Capacitor for reducing tantalum capacitance attenuation and preparation method thereof

Abstract

The invention discloses a capacitor capable of reducing tantalum capacitance attenuation and a preparation method thereof. The preparation method comprises the following steps: preparing tantalum powder into a tantalum block; sintering the tantalum block; performing a forming process on the tantalum block to obtain a tantalum core with a dielectric oxide film; carrying out dipping treatment on the tantalum core with the dielectric oxide film, and then packaging the tantalum core; and aging the packaged tantalum core to complete the preparation of the capacitor. According to the forming process, a gradient boosting forming method is adopted, the forming voltage multiplying power of the tantalum core is improved, and the Ta2O5 dielectric oxide film with good performance is obtained; during assembly, a polarising agent is added into a working electrolyte to inhibit generation of hydrogen in a product, reduce air pressure release in the capacitor and stabilize the capacity; and through adjustment of an aging process method, the non-solid electrolyte tantalum capacitor with high voltage and larger capacity is manufactured.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitors, and in particular relates to a capacitor capable of reducing tantalum capacitance attenuation and a preparation method thereof. Background Art

[0002] Product lightweighting and miniaturization have always been the goals pursued by the market and suppliers. Users' demand for high-voltage, large-capacity, small-volume liquid tantalum products has become more and more urgent. With the continuous deepening of research on materials and process technologies, the process technology requirements for the production of liquid tantalum products have become higher and higher. At present, domestic and foreign manufacturers have developed products with large capacity and small volume. However, many small-volume and large-capacity capacitors produced by conventional processes, especially those with high technical difficulty, will have the problem of capacitance attenuation after electrical aging life. Therefore, a capacitor preparation method that can solve this problem is needed.

[0003] The patent document with announcement number CN104916443A discloses a high-voltage chip-type conductive polymer solid electrolyte tantalum capacitor and a manufacturing method thereof, the method comprising: pressing a chip-type tantalum powder raw material into a tantalum core block with a tantalum wire lead wire, vacuum sintering the tantalum core block, and then passivating it; placing the sintered block into a forming tank filled with ethylene glycol phosphate electrolyte to electrochemically form a dielectric layer with a thickness of not less than 3000 nanometers or 3500 nanometers; using a repeated immersion method to infiltrate a nanoscale poly (3,4-ethylenedioxythiophene) particle solution into the internal gap of the block and the dielectric layer of the block to deposit a cathode, coating the cathode with a graphite layer and a silver paste layer as a cathode lead layer; welding the tantalum wire lead wire of the block to the lead wire of the metal frame of the shell, and encapsulating it with epoxy resin to obtain a high-voltage chip-type conductive polymer solid electrolyte tantalum capacitor. However, the rated withstand voltage and leakage current of the chip-type solid tantalum electrolytic capacitor prepared by this patent can both meet the requirements of 50V or 63V, and the problem of reducing the loss of capacitor capacitance after aging is not solved. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a capacitor capable of reducing tantalum capacitance attenuation and a method for preparing the same.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a method for preparing a capacitor with reduced tantalum capacitance attenuation, comprising the following steps:

[0007] S1: preparing tantalum powder into tantalum blocks;

[0008] S2: sintering the tantalum block;

[0009] S3: performing a forming process on the tantalum block to obtain a tantalum core having a dielectric oxide film;

[0010] S4: performing an immersion treatment on the tantalum core having the dielectric oxide film, and then performing tantalum core packaging;

[0011] S5: After aging the packaged tantalum core, the preparation of the capacitor is completed.

[0012] Preferably, in step S1, tantalum powder having a specific volume of 15000 μFV / g is molded using a molding mold with a lubricant, and the anode tantalum block is obtained after slow demoulding.

[0013] Preferably, in step S2, the sintering temperature is 1500-1700° C., maintained for 30-50 minutes after reaching the temperature, and removed from the furnace after cooling to 30° C., to ensure that the specific volume of the tantalum core and tantalum powder after sintering is 13500-15500 μFV / g.

[0014] Preferably, the forming process in step S3 is voltage segment boosting forming, and the steps sequentially include: forming step A, forming step B, heat treatment, supplementary forming and boiling and washing.

[0015] Preferably, the forming liquid used in the forming process is ethylene glycol phosphate, and the forming step A comprises: soaking at a temperature of 86-89° C., and the soaking time is: soaking for 1-3 hours without electricity, and soaking for 0.5-2 hours with a voltage of 3V applied.

[0016] Preferably, the forming step B comprises: at a current density of 0-60V, 0.08nCV / 100mA; 60-90V, 0.06nCV / 100mA; 90-142V, 0.04nCV / 100mA, each stage is constant voltage for 4-9h;

[0017] The heat treatment comprises: maintaining at 300-400° C. for 20-45 minutes.

[0018] Preferably, the complementary forming step comprises: constant voltage at 75-85V for 10-40min; constant voltage at 86-95V for 10-40min; constant voltage at 96-105V for 10-40min; constant voltage at 106-115V for 10-40min; constant voltage at 116-125V for 10-40min; constant voltage at 126-135V for 10-40min; constant voltage at 136-145V for 10-40min.

[0019] Preferably, the boiling and washing step includes boiling and washing in deionized water at a temperature of 100-125° C. for 30-35 minutes, and re-boiling and washing six to seven times, and then taking out and drying for 3-3.5 hours to prepare a tantalum core with a good dielectric oxide film.

[0020] Preferably, the immersion treatment step in step S4 comprises: immersing the tantalum core with the dielectric oxide film in a sulfuric acid electrolyte for 0.5-2 hours, assembling using an electrolyte to which a compound polarizer composed of sulfate ions and metal cations is added, and then soldering and packaging.

[0021] Preferably, the aging steps of the packaged tantalum core in step S5 include: keeping at room temperature and 1-6V for 1-3 hours; then keeping at room temperature and 60-90V for 4-8 hours; then keeping at 55-75℃ and 60-90V for 4-8 hours; then keeping at 110-140℃ and 40-70V for 1-4 hours; then keeping at 75-95℃ and 60-90V for 40-55 hours; the boost rate is 2-7V / 20min.

[0022] A capacitor prepared by the above method.

[0023] The beneficial effects of the present invention are:

[0024] The formation process of the present invention adopts a gradient voltage boosting formation method to increase the formation voltage ratio of the tantalum core and obtain a Ta2O5 dielectric oxide film with good performance; during assembly, a polarizer is added to the working electrolyte to inhibit the generation of hydrogen inside the product, reduce the internal gas pressure release of the capacitor, and stabilize the capacity; and then through the adjustment of the aging process method, a high-voltage, larger-capacity non-solid electrolyte tantalum capacitor is manufactured. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0026] Embodiment 1:

[0027] A method for preparing a capacitor with reduced tantalum capacitance attenuation comprises the following steps:

[0028] S1: preparing tantalum powder into tantalum blocks;

[0029] S2: sintering the tantalum block;

[0030] S3: performing a forming process on the tantalum block to obtain a tantalum core having a dielectric oxide film;

[0031] S4: performing an immersion treatment on the tantalum core having the dielectric oxide film, and then performing tantalum core packaging;

[0032] S5: After aging the packaged tantalum core, the preparation of the capacitor is completed.

[0033] In the step S1, 22300 mg of tantalum powder with a specific volume of 15000 μFV / g is accurately weighed using an electronic analytical balance, and molded using a φ14.2 molding mold with stearic acid as a lubricant, and slowly demolded to obtain an anode tantalum block with a certain strength.

[0034] In step S2, the sintering temperature is 1500° C., which is maintained for 30 minutes after reaching the temperature, and the furnace is removed after cooling to 30° C., ensuring that the specific volume of the tantalum core and tantalum powder after sintering is 13500 μFV / g.

[0035] The forming process in step S3 is voltage step-up forming, and the steps include: forming step A, forming step B, heat treatment, supplementary forming and boiling and washing.

[0036] The forming liquid used in the forming process is ethylene glycol phosphate, and the forming step A includes: soaking at a temperature of 86° C., soaking time: soaking for 1 hour without electricity, and then soaking for 0.5 hour under the application of a voltage of 3V.

[0037] The forming step B comprises: at a current density of 0V, 0.08nCV / 100mA; 60V, 0.06nCV / 100mA; 90V, 0.04nCV / 100mA, each stage is constant voltage for 4h;

[0038] The heat treatment includes: maintaining at 300° C. for 20 minutes.

[0039] The complementary forming steps include: maintaining a constant voltage at 75V for 10 minutes; maintaining a constant voltage at 86V for 10 minutes; maintaining a constant voltage at 96V for 10 minutes; maintaining a constant voltage at 106V for 10 minutes; maintaining a constant voltage at 116V for 10 minutes; maintaining a constant voltage at 126V for 10 minutes; and maintaining a constant voltage at 136V for 10 minutes.

[0040] The boiling and washing step includes boiling and washing in deionized water at a temperature of 100° C. for 30 minutes, and boiling and washing six times, and then drying for 3 hours to prepare a tantalum core with a good Ta2O5 dielectric oxide film.

[0041] The immersion treatment step in step S4 includes: using sulfuric acid electrolyte to immerse the tantalum core with Ta2O5 dielectric oxide film for 0.5h, assembling it using electrolyte added with ferric sulfate polarizer, and then soldering and packaging it using conventional packaging methods. The immersion treatment and packaging can be conventional steps.

[0042] The aging steps of the packaged tantalum core in step S5 include: keeping at room temperature and 1V for 1 hour; then keeping at room temperature and 60V for 4 hours; then keeping at 55°C and 60V for 4 hours; then keeping at 110°C and 40V for 1 hour; then keeping at 75°C and 60V for 40 hours; the boost rate is 2V / 20min.

[0043] Embodiment 2:

[0044] A method for preparing a capacitor with reduced tantalum capacitance attenuation comprises the following steps:

[0045] S1: preparing tantalum powder into tantalum blocks;

[0046] S2: sintering the tantalum block;

[0047] S3: performing a forming process on the tantalum block to obtain a tantalum core having a dielectric oxide film;

[0048] S4: performing an immersion treatment on the tantalum core having the dielectric oxide film, and then performing tantalum core packaging;

[0049] S5: After aging the packaged tantalum core, the preparation of the capacitor is completed.

[0050] In the step S1, 22300 mg of tantalum powder with a specific volume of 15000 μFV / g is accurately weighed using an electronic analytical balance, and molded using a φ14.2 molding mold with stearic acid as a lubricant, and slowly demolded to obtain an anode tantalum block with a certain strength.

[0051] In step S2, the sintering temperature is 1700° C., which is maintained for 50 minutes after reaching the temperature, and the furnace is removed after cooling to 30° C., ensuring that the specific volume of the tantalum core and tantalum powder after sintering is 15500 μFV / g.

[0052] The forming process in step S3 is voltage step-up forming, and the steps include: forming step A, forming step B, heat treatment, supplementary forming and boiling and washing.

[0053] The forming liquid used in the forming process is ethylene glycol phosphate, and the forming step A includes: soaking at a temperature of 89° C., soaking time: soaking for 3 hours without electricity, and soaking for 0.5-2 hours under a voltage of 3V.

[0054] The forming step B comprises: at a current density of 60V, 0.08nCV / 100mA; 90V, 0.06nCV / 100mA; 142V, 0.04nCV / 100mA, each stage is constant voltage for 9h;

[0055] The heat treatment includes: maintaining at 400° C. for 45 minutes.

[0056] The complementary forming steps include: constant voltage at 85V for 40 minutes; constant voltage at 95V for 40 minutes; constant voltage at 105V for 40 minutes; constant voltage at 115V for 40 minutes; constant voltage at 125V for 40 minutes; constant voltage at 135V for 40 minutes; and constant voltage at 145V for 40 minutes.

[0057] The boiling and washing step includes boiling and washing in deionized water at a temperature of 125° C. for 35 minutes, and boiling and washing seven times, and then drying for 3.5 hours to prepare a tantalum core with a good Ta2O5 dielectric oxide film.

[0058] The immersion treatment step in step S4 includes: using sulfuric acid electrolyte to immerse the tantalum core with Ta2O5 dielectric oxide film for 2 hours, using electrolyte added with copper sulfate polarizer for assembly, and then using conventional packaging method for soldering packaging. The immersion treatment and packaging can be conventional steps.

[0059] The aging steps of the packaged tantalum core in step S5 include: keeping at room temperature and 6V for 3 hours; then keeping at room temperature and 90V for 8 hours; then keeping at 75°C and 90V for 8 hours; then keeping at 140°C and 70V for 4 hours; then keeping at 95°C and 90V for 55 hours; the boost rate is 7V / 20min.

[0060] Embodiment 3:

[0061] A method for preparing a capacitor with reduced tantalum capacitance attenuation comprises the following steps:

[0062] S1: preparing tantalum powder into tantalum blocks;

[0063] S2: sintering the tantalum block;

[0064] S3: performing a forming process on the tantalum block to obtain a tantalum core having a dielectric oxide film;

[0065] S4: performing an immersion treatment on the tantalum core having the dielectric oxide film, and then performing tantalum core packaging;

[0066] S5: After aging the packaged tantalum core, the preparation of the capacitor is completed.

[0067] In the step S1, 22300 mg of tantalum powder with a specific volume of 15000 μFV / g is accurately weighed using an electronic analytical balance, and molded using a φ14.2 molding mold with stearic acid as a lubricant, and slowly demolded to obtain an anode tantalum block with a certain strength.

[0068] In step S2, the sintering temperature is 1630° C., which is maintained for 40 minutes after reaching the temperature, and the furnace is removed after cooling to 30° C., ensuring that the specific volume of the tantalum core and tantalum powder after sintering is 14000 μFV / g.

[0069] The forming process in step S3 is voltage step-up forming, and the steps include: forming step A, forming step B, heat treatment, supplementary forming and boiling and washing.

[0070] The forming liquid used in the forming process is ethylene glycol phosphate, and the forming step A includes: soaking at a temperature of 86° C., soaking time: soaking for 2 hours without electricity, and soaking for 1 hour with a voltage of 3V applied.

[0071] The forming step B comprises: at a current density of 30V, 0.08nCV / 100mA; 80V, 0.06nCV / 100mA; 110V, 0.04nCV / 100mA, each stage is constant voltage for 6h;

[0072] The heat treatment includes: maintaining at 360° C. for 30 minutes.

[0073] The complementary forming steps include: constant voltage at 80V for 20 minutes; constant voltage at 90V for 20 minutes; constant voltage at 100V for 20 minutes; constant voltage at 110V for 20 minutes; constant voltage at 120V for 20 minutes; constant voltage at 130V for 20 minutes; and constant voltage at 142V for 20 minutes.

[0074] The boiling and washing step includes boiling and washing in deionized water at a temperature of 110° C. for 32 minutes, and re-boiling and washing six to seven times, and then taking out and drying for 3.5 hours to prepare a tantalum core with a good Ta2O5 dielectric oxide film.

[0075] The immersion treatment step in step S4 includes: using sulfuric acid electrolyte to immerse the tantalum core with Ta2O5 dielectric oxide film for 1 hour, using electrolyte added with copper sulfate polarizer for assembly, and then using conventional packaging method for soldering packaging. The immersion treatment and packaging can be conventional steps.

[0076] The aging steps of the packaged tantalum core in step S5 include: keeping at room temperature and 3V for 2 hours; then keeping at room temperature and 77V for 6 hours; then keeping at 65°C and 77V for 6 hours; then keeping at 125°C and 58V for 2 hours; then keeping at 85°C and 77V for 48 hours; the boost rate is 5V / 20min.

[0077] Comparative Example 1:

[0078] CAK35 type 75V2200μF non-solid electrolyte tantalum capacitor produced using existing technology.

[0079] The CAK35 type 75V 2200μF non-solid electrolyte tantalum capacitor was produced by the method of Examples 1-3, and the capacity loss of the capacitor of Comparative Example 1 after 480h aging is shown in the following table.

[0080] Group Capacity loss (%) Example 1 5.15 Example 2 3.36 Example 3 2.38 Comparative Example 1 18.08

[0081] It can be seen from the above table that the method of the present invention can not only manufacture non-solid electrolyte tantalum capacitors with high voltage and large capacity, but also the capacitance loss of the capacitors manufactured by the method after aging is greatly reduced.

[0082] The method of the invention is suitable for preparing non-solid electrolyte tantalum electrolytic capacitors.

Claims

1. A method for preparing a capacitor with reduced capacitance attenuation of tantalum, characterized in that: The following steps are involved: S1: preparing tantalum powder into tantalum blocks; S2: sintering the tantalum block; S3: performing a forming process on the tantalum block to obtain a tantalum core having a dielectric oxide film; S4: performing an immersion treatment on the tantalum core having the dielectric oxide film, and then performing tantalum core packaging; S5: After aging the packaged tantalum core, the preparation of the capacitor is completed.

2. A method for preparing a capacitor with reduced tantalum capacitance attenuation as claimed in claim 1, characterized in that: In the step S1, tantalum powder with a specific volume of 15000 μFV / g is molded using a molding mold with a lubricant, and the anode tantalum block is obtained after slow demoulding.

3. The method for preparing a capacitor with reduced tantalum capacitance attenuation as claimed in claim 1, characterized in that: In step S2, the sintering temperature is 1500-1700° C., and the temperature is maintained for 30-50 minutes. The furnace is removed after cooling to 30° C. to ensure that the specific volume of the tantalum core and tantalum powder after sintering is 13500-15500 μFV / g.

4. The method for preparing a capacitor with reduced capacitance attenuation of tantalum as claimed in claim 1, characterized in that: The forming process in step S3 is voltage step-up forming, and the steps include: forming step A, forming step B, heat treatment, supplementary forming and boiling and washing.

5. The method for preparing a capacitor with reduced tantalum capacitance attenuation as claimed in claim 4, characterized in that: The forming liquid used in the forming process is ethylene glycol phosphate, and the forming step A comprises: soaking at a temperature of 86-89° C., soaking time: soaking for 1-3 hours without electricity, and soaking for 0.5-2 hours with a voltage of 3V applied; The forming step B comprises: at a current density of 0-60V, 0.08nCV / 100mA; 60-90V, 0.06nCV / 100mA; 90-142V, 0.04nCV / 100mA, each stage is constant voltage for 4-9h; The heat treatment comprises: maintaining at 300-400° C. for 20-45 minutes.

6. A method for preparing a capacitor with reduced capacitance attenuation of tantalum as claimed in claim 4, characterized in that: The complementary forming step includes: constant voltage at 75-85V for 10-40min; constant voltage at 86-95V for 10-40min; constant voltage at 96-105V for 10-40min; constant voltage at 106-115V for 10-40min; constant voltage at 116-125V for 10-40min; constant voltage at 126-135V for 10-40min; constant voltage at 136-145V for 10-40min.

7. A method for preparing a capacitor with reduced capacitance attenuation of tantalum as claimed in claim 4, characterized in that: The boiling and washing step includes boiling and washing in deionized water at a temperature of 100-125° C. for 30-35 minutes, and re-boiling and washing six to seven times, and then drying for 3-3.5 hours after taking out, so as to prepare a tantalum core with a good dielectric oxide film.

8. The method for preparing a capacitor with reduced capacitance attenuation of tantalum as claimed in claim 1, characterized in that: The immersion treatment step in step S4 includes: immersing the tantalum core with a dielectric oxide film in a sulfuric acid electrolyte for 0.5-2 hours, assembling using an electrolyte to which a compound polarizer composed of sulfate ions and metal cations is added, and then soldering and packaging.

9. The method for preparing a capacitor with reduced capacitance attenuation of tantalum as claimed in claim 1, characterized in that: The aging steps of the packaged tantalum core in step S5 include: keeping at room temperature and 1-6V for 1-3 hours; then keeping at room temperature and 60-90V for 4-8 hours; then keeping at 55-75℃ and 60-90V for 4-8 hours; then keeping at 110-140℃ and 40-70V for 1-4 hours; then keeping at 75-95℃ and 60-90V for 40-55 hours; the boost rate is 2-7V / 20min.

10. A capacitor prepared by the method according to any one of claims 1 to 9.