Preparation method of internal micro-negative-pressure non-solid tantalum capacitor

Abstract

A preparation method of an internal micro-negative-pressure non-solid tantalum capacitor specifically comprises the following steps: step 1, diluting concentrated sulfuric acid, then adding a high-boiling-point alcohol ether additive and a depolarizer, and uniformly mixing to obtain an electrolyte; 2, assembling and welding the tantalum core, the ruthenium oxide sheet, the polytetrafluoroethylene diaphragm, the gasket and the tantalum shell to obtain a capacitor without electrolyte injection; 3, electrolyte is injected into the capacitor, and the capacitor after electrolyte injection is subjected to opening aging at the normal temperature and the high temperature in sequence; step 4, discharging gas generated by aging of the capacitor, and then supplementing part of the lost electrolyte until a space of 0.2-0.8 ml is reserved in the capacitor; and step 5, transferring the capacitor into a drying oven, heating to enable the interior of the capacitor to expand until the whole internal space is filled with the electrolyte, welding the electrolyte injection hole while the capacitor is hot, and naturally cooling to obtain the internal micro-negative-pressure non-solid tantalum capacitor. The tantalum capacitor prepared by the invention can significantly improve the problem of shell bulging caused by high-temperature thermal expansion, and meets the use requirements.

Description

Technical Field

[0001] This invention belongs to the field of tantalum capacitor manufacturing, specifically relating to a method for manufacturing a non-solid tantalum capacitor with internal micro-negative voltage. Background Technology

[0002] Tantalum capacitors, as core passive components in the electronics industry, have undergone significant technological iterations since their initial commercialization by Bell Labs in 1956, evolving from solid-state sintered capacitors to liquid electrolyte capacitors. Early solid tantalum capacitors (MnO2 cathode) established an irreplaceable position in the military and aerospace fields due to their small size and stable capacitance; however, their inherent high ESR (equivalent series resistance) limited their high-frequency applications. Liquid tantalum capacitors, as an important branch of tantalum capacitors, have secured an irreplaceable position in extreme environment circuits such as aerospace, military electronics, and oil exploration due to their low equivalent series resistance.

[0003] These applications involve large and rapid temperature fluctuations and high voltages, requiring liquid tantalum capacitors to maintain stability under high temperatures and voltages. Liquid tantalum capacitors use sulfuric acid solution as the electrolyte. At high temperatures, the sulfuric acid solution evaporates easily, creating a large vapor pressure (38% sulfuric acid boiling point -120℃). Simultaneously, the electrolyte, PTFE diaphragm, and gaskets exhibit significant thermal expansion, subjecting the tantalum shell to considerable expansion forces. High temperature and high voltage also enhance the surface reactivity of the tantalum core, accelerating internal aging and gas production, further deteriorating the internal pressure and ultimately leading to tantalum shell deformation, causing acid leakage and capacitor failure.

[0004] The most common method in the industry is to use a thicker tantalum shell to suppress expansion and deformation, but this does not solve the problem at its root. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing an internal micro-negative voltage non-solid tantalum capacitor.

[0006] The present invention adopts the following technical solution: A method for fabricating an internally micro-negative voltage non-solid tantalum capacitor specifically includes the following steps: Step 1: Dilute concentrated sulfuric acid to reduce its mass fraction from 95wt%-98wt% to 34wt%-45wt%, then add high-boiling-point alcohol ether additives and depolarizers, and mix well to obtain the electrolyte. Step 2: Assemble and weld the tantalum core, ruthenium oxide sheet, polytetrafluoroethylene diaphragm, gasket, and tantalum shell to obtain a capacitor without electrolyte. Step 3: Inject the electrolyte prepared in Step 1 into the capacitor. After injection, the capacitor is subjected to open-end aging at room temperature and high temperature in sequence. Step 4: Place the aged capacitor into a negative pressure device to expel the gas produced during aging, and then replenish some of the lost electrolyte until there is 0.2-0.8ml of space inside. Step 5: Transfer the capacitor to an oven and heat it until the inside of the capacitor expands and the electrolyte fills the entire internal space. While it is still hot, weld the electrolyte injection hole and allow it to cool naturally to obtain the internal micro-negative voltage non-solid tantalum capacitor.

[0007] Furthermore, the amount of the high-boiling-point alcohol ether additive is 3-20% of the total mass of the electrolyte, and the amount of the depolarizer is 0.5-3% of the total mass.

[0008] Furthermore, in step 5, the oven temperature is 50-125℃.

[0009] Furthermore, the high-boiling-point alcohol ether additive is one or more of diethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, and diethylene glycol propyl ether.

[0010] Furthermore, the depolarizing agent is one or more of copper sulfate, ferric sulfate, silver sulfate, chromium sulfate, and vanadium oxysulfate.

[0011] Furthermore, in step 3, the aging environment at room temperature is as follows: 1.1-1.4 times the rated voltage, aging for 20-30 hours.

[0012] Furthermore, in step 3, the high-temperature aging environment is as follows: 80-130℃ temperature, 0.6-1.0 times the rated voltage, aging for 1-5 hours.

[0013] Furthermore, in step 2, the preparation method of the tantalum core is as follows: tantalum powder and tantalum wire are pressed into tantalum blocks, and the tantalum blocks are vacuum sintered; the sintered tantalum blocks are placed in an aqueous solution containing acid and ethylene glycol to perform electrochemical formation, so that the thickness of the generated dielectric layer reaches the design requirements; after cleaning off excess acid, the tantalum core is dried.

[0014] Furthermore, in the aqueous solution, the acid solution is 0.05-0.2 wt% phosphoric acid, and the mass fraction of ethylene glycol is 30-70 wt%.

[0015] As can be seen from the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are: First, this application specifically defines the preparation method of non-solid tantalum capacitors, which uses high temperature to seal the electrolyte injection hole and release the high temperature thermal expansion pressure, which can significantly improve the shell bulging problem caused by high temperature thermal expansion. At the same time, under normal pressure, the inside of the capacitor is in a negative pressure state, which has a certain resistance to aging gas production and has the characteristics of long life. Secondly, the present invention uses a high-temperature open-end aging process combined with a high-boiling-point electrolyte, which can promptly remove harmful gases generated during aging and reduce the initial internal pressure of the capacitor; at the same time, the high-boiling-point electrolyte is stable and non-volatile when heated, and its composition is controllable, which improves the consistency of product manufacturing. Third, the high-boiling-point electrolyte is supplemented with high-boiling-point organic alcohol ether additives. Under high voltage and high temperature, the electron-rich oxygen of the alcohol ether easily interacts with the surface of the dielectric layer, adsorbs and isolates the electrolyte, shields the defect sites of the dielectric layer, improves the stability of the dielectric layer surface, and enables the capacitor to have high-temperature and long-life characteristics. Detailed Implementation

[0016] The present invention will be further described below through specific embodiments.

[0017] A method for fabricating an internally micro-negative voltage non-solid tantalum capacitor specifically includes the following steps: Step 1: Press tantalum powder and tantalum wire into tantalum blocks and vacuum sinter the tantalum blocks; place the sintered tantalum blocks into an aqueous solution containing acid and ethylene glycol to perform electrochemical formation, so that the thickness of the generated dielectric layer reaches the design requirements; after cleaning off excess acid, dry to obtain tantalum cores. Step 2: Dilute concentrated sulfuric acid to reduce its mass fraction from 95wt%-98wt% to 34wt%-45wt%. Then add high-boiling-point alcohol ether additive and depolarizer, and mix thoroughly to obtain the electrolyte. The amount of high-boiling-point alcohol ether additive added is 3-20% of the total mass of the electrolyte, and the amount of depolarizer added is 0.5-3% of the total mass. Step 3: Assemble and weld the tantalum core, ruthenium oxide sheet, polytetrafluoroethylene diaphragm, gasket, and tantalum shell to obtain a capacitor without electrolyte. Step 4: Inject the electrolyte prepared in Step 1 into the capacitor. After injection, the capacitor is subjected to open-end aging at room temperature and high temperature in sequence. Step 5: Place the aged capacitor into a negative pressure device to expel the gas produced during aging, and then replenish some of the lost electrolyte until there is 0.2-0.8ml of space inside. Step 6: Transfer the capacitor to an oven and heat it at a temperature of 50-125°C until the inside of the capacitor expands and the electrolyte fills the entire internal space. While it is still hot, weld the electrolyte injection hole and allow it to cool naturally to obtain the internal micro-negative voltage non-solid tantalum capacitor. Step 7: The obtained internal micro-negative voltage non-solid tantalum capacitors are further aged at 25°C and 85°C for 24 hours and 48 hours, respectively. The electrical performance is tested and unqualified products are eliminated.

[0018] Specifically, in step 1, the acid solution uses 0.05-0.2 wt% phosphoric acid and the mass fraction of ethylene glycol is 30-70 wt%.

[0019] In step 2, the high-boiling-point alcohol ether additive is one or more of diethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, and diethylene glycol propyl ether; the depolarizing agent is one or more of copper sulfate, ferric sulfate, silver sulfate, chromium sulfate, and vanadium oxysulfate.

[0020] In step 3, the ambient temperature aging environment is as follows: 1.1-1.4 times the rated voltage, aging for 20-30 hours; the high temperature aging environment is as follows: 80-130℃ temperature, 0.6-1.0 times the rated voltage, aging for 1-5 hours.

[0021] Example 1 A method for fabricating an internally micro-negative voltage non-solid tantalum capacitor specifically includes the following steps: Step 1: Mix tantalum powder with a specific volume of 10000 uF•V / g and tantalum wire at a ratio of 6 g / cm. 2 The density is pressed into tantalum blocks with a diameter of ø20mm and a thickness of 3mm, and the tantalum blocks are vacuum sintered; the sintered tantalum blocks are placed in an aqueous solution containing 0.1wt% phosphoric acid and 50wt% ethylene glycol to carry out electrochemical formation so that the thickness of the generated dielectric layer reaches the design requirements. After cleaning off the excess acid, the tantalum core is dried. Step 2: Dilute concentrated sulfuric acid to reduce its mass fraction from 98wt% to 38wt%, then add 10wt% diethylene glycol methyl ether and 2wt% copper sulfate, mix well to obtain electrolyte, and transfer to a fluorinated bottle for sealed storage at low temperature. Step 3: Assemble and weld the tantalum core, ruthenium oxide sheet, polytetrafluoroethylene diaphragm, gasket, and tantalum shell to obtain a capacitor without electrolyte. Step 4: Inject the electrolyte prepared in Step 1 into the capacitor. After injection, the capacitor is aged sequentially at room temperature and 1.2 times the rated voltage for 24 hours, and at 85°C and 1.0 times the rated voltage for 2 hours. Step 5: Place the aged capacitor into a negative pressure device to expel the gas produced during aging, and then replenish some of the lost electrolyte until there is 0.4ml of space inside. Step 6: Transfer the capacitor to an oven and heat it at 85°C until the inside of the capacitor expands and the electrolyte fills the entire internal space. While it is still hot, weld the electrolyte injection hole and allow it to cool naturally to obtain the internal micro-negative voltage non-solid tantalum capacitor. Step 7: The obtained internal micro-negative voltage non-solid tantalum capacitors are further aged at 25°C and 85°C for 24 hours and 48 hours, respectively. The electrical performance is tested and unqualified products are eliminated.

[0022] Example 2 The preparation method is basically the same as that in Example 1, the main difference being that the oven temperature for welding the liquid injection port in step 6 is 50°C.

[0023] Example 3 Its preparation method is basically the same as that in Example 1, the main difference being that the oven temperature for welding the liquid injection port in step 6 is 125°C.

[0024] Example 4 The preparation method is basically the same as that in Example 1, the main difference being that the mass content of diethylene glycol methyl ether in the high-boiling-point electrolyte is 5%.

[0025] Example 5 The preparation method is basically the same as in Example 1, the main difference being that the mass content of diethylene glycol methyl ether in the high-boiling-point electrolyte is 15%.

[0026] Example 6 The preparation method is basically the same as in Example 1, the main difference being that the mass content of diethylene glycol methyl ether in the high-boiling-point electrolyte is 20%.

[0027] Example 7 The preparation method is basically the same as in Example 1, the main difference being: in step 1, tantalum powder with a powder specific volume of 23000 uF•V / g is mixed with tantalum wire at a ratio of 6 g / cm 2 The tantalum core is pressed into a tantalum block with a density of 0.1 wt% phosphoric acid and 50 wt% ethylene glycol in a vacuum sintering process. The sintered tantalum block is then placed in an aqueous solution of 0.1 wt% phosphoric acid and 50 wt% ethylene glycol to form an electrochemical layer, which achieves the desired thickness. After removing excess acid, the tantalum core is dried.

[0028] Example 8 The preparation method is basically the same as that in Example 1, the main difference being that the sulfuric acid mass fraction of the high-boiling-point electrolyte is 34%.

[0029] Example 9 The preparation method is basically the same as in Example 1, the main difference being that the sulfuric acid mass fraction of the high-boiling-point electrolyte is 45%.

[0030] Comparative Example 1 A method for fabricating an internally micro-negative voltage non-solid tantalum capacitor specifically includes the following steps: Step 1: Mix tantalum powder with a specific volume of 10000 uF•V / g and tantalum wire at a ratio of 6 g / cm. 2 The density is pressed into tantalum blocks with a diameter of ø20mm and a thickness of 3mm, and the tantalum blocks are vacuum sintered; the sintered tantalum blocks are placed in an aqueous solution containing 0.1wt% phosphoric acid and 50wt% ethylene glycol to carry out electrochemical formation so that the thickness of the generated dielectric layer reaches the design requirements. After cleaning off the excess acid, the tantalum core is dried. Step 2: Dilute 98% concentrated sulfuric acid to 38 wt%, add 10 wt% diethylene glycol methyl ether and 2 wt% copper sulfate to the sulfuric acid solution, mix well to obtain the electrolyte, and transfer it to a fluorinated bottle for sealing and low-temperature storage. Step 3: Assemble and weld the tantalum core, ruthenium oxide sheet, polytetrafluoroethylene diaphragm, gasket, and tantalum shell to obtain a capacitor without electrolyte. Step 4: Inject the electrolyte prepared in Step 1 into the capacitor. After injection, the capacitor is subjected to open-end aging at room temperature for 24 hours and open-end aging at 85°C for 2 hours. Step 5: Place the aged capacitor into a negative pressure device to expel the gas generated during aging, then replenish some of the lost electrolyte until there is 0.4ml of space inside, and weld the electrolyte injection hole at room temperature to obtain the non-solid tantalum capacitor. Step 6: The obtained non-solid tantalum capacitors are further aged at 25°C and 85°C for 24 hours and 48 hours, respectively. The electrical performance is tested and unqualified products are eliminated.

[0031] Comparative Example 2 A method for fabricating an internally micro-negative voltage non-solid tantalum capacitor specifically includes the following steps: Step 1: Mix tantalum powder with a specific volume of 10000 uF•V / g and tantalum wire at a ratio of 6 g / cm. 2 The density is pressed into tantalum blocks with a diameter of ø20mm and a thickness of 3mm, and the tantalum blocks are vacuum sintered; the sintered tantalum blocks are placed in an aqueous solution containing 0.1wt% phosphoric acid and 50wt% ethylene glycol to carry out electrochemical formation so that the thickness of the generated dielectric layer reaches the design requirements. After cleaning off the excess acid, the tantalum core is dried. Step 2: Dilute 98% concentrated sulfuric acid to 38 wt%, add 10 wt% diethylene glycol methyl ether and 2 wt% copper sulfate to the sulfuric acid solution, mix well to obtain the electrolyte, and transfer it to a fluorinated bottle for sealing and low-temperature storage. Step 3: Assemble and weld the tantalum core, ruthenium oxide sheet, polytetrafluoroethylene diaphragm, gasket, and tantalum shell to obtain a capacitor without electrolyte. Step 4: Inject electrolyte into the capacitor, transfer the capacitor to an oven, heat it to 85°C, and allow the capacitor to expand until the electrolyte fills the entire internal space. While it is still hot, weld the electrolyte injection hole, and after natural cooling, you will get a non-solid tantalum capacitor. Step 5: The obtained non-solid tantalum capacitors are further aged at 25°C and 85°C for 24 hours and 48 hours, respectively. The electrical performance is tested and unqualified products are eliminated.

[0032] Comparative Example 3 The preparation method is basically the same as in Example 1, the main difference being that the mass content of diethylene glycol methyl ether in the high electrolyte is 0%, that is, it does not include diethylene glycol methyl ether.

[0033] Comparative Example 4 A method for fabricating an internally micro-negative voltage non-solid tantalum capacitor specifically includes the following steps: Step 1: Mix tantalum powder with a specific volume of 10000 uF•V / g and tantalum wire at a ratio of 6 g / cm. 2 The density is pressed into tantalum blocks with a diameter of ø20mm and a thickness of 3mm, and the tantalum blocks are vacuum sintered; the sintered tantalum blocks are placed in an aqueous solution containing 0.1wt% phosphoric acid and 50wt% ethylene glycol to carry out electrochemical formation so that the thickness of the generated dielectric layer reaches the design requirements. After cleaning off the excess acid, the tantalum core is dried. Step 2: Dilute 98% concentrated sulfuric acid to 38 wt%, add 2 wt% copper sulfate to the sulfuric acid solution, mix well to obtain the electrolyte, and transfer it to a fluorinated bottle for sealing and low-temperature storage. Step 3: Assemble and weld the tantalum core, ruthenium oxide sheet, polytetrafluoroethylene diaphragm, gasket, and tantalum shell to obtain a capacitor without electrolyte. Step 4: Inject the electrolyte prepared in Step 1 into the capacitor, and weld the electrolyte injection hole at room temperature to obtain the non-solid tantalum capacitor. Step 5: The obtained non-solid tantalum capacitors are further aged at 25°C and 85°C for 24 hours and 48 hours, respectively. The electrical performance is tested and unqualified products are eliminated.

[0034] The performance of the non-solid tantalum capacitors prepared in Examples 1-9 and Comparative Examples 1-4 was evaluated. The specific results are shown in Table 1. The test methods are as follows: ① Room temperature test: Using an LCR meter, the AC voltage was set to 1V, the bias voltage to 2V, and the test frequency to 100Hz. The capacitance and loss tangent were tested and recorded. ② 125℃ high temperature life test: The capacitor was placed in a 125℃ constant temperature chamber and left to stand for 1 hour to allow the capacitor to heat up to 125℃. The capacitor was then increased to 60% of the rated voltage at a rate of 5V / min. After reaching the specified voltage, the test was switched to constant voltage. The leakage current in the first hour after constant voltage was recorded as I. The leakage current was then tested every 10 hours, and the appearance of the capacitor was observed. If the leakage current increased by a factor of I (1 hour) or the appearance bulged, the capacitor was considered to have failed. The total time was recorded as the 125℃ life of the capacitor. The test was stopped after 2000 hours and recorded as >2000h.

[0035] Table 1 Test Data Table Table 1 shows that the tantalum capacitor of the present invention has an ultra-long life of over 2000 hours at 125°C under a high voltage of 75V (60% derating). Comparing Examples 1-3 and Comparative Example 1, it can be found that as the temperature increases during sealing of the electrolyte injection hole, the high-temperature life of the capacitor is improved. However, at high temperatures, more electrolyte is squeezed out due to thermal expansion, resulting in less electrolyte actually retained and increased losses in the capacitor at room temperature. Therefore, the temperature needs to be controlled within a reasonable range. Comparing Examples 1, 4, 5, and 6, and Comparative Example 3, it can be seen that diethylene glycol methyl ether can significantly improve the high-temperature life of the capacitor. However, introducing too much ethylene glycol ether additive will lead to an increase in electrolyte viscosity, which will deteriorate both capacity and losses. Examples 1, 8, and 9 show that when the sulfuric acid concentration is too high, the dielectric layer surface is more prone to breakdown due to the increased concentration of anions, resulting in a poor high-temperature life of the capacitor. Comparing Examples 1 and Comparative Example 4, it can be seen that the specific limitations of the electrolyte, the high-temperature opening aging process, and the high-temperature welding electrolyte injection hole process are coordinated to significantly improve the high-temperature life of the capacitor.

[0036] This application specifically defines a method for manufacturing non-solid tantalum capacitors. By sealing the electrolyte injection hole at high temperature, the high-temperature thermal expansion pressure is released, which can significantly improve the problem of shell bulging caused by high-temperature thermal expansion. At the same time, under normal pressure, the inside of the capacitor is in a negative pressure state, which has a certain resistance to aging gas generation and has the characteristics of long life. In addition, the use of high-temperature open aging process combined with high-boiling-point electrolyte can promptly remove harmful gases generated during aging and reduce the initial internal pressure of the capacitor. Meanwhile, the high-boiling-point electrolyte is stable and non-volatile when heated, and its composition is controllable, which improves the consistency of product manufacturing.

[0037] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing an internally micro-negative voltage non-solid tantalum capacitor, characterized in that: Specifically, the following steps are included: Step 1: Dilute concentrated sulfuric acid to reduce its mass fraction from 95wt%-98wt% to 34wt%-45wt%, then add high-boiling-point alcohol ether additives and depolarizers, and mix well to obtain the electrolyte. Step 2: Assemble and weld the tantalum core, ruthenium oxide sheet, polytetrafluoroethylene diaphragm, gasket, and tantalum shell to obtain a capacitor without electrolyte. Step 3: Inject the electrolyte prepared in Step 1 into the capacitor. After injection, the capacitor is subjected to open-end aging at room temperature and high temperature in sequence. Step 4: Place the aged capacitor into a negative pressure device to expel the gas produced during aging, and then replenish some of the lost electrolyte until there is 0.2-0.8ml of space inside. Step 5: Transfer the capacitor to an oven and heat it until the inside of the capacitor expands and the electrolyte fills the entire internal space. While it is still hot, weld the electrolyte injection hole and allow it to cool naturally to obtain the internal micro-negative voltage non-solid tantalum capacitor.

2. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: The amount of the high-boiling-point alcohol ether additive is 3-20% of the total mass of the electrolyte, and the amount of the depolarizer is 0.5-3% of the total mass.

3. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: In step 5, the oven temperature is 50-125℃.

4. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: The high-boiling-point alcohol ether additive is one or more of diethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, and diethylene glycol propyl ether.

5. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: The depolarizing agent is one or more of copper sulfate, ferric sulfate, silver sulfate, chromium sulfate, and vanadium oxysulfate.

6. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: In step 3, the aging environment at room temperature is as follows: 1.1-1.4 times the rated voltage, aging for 20-30 hours.

7. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: In step 3, the high-temperature aging environment is as follows: 80-130℃ temperature, 0.6-1.0 times the rated voltage, aging for 1-5 hours.

8. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: In step 2, the tantalum core is prepared as follows: tantalum powder and tantalum wire are pressed into tantalum blocks, and the tantalum blocks are vacuum sintered; the sintered tantalum blocks are placed in an aqueous solution containing acid and ethylene glycol to perform electrochemical formation, so that the thickness of the generated dielectric layer reaches the design requirements; after cleaning off excess acid, the tantalum core is dried.

9. The method for preparing an internally micro-negative voltage non-solid tantalum capacitor according to claim 1, characterized in that: In the aqueous solution, the acid solution is 0.05-0.2wt% phosphoric acid, and the mass fraction of ethylene glycol is 30-70wt%.

Images