Method for reducing leakage current of tantalum capacitor in high-temperature and high-humidity environment

Abstract

The invention discloses a method for reducing leakage current of a tantalum capacitor in a high-temperature and high-humidity environment. The method comprises the following steps of: performing graphite layer impregnation on a tantalum core on which a dielectric oxide film and a MnO2 layer are formed; the graphite layer comprises a water-based graphite layer and an oily graphite layer, and an additive is added in the process of preparing the oily graphite layer. According to the method, the nano antimony-doped tin oxide material is added into the oily graphite solution, Ag < + > is adsorbed in the migration process, a stable adsorption layer is formed, the migration path of silver ions is effectively blocked, the insulation resistance between the tantalum anode and the MnO2 cathode is remarkably enhanced, and the problem of current leakage of the chip tantalum capacitor in high temperature and high humidity is effectively solved. The surface of the used nano-antimony-doped tin oxide is provided with permanent negative charges, a stable adsorption layer is formed through the adsorption effect of a nano-antimony-doped tin oxide adding material, and the electrical performance and the service life of the chip capacitor are not affected.

Description

Technical Field

[0001] This invention belongs to the field of tantalum capacitor manufacturing technology, and particularly relates to a method for reducing the leakage current of tantalum capacitors under high temperature and high humidity conditions. Background Technology

[0002] Solid electrolyte tantalum surface-mount capacitors (hereinafter referred to as surface-mount tantalum capacitors) are widely used in aerospace and other fields due to their small size, large capacitance, good temperature and frequency stability, and excellent filtering performance. In high-temperature and high-humidity environments, despite the airtight encapsulation of surface-mount tantalum capacitors, moisture can still slowly penetrate into the capacitor through tiny pores, interfaces, or the material itself. Under the influence of moisture and applied voltage, elemental silver ionizes into silver ions, which grow continuously from the cathode to the anode, reacting with OH- ions generated by the ionization of water molecules. - The reaction produces AgOH, which is unstable and decomposes into Ag₂O, forming a gel-like dispersion. Under the influence of water vapor and voltage, Ag₂O reacts with H₂O to produce Ag₂O. + The silver ions migrate towards the cathode. During this migration, there is a chance that the silver ions can connect the anode Ta / cathode MnO2 layers through cracks in the Ta2O5 dielectric film, reducing the insulation resistance between the anode Ta / cathode MnO2 layers. This not only leads to an increase in the leakage current of the capacitor but also seriously affects the electrical performance and service life of the tantalum capacitor under long-term use or in high-temperature and high-humidity environments.

[0003] Currently, to reduce the leakage current of surface-mount tantalum capacitors under high temperature and humidity conditions, some improvement methods have been proposed, such as using denser packaging materials or coating the tantalum core with conformal coating. However, these methods often increase manufacturing costs or make the process more complex.

[0004] Patent application CN119252670A discloses a solid electrolyte tantalum chip capacitor and its manufacturing method that ensure the electrical performance of the chip tantalum capacitor in humid environments. This patent effectively improves the moisture resistance of the chip tantalum chip capacitor by coating a graphite silver paste layer with a specific hydrophobic moisture-proof layer, without increasing the manufacturing process difficulty, cost, or finished product volume. This makes the chip tantalum chip capacitor suitable for use in high-temperature and high-humidity environments, ensuring product performance. However, this patent still has the problem of reducing the capacitor's equivalent series resistance (ESR). Therefore, how to effectively prevent moisture penetration and improve the reliability of tantalum capacitors in high-temperature and high-humidity environments without affecting their normal performance has become a key problem that urgently needs to be solved in the field of tantalum capacitor technology. This not only relates to the service life and electrical performance of tantalum capacitors but also to their reliability in high-end electronic equipment applications. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for reducing the leakage current of tantalum capacitors under high temperature and high humidity conditions.

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

[0007] The present invention provides a method for reducing the leakage current of tantalum capacitors under high temperature and high humidity conditions, characterized in that: it includes a step of impregnating the tantalum core after forming a dielectric oxide film and a MnO2 layer with a graphite layer; the graphite layer includes an aqueous graphite layer and an oily graphite layer, and an additive is added during the preparation of the oily graphite layer.

[0008] Preferably, the preparation steps of the aqueous graphite layer include: A1: An aqueous graphite layer is prepared by impregnating a tantalum core after the formation of a dielectric oxide film and a MnO2 layer. The thickness of the aqueous graphite layer is 0.02~0.05mm. A2: The tantalum core after the formation of the water-based graphite layer is dried and cured sequentially.

[0009] Preferably, in step A2, the tantalum core impregnated with the water-based graphite layer is dried at room temperature for 10-30 minutes.

[0010] Preferably, in step A2, the tantalum core is dried and then cured at 160-200℃ for 20-50 minutes.

[0011] Preferably, the preparation steps of the oily graphite layer include: B1: The tantalum core after the formation of the aqueous graphite layer is immersed in a mixture of oily graphite and additives to form an oily graphite layer in the aqueous graphite layer. B2: The tantalum cores with the formed oily graphite layer are sequentially dried and cured.

[0012] Preferably, in step B1, the oily graphite and the additives are mixed at a mass ratio of 10-20:1-3.

[0013] Preferably, in step B1, the additive is ultrasonically dispersed in an oily graphite solution for 30-60 minutes to obtain a mixture.

[0014] Preferably, in step B2, the tantalum core is dried at room temperature for 40-60 minutes; after drying, it is cured at 120-180°C for 20-40 minutes.

[0015] Preferably, the additive is nano-antimony-doped tin oxide.

[0016] Preferably, the nano-antimony-doped tin oxide has an average particle size of 20-50 nm and a solid content of 0.8-3.0%.

[0017] The beneficial effects of this invention are as follows: 1) By adding nano-antimony-doped tin oxide material to an oily graphite solution, in Ag... + During migration, silver ions are adsorbed to form a stable adsorption layer, effectively blocking the migration path of silver ions, significantly enhancing the insulation resistance between the tantalum anode and the MnO2 cathode, and effectively improving the leakage current problem of chip tantalum capacitors in high temperature and high humidity.

[0018] 2) The nano-antimony-doped tin oxide of the present invention has a permanent negative charge on its surface. Through the adsorption effect of the nano-antimony-doped tin oxide additive, a stable adsorption layer is formed without affecting the electrical performance and service life of the chip capacitor.

[0019] 3) The solution of the present invention does not require changing the overall structural design of the tantalum capacitor or using a more compact packaging material, thus avoiding increased manufacturing costs and manufacturing difficulties. Without affecting the normal performance of the tantalum capacitor, it improves the leakage current of the chip tantalum capacitor under high temperature and high humidity conditions.

[0020] 4) The preparation method is simple and inexpensive, easy to implement on existing production lines, and has good prospects for industrial application. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the surface of the tantalum core after being processed by the present invention; In the figure: 1-tantalum core, 2-tantalum pentoxide, 3-tantalum block, 4-water-based graphite layer, 5-nano antimony-doped tin oxide particles, 6-silver paste layer, 7-oil-based graphite layer. Detailed Implementation

[0022] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0023] Example 1: like Figure 1 As shown, a method for reducing the leakage current of a tantalum capacitor under high temperature and high humidity conditions includes the step of impregnating a tantalum core after forming a tantalum pentoxide dielectric oxide film and a MnO2 layer with a graphite layer; the graphite layer includes an aqueous graphite layer and an oily graphite layer, and additives are added during the preparation of the oily graphite layer.

[0024] The preparation steps of the aqueous graphite layer include: A1: A water-based graphite layer with a thickness of 0.03 mm was prepared by impregnating the tantalum core after the formation of the dielectric oxide film and MnO2 layer; A2: The tantalum core after the formation of the water-based graphite layer is dried and cured sequentially.

[0025] In step A2, the tantalum core impregnated with the water-based graphite layer is dried at room temperature for 40 minutes to remove excess solvent.

[0026] In step A2, the tantalum core is dried and then cured at 160°C for 20 minutes.

[0027] The preparation steps of the oily graphite layer include: B1: The tantalum core after the formation of the aqueous graphite layer is immersed in a mixture of oily graphite and additives to form an oily graphite layer with a thickness controlled at 0.05-0.08 mm in the aqueous graphite layer. B2: The tantalum cores with the formed oily graphite layer are sequentially dried and cured; B3: A tantalum core is made by coating an oily graphite dispersion surface layer with a layer of silver paste.

[0028] In step B1, the oily graphite and the additives are mixed at a mass ratio of 10:1.

[0029] In step B1, the additive is ultrasonically dispersed in an oily graphite solution for 30 minutes to obtain a mixture.

[0030] In step B2, the tantalum core is dried at room temperature for 40 minutes to remove excess solvent; after drying, it is cured at 120°C for 20 minutes.

[0031] The additive is nano-antimony-doped tin oxide, the average particle size of the mixture is 20 nm, and the solid content is 0.8%.

[0032] Example 2: like Figure 1 As shown, a method for reducing the leakage current of a tantalum capacitor under high temperature and high humidity conditions includes the step of impregnating a tantalum core after forming a tantalum pentoxide dielectric oxide film and a MnO2 layer with a graphite layer; the graphite layer includes an aqueous graphite layer and an oily graphite layer, and additives are added during the preparation of the oily graphite layer.

[0033] The preparation steps of the aqueous graphite layer include: A1: A water-based graphite layer with a thickness of 0.03 mm was prepared by impregnating the tantalum core after the formation of the dielectric oxide film and MnO2 layer; A2: The tantalum core after the formation of the water-based graphite layer is dried and cured sequentially.

[0034] In step A2, the tantalum core impregnated with the water-based graphite layer is dried at room temperature for 60 minutes to remove excess solvent.

[0035] In step A2, the tantalum core is dried and then cured at 200°C for 50 minutes.

[0036] The preparation steps of the oily graphite layer include: B1: The tantalum core after the formation of the aqueous graphite layer is immersed in a mixture of oily graphite and additives to form an oily graphite layer with a thickness controlled at 0.05-0.08 mm in the aqueous graphite layer. B2: The tantalum cores with the formed oily graphite layer are sequentially dried and cured; B3: A tantalum core is made by coating an oily graphite dispersion surface layer with a layer of silver paste.

[0037] In step B1, the oily graphite and the additives are mixed at a mass ratio of 20:3.

[0038] In step B1, the additive is ultrasonically dispersed in an oily graphite solution for 60 minutes to obtain a mixture.

[0039] In step B2, the tantalum core is dried at room temperature for 60 minutes to remove excess solvent; after drying, it is cured at 180°C for 40 minutes.

[0040] The additive is nano-antimony-doped tin oxide with an average particle size of 50 nm and a solid content of 3.0%.

[0041] Example 3: like Figure 1 As shown, a method for reducing the leakage current of a tantalum capacitor under high temperature and high humidity conditions includes the step of impregnating a tantalum core after forming a tantalum pentoxide dielectric oxide film and a MnO2 layer with a graphite layer; the graphite layer includes an aqueous graphite layer and an oily graphite layer, and additives are added during the preparation of the oily graphite layer.

[0042] The preparation steps of the aqueous graphite layer include: A1: A water-based graphite layer with a thickness of 0.03 mm was prepared by impregnating the tantalum core after the formation of the dielectric oxide film and MnO2 layer; A2: The tantalum core after the formation of the water-based graphite layer is dried and cured sequentially.

[0043] In step A2, the tantalum core impregnated with the water-based graphite layer is dried at room temperature for 50 minutes to remove excess solvent.

[0044] In step A2, the tantalum core is dried and then cured at 180°C for 30 minutes.

[0045] The preparation steps of the oily graphite layer include: B1: The tantalum core after the formation of the aqueous graphite layer is immersed in a mixture of oily graphite and additives to form an oily graphite layer with a thickness controlled at 0.05-0.08 mm in the aqueous graphite layer. B2: The tantalum cores with the formed oily graphite layer are sequentially dried and cured; B3: A tantalum core is made by coating an oily graphite dispersion surface layer with a layer of silver paste.

[0046] In step B1, the oily graphite and additives are mixed at a mass ratio of 16:2.

[0047] In step B1, the additive is ultrasonically dispersed in an oily graphite solution for 45 minutes to obtain a mixture.

[0048] In step B2, the tantalum core is dried at room temperature for 50 minutes to remove excess solvent; after drying, it is cured at 160°C for 30 minutes.

[0049] The additive is nano-antimony-doped tin oxide with an average particle size of 25 nm and a solid content of 2.5%.

[0050] Based on the existing 16V 220μF E-case capacitor, a 16V 220μF E-case capacitor was prepared by combining the methods of Examples 1-3.

[0051] The 16V 220μF E-shell capacitors prepared in Examples 1-3 and prior art were tested and evaluated. High-temperature and high-humidity tests were conducted on the prepared tantalum capacitors, including capacitance (C), equivalent series resistance (ESR), and leakage current (Id), to evaluate the improvement effect of leakage current and the electrical performance of the chip tantalum capacitors under high-temperature and high-humidity conditions. The test results showed that adding nano-antimony-doped tin oxide (ATO) material to an oily graphite solution to form Ag... + The adsorption layer reduced the high-temperature and high-humidity leakage current by 60.0%, and the capacitance and ESR of the tantalum capacitor were normal, as shown in the table below.

[0052] Due to the advanced nature of this technical solution, it can be widely applied in fields such as electronic component manufacturing and tantalum capacitor manufacturing. Firstly, this technical solution involves adding nano-antimony-doped tin oxide (ATO) material to an oil-based graphite solution, thereby increasing the content of Ag... + During migration, silver ions are adsorbed to form a stable adsorption layer, effectively blocking the migration path of silver ions, significantly enhancing the insulation resistance between the tantalum anode and the MnO2 cathode, and improving the leakage current problem of chip tantalum capacitors in high temperature and high humidity.

[0053] Meanwhile, the surface of the antimony-doped tin oxide (ATO) nanomaterial carries a permanent negative charge. Through the adsorption effect of the ATO nanomaterial, a stable adsorption layer is formed without affecting the electrical performance and lifespan of the capacitor. Secondly, the solution of this invention does not require changes to the overall structural design of the tantalum capacitor or the use of more tightly packed packaging materials, avoiding increased manufacturing costs and difficulties. It improves the leakage current of chip tantalum capacitors under high temperature and high humidity environments without affecting the normal performance of the tantalum capacitor. Finally, the preparation method of this invention is simple, low-cost, and easy to implement on existing production lines, showing good prospects for industrial application. Therefore, this technical solution has broad market application prospects and demand.

Claims

1. A method for reducing the leakage current of a tantalum capacitor under high temperature and high humidity conditions, characterized in that: The process includes impregnating a tantalum core with a graphite layer after forming a dielectric oxide film and a MnO2 layer; the graphite layer includes an aqueous graphite layer and an oil-based graphite layer, and additives are added during the preparation of the oil-based graphite layer.

2. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 1, characterized in that: The preparation steps of the aqueous graphite layer include: A1: An aqueous graphite layer is prepared by impregnating a tantalum core after the formation of a dielectric oxide film and a MnO2 layer. The thickness of the aqueous graphite layer is 0.02~0.05mm. A2: The tantalum core after the formation of the water-based graphite layer is dried and cured sequentially.

3. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 2, characterized in that: In step A2, the tantalum core impregnated with the water-based graphite layer is dried at room temperature for 10-30 minutes.

4. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 1, characterized in that: In step A2, the tantalum core is dried and then cured at 160-200℃ for 20-50 minutes.

5. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 1, characterized in that: The preparation steps of the oily graphite layer include: B1: The tantalum core after the formation of the aqueous graphite layer is immersed in a mixture of oily graphite and additives to form an oily graphite layer in the aqueous graphite layer. B2: The tantalum cores with the formed oily graphite layer are sequentially dried and cured.

6. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 5, characterized in that: In step B1, oily graphite and additives are mixed at a mass ratio of 10-20:1-3.

7. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 5, characterized in that: In step B1, the additive is ultrasonically dispersed in an oily graphite solution for 30-60 minutes to obtain a mixture.

8. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 5, characterized in that: In step B2, the tantalum core is dried at room temperature for 40-60 minutes; after drying, it is cured at 120-180℃ for 20-40 minutes.

9. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 1, characterized in that: The additive is nano-antimony-doped tin oxide.

10. The method for reducing leakage current of a tantalum capacitor under high temperature and high humidity conditions as described in claim 9, characterized in that: The average particle size of the nano-antimony-doped tin oxide is 20-50 nm, and the solid content is 0.8-3.0%.

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