Powder sintered tantalum electrolytic capacitor anode and method of making same

Abstract

The application discloses a powder sintering type tantalum electrolytic capacitor anode and a preparation method thereof, and belongs to the technical field of tantalum electrolytic capacitors. The preparation method of the powder sintering type tantalum electrolytic capacitor anode is as follows: a dielectric substance is used to coat tantalum powder to obtain dielectric substance-coated tantalum powder; the dielectric constant of the dielectric substance is greater than the dielectric constant of dittantalum pentoxide; the dielectric substance-coated tantalum powder, a binder and a solvent are uniformly mixed to obtain slurry, the slurry is dried to remove the solvent and mixed powder is obtained; the mixed powder is pressed and shaped, subjected to a degreasing treatment, then sintered in an oxygen-free atmosphere, and after sintering, the powder sintering type tantalum electrolytic capacitor anode is obtained by energization. The high dielectric constant substance is introduced into the tantalum electrolytic capacitor, the dielectric constant of the composite dielectric layer is increased, the static capacity is effectively improved, and the device failure problem of the tantalum electrolytic capacitor powder accumulation sintering block in the preparation process due to the crystallization of the dielectric layer is relieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tantalum electrolytic capacitor, more particularly to a powder sintering type tantalum electrolytic capacitor anode and a preparation method thereof. BACKGROUND

[0002] Capacitors play an important role in circuits such as filtering, rectification, coupling, decoupling, bypass, etc. Large-capacity electrolytic capacitors have the performance of storing electric energy, charging and discharging, allowing AC resistance to block DC, etc. Aluminum electrolytic capacitors are generally used in consumer electronics, household appliances, industrial control, etc. due to their low price, high rated voltage, and the advantage of being able to be used at low frequencies. However, the service life of aluminum electrolytic capacitors is short, they are prone to aging, and their performance reliability decreases year by year; they are greatly affected by the environment, and their service life is halved for every 10℃ increase in temperature; and if they are not used for a long time and suddenly subjected to rated voltage, they are prone to failure, damage, or even explosion.

[0003] Tantalum electrolytic capacitors have high energy density, long service life, high insulation resistance, small leakage current, wide temperature range, and high reliability, and are widely used in military communication, aerospace, industrial control, video equipment, communication instruments, etc. With the continuous development of the modularization and integration of equipment and instruments, there is an increasing demand for the miniaturization of electronic components, and it is urgent to reduce the size of tantalum electrolytic capacitors. The voltage and current resistance of tantalum electrolytic capacitors is limited, and when used at high voltage or high current, it is prone to cause thermal runaway or fire, hindering the development of the electronics industry. The root cause is that the oxide crystalline defects in the dielectric weaken the amorphous dielectric, providing a conductive path, which leads to short-circuiting between the positive and negative electrodes of the tantalum electrolytic capacitor, resulting in thermal runaway or fire. SUMMARY

[0004] To solve the above problems, the present application provides a powder sintering type tantalum electrolytic capacitor anode and a preparation method thereof. In order to improve the static capacity of the tantalum electrolytic capacitor block anode and reduce the size of the tantalum electrolytic capacitor, the present application proposes coating a high dielectric constant material on the surface of tantalum powder, and after sintering and energizing, a high dielectric composite tantalum electrolytic capacitor block anode is formed. The introduction of high dielectric constant material in the tantalum electrolytic capacitor increases the dielectric constant of the composite dielectric layer, effectively improves its static capacity, and alleviates the device failure problem caused by crystallization of the dielectric layer during the preparation process of the powder sintering block tantalum electrolytic capacitor.

[0005] A preparation method of a powder sintering type tantalum electrolytic capacitor anode, comprising the following steps:

[0006] The tantalum powder is coated with dielectric substance to obtain dielectric substance coated tantalum powder; the dielectric constant of the dielectric substance is greater than the dielectric constant of the tantalum pentoxide;

[0007] The dielectric substance coated tantalum powder, the binder and the solvent are mixed uniformly to obtain a slurry, and the slurry is dried to remove the solvent to obtain a mixed powder;

[0008] After the mixed powder is pressed and shaped, the slurry is subjected to a debinding treatment at 100-550 DEG C, and then sintered at 1200-2000 DEG C in an oxygen-free atmosphere to obtain a powder sintered tantalum block. Then, the block is energized to obtain a powder sintered tantalum block anode for electrolytic capacitors.

[0009] For example, the debinding temperature is 100 DEG C, 130 DEG C, 150 DEG C, 190 DEG C, 210 DEG C, 250 DEG C, 290 DEG C, 310 DEG C, 350 DEG C, 390 DEG C, 410 DEG C, 450 DEG C, 490 DEG C, 510 DEG C, 550 DEG C, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0010] The sintering temperature is 1200 DEG C, 1300 DEG C, 1400 DEG C, 1500 DEG C, 1600 DEG C, 1700 DEG C, 1800 DEG C, 1900 DEG C, 2000 DEG C, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0011] In a preferred embodiment of the present application, the slurry is composed of the following components in the following mass percentages: 40-80% of dielectric substance coated tantalum powder, 0.1-10% of binder, and the rest is solvent, and the total is 100%. For example, the proportion of dielectric substance coated tantalum powder is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., the proportion of binder is 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. The proportion of solvent is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 59.9%, etc. But not limited to the listed values, and other values not listed in the above value range are also applicable.

[0012] In a preferred embodiment of the present application, the debinding temperature is 5 DEG C / min-10 DEG C / min, and the reaction time is 10 min-120 min. For example, the debinding time is 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0013] In a preferred embodiment of the present invention, the heating rate during sintering is 5°C / min to 10°C / min, and the reaction time is 10 min to 120 min. For example, the sintering time can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc., but is not limited to the listed values; other unlisted values ​​within the above range are also applicable. The sintering atmosphere is any one or more of a vacuum atmosphere, an argon atmosphere, a nitrogen atmosphere, and a hydrogen atmosphere.

[0014] In a preferred embodiment of the present invention, the dielectric material is one or more of titanium dioxide, hafnium oxide, tantalum nitride, niobium oxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate, and bismuth ferrite. The particle size of the dielectric material is 0.1 nm to 500 nm.

[0015] In a preferred embodiment of the present invention, the specific volume of tantalum powder is 1000 μF·V / g to 150000 μF·V / g. For example, the specific volume of tantalum powder is 1000 μF·V / g, 3000 μF·V / g, 9000 μF·V / g, 10000 μF·V / g, 30000 μF·V / g, 50000 μF·V / g, 90000 μF·V / g, 110000 μF·V / g, 130000 μF·V / g, 150000 μF·V / g, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0016] In a preferred embodiment of the present invention, the binder is one or more selected from polyvinyl alcohol, urea, polymethyl methacrylate, methyl methacrylate, polystyrene, polyvinyl chloride, stearic acid, glycerin, polyethylene glycol, paraffin wax, camphor, menthol, benzoic acid, polyethylene oxide, hydroxypropyl cellulose, acrylic resin, polypropylene carbonate, polyvinyl butyral, and propylene carbonate.

[0017] The dispersant is water, methanol, ethanol, terpineol, acetonitrile, acetone, dimethylformamide, N-methylpyrrolidone, n-butanol or methyl ethyl ketone.

[0018] During drying, drying can be carried out at 50-200℃, and the drying atmosphere can be any one or more of the following: vacuum atmosphere, air atmosphere, argon atmosphere, and nitrogen atmosphere.

[0019] In a preferred embodiment of the present invention, the compaction density is 5 g / cm³ during the briquetting and shaping step. 3 ~10g / cm 3 For example, a compacted density of 5 g / cm³ 3 6g / cm 3 7g / cm3 8 g / cm 3 9 g / cm 3 10 g / cm 3 and the like, but are not limited to the listed values, and other unlisted values within the above ranges are also applicable.

[0020] In a preferred embodiment of the present application, the coating method is liquid immersion coating, gas phase deposition coating or solid mixing coating. Further, the gas phase coating method is chemical vapor deposition, atomic layer deposition, molecular layer deposition, fluidized bed method, magnetron sputtering method; the liquid phase coating method is sol-gel method; and the solid mixing coating method is dry mixing or wet mixing of tantalum powder and nano-sized high dielectric constant powder.

[0021] A second object of the present application is to provide a powder sintered tantalum electrolytic capacitor anode prepared by the above preparation method.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The present application uses dielectric material to coat tantalum powder as raw material, and after the introduction of dielectric material, subsequent high temperature and energizing treatment, the introduction of dielectric material effectively prevents local overheating and excessive local current, effectively alleviates the crystallization phenomenon of tantalum pentoxide, and effectively improves the dielectric constant of the bulk anode. Therefore, the introduction of dielectric material in the tantalum electrolytic capacitor powder accumulation sintered bulk not only can improve the capacitance of the anode foil, reduce the volume of the tantalum electrolytic capacitor, but also can alleviate the device failure problem caused by the crystallization phenomenon of the dielectric layer. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Schematic diagram of solid mixing coated tantalum powder sintering.

[0025] Figure 2 Schematic diagram of ALD gas phase coated tantalum powder.

[0026] Figure 3 Tantalum powder accumulation diagram during sintering.

[0027] Reference signs: 1-aluminum powder, 2-dielectric material. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] The failure mechanism of tantalum electrolytic capacitor is largely because the oxide crystalline defects in the dielectric weaken the amorphous dielectric, providing a conductive channel, thus causing the short circuit of the positive and negative poles of the tantalum electrolytic capacitor, and causing thermal runaway or fire. The anodic oxide film (Ta2O5) formed by the energy provided is an amorphous structure, but due to local overheating and excessive local current (due to oxide film defects such as pits and cracks), the activation energy for the reaction is provided, driving ions to overcome the potential barrier and reorder from amorphous to crystalline structure. Based on this, in the preparation of the bulk anode for tantalum electrolytic capacitor, a dielectric substance is introduced for doping, and after high-temperature heat treatment and energy is provided, a high-dielectric composite dielectric layer is formed, which increases the dielectric constant of the composite dielectric layer and effectively improves the static capacity, and alleviates the device failure problem caused by crystallization of the dielectric layer during the preparation of the tantalum electrolytic capacitor powder sintered bulk.

[0030] The specific technical solutions are as follows:

[0031] The tantalum powder is coated with a dielectric substance to obtain dielectric substance-coated tantalum powder. It can be understood that the thickness of the dielectric constant substance coating is 0.1-30 nm.

[0032] The dielectric substance-coated tantalum powder, a binder and a solvent are mixed uniformly to obtain a slurry, and the slurry is dried to remove the solvent to obtain a mixed powder.

[0033] After the mixed powder is pressed and shaped, it is subjected to a debinding treatment at 100-450 DEG C, and then sintered at 1200-2000 DEG C to undergo micro-melting, to obtain a powder sintered tantalum bulk. It should be noted that the powder sintered tantalum bulk prepared according to the preparation method of the present application is a high-dielectric powder sintered tantalum bulk formed by coating the tantalum powder with a high-dielectric substance.

[0034] During the pressing and shaping process, if the compaction density is too high, the tantalum powder will be deformed, and if the compaction density is too low, it will not be easy to shape.

[0035] During the debinding process, if the debinding temperature is too low, the binder will carbonize, resulting in an increase in leakage current, and if the debinding temperature is too high, a thermal oxide film will be formed, and the excessive thickness of the thermal oxide film will result in a decrease in static capacity.

[0036] During the sintering process, if the sintering temperature is too low, powder loss will occur, and if the sintering temperature is too high, the specific surface area will decrease, resulting in a decrease in static capacity.

[0037] If a small amount of dielectric substance is introduced, the improvement effect is not obvious, and a large amount of introduction will affect sintering.

[0038] Example 1

[0039] (1) The tantalum powder with a specific capacity of 8000 μF·V / g and a purity of 99.95% and barium titanate with a particle size of 2 nm were mixed uniformly at a mass ratio of 95:5 to obtain dielectric substance-coated tantalum powder.

[0040] (2) The dielectric substance-coated tantalum powder, camphor and anhydrous ethanol were mixed uniformly at a mass percentage of 65%, 5% and 30% respectively to obtain a slurry.

[0041] (3) The slurry prepared in step (2) was dried at 80°C in an air atmosphere for 30 min to obtain a mixed powder.

[0042] (4) The mixed powder prepared in step (3) was pressed and shaped in a mold, and the compacted density was 7 g / cm 3 , to obtain a block, the thickness of which was 1 mm and the area was 2 cm 2 .

[0043] (5) The block prepared in step (4) was debound at 130°C in an air atmosphere for 1 h, and sintered at 1400°C in a vacuum atmosphere for 30 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0044] Comparative Example 1

[0045] (1) The tantalum powder with a specific capacity of 8000 μF·V / g and a purity of 99.95%, camphor and anhydrous ethanol were mixed uniformly at a mass ratio of 65:5:30 to obtain a slurry.

[0046] (2) The slurry prepared in step (1) was dried at 80°C in an air atmosphere for 30 min to obtain a mixed powder.

[0047] (3) The mixed powder prepared in step (2) was pressed and shaped in a mold, and the compacted density was 7 g / cm 3 , to obtain a block, the thickness of which was 1 mm and the area was 2 cm 2 .

[0048] (4) The block prepared in step (3) was debound at 130°C in an air atmosphere for 1 h by increasing the temperature at a rate of 10°C, and sintered at 1400°C in a vacuum atmosphere for 30 min by increasing the temperature at a rate of 10°C to obtain a sintered block for a tantalum electrolytic capacitor.

[0049] Example 2

[0050] (1) The tantalum powder with a specific capacity of 50000 μF·V / g and a purity of 99.95% and barium titanate with a particle size of 2 nm were mixed uniformly at a mass ratio of 95:5 to obtain dielectric substance-coated tantalum powder.

[0051] (2) The dielectric substance-coated tantalum powder, camphor and anhydrous ethanol were mixed uniformly at a mass percentage of 65%, 5% and 30% respectively to obtain a slurry.

[0052] (3) The slurry prepared in step (2) is dried at 80°C in air atmosphere for 30 min to obtain a mixed powder.

[0053] (4) The mixed powder prepared in step (3) is pressed into a block in a mold, and the compaction density is 7 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 2 cm 2 .

[0054] (5) The block prepared in step (4) is debinded at a temperature rising rate of 10°C to 130°C in air atmosphere for 1 h, and sintered at a temperature rising rate of 10°C to 1400°C in vacuum atmosphere for 30 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0055] Comparative Example 2

[0056] (1) Tantalum powder with a specific capacity of 50000 μF·V / g and a purity of 99.95%, camphor, and anhydrous ethanol are mixed uniformly according to a mass ratio of 65:5:30 to obtain a slurry.

[0057] (2) The slurry prepared in step (1) is dried at 80°C in air atmosphere for 30 min to obtain a mixed powder.

[0058] (3) The mixed powder prepared in step (2) is pressed into a block in a mold, and the compaction density is 4.9 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 2 cm 2 .

[0059] (4) The block prepared in step (3) is debinded at a temperature rising rate of 10°C to 130°C in air atmosphere for 1 h, and sintered at a temperature rising rate of 10°C to 1400°C in vacuum atmosphere for 30 min to obtain a sintered block for a tantalum electrolytic capacitor.

[0060] Example 3

[0061] (1) Tantalum powder with a specific capacity of 8000 μF·V / g and a purity of 99.95% is placed in an ALD reaction cavity with a temperature of 200°C and a vacuum degree of 5 mTorr, nitrogen gas is used as a carrier gas, isopropyl titanate is used as a titanium source, the temperature of the titanium source is kept at 25°C, and the titanium source is introduced for 5 s, and then nitrogen gas is introduced for 30 s for purging. Then O3 is introduced for 10 s, and then nitrogen gas is introduced for 50 s for purging. The above steps are repeated for 200 times to obtain dielectric substance-coated tantalum powder.

[0062] (2) 65% of the dielectric substance-coated tantalum powder, 5% of camphor, and 30% of anhydrous ethanol are weighed according to the mass percentage and mixed uniformly to obtain a slurry.

[0063] (3) The slurry prepared in step (2) is dried at 80°C in air atmosphere for 30 min to obtain a mixed powder.

[0064] (4) The mixed powder prepared in step (3) is pressed into a block in a special mold, and the compaction density is 4.9 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 2 cm 2 .

[0065] (5) The block prepared in step (4) is debound at a temperature rising rate of 10°C to 130°C in air atmosphere for 1 h, and sintered at a temperature rising rate of 10°C to 1400°C in vacuum atmosphere for 30 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0066] Example 4

[0067] (1) The tantalum powder with a specific capacity of 8000 μF·V / g and a purity of 99.95% is placed in an ALD reaction cavity with a temperature of 200°C and a vacuum degree of 5 mTorr, and titanium isopropoxide is used as the titanium source, the temperature of the titanium source is kept at 25°C, nitrogen gas is introduced for 5 s, and then nitrogen gas is introduced for 30 s. Then O3 is introduced for 10 s, and then nitrogen gas is introduced for 50 s. According to the above steps, the thickness of the deposited tantalum powder is 5 nm, and the dielectric material is obtained.

[0068] (2) The dielectric material-coated tantalum powder, camphor and anhydrous ethanol are mixed in a mass percentage of 65%, 5% and 30% respectively to obtain a slurry.

[0069] (3) The slurry prepared in step (2) is dried at 80°C in air atmosphere for 30 min to obtain a mixed powder.

[0070] (4) The mixed powder prepared in step (3) is pressed into a block in a special mold, and the compaction density is 4.9 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 2 cm 2 .

[0071] (5) The block prepared in step (4) is debound at a temperature rising rate of 10°C to 130°C in air atmosphere for 1 h, and sintered at a temperature rising rate of 10°C to 1400°C in vacuum atmosphere for 30 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0072] Example 5

[0073] (1) Put the tantalum powder with a specific capacitance of 50000 μF·V / g and a purity of 99.95% into an ALD reaction cavity with a temperature of 200°C and a vacuum degree of 5 mTorr, use nitrogen as a carrier gas, use isopropyl titanate as a titanium source, keep the temperature of the titanium source at 25°C, pass in for 5 s, then pass in nitrogen for 30 s for purging. Then pass in O3 for 10 s, and then pass in nitrogen for 50 s for purging. Repeat the deposition according to the above steps, and deposit a thickness of 2 nm to obtain dielectric substance-wrapped tantalum powder.

[0074] (2) Take 65% dielectric substance-wrapped tantalum powder, 5% camphor and 30% anhydrous ethanol according to the mass percentage, and mix them uniformly to obtain a slurry.

[0075] (3) Dry the slurry prepared in step (2) at 80°C in an air atmosphere for 30 min to obtain a mixed powder.

[0076] (4) Press the mixed powder prepared in step (3) into a block in a specially designed mold, and the compaction density is 4.9 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 2 cm 2 .

[0077] (5) The block prepared in step (4) is debound in an air atmosphere at a temperature rising rate of 10°C to 130°C for 1 h, and then sintered in a vacuum atmosphere at a temperature rising rate of 10°C to 1400°C for 30 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0078] Example 6

[0079] (1) Put the tantalum powder with a specific capacitance of 50000 μF·V / g and a purity of 99.95% into an ALD reaction cavity with a temperature of 200°C and a vacuum degree of 5 mTorr, use nitrogen as a carrier gas, use isopropyl titanate as a titanium source, keep the temperature of the titanium source at 25°C, pass in for 5 s, then pass in nitrogen for 30 s for purging. Then pass in O3 for 10 s, and then pass in nitrogen for 50 s for purging. Repeat the deposition according to the above steps, and deposit a thickness of 5 nm to obtain dielectric substance-wrapped tantalum powder.

[0080] (2) Take 65% dielectric substance-wrapped tantalum powder, 5% camphor and 30% anhydrous ethanol according to the mass percentage, and mix them uniformly to obtain a slurry.

[0081] (3) Dry the slurry prepared in step (2) at 80°C in an air atmosphere for 30 min to obtain a mixed powder.

[0082] (4) Press the mixed powder prepared in step (3) into a block in a specially designed mold, and the compaction density is 4.9 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 2 cm 2 .

[0083] (5) The block prepared in step (4) is debinded in air atmosphere at a temperature increasing rate of 10°C to 450°C for 10 min, and sintered in vacuum atmosphere at a temperature increasing rate of 10°C to 1200°C for 120 min to obtain a sintered block of powder sintered tantalum electrolytic capacitor.

[0084] Example 7

[0085] (1) Tantalum powder with specific capacitance of 150000 μF·V / g and purity of 99.95% and tantalum nitride with particle size of 2 nm are mixed uniformly at a mass ratio of 80:20 to obtain dielectric substance-coated tantalum powder.

[0086] (2) 40% of the dielectric substance-coated tantalum powder, 10% of urea and 50% of acetone are weighed according to the mass percentage and mixed uniformly to obtain a slurry.

[0087] (3) The slurry prepared in step (2) is dried at 200°C in argon atmosphere for 20 min to obtain a mixed powder.

[0088] (4) The mixed powder prepared in step (3) is pressed and shaped in a mold to obtain a block with a compacted density of 8 g / cm 3 , a thickness of 1 mm and an area of 2 cm 2 .

[0089] (5) The block prepared in step (4) is debinded in air atmosphere at a temperature increasing rate of 10°C to 450°C for 10 min, and sintered in vacuum atmosphere at a temperature increasing rate of 10°C to 1200°C for 120 min to obtain a sintered block of powder sintered tantalum electrolytic capacitor.

[0090] Example 8

[0091] (1) Tantalum powder with specific capacitance of 30000 μF·V / g and purity of 99.95% and niobium oxide with particle size of 2 nm are mixed uniformly at a mass ratio of 70:30 to obtain dielectric substance-coated tantalum powder.

[0092] (2) 40% of the dielectric substance-coated tantalum powder, 10% of a composite binder and 50% of n-butanol are weighed according to the mass percentage and mixed uniformly to obtain a slurry, wherein the composite binder is obtained by mixing polyethylene glycol with a molecular weight of 4000 and polyvinyl alcohol with a molecular weight of 120000 at a mass ratio of 2:3.

[0093] (3) The slurry prepared in step (2) is dried at 50°C in vacuum atmosphere for 1 h to obtain a mixed powder.

[0094] (4) The mixed powder prepared in step (3) is pressed and shaped in a mold to obtain a block with a compacted density of 8 g / cm 3 , a thickness of 1 mm and an area of 2 cm2 .

[0095] (5) The block prepared in step (4) is debinded in air atmosphere at a temperature increasing rate of 10°C to 250°C for 50 min, and sintered in vacuum atmosphere at a temperature increasing rate of 10°C to 2000°C for 10 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0096] Example 9

[0097] (1) Tantalum powder with a specific volume of 30000 μF·V / g and a purity of 99.95% is mixed with barium strontium titanate with a particle size of 30 nm at a mass ratio of 70:30 to obtain dielectric substance-coated tantalum powder.

[0098] (2) 80% of the dielectric substance-coated tantalum powder, 10% of the composite binder, and 10% of water are weighed according to the mass percentage, and mixed uniformly to obtain a slurry, wherein the composite binder is obtained by mixing urea, stearic acid, and glycerol at a mass ratio of 2:3.

[0099] (3) The slurry prepared in step (2) is dried at 50°C under vacuum atmosphere for 1 h to obtain a mixed powder.

[0100] (4) The mixed powder prepared in step (3) is pressed and shaped in a mold to obtain a block with a compacted density of 8 g / cm 3 , a thickness of 2 mm, and an area of 2 cm 2 .

[0101] (5) The block prepared in step (4) is debinded in air atmosphere at a temperature increasing rate of 10°C to 250°C for 50 min, and sintered in vacuum atmosphere at a temperature increasing rate of 10°C to 1800°C for 15 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0102] Example 10

[0103] (1) Tantalum powder with a specific volume of 30000 μF·V / g and a purity of 99.95% is mixed with barium strontium titanate with a particle size of 0.1 nm at a mass ratio of 80:20 to obtain dielectric substance-coated tantalum powder.

[0104] (2) 40% of the dielectric substance-coated tantalum powder, 0.1% of the composite binder, and 59.9% of methanol are weighed according to the mass percentage, and mixed uniformly to obtain a slurry, wherein the composite binder is obtained by mixing polystyrene and polyvinyl chloride at a mass ratio of 2:3, the molecular weight of polystyrene is 60000, and the molecular weight of polyvinyl chloride is 100000.

[0105] (3) The slurry prepared in step (2) is dried at 50°C under vacuum atmosphere for 1 h to obtain a mixed powder.

[0106] (4) The mixed powder prepared in step (3) is pressed into a block in a mold, and the compaction density is 8 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 2 cm 2 .

[0107] (5) The block prepared in step (4) is debinded in an air atmosphere at a temperature increasing rate of 5°C to 550°C for 50 min, and sintered in an argon atmosphere at a temperature increasing rate of 5°C to 1500°C for 50 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0108] Example 11

[0109] (1) Tantalum powder with a specific capacity of 5000 μF·V / g and a purity of 99.95% is mixed with barium strontium titanate with a particle size of 2 nm at a mass ratio of 80:20 to obtain dielectric substance-coated tantalum powder.

[0110] (2) 40% dielectric substance-coated tantalum powder, 0.1% composite binder, and 59.9% N-methyl pyrrolidone are weighed according to the mass percentage and mixed uniformly to obtain a slurry, wherein the composite binder is obtained by mixing paraffin, menthol, and benzoic acid at a mass ratio of 1:1:1.

[0111] (3) The slurry prepared in step (2) is dried at 50°C in a vacuum atmosphere for 1 h to obtain a mixed powder.

[0112] (4) The mixed powder prepared in step (3) is pressed into a block in a mold, and the compaction density is 8 g / cm 3 , to obtain a block, the thickness of the block is 1 mm, and the area is 3 cm 2 .

[0113] (5) The block prepared in step (4) is debinded in an air atmosphere at a temperature increasing rate of 10°C to 130°C for 120 min, and sintered in a vacuum atmosphere at a temperature increasing rate of 10°C to 2000°C for 10 min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0114] Example 12

[0115] (1) Tantalum powder with a specific capacity of 5000 μF·V / g and a purity of 99.95% is mixed with lead zirconium titanate with a particle size of 6 nm at a mass ratio of 80:20 to obtain dielectric substance-coated tantalum powder.

[0116] (2) Take 55% dielectric substance wrapped tantalum powder, 5% composite binder and 40% terpineol by mass percentage, mix uniformly to obtain slurry, wherein the composite binder is obtained by mixing polyethylene oxide, hydroxypropyl cellulose and acrylic resin in a mass ratio of 2:2:1, the molecular weight of polyethylene oxide is 10000, the molecular weight of hydroxypropyl cellulose is 40000, and the molecular weight of acrylic resin is 80000.

[0117] (3) Dry the slurry prepared in step (2) at 50°C under vacuum atmosphere for 1h to obtain a mixed powder.

[0118] (4) Press the mixed powder prepared in step (3) into a block in a mold to shape, and the compaction density is 8g / cm 3 , to obtain a block, the thickness of the block is 1mm, and the area is 2cm 2 .

[0119] (5) The block prepared in step (4) is heated to 450°C in air atmosphere at a heating rate of 8°C for 10min, and then heated to 2000°C in vacuum atmosphere at a heating rate of 8°C for 10min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0120] Example 13

[0121] (1) Mix 5000μF·V / g specific volume, 99.95% purity tantalum powder and dielectric substance in a mass ratio of 80:20 to obtain dielectric substance wrapped tantalum powder, wherein the dielectric substance is obtained by mixing niobium oxide and hafnium oxide in a mass ratio of 1:1.

[0122] (2) Take 50% dielectric substance wrapped tantalum powder, 10% composite binder and 40% acetonitrile by mass percentage, mix uniformly to obtain slurry, wherein the composite binder is obtained by mixing polymethyl methacrylate, polypropylene carbonate and polyvinyl butyral in a mass ratio of 2:2:1, the molecular weight of polymethyl methacrylate is 100000, the molecular weight of polypropylene carbonate is 280000, and the molecular weight of polyvinyl butyral is 40000.

[0123] (3) Dry the slurry prepared in step (2) at 50°C under vacuum atmosphere for 1h to obtain a mixed powder.

[0124] (4) Press the mixed powder prepared in step (3) into a block in a mold to shape, and the compaction density is 5g / cm 3 , to obtain a block, the thickness of the block is 1mm, and the area is 2cm 2 .

[0125] (5) The block prepared in step (4) is debinded in a vacuum atmosphere at a temperature increasing rate of 10℃ to 130℃ for 90min, and sintered in a nitrogen atmosphere at a temperature increasing rate of 10℃ to 1200℃ for 10min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0126] Example 14

[0127] (1) The tantalum powder with a specific capacity of 5000μF·V / g and a purity of 99.95% is mixed with the dielectric substance at a mass ratio of 70:30 to obtain dielectric substance coated tantalum powder, wherein the dielectric substance is obtained by mixing lead zirconate titanate and bismuth ferrite at a mass ratio of 1:1.

[0128] (2) 70% of the dielectric substance coated tantalum powder, 9% of the composite binder and 21% of N,N'-dimethylformamide are weighed according to the mass percentage and mixed uniformly to obtain a slurry, wherein the composite binder is obtained by mixing methyl methacrylate and propylene carbonate at a mass ratio of 2:1.

[0129] (3) The slurry prepared in step (2) is dried at 100℃ in a vacuum atmosphere for 20min to obtain a mixed powder.

[0130] (4) The mixed powder prepared in step (3) is pressed and shaped in a mold to obtain a block with a compacted density of 10g / cm 3 , wherein the thickness of the block is 2mm and the area is 3cm 2 .

[0131] (5) The block prepared in step (4) is debinded in a nitrogen atmosphere at a temperature increasing rate of 5℃ to 250℃ for 50min, and sintered in a vacuum atmosphere at a temperature increasing rate of 5℃ to 2000℃ for 10min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0132] Example 15

[0133] (1) The tantalum powder with a specific capacity of 5000μF·V / g and a purity of 99.95% is mixed with bismuth ferrite with a particle size of 500nm at a mass ratio of 70:30 to obtain dielectric substance coated tantalum powder.

[0134] (2) 40% of the dielectric substance coated tantalum powder, 0.1% of glycerol and 59.9% of methyl ethyl ketone are weighed according to the mass percentage and mixed uniformly to obtain a slurry.

[0135] (3) The slurry prepared in step (2) is dried at 200℃ in a vacuum atmosphere for 20min to obtain a mixed powder.

[0136] (4) The mixed powder prepared in step (3) is pressed and shaped in a mold to obtain a block with a compacted density of 10g / cm 3, to obtain a block, the thickness of the block is 0.8mm, the area is 2cm 2 .

[0137] (5) the block prepared in step (4) is debinded in air atmosphere at a temperature increasing rate of 5℃ to 100℃ for 24h, and sintered in hydrogen atmosphere at a temperature increasing rate of 5℃ to 1200℃ for 60min to obtain a powder sintered tantalum electrolytic capacitor sintered block.

[0138] The powder sintered tantalum electrolytic capacitor sintered blocks prepared in examples 1-6 and comparative examples 1-2 are subjected to energizing treatment, i.e. chemical conversion treatment in a phosphoric acid system solution to obtain powder sintered tantalum electrolytic capacitor anodes. Specifically, the chemical conversion solution is prepared by mixing 2 volumes of 0.07mol / L aqueous phosphoric acid solution with 1 volume of ethylene glycol at a volume ratio of 2:1, and then adding 0.15wt% of citric acid based on the total mass of the chemical conversion solution. The chemical conversion current density is 3mAg -1 .

[0139] Table 1: Test results of tantalum capacitor sintered foils

[0140] Experiment Electrostatic capacity (μF·V / g) V f (V) Example 1 7123 180 Comparative Example 1 6935 175 Example 2 45684 64 Comparative Example 2 42012 61 Example 3 7256 184 Example 4 7334 190 Example 5 46679 66 Example 6 47692 68

[0141] As can be seen from Table 1, compared with the static capacitance and voltage resistance of the pure tantalum powder tantalum block anodes in the comparative examples, the static capacitance and voltage resistance of the high dielectric constant tantalum block anodes prepared from the high dielectric constant coated tantalum powder in examples 1-6 are both significantly improved, which indicates that the introduction of the dielectric substance, after high temperature heat treatment and energizing, effectively improves the dielectric constant of the block anode and suppresses the crystallization of the tantalum pentoxide. When the crystallization is serious, the dielectric layer is not dense and the voltage resistance performance is poor. The high dielectric constant tantalum block anodes prepared by the gas phase coating method in comparative example 1 and example 3 are obviously superior to the high dielectric constant tantalum block anodes prepared by mixing high dielectric constant powder, which indicates that the high dielectric constant layer prepared by the gas phase coating method is more dense and the suppression of the crystallization of the tantalum pentoxide is more obvious.

[0142] Although preferred embodiments of the application have been described, a person of ordinary skill in the art can make additional changes and modifications to these embodiments once the basic inventive concept is known. Therefore, the appended claims are intended to be interpreted as including all changes and modifications falling within the scope of the application.

[0143] Obviously, various modifications and changes can be made to the present application by those skilled in the art without departing from the spirit and scope of the present application. Thus, it is intended that the present application encompass all such modifications and changes as fall within the scope of the appended claims and their equivalents.

Claims

1. A method for preparing the anode of a powder-sintered tantalum electrolytic capacitor, characterized in that, Includes the following steps: Tantalum powder is coated with a dielectric material to obtain tantalum powder coated with dielectric material; the dielectric constant of the dielectric material is greater than that of tantalum pentoxide; the dielectric material is one or more of titanium dioxide, hafnium oxide, tantalum nitride, niobium oxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate, and bismuth ferrite. A slurry is obtained by uniformly mixing tantalum powder, binder, and solvent with a dielectric material, and then drying the slurry to remove the solvent to obtain a mixed powder. After the mixed powder is pressed into blocks and shaped, it is degreased at 100℃~550℃, and then sintered at 1200℃~2000℃ in an oxygen-free atmosphere. After sintering, the powder-sintered tantalum electrolytic capacitor anode is obtained by energizing. The degreasing reaction time is 10min~120min. The sintering reaction time is 10min~120min.

2. The method for preparing the anode of a powder-sintered tantalum electrolytic capacitor according to claim 1, characterized in that, The slurry is composed of the following components by mass percentage: 40%~80% tantalum powder coated with dielectric material, 0.1%~10% binder, and the remainder is solvent, totaling 100%.

3. The method for preparing the anode of a powder-sintered tantalum electrolytic capacitor according to claim 1, characterized in that, The specific volume of tantalum powder is 1000 μF·V / g to 150000 μF·V / g.

4. The method for preparing the anode of a powder-sintered tantalum electrolytic capacitor according to claim 1, characterized in that, The binder is one or more of the following: polyvinyl alcohol, urea, polymethyl methacrylate, polystyrene, polyvinyl chloride, stearic acid, glycerin, polyethylene glycol, paraffin wax, camphor, menthol, benzoic acid, polyethylene oxide, hydroxypropyl cellulose, acrylic resin, polypropylene carbonate, polyvinyl butyral, and propylene carbonate.

5. The method for preparing the anode of a powder-sintered tantalum electrolytic capacitor according to claim 1, characterized in that, In the briquetting and shaping process, the compaction density is 5 g / cm³. 3 ~10g / cm 3 .

6. The method for preparing the anode of a powder-sintered tantalum electrolytic capacitor according to claim 1, characterized in that, The coating methods include liquid phase impregnation coating, vapor phase deposition coating, or solid mixed coating.

7. An anode of a powder-sintered tantalum electrolytic capacitor prepared by the preparation method according to any one of claims 1-6.

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