A method for manufacturing a tantalum capacitor low-carbon content anode body

Abstract

The application discloses a manufacturing method of a tantalum capacitor low-carbon-content anode body, and comprises the following steps: S1, powder mixing: a certain proportion of PVP and anhydrous glucose are weighed and dissolved in a solvent, sieved tantalum powder is added into the solvent, the PVP and the anhydrous glucose form a composite binder, the composite binder and the tantalum powder are heated and mixed, the solvent is volatilized completely, then the tantalum powder is sieved, and the tantalum powder is sealed and stored in a container filled with inert gas; S2, pressing forming: the tantalum powder mixed with the composite binder is pressed into a tantalum blank with a required shape and size at a certain speed and pressure maintaining time; S3, removing the composite binder: the formed tantalum blank is soaked in a hydrogen peroxide aqueous solution, heated and stirred to dissolve and remove the composite binder component, then the tantalum blank is put into pure water to rinse and remove residues, and then the tantalum blank is heated and dried at a certain temperature and time; and S4, vacuum sintering: the tantalum blank from which the composite binder is removed is sintered in a high-temperature high-vacuum environment, and a low-carbon-content anode body is sintered; the carbon content of the tantalum blank is low, and the leakage current is smaller.

Description

Technical Field

[0001] This invention relates to the field of tantalum capacitor manufacturing, and more specifically to a method for manufacturing a low-carbon content anode for tantalum capacitors. Background Technology

[0002] Tantalum capacitors are widely used in aerospace, shipbuilding, weaponry, and automotive electronics due to their high volumetric efficiency and reliability. The quality of the dielectric oxide film is a key factor determining the reliability of tantalum capacitors, and the composition and structural integrity of the dielectric oxide film are important criteria for evaluating its quality. Tantalum capacitor manufacturing typically involves pressing powder into a porous anode body, followed by sintering. Then, an electrochemical method is used to form a tantalum pentoxide dielectric oxide film on the surface of the anode body's pores, and finally, a cathode material is coated onto the surface of the dielectric oxide film. During the dielectric oxide film formation process, impurities from the anode surface become trapped within the dielectric oxide film, occupying positions that should be occupied by tantalum pentoxide. Theoretically, the tantalum pentoxide dielectric oxide film is an insulator, and its insulation level determines the reliability of the tantalum capacitor. Impurities reduce the insulation of the dielectric oxide film and also become stress concentration points, reducing its ability to withstand electrical, thermal, or vibration stresses. Therefore, tantalum powder and capacitor manufacturers strictly control the impurity content of both the tantalum powder and the anode body. Impurities in capacitor-grade tantalum powder are mainly oxygen, nitrogen, hydrogen, carbon, silicon, phosphorus, iron, nickel, chromium, magnesium, niobium, etc. Nitrogen and phosphorus can be added as beneficial components. Except for oxygen, the other harmful elements are controlled within 50 ppm. Carbon is a recognized harmful element, and its content in tantalum powder is generally less than 50 ppm.

[0003] In the anode manufacturing process, an organic binder is first mixed into the tantalum powder to improve its flowability, reduce friction during the molding process, and increase the porosity of the anode. Camphor is a commonly used binder. After the tantalum powder is formed, the camphor in the tantalum blank is removed by heating, and then it is sintered at high temperature and high vacuum.

[0004] Camphor has several drawbacks as a binder: First, camphor is prone to sublimation and is unstable, which has adverse effects on the stability of tantalum powder and molten tantalum blanks, the health of operators, and the environment. Second, the fluidity of tantalum powder is not significantly improved after camphor is mixed, which affects the weight consistency of the molten tantalum blanks. Third, the effect of removing camphor by heating is not ideal. At low temperatures, the carbon residue is high, and at high temperatures, the oxygen content increases, making it difficult to reconcile. In particular, when the specific volume of tantalum powder reaches above 50K, the carbon residue can be as high as 200ppm or more. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for manufacturing a low-carbon content anode for tantalum capacitors.

[0006] The present invention is achieved through the following technical solutions.

[0007] The technical solution of the present invention: A method for manufacturing a low-carbon content anode body for a tantalum capacitor, comprising the following steps: S1: Mixing powder: Weigh out a certain proportion of PVP and anhydrous glucose and dissolve them in a solvent. Add sieved tantalum powder to the solvent. PVP and anhydrous glucose form a composite binder and are heated and mixed with tantalum powder. After the solvent has evaporated completely, sieve the mixture and then store it in a container filled with inert gas. S2: Compression molding: Pressing tantalum powder mixed with composite binder into tantalum blanks of the required shape and size at a certain speed and holding time; S3: Removal of composite binder: The formed tantalum blank is immersed in an aqueous hydrogen peroxide solution, heated and stirred to dissolve and remove the composite binder components, then rinsed in pure water to remove residues, and then dried at a certain temperature and time. S4: Vacuum sintering: The tantalum blank after removing the composite binder is sintered in a high temperature and high vacuum environment to produce an anode with low carbon content.

[0008] Preferably, in step S1, 0.1% to 10% by weight of PVP and 0.1% to 10% by weight of anhydrous glucose are weighed.

[0009] Preferably, in step S1, the solution is pure water or an organic solution, and the purity of the pure water or organic solution is greater than 99.6%.

[0010] Preferably, in step S1, the ratio of tantalum powder dissolved in the solvent is 100g tantalum powder: 1ml to 50ml solvent.

[0011] Preferably, in step S1, the tantalum powder is sieved using a 20-mesh to 100-mesh screen.

[0012] Preferably, in S2, the single-sided dimension of the tantalum blank ranges from 0.1 mm to 10 cm.

[0013] Preferably, in step S3, the concentration of the hydrogen peroxide aqueous solution is 1% to 90%, and the purity is greater than 99.6%.

[0014] Preferably, in step S2, the die head moving speed during pressing is 0.01 mm / s to 10 mm / s, and the holding time is 1 ms to 10 min.

[0015] Preferably, in step S4, the vacuum degree inside the furnace before heating is ≤1.0×10⁻⁶. -2 Pa, the vacuum degree inside the furnace during sintering is ≤4.0×10 Pa. -2 Pa, where the sintering temperature process is divided into: Stage 1: room temperature → T1, heating rate 0.5℃ / min~100℃ / min; T1 temperature range is 100℃~500℃, T1 is constant temperature for 1min~120min; Phase 2: T1→T2, heating rate 0.5℃ / min~100℃ / min; T2 temperature range 500℃~1000℃, T2 constant temperature 1min~120min; Phase 3: T2→T3, heating rate 0.5℃ / min~100℃ / min; T3 temperature range 1000℃~1400℃, T3 constant temperature 1min~120min; Stage 4: T3→T4, heating rate 0.5℃ / min~100℃ / min; T4 temperature range 1200℃→1450℃, constant temperature 1min~120min; Phase 5: T4 → T5. After the temperature is maintained at T4, the furnace is cooled to T5, which ranges from 100℃ to 1000℃. The vacuum level inside the furnace between T4 and T5 is ≤1.0×10⁻⁶. -3 Pa; Stage Six: T5→T6. At T5, argon gas with a purity greater than 99.9% is introduced into the furnace until the furnace pressure is -80kPa to 0Pa. At T6, the temperature is 0℃ to 100℃. When the temperature reaches T6, the tantalum billet is taken out of the sintering furnace to obtain a low-carbon anode.

[0016] The beneficial effects of this invention are: 1. The addition of composite binder improves the fluidity of tantalum powder. PVP has good film-forming properties. After dissolution and release, it is coated on the surface of tantalum powder in the form of a thin film, which has a pelletizing effect. The fluidity of tantalum powder is significantly improved after mixing. 2. After mixing with PVP, the fluidity of tantalum powder is significantly improved, the supply is smooth during the molding process, and anhydrous glucose, as a small molecule organic compound, plays a good lubricating role in the molding process, which can effectively reduce the friction between tantalum powder and mold, improve the service life of mold, and improve the weight consistency of the molded tantalum billet. 3. PVP and anhydrous glucose are used as binder components. During the dissolution and removal process, the aqueous solution can penetrate deep into the interior of the tantalum blank to dissolve the binder components. Anhydrous glucose has better solubility in water than PVP, and will preferentially dissolve and precipitate out, forming preliminary channels to facilitate further dissolution and precipitation of PVP. 4. The tantalum billet has a low carbon content, resulting in fewer defects in the dielectric oxide film, which reduces the probability of electrons passing through and reduces leakage current. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0019] Example 1 Experimental group 1 S1: Mixed powder. Tantalum powder has a nominal specific volume of 32000 μF·V / g. The weight of tantalum powder is 1 kg, and the weight of PVP is 15 g. No anhydrous glucose is added, and the amount of anhydrous ethanol is 75 ml. PVP is added to anhydrous ethanol and dissolved using a magnetic stirrer at room temperature at 30 rpm for 10 min. The tantalum powder is then sieved through a 40-mesh standard sieve. The binder solution is then added and stirred until homogeneous at 60℃ for 60 min at a stirring speed of 8 rpm. After mixing, the mixture is sieved through a 40-mesh sieve and then stored in a container filled with argon gas.

[0020] S2: Compression molding. An automatic compression molding machine is used to compress tantalum powder into square tantalum blanks with dimensions of 1.8mm × 3.4mm × 4.9mm. Each square tantalum blank weighs 180mg, and the compression density is 6g / cm³. 3 The die head moving speed during pressing is 0.5mm / s, and the holding time is 20ms.

[0021] S3: Remove the binder without anhydrous glucose. Immerse the tantalum blank in a 5% (v / v) hydrogen peroxide aqueous solution and stir to separate the composite binder from the tantalum blank. The temperature of the hydrogen peroxide aqueous solution is 65℃, the stirring speed is 30r / min, and the stirring time is 90min. Then rinse the tantalum blank in pure water at 85℃ for 50min. After rinsing, dry the tantalum blank in an oven at 100℃ for 60min under normal atmospheric pressure.

[0022] S4: High-temperature high-vacuum sintering After removing the binder containing anhydrous glucose, the tantalum billet is placed in an oven for high-temperature, high-vacuum sintering. Before heating, the vacuum level inside the oven is ≤1.0×10⁻⁶. -2 Pa, the process is as follows: Stage 1: Room temperature → T1. After maintaining room temperature for 10 minutes, the furnace temperature is increased at a rate of 20℃ / min. The temperature of T1 is 300℃, which is then maintained for 10 minutes. During the heating and holding process, the vacuum degree is ≤6.0×10⁻⁶. -3 Pa.

[0023] Stage 2: T1→T2, heating rate 25℃ / min, T2 temperature 800℃, hold at 800℃ for 10min, vacuum degree ≤5.0×10 during heating and holding process. -3 Pa.

[0024] Stage 3: T2→T3, heating rate 30℃ / min, temperature of T3 is 1200℃; after reaching 1200℃, hold the temperature for 10 minutes, vacuum degree ≤4.0×10 during heating and holding. -3 Pa.

[0025] Stage 4: T3→T4, heating rate 30℃ / min, temperature of T4 is 1450℃, and the temperature is held at 1450℃ for 30 minutes.

[0026] Stage 5: T4→T5, naturally cooled in the furnace to 400℃. The temperature of T5 is 400℃, and the vacuum degree during the cooling process is ≤6.0×10. -4 Pa.

[0027] Stage 6: T5→T6, at 300℃, argon gas with a purity greater than 99.99% is introduced into the furnace until the furnace pressure is 0Pa. When the furnace temperature drops to 40℃, the furnace is first evacuated to 0kPa, and then air is slowly introduced into the furnace. The tantalum billet is then taken out of the sintering furnace to obtain a low-carbon anode.

[0028] Control group 1 S1: Mixed powder. Tantalum powder has a nominal specific volume of 32000 μF·V / g. The weight of tantalum powder is 1 kg, the weight of camphor is 15 g, and the amount of anhydrous ethanol is 75 ml. Add camphor to anhydrous ethanol and dissolve it using a magnetic stirrer at room temperature at a stirring speed of 30 r / min for 10 min. Sift the tantalum powder through a 40-mesh standard sieve, then add the binder solution and stir until homogeneous. The stirring temperature is 60℃, the stirring time is 60 min, and the stirring speed is 8 r / min. After mixing, sieve through a 40-mesh sieve and then store in a container filled with argon gas.

[0029] S2: Compression molding. An automatic compression molding machine is used to compress tantalum powder into square tantalum blanks with dimensions of 1.8mm × 3.4mm × 4.9mm. Each square tantalum blank weighs 180mg, and the compression density is 6g / cm³. 3 The die head moving speed during pressing is 0.5mm / s, and the holding time is 20ms.

[0030] S3: Remove camphor. Place the molded blank in an oven and heat it to remove camphor. The heating rate is 2℃ / min. Heat it to 150℃ and hold it at that temperature for 150min. After the holding time is over, cool it down to below 50℃ and take it out.

[0031] S4: High-temperature high-vacuum sintering After camphor removal, the tantalum billet is placed in a furnace for high-temperature, high-vacuum sintering. Before heating, the vacuum level inside the furnace is ≤1.0×10⁻⁶. -2 Pa, the process is as follows: Stage 1: Room temperature → T1. After maintaining room temperature for 10 minutes, the furnace temperature is increased at a rate of 15℃ / min. The temperature of T1 is 300℃, which is then maintained for 15 minutes. During the heating and holding process, the vacuum degree is ≤7.0×10⁻⁶. -3 Pa.

[0032] Stage 2: T1→T2, T2 temperature is 800℃, the heating rate during the process of rising to T2 is 20℃ / min, the temperature is held at 800℃ for 15min, and the vacuum degree during the heating and holding process is ≤6.5×10 -3 Pa.

[0033] Stage 3: T2→T3, heating rate 25℃ / min, temperature of T3 is 1200℃; after reaching 1200℃, hold at that temperature for 15min, vacuum degree ≤4.5×10 during heating and holding. -3 Pa.

[0034] Stage 4: T3→T4, heating rate 30℃ / min, temperature of T4 is 1350℃, and the temperature is held at 1350℃ for 30 minutes.

[0035] Stage 5: T4→T5, naturally cooled in the furnace to 300℃. The temperature of T5 is 300℃, and the vacuum degree during the cooling process is ≤6.0×10. -4 Pa.

[0036] Stage 6: T5→T6, at 300℃, argon gas with a purity greater than 99.99% is introduced into the furnace until the furnace pressure is 0Pa. When the furnace temperature drops to 35℃, the furnace is first evacuated to -80kPa, and then air is slowly introduced into the furnace. The tantalum billet is then taken out of the sintering furnace to obtain the corresponding anode body.

[0037] The following table shows the comparison results of relevant data between experimental group 1 and control group 1.

[0038] Table 1 Example 2 Experimental group 2 Specifically, the following steps are included: S1: Mixing powders. Tantalum powder has a nominal specific volume of 50000 μF·V / g, and the weight of tantalum powder is 1 kg. The weight of PV is 15 g, the weight of anhydrous glucose is 5 g, and the weight of pure water is 100 ml. Add 15 g of PVP and 5 g of anhydrous glucose to pure water and stir with a magnetic stirrer at room temperature until dissolved. The stirring speed is 30 r / min, and the stirring time is 15 min.

[0039] The tantalum powder is then sieved through a 40-mesh standard sieve, and then a solution containing a composite binder is added and stirred to make it evenly mixed. The stirring temperature is 85℃, the stirring time is 60 minutes, and the stirring speed is 8 r / min. After mixing, the mixture is sieved through a 40-mesh sieve and then stored in a container filled with argon gas.

[0040] S2: Compression molding. An automatic compression molding machine is used to compress tantalum powder into square tantalum blanks with a volume of 3mm × 3.5mm × 5mm. Each square tantalum blank weighs 283.5mg and has a compression density of 5.4g / cm³. 3 The die head moving speed during pressing is 0.3 mm / s, and the holding time is 30 ms.

[0041] S3: Remove the composite adhesive. Immerse the tantalum blank in a 10% (v / v) hydrogen peroxide aqueous solution and stir to dissolve and precipitate the composite adhesive from the tantalum blank. The temperature of the hydrogen peroxide aqueous solution is 65℃, the stirring speed is 30 r / min, and the stirring time is 100 min. Then rinse the tantalum blank in pure water at 85℃ for 60 min. After rinsing, dry the tantalum blank in an oven at 100℃ for 60 min under normal atmospheric pressure.

[0042] S4: High-temperature high-vacuum sintering After removing the composite binder, the tantalum billet is placed in an oven for high-temperature, high-vacuum sintering. Before heating, the vacuum level inside the oven is ≤1.0×10⁻⁶. -2 Pa, the process is as follows: Stage 1: Room temperature → T1. After maintaining room temperature for 10 minutes, the furnace temperature is increased at a rate of 15℃ / min. The temperature of T1 is 300℃, which is then maintained for 15 minutes. During the heating and holding process, the vacuum degree is ≤7.0×10⁻⁶. -3 Pa.

[0043] Stage 2: T1→T2, T2 temperature is 800℃, the heating rate during the process of rising to T2 is 20℃ / min, the temperature is held at 800℃ for 15min, and the vacuum degree during the heating and holding process is ≤6.5×10 -3 Pa.

[0044] Stage 3: T2→T3, heating rate 25℃ / min, temperature of T3 is 1200℃; after reaching 1200℃, hold at that temperature for 15min, vacuum degree ≤4.5×10 during heating and holding. -3 Pa.

[0045] Stage 4: T3→T4, heating rate 30℃ / min, temperature of T4 is 1350℃, and the temperature is held at 1350℃ for 30 minutes.

[0046] Stage 5: T4→T5, naturally cooled in the furnace to 300℃. The temperature of T5 is 300℃, and the vacuum degree during the cooling process is ≤6.0×10. -4 Pa.

[0047] Stage 6: T5→T6, at 300℃, argon gas with a purity greater than 99.99% is introduced into the furnace until the furnace pressure is 0Pa. When the furnace temperature drops to 35℃, the furnace is first evacuated to -80kPa, and then air is slowly introduced into the furnace. The tantalum billet is then taken out of the sintering furnace to obtain a low-carbon anode.

[0048] Control group 2 S1: Mixed powder. The nominal specific volume of tantalum powder is 50000 μF·V / g, the weight of tantalum powder is 1 kg, the weight of camphor is 20 g, and the weight of anhydrous ethanol is 100 ml. Add camphor to anhydrous ethanol and dissolve it using a magnetic stirrer at room temperature at 30 r / min for 10 min. Sift the tantalum powder through a 40-mesh standard sieve, then add the binder solution and stir until homogeneous. The stirring temperature is 60℃, the stirring time is 60 min, and the stirring speed is 8 r / min. After mixing, sieve through a 40-mesh sieve and then store in a container filled with argon gas.

[0049] S2: Compression molding. An automatic compression molding machine is used to compress tantalum powder into square tantalum blanks with a volume of 3mm × 3.5mm × 5mm. Each square tantalum blank weighs 283.5mg and has a compression density of 5.4g / cm³. 3 The die head moving speed during pressing is 0.3 mm / s, and the holding time is 30 ms.

[0050] S3: Remove camphor. Place the molded blank in an oven and heat it to remove camphor. The heating rate is 2℃ / min. Heat it to 150℃ and hold it at that temperature for 150min. After the holding time is over, cool it down to below 50℃ and take it out.

[0051] S4: High-temperature high-vacuum sintering After camphor removal, the tantalum billet is placed in a furnace for high-temperature, high-vacuum sintering. Before heating, the vacuum level inside the furnace is ≤1.0×10⁻⁶. -2 Pa, the process is as follows: Stage 1: Room temperature → T1. After maintaining room temperature for 10 minutes, the furnace temperature is increased at a rate of 15℃ / min. The temperature of T1 is 300℃, which is then maintained for 15 minutes. During the heating and holding process, the vacuum degree is ≤7.0×10⁻⁶. -3 Pa.

[0052] Stage 2: T1→T2, T2 temperature is 800℃, the heating rate during the process of rising to T2 is 20℃ / min, the temperature is held at 800℃ for 15min, and the vacuum degree during the heating and holding process is ≤6.5×10 -3 Pa.

[0053] Stage 3: T2→T3, heating rate 25℃ / min, temperature of T3 is 1200℃; after reaching 1200℃, hold at that temperature for 15min, vacuum degree ≤4.5×10 during heating and holding. -3 Pa.

[0054] Stage 4: T3→T4, heating rate 30℃ / min, temperature of T4 is 1350℃, and the temperature is held at 1350℃ for 30 minutes.

[0055] Stage 5: T4→T5, naturally cooled in the furnace to 300℃. The temperature of T5 is 300℃, and the vacuum degree during the cooling process is ≤6.0×10. -4 Pa.

[0056] Stage 6: T5→T6, at 300℃, argon gas with a purity greater than 99.99% is introduced into the furnace until the furnace pressure is 0Pa. When the furnace temperature drops to 35℃, the furnace is first evacuated to -80kPa, and then air is slowly introduced into the furnace. The tantalum billet is then taken out of the sintering furnace to obtain the corresponding anode body.

[0057] The following table shows the comparison results of relevant data between experimental group 2 and control group 2.

[0058] Table 2 Example 3 Experimental group 3 S1: Mixed powders. Tantalum powder has a nominal specific volume of 70000 μF·V / g. The weight of tantalum powder is 1 kg, the weight of PVP is 20 g, the weight of anhydrous glucose is 5 g, and the weight of pure water is 125 ml. PVP and anhydrous glucose are added to pure water and dissolved using a magnetic stirrer at room temperature at 30 rpm for 20 min. The tantalum powder is then sieved through a 40-mesh standard sieve. The composite binder solution is then added and stirred until homogeneous at 85℃ for 80 min at a stirring speed of 8 rpm. After mixing, the mixture is sieved through a 40-mesh sieve and then stored in a container filled with argon gas.

[0059] S2: Compression molding. An automatic compression molding machine is used to compress tantalum powder into square tantalum blanks with a volume of 3mm × 3.5mm × 5mm. Each square tantalum blank weighs 283.5mg and has a compression density of 5.4g / cm³. 3 The die head moving speed during pressing is 0.2 mm / s, and the holding time is 40 ms.

[0060] S3: Remove the composite binder by immersing the tantalum blank in a 15% (v / v) hydrogen peroxide aqueous solution and stirring to dissolve and precipitate the composite binder from the tantalum blank. The temperature of the hydrogen peroxide aqueous solution is 65℃, the stirring speed is 30 r / min, and the stirring time is 120 min. Then, rinse the tantalum blank in pure water at 85℃ for 70 min. After rinsing, dry the tantalum blank in an oven at 100℃ for 80 min under atmospheric pressure.

[0061] S4: High-temperature high-vacuum sintering After removing the composite binder, the tantalum billet is placed in an oven for high-temperature, high-vacuum sintering. Before heating, the vacuum level inside the oven is ≤1.0×10⁻⁶. -2 Pa, the process is as follows: Phase 1: From room temperature to T1, after holding at room temperature for 10 minutes, the furnace temperature is increased at a rate of 10℃ / min; the temperature of T1 is 300℃, and after reaching 300℃, it is held constant for 20 minutes. During both the heating and holding periods, the vacuum degree is ≤9.0×10⁻⁻¹. 3 Pa.

[0062] Phase 2: T1→T2, T2 temperature is 800℃, the heating rate during the process of rising to T2 is 15℃ / min, the temperature is held at 800℃ for 20min, and the vacuum degree during the heating and holding process is ≤8.0×10- 3 Pa.

[0063] Stage 3: T2→T3, heating rate 20℃ / min, temperature of T3 is 1200℃; after reaching 1200℃, hold at that temperature for 20min, vacuum degree ≤5.0×10- during heating and holding. 3 Pa.

[0064] Stage 4: T3→T4, heating rate 30℃ / min, temperature of T4 is 1300℃, and the temperature is held at 1300℃ for 30 minutes.

[0065] Stage 5: T4→T5, naturally cooled in the furnace to 000℃, the temperature of T5 is 200℃, and the vacuum degree during the cooling process is ≤6.0×10 -4 Pa.

[0066] Stage 6: T5→T6, at 300℃, argon gas with a purity greater than 99.99% is introduced into the furnace until the furnace pressure is 0Pa. When the furnace temperature drops to 25℃, the furnace is first evacuated to -80kPa, and then air is slowly introduced into the furnace. The tantalum billet is then taken out of the sintering furnace to obtain a low-carbon anode.

[0067] Control group 3 S1: Mixed powder. The nominal specific volume of tantalum powder is 70000 μF·V / g, the weight of tantalum powder is 1 kg, the weight of camphor is 25 g, and the weight of anhydrous ethanol is 125 ml. Add camphor to anhydrous ethanol and dissolve it using a magnetic stirrer at room temperature at 30 r / min for 10 min. Sift the tantalum powder through a 40-mesh standard sieve, then add the binder solution and stir until homogeneous. The stirring temperature is 60℃, the stirring time is 60 min, and the stirring speed is 8 r / min. After mixing, sieve through a 40-mesh sieve and then store in a container filled with argon gas.

[0068] S2: Press molding. The tantalum powder is pressed into square tantalum blanks with a volume of 3mm×3.5mm×5mm using an automatic pressing molding machine. The weight of each square tantalum blank is 283.5mg, the pressing density is 5.4g / cm3, the die head moving speed during pressing is 0.2mm / s, and the holding time is 40ms.

[0069] S3: Remove camphor. Place the molded blank in an oven and heat it to remove camphor. The heating rate is 2℃ / min. Heat it to 150℃ and hold it at that temperature for 150min. After the holding time is over, cool it down to below 50℃ and take it out.

[0070] S4: The camphor-free tantalum billet is placed in a furnace for high-temperature, high-vacuum sintering. The vacuum degree inside the furnace before heating is ≤1.0×10⁻⁶. -2 Pa, the process is as follows: Phase 1: From room temperature to T1, after holding at room temperature for 10 minutes, the furnace temperature is increased at a rate of 10℃ / min; the temperature of T1 is 300℃, and after reaching 300℃, it is held constant for 20 minutes. During both the heating and holding periods, the vacuum degree is ≤9.0×10⁻⁻¹. 3 Pa.

[0071] Phase 2: T1→T2, T2 temperature is 800℃, the heating rate during the process of rising to T2 is 15℃ / min, the temperature is held at 800℃ for 20min, and the vacuum degree during the heating and holding process is ≤8.0×10- 3 Pa.

[0072] Stage 3: T2→T3, heating rate 20℃ / min, temperature of T3 is 1200℃; after reaching 1200℃, hold at that temperature for 20min, vacuum degree ≤5.0×10- during heating and holding. 3 Pa.

[0073] Stage 4: T3→T4, heating rate 30℃ / min, temperature of T4 is 1300℃, and the temperature is held at 1300℃ for 30 minutes.

[0074] Stage 5: T4→T5, naturally cooled in the furnace to 000℃, the temperature of T5 is 200℃, and the vacuum degree during the cooling process is ≤6.0×10 -4 Pa.

[0075] Stage 6: T5→T6, at 300℃, argon gas with a purity greater than 99.99% is introduced into the furnace until the furnace pressure is 0Pa. When the furnace temperature drops to 25℃, the furnace is first evacuated to -80kPa, and then air is slowly introduced into the furnace. The tantalum billet is then taken out of the sintering furnace to obtain a low-carbon anode.

[0076] The following table shows the comparison results of relevant data between experimental group 3 and control group 3:

[0077] Table 3 In summary, based on the comparative tests of the three embodiments, the addition of composite binder improved the flowability of tantalum powder by 12.06% to 14.06%, reducing the standard deviation of the heavy deviation of the molded powder by 47.93% to 61.71%; the removal of composite binder reduced carbon residue by 65.26% to 83.81%, resulting in a reduction of leakage current by 26.83% to 45.83%.

[0078] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the content of the present invention under the concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing a low-carbon content anode body for a tantalum capacitor, characterized in that, Includes the following steps: S1: Mixing powder: Weigh out a certain proportion of PVP and anhydrous glucose and dissolve them in a solvent. Add sieved tantalum powder to the solvent. PVP and anhydrous glucose form a composite binder and are heated and mixed with tantalum powder. After the solvent has evaporated completely, sieve the mixture and then store it in a container filled with inert gas. S2: Compression molding: Pressing tantalum powder mixed with composite binder into tantalum blanks of the required shape and size at a certain speed and holding time; S3: Removal of composite binder: The formed tantalum blank is immersed in an aqueous hydrogen peroxide solution, heated and stirred to dissolve and remove the composite binder components, then rinsed in pure water to remove residues, and then dried at a certain temperature and time. S4: Vacuum sintering: The tantalum blank after removing the composite binder is sintered in a high temperature and high vacuum environment to produce an anode with low carbon content.

2. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 1, characterized in that: In step S1, 0.1% to 10% by weight of PVP and 0.1% to 10% by weight of anhydrous glucose are weighed.

3. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 1, characterized in that: In S1, the solution is pure water or an organic solution, and the purity of the pure water or organic solution is greater than 99.6%.

4. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 3, characterized in that: In step S1, the ratio of tantalum powder dissolved in the solvent is 100g tantalum powder: 1ml to 50ml solvent.

5. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 1, characterized in that: In S1, the tantalum powder is sieved using a 20-100 mesh screen.

6. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 1, characterized in that: In S2, the single-sided dimension of the tantalum blank ranges from 0.1 mm to 10 cm.

7. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 1, characterized in that: In S3, the concentration of the hydrogen peroxide aqueous solution is 1% to 90%, and the purity is greater than 99.6%.

8. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 1, characterized in that: In S2, the die head moving speed during pressing is 0.01mm / s to 10mm / s, and the holding time is 1ms to 10min.

9. The method for manufacturing the low-carbon content anode of the tantalum capacitor according to claim 1, characterized in that: In step S4, the vacuum degree inside the furnace before heating is ≤1.0×10⁻⁶. -2 Pa, the vacuum degree inside the furnace during sintering is ≤4.0×10 Pa. -2 Pa, where the sintering temperature process is divided into: Stage 1: room temperature → T1, heating rate 0.5℃ / min~100℃ / min; T1 temperature range is 100℃~500℃, T1 is constant temperature for 1min~120min; Phase 2: T1→T2, heating rate 0.5℃ / min~100℃ / min; T2 temperature range 500℃~1000℃, T2 constant temperature 1min~120min; Phase 3: T2→T3, heating rate 0.5℃ / min~100℃ / min; T3 temperature range 1000℃~1400℃, T3 constant temperature 1min~120min; Stage 4: T3→T4, heating rate 0.5℃ / min~100℃ / min; T4 temperature range 1200℃→1450℃, constant temperature 1min~120min; Phase 5: T4 → T5. After the temperature is maintained at T4, the furnace is cooled to T5, which ranges from 100℃ to 1000℃. The vacuum level inside the furnace between T4 and T5 is ≤1.0×10⁻⁶. -3 Pa; Stage Six: T5→T6. At T5, argon gas with a purity greater than 99.9% is introduced into the furnace until the furnace pressure is -80kPa to 0Pa. At T6, the temperature is 0℃ to 100℃. When the temperature reaches T6, the tantalum billet is taken out of the sintering furnace to obtain a low-carbon anode.

Images