Preparation method of chip tantalum capacitor

Abstract

The invention discloses a preparation method of a chip tantalum capacitor, and the method comprises the steps: mixing tantalum powder and a binder, carrying out the compression molding, and carrying out the sintering, thereby obtaining a tantalum powder core; the tantalum powder core is placed in electrolyte for anodic oxidation, and a dielectric layer is generated on the surface of the tantalum powder core; preparing a first outer layer inside and outside the dielectric layer, and preparing a second outer layer on the surface of the first outer layer to form a cathode layer; and packaging the tantalum powder core, and leading out an anode and a cathode to complete the preparation of the chip tantalum capacitor. The tantalum powder core with a porous structure is formed by adopting the tantalum powder with high specific volume and an optimized sintering process, so that the mechanical strength and the thermal stability of the tantalum capacitor are improved, and the tantalum capacitor can still work stably in a severe environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitor preparation, and particularly relates to a preparation method of a chip tantalum capacitor. Background Art

[0002] Due to advantages such as small volume, large capacitance, and good stability, tantalum capacitors are widely used in fields such as communication, computers, and consumer electronics. However, the existing chip tantalum capacitors have the following deficiencies:

[0003] 1. Reliability issue: Traditional tantalum capacitors are prone to failure under harsh environments such as high temperature and high humidity, affecting their service life.

[0004] 2. Capacitance stability: The capacitance of traditional tantalum capacitors varies greatly with conditions such as temperature and voltage, making it difficult to meet the requirements of high-precision circuits.

[0005] 3. ESR value: The equivalent series resistance (ESR) of traditional tantalum capacitors is relatively high, affecting their high-frequency performance.

[0006] The patent application document with the publication number CN105977030A discloses a preparation method of a tantalum capacitor with an ultra-large capacitance. This preparation method can effectively avoid the crystallization phenomenon in the anode energization process of the tantalum capacitor, and the prepared capacitor has the characteristics of large capacitance and high withstand voltage. However, this method does not solve the technical problem of improving the high-temperature life of the capacitor. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a preparation method of a chip tantalum capacitor.

[0008] The present invention is achieved through the following technical solutions.

[0009] A preparation method of a chip tantalum capacitor provided by the present invention includes the following steps:

[0010] A1: Mix tantalum powder with a binder and press them into a shape, and obtain a tantalum powder core after sintering;

[0011] A2: Place the tantalum powder core in an electrolyte and perform anodic oxidation to generate a dielectric layer on the surface of the tantalum powder core;

[0012] A3: Prepare a first outer layer inside and outside the dielectric layer, and prepare a second outer layer on the surface of the first outer layer to form a cathode layer;

[0013] A4: Package the tantalum powder core processed in step A3, and lead out the anode and cathode to complete the preparation of the chip tantalum capacitor.

[0014] Preferably, in step A1, the tantalum powder and the binder are mixed in a weight ratio of 80 - 105:5.

[0015] Preferably, in step A1, sintering is carried out in a vacuum furnace under the protection of an inert gas at 1500 - 1800 °C for 1 - 4 hours.

[0016] Preferably, the binder includes polyvinyl alcohol and polytetrafluoroethylene.

[0017] Preferably, in step A2, the electrolyte includes an oxalic acid solution and a phosphoric acid solution, and the dielectric layer is a tantalum pentoxide dielectric layer.

[0018] Preferably, the electrolyte includes a 0.1 - 0.5% oxalic acid solution and a 0.1 - 0.5% phosphoric acid solution.

[0019] Preferably, in step A2, anodic oxidation is carried out at a voltage of 120V.

[0020] Preferably, in step A3, the first outer layer material includes manganese dioxide, and the second outer layer material includes graphite and silver.

[0021] Preferably, in step A4, the tantalum powder core is encapsulated with epoxy resin.

[0022] Preferably, the specific volume of the tantalum powder is greater than or equal to 20000 CV / g.

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

[0024] 1. The present invention adopts a sintering process of mixing high - specific - volume tantalum powder and a binder to form a tantalum powder core with a porous structure, improving the mechanical strength and thermal stability of the tantalum capacitor, enabling it to still work stably in a harsh environment.

[0025] 2. The present invention forms a dense and uniform tantalum pentoxide dielectric layer by controlling the anodic oxidation process, effectively reducing the change rate of capacitance with temperature and voltage.

[0026] 3. The present invention adopts a composite cathode structure of a graphite layer and a silver paste layer, reducing the contact resistance of the cathode, thereby reducing the ESR value of the tantalum capacitor and improving the high - frequency performance. Specific Embodiments

[0027] The technical solutions of the present invention will be further described below, but the scope of protection claimed is not limited thereto.

[0028] Example 1:

[0029] A method for preparing a chip tantalum capacitor comprises the following steps:

[0030] A1: Mix tantalum powder with a binder and press it into shape, and obtain a tantalum powder core after sintering;

[0031] A2: Place the tantalum powder core in an electrolyte for anodic oxidation to generate a tantalum pentoxide dielectric layer on the surface of the tantalum powder core;

[0032] A3: Prepare the first outer layer of manganese dioxide inside and outside the dielectric layer, and coat the surface of the first outer layer with a graphite silver paste layer to prepare the second outer layer, forming the cathode layer;

[0033] A4: Encapsulate the tantalum powder core processed in step A3, and lead out the anode and cathode to complete the preparation of the chip tantalum capacitor.

[0034] In step A1, the tantalum powder and the binder are mixed at a weight ratio of 80:5.

[0035] In step A1, sintering is carried out in a vacuum furnace under argon protection at 1500 °C for 4 hours.

[0036] The binder is polyvinyl alcohol.

[0037] In step A2, the electrolyte is a 0.1% oxalic acid solution, and the dielectric layer is a tantalum pentoxide dielectric layer.

[0038] In step A2, anodic oxidation is carried out at a voltage of 120V.

[0039] In step A4, the tantalum powder core is encapsulated with epoxy resin.

[0040] The specific volume of the tantalum powder is 20000 CV / g.

[0041] Among them, the processes of anodic oxidation, the first outer layer, the second outer layer and the encapsulation of the tantalum powder core use the corresponding production processes of CAK45 chip tantalum capacitors.

[0042] Example 2:

[0043] A method for preparing a chip tantalum capacitor, comprising the following steps:

[0044] A1: Mix the tantalum powder and the binder and press them into shape, and obtain a tantalum powder core after sintering;

[0045] A2: Place the tantalum powder core in the electrolyte and carry out anodic oxidation to generate a tantalum pentoxide dielectric layer on the surface of the tantalum powder core;

[0046] A3: Prepare the first outer layer of manganese dioxide inside and outside the dielectric layer, and coat the surface of the first outer layer with a graphite silver paste layer to prepare the second outer layer, forming the cathode layer;

[0047] A4: Encapsulate the tantalum powder core processed in step A3, and lead out the anode and cathode to complete the preparation of the chip tantalum capacitor.

[0048] In step A1, the tantalum powder and the binder are mixed at a weight ratio of 105:5.

[0049] In the step A1, sintering is carried out at 1800 °C for 1 hour in a vacuum furnace under argon protection.

[0050] The binder is polytetrafluoroethylene.

[0051] In the step A2, the electrolyte is a 0.5% oxalic acid solution, and the dielectric layer is a tantalum pentoxide dielectric layer.

[0052] In the step A2, anodic oxidation is carried out at a voltage of 120 V.

[0053] In the step A4, the tantalum powder core is encapsulated with epoxy resin.

[0054] The specific volume of the tantalum powder is 20000 CV / g.

[0055] Among them, the processes of anodic oxidation, the first outer layer, the second outer layer and encapsulating the tantalum powder core use the corresponding production processes of CAK45 chip tantalum capacitors.

[0056] Example 3:

[0057] A method for preparing a chip tantalum capacitor comprises the following steps:

[0058] A1: Mix tantalum powder with a binder and press into a shape, and obtain a tantalum powder core after sintering;

[0059] A2: Place the tantalum powder core in an electrolyte for anodic oxidation to form a tantalum pentoxide dielectric layer on the surface of the tantalum powder core;

[0060] A3: Prepare a first outer layer of manganese dioxide inside and outside the dielectric layer, and coat a graphite silver paste layer on the surface of the first outer layer to prepare a second outer layer to form a cathode layer;

[0061] A4: Encapsulate the tantalum powder core processed in step A3, and lead out the anode and cathode to complete the preparation of the chip tantalum capacitor.

[0062] In the step A1, the tantalum powder and the binder are mixed in a weight ratio of 95:5.

[0063] In the step A1, sintering is carried out at 1600 °C for 2 hours in a vacuum furnace under argon protection.

[0064] The binder is polyvinyl alcohol.

[0065] In the step A2, the electrolyte is a 0.2% oxalic acid solution, and the dielectric layer is a tantalum pentoxide dielectric layer.

[0066] In the step A2, anodic oxidation is carried out at a voltage of 120 V.

[0067] In the step A4, the tantalum powder core is encapsulated with epoxy resin.

[0068] The specific capacitance of the tantalum powder is 25,000 CV / g.

[0069] Among them, the processes of anodic oxidation, the first outer layer, the second outer layer and encapsulating the tantalum powder core use the corresponding production processes of CAK45 chip tantalum capacitors.

[0070] Example 4:

[0071] A method for preparing a chip tantalum capacitor comprises the following steps:

[0072] A1: Mix tantalum powder with a binder and press into a shape, and obtain a tantalum powder core after sintering.

[0073] A2: Place the tantalum powder core in an electrolyte for anodic oxidation to form a tantalum pentoxide dielectric layer on the surface of the tantalum powder core.

[0074] A3: Prepare a first outer layer of manganese dioxide inside and outside the dielectric layer, and coat a graphite silver paste layer on the surface of the first outer layer to prepare a second outer layer to form a cathode layer.

[0075] A4: Encapsulate the tantalum powder core processed in step A3, and lead out the anode and cathode to complete the preparation of the chip tantalum capacitor.

[0076] In step A1, the tantalum powder and the binder are mixed at a weight ratio of 95:5.

[0077] In step A1, sinter at 1600 °C for 1 hour in a vacuum furnace under argon protection.

[0078] The binder is polytetrafluoroethylene.

[0079] In step A2, the electrolyte is a 0.1% phosphoric acid solution, and the dielectric layer is a tantalum pentoxide dielectric layer.

[0080] In step A2, anodic oxidation is carried out at a voltage of 120 V.

[0081] In step A3, the material of the first outer layer is a manganese dioxide layer, and the materials of the second outer layer are a graphite layer and a silver paste layer.

[0082] In step A4, the tantalum powder core is encapsulated with epoxy resin.

[0083] The specific capacitance of the tantalum powder is 25,000 CV / g.

[0084] Among them, the processes of anodic oxidation, the first outer layer, the second outer layer and encapsulating the tantalum powder core use the corresponding production processes of CAK45 chip tantalum capacitors.

[0085] Comparative Example 1:

[0086] A method for preparing a chip tantalum capacitor comprises the following steps:

[0087] A1: Press the tantalum powder into a shape, and obtain a tantalum powder core after sintering.

[0088] A2: Place the tantalum powder core in an electrolyte and perform anodic oxidation to generate a tantalum pentoxide dielectric layer on the surface of the tantalum powder core.

[0089] A3: Prepare a first outer layer of manganese dioxide inside and outside the dielectric layer, and coat a graphite silver paste layer on the surface of the first outer layer to prepare a second outer layer to form a cathode layer.

[0090] A4: Encapsulate the tantalum powder core processed in step A3, and lead out the anode and cathode to complete the preparation of the chip tantalum capacitor.

[0091] In step A1, sinter at 1600 °C for 1 hour in a vacuum furnace under argon protection.

[0092] In step A2, the electrolyte is a 0.2% oxalic acid solution, and the dielectric layer is a tantalum pentoxide dielectric layer.

[0093] In step A2, anodic oxidation is carried out at a voltage of 120 V.

[0094] In step A4, the tantalum powder core is encapsulated with epoxy resin.

[0095] The specific capacitance of the tantalum powder is 25000 CV / g.

[0096] Among them, the processes of anodic oxidation, the first outer layer, the second outer layer, and the encapsulation of the tantalum powder core use the corresponding production processes of CAK45 chip tantalum capacitors.

[0097] Comparative Example 2

[0098] Existing CAK45 chip tantalum capacitors.

[0099] Perform performance tests on the chip tantalum capacitors prepared in Examples 1-4 and the chip tantalum capacitors in Comparative Example 1, and the results are shown in the following table:

[0100]

[0101] It can be seen from the table that the chip tantalum capacitors prepared by the present invention have higher capacitance stability, lower ESR values, and longer service life. The high-temperature life of the capacitors prepared in Comparative Example 1 without a binder is reduced.

Claims

1. A preparation method of a chip tantalum capacitor, characterized in that, It includes the following steps: A1: Mix tantalum powder with a binder and press it into a shape, and obtain a tantalum powder core after sintering; A2: Place the tantalum powder core in an electrolyte and perform anodic oxidation to generate a dielectric layer on the surface of the tantalum powder core; A3: Prepare a first outer layer inside and outside the dielectric layer, and prepare a second outer layer on the surface of the first outer layer to form a cathode layer; A4: Package the tantalum powder core processed in step A3, and lead out the anode and cathode to complete the preparation of the chip tantalum capacitor.

2. The preparation method of a chip tantalum capacitor according to claim 1, characterized in that: In step A1, the tantalum powder and the binder are mixed in a weight ratio of 80-105:

5.

3. The manufacturing method of a chip tantalum capacitor according to claim 1, characterized in that: In step A1, sinter at 1500-1800 °C for 1-4 hours in a vacuum furnace under the protection of inert gas.

4. The preparation method of a chip tantalum capacitor as described in claim 1, characterized in that: The binder includes polyvinyl alcohol and polytetrafluoroethylene.

5. The preparation method of a chip tantalum capacitor according to claim 1, characterized in that: In step A2, the electrolyte includes an oxalic acid solution and a phosphoric acid solution, and the dielectric layer is a tantalum pentoxide dielectric layer.

6. The preparation method of a chip tantalum capacitor according to claim 1, characterized in that: The electrolyte includes a 0.1-0.5% oxalic acid solution and a 0.1-0.5% phosphoric acid solution.

7. The preparation method of a chip tantalum capacitor as described in claim 1, characterized in that: In step A2, anodic oxidation is performed at a voltage of 120V.

8. The preparation method of a chip tantalum capacitor as described in claim 1, characterized in that: In step A3, the material of the first outer layer includes manganese dioxide, and the material of the second outer layer includes graphite and silver.

9. The preparation method of a chip tantalum capacitor according to claim 1, wherein: In step A4, the tantalum powder core is packaged with epoxy resin.

10. The preparation method of a chip tantalum capacitor according to claim 1, characterized in that: The specific capacitance of the tantalum powder is greater than or equal to 20000 CV / g.

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