Method for improving voltage endurance capability of chip tantalum capacitor

Abstract

The invention discloses a method for improving the voltage endurance capability of a chip tantalum capacitor, and belongs to the technical field of capacitor manufacturing, and the method comprises the steps: enabling an anode tantalum block formed through a powder metallurgy method to generate a dielectric oxide film in an acid solution, then placing the anode tantalum block in sputtering coating equipment, introducing oxygen, taking tantalum as a target material, and carrying out sputtering coating on the anode tantalum block; a layer of tantalum pentoxide film is generated on the surface; and finally, the chip tantalum capacitor is formed by coating a manganese dioxide or polymer cathode. The invention relates to a method for improving the voltage endurance capability of a chip-type tantalum capacitor, which plays a role in improving the reliability of the chip-type tantalum capacitor.

Description

Technical Field

[0001] The invention belongs to the technical field of capacitors, and in particular relates to a method for improving the withstand voltage capability of a chip tantalum capacitor. Background Art

[0002] Solid electrolyte tantalum capacitors are one of the most important basic electronic components in electronic engineering, widely used in communications equipment, audio-visual systems, electrical instruments, and other fields. Tantalum metal surfaces can be chemically or electrochemically formed with a dense and uniform dielectric oxide film, a process known as formation. The properties of this dielectric oxide film significantly influence the withstand voltage and reliability of electrolytic capacitors. Due to the skin effect, current is concentrated on the surface of a conductor, with the outer layer carrying a greater current. Therefore, the dielectric oxide film on the outer layer of the tantalum anode is particularly important.

[0003] US11004615B2 provides a solid electrolytic capacitor for use at high temperatures, which is to form a dielectric oxide film on the surface and inside of the anode tantalum block in an acidic solution, and then continue to grow the oxide film in an acidic solution with lower conductivity than the first stage in the second stage. CN103354178A provides a method for manufacturing a dielectric oxide film of a solid tantalum capacitor resistant to high voltage, which is to form a dielectric oxide film on the anode tantalum block in an ethylene glycol solution, and then immerse the anode tantalum block in an ethylene glycol solution again and apply a voltage higher than the primary formation voltage for secondary formation to improve the product's withstand voltage. The above methods all attempt to increase the thickness of the tantalum pentoxide oxide film on the surface of the anode tantalum block by performing two chemical methods in the solution to improve the withstand voltage performance. However, the second use of the chemical method in the solution will inevitably generate a dielectric oxide film of a certain thickness inside the anode tantalum block, resulting in a significant reduction in the capacity of the tantalum capacitor. Summary of the Invention

[0004] In order to solve the above problems, the present invention aims to provide a method for improving the withstand voltage capability of chip tantalum capacitors.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: a method for improving the withstand voltage capability of a chip tantalum capacitor, comprising the following steps:

[0006] Step 1: preparing a tantalum block by preparing tantalum powder to obtain a tantalum block with a porosity of 20%-80%;

[0007] Step 2: Forming a dielectric oxide film: placing the tantalum block in an acidic solution to form a dielectric oxide film;

[0008] Step 3: Physically generate a thickened film layer. Place the tantalum block processed in step 2 in a sputtering device. Use tantalum as the target and sputter-deposit a tantalum pentoxide film on the surface in an oxygen atmosphere. The process parameters are: temperature 10-120°C, sputtering power 500-5000W, vacuum 0.001-0.1Pa, sample stage speed 1-30r / min, and oxygen flow rate 10-200mL / min.

[0009] Step 4: Cover the surface of the tantalum block in step 3 with manganese dioxide or a polymer cathode and encapsulate it to form a chip tantalum capacitor.

[0010] Furthermore, the method for preparing tantalum blocks from tantalum powder in step 1 is powder metallurgy.

[0011] Furthermore, the acidic solution in step 2 is one or more of phosphoric acid, nitric acid, acetic acid, and hydrochloric acid.

[0012] Furthermore, in step 3, the thickness of the outermost oxide film is increased by sputtering, and the increased thickness ranges from 6 to 600 nm.

[0013] Compared with existing technologies, the present invention has the following advantages: By combining chemical and physical methods, the thickness of the outermost oxide film is increased without causing further growth of the inner oxide film. This improves the withstand voltage capability of chip tantalum capacitors without significantly affecting their capacitance. DETAILED DESCRIPTION

[0014] The present invention is further described below with reference to specific embodiments. However, it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various modifications, substitutions and changes made according to common technical knowledge and customary means in the field are included in the scope of the present invention.

[0015] Comparative Example 1: A tantalum anode block with a porosity of 80% and a specification of 20-22-B was placed in hydrochloric acid to form a dielectric oxide film with a withstand voltage of 35V and a capacity retention rate of 91.5%.

[0016] In Example 1, an anode tantalum block with a porosity of 80% was placed in hydrochloric acid to form a dielectric oxide film. The tantalum block with the dielectric oxide film was then placed in a sputtering device. Tantalum was used as a target and a tantalum pentoxide film with a thickness of 200 nm was sputtered on the surface in an oxygen atmosphere. The sputtering parameters were: power 2500 W, oxygen flow rate 80 mL / min, vacuum degree 0.01 Pa, temperature 80° C., and rotation speed 10 r / min.

[0017] The obtained capacitor had a withstand voltage of 51 V and a capacity retention rate of 98%.

[0018] Comparative Example 2: A tantalum anode block with a porosity of 20% and a specification of 16V-10μF-A was placed in hydrochloric acid to form a dielectric oxide film with a withstand voltage of 30V and a capacity retention rate of 95%.

[0019] In Example 2, an anode tantalum block with a porosity of 20% was placed in a mixture of nitric acid and acetic acid at a volume ratio of 1:2 to form a dielectric oxide film. The tantalum block with the dielectric oxide film was then placed in a sputtering device. Tantalum was used as a target, and a tantalum pentoxide film with a thickness of 175 nm was sputtered on the surface in an oxygen atmosphere. The sputtering parameters were: power 3000 W, oxygen flow rate 100 mL / min, vacuum 0.05 Pa, temperature 100° C., and rotation speed 20 r / min.

[0020] The obtained capacitor had a withstand voltage of 49 V and a capacity retention rate of 98.7%.

[0021] Comparative Example 3: An anode tantalum block with a porosity of 40% and a specification of 25V-47μF-E is placed in phosphoric acid to form a dielectric oxide film with a withstand voltage of 43V and a capacity retention rate of 93%.

[0022] In Example 3, an anode tantalum block with a porosity of 400% was placed in phosphoric acid to form a dielectric oxide film. The tantalum block with the dielectric oxide film was then placed in a sputtering device. Tantalum was used as a target and a tantalum pentoxide film with a thickness of 230 nm was sputtered on the surface in an oxygen atmosphere. The sputtering parameters were: power 5000 W, oxygen flow rate 200 mL / min, vacuum degree 0.1 Pa, temperature 120° C., and rotation speed 30 r / min.

[0023] The obtained capacitor had a withstand voltage of 58 V and a capacity retention rate of 96%.

[0024] The above describes in detail the method for improving the withstand voltage of chip tantalum capacitors provided by the present invention. Specific examples are used herein to illustrate the structure and operating principles of the present invention. The description of the above embodiments is intended only to facilitate understanding of the method and core concepts of the present invention. It should be noted that those skilled in the art will be able to make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications fall within the scope of protection of the claims.

Claims

1. A method for improving the withstand voltage of a chip tantalum capacitor, characterized by: The following steps are included: Step 1: preparing a tantalum block by preparing tantalum powder to obtain a tantalum block with a porosity of 20%-80%; Step 2: Forming a dielectric oxide film: placing the tantalum block in an acidic solution to form a dielectric oxide film; Step 3: Physically generate a thickened film layer. Place the tantalum block processed in step 2 in a sputtering device. Use tantalum as the target and sputter-deposit a tantalum pentoxide film on the surface in an oxygen atmosphere. The process parameters are: temperature 10-120°C, sputtering power 500-5000W, vacuum 0.001-0.1Pa, sample stage speed 1-30r / min, and oxygen flow rate 10-200mL / min. Step 4: Cover the surface of the tantalum block in step 3 with manganese dioxide or a polymer cathode and encapsulate it to form a chip tantalum capacitor.

2. The method for improving the withstand voltage capability of a chip tantalum capacitor according to claim 1, wherein: The method for preparing tantalum powder into tantalum blocks in step 1 is powder metallurgy.

3. The method for improving the withstand voltage of a chip tantalum capacitor according to claim 1, wherein: The acidic solution in step 2 is one or more of phosphoric acid, nitric acid, acetic acid, and hydrochloric acid.

4. The method for improving the withstand voltage capability of a chip tantalum capacitor according to claim 3, wherein: In step 3, the thickness of the outermost oxide film is increased by sputtering, and the increased thickness ranges from 6 to 600 nm.