Solid electrolytic tantalum capacitor for high temperature and high humidity environment and method of manufacturing

Abstract

The application discloses a kind of high-temperature high-humidity environment solid electrolyte tantalum capacitor and preparation method, including tantalum anode (1) and the medium layer (2) successively coated in tantalum anode (1) outside, solid electrolyte layer (3), graphite silver paste layer (4) and epoxy shell (7);Its characterized in that, the medium layer (2), solid electrolyte layer (3) or graphite silver paste layer (4) one layer, two layers or three layers outer coating moisture-proof layer (5). Increase moisture-proof layer, can completely isolate the water vapor invasion in external environment, greatly reduce the failure rate of tantalum capacitor in high-temperature high-humidity working environment, improve reliability.Can solve the application range of tantalum capacitor under high-temperature high-humidity environment, can maintain the excellent electrical performance of tantalum capacitor.

Description

Technical Field

[0001] This invention belongs to the technical field of tantalum capacitors, and particularly relates to a solid electrolyte tantalum capacitor for high temperature and high humidity environments and its preparation method. Background Technology

[0002] Tantalum capacitors are widely used in communications, aerospace, and other fields due to their small size, high capacitance, long lifespan, and excellent filtering effect. However, with the increasing environmental conditions of equipment in some fields, maintaining the excellent electrical performance of tantalum capacitors in high-temperature and high-humidity environments remains a technical challenge for tantalum capacitor manufacturers.

[0003] Currently used tantalum capacitors have a semi-sealed encapsulation structure, with epoxy resin as the encapsulation material. While this epoxy resin provides some protection against moisture in normal operating environments, prolonged use in high-temperature and high-humidity environments can cause it to degrade or break down, allowing moisture to enter the capacitor. Since tantalum capacitors have a humidity sensitivity rating of 3, they are easily affected by ambient humidity. When moisture enters the capacitor, it adheres to weak points in the dielectric layer, forming conductive paths and significantly reducing the insulation performance of the dielectric layer. During operation, this results in a decline in the capacitor's electrical performance, and in severe cases, may lead to explosion or combustion.

[0004] Therefore, tantalum capacitors that are suitable for high temperature and high humidity environments and maintain excellent electrical performance are currently in high demand. Summary of the Invention

[0005] The purpose of this invention is to provide a solid electrolyte tantalum capacitor for high temperature and high humidity environments and its preparation method. The invention adds a moisture-proof layer, which can expand the application range of tantalum capacitors in high temperature and high humidity environments and maintain the excellent electrical performance of tantalum capacitors.

[0006] The technical solution provided by this invention is as follows:

[0007] A solid electrolyte tantalum capacitor for high temperature and high humidity environments includes a tantalum anode 1 and a dielectric layer 2, a solid electrolyte layer 3, a graphite silver paste layer 4, and an epoxy shell 7 sequentially covering the tantalum anode 1; the dielectric layer 2, the solid electrolyte layer 3, or the graphite silver paste layer 4 are covered with one, two, or three layers of a moisture-proof layer 5.

[0008] The moisture-proof layer 5 material includes one or more of polyacrylate, polyurethane and polyvinylsiloxane in any proportion.

[0009] The moisture-proof layer 5 has a thickness of 0.0001mm to 0.01mm.

[0010] A method for preparing a solid electrolyte tantalum capacitor for high temperature and high humidity environments includes: preparing a tantalum anode 1; coating the tantalum anode 1 with a dielectric layer 2; coating the dielectric layer 2 with a solid electrolyte layer 3; coating the solid electrolyte layer 3 with a graphite silver paste layer 4; coating the graphite silver paste layer 4 with an epoxy shell 7; and further coating one, two, or three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 with a moisture-proof layer 5.

[0011] The moisture-proof coating 5 includes coating by one or more combinations of coating processes such as sputtering, impregnation or deposition.

[0012] The deposition coating process includes vacuum coating, coating time of 30s to 5min, vacuum degree of 1.0 to 5.0Pa, heat treatment temperature of 100℃ to 200℃, to generate a moisture-proof layer 5 with a thickness of 0.0001mm to 0.01mm.

[0013] The moisture-proof layer 5 material includes one or more of polyacrylate, polyurethane and polyvinylsiloxane in any proportion.

[0014] As can be seen from the technical solutions provided by the present invention above, the solid electrolyte tantalum capacitor and its preparation method for high-temperature and high-humidity environments provided by the embodiments of the present invention add a moisture-proof layer, which can completely isolate the intrusion of water vapor in the external environment, significantly reduce the failure rate of tantalum capacitors used in high-temperature and high-humidity working environments, and improve reliability. It can solve the application range of tantalum capacitors in high-temperature and high-humidity environments and maintain the excellent electrical performance of tantalum capacitors. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a solid electrolyte tantalum capacitor for high temperature and high humidity environments according to Embodiment 1 of the present invention;

[0017] Figure 2 This is a schematic flowchart of the solid electrolyte tantalum capacitor for high temperature and high humidity environments and its preparation method according to Embodiment 2 of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0019] First, the following explanations are provided for the terms that may be used in this article:

[0020] The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0021] The terms “including,” “comprising,” “containing,” “having,” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, “including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.)” should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0022] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0023] The term "parts by mass" indicates the mass ratio between multiple components. For example, if component X is described as x parts by mass and component Y as y parts by mass, then the mass ratio of component X to component Y is x:y. One part by mass can represent any mass; for example, one part by mass can be expressed as 1 kg or 3.1415926 kg, etc. The sum of the parts by mass of all components is not necessarily 100 parts; it can be greater than 100 parts, less than 100 parts, or equal to 100 parts. Unless otherwise stated, parts, proportions, and percentages mentioned herein are all measured by mass.

[0024] Unless otherwise explicitly specified or limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this document according to the specific circumstances.

[0025] When concentration, temperature, pressure, size, or other parameters are expressed as numerical ranges, such ranges should be understood to specifically disclose all ranges formed by any pairing of upper limits, lower limits, or preferred values ​​within that range, regardless of whether the range is explicitly stated; for example, if the numerical range "2 to 8" is stated, then that range should be interpreted to include ranges such as "2 to 7", "2 to 6", "5 to 7", "3 to 4 and 6 to 7", "3 to 5 and 7", "2 and 5 to 7", etc. Unless otherwise stated, the numerical ranges described herein include both their endpoints and all integers and fractions within that range.

[0026] The terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” and “counterclockwise” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience and simplification of description and do not imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this document.

[0027] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0028] Example 1

[0029] like Figure 1 As shown, a solid electrolyte tantalum capacitor for high-temperature and high-humidity environments includes a tantalum anode 1 and, sequentially, a dielectric layer 2, a solid electrolyte layer 3, a graphite silver paste layer 4, and an epoxy shell 7, all of which are sequentially wrapped around the tantalum anode 1. The tantalum anode 1 is also connected to an anode lead 6, and the graphite silver paste layer 4 is connected to a cathode lead 8. The materials and preparation of the dielectric layer 2, solid electrolyte layer 3, graphite silver paste layer 4, and epoxy shell 7 can be any of the known and existing technologies, and will not be elaborated further. Alternatively, the method described in Embodiment 2 can also be used, all of which are within the scope of protection of this patent.

[0030] In this example, one, two, or three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 are covered with a moisture-proof layer 5. That is, one of the three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 can be covered with a moisture-proof layer 5; two of the three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 can be covered with a moisture-proof layer 5; or all three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 can be covered with a moisture-proof layer 5.

[0031] Here, the moisture-proof layer 5 material includes one or more of polyacrylate, polyurethane, and polyvinylsiloxane in any proportion. The thickness of the moisture-proof layer 5 is 0.0001 mm to 0.01 mm.

[0032] Example 2

[0033] refer to Figure 1 and 2 As shown, a method for preparing a solid electrolyte tantalum capacitor for high temperature and high humidity environments includes: preparing a tantalum anode 1; coating the tantalum anode 1 with a dielectric layer 2; coating the dielectric layer 2 with a solid electrolyte layer 3; coating the solid electrolyte layer 3 with a graphite silver paste layer 4; and coating the graphite silver paste layer 4 with an epoxy shell 7.

[0034] The above-described process is a well-known technical solution. Specifically, in this example, it could be:

[0035] The preparation process of tantalum anode 1 includes using tantalum powder with a specific volume of 5000μF*V / g to 100000μF*V / g and parameters between 5.0g / cm3 and 8.0g / cm3, pressing it into tantalum blocks with a suitable pressing density, and sintering the tantalum blocks into tantalum anode blocks with a certain mechanical strength at a heating rate of 20℃ / min to 100℃ / min and a temperature range of 1500℃ to 1800℃, which are used as block-shaped tantalum anode 1.

[0036] The process of coating the tantalum anode 1 with the dielectric layer 2 includes: the tantalum anode 1 is placed in an anodizing solution containing acid (phosphoric acid or nitric acid) with a solution mass ratio of 0.01wt% to 1wt%, and an electric current is applied to form a dielectric layer 2 of a certain thickness.

[0037] The process of coating the dielectric layer 2 with the solid electrolyte layer 3 includes: impregnating the dielectric layer 2 with manganese nitrate solution 5 to 10 times, and generating a manganese dioxide cathode layer, which is the solid electrolyte layer 3, at a thermal decomposition temperature of 230℃ to 250℃.

[0038] The process of coating the solid electrolyte layer 3 with the graphite silver paste layer 4 includes: the solid electrolyte layer 3 is provided with a graphite and silver cathode lead-out coating, which is the graphite silver paste layer 4;

[0039] The process of coating the graphite silver paste layer 4 with an epoxy shell 7 includes: coating the graphite silver paste layer 4 with an epoxy resin shell, namely the epoxy shell 7, by molding.

[0040] In addition, the tantalum anode 1 is also connected to the anode lead 6, and the graphite silver paste layer 4 is connected to the cathode lead 8. The anode lead 6 and the cathode lead 8 form a lead frame, and the tantalum core with anode and cathode layers is assembled in the lead frame by bonding it with conductive silver paste.

[0041] In this example, one, two, or three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 are covered with a moisture-proof layer 5; that is, one of the three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 can be covered with a moisture-proof layer 5; two of the three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 can be covered with a moisture-proof layer 5; or all three layers of the dielectric layer 2, solid electrolyte layer 3, or graphite silver paste layer 4 can be covered with a moisture-proof layer 5.

[0042] The moisture-proof coating 5 includes coating by one or more combinations of coating processes such as sputtering, impregnation or deposition.

[0043] Specifically, in this example, the deposition coating process includes vacuum coating, with a coating time of 30 seconds to 5 minutes, a vacuum degree of 1.0 to 5.0 Pa, and a heat treatment temperature of 100°C to 200°C, to generate a moisture-proof layer 5 with a thickness of 0.0001 mm to 0.01 mm. The coating material, i.e., the moisture-proof layer 5 material, includes one or more of polyacrylate, polyurethane, and polyvinylsiloxane in any proportion.

[0044] Example 3

[0045] This embodiment provides a method for fabricating a solid electrolyte tantalum capacitor for high-temperature and high-humidity environments. An example solid electrolyte tantalum capacitor for high-temperature and high-humidity environments is a 50V 10uF capacitor, and its structure is as follows. Figure 1 As shown, its manufacturing method is referenced. Figure 2 The steps are as follows:

[0046] (1) Preparation of tantalum anode 1: tantalum powder with a specific volume of 10000 uF.V / g is used. The anode blank with tantalum wire leads is pressed into a size of 4.5×3.50×3.30mm and a density of 7.5g / cm3. The pressed anode blank is sintered in a high temperature vacuum at 1750℃ for 30min. After sintering, it is passivated when it is taken out of the furnace to ensure that the tantalum wire on the blank is folded no less than 4 times and that the oxidation of the tantalum block and the tantalum wire is within an acceptable range. The tantalum block is the porous tantalum anode 1, and the tantalum wire is the anode lead 6 connected to the tantalum anode 1.

[0047] (2) The tantalum anode 1 is coated with a dielectric layer 2. The sintered tantalum anode 1 is spot-welded to a stainless steel strip and placed in a forming tank containing a phosphate-ethylene glycol electrolyte with a temperature of 85°C and a resistivity of 800-1500 Ω·cm (the concentration of phosphate in the electrolyte is 0.1% by volume and the concentration of ethylene glycol is 50% by volume). The dielectric layer 2 is formed by electrochemical formation at a forming voltage of 180V and a current density of 40mA / g.

[0048] (3) The solid electrolyte layer 3 is coated on the dielectric layer 2 by thermal decomposition of manganese nitrate solution of different concentrations, so that a manganese dioxide (MnO2) solid electrolyte layer 3 (i.e., the cathode of the tantalum capacitor) is generated on the surface of the dielectric layer 2 coated on the tantalum anode 1. The main process is as follows: the tantalum anode 1 coated on the dielectric layer 2 is immersed in manganese nitrate solution, and then thermally decomposed at a temperature of 250°C and a humidity of 5%RH-13%RH. The above process is repeated 10 to 12 times, and finally a manganese dioxide cathode of a certain thickness is formed on the dielectric layer 2, which is the solid electrolyte layer 3; the thickness of the solid electrolyte layer 3 is generally 0.1 mm to 0.3 mm.

[0049] (4) The solid electrolyte layer 3 is coated with a graphite silver paste layer 4. The tantalum anode 1, which is the tantalum anode 1 after the dielectric layer 2 and the solid electrolyte layer 3 are coated, is immersed in the hydrolyzed coupling agent solution for 10 min-2 h (the immersion process should not be submerged to ensure that the solvent can enter the tantalum porous body). Then, it is dried at 125°C for 10 min.

[0050] The tantalum block is then immersed in an oily graphite solution and a silver paste solution in sequence. After immersion, it is dried at 160℃ for 30 minutes to finally form a graphite layer and a silver paste layer, namely the graphite-silver paste layer 4. The main function of the graphite-silver paste layer 4 is to lead out the cathode lead 8.

[0051] (5) The graphite silver paste layer 4 is covered with a moisture-proof layer 5. The tantalum anode 1, which is covered with the dielectric layer 2, the solid electrolyte layer 3 and the graphite silver paste layer 4, is heat-treated at 100℃ / 30min. The heat-treated tantalum body and the moisture-proof material are placed in a vacuum coating furnace with a vacuum degree of 2.8Pa and kept for 30s to generate a moisture-proof layer that covers the entire tantalum core.

[0052] The moisture-proof material is made of one or more of polyacrylate, polyurethane and polyvinylsiloxane in any proportion.

[0053] (6) The epoxy shell 7 is encapsulated by using polymer conductive silver paste to connect the tantalum body covering the moisture-proof layer 5 to the lead frame. The assembled body is then encapsulated with an epoxy resin layer by molding to form the epoxy shell 7. The finished product has external dimensions of 7.3mm × 4.3mm × 4.1mm, and is then processed through printing, edge trimming, aging and screening to form a complete finished product.

[0054] The finished product was placed in an environment of 85℃ / 85%RH, and the electrical performance parameters were tested before and after the placement. The electrical performance parameters were tested at 500h, 1000h, and 1500h, respectively, and the results of the electrical performance parameters did not change.

[0055] The circuit connection of the high-temperature and high-humidity environment solid electrolyte tantalum capacitor of the present invention is the same as that of existing tantalum capacitors. The difference is that the high-temperature and high-humidity environment solid electrolyte tantalum capacitor is equipped with a moisture-proof layer inside, which covers the entire tantalum core and completely isolates it from the intrusion of external moisture. This avoids the degradation of the electrical performance of the tantalum capacitor due to moisture. Moreover, it still maintains excellent electrical performance in a high-temperature and high-humidity environment of 85℃ / 85RH%, which solves the problem of short circuit caused by the tantalum capacitor being easily affected by moisture, extends the service life of the capacitor, and greatly improves reliability.

[0056] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a solid electrolyte tantalum capacitor for high-temperature and high-humidity environments, characterized in that, include: Preparation of tantalum anode (1); The tantalum anode (1) is covered with a dielectric layer (2); including: spot welding the sintered tantalum anode (1) to a stainless steel strip and placing it in a forming tank containing an ethylene glycol phosphate electrolyte at a temperature of 85°C and a resistivity of 800 to 1500 Ω·cm, to perform electrochemical formation of the dielectric layer (2); The dielectric layer (2) is covered with a solid electrolyte layer (3); including: immersing the tantalum anode (1) of the dielectric layer (2) in a manganese nitrate solution, thermally decomposing it at a temperature of 250°C and a humidity of 5%RH-13%RH, and repeating the process 10 to 12 times to form a manganese dioxide cathode as a solid electrolyte layer (3) on the dielectric layer 2, the thickness of which is 0.1 mm to 0.3 mm; The solid electrolyte layer (3) is coated with a graphite silver paste layer (4); it also includes: the tantalum anode (1) after forming the MnO2 cathode is immersed in a hydrolyzed coupling agent solution for 10 min-2 h, then dried, and then the tantalum block is immersed in an oily graphite solution and a silver paste solution to generate a graphite silver paste layer (4). The graphite silver paste layer (4) is covered with an epoxy shell (7); the epoxy shell (7) encapsulation includes: using polymer conductive silver paste to connect the tantalum body covering the moisture-proof layer (5) to the lead frame, and the assembled body is encapsulated with an epoxy resin layer outside the body by molding to form an epoxy shell (7). The dielectric layer (2), solid electrolyte layer (3) or graphite silver paste layer (4) are covered with a moisture-proof layer (5) in addition to one, two or three layers. The moisture-proof coating (5) includes coating by one or more combinations of coating processes such as sputtering, impregnation or deposition.

2. The method for preparing a solid electrolyte tantalum capacitor for high-temperature and high-humidity environments according to claim 1, characterized in that, The electrolyte contains 0.1% phosphoric acid by volume and 50% ethylene glycol by volume.

3. The method for preparing a solid electrolyte tantalum capacitor for high-temperature and high-humidity environments according to claim 1, characterized in that, The process of sequentially immersing the tantalum block in an oily graphite solution and a silver paste solution to generate a graphite silver paste layer (4) includes: After drying at 125°C for 10 min, the tantalum block is sequentially immersed in an oily graphite solution and a silver paste solution. After immersion, it is dried at 160°C for 30 min to form a graphite layer and a silver paste layer as a graphite-silver paste layer (4), which is used as the lead-out of the cathode lead (8).

4. The method for preparing a solid electrolyte tantalum capacitor for high-temperature and high-humidity environments according to claim 1, 2, or 3, characterized in that, The process of coating the graphite silver paste layer (4) with a moisture-proof layer (5) includes: The tantalum anode (1) covered with the dielectric layer (2), solid electrolyte layer (3) and graphite silver paste layer (4) is heat-treated at 100℃ for 30min. Then the heat-treated tantalum body and moisture-proof material are placed in a vacuum coating furnace with a vacuum degree of 2.8Pa and kept for 30s to generate a moisture-proof layer covering the entire tantalum core.

5. The method for preparing a solid electrolyte tantalum capacitor for high temperature and high humidity environments according to claim 4, characterized in that, The deposition coating process includes vacuum coating, coating time of 30s to 5min, vacuum degree of 1.0 to 5.0Pa, heat treatment temperature of 100℃ to 200℃, to generate a moisture-proof layer (5) with a thickness of 0.0001mm to 0.01mm.

6. The method for preparing a solid electrolyte tantalum capacitor for high temperature and high humidity environments according to claim 4, characterized in that, The moisture-proof layer (5) material includes one or more of polyacrylate, polyurethane and polyvinylsiloxane in any proportion.

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