CN116246888A - Manganese dioxide cathode of surge-resistant tantalum electrolytic capacitor, capacitor and preparation method of manganese dioxide cathode - Google Patents

Manganese dioxide cathode of surge-resistant tantalum electrolytic capacitor, capacitor and preparation method of manganese dioxide cathode Download PDF

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CN116246888A
CN116246888A CN202310297806.0A CN202310297806A CN116246888A CN 116246888 A CN116246888 A CN 116246888A CN 202310297806 A CN202310297806 A CN 202310297806A CN 116246888 A CN116246888 A CN 116246888A
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tantalum
manganese dioxide
electrolytic capacitor
cathode
manganese
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林俊鸿
蔡澍炜
陈小吟
王殊源
陈玉坤
孙涛
许坤峰
蔡劲军
郑志杰
陈文凯
吴思杰
潘勋贤
姜添宪
涂航宇
陈领
许俊铭
蔡世扬
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Fujian Torch Electron Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
    • H01G9/0425—Electrodes or formation of dielectric layers thereon characterised by the material specially adapted for cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/14—Structural combinations or circuits for modifying, or compensating for, electric characteristics of electrolytic capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/15—Solid electrolytic capacitors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

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Abstract

The invention discloses a manganese dioxide cathode of a surge-resistant tantalum electrolytic capacitor, a capacitor and a preparation method thereof, wherein the preparation method of the manganese dioxide cathode comprises the following steps: providing a tantalum core anode coated with a tantalum pentoxide dielectric film, immersing in manganese nitrate solution with different specific gravities for high-temperature vapor decomposition, and forming a first cathode layer on the tantalum pentoxide dielectric film after repeated operation for a plurality of times; and forming a second cathode layer on the surface of the first cathode layer in an electrochemical mode, and then performing heat treatment to form the manganese dioxide cathode. The invention improves the integrity and continuity of the manganese dioxide cathode layer, greatly reduces the combustion and explosion risks of the tantalum electrolytic capacitor while maintaining the excellent performance of the tantalum electrolytic capacitor, and improves the use safety of the tantalum electrolytic capacitor.

Description

Manganese dioxide cathode of surge-resistant tantalum electrolytic capacitor, capacitor and preparation method of manganese dioxide cathode
Technical Field
The invention relates to the field of ceramic capacitors, in particular to a manganese dioxide cathode of a surge-resistant tantalum electrolytic capacitor, a capacitor and a preparation method thereof.
Background
With the rapid development of the electronic information industry, integration, miniaturization, high frequency and high density have become major trends in the development of electronic devices. The tantalum electrolytic capacitor has higher volume specific capacity, good temperature stability and frequency stability, and is widely applied to small-sized complete machine electronic equipment such as mobile communication, notebook computers, palm computers, automobile electronics and the like, and has good application prospects in the aspects of aviation, aerospace, petroleum drilling and the like. However, the electrolyte layer of the common sheet type solid electrolyte tantalum capacitor is composed of manganese dioxide, the manganese dioxide layer in the prior art is formed by decomposing and accumulating manganese nitrate for a plurality of times at a certain temperature, and the problems of random and discontinuous structure of the manganese dioxide layer exist, so that the tantalum capacitor has larger resistance, and the risk of burning and explosion is easily generated due to surge current existing in a circuit in the actual use process.
In view of this, it is very important to provide a tantalum electrolytic capacitor excellent in surge current resistance and a method for manufacturing the same.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a manganese dioxide cathode of a surge-resistant tantalum electrolytic capacitor, a capacitor and a preparation method thereof, which can effectively improve the surge current resistance of the tantalum electrolytic capacitor.
In order to achieve the above object, the technical scheme of the present invention is as follows:
a preparation method of a manganese dioxide cathode of a surge-resistant tantalum electrolytic capacitor comprises the following steps:
1) Providing a tantalum core anode coated with a tantalum pentoxide dielectric film, immersing in manganese nitrate solution with different specific gravities for high-temperature vapor decomposition, and forming a first cathode layer on the tantalum pentoxide dielectric film after repeated operation for a plurality of times;
2) Forming a second cathode layer on the surface of the first cathode layer in an electrochemical mode;
3) And (3) carrying out heat treatment on the sample obtained in the step (2) to form a manganese dioxide cathode.
Preferably, the electrochemical manner in the step 2 specifically includes:
connecting the external electrode with the tantalum core anode in the sample obtained in the step 1 to serve as an anode, taking a graphite plate or a stainless steel plate as a cathode, putting the anode into an electrolyte solution taking soluble salt of manganese as a solute, and performing a reaction at a temperature of between 0.1 and 20mA/cm 2 Constant current power-up is carried out for 5 to 60 minutes under the current density of (3).
Preferably, the soluble salt of manganese comprises manganese nitrate, manganese sulfate, manganese chloride and manganese acetate, water is used as a solvent in the electrolyte solution, and the molar concentration of the soluble salt of manganese is 0.01-1 mol/L.
Preferably, the tantalum core anode coated with the tantalum pentoxide dielectric film has a tantalum wire led out from a tantalum core, and is connected with the external electrode through the tantalum wire.
Preferably, the temperature of the heat treatment is 250 to 400 ℃.
Preferably, the time of the heat treatment is 5 to 60 minutes.
Preferably, the second cathode layer is uniform and dense manganese dioxide, and the grain surface roughness of the second cathode layer is smaller than the grain surface roughness of the first cathode layer.
The manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor is prepared by adopting the preparation method of the manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor.
A preparation method of a solid sheet type tantalum electrolytic capacitor comprises a preparation step of a tantalum core anode, a preparation step of a tantalum pentoxide dielectric film and a preparation method of a manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor.
The solid sheet type tantalum electrolytic capacitor is prepared by adopting the preparation method of the solid sheet type tantalum electrolytic capacitor.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention carries out strengthening treatment on the basis of the first cathode layer obtained by dipping and high-temperature vapor decomposition, adopts an electrochemical mode to prepare the uniform and compact second cathode layer with good consistency on the first cathode layer, and ensures better manganese dioxide performance through heat treatment.
(2) The surface roughness of the crystal grain of the second cathode layer of the solid sheet type tantalum electrolytic capacitor prepared by the method is smaller than that of the manganese dioxide cathode formed by dipping and high-temperature decomposition, and the surface of the manganese dioxide cathode layer is smoother and denser, so that the continuity of the conductive layer of the film layer is ensured, and the method plays a key role in improving the surge current performance. The invention not only improves the integrity and continuity of the manganese dioxide cathode layer, but also avoids heating and burning caused by larger local resistance, and avoids the point discharge risk caused by surface protrusion while maintaining the excellent performance of the tantalum electrolytic capacitor, and can also greatly reduce the burning and explosion risks of the tantalum electrolytic capacitor and improve the use safety of the tantalum electrolytic capacitor.
(3) The finished product of the solid-chip tantalum electrolytic capacitor prepared by the method has higher qualification rate after aging, and the product has no leakage current increase or short circuit failure after surge current test, so that the qualification rate and the product safety after the surge current test are effectively improved.
Drawings
The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain the principles of the invention. Many of the intended advantages of other embodiments and embodiments will be readily appreciated as they become better understood by reference to the following detailed description.
FIG. 1 is a scanning electron microscope image of a manganese dioxide cathode of a solid sheet type tantalum electrolytic capacitor prepared in example 1 of the present application;
FIG. 2 is a scanning electron microscope image of a manganese dioxide cathode of a solid sheet type tantalum electrolytic capacitor prepared in comparative example 1 of the present application;
FIG. 3 is a scanning electron microscope image of a manganese dioxide cathode of a solid sheet type tantalum electrolytic capacitor prepared in comparative example 3 of the present application;
fig. 4 is a scanning electron microscope image of a manganese dioxide cathode of a solid sheet type tantalum electrolytic capacitor prepared in comparative example 4 of the present application.
Detailed Description
The present application is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
The embodiment of the invention provides a preparation method of a manganese dioxide cathode of a surge-resistant tantalum electrolytic capacitor, which comprises the following steps:
1) Providing a tantalum core anode coated with a tantalum pentoxide dielectric film, immersing in manganese nitrate solution with different specific gravities for high-temperature vapor decomposition, and forming a first cathode layer on the tantalum pentoxide dielectric film after repeated operation for a plurality of times;
2) Forming a second cathode layer on the surface of the first cathode layer in an electrochemical mode, specifically, connecting an external electrode with a tantalum core anode in the sample obtained in the step 1 to serve as an anode, taking a graphite plate or a stainless steel plate as a cathode, putting the anode into an electrolyte solution taking soluble salt of manganese as a solute, and performing a reaction between 0.1 and 20mA/cm 2 Constant current power-up is carried out for 5 to 60 minutes under the current density of (3).
3) And (3) carrying out heat treatment on the sample obtained in the step (2) at the temperature of 250-400 ℃ for 5-60 min to form the manganese dioxide cathode.
In a specific embodiment, the soluble salt of manganese comprises manganese nitrate, manganese sulfate, manganese chloride and manganese acetate, and the electrolyte solution uses water as a solvent, and the molar concentration of the soluble salt of manganese is 0.01-1 mol/L.
Specifically, the tantalum core anode coated with the tantalum pentoxide dielectric film is provided with a tantalum wire led out from a tantalum core, and is connected with an external electrode through the tantalum wire. The second cathode layer is uniform and dense manganese dioxide, and has a smooth grain surface, and the grain surface roughness of the second cathode layer is less than that of the first cathode layer.
The manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor is prepared by adopting the preparation method of the manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor.
A preparation method of a solid sheet type tantalum electrolytic capacitor comprises a preparation step of a tantalum core anode, a preparation step of a tantalum pentoxide dielectric film, a preparation method of a manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor and a packaging step. The preparation method of the tantalum core anode and the preparation method of the tantalum pentoxide dielectric film are both carried out in the conventional mode, and the tantalum core anode is formed by compression molding and sintering at high temperature under vacuum conditions. The tantalum pentoxide dielectric film is prepared by adopting an electrochemical mode.
The solid chip tantalum electrolytic capacitor is basically the same as the traditional chip solid electrolyte tantalum capacitor in structure mode, and is prepared by the preparation method of the solid chip tantalum electrolytic capacitor. Firstly, according to the design, the tantalum powder particles are pressed and molded, vacuum sintering is carried out to obtain a tantalum core anode, then a tantalum pentoxide dielectric film is formed in an electrochemical mode, manganese dioxide is coated on the tantalum core anode as a cathode, finally, core block assembly is carried out, and products are molded and sealed by epoxy resin. However, the preparation method of the manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor is adopted in the preparation process of the manganese dioxide cathode because of being a high-safety product, and a new preparation process and a solution formula are adopted to finally prepare the tantalum electrolytic capacitor with excellent surge current performance.
The present invention is further illustrated by the following examples, which are not intended to limit the scope or applicability of the invention.
Example 1
The embodiment provides a preparation method of a solid sheet type tantalum electrolytic capacitor, which comprises the following steps:
1) Anode design: tantalum metal powder with uniform particle size is selected, the weight of the tantalum powder is calculated, tantalum wires are inserted into the tantalum powder and pressed into square blocks, and then the tantalum powder is sintered into the porous substrate tantalum core anode under the conditions of high temperature and vacuum.
2) Forming a dielectric film: and forming a tantalum pentoxide dielectric film with uniform thickness and good consistency on the surface of the tantalum core anode by using an aqueous solution prepared by taking nitric acid as an electrolyte as a forming solution and electrochemically forming the tantalum core anode in the forming solution.
3) Preparation of the first cathode layer: and (3) putting the tantalum core anode with the tantalum pentoxide dielectric film into manganese nitrate solutions with different specific gravities for soaking and high-temperature steam decomposition, and repeatedly performing operation for multiple times to form a first cathode layer, wherein the first cathode layer is manganese dioxide.
4) First cathode layer reinforcement treatment: the tantalum core anode having the first cathode layer formed thereon was put into a metal oxide film formed by a process of adding manganese nitrate (Mn (NO) 3 ) 2 ) An aqueous solution having a molar concentration of 0.1mol/L was prepared as the electrolyte. Is connected with a tantalum core anode through an external electrode to serve as an anode, and a graphite plate is used as a cathode, at 20mA/cm 2 Constant current power-up is carried out for 30min under the current density, a layer of uniform and compact manganese dioxide is prepared on the surface of the first cathode layer formed in the preparation step of the first cathode layer to serve as a second cathode layer, and then the second cathode layer is subjected to heat treatment at 250 ℃ for 20min, so that a manganese dioxide cathode is finally obtained.
5) Assembling a chip tantalum capacitor: and (3) sequentially preparing a graphite layer and a silver layer outside the tantalum core anode after the step (4) in a dipping manner, then attaching the tantalum core anode on a lead frame cathode by using silver paste, connecting a tantalum wire of the tantalum core anode with a positive lead frame in a resistance welding manner, and then carrying out mould pressing encapsulation, ageing and testing by using epoxy resin.
Example 2
The embodiment provides a preparation method of a solid sheet type tantalum electrolytic capacitor, which comprises the following steps:
1) Anode design: selecting tantalum metal powder with uniform particle size, calculating the weight of the tantalum powder, inserting tantalum wires into the tantalum powder, pressing the tantalum wire into square blocks, and sintering the tantalum wire into a porous substrate tantalum core anode under the conditions of high temperature and vacuum;
2) Forming a dielectric film: taking aqueous solution prepared by taking nitric acid as electrolyte as forming liquid, and forming a tantalum pentoxide dielectric film with uniform thickness and good consistency on the surface of the tantalum core anode in the forming liquid in an electrochemical mode;
3) Preparation of the first cathode layer: and (3) putting the tantalum core anode with the tantalum pentoxide dielectric film into manganese nitrate solutions with different specific gravities for soaking and high-temperature steam decomposition, and repeatedly performing operation for multiple times to form a first cathode layer, wherein the first cathode layer is manganese dioxide.
4) First cathode layer reinforcement treatment: putting the tantalum core anode with the first cathode layer into manganese chloride (MnCl) 2 ) An aqueous solution having a molar concentration of 0.01mol/L was prepared as the electrolyte. Is connected with a tantalum core anode through an external electrode to serve as an anode, and a graphite plate is used as a cathode, at 10mA/cm 2 Constant current power-up is carried out for 60min under the current density, a layer of uniform and compact manganese dioxide is prepared on the surface of the first cathode layer formed in the preparation step of the first cathode layer to serve as a second cathode layer, and then the second cathode layer is subjected to heat treatment at 350 ℃ for 10min, so that a manganese dioxide cathode is finally obtained.
5) Assembling a chip tantalum capacitor: and (3) sequentially preparing a graphite layer and a silver layer outside the tantalum core anode after the step (4) in a dipping manner, then attaching the tantalum core anode on a lead frame cathode by using silver paste, connecting a tantalum wire of the tantalum core anode with a positive lead frame in a resistance welding manner, and then carrying out mould pressing encapsulation, ageing and testing by using epoxy resin.
Example 3
The embodiment provides a preparation method of a solid sheet type tantalum electrolytic capacitor, which comprises the following steps:
1) Anode design: selecting tantalum metal powder with uniform particle size, calculating the weight of the tantalum powder, inserting tantalum wires into the tantalum powder, pressing the tantalum wire into square blocks, and sintering the tantalum wire into a porous substrate tantalum core anode under the conditions of high temperature and vacuum;
2) Forming a dielectric film: taking aqueous solution prepared by taking nitric acid as electrolyte as forming liquid, and forming a tantalum pentoxide dielectric film with uniform thickness and good consistency on the surface of the tantalum core anode in the forming liquid in an electrochemical mode;
3) Preparation of the first cathode layer: and (3) putting the tantalum core anode with the tantalum pentoxide dielectric film into manganese nitrate solutions with different specific gravities for soaking and high-temperature steam decomposition, and repeatedly performing operation for multiple times to form a first cathode layer, wherein the first cathode layer is manganese dioxide.
4) First cathode layer reinforcement treatment: putting the tantalum core anode with the first cathode layer into a solution of manganese sulfate (MnSO 4 ) An aqueous solution having a molar concentration of 1mol/L was prepared as the electrolyte. Is connected with a tantalum core anode through an external electrode to serve as an anode, and a graphite plate is used as a cathode, and the anode is at 0.1mA/cm 2 Constant current power-up is carried out for 5min under the current density, a layer of uniform and compact manganese dioxide is prepared on the surface of the first cathode layer formed in the preparation step of the first cathode layer to serve as a second cathode layer, and then the second cathode layer is subjected to heat treatment at 400 ℃ for 5min, so that a manganese dioxide cathode is finally obtained.
5) Assembling a chip tantalum capacitor: and (3) sequentially preparing a graphite layer and a silver layer outside the tantalum core anode after the step (4) in a dipping manner, then attaching the tantalum core anode on a lead frame cathode by using silver paste, connecting a tantalum wire of the tantalum core anode with a positive lead frame in a resistance welding manner, and then carrying out mould pressing encapsulation, ageing and testing by using epoxy resin.
Comparative example 1
The comparative example proposes a method for manufacturing a solid sheet type tantalum electrolytic capacitor, comprising the following steps:
1) Anode design: selecting tantalum metal powder with uniform particle size, calculating the weight of the tantalum powder, inserting tantalum wires into the tantalum powder, pressing the tantalum wire into square blocks, and sintering the tantalum wire into a porous substrate tantalum core anode under the conditions of high temperature and vacuum;
2) Forming a dielectric film: taking aqueous solution prepared by taking nitric acid as electrolyte as forming liquid, and forming a tantalum pentoxide dielectric film with uniform thickness and good consistency on the surface of the tantalum core anode in the forming liquid in an electrochemical mode;
3) Manufacturing a manganese dioxide cathode: and (3) putting the tantalum core anode with the tantalum pentoxide dielectric film into manganese nitrate solutions with different specific gravities for soaking and high-temperature vapor decomposition, and repeating the operation for a plurality of times to form the manganese dioxide cathode.
4) Assembling a chip tantalum capacitor: and (3) sequentially preparing a graphite layer and a silver layer outside the tantalum core anode after the step (3) in a dipping manner, then attaching the tantalum core anode on a lead frame cathode by using silver paste, connecting a tantalum wire of the tantalum core anode with a positive lead frame in a resistance welding manner, and then carrying out mould pressing encapsulation, ageing and testing by using epoxy resin.
Comparative example 2
The comparative example proposes a method for manufacturing a solid sheet type tantalum electrolytic capacitor, comprising the following steps:
1) Anode design: selecting tantalum metal powder with uniform particle size, calculating the weight of the tantalum powder, inserting tantalum wires into the tantalum powder, pressing the tantalum wire into square blocks, and sintering the tantalum wire into a porous substrate tantalum core anode under the conditions of high temperature and vacuum;
2) Forming a dielectric film: taking aqueous solution prepared by taking nitric acid as electrolyte as forming liquid, and forming a tantalum pentoxide dielectric film with uniform thickness and good consistency on the surface of the tantalum core anode in the forming liquid in an electrochemical mode;
3) Preparation of the first cathode layer: and (3) putting the tantalum core anode with the tantalum pentoxide dielectric film into manganese nitrate solutions with different specific gravities for soaking and high-temperature steam decomposition, and repeatedly performing operation for multiple times to form a first cathode layer, wherein the first cathode layer is manganese dioxide.
4) First cathode layer reinforcement treatment: putting the tantalum core anode with the first cathode layer into a solution of manganese sulfate (MnSO 4 ) An aqueous solution having a molar concentration of 1mol/L was prepared as the electrolyte. Is connected with a tantalum core anode through an external electrode to serve as an anode, and a graphite plate is used as a cathode, and the anode is at 0.1mA/cm 2 And (3) constant current power-up is carried out for 5min under the current density, and a layer of uniform and compact manganese dioxide is prepared on the surface of the first cathode layer formed in the preparation step of the first cathode layer to serve as a second cathode layer, so that a manganese dioxide cathode is obtained.
5) Assembling a chip tantalum capacitor: and (3) sequentially preparing a graphite layer and a silver layer outside the tantalum core anode after the step (4) in a dipping manner, then attaching the tantalum core anode on a lead frame cathode by using silver paste, connecting a tantalum wire of the tantalum core anode with a positive lead frame in a resistance welding manner, and then carrying out mould pressing encapsulation, ageing and testing by using epoxy resin.
Comparative example 3
The comparative example proposes a method for manufacturing a solid sheet type tantalum electrolytic capacitor, comprising the following steps:
1) Anode design: selecting tantalum metal powder with uniform particle size, calculating the weight of the tantalum powder, inserting tantalum wires into the tantalum powder, pressing the tantalum wire into square blocks, and sintering the tantalum wire into a porous substrate tantalum core anode under the conditions of high temperature and vacuum;
2) Forming a dielectric film: taking aqueous solution prepared by taking nitric acid as electrolyte as forming liquid, and forming a tantalum pentoxide dielectric film with uniform thickness and good consistency on the surface of the tantalum core anode in the forming liquid in an electrochemical mode;
3) Preparation of cathode layer: and (3) putting the tantalum core anode with the tantalum pentoxide dielectric film into manganese nitrate solutions with different specific gravities for soaking and high-temperature steam decomposition, repeatedly operating for a plurality of times to form a manganese dioxide layer, and then carrying out heat treatment on manganese dioxide at 400 ℃ for 10min to finally obtain the manganese dioxide cathode.
4) Assembling a chip tantalum capacitor: and (3) sequentially preparing a graphite layer and a silver layer outside the tantalum core anode after the step (3) in a dipping manner, then attaching the tantalum core anode on a lead frame cathode by using silver paste, connecting a tantalum wire of the tantalum core anode with a positive lead frame in a resistance welding manner, and then carrying out mould pressing encapsulation, ageing and testing by using epoxy resin.
Comparative example 4
The comparative example proposes a method for manufacturing a solid sheet type tantalum electrolytic capacitor, comprising the following steps:
1) Anode design: selecting tantalum metal powder with uniform particle size, calculating the weight of the tantalum powder, inserting tantalum wires into the tantalum powder, pressing the tantalum wire into square blocks, and sintering the tantalum wire into a porous substrate tantalum core anode under the conditions of high temperature and vacuum;
2) Forming a dielectric film: taking aqueous solution prepared by taking nitric acid as electrolyte as forming liquid, and forming a tantalum pentoxide dielectric film with uniform thickness and good consistency on the surface of the tantalum core anode in the forming liquid in an electrochemical mode;
3) Preparation of the first cathode layer: and (3) putting the tantalum core anode with the tantalum pentoxide dielectric film into manganese nitrate solutions with different specific gravities for soaking and high-temperature vapor decomposition, and repeatedly operating to form a manganese dioxide layer to finally obtain the manganese dioxide first cathode layer.
4) First cathode layer reinforcement treatment: putting the tantalum core anode with the first cathode layer formed into a solution containing 0.03wt% of polyoxyethylene nonylphenol ammonium acetate as a viscosity reducer and 0.1wt% of ethanol as a dispersing agent with a specific gravity of 1.3g/cm 3 Dipping the tantalum core into the manganese nitrate solution for one time, and decomposing the tantalum core for 6 minutes under the conditions that the temperature is 260 ℃, the vapor pressure is 0.05MPa and the oxygen mass percentage concentration is 9%, thus obtaining the manganese dioxide cathode.
5) Assembling a chip tantalum capacitor: and (3) sequentially preparing a graphite layer and a silver layer outside the tantalum core anode after the step (4) in a dipping manner, then attaching the tantalum core anode on a lead frame cathode by using silver paste, connecting a tantalum wire of the tantalum core anode with a positive lead frame in a resistance welding manner, and then carrying out mould pressing encapsulation, ageing and testing by using epoxy resin.
The solid sheet type tantalum electrolytic capacitors prepared in examples 1 to 3 and comparative example were subjected to an aging test and a surge current test, and the results shown in table 1 were obtained.
Table 1 surge current test qualification statistics for comparative and example
Figure BDA0004143780260000071
Figure BDA0004143780260000081
Fig. 1 shows the sem images of the second cathode layer prepared electrochemically in step 4 of example 1, and fig. 2-4 show the sem images of the manganese dioxide cathodes prepared in comparative example 1 and comparative examples 3 and 4, respectively. From the graph, it can be seen that the embodiment of the application adopts the electrochemical mode to carry out the strengthening treatment on the basis of the first cathode layer, so as to obtain the manganese dioxide layer with smaller grain surface roughness, and the manganese dioxide layer is even and compact, and is more coherent and complete, so that the surge current resistance performance is more excellent. The manganese dioxide cathodes prepared in comparative example 1 and comparative examples 3 and 4 were rough in grain surface, resulting in poor surge current resistance. In contrast, the manganese dioxide layer prepared only electrochemically in comparative example 2 has poor conductivity, and the conductivity can be significantly improved by heat treatment. The ESR of the solid sheet type tantalum electrolytic capacitor can be effectively reduced by combining electrochemical mode with heat treatment, and the electrical performance is improved.
According to the manganese dioxide cathode of the tantalum electrolytic capacitor, the tantalum electrolytic capacitor and the preparation method thereof, the manganese dioxide layer on the surface of the tantalum electrolytic capacitor is uniform and compact, the consistency is good, the qualification rate after finished product aging is higher and reaches more than 90%, the product has no leakage current increase or short circuit failure after surge current test, the qualification rate after the surge current test can reach 100%, and the use safety of the tantalum electrolytic capacitor is effectively improved.
While the present invention has been described with reference to the specific embodiments thereof, the scope of the present invention is not limited thereto, and any changes or substitutions will be apparent to those skilled in the art within the scope of the present invention, and are intended to be covered by the present invention. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. The preparation method of the manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor is characterized by comprising the following steps of:
1) Providing a tantalum core anode coated with a tantalum pentoxide dielectric film, immersing in manganese nitrate solution with different specific gravities for high-temperature vapor decomposition, and forming a first cathode layer on the tantalum pentoxide dielectric film after repeated operation for a plurality of times;
2) Forming a second cathode layer on the surface of the first cathode layer in an electrochemical mode;
3) And (3) carrying out heat treatment on the sample obtained in the step (2) to form a manganese dioxide cathode.
2. The method for preparing a manganese dioxide cathode of a surge-resistant tantalum electrolytic capacitor according to claim 1, wherein the electrochemical method in step 2 specifically comprises:
connecting the external electrode with the tantalum core anode in the sample obtained in the step 1 to serve as an anode, taking a graphite plate or a stainless steel plate as a cathode, putting the anode into an electrolyte solution taking soluble salt of manganese as a solute, and performing a reaction at a temperature of between 0.1 and 20mA/cm 2 Constant current power-up is carried out for 5 to 60 minutes under the current density of (3).
3. The method for preparing manganese dioxide cathode of surge-resistant tantalum electrolytic capacitor according to claim 2, wherein the soluble salt of manganese comprises manganese nitrate, manganese sulfate, manganese chloride and manganese acetate, water is used as solvent in the electrolyte solution, and the molar concentration of the soluble salt of manganese is 0.01-1 mol/L.
4. The method for producing a manganese dioxide cathode for a surge-resistant tantalum electrolytic capacitor according to claim 2, wherein said tantalum core anode having been coated with a tantalum pentoxide dielectric film has a tantalum wire led out from a tantalum core, and is connected to said external electrode through said tantalum wire.
5. The method for producing a manganese dioxide cathode for a surge-resistant tantalum electrolytic capacitor according to claim 1, wherein the temperature of the heat treatment is 250 to 400 ℃.
6. The method for producing a manganese dioxide cathode for a surge-resistant tantalum electrolytic capacitor according to claim 1, wherein the time for the heat treatment is 5 to 60 minutes.
7. The method of producing manganese dioxide cathode for a surge-resistant tantalum electrolytic capacitor according to claim 1, wherein said second cathode layer is uniform and dense manganese dioxide and has a grain surface roughness smaller than that of said first cathode layer.
8. A manganese dioxide cathode of a surge-resistant tantalum electrolytic capacitor, which is characterized by being prepared by the preparation method of the manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor in any one of claims 1-7.
9. A method for preparing a solid sheet type tantalum electrolytic capacitor, which is characterized by comprising a step for preparing a tantalum core anode, a step for preparing a tantalum pentoxide dielectric film and a method for preparing a manganese dioxide cathode of the surge-resistant tantalum electrolytic capacitor as claimed in any one of claims 1 to 7.
10. A solid-chip tantalum electrolytic capacitor, which is characterized by being prepared by the preparation method of the solid-chip tantalum electrolytic capacitor as claimed in claim 9.
CN202310297806.0A 2023-03-24 2023-03-24 Manganese dioxide cathode of surge-resistant tantalum electrolytic capacitor, capacitor and preparation method of manganese dioxide cathode Pending CN116246888A (en)

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