CN114093676A - Sintering method of anode block of tantalum capacitor - Google Patents
Sintering method of anode block of tantalum capacitor Download PDFInfo
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- CN114093676A CN114093676A CN202111342291.9A CN202111342291A CN114093676A CN 114093676 A CN114093676 A CN 114093676A CN 202111342291 A CN202111342291 A CN 202111342291A CN 114093676 A CN114093676 A CN 114093676A
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- 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
Abstract
The invention discloses a sintering method of a tantalum capacitor anode block, which comprises the following steps: (1) loading the anode block to be sintered into a sintering furnace to make the vacuum degree in the furnace less than or equal to 5X 10‑3pa; (2) sintering the first section; (3) sintering in a second section; (4) continuously filling reducing atmosphere into the furnace at the second-stage sintering temperature for a period of time; (5) after the sintering in reducing atmosphere is finished, the vacuum degree in the furnace is less than or equal to 2 multiplied by 10‑2pa, heating to the original temperature at a third heating rate and keeping the temperature constant; (6) when the temperature in the furnace is reduced to below 50 ℃, the mixed atmosphere of oxygen and inert gas is filled into the furnace for multiple times; (7) and when the temperature in the furnace is reduced to the room temperature, cleaning and drying. The method can obtain the sintered anode block with a large-size sintering neck, high charging efficiency and the bulk oxygen content of less than half of the sintering front, thereby manufacturing a more reliable tantalum capacitor product.
Description
Technical Field
The invention relates to the technical field of capacitor manufacturing, in particular to a sintering method of an anode block of a tantalum capacitor.
Background
The high-temperature sintering is a key process in the manufacturing process of the tantalum capacitor, and is used for improving the mechanical property and the purity of the anode block of the tantalum capacitor through high temperature. The sintered tantalum powder particles are connected with each other, the whole anode block is in a porous sponge structure and has a very high surface area, the tantalum pentoxide dielectric layer continuously covers the surfaces of the tantalum powder particles after anodic oxidation to form a structure with a plurality of small capacitors connected in parallel, and the reliability of the tantalum capacitor is determined by the oxygen content of the sintered anode block and the connection strength between the tantalum powder particles.
The traditional sintering process of the anode block of the tantalum capacitor is that under the vacuum or inert atmosphere, the temperature is increased from low temperature to relatively low sintering temperature at a certain rate, the temperature is kept for a certain time at the temperature to remove low-temperature impurities of the anode block, then the temperature is increased to the sintering temperature at a certain rate, the temperature is kept for a certain time, and then the temperature is cooled to room temperature. In the process, under the action of temperature, tantalum powder particles are mutually fused and connected together, so that the whole anode block is in a porous sponge structure, and meanwhile, the anode block can absorb oxygen in the surrounding atmosphere under the action of temperature, so that the oxygen content of the anode block is increased.
The sintering neck is used in the tantalum capacitor industry to represent the connection condition between tantalum powder particles of the sintered anode block, specifically the size of the minimum cross section of an electric path between the tantalum powder particles in the anode block, the sintering neck can be increased by improving the pressing density and the sintering temperature of the anode block, but the pressing density and the sintering temperature of the anode block are improved, so that the micropores in the inner part of the anode block are closed, the electrostatic capacity of the anode block is reduced, the charging efficiency is reduced, and the volume efficiency is reduced.
The oxygen content of the anode block is from oxygen contained in tantalum powder and oxygen absorption in the sintering process of the anode block, at present, manufacturers of tantalum capacitors aim to reduce the oxygen absorption in the sintering process of the anode block, but inevitably, the oxygen content of the anode block after sintering by the sintering process adopted at present is increased, and the oxygen contained in the anode block of the tantalum capacitor promotes crystallization of a dielectric layer of the anode block, so that the higher the oxygen content of the anode block, the poorer the reliability of the anode block is.
Disclosure of Invention
The invention aims to provide a sintering method of an anode block of a tantalum capacitor, which can reduce the bulk oxygen content of the anode block to be less than half of that before sintering under the condition of reducing the sintering temperature of the anode block, thereby improving the reliability of the tantalum capacitor.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a sintering method of a tantalum capacitor anode block, which comprises the following steps:
(1) charging: loading the anode block to be sintered into a sintering furnace, and evacuating the gas in the furnace to make the vacuum degree in the furnace less than or equal to 5X 10- 3pa；
(2) Sintering in the first stage: heating to a first sintering temperature at a first heating rate and keeping the temperature constant;
(3) and (3) second-stage sintering: heating to a second sintering temperature at a second heating rate and keeping the temperature constant;
(4) sintering in a reducing atmosphere: continuously filling reducing atmosphere into the furnace at a second sintering temperature for a period of time;
(5) the method comprises the following steps: after the sintering in reducing atmosphere is finished, the gas in the furnace is evacuated to ensure that the vacuum degree in the furnace is less than or equal to 2 multiplied by 10-2pa, heating to the original temperature at a third heating rate and keeping the temperature constant;
(6) passivation: when the temperature in the furnace is reduced to below 50 ℃, the mixed atmosphere of oxygen and inert gas is filled into the furnace for multiple times;
(7) and (3) cooling: and when the temperature in the furnace is reduced to room temperature, taking the sintered anode block out of the furnace, and carrying out cleaning and drying operation.
The cleaning and drying comprises the following steps:
(1) acid washing: soaking the sintered anode block in dilute acid solution;
(2) boiling and washing: putting the anode block soaked with the dilute acid solution into deionized water at 35-90 ℃ for boiling and washing for 40-120 min;
(3) drying: and (3) putting the boiled anode block into an oven at 65-120 ℃ for drying for 15-40 min.
The first heating rate is 15-25 ℃/min, the first sintering temperature is 300-.
The second heating rate is 20-35 ℃/min, the second sintering temperature is 700-.
The reducing atmosphere is a mixed gas of reducing gas and inert gas, wherein the volume of the reducing gas accounts for 10-50%, and the volume of the inert gas accounts for 50-90%.
The reducing gas is one of magnesium vapor, aluminum vapor or calcium vapor, and the inert gas is one of helium, argon, radon or xenon.
The sintering time of the reducing atmosphere is 20-180min, preferably 50-120min, and the pressure of the reducing atmosphere is 0.002-0.4MPa, preferably 0.02-0.2 MPa.
The third heating rate is 15-30 ℃/min, the present sintering temperature is 1300-1900 ℃, and the constant temperature time is 10-40 min.
The volume of oxygen in the mixed atmosphere accounts for 10-30%, the volume of inert gas accounts for 70-90%, and the inert gas is one of helium, argon, radon or xenon.
The pressure of the mixed atmosphere is 0.01-0.1MPa, the duration of the mixed atmosphere is 30-60S, the interval time is 30-60min, and the repetition times are 3-10.
The diluted acid solution is a mixed solution of inorganic acid, hydrogen peroxide and deionized water, the inorganic acid is one of sulfuric acid, nitric acid or hydrochloric acid, and the soaking time is 60-180 min.
The volume of the inorganic acid in the dilute acid solution is 10-40%, the volume of the hydrogen peroxide is 10-30%, and the balance is deionized water.
The invention has the beneficial effects that: by the method, the sintered anode block with a large-size sintering neck, high charging efficiency and reduced bulk oxygen content to less than half of the original sintering temperature can be obtained under the condition of reducing the original sintering temperature of the anode block, so that a tantalum capacitor product with higher reliability can be manufactured.
Detailed Description
Specific embodiments of the present invention are described further below, but the scope of the claims is not limited thereto.
Example 1
A sintering method of anode blocks of tantalum capacitors comprises the following steps of loading 1000 anode blocks to be sintered of 50V10 mu F tantalum capacitors with the size of 1.7 x 3.5 x 4.8(mm) into a sintering furnace for sintering, wherein the specific sintering process comprises the following steps:
(1) loading the anode block into sintering furnace, evacuating gas in furnace to make vacuum degree in furnace less than or equal to 5X 10-3pa；
(2) Heating to 500 deg.C at 25 deg.C/min, and holding the temperature for 15 min;
(3) heating to 1000 deg.C at 30 deg.C/min, and holding for 10 min;
(4) filling mixed reducing gas of magnesium vapor and argon into the furnace at 1000 ℃, wherein the gas pressure is 0.06MPa, the magnesium vapor accounts for 30 percent and the argon accounts for 70 percent in the mixed gas, and the duration time is 60 min;
(5) stopping filling the mixed gas of magnesium vapor and argon into the furnace at the temperature of 1000 ℃, evacuating the gas in the furnace to ensure that the vacuum degree in the furnace is less than or equal to 2 multiplied by 10-2pa, heating to 1700 ℃ at 30 ℃, and keeping the temperature for 30 min;
(6) when the temperature in the furnace is reduced to below 50 ℃, filling a mixed atmosphere of 20 percent of oxygen and 80 percent of argon into the furnace, wherein the pressure of the mixed atmosphere is 0.02MPa, the duration is 30S, the gas filling interval is 40min each time, and the repeating times are 3 times;
(7) when the temperature in the furnace is reduced to room temperature, taking the sintered anode block out of the furnace;
(8) soaking the sintered anode block in a dilute sulfuric acid solution prepared from 15% of sulfuric acid, 20% of hydrogen peroxide and 65% of deionized water for 60 min;
(9) boiling and washing the anode block soaked with the dilute acid solution for 60min in deionized water at 85 ℃;
(10) baking the boiled anode block in an oven at 85 ℃ for 30 min;
example 2
A sintering method of anode blocks of tantalum capacitors comprises the following steps of loading 1000 anode blocks to be sintered of 10V330 muF tantalum capacitors with the size of 1.7 x 3.5 x 5.0(mm) into a sintering furnace for sintering, wherein the specific sintering process comprises the following steps:
(1) loading the anode block into sintering furnace, evacuating gas in furnace to make vacuum degree in furnace less than or equal to 5X 10-3pa；
(2) Heating to 300 deg.C at 15 deg.C/min, and holding the temperature for 20 min;
(3) heating to 900 deg.C at 20 deg.C/min, and holding the temperature for 15 min;
(4) filling mixed reducing gas of magnesium vapor and argon into the furnace at 900 ℃, wherein the gas pressure is 0.08MPa, the magnesium vapor accounts for 35 percent and the argon accounts for 65 percent in the mixed gas, and the duration time is 90 min;
(5) stopping filling the mixed gas of magnesium vapor and argon into the furnace at 900 ℃, evacuating the gas in the furnace to ensure that the vacuum degree in the furnace is less than or equal to 2 multiplied by 10-2pa, heating to 1350 ℃ at 25 ℃, and keeping the temperature for 20 min;
(6) when the temperature in the furnace is reduced to below 50 ℃, filling a mixed atmosphere of 20 percent oxygen and 80 percent argon into the furnace, wherein the pressure of the mixed atmosphere is 0.02MPa, the duration is 60S, the gas filling interval is 60min each time, and the times are 6;
(7) when the temperature in the furnace is reduced to room temperature, taking the sintered anode block out of the furnace;
(8) soaking the sintered anode block in a dilute sulfuric acid solution prepared from 15% of sulfuric acid, 20% of hydrogen peroxide and 65% of deionized water for 90 min;
(9) boiling and washing the anode block soaked with the dilute acid solution for 60min in deionized water at 85 ℃;
(10) and baking the boiled anode block in an oven at 85 ℃ for 30 min.
Comparative example 1
In the existing sintering method of the anode block of the tantalum capacitor, 1000 anode blocks to be sintered of the 50V10 mu F tantalum capacitor with the size of 1.7X 3.5X 4.8(mm) are put into a sintering furnace for sintering, and the specific sintering process comprises the following steps:
(1) loading the anode block into sintering furnace, evacuating gas in furnace to make vacuum degree in furnace less than or equal to 5X 10-3pa；
(2) Heating to 500 deg.C at 25 deg.C/min, and holding the temperature for 15 min;
(3) heating to 1000 deg.C at 30 deg.C/min, and holding for 10 min;
(4) heating to 1700 ℃ at 30 ℃, and keeping the temperature for 30 min;
(5) and cooling, and taking the sintered anode block out of the furnace when the temperature in the furnace is reduced to room temperature.
Oxygen content of the sintered anode block was measured using an oxygen-nitrogen-hydrogen combination tester, the sintered neck size of the anode block was measured using a scanning electron microscope, and the charging efficiency of the sintered anode block was measured using a test-volume method, and the oxygen content, the sintered neck size, and the charging efficiency of the anode blocks of example 1 and comparative example 1 were compared as in table 1 below.
TABLE 1 comparison of oxygen content, sintering neck and charging efficiency of anode blocks of example 1 and comparative example 1
Comparative example 2
In the existing sintering method of the anode block of the tantalum capacitor, 1000 anode blocks to be sintered of the 10V330 muF tantalum capacitor with the size of 1.7 x 3.5 x 5.0(mm) are put into a sintering furnace for sintering, and the specific sintering process comprises the following steps:
(1) loading the anode block into sintering furnace, evacuating gas in furnace to make vacuum degree in furnace less than or equal to 5X 10-3pa；
(2) Heating to 300 deg.C at 15 deg.C/min, and holding the temperature for 20 min;
(3) heating to 900 deg.C at 20 deg.C/min, and holding the temperature for 15 min;
(4) heating to 1350 deg.C at 25 deg.C, and holding for 20 min;
(5) and cooling, and taking the sintered anode block out of the furnace when the temperature in the furnace is reduced to room temperature.
Oxygen content of the sintered anode block was measured using an oxygen-nitrogen-hydrogen combination tester, the sintered neck size of the anode block was measured using a scanning electron microscope, and the charging efficiency of the sintered anode block was measured using a test-volume method, and the oxygen content, the sintered neck size, and the charging efficiency of the anode blocks of example 2 and comparative example 2 were compared as in table 2 below.
Table 2 comparison of oxygen content, sintering neck and charging efficiency of anode blocks of example 2 and comparative example 2
As can be seen from the data in tables 1 and 2, the tantalum capacitor anode block sintered by the method is sintered and passivated by reducing atmosphere, compared with the tantalum capacitor anode block sintered by the conventional sintering process, the tantalum capacitor anode block has larger sintering neck size, higher charging efficiency and lower bulk oxygen content, and the bulk oxygen content is reduced to less than half of that before sintering.
Claims (10)
1. A sintering method of an anode block of a tantalum capacitor is characterized by comprising the following steps:
(1) charging: loading the anode block to be sintered into a sintering furnace, and evacuating the gas in the furnace to make the vacuum degree in the furnace less than or equal to 5X 10-3pa；
(2) Sintering in the first stage: heating to a first sintering temperature at a first heating rate and keeping the temperature constant;
(3) and (3) second-stage sintering: heating to a second sintering temperature at a second heating rate and keeping the temperature constant;
(4) sintering in a reducing atmosphere: continuously filling reducing atmosphere into the furnace at a second sintering temperature for a period of time;
(5) the method comprises the following steps: after the sintering in reducing atmosphere is finished, the gas in the furnace is evacuated to ensure that the vacuum degree in the furnace is less than or equal to 2 multiplied by 10-2pa, heating to the original temperature at a third heating rate and keeping the temperature constant;
(6) passivation: when the temperature in the furnace is reduced to below 50 ℃, the mixed atmosphere of oxygen and inert gas is filled into the furnace for multiple times;
(7) and (3) cooling: and when the temperature in the furnace is reduced to room temperature, taking the sintered anode block out of the furnace, and carrying out cleaning and drying operation.
2. The method for sintering an anode block for a tantalum capacitor according to claim 1, wherein said cleaning and drying operation comprises the steps of:
(1) acid washing: soaking the sintered anode block in dilute acid solution;
(2) boiling and washing: putting the anode block soaked with the dilute acid solution into deionized water at 35-90 ℃ for boiling and washing for 40-120 min;
(3) drying: and (3) putting the boiled anode block into an oven at 65-120 ℃ for drying for 15-40 min.
3. The method for sintering the anode block for the tantalum capacitor as claimed in claim 2, wherein the reducing atmosphere is a mixed gas of a reducing gas and an inert gas, wherein the volume of the reducing gas is 10-50% and the volume of the inert gas is 50-90%.
4. The method of claim 3, wherein the reducing gas is one of magnesium vapor, aluminum vapor or calcium vapor, and the inert gas is one of helium, argon, radon or xenon.
5. The method for sintering the anode block for the tantalum capacitor as claimed in claim 4, wherein the sintering time in the reducing atmosphere is 20 to 180min, and the pressure in the reducing atmosphere is 0.002 to 0.4 MPa.
6. The method of claim 2, wherein the third temperature-raising rate is 15-30 ℃/min, the sintering temperature is 1300-1900 ℃, and the constant temperature time is 10-40 min.
7. The method for sintering the anode block of the tantalum capacitor as claimed in claim 2, wherein the mixed atmosphere comprises 10-30% by volume of oxygen and 70-90% by volume of inert gas, and the inert gas is one of helium, argon, radon or xenon.
8. The method for sintering the anode block of the tantalum capacitor as claimed in claim 7, wherein the pressure of the mixed atmosphere is 0.01-0.1MPa, the duration of each filling of the mixed atmosphere is 30-60S, the interval time is 30-60min, and the repetition time is 3-10 times.
9. The method for sintering the anode block of the tantalum capacitor as claimed in claim 2, wherein the diluted acid solution is a mixed solution of inorganic acid, hydrogen peroxide and deionized water, the inorganic acid is one of sulfuric acid, nitric acid or hydrochloric acid, and the soaking time is 60-180 min.
10. The method of sintering an anode block for a tantalum capacitor of claim 9, wherein said dilute acid solution comprises 10-40% by volume of inorganic acid, 10-30% by volume of hydrogen peroxide, and the balance of deionized water.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002013998A1 (en) * | 2000-08-10 | 2002-02-21 | Cabot Supermetals K.K. | Method for manufacturing tantalum sintered object for electrolytic capacitor |
| CN102773478A (en) * | 2012-07-10 | 2012-11-14 | 中国振华（集团）新云电子元器件有限责任公司 | Sintering method for improving mechanical strength of tantalum block |
| CN112457026A (en) * | 2020-12-14 | 2021-03-09 | 江西科技学院 | Copper calcium titanate ceramic reduction-oxidation atmosphere co-sintering method |
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2021
- 2021-11-12 CN CN202111342291.9A patent/CN114093676B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002013998A1 (en) * | 2000-08-10 | 2002-02-21 | Cabot Supermetals K.K. | Method for manufacturing tantalum sintered object for electrolytic capacitor |
| CN102773478A (en) * | 2012-07-10 | 2012-11-14 | 中国振华（集团）新云电子元器件有限责任公司 | Sintering method for improving mechanical strength of tantalum block |
| CN112457026A (en) * | 2020-12-14 | 2021-03-09 | 江西科技学院 | Copper calcium titanate ceramic reduction-oxidation atmosphere co-sintering method |
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