Solid state stacked aluminum electrolytic capacitor and method of manufacturing the same

Abstract

A solid-state multilayer aluminum electrolytic capacitor includes a core and a casing, with the core encapsulated within the casing using a molding compound. Each core comprises a positive electrode region and a negative electrode region. The positive electrode region includes an aluminum foil and an oxide film formed on the aluminum foil. The negative electrode region includes an aluminum foil, an oxide film formed on the aluminum foil, a water-blocking layer, a conductive polymer layer, and a negative electrode lead-out layer. The water-blocking layer is disposed on the surface of the oxide film in the negative electrode region, and the conductive polymer layer is formed on the water-blocking layer. The negative electrode lead-out layer is disposed on the conductive polymer layer. The water-blocking layer is formed by drying a water-blocking agent dispersion, and the water-blocking agent includes a compound containing at least one of long-chain alkyl, long-chain hydrocarbon, or perfluoroalkyl functional groups. In this invention, the water-blocking layer effectively protects the alumina film, isolates the alumina from water, and improves the product's high-temperature and high-humidity resistance, thereby ensuring the stability of the capacitor's performance. The solid-state multilayer aluminum electrolytic capacitor of this invention exhibits a small leakage current change rate after being subjected to 85°C / 85% load.

Description

Technical Field

[0001] This invention relates to a solid-state multilayer aluminum electrolytic capacitor, and more particularly to a solid-state multilayer aluminum electrolytic capacitor with stable performance. Background Technology

[0002] Solid-state multilayer aluminum electrolytic capacitors use a single piece as the basic unit. The positive electrode region of the single piece is an aluminum core layer, the dielectric layer is an aluminum oxide insulating layer, and the negative electrode includes a solid electrolyte polymer (first cathode) formed on the outer surface of the dielectric layer, and carbon and silver layers formed on the solid electrolyte (i.e., second and third cathodes). The positive electrode of the single piece is soldered to the positive lead terminal, and the negative electrode of the single piece is bonded to the negative lead terminal with metal paste to form a multilayer stack. The stack is then encapsulated with plastic sealant to form a solid-state multilayer high-resolution capacitor.

[0003] However, solid-state multilayer aluminum electrolytic capacitors are classified as MSL3 moisture-sensitive components, meaning they are highly sensitive to moisture. During high-temperature and high-humidity reliability verification, moisture intrusion often causes the leakage current of solid-state multilayer aluminum electrolytic capacitors to exceed the standard.

[0004] In high-temperature and high-humidity environments, the aluminum foil surface of solid-state multilayer aluminum electrolytic capacitors undergoes continuous water absorption and degradation, leading to a surge in leakage current. The degradation process is as follows:

[0005] Al2O3+3H2O→2Al(OH)3;Al2O3+H2O→2AlO(OH);

[0006] The dense oxide film gradually reacts into a loose and porous hydroxide, resulting in a significant decrease in insulation withstand voltage.

[0007] Furthermore, when solid-state multilayer aluminum electrolytic capacitors are subjected to rated voltage under high temperature and high humidity conditions, water ionizes, leading to a sharp increase in hydrogen ion concentration. This causes localized dissolution of the aluminum oxide, resulting in defects and a surge in capacitor leakage current. The degradation process is as follows:

[0008] H2O→H + +OH - Al2O3+H + →Al2O(OH) + Al₂O(OH) + +5H + =2Al 3 +2H2O;

[0009] Under high temperature and high humidity conditions, water ionizes into hydrogen ions, which disrupt the bonds in alumina, break the alumina skeleton, and significantly reduce the insulation withstand voltage. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a solid multilayer aluminum electrolytic capacitor and its preparation method.

[0011] To solve the above-mentioned technical problems, the present invention proposes the following technical solution: a solid-state multilayer aluminum electrolytic capacitor, comprising a core and a shell formed by multiple stacked monoliths, wherein the core is encapsulated in the shell by a molding compound; each monolith includes a positive electrode region and a negative electrode region; the positive electrode region includes an aluminum foil and an oxide film formed on the aluminum foil, the negative electrode region includes an aluminum foil, an oxide film formed on the aluminum foil, a water-blocking layer, a conductive polymer layer, and a negative electrode lead-out layer, wherein the water-blocking layer is disposed on the surface of the oxide film in the negative electrode region, the conductive polymer layer is formed on the water-blocking layer, and the negative electrode lead-out layer is disposed on the conductive polymer layer; the water-blocking layer is formed by drying a water-blocking agent dispersion, wherein the water-blocking agent includes a compound containing at least one of long-chain alkyl, long-chain hydrocarbon, or perfluoroalkyl functional groups.

[0012] Preferably, in the above-mentioned solid-state multilayer aluminum electrolytic capacitor, the water-blocking agent includes one or more of isopentane, dodecyl acrylate, hexadecane, perfluoroalkyl acrylate, perfluorohexylethyl acrylate, or perfluorohexylsilane.

[0013] Preferably, in the above-mentioned solid multilayer aluminum electrolytic capacitor, the solid content of the water-blocking agent dispersion is between 0.05% and 10%.

[0014] Preferably, in the above-mentioned solid multilayer aluminum electrolytic capacitor, the negative electrode region is immersed in the water-blocking agent dispersion for 2-300 seconds.

[0015] A method for preparing a solid-state multilayer aluminum electrolytic capacitor includes the following steps:

[0016] 1) Cut the aluminum foil, then apply a release adhesive to the aluminum foil to form a positive electrode area and a negative electrode area on the aluminum foil;

[0017] 2) Form the negative electrode region of the aluminum foil processed in step 1);

[0018] 3) Immerse the negative electrode region of the aluminum foil treated in step 2) in the water-blocking agent dispersion for 2-300s; after removal, dry to form a water-blocking layer in the negative electrode region; the water-blocking agent includes one or more of isopentane, dodecyl acrylate, hexadecane, perfluoroalkyl acrylate, perfluorohexyl ethyl acrylate or perfluorohexylsilane.

[0019] 4) Form a conductive polymer layer on the surface of the water-blocking layer after completing step 3);

[0020] 5) Coat the surface of the conductive polymer layer with a conductive carbon layer, and coat the carbon layer with a conductive silver layer to form a monolith;

[0021] 6) The positive electrode regions of multiple single-chip wafers are welded together by positive electrode welding blocks to form a core.

[0022] In the above-mentioned method for preparing solid multilayer aluminum electrolytic capacitors, preferably, the solid content of the water-blocking agent dispersion is between 0.05% and 10%.

[0023] In the above-described method for preparing a solid-state multilayer aluminum electrolytic capacitor, preferably, the method for forming the conductive polymer layer in step 4) includes the following steps:

[0024] ① Coat the surface of the water-blocking layer with a monomer dispersion and dry it;

[0025] ② Coating with an oxidizing agent; carrying out a polymerization reaction at a temperature of 30℃-80℃; forming a conductive polymer layer;

[0026] ③ Cleaning;

[0027] In the above-described method for preparing a solid-state multilayer aluminum electrolytic capacitor, preferably, the method for forming the conductive polymer layer in step 4) includes the following steps:

[0028] a) Coat the surface of the water-blocking layer with a conductive polymer dispersion;

[0029] b) After drying, a conductive polymer layer is formed.

[0030] Compared with existing technologies, the advantages of this invention are: the water-blocking layer effectively protects the alumina film, isolates the alumina from water, and improves the product's resistance to high temperature and humidity, thereby ensuring the stability of the capacitor's performance. The solid-state multilayer aluminum electrolytic capacitor of this invention exhibits a small leakage current change rate after being subjected to 85℃ / 85% load. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the solid-state multilayer aluminum electrolytic capacitor in Example 1.

[0032] Figure 2 This is a schematic diagram of the core structure in Example 1.

[0033] Legend

[0034] 1. Core; 11. Aluminum foil; 12. Oxide film; 13. Water-blocking layer; 14. High-molecular conductive polymer layer; 15. Conductive carbon layer; 16. Conductive silver layer; 17. Positive electrode welding block; 18. Separating adhesive; 2. Molding material; 3. Positive electrode lead-out terminal; 4. Negative electrode lead-out terminal. Detailed Implementation

[0035] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0036] It should be noted that when a component is described as being "fixed to, attached to, connected to or connected to" another component, it can be directly fixed to, attached to, connected to or connected to the other component, or it can be indirectly fixed to, attached to, connected to or connected to the other component through other intermediate connectors.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] Example 1

[0039] like Figure 1 The solid-state multilayer aluminum electrolytic capacitor shown includes a core formed by multiple monolithic sheets stacked together and a housing, with the core encapsulated within the housing by a molding compound. Figure 2 As shown, the single-electrode includes a positive electrode region and a negative electrode region. The positive electrode region includes an aluminum foil and an oxide film formed on the aluminum foil. The negative electrode region includes an aluminum foil, an oxide film formed on the aluminum foil, a water-blocking layer, a conductive polymer layer, and a negative electrode lead-out layer. The water-blocking layer is disposed on the surface of the oxide film in the negative electrode region. The conductive polymer layer is formed on the water-blocking layer, and the negative electrode lead-out layer is disposed on the conductive polymer layer. The water-blocking layer is formed by drying a water-blocking agent dispersion. In this embodiment, the negative electrode lead-out layer includes a conductive carbon layer and a conductive silver layer. The conductive carbon layer is disposed on the surface of the conductive polymer layer, and the conductive silver layer is disposed on the surface of the conductive carbon layer. In this embodiment, the positive electrode region is led out through a positive electrode lead-out terminal, and the negative electrode region is led out through a negative electrode lead-out terminal.

[0040] In this embodiment, the water-blocking agent is isopentane, which contains long-chain alkyl and / or hydrocarbon functional groups. Long-chain alkyl groups are non-polar substances that repel polar water. After being cured into a film on aluminum foil, the long-chain alkyl groups are tightly arranged and have extremely low surface energy, causing water droplets to shrink into spherical shapes and slide off without spreading.

[0041] Meanwhile, in this embodiment, isopentane has no unsaturated active bonds, no strong oxidizing / reducing properties, and does not chemically react with the polymer. The conductive polymer chains are stacked with π-π bonds, and isopentane fills the gaps, making the conductive polymer film denser and reducing the surface energy of the polymer, thus adding waterproof properties to the polymer.

[0042] In this embodiment, the dispersant in the isopentane dispersion can be one or more of n-hexane, petroleum ether, ethyl acetate, or butyl acetate. The solid content of isopentane in the dispersion is between 0.05% and 10%, preferably 1% to 5%.

[0043] This embodiment also provides a method for preparing a solid multilayer aluminum electrolytic capacitor, which includes the following steps:

[0044] 1) Cut the aluminum foil and then apply a release adhesive to the aluminum foil to form a positive electrode area and a negative electrode area on the aluminum foil.

[0045] 2) The negative electrode region of the aluminum foil treated in step 1) is formed to form a complete oxide film on the surface of the aluminum foil; the rated voltage of the anode foil is 3.6VF.

[0046] 3) Immerse the negative electrode region of the aluminum foil treated in step 2) in the water-blocking agent dispersion for 2-300s; after removal, dry to form a water-blocking layer in the negative electrode region; in this embodiment, the water-blocking agent is isopentane; the solid content of isopentane in the dispersion is between 0.05% and 10%.

[0047] 4) Form a conductive polymer layer on the surface of the water-blocking layer after completing step 3).

[0048] 5) Coat the surface of the conductive polymer layer with a conductive carbon layer, and coat the carbon layer with a conductive silver layer to form a monolith;

[0049] 6) The positive electrode regions of multiple single-chip wafers are welded together by positive electrode welding blocks to form a core.

[0050] In this embodiment, the conductive polymer is PEDOT. There are two methods for forming the conductive polymer layer in step 4). The first method includes the following steps:

[0051] ① Coat the surface of the water-blocking layer with an EDOT monomer dispersion and dry. The dispersant in the EDOT monomer dispersion can be one or more of anhydrous methanol, anhydrous ethanol, or anhydrous butanol.

[0052] ② Coating with an oxidizing agent; carrying out a polymerization reaction at a temperature of 30℃-80℃ for about 80 minutes; forming a conductive polymer layer; the oxidizing agent can be one or more of ferric p-toluenesulfonate, ammonium persulfate, sodium persulfate, ammonium sulfate, and ferric chloride; the solvent for the oxidizing agent includes one or more of pure water, ethanol, methanol, or n-butanol.

[0053] ③ Cleaning: Remove excess oxidant or residual EDOT monomer.

[0054] The second method includes the following steps:

[0055] a) Coat the surface of the water-blocking layer with a dispersion of PEDOT; the dispersant of the dispersion may be one or more of pure water, anhydrous methanol, anhydrous ethanol or anhydrous butanol.

[0056] b) After drying, a conductive polymer layer is formed.

[0057] In this embodiment, the water-blocking layer effectively protects the alumina film, isolating the alumina from water, thereby ensuring the stability of the capacitor product's performance. The solid-state multilayer aluminum electrolytic capacitor of this invention exhibits a small leakage current change rate after being subjected to 85℃ / 85% load.

[0058] Example 2

[0059] In this embodiment, the water-blocking agent is dodecyl acrylate; dodecyl acrylate contains long-chain alkyl and hydrocarbon groups. Dodecyl acrylate contains long-chain alkyl and long-chain hydrocarbon functional groups, which are non-polar substances and repel polar water. After being cured into a film on aluminum foil, the long-chain alkyl and hydrocarbon groups are closely arranged, resulting in extremely low surface energy. Water droplets shrink into spherical shapes and slide off without spreading.

[0060] The other parts of this embodiment are the same as those in Embodiment 1.

[0061] Example 3

[0062] In this embodiment, the water-blocking agent is hexadecane; similar to isopentane in Example 1, hexadecane contains long-chain alkyl groups. The other parts of this embodiment are the same as in Example 1.

[0063] Example 4

[0064] In this embodiment, the water-blocking agent is perfluoroalkyl acrylate. After the perfluoroalkyl acrylate is cured into a film on aluminum foil, the perfluorocarbon chains are arranged vertically and tightly outward, resulting in extremely low surface energy. Fluorine atoms encapsulate the outer layer of the molecules, forming a dense, inert, hydrophobic fluorocarbon barrier layer. Simultaneously, the perfluoroalkyl acrylate has no unsaturated active bonds, no strong oxidizing / reducing properties, and does not chemically react with the polymer. The conductive polymer chains are stacked with π-π bonds, and the perfluoroalkyl acrylate fills the gaps, making the conductive polymer film denser and reducing the polymerization surface energy, thus adding waterproof properties to the conductive polymer.

[0065] Example 5

[0066] In this embodiment, the water-blocking agent is perfluorohexyl ethyl acrylate; similar to the perfluoroalkyl acrylate in Example 4, perfluorohexyl ethyl acrylate contains a perfluoroalkyl group. The other parts of this embodiment are the same as in Example 4.

[0067] Example 6

[0068] In this embodiment, the water-blocking agent is perfluorohexylsilane; similar to the perfluoroalkyl acrylate in Example 4, perfluorohexylsilane contains a perfluoroalkyl group. The other parts of this embodiment are the same as in Example 4.

[0069] Comparative Example 1

[0070] In Comparative Example 1, no water-blocking layer was provided on the surface of the oxide film in the negative electrode region. The other parts of Comparative Example 1 were the same as those in Example 1 or Example 4.

[0071] The capacitors with a rated value of 2V and 330μF, made in Examples 1-6 and Comparative Example 1, were tested for their initial capacitance (CAP), initial loss (DF), initial equivalent series resistance (ESR), and initial leakage current (LC). After being subjected to 85℃ / 85% steady state for 500 hours and load for 500 hours, the capacitance (CAP), loss (DF), equivalent series resistance (ESR), and leakage current (LC) of the capacitors were tested.

[0072] Table 1 compares the steady-state performance of Examples 1-6 with Comparative Example 1 at 85℃ / 85% and Table 2 compares the load performance of Examples 1-6 with Comparative Example 1 at 85℃ / 85%.

[0073] Table 1: Comparison of steady-state performance at 85℃ / 85% between the examples and comparative examples

[0074]

[0075] As can be seen from Table 1, the leakage current change rate of the embodiment is smaller and the performance is more stable after 500 hours of steady state at 85℃ / 85%.

[0076] Table 2: Comparison of 85℃ / 85% load performance between the Example and Comparative Examples

[0077]

[0078] As can be seen from Table 2, the leakage current change rate of the embodiment is smaller and the performance is more stable after being subjected to 85℃ / 85% load.

[0079] As can be seen from Tables 1 and 2, the present invention significantly improves the high temperature and high humidity resistance of solid multilayer aluminum electrolytic capacitors and can effectively solve the problem of increased leakage current caused by water vapor intrusion during high temperature and high humidity processes.

Claims

1. A solid state stacked aluminum electrolytic capacitor characterized by: The device comprises a core and a shell formed by multiple stacked monoliths, the core being encapsulated within the shell using a molding compound; each monolith includes a positive electrode region and a negative electrode region; the positive electrode region includes an aluminum foil and an oxide film formed on the aluminum foil, the negative electrode region includes an aluminum foil, an oxide film formed on the aluminum foil, a water-blocking layer, a conductive polymer layer, and a negative electrode lead-out layer, the water-blocking layer being disposed on the surface of the oxide film in the negative electrode region, the conductive polymer layer being formed on the water-blocking layer, and the negative electrode lead-out layer being disposed on the conductive polymer layer; the water-blocking layer is formed by drying a water-blocking agent dispersion, the water-blocking agent comprising a compound containing at least one of long-chain alkyl, long-chain hydrocarbon, or perfluoroalkyl functional groups.

2. The solid-state stacked aluminum electrolytic capacitor of claim 1 wherein: The water-blocking agent includes one or more of isopentane, dodecyl acrylate, hexadecane, perfluoroalkyl acrylate, perfluorohexyl ethyl acrylate, or perfluorohexylsilane.

3. The solid-state stacked aluminum electrolytic capacitor of claim 1 wherein: The solid content of the water-blocking agent dispersion is between 0.05% and 10%.

4. The solid-state stacked aluminum electrolytic capacitor of claim 1 wherein: The negative electrode region is immersed in the water-blocking agent dispersion for 2-300 seconds.

5. A method for preparing a solid-state multilayer aluminum electrolytic capacitor, characterized in that, Includes the following steps: 1) Cut the aluminum foil, then apply a release adhesive to the aluminum foil to form a positive electrode area and a negative electrode area on the aluminum foil; 2) Form the negative electrode region of the aluminum foil processed in step 1); 3) Immerse the negative electrode region of the aluminum foil treated in step 2) in the water-blocking agent dispersion for 2-300s; after removal, dry to form a water-blocking layer in the negative electrode region; the water-blocking agent includes one or more of isopentane, dodecyl acrylate, hexadecane, perfluoroalkyl acrylate, perfluorohexyl ethyl acrylate or perfluorohexylsilane. 4) Form a conductive polymer layer on the surface of the water-blocking layer after completing step 3); 5) Coat the surface of the conductive polymer layer with a conductive carbon layer, and coat the carbon layer with a conductive silver layer to form a monolith; 6) The positive electrode regions of multiple single-chip wafers are welded together by positive electrode welding blocks to form a core.

6. The method for preparing a solid-state multilayer aluminum electrolytic capacitor according to claim 5, characterized in that: The solid content of the water-blocking agent dispersion is between 0.05% and 10%.

7. The method for preparing a solid-state multilayer aluminum electrolytic capacitor according to claim 5, characterized in that: The method for forming the conductive polymer layer in step 4) includes the following steps: ① Coat the surface of the water-blocking layer with a monomer dispersion and dry it; ② Coating with an oxidizing agent; carrying out a polymerization reaction at a temperature of 30℃-80℃; forming a conductive polymer layer; ③ Cleaning.

8. The method for preparing a solid-state multilayer aluminum electrolytic capacitor according to claim 5, characterized in that: The method for forming the conductive polymer layer in step 4) includes the following steps: a) Coat the surface of the water-blocking layer with a conductive polymer dispersion; b) After drying, a conductive polymer layer is formed.

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