (which can be a sintered body formed by sintering a metal powder or alloy powder composition, or a sintered foil with a sintered body film formed by a sintered body on the surface of a substrate), the cutting edge is prone to the phenomenon of sintered powder being squeezed and broken, falling off and cracking. Although the oxide film is formed by electrolyte repair in the later aging process, the formation voltage and formation quality of the oxide film formed by electrolyte repair are far inferior to those formed by the formation liquid. Therefore, the laminated foil electrolytic capacitor using laminated foil as the anode foil has a slightly larger leakage current and is prone to breakdown at the cut section and edge.

[0003] Therefore, it is urgent to develop a method for preparing aluminum electrolytic capacitors to solve the problem that the voltage resistance and quality of the oxide film formed by the cut section and edge of the formed foil and the laminated foil after cutting are not as good as the original oxide film after the electrolyte repair in the aging process. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present invention provides an aluminum electrolytic capacitor and a preparation method thereof, which solves the problem that the voltage resistance and quality of the oxide film formed by the cut section and edge of the formed foil and the laminated foil after cutting and repaired by the electrolyte in the aging process are not as good as the original oxide film, effectively reduces the burrs generated by cutting, reduces the probability of breakdown of the cut section and edge of the aluminum electrolytic capacitor, reduces the concentration of leakage current in the cut section and edge, reduces gas production, and effectively prolongs the service life. At the same time, when the cut surface and edge of the aluminum foil are re-formed, it will also have a certain repair effect on the surface oxide film cracks generated by the aluminum foil during the manufacturing process, which helps to improve the product's voltage resistance and life performance.

[0005] To this end, the first aspect of the present invention provides a method for preparing an aluminum electrolytic capacitor, comprising:

[0006] Cutting the formed anode foil into aluminum foil sheets of required width;

[0007] Performing chemical re-processing on the cut surface and / or edge of the aluminum foil;

[0008] The aluminum electrolytic capacitor is prepared based on the aluminum foil after the re-formation treatment.

[0009] In order to solve the deficiencies in the prior art, the present invention adopts a method of forming the anode foil after cutting, that is, the anode foil after forming is cut into the required width according to the design requirements and then subjected to the forming treatment, so that the cut section and edge are repaired by the forming treatment, and the aluminum electrolytic capacitor is made after the forming voltage of the cut section and edge is close to or equal to the original oxide film forming voltage and the oxide film of good quality is formed. The aluminum electrolytic capacitor prepared by this method is not easy to be broken down at the cut section and edge of the aluminum foil, and the gas production and bulging are alleviated, and the service life is also effectively extended.

[0010] According to an embodiment of the present invention, the formation voltage a selected for the re-formation treatment of the cut surface and / or edge and the formation voltage b of the anode foil satisfy: a≤b.

[0011] According to an embodiment of the present invention, the formation voltage a selected for the re-formation treatment of the cut surface and / or edge and the formation voltage b of the anode foil satisfy: b-50V≤a≤b.

[0012] According to an embodiment of the present invention, the chemical conversion liquid used in the cutting surface and / or edge re-conversion treatment includes boric acid.

[0013] According to an embodiment of the present invention, the mass concentration of the boric acid is 1-10%, preferably 5-8%.

[0014] According to an embodiment of the present invention, the chemical conversion liquid used in the cutting surface and / or edge re-chemical conversion treatment optionally further includes an auxiliary solute, and the auxiliary solute includes at least one of borate, adipate, citric acid, citrate, and azelaic acid.

[0015] According to an embodiment of the present invention, the mass concentration of the auxiliary solute is 0.1-5%.

[0016] According to an embodiment of the present invention, the temperature of the cutting surface and / or edge re-forming treatment is 60-95°C, preferably 80-95°C.

[0017] According to an embodiment of the present invention, the current density in the cutting surface and / or edge re-forming process is 10-200 mA / cm 2 , preferably 50-100mA / cm 2 .

[0018] According to an embodiment of the present invention, the time for the re-construction treatment of the cutting surface and / or edge is 5-60 minutes.

[0019] A second aspect of the present invention provides an aluminum electrolytic capacitor, which is obtained by the preparation method described in the first aspect.

[0020] Therefore, the aluminum electrolytic capacitor has better voltage resistance and longer service life.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an example diagram of the cut cross section and edge breakdown location of the anode foil in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0024] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0025] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0026] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0027] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0028] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0029] According to an embodiment of the present invention, a first aspect of the present invention provides a method for preparing an aluminum electrolytic capacitor, comprising:

[0030] (1) Cut the formed anode foil into aluminum foil sheets of required width.

[0031] According to a specific embodiment of the present invention, the chemical formation method of the anode foil in this step is not particularly limited and does not affect the subsequent treatment of the anode foil. Specifically, the anode foil can be subjected to a conventional chemical formation method for re-chemical treatment.

[0032] According to a specific embodiment of the present invention, the type of anode foil is not particularly limited, including but not limited to conventional corrosion-chemical foil or novel laminated foil, which does not affect subsequent processing. The laminated foil is a sintered body formed by sintering a metal powder or alloy powder composition, or a sintered foil with a sintered body film made of a sintered body formed on the surface of a substrate.

[0033] (2) The cut surface and / or edge of the aluminum foil are subjected to chemical reprocessing.

[0034] According to a specific embodiment of the present invention, the cut surface and / or edge re-forming treatment is carried out under constant voltage conditions, and the formation voltage a selected for the cut surface and / or edge re-forming treatment and the formation voltage b of the anode foil satisfy: a≤b, preferably b-50V≤a≤b. For example, if the formation voltage b of the anode foil is 640V, then the formation voltage a selected for the cut surface and / or edge re-forming treatment should satisfy a≤640V, preferably 590V≤a≤640V. This avoids the problem that the withstand voltage of the oxide film formed by the electrolyte repair in the aging process cannot approach or reach the original formation voltage of the anode foil, and the quality of the oxide film is also worse than that of the oxide film formed by the formation liquid.

[0035] According to a specific embodiment of the present invention, the chemical conversion liquid used in the re-chemical conversion treatment of the cutting surface and / or edge includes boric acid, and its concentration is not particularly limited. Those skilled in the art can make a reasonable selection according to actual needs. As some specific examples, the mass concentration of boric acid in the chemical conversion liquid is 1-10%, preferably 5-8%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0036] According to a specific embodiment of the present invention, the chemical formation liquid optionally further includes an auxiliary solute, the type of which is not particularly limited, and those skilled in the art can make a reasonable selection according to actual needs. As some specific examples, the auxiliary solute includes but is not limited to borates, adipates, citric acid, citrate, and azelaic acid. Among them, borates include ammonium pentaborate, etc.; adipates include ammonium adipate, etc. The mass concentration of the auxiliary solute is 0.1-5%. As some specific examples, the mass concentration of the auxiliary solute is 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0037] According to a specific embodiment of the present invention, the temperature of the cutting surface and / or edge re-formation treatment is not particularly limited, and those skilled in the art can make a reasonable selection according to actual needs. As some specific examples, the temperature of the cutting surface and / or edge re-formation treatment is 60-95°C, preferably 80-95°C, for example 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc.

[0038] According to a specific embodiment of the present invention, the current density in the cutting surface and / or edge re-forming process is 10-200 mA / cm 2 ; preferably 50-100mA / cm 2 As some specific examples, the current density in the cutting surface and / or edge re-forming process is 10 mA / cm 2 , 20mA / cm 2 、30mA / cm 2 , 40mA / cm2 , 50mA / cm 2 、60mA / cm 2 , 70mA / cm 2 、80mA / cm 2 , 90mA / cm 2 , 100mA / cm 2 , 110mA / cm 2 , 120mA / cm 2 , 130mA / cm 2 , 140mA / cm 2 , 150mA / cm 2 , 160mA / cm 2 , 170mA / cm 2 , 180mA / cm 2 、190mA / cm 2 , 200mA / cm 2 wait.

[0039] According to a specific embodiment of the present invention, the time for the re-chemical treatment of the cutting surface and / or edge is 5-60 min. As some specific examples, the time for the re-chemical treatment of the cutting surface and / or edge is 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0040] (3) The aluminum electrolytic capacitor is prepared based on the aluminum foil after the re-formation treatment.

[0041] According to a specific embodiment of the present invention, the preparation method of the aluminum electrolytic capacitor in this step is not particularly limited, and a normal production process can be adopted, for example, the anode foil after the re-formation treatment is wound into a core package, and the core package is impregnated with electrolyte to make an aluminum electrolytic capacitor.

[0042] According to an embodiment of the present invention, a second aspect of the present invention provides an aluminum electrolytic capacitor obtained by the preparation method described in the first aspect.

[0043] Therefore, the aluminum electrolytic capacitor has better voltage resistance and longer service life.

[0044] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0045] Example 1

[0046] The method for preparing an aluminum electrolytic capacitor provided in this embodiment comprises the following steps:

[0047] After the 640VF ordinary traditional etched foil is cut into the required width, a 640V forming voltage is applied to the cut section and edge for re-forming treatment, and then it is wound into a core and impregnated with electrolyte according to the normal production process of aluminum electrolytic capacitors to make 450V 1000μF 35×50 aluminum electrolytic capacitors.

[0048] The specific operations of the re-chemical treatment are:

[0049] Place the integrated and cut 640VF foil disc into a 5% boric acid solution for constant voltage formation. The bath temperature is 85°C. The formation voltage is 640V, the current density is 100mA / cm 2 , formation time 20min.

[0050] Example 2

[0051] After the 640VF laminated foil is cut into the required width, a 640V forming voltage is applied to the cut section and edge for re-forming treatment (the re-forming treatment is the same as in Example 1), and then it is wound into a core and impregnated with electrolyte to produce a 450V, 1200μF 35×50 aluminum electrolytic capacitor according to the normal production process of aluminum electrolytic capacitors.

[0052] Comparative Example 1

[0053] After the same type of ordinary traditional corrosion-formed foil of 640VF is cut into the required width, the same supporting materials as in Example 1 are directly wound into a core, which is impregnated with the same electrolyte as in Example 1 and made into a 450V 1000μF 35×50 aluminum electrolytic capacitor according to the same normal production process of aluminum electrolytic capacitors.

[0054] Comparative Example 2

[0055] The same type of laminated foil of 640VF is cut into the required width, and the same supporting materials as in Example 2 are directly wound into a core, which is impregnated with the same electrolyte as in Example 2 and manufactured into a 450V1200μF 35×50 aluminum electrolytic capacitor according to the normal manufacturing process of aluminum electrolytic capacitors.

[0056] Test example:

[0057] 1. Withstand voltage test:

[0058] (1) Take 10 aluminum electrolytic capacitors obtained in Example 1 and Comparative Example 1 respectively to conduct a withstand voltage test. A 675V DC voltage is directly applied to each product to observe the valve opening of the product and disassemble and analyze the breakdown position of the breakdown product. The experimental results are shown in Table 1.

[0059] Table 1

[0060]

[0061] Among them, “ / ” means none.

[0062] The results show that the aluminum electrolytic capacitors in Example 1 prepared by the method of cutting the forming foil and then treating it opened the valve normally in the withstand voltage test, and the withstand voltage qualified rate was 100%; while in the withstand voltage test of the aluminum electrolytic capacitors in Comparative Example 1, which did not undergo the forming foil cutting and then treating it, 5 of them broke down, and the qualified rate was only 50%. After disassembly analysis, the breakdown sites were all the upper and lower cut section edges of the anode foil (see Figure 1 ), indicating that the pressure resistance and quality of the oxide film on the cut section of aluminum foil formed by the method of chemically treating the foil after cutting are better than those formed by direct electrolyte repair in the aging process.

[0063] (2) Ten aluminum electrolytic capacitors obtained in Example 2 and Comparative Example 2 were respectively subjected to a withstand voltage test. A 675V DC voltage was directly applied to each product to observe the valve opening of the product and disassemble and analyze the breakdown position of the breakdown product. The experimental results are shown in Table 2.

[0064] Table 2

[0065]

[0066] Among them, “ / ” means none.

[0067] The results show that: the aluminum electrolytic capacitors in Example 2 prepared by the method of cutting the laminated foil and then performing the chemical treatment all opened normally in the withstand voltage test, and the withstand voltage qualified rate was 100%; while in the withstand voltage test of the aluminum electrolytic capacitors in Comparative Example 2 where the laminated foil was not cut and then subjected to the chemical treatment, 6 capacitors were broken down, and the qualified rate was only 40%. After disassembly analysis, the breakdown sites were all the upper and lower cut section edges of the anode foil, indicating that the withstand voltage performance and quality of the oxide film on the cut section of the aluminum foil repaired by the method of cutting the formed foil and then performing the chemical treatment are better than those formed by direct electrolyte repair in the aging process.

[0068] 2. High temperature load life test:

[0069] (1) Four products (numbered as Example C1, C2, C3, C4; Comparative Example D1, D2, D3, D4) were taken from each of Example 1 and Comparative Example 1 to conduct a high temperature load life test. Each product was loaded with a ripple current of 2.5A / product and a certain DC voltage to ensure that the effective value of the loaded DC voltage plus the ripple voltage was equal to the rated voltage of 450V. The high temperature load life test was conducted at a high temperature of 105°C. The experimental results are shown in Table 3.

[0070] Table 3

[0071]

[0072] The results show that the initial leakage current of the aluminum electrolytic capacitors of Examples C1-C4 obtained by adopting the method of cutting the forming foil and then performing the forming treatment is smaller than that of the aluminum electrolytic capacitors of Comparative Examples D1-D4 which are not subjected to the forming treatment after cutting the forming foil, indicating that the quality of the oxide film on the cut section of the aluminum foil repaired by adopting the method of cutting the forming foil and then performing the forming treatment is better than the oxide film formed by directly repairing with the electrolyte in the aging process. In the high-temperature load life experiment at 105°C, the comparative example D2, which did not undergo the forming foil cutting and then forming treatment, had a breakdown on the cut section edge of the anode foil at 1100 hours, and the other three comparative examples D1, D3 and D4 aluminum electrolytic capacitors, which did not undergo the forming foil cutting and then forming treatment, had leakage at 1500 hours; the aluminum electrolytic capacitors of Examples C1-C4, which adopted the method of forming foil cutting and then forming treatment, all had normal appearance and no leakage at 2000 hours, and the parameters such as loss size, leakage current and bulging height obtained by testing were significantly better than those of the three comparative examples D1, D3 and D4 aluminum electrolytic capacitors, which did not undergo the forming foil cutting and then forming treatment, indicating that the method of forming foil cutting and then forming treatment can help the aluminum electrolytic capacitors effectively extend their life.

[0073] (2) Four products (numbered respectively as Example G1, G2, G3, G4; Comparative Example H1, H2, H3, H4) were taken from each of Example 2 and Comparative Example 2 to conduct a high temperature load life test. Each product was loaded with a ripple current of 2.7A / product and a certain DC voltage to ensure that the effective value of the loaded DC voltage plus the ripple voltage was equal to the rated voltage of 450V. The high temperature load life test was conducted at a high temperature of 105°C. The experimental results are shown in Table 4.

[0074] Table 4

[0075]

[0076] The results show that the initial leakage current of the aluminum electrolytic capacitors of Examples G1-G4 prepared by the method of forming after cutting the laminated foil is less than that of the aluminum electrolytic capacitors of Comparative Examples H1-H4 without forming after cutting the laminated foil, indicating that the quality of the oxide film formed by the forming after cutting the laminated foil is better than the oxide film formed by the direct electrolyte repair in the aging process. In the 105℃ high temperature load life test, the aluminum electrolytic capacitors of Comparative Examples H1-H4 without forming after cutting the laminated foil had leakage at 2000h; while the aluminum electrolytic capacitors of Examples G1-G4 prepared by the method of forming after cutting the laminated foil still maintained normal appearance without leakage at 3000h. The parameters such as loss size, leakage current and bulging height obtained by the test were significantly better than those of the aluminum electrolytic capacitors of Comparative Examples H1-H4 without forming after cutting the laminated foil, indicating that the forming after cutting the laminated foil can effectively extend the life performance of the aluminum electrolytic capacitors of laminated foil.

[0077] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0078] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing an aluminum electrolytic capacitor, characterized in that: include: Cutting the formed anode foil into aluminum foil sheets of required width; Performing a chemical reprocessing on the cut surface and / or edge of the aluminum foil; The aluminum electrolytic capacitor is prepared based on the aluminum foil after the re-formation treatment.

2. The preparation method according to claim 1, characterized in that: The formation voltage a selected for the re-formation treatment of the cut surface and / or edge and the formation voltage b of the anode foil satisfy the following: a≤b.

3. The preparation method according to claim 1, characterized in that: The formation voltage a selected for the re-formation treatment of the cut surface and / or edge and the formation voltage b of the anode foil satisfy the following conditions: b-50V≤a≤b.

4. The preparation method according to claim 1, characterized in that: The chemical conversion liquid used in the chemical conversion treatment of the cutting surface and / or edge includes boric acid; Optionally, the mass concentration of the boric acid is 1-10%, preferably 5-8%.

5. The preparation method according to claim 1, characterized in that: The chemical conversion liquid used in the re-chemical conversion treatment of the cutting surface and / or edge optionally further includes an auxiliary solute, and the auxiliary solute includes at least one of borate, adipate, citric acid, citrate, and azelaic acid.

6. The preparation method according to claim 5, characterized in that: The mass concentration of the auxiliary solute is 0.1-5%.

7. The preparation method according to claim 1, characterized in that: The temperature of the cutting surface and / or edge re-forming treatment is 60-95°C, preferably 80-95°C.

8. The preparation method according to claim 1, characterized in that: The current density during the re-construction of the cut surface and / or edge is 10-200 mA / cm 2 , preferably 50-100mA / cm 2 .

9. The preparation method according to claim 1, characterized in that: The time for the re-chemical treatment of the cutting surface and / or edge is 5-60 minutes.

10. An aluminum electrolytic capacitor, characterized in that: The aluminum electrolytic capacitor is obtained by the preparation method according to any one of claims 1 to 9.

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