CN113192755A - Anodic oxidation method of electrolytic capacitor - Google Patents
Anodic oxidation method of electrolytic capacitor Download PDFInfo
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- CN113192755A CN113192755A CN202110470833.4A CN202110470833A CN113192755A CN 113192755 A CN113192755 A CN 113192755A CN 202110470833 A CN202110470833 A CN 202110470833A CN 113192755 A CN113192755 A CN 113192755A
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- 230000003647 oxidation Effects 0.000 title claims abstract description 155
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 155
- 238000000034 method Methods 0.000 title claims abstract description 61
- 239000003990 capacitor Substances 0.000 title claims abstract description 32
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 140
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 70
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 49
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 48
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 36
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- 230000000295 complement effect Effects 0.000 claims abstract description 13
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 44
- 238000007743 anodising Methods 0.000 claims description 18
- 229910052751 metal Inorganic materials 0.000 claims description 12
- 239000002184 metal Substances 0.000 claims description 12
- 230000000052 comparative effect Effects 0.000 description 23
- 238000005406 washing Methods 0.000 description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 18
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 14
- 239000000843 powder Substances 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- 229910052786 argon Inorganic materials 0.000 description 7
- 238000001816 cooling Methods 0.000 description 7
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 7
- 238000003825 pressing Methods 0.000 description 5
- 238000002048 anodisation reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- -1 oxygen ion Chemical class 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
- H01G9/052—Sintered electrodes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/26—Anodisation of refractory metals or alloys based thereon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
- H01G9/052—Sintered electrodes
- H01G9/0525—Powder therefor
Abstract
The application provides an anodic oxidation method of an electrolytic capacitor, and belongs to the technical field of capacitors. The anodic oxidation method comprises the following steps: carrying out first-stage oxidation treatment on the anode in a nitric acid solution; then, carrying out second-stage oxidation treatment on the anode in a phosphoric acid solution; and then the anode is sequentially subjected to heat treatment and complementary formation treatment. The anodic oxidation method can solve the problems of poor thickness uniformity, low density and poor insulating strength of the dielectric oxide film layer, thereby effectively reducing the loss and leakage current of the anode.
Description
Technical Field
The application relates to the technical field of capacitors, in particular to an anodic oxidation method of an electrolytic capacitor.
Background
In recent years, as electronic complete machine systems are rapidly developed in the direction of miniaturization, integration, high power, high frequency and the like, the requirements for the size of the electrolytic capacitor are smaller and smaller, but the requirements for the capacity are larger and larger, so that the specific capacity of valve metal (such as tantalum, niobium and the like) powder used by the electrolytic capacitor is higher and higher.
The higher the specific value of the valve metal powder is, the smaller the particle size of the valve metal powder is, the smaller the internal pore of the anode block formed by pressing and sintering is, and the greater the difficulty of anodic oxidation processing is. The prior anode oxidation method of the electrolytic capacitor is mainly suitable for the anode oxidation of the valve metal powder anode block with low volume ratio; when the anode block of the valve metal powder with a high specific value (more than or equal to 70K muF.V/g) is subjected to anodic oxidation, the produced dielectric oxide film layer has the problems of poor thickness uniformity, low density and poor insulating strength, and macroscopically shows that the loss and leakage current of the anode are large, so that the reliability of the prepared electrolytic capacitor is low.
Disclosure of Invention
The application aims to provide an anodic oxidation method of an electrolytic capacitor, which can solve the problems of poor thickness uniformity, low density and poor insulating strength of a dielectric oxide film layer when carrying out anodic oxidation of a high specific value valve metal powder anode block, thereby effectively reducing the loss and leakage current of an anode.
The embodiment of the application is realized as follows:
the embodiment of the application provides an anodic oxidation method of an electrolytic capacitor, which comprises the following steps: carrying out first-stage oxidation treatment on the anode in a nitric acid solution; then, carrying out second-stage oxidation treatment on the anode in a phosphoric acid solution; and then the anode is sequentially subjected to heat treatment and complementary formation treatment.
The anode oxidation method of the electrolytic capacitor provided by the embodiment of the application has the beneficial effects that:
according to the anodic oxidation method, nitric acid solution is used for carrying out first-stage oxidation treatment, so that a continuous dielectric oxidation film can be generated in micropores of an anode block; and then, performing second-stage oxidation treatment by using a phosphoric acid solution to form a medium oxide film with better density. The combination of the first-stage oxidation treatment and the second-stage oxidation treatment enables the dielectric oxide film after the heat treatment and the complementary formation treatment to have better thickness uniformity, density and insulating strength, thereby effectively reducing the loss and leakage current of the anode.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
It should be noted that "and/or" in the present application, such as "feature 1 and/or feature 2" refers to "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2" alone.
In the description of the present application, the range of "numerical value a to numerical value b" includes both values "a" and "b", and "unit of measure" in "numerical value a to numerical value b + unit of measure" represents "unit of measure" of both "numerical value a" and "numerical value b".
The method of anodizing the electrolytic capacitor according to the embodiment of the present application will be specifically described below.
The embodiment of the application provides an anodic oxidation method of an electrolytic capacitor, which comprises the following steps: carrying out first-stage oxidation treatment on the anode in a nitric acid solution; then, carrying out second-stage oxidation treatment on the anode in a phosphoric acid solution; and then the anode is sequentially subjected to heat treatment and complementary formation treatment.
As an example, the anode is made of valve metal with specific capacity value more than or equal to 70K muF.V/g. Optionally, the anode material has a specific value S of 70K μ F.V/g ≦ S ≦ 150K μ F.V/g, such as, but not limited to, a point value of any one of 70K μ F.V/g, 100K μ F.V/g, and 150K μ F.V/g, or a range value therebetween.
The inventor researches and discovers that for a valve metal powder anode block with a high specific value, due to the fact that the specific value is high, oxygen ion migration in an anodic oxidation process is insufficient, the anodic oxidation process is slow, and further, the thickness uniformity, the density and the insulating strength of a produced dielectric oxidation film layer are poor.
The nitric acid ion has small radius and good permeability, and the nitric acid solution is firstly used for carrying out the first-stage oxidation treatment, so that a continuous medium oxidation film can be generated in the micropores of the anode block, and the subsequent formation of the medium oxidation film with good thickness uniformity is facilitated. The phosphoric acid solution has good inhibition capability on liquid crystallization, good formability and high viscosity, and the phosphoric acid solution is used for the second stage oxidation treatment, so that a further formed medium oxidation film has better compactness. The cooperation of the first-stage oxidation treatment and the second-stage oxidation treatment is beneficial to forming a dielectric oxide film with good thickness uniformity and density, so that the dielectric oxide film after heat treatment and complementary formation has good thickness uniformity, density and insulating strength.
The anodic oxidation method provided by the application can form a dielectric oxide film with better thickness uniformity, density and insulation strength when being used for anodic oxidation of the valve metal powder anode block with a high specific value of more than or equal to 70K muF.V/g, so that the loss and leakage current of the anode can be effectively reduced.
The anodic oxidation method provided by the application has a good anodic oxidation effect on the valve metal powder anode block with the specific value of more than or equal to 70K muF.V/g, but is not limited to be only used for anodic oxidation of the valve metal powder anode block with the specific value of more than or equal to 70K muF.V/g.
It is to be understood that, in the present application, the first-stage oxidation treatment and the second-stage oxidation treatment are each a single anodic oxidation process, and thus the pressure-increasing process and the constant-pressure process are each performed separately in the two treatment stages. Namely, in the first-stage oxidation treatment, the voltage is increased to a first preset voltage and then constant voltage is carried out; in the second stage of oxidation treatment, the voltage is increased to a second preset voltage and then constant voltage is carried out.
The inventor researches and discovers that the conductivity of the solution, the temperature of the solution, the boosting speed, the magnitude of the constant voltage and the constant voltage time have certain influence on the effects of the first-stage oxidation treatment and the second-stage oxidation treatment, and the proper treatment parameters are favorable for ensuring the better anodic oxidation treatment effect while considering the treatment efficiency.
Regarding the first-stage oxidation treatment:
regarding the conductivity of the solution, in some alternative embodiments, the conductivity of the nitric acid solution at 25 ℃ is from 2 to 15mS/cm, such as, but not limited to, 2mS/cm, 3mS/cm, 4mS/cm, 5mS/cm, 6mS/cm, 7mS/cm, 8mS/cm, 9mS/cm, 10mS/cm, 11mS/cm, 12mS/cm, 13mS/cm, 14mS/cm, and 15mS/cm, or a range between any two thereof.
Optionally, the conductivity of the nitric acid solution at 25 ℃ is 2.5-6.5 mS/cm; or the conductivity of the nitric acid solution at 25 ℃ is 7-15 mS/cm.
With respect to the temperature of the solution, in some alternative embodiments, the temperature of the nitric acid solution is from 35 ℃ to 65 ℃, such as, but not limited to, any one of 35 ℃, 45 ℃, 55 ℃, and 65 ℃ or a range between any two.
For boost speed, in some alternative embodiments, the boost current density is 70-90 mA/g, such as but not limited to any one or a range of values between any two of 70mA/g, 75mA/g, 80mA/g, 85mA/g, and 90 mA/g.
For the constant voltage level, in some alternative embodiments, the first preset voltage is 50 to 75% of the final formation voltage of the anodic oxidation, such as but not limited to any one of 50%, 55%, 60%, 65%, 70% and 75%, or a range between any two.
It is understood that in the anodizing method of the electrolytic capacitor, the final formation voltage of the anodic oxidation means a constant voltage at the time of final anodic oxidation, that is, a magnitude of the constant voltage in the formation-compensating process of the constant voltage oxidation.
For the constant pressure time, in some alternative embodiments, the constant pressure time is 1 to 4 hours, such as but not limited to any one of 1 hour, 2 hours, 3 hours, and 4 hours or a range between any two. As an example, the constant pressure time is 4 h.
Optionally, when one or more of the conductivity of the solution, the temperature of the solution and the magnitude of the constant voltage is high, the constant voltage time is 1-2 h; or when one or more of the conductivity of the solution, the temperature of the solution and the magnitude of the constant voltage is low, the constant voltage time is 2-4 h.
Regarding the second-stage oxidation treatment:
regarding the conductivity of the solution, in some alternative embodiments, the conductivity of the phosphoric acid solution at 25 ℃ is 1 to 10mS/cm, such as, but not limited to, any one or a range between any two of 1mS/cm, 2mS/cm, 3mS/cm, 4mS/cm, 5mS/cm, 6mS/cm, 7mS/cm, 8mS/cm, 9mS/cm, and 10 mS/cm.
Optionally, the conductivity of the phosphoric acid solution at 25 ℃ is 1-5 mS/cm; or the conductivity of the phosphoric acid solution at 25 ℃ is 5.5-9 mS/cm.
With respect to the temperature of the solution, in some alternative embodiments, the temperature of the phosphoric acid solution in the second stage oxidation treatment is higher than the temperature of the nitric acid solution in the first stage oxidation treatment.
As an example, the temperature of the phosphoric acid solution is 65 to 95 ℃, such as but not limited to, any one of 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃ and 95 ℃ or a range between any two.
Optionally, the temperature of the phosphoric acid solution is 75-90 ℃.
With respect to the boosting speed, in some alternative embodiments, the boosting current density in the second-stage oxidation process is lower than that in the first-stage oxidation process.
As an example, the boost current density is 50-70 mA/g, such as but not limited to any one or a range of values between 50mA/g, 55mA/g, 60mA/g, 65mA/g and 70 mA/g.
For constant voltage levels, in some alternative embodiments, the second predetermined voltage is the final formation voltage of anodization.
For the constant pressure time, in some alternative embodiments, the constant pressure time is 4 to 8 hours, such as but not limited to any one of 4 hours, 5 hours, 6 hours, 7 hours and 8 hours or a range between any two. As an example, the constant pressure time is 8 hours.
Optionally, when one or more of the conductivity of the solution and the temperature of the solution is high, the constant pressure time is 4-6 h; or when one or more of the conductivity of the solution and the temperature of the solution is low, the constant pressure time is 6-8 h.
The inventor researches and discovers that when the phosphoric acid solution is used for carrying out anodic oxidation treatment, a certain amount of hydrogen peroxide is added into the phosphoric acid solution, so that the oxygen ion concentration in the anodic oxidation process can be improved, and the anode loss and the leakage current can be further reduced.
In some exemplary embodiments, the phosphoric acid solution contains hydrogen peroxide in the second stage oxidation treatment. As an example, the content of the hydrogen peroxide in the phosphoric acid solution is 0.1 to 1.5 wt%, for example, but not limited to, 0.1 wt%, 0.5 wt%, 1 wt%, or 1.5 wt%, or a range therebetween.
Optionally, the content of hydrogen peroxide in the phosphoric acid solution is 0.5-1 wt%.
It is to be understood that, in the present application, the requirements of the heat treatment and the complementary formation treatment are not particularly limited, and both may be performed in a manner well known in the art without additional description.
Regarding the heat treatment:
the inventor researches and discovers that in the anodic oxidation method, the treatment temperature in the heat treatment process is properly increased relative to the requirement of about 320 ℃ in the prior art, and the dense dielectric oxide film obtained after the heat treatment is more favorably ensured.
In some exemplary embodiments, the treatment temperature in the heat treatment is 380 to 420 ℃, such as but not limited to, 380 ℃, 390 ℃, 400 ℃, 410 ℃ and 420 ℃ or a range between any two.
Further, in the heat treatment, the treatment time is 15-30 min, such as but not limited to any one of 15min, 20min, 25min and 30min or a range value between any two.
The complementary forming treatment:
in some exemplary embodiments, the anode is subjected to constant-voltage oxidation with a phosphoric acid solution under the final formation voltage condition of the anodic oxidation in the complementary formation treatment. The phosphoric acid solution used in the complementary formation treatment is the same as that used in the second-stage oxidation treatment, and the temperature requirement of the phosphoric acid solution used in the complementary formation treatment is the same as that in the second-stage oxidation treatment.
Optionally, in the complementary forming treatment, the treatment time is 60-90 min, such as but not limited to, any one of 60min, 70min, 80min and 90min or a range value between any two.
The features and properties of the present application are described in further detail below with reference to examples.
Example 1
A method of anodizing an electrolytic capacitor comprising:
s1, first-stage oxidation treatment
Placing the anode block in a nitric acid solution with the temperature of 55 ℃; the conductivity of the nitric acid solution at 25 ℃ is 8.6 mS/cm. Energization at a boost current density of 70mA/g requires raising the voltage to 15V and then holding it at a constant voltage for 2 h.
S2, second stage oxidation treatment
Washing the anode block obtained in the step S1 with water, and then placing the anode block in a phosphoric acid solution with the temperature of 85 ℃; the phosphoric acid solution has the conductivity of 6.5mS/cm at the temperature of 25 ℃, and contains 0.5 wt% of hydrogen peroxide. Energization at a boost current density of 50mA/g requires raising the voltage to 23.5V and then maintaining the constant voltage for 6 h.
S3, heat treatment
And (4) washing the anode block obtained in the step S2 with water, then placing the anode block into a high-temperature furnace filled with argon and having the temperature of 380 ℃ for heat treatment, and keeping the temperature for 15 min.
S4, supplementary forming treatment
And cooling the anode block obtained in the step S3, then placing the cooled anode block into a phosphoric acid solution for formation, and then washing the anode block with water. The conditions of the phosphoric acid solution were the same as those used in the step S2, and the formation voltage was 23.5V and the time was 60 min.
In this embodiment, the preparation method of the anode block is as follows:
pressing capacitor-grade tantalum powder with specific value of 70 KmuF.V/g into an anode block with tantalum wire with the size of 1.7 x 3.5 x 5mm and the pressing density of 5.8g/cm3(ii) a Then, sintering was carried out at a temperature of 1300 ℃.
Example 2
A method of anodizing an electrolytic capacitor comprising:
s1, first-stage oxidation treatment
Placing the anode block in a nitric acid solution with the temperature of 55 ℃; the conductivity of the nitric acid solution at 25 ℃ is 8.6 mS/cm. Energization at a boost current density of 80mA/g required a voltage boost to 18V, followed by a constant voltage hold for 2.5 h.
S2, second stage oxidation treatment
Washing the anode block obtained in the step S1 with water, and then placing the anode block in a phosphoric acid solution with the temperature of 85 ℃; the phosphoric acid solution has the conductivity of 7mS/cm at the temperature of 25 ℃, and contains 0.7 wt% of hydrogen peroxide. Energization at a boost current density of 60mA/g requires raising the voltage to 26V and then maintaining the constant voltage for 8 hours.
S3, heat treatment
And (4) washing the anode block obtained in the step S2 with water, then placing the anode block into a high-temperature furnace filled with argon and having the temperature of 400 ℃ for heat treatment, and keeping the temperature for 20 min.
S4, supplementary forming treatment
And cooling the anode block obtained in the step S3, then placing the cooled anode block into a phosphoric acid solution for formation, and then washing the anode block with water. The conditions of the phosphoric acid solution were the same as those used in the step S2, and the formation voltage was 26V and the time was 90 min.
In this embodiment, the preparation method of the anode block is as follows:
the capacitor-grade tantalum powder with the specific value of 100 KmuF.V/g is pressed into an anode block with a tantalum wire, the size of which is 1.5 multiplied by 2.5 multiplied by 3.2mm, and the pressing density is 5.6g/cm3(ii) a Then, sintering is carried out at a temperature of 1250 ℃.
Example 3
A method of anodizing an electrolytic capacitor comprising:
s1, first-stage oxidation treatment
Placing the anode block in a nitric acid solution with the temperature of 55 ℃; the conductivity of the nitric acid solution at 25 ℃ is 6.5 mS/cm. Energization at a boost current density of 90mA/g requires the voltage to be raised to 8.5V and then held at constant voltage for 4 hours.
S2, second stage oxidation treatment
Washing the anode block obtained in the step S1 with water, and then placing the anode block in a phosphoric acid solution at the temperature of 75 ℃; the phosphoric acid solution has the conductivity of 5.5mS/cm at the temperature of 25 ℃, and contains 1 wt% of hydrogen peroxide. Energization at a boost current density of 70mA/g requires the voltage to be raised to 14.5V and then held at constant voltage for 8 hours.
S3, heat treatment
And (4) washing the anode block obtained in the step S2 with water, then placing the anode block into a high-temperature furnace filled with argon and having the temperature of 400 ℃ for heat treatment, and keeping the temperature for 25 min.
S4, supplementary forming treatment
And cooling the anode block obtained in the step S3, then placing the cooled anode block into a phosphoric acid solution for formation, and then washing the anode block with water. The conditions of the phosphoric acid solution were the same as those used in the step S2, and the formation voltage was 14.5V and the time was 90 min.
In this embodiment, the preparation method of the anode block is as follows:
the capacitor-grade tantalum powder with the specific value of 150 KmuF.V/g is pressed into an anode block with tantalum wires with the size of 1.5 multiplied by 2.5 multiplied by 3.2mm, and the pressing density is 5.4g/cm3(ii) a Then, sintering is carried out at a temperature of 1250 ℃.
Example 4 a method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in the steps S2 and S4, the phosphoric acid solution used does not contain hydrogen peroxide.
Example 5
A method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in step S1, the first preset voltage is 6.5V.
Example 6
A method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in step S1, the first preset voltage is 11V.
Example 7
A method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in step S1, the constant pressure holding time is 3 hours.
Example 8
A method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in step S1, the constant pressure holding time is 5 hours.
Example 9
A method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in step S2, the constant pressure holding time is 7 hours.
Example 10
A method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in step S2, the constant pressure holding time was 9 hours.
Example 11
A method of anodizing an electrolytic capacitor, which is different from example 3 only in that:
in step S3, the heat treatment temperature is 320 ℃ and the time is 25 min.
Comparative example 1
An anodic oxidation method of an electrolytic capacitor using the same anode block as in example 1.
The anodic oxidation method comprises the following steps:
s1, oxidation treatment
Placing the anode block in a phosphoric acid solution with the temperature of 85 ℃; the conductivity of the phosphoric acid solution at 25 ℃ was 8.6 mS/cm. Energization at a boost current density of 70mA/g requires raising the voltage to 23.5V and then maintaining the constant voltage for 8 hours.
S2, heat treatment
And (4) washing the anode block obtained in the step S1 with water, then placing the anode block into a high-temperature furnace filled with argon and having the temperature of 380 ℃ for heat treatment, and keeping the temperature for 15 min.
S3, forming compensation treatment
And cooling the anode block obtained in the step S2, then placing the cooled anode block into a phosphoric acid solution for formation, and then washing the anode block with water. The conditions of the phosphoric acid solution were the same as those used in the step S1, and the formation voltage was 23.5V and the time was 60 min.
Comparative example 2
An anodic oxidation method of an electrolytic capacitor using the same anode block as in example 2.
The anodic oxidation method comprises the following steps:
s1, oxidation treatment
Placing the anode block in a nitric acid solution with the temperature of 55 ℃; the conductivity of the nitric acid solution at 25 ℃ is 8.6 mS/cm. Energization at a boost current density of 80mA/g requires raising the voltage to 26V and then maintaining a constant voltage for 12 hours.
S2, heat treatment
And (4) washing the anode block obtained in the step S1 with water, then placing the anode block into a high-temperature furnace filled with argon and having the temperature of 400 ℃ for heat treatment, and keeping the temperature for 15 min.
S3, forming compensation treatment
And cooling the anode block obtained in the step S2, then putting the anode block into a nitric acid solution for formation, and then washing with water. The nitric acid solution was subjected to the same conditions as those used in the step S1, and the voltage for formation was 26V and the time was 90 min.
Comparative example 3
An anodic oxidation method of an electrolytic capacitor using the same anode block as in example 3.
The anodic oxidation method comprises the following steps:
s1, oxidation treatment
Placing the anode block in a nitric acid solution with the temperature of 55 ℃; the conductivity of the nitric acid solution at 25 ℃ is 6.5 mS/cm. Energization at a boost current density of 90mA/g requires the voltage to be raised to 14.5V and then held at constant voltage for 12 hours.
S2, heat treatment
And (4) washing the anode block obtained in the step S1 with water, then placing the anode block into a high-temperature furnace filled with argon and having the temperature of 400 ℃ for heat treatment, and keeping the temperature for 25 min.
S3, forming compensation treatment
And cooling the anode block obtained in the step S2, then putting the anode block into a nitric acid solution for formation, and then washing with water. The nitric acid solution was subjected to the same conditions as those used in the step S1, and the voltage for formation was 14.5V and the time was 90 min.
Comparative example 4
An anodic oxidation method of an electrolytic capacitor using the same anode block as in example 3.
The anodic oxidation method comprises the following steps:
s1, first-stage oxidation treatment
Placing the anode block in a phosphoric acid solution with the temperature of 75 ℃; the phosphoric acid solution has the conductivity of 5.5mS/cm at the temperature of 25 ℃, and contains 1 wt% of hydrogen peroxide. Energization at a boost current density of 90mA/g requires the voltage to be raised to 8.5V and then held at constant voltage for 4 hours.
S2, second stage oxidation treatment
Washing the anode block obtained in the step S1 with water, and then placing the anode block in a nitric acid solution at the temperature of 55 ℃; the conductivity of the nitric acid solution at 25 ℃ is 6.5 mS/cm. Energization at a boost current density of 70mA/g requires the voltage to be raised to 14.5V and then held at constant voltage for 8 hours.
S3, heat treatment
And (4) washing the anode block obtained in the step S2 with water, then placing the anode block into a high-temperature furnace filled with argon and having the temperature of 400 ℃ for heat treatment, and keeping the temperature for 25 min.
S4, supplementary forming treatment
And cooling the anode block obtained in the step S3, then putting the anode block into a nitric acid solution for formation, and then washing with water. The conditions of the acid washing solution were the same as those used in the step S2, and the voltage for formation was 14.5V and the time was 90 min.
Test examples
The capacitance, loss and leakage current of the anode blocks anodized in each example and comparative example were measured by taking 5 anode blocks anodized in each example and comparative example, respectively.
The detection method comprises the following steps:
(1) capacitance and loss: the measurement is carried out by adopting a capacitance measuring instrument under the conditions of 2.2V of direct current bias, 0.5V of peak-peak sinusoidal signals and 120Hz of working frequency, and the measurement temperature is room temperature.
(2) Leakage current: and measuring by using a leakage current tester, wherein the measured voltage is the final formed voltage, the charging time is 60s, and the measured temperature is room temperature.
First, the results of measuring electrical parameters of the anode blocks after the anodic oxidation treatment in example 1 and comparative example 1 are shown in table 1.
TABLE 1 Electrical parameters of Anode blocks after anodizing treatment in example 1 and comparative example 1
In the embodiment 1, firstly, nitric acid solution is adopted for oxidation treatment, and then phosphoric acid solution containing hydrogen peroxide is adopted for oxidation treatment; comparative example 1 the oxidation treatment was carried out using only a phosphoric acid solution.
As is clear from comparison between example 1 and comparative example 1, the anodic oxidation method in which oxidation is performed with a nitric acid solution and then with a phosphoric acid solution (containing hydrogen peroxide) enables significant reduction in loss and leakage current after anodic oxidation while maintaining a higher electric capacity, as compared with the oxidation treatment with a phosphoric acid solution alone.
Second, the results of measuring electrical parameters of the anode blocks after the anodic oxidation treatment in example 2 and comparative example 2 are shown in table 2.
TABLE 2 Electrical parameters of the anode blocks after anodizing treatment in example 2 and comparative example 2
In the embodiment 2, firstly, nitric acid solution is adopted for oxidation treatment, and then phosphoric acid solution containing hydrogen peroxide is adopted for oxidation treatment; comparative example 2 the oxidation treatment was carried out using only a nitric acid solution.
As is clear from comparison between example 2 and comparative example 2, the anodic oxidation method in which oxidation is performed with a nitric acid solution and then with a phosphoric acid solution (containing hydrogen peroxide) enables significant reduction in loss and leakage current after anodic oxidation while maintaining a higher electric capacity, as compared with the oxidation treatment with a nitric acid solution alone.
Third, the results of electrical parameter measurements of the anode blocks after the anodic oxidation treatment in examples 3 to 4 and comparative example 3 are shown in table 3.
TABLE 3 Electrical parameters of anode blocks after anodic oxidation treatment in examples 3-4 and comparative example 3
In the embodiment 3, firstly, nitric acid solution is adopted for oxidation treatment, and then phosphoric acid solution containing hydrogen peroxide is adopted for oxidation treatment; in example 4, a nitric acid solution was used for oxidation treatment, and then a phosphoric acid solution containing no hydrogen peroxide was used for oxidation treatment; comparative example 3 the oxidation treatment was carried out using only a nitric acid solution.
It is understood from comparison between examples 3 to 4 and comparative example 3 that the anodic oxidation method in which the oxidation is performed with the nitric acid solution and then with the phosphoric acid solution can significantly reduce the loss and the leakage current after the anodic oxidation while maintaining a higher electric capacity, as compared with the oxidation treatment with the nitric acid solution alone.
As is clear from comparison between example 3 and example 4, in the anodic oxidation method using a nitric acid solution and then a phosphoric acid solution, if the oxidation treatment is performed using a phosphoric acid solution containing hydrogen peroxide in the second-stage oxidation treatment, the loss and the leakage current after the anodic oxidation can be significantly reduced.
Fourth, the results of measuring electrical parameters of the anode blocks after the anodic oxidation treatment in examples 3 and 5 to 6 are shown in table 4.
TABLE 4 Electrical parameters of the anode blocks after anodic oxidation treatment in examples 3 and 5 to 6
The voltage of the step S1 in example 3 is 58.6% of the final formation voltage; the voltage of the step S1 in example 5 is 44.8% of the final formation voltage; the voltage at step S1 in example 6 was 75.9% of the final formation voltage. The voltage multiplying power of the step S1 is the result of rounding off and retaining a decimal fraction.
As can be seen from comparison between example 3 and examples 5-6, in example 5, the voltage multiplying factor of the S1 step is low (lower than 50% of the final forming voltage), and the loss and leakage current after anodic oxidation are large; in example 6, the voltage multiplying factor of the S1 step is higher (higher than 75% of the final forming voltage), and the capacitance after anodization is lower, and the loss and the leakage current are larger.
Fifth, the results of measuring electrical parameters of the anode blocks after the anodic oxidation treatment in examples 3 and 7 to 8 are shown in table 5.
TABLE 5 Electrical parameters of the anode blocks after anodic oxidation treatment in example 3 and examples 7 to 8
The constant pressure maintaining time of step S1 in example 3 was 4 h; the constant pressure maintaining time of step S1 in example 7 was 3 hours; the constant pressure maintaining time of step S1 in example 8 was 5 h.
As is clear from comparison between example 3 and example 7, the voltage holding time in the S1 step is short, and the loss and the leakage current after anodization are slightly large. According to the comparative examples of example 3 and example 8, the constant pressure maintaining time of the step S1 exceeds 4 hours, which only reduces the efficiency and has no practical significance for improving the quality of the dielectric oxide film.
Sixth, the results of measuring electrical parameters of the anode blocks after the anodic oxidation treatment in examples 3 and 9 to 10 are shown in table 6.
TABLE 6 Electrical parameters of the anode blocks after anodic oxidation treatment in example 3 and examples 7 to 8
The constant pressure maintaining time of step S2 in example 3 was 8 h; the constant pressure maintaining time of step S2 in example 9 was 7 h; the constant pressure maintaining time of step S1 in example 10 was 9 h.
As is clear from comparison between example 3 and example 9, the voltage holding time in the S2 step is short, and the loss and the leakage current after anodization are slightly large. From the comparison between example 3 and example 10, it is understood that the constant voltage maintaining time of the step S2 exceeds 8 hours, which only reduces the efficiency and has no practical significance for improving the quality of the dielectric oxide film.
Seventhly, the results of measuring the electrical parameters of the anode blocks after the anodic oxidation treatment in examples 3 and 11 are shown in table 7.
TABLE 7 Electrical parameters of anodized anode blocks of examples 3 and 11
The heat treatment temperature of S3 in example 3 is 400 ℃; the heat treatment temperature of S3 in example 11 is 320 ℃.
As can be seen from the comparison between example 3 and example 11, the heat treatment temperature of the step S3 needs to be increased compared with the standard of 320 ℃ in the prior art, otherwise, the improvement effect on the loss and leakage current after anodic oxidation is affected to a certain extent.
The results of measuring electrical parameters of the anode blocks anodized in example 3 and comparative example 4 are shown in Table 8.
TABLE 8 Electrical parameters of the anode blocks after anodizing in example 3 and comparative example 4
In the embodiment 3, firstly, nitric acid solution is adopted for oxidation treatment, and then phosphoric acid solution containing hydrogen peroxide is adopted for oxidation treatment; in comparative example 4, the oxidation treatment was performed with phosphoric acid containing hydrogen peroxide, and then with a nitric acid solution.
As is clear from comparison between example 3 and comparative example 4, the anodic oxidation method in which oxidation is performed using a nitric acid solution and then using a phosphoric acid solution enables significant reduction in loss and leakage current after anodic oxidation while maintaining a higher capacitance, as compared to the oxidation treatment using a nitric acid solution in which oxidation is performed using a phosphoric acid solution containing hydrogen peroxide.
The embodiments described above are some, but not all embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Claims (10)
1. A method of anodizing an electrolytic capacitor, comprising:
carrying out first-stage oxidation treatment on the anode in a nitric acid solution;
then carrying out second-stage oxidation treatment on the anode in a phosphoric acid solution;
and then the anode is sequentially subjected to heat treatment and complementary formation treatment.
2. The anodic oxidation method according to claim 1, wherein the conductivity of the nitric acid solution at 25 ℃ is 2-15 mS/cm; optionally, the conductivity of the nitric acid solution at 25 ℃ is 2.5-6.5 mS/cm; optionally, the conductivity of the nitric acid solution at 25 ℃ is 7-15 mS/cm;
and/or in the first-stage treatment, the temperature of the nitric acid solution is 35-65 ℃.
3. The anodic oxidation method according to claim 1 or 2, wherein in the first-stage oxidation treatment, the voltage is increased to a first predetermined voltage and then the voltage is kept constant, wherein the boost current density is 70 to 90mA/g, and the first predetermined voltage is 50 to 75% of the final formation voltage of the anodic oxidation;
optionally, the constant pressure time is 1-4 h; optionally, the constant pressure time is 1-2 h; optionally, the constant pressure time is 2-4 h.
4. The anodic oxidation method according to claim 1, wherein in the second-stage oxidation treatment, the phosphoric acid solution contains hydrogen peroxide; optionally, the content of the hydrogen peroxide in the phosphoric acid solution is 0.1-1.5 wt%; optionally, the content of the hydrogen peroxide in the phosphoric acid solution is 0.5-1 wt%.
5. The anodic oxidation method according to claim 4, wherein the conductivity of the phosphoric acid solution at 25 ℃ is 1-10 mS/cm; optionally, the conductivity of the phosphoric acid solution at 25 ℃ is 1-5 mS/cm; optionally, the conductivity of the phosphoric acid solution at 25 ℃ is 5.5-9 mS/cm;
and/or in the second-stage oxidation treatment, the temperature of the phosphoric acid solution is 65-95 ℃; optionally, the temperature of the phosphoric acid solution is 75-90 ℃.
6. The anodic oxidation method according to claim 1, wherein the conductivity of the phosphoric acid solution at 25 ℃ is 1-10 mS/cm; optionally, the conductivity of the phosphoric acid solution at 25 ℃ is 1-5 mS/cm; optionally, the conductivity of the phosphoric acid solution at 25 ℃ is 5.5-9 mS/cm;
and/or in the second-stage oxidation treatment, the temperature of the phosphoric acid solution is 65-95 ℃; optionally, the temperature of the phosphoric acid solution is 75-90 ℃.
7. The anodic oxidation method according to claim 1, 4, 5 or 6, wherein in the second-stage oxidation treatment, the voltage is increased to a second preset voltage and then the voltage is kept constant, wherein the second preset voltage is a final formation voltage of anodic oxidation, and the boosting current density is 50-70 mA/g;
optionally, the constant pressure time is 4-8 h; optionally, the constant pressure time is 4-6 h; optionally, the constant pressure time is 6-8 h.
8. The anodizing method according to claim 1, 4, 5 or 6, wherein in the complementary formation treatment, the anode is subjected to constant-pressure oxidation using the phosphoric acid solution under a final formation voltage condition of the anodic oxidation, and the temperature of the phosphoric acid solution is required to be the same as that in the second-stage oxidation treatment;
optionally, the treatment time is 60-90 min.
9. The anodic oxidation method according to claim 1, wherein the heat treatment is carried out at a temperature of 380 to 420 ℃ for a time of 15 to 30 min.
10. The anodic oxidation method according to claim 1, wherein the anode is made of a valve metal having a specific capacity of 70K μ F-V/g or more.
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Application publication date: 20210730 |