Liquid aluminum electrolytic capacitor with edge resistant to high-voltage breakdown and preparation method thereof

Abstract

The invention relates to the technical field of electronic components, in particular to a liquid aluminum electrolytic capacitor with edges resistant to high-voltage breakdown and a preparation method of the liquid aluminum electrolytic capacitor, and solves the problems that in the prior art, wet electrolytic paper is still electrically conducted with an aluminum shell and a cathode, and burrs and edges of an anode foil still discharge the electrolytic paper. The invention discloses a liquid-state aluminum electrolytic capacitor with edges resistant to high-voltage breakdown and a preparation method thereof. The liquid-state aluminum electrolytic capacitor comprises an anode foil, a cathode foil, a core bag formed by winding electrolytic paper, and an aluminum shell wrapping the core bag, the inner wall of the aluminum shell is coated with an insulating layer which is obtained by dissolving, mixing, coating and drying a specific mixture. By coating the insulating layer, the electric contact between the edge of the core cladding and the aluminum shell is effectively blocked, the high-voltage breakdown resistance of the capacitor is improved, the problem that burrs and edges of the positive electrode foil discharge to the aluminum shell is solved, and the reliability and the stability of the capacitor are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic components, and particularly to a liquid aluminum electrolytic capacitor with high-voltage breakdown resistance at the edge and a preparation method thereof. Background Art

[0002] With the continuous miniaturization of electronic products, higher requirements are put forward for the size and performance of capacitors. As one of the commonly used components in electronic products, the performance of aluminum electrolytic capacitors directly affects the stability and reliability of electronic products. However, in the prior art, during the aging production process of aluminum electrolytic capacitors, a phenomenon of positive foil short-circuit breakdown often occurs due to arcing between the anode foil of the core package and the bottom of the aluminum shell. Especially in small-sized capacitors, due to the decreasing margin of the foil paper and the decreasing gap between the core package and the top of the aluminum shell, this problem is particularly prominent.

[0003] To solve this problem, a design of adding cushion paper between the core package and the aluminum shell has been proposed in the prior art. By means of physical isolation, the core package is isolated from the aluminum shell, and the insulation between the core package and the aluminum shell of the capacitor is increased. However, this design has many disadvantages: First, the wet electrolytic paper still maintains electrical conduction with the aluminum shell and the cathode, and the burrs and edges of the positive electrode foil will still discharge to it; Second, the inserted electrolytic paper will affect the safety when the explosion-proof valve of the electrolytic capacitor is opened; Finally, the design of the cushion paper increases the manufacturing cost and complexity of the capacitor.

[0004] Therefore, there is an urgent need for a liquid aluminum electrolytic capacitor with high-voltage breakdown resistance at the edge and a preparation method thereof, which can effectively solve the problems existing in the prior art and improve the high-voltage breakdown resistance and reliability of the capacitor. Summary of the Invention

[0005] The purpose of the present invention is to provide a liquid aluminum electrolytic capacitor with high-voltage breakdown resistance at the edge and a preparation method thereof, which solves the problem that the wet electrolytic paper in the prior art still maintains electrical conduction with the aluminum shell and the cathode, and the burrs and edges of the positive electrode foil will still discharge to it.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A liquid aluminum electrolytic capacitor with high-voltage breakdown resistance at the edge and a preparation method thereof, comprising an anode foil, a cathode foil, a core package formed by winding electrolytic paper, and an aluminum shell wrapping the core package; an insulating layer formed by coating a layer of insulating glue on the inner wall of the aluminum shell, the insulating layer is obtained by dissolving, mixing, coating and drying a mixture containing polyvinyl butyral, nano-scale SiO2 powder, coupling agent, ethanol, ether and ethanolamine, and the thickness of the insulating layer is 0.02 - 0.1 mm; the insulating glue is prepared by aldol condensation reaction.

[0008] Preferably, the preparation method of the insulating glue comprises the following steps:

[0009] (a) Add polyvinyl butyral solid powder to ethanol in a certain proportion, and add ether at the same time to form a mixed solvent. Seal and stir for 4 to 6 hours until completely dissolved;

[0010] (b) Add 0.005 to 0.02% of nano-scale SiO2 powder to the coupling agent, and stir until evenly dispersed;

[0011] (c) Pour the liquid obtained in step (b) into the solution obtained in step (a), and stir again to form insulating glue;

[0012] (d) Adjust the pH value of the insulating glue to be slightly greater than 7, and achieve an alkaline environment by adding ethanolamine;

[0013] (e) Evenly apply the insulating glue on the inner wall of the aluminum shell, and dry it in an environment of 60 to 80 °C to volatilize the organic solvent and solidify to form an insulating layer.

[0014] Preferably, in step (a), the dissolution process is preferably carried out in a low-temperature circulating water bath environment, and the water bath temperature is lower than 2 °C to ensure the complete dissolution of polyvinyl butyral and the stability of the mixed solvent.

[0015] Preferably, the addition amount of the nano-scale SiO2 powder accounts for 0.005 to 0.02% of the mass of the coupling agent. The oxygen atoms in the SiO2 molecules form a Lewis acid-base bond with the aluminum oxide (Al2O3) on the surface oxide film of the aluminum shell, enhancing the bonding force and mechanical strength between the insulating layer and the aluminum shell.

[0016] Preferably, the thickness of the insulating layer is 0.02 to 0.1 mm. This thickness range not only ensures the insulation performance of the insulating layer but also avoids affecting the volume and assembly of the capacitor due to excessive thickness.

[0017] Preferably, the aluminum shell is a special aluminum shell for high-voltage capacitors. After coating the insulating glue, the explosion-proof pressure of the aluminum shell does not increase significantly, maintaining the original explosion-proof performance.

[0018] A preparation method of a liquid aluminum electrolytic capacitor with high-voltage breakdown resistance at the edge comprises the following steps:

[0019] A) Cut the anode foil, cathode foil and electrolytic paper into predetermined sizes;

[0020] B) Rivet the anode lead to the anode foil, rivet the cathode lead to the cathode foil, and wind the riveted anode foil, cathode foil and electrolytic paper into a core package;

[0021] C) Prepare insulating glue according to the insulating glue preparation method described in any one of claims 2 to 6;

[0022] D) Apply the insulating glue evenly on the inner wall of the aluminum shell and dry it in an environment of 60 - 80 °C to form an insulating layer;

[0023] E) Immerse the core package in the electrolyte for impregnation;

[0024] F) Put the impregnated core package into the aluminum shell coated with insulating glue, assemble and seal it;

[0025] G) Conduct sleeve, aging and electrical performance tests.

[0026] Preferably, the electrical performance test includes the voltage test between the positive electrode and the aluminum shell. When the power supply voltage is 450 V for the aluminum shell coated with insulating glue, the voltage between the positive electrode and the aluminum shell decreases significantly, indicating that the insulating layer effectively blocks the electrical contact and improves the high - voltage breakdown resistance of the capacitor. At the same time, conduct lightning strike test, explosion - proof test and reliability test to verify the comprehensive performance of the capacitor.

[0027] The present invention has at least the following beneficial effects:

[0028] By adopting the method of coating the inner wall of the aluminum shell with insulating glue, the present invention effectively solves the problem of short - circuit breakdown caused by arcing between the anode foil and the bottom of the aluminum shell in the prior art. The inner wall of the aluminum shell coated with insulating glue is equivalent to adding an insulating layer, so that the core package and the aluminum shell no longer directly contact, forming a certain insulating state. This not only effectively blocks the problems of breakdown caused by burrs in aluminum foil cutting, tip discharge or edge discharge between the edge of the aluminum foil and the top of the aluminum shell, but also greatly improves the surge voltage resistance of the compact electrolytic capacitor. Specific Embodiments

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0030] Embodiment 1

[0031] A liquid aluminum electrolytic capacitor with high - voltage breakdown resistance at the edge in this embodiment includes an anode foil, a cathode foil, a core package formed by winding electrolytic paper, and an aluminum shell wrapping the core package; an insulating layer formed by coating a layer of insulating glue is provided on the inner wall of the aluminum shell. The insulating layer is obtained by dissolving, mixing, coating and drying a mixture containing polyvinyl butyral, nano - sized SiO2 powder, coupling agent, ethanol, ether and ethanolamine, and the thickness of the insulating layer is 0.02 - 0.1 mm; the insulating glue is prepared by aldol condensation reaction.

[0032] By adopting the method of coating the inner wall of the aluminum shell with insulating glue, the problem of short - circuit breakdown caused by arcing between the anode foil and the bottom of the aluminum shell in the prior art is effectively solved. The inner wall of the aluminum shell after coating with insulating glue is equivalent to adding an insulating layer, so that the core package and the aluminum shell no longer directly contact, forming a certain insulating state. This not only effectively blocks the problem of breakdown caused by burrs in aluminum foil cutting, tip discharge or edge discharge between the edge of the aluminum foil and the top of the aluminum shell, but also greatly improves the surge - voltage resistance ability of the compact electrolytic capacitor.

[0033] At the same time, the insulating glue used in the present invention has good adhesion and a low curing temperature, has good light resistance, water resistance, heat resistance, cold resistance and film - forming property, and has no influence on the parameters and explosion - proof characteristics of the capacitor itself. The addition of nano - level SiO2 powder enhances the bonding force and mechanical strength between the insulating layer and the aluminum shell, and improves the durability of the capacitor.

[0034] In addition, the preparation method of the present invention is simple and easy to operate, with low cost, and is suitable for large - scale production. Through verification such as electrical performance testing, lightning strike testing, explosion - proof testing and reliability testing, the capacitor of the present invention has excellent high - voltage breakdown resistance ability, explosion - proof performance and reliability, meeting the high - performance requirements of electronic products for capacitors.

[0035] Example Two

[0036] For a liquid aluminum electrolytic capacitor with edge high - voltage breakdown resistance in this embodiment, the preparation method of the insulating glue includes the following steps:

[0037] (a) Add polyvinyl butyral solid powder to ethanol in a certain proportion, and at the same time add ether to form a mixed solvent, seal and stir for 4 - 6 hours until fully dissolved;

[0038] (b) Add 0.005 - 0.02% of nano - level SiO2 powder to the coupling agent, and stir until evenly dispersed;

[0039] (c) Pour the liquid obtained in step (b) into the solution obtained in step (a), and stir again to form insulating glue;

[0040] (d) Adjust the pH value of the insulating glue to be slightly greater than 7 to achieve an alkaline environment by adding ethanolamine;

[0041] (e) Evenly apply the insulating glue on the inner wall of the aluminum shell, and dry it in an environment of 60 - 80 °C to volatilize the organic solvent and cure to form an insulating layer.

[0042] In step (a), the dissolution process is preferably carried out in a low - temperature circulating water tank environment, and the water tank temperature is lower than 2 °C to ensure the full dissolution of polyvinyl butyral and the stability of the mixed solvent.

[0043] The addition amount of the nano-scale SiO2 powder accounts for 0.005-0.02% of the mass of the coupling agent. The oxygen atoms in the SiO2 molecules form Lewis acid-base bonds with the aluminum oxide (Al2O3) on the surface oxide film of the aluminum shell, enhancing the bonding force and mechanical strength between the insulating layer and the aluminum shell.

[0044] The thickness of the insulating layer is 0.02-0.1 mm. This thickness range not only ensures the insulation performance of the insulating layer but also avoids affecting the volume and assembly of the capacitor due to excessive thickness.

[0045] The aluminum shell is a special aluminum shell for high-voltage capacitors. After coating with insulating glue, the explosion-proof pressure of the aluminum shell does not increase significantly, maintaining the original explosion-proof performance.

[0046] 1. Aging effect confirmation:

[0047]

[0048] 2. Explosion-proof pressure test:

[0049] Test the aluminum shell of a certain shell number. The standard range of the explosion-proof pressure is 1.1-1.7 Mpa. The explosion-proof pressure of the aluminum shell coated with insulating glue does not increase significantly.

[0050] Classification Film thickness Explosion-proof pressure test Ordinary aluminum shell / 1.1 - 1.7 Mpa Aluminum shell with inner coating of insulating glue Approximately 0.02 - 0.1 mm 1.1 - 1.7 Mpa

[0051] 3. Product power-on test:

[0052]

[0053] 4. Explosion-proof test:

[0054] 100 finished products of aluminum shells coated with insulating glue are explosion-proof tested, and the situation is good without any abnormal valve-opening phenomena.

[0055] 5. Lightning strike test:

[0056] Assemble 50 RL 450V3913*20 capacitors each with an aluminum shell with internal paper padding and an aluminum shell coated with insulating glue respectively. The other component materials are exactly the same. Apply surge voltage to them through a lightning surge tester, with the starting voltage of 2000 V, the step voltage of 100 V, and each voltage is applied 20 times at an interval of 20 s. Record the voltage and number of times when the explosion-proof valve at the bottom of the capacitor bulges open. After the test, disassemble the capacitor and observe whether there are discharge blackening marks at the bottom inside the aluminum shell.

[0057]

[0058] 6. Reliability test:

[0059] The assembled aluminum shell coated with insulating glue for the RL 450V39 13*20 product was subjected to a reliability test at 105°C for 2000 hours, and the electrical characteristics were confirmed to be normal, meeting the design requirements.

[0060] Example 3

[0061] A method for preparing a liquid aluminum electrolytic capacitor with high-voltage breakdown resistance at the edge, comprising the following steps:

[0062] A) Cut the anode foil, cathode foil, and electrolytic paper into predetermined sizes;

[0063] B) Rivet the anode lead to the anode foil, rivet the cathode lead to the cathode foil, and wind the treated anode foil, cathode foil, and electrolytic paper into a core package;

[0064] C) Prepare the insulating glue according to the insulating glue preparation method described in any one of claims 2 to 6;

[0065] D) Evenly apply the insulating glue on the inner wall of the aluminum shell and dry it in an environment of 60 - 80°C to form an insulating layer;

[0066] E) Immerse the core package in the electrolyte for impregnation;

[0067] F) Place the impregnated core package into the aluminum shell coated with insulating glue, assemble and seal it;

[0068] G) Conduct sleeve, aging, and electrical performance tests.

[0069] The electrical performance test includes the voltage test between the positive electrode and the aluminum shell. When the power supply voltage is 450V for the aluminum shell coated with insulating glue, the voltage between the positive electrode and the aluminum shell is significantly reduced, indicating that the insulating layer effectively blocks the electrical contact and improves the high-voltage breakdown resistance of the capacitor; meanwhile, lightning strike tests, explosion-proof tests, and reliability tests are conducted to verify the comprehensive performance of the capacitor.

[0070] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance, characterized in that: include: A core package formed by winding anode foil, cathode foil and electrolytic paper, and an aluminum shell wrapping the core package; The inner wall of the aluminum shell is coated with an insulating layer formed by an insulating glue, which is obtained by dissolving, mixing, coating and drying a mixture of polyvinyl butyral, nano-scale SiO2 powder, a coupling agent, ethanol, ether and ethanolamine, and the thickness of the insulating layer is 0.02 to 0.1 mm; the insulating glue is prepared by an aldol condensation reaction.

2. The liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance according to claim 1, characterized in that: The preparation method of the insulating glue comprises the following steps: (a) adding polyvinyl butyral solid powder to ethanol in a certain proportion, and adding ether to form a mixed solvent, and stirring for 4 to 6 hours in a sealed state until fully dissolved; (b) adding 0.005-0.02% of nano-SiO2 powder to the coupling agent and stirring until it is evenly dispersed; (c) pouring the liquid obtained in step b) into the solution obtained in step a), stirring again to form an insulating glue; (d) adjusting the pH value of the insulating glue to slightly greater than 7, and achieving an alkaline environment by adding ethanolamine; (e) The insulating glue is evenly applied to the inner wall of the aluminum shell and dried at 60 to 80°C to evaporate the organic solvent and solidify to form an insulating layer.

3. The liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance according to claim 2, characterized in that: In the step (a), the dissolution process is preferably carried out in a low-temperature circulating water tank environment, and the water tank temperature is lower than 2° C. to ensure the full dissolution of polyvinyl butyral and the stability of the mixed solvent.

4. The liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance according to claim 1, characterized in that: The addition amount of the nano-scale SiO2 powder accounts for 0.005-0.02% of the coupling agent mass. The oxygen atoms in the SiO2 molecules form Lewis acid-base bonds with the aluminum oxide (Al2O3) of the aluminum shell surface oxide film, thereby enhancing the bonding force and mechanical strength between the insulating layer and the aluminum shell.

5. The liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance according to claim 1, characterized in that: The thickness of the insulating layer is 0.02-0.1 mm, and this thickness range not only ensures the insulating performance of the insulating layer, but also avoids affecting the volume and assembly of the capacitor due to excessive thickness.

6. The liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance according to claim 1, characterized in that: The aluminum shell is a special aluminum shell for high-voltage capacitors. After being coated with insulating glue, the explosion-proof pressure of the aluminum shell does not increase significantly, and the original explosion-proof performance is maintained.

7. A method for preparing a liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance, according to the liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance in claim 1, characterized in that: The following steps are involved: A) cutting the anode foil, cathode foil and electrolytic paper into predetermined sizes; B) nailing the anode guide pin to the anode foil, nailing the cathode guide pin to the cathode foil, and winding the nailed anode foil, cathode foil and electrolytic paper into a core package; C) preparing the insulating glue according to the insulating glue preparation method according to any one of claims 2 to 6; D) Apply the insulating glue evenly on the inner wall of the aluminum shell and dry it at 60-80℃ to form an insulating layer; E) immersing the core package in the electrolyte for impregnation; F) Pack the impregnated core into an aluminum shell coated with insulating glue and assemble and seal; G) Carry out bushing, aging and electrical performance tests.

8. The method for preparing a liquid aluminum electrolytic capacitor with edge high voltage breakdown resistance according to claim 7, characterized in that: The electrical performance test includes a voltage test between the positive electrode and the aluminum shell. When the power supply voltage of the aluminum shell coated with insulating glue is 450V, the voltage between the positive electrode and the aluminum shell is significantly reduced, indicating that the insulating layer effectively blocks the electrical contact and improves the high-voltage breakdown resistance of the capacitor. At the same time, lightning strike tests, explosion-proof tests and reliability tests are carried out to verify the comprehensive performance of the capacitor.

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