A sintering method of a multilayer chip ceramic capacitor

Abstract

The application discloses a sintering method of a multilayer chip ceramic capacitor, which comprises the following steps: 1) placing a coated nickel net in a nitrogen atmosphere with an oxygen content of 10-100 ppm for oxidation treatment; 2) uniformly stacking and arranging ceramic blanks on the coated nickel net subjected to the oxidation treatment for degassing treatment; 3) transferring the ceramic blanks and the coated nickel net subjected to the degassing treatment as a whole into a tunnel furnace, then introducing nitrogen and hydrogen, and then controlling the oxygen content in the tunnel furnace for three-stage sintering, so as to obtain the multilayer chip ceramic capacitor. The sintering method of the multilayer chip ceramic capacitor does not cause the product performance degradation problem caused by poor sintering atmosphere uniformity, the service life of the coated nickel net is long, the electric performance and reliability of the obtained MLCC are good, and the method is suitable for large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of ceramic capacitor technology, and more specifically to a sintering method for a multilayer chip ceramic capacitor. Background Technology

[0002] Multilayer ceramic chip capacitors (MLCCs) have advantages such as small size, compact structure, high reliability, and suitability for surface mount assembly, making them the most widely used and largest market share capacitor component. In recent years, with the advent of the 5G era and the popularization of electronic products such as laptops, satellite communications, smartphones, and wearable devices, MLCCs, as basic electronic components in circuits, have experienced rapid development, and market demand is increasing.

[0003] Currently, MLCCs are typically manufactured by sintering ceramic preforms at high temperatures on a sintering plate or a coated nickel mesh (pure nickel as the substrate, coated with a zirconium oxide layer). The method of sintering the ceramic preform on a sintering plate has the following disadvantages: 1) The sintering plate has a short service life and requires frequent replacement; 2) The poor permeability of the sintering plate leads to poor atmosphere uniformity within the sintering furnace, which in turn affects product performance; 3) The low thermal conductivity of the sintering plate results in high energy consumption during sintering. Compared to sintering the ceramic preform on a sintering plate, the method of sintering the ceramic preform on a coated nickel mesh offers advantages such as better atmosphere uniformity during sintering, better product sintering consistency, and lower energy consumption (due to the high thermal conductivity of the coated nickel mesh), making it a more promising application method. However, coated nickel mesh is prone to deformation during long-term use. Deformed and dented areas are prone to product stacking, which can lead to product performance degradation. Moreover, during the leveling process of coated nickel mesh, local peeling of the zirconium oxide coating may occur, which can significantly shorten the service life of coated nickel mesh. In addition, coated nickel mesh may absorb the furnace atmosphere during sintering, resulting in poor sintering atmosphere, which may lead to the deterioration of product reliability.

[0004] Therefore, developing a sintering method for multilayer ceramic chip capacitors with superior product performance is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a sintering method for multilayer ceramic chip capacitors.

[0006] The technical solution adopted in this invention is:

[0007] A sintering method for a multilayer ceramic chip capacitor includes the following steps:

[0008] 1) Place the coated nickel mesh in a nitrogen atmosphere with an oxygen content of 10ppm to 100ppm, and then heat it to perform an oxidation treatment;

[0009] 2) The ceramic blanks are evenly stacked and arranged on the nickel-coated mesh that has undergone peroxide treatment in step 1), and then the adhesive is removed.

[0010] 3) Transfer the ceramic green body and coated nickel mesh from step 2) that have undergone debinding treatment to a tunnel furnace, then introduce nitrogen and hydrogen gas, controlling the oxygen content inside the tunnel furnace to 1×10⁻⁶. -10 vol% ~ 10×10 -10 The first stage of sintering is carried out at vol%, and the oxygen content in the tunnel furnace is controlled at 1×10⁻⁶. -14 vol% ~ 1×10 -10 The second stage of sintering is carried out at vol%, and the oxygen content in the tunnel furnace is controlled at 1×10⁻⁶. -8 vol% ~ 10×10 -8 The third stage of sintering is carried out at vol%, which is to produce multilayer chip ceramic capacitors.

[0011] Preferably, the aperture of the coated nickel mesh in step 1) is 20 mesh to 120 mesh.

[0012] Preferably, the oxidation treatment in step 1) is carried out at 800℃~1100℃ for 1h~20h.

[0013] Preferably, in step 2), the stacking amount of the ceramic preform on the nickel-coated mesh is 1 g / cm³. 2 ~4g / cm 2 .

[0014] Preferably, the glue removal process in step 2) is carried out at 230℃~310℃ for 40h~80h.

[0015] Preferably, the adhesive removal process in step 2) is carried out in an air atmosphere.

[0016] Preferably, the specific operation of the first sintering stage in step 3) is as follows: the temperature is increased to 700℃ to 1000℃ at a heating rate of 1℃ / min to 3℃ / min, and then held for 1h to 10h.

[0017] Preferably, the specific operation of the second stage sintering in step 3) is as follows: the temperature is increased to 1150℃ to 1350℃ at a heating rate of 8℃ / min to 12℃ / min, and then held for 1h to 10h.

[0018] Preferably, the specific operation of the third sintering stage in step 3) is as follows: cooling to 800℃~1100℃ at a cooling rate of 8℃ / min~12℃ / min, and then holding at that temperature for 1h~10h.

[0019] Preferably, the oxygen content in step 3) is measured using a trace oxygen analyzer.

[0020] The beneficial effects of the present invention are: the sintering method of the multilayer chip ceramic capacitor of the present invention will not cause the product performance deterioration problem due to poor sintering atmosphere uniformity, and the coated nickel mesh has a long service life, and the obtained MLCC has good electrical performance and reliability, making it suitable for large-scale promotion and application.

[0021] Specifically, this invention forms a NiO film on the surface of the coated nickel mesh through oxidation pretreatment, which blocks the reaction between oxygen and nickel in the sintering atmosphere, effectively reducing the impact on the atmosphere of the sintering furnace's debinding zone during sintering. By controlling the sintering temperature and oxygen content in each section, the sintering atmosphere reaches or approaches the oxygen concentration of Ni / NiO equilibrium (balancing the "hydrogen absorption" in the high-temperature zone and the "oxygen absorption" in the re-oxidation zone), reducing the amount of reaction between the coated nickel mesh and oxygen in the atmosphere, improving the uniformity of the atmosphere around the product in the sintering furnace, and reducing the impact on the electrical performance and reliability of MLCCs. Detailed Implementation

[0022] The present invention will be further explained and described below with reference to specific embodiments.

[0023] Example 1:

[0024] A sintering method for a multilayer ceramic chip capacitor includes the following steps:

[0025] 1) Place the coated nickel mesh (20 mesh) in a nitrogen atmosphere with an oxygen content of 10 ppm, and then heat it to 800℃ for oxidation treatment for 10 h;

[0026] 2) The ceramic green body (barium titanate ceramic, size 1.0mm × 0.5mm × 0.5mm) is evenly stacked on the nickel-coated mesh that underwent peroxide treatment in step 1). The stacking amount of the ceramic green body on the nickel-coated mesh is 1g / cm². 2 Then, release the adhesive at 310°C in air for 80 hours;

[0027] 3) Transfer the ceramic blank and coated nickel mesh from step 2) that have undergone debinding treatment to a tunnel furnace, and then introduce nitrogen and hydrogen (the amount of nitrogen introduced during the entire sintering process should ensure that the atmosphere replacement rate in the tunnel furnace is 3 times per minute), and control the oxygen content in the tunnel furnace to 1×10⁻⁶. -10 The oxygen content (vol%) was determined using a trace oxygen analyzer. The temperature was increased to 700℃ at a rate of 2℃ / min and held for 1 hour as the first stage of sintering. The oxygen content in the tunnel furnace was then controlled to be 1×10⁻⁶. -14 The oxygen content in the tunnel furnace was controlled at 1×10⁻⁶ vol%, heated to 1150℃ at a heating rate of 10℃ / min, and held for 1 hour as the second stage of sintering. -8The third sintering stage involves cooling the material to 800℃ at a rate of 10℃ / min and holding it at that temperature for 1 hour. This process produces a multilayer ceramic chip capacitor.

[0028] Examples 2-7 and Comparative Examples 1-5:

[0029] The key parameters involved in the sintering process of multilayer ceramic chip capacitors in Examples 1-7 and Comparative Examples 1-5 are shown in the table below:

[0030] Table 1 shows the key parameters involved in Examples 1-7.

[0031]

[0032]

[0033] Table 2 shows the key parameters involved in Comparative Examples 1-5.

[0034]

[0035]

[0036] Performance testing:

[0037] The performance of the multilayer chip ceramic capacitors obtained by sintering in Examples 1-7 and Comparative Examples 1-5 was tested, and the test results are shown in the table below:

[0038] Table 3. Performance test results of the multilayer chip ceramic capacitors obtained by sintering in Examples 1-7 and Comparative Examples 1-5.

[0039]

[0040] Note: All performance tests were conducted in accordance with "GB / T 5968-2011 Fixed Capacitors for Electronic Equipment Part 9: Class 2 Ceramic Fixed Capacitors".

[0041] As shown in Table 3:

[0042] 1) In Examples 1 to 7, the coated nickel mesh was subjected to oxidation pretreatment, which reduced the influence of the coated nickel mesh on the atmosphere during sintering. Appropriate three-stage sintering parameters were selected for sintering. The dielectric layer of the product was dense, the electrode continuity was good, the oxygen vacancies in the dielectric layer were few, and the various electrical properties and lifespan of the product were qualified.

[0043] 2) Comparative Example 1 did not perform oxidation pretreatment on the coated nickel mesh. The coated nickel mesh reacted with the atmosphere in the high temperature zone and the cooling zone. The atmosphere around the product was more reducing. The barium titanate ceramic had more oxygen vacancies during sintering under a reducing atmosphere. The leakage current of the product was larger under voltage, the insulation resistance was reduced, and the product failed in the HALT test.

[0044] 3) The oxygen concentration in the dispensing section of Comparative Example 2 was too high, which caused oxidation of the internal electrodes of the product, product structural failure, capacity loss, insulation breakdown voltage and HALT test failure.

[0045] 4) In the high-temperature zone of Comparative Example 3, the oxygen concentration was below the lower limit, and the atmosphere was highly reducing. Under the reducing atmosphere, the oxygen vacancies in the barium titanate ceramic increased during sintering, resulting in a larger leakage current and a lower insulation resistance under voltage. The product failed the HALT test due to breakdown.

[0046] 5) The high-temperature section insulation temperature of Comparative Example 4 is too high, the product electrode shrinks too much and there is abnormal growth of grains in the dielectric layer, resulting in low product capacity, high loss, high leakage current under voltage, and reduced insulation resistance. The product breaks down and fails in HALT test.

[0047] 6) The cooling section temperature of Comparative Example 5 is too low, oxygen diffuses into the product and the reaction rate with oxygen vacancies in the product decreases, there are too many oxygen vacancies in the product after sintering, the leakage current of the product under voltage is too large, the insulation resistance is reduced, and the product breaks down and fails in HALT test.

[0048] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A sintering method for a multilayer chip ceramic capacitor, characterized in that, Includes the following steps: 1) Place the coated nickel mesh in a nitrogen atmosphere with an oxygen content of 10ppm to 100ppm, and then heat it to perform an oxidation treatment; 2) Arrange the ceramic blanks evenly on the nickel-coated mesh that has undergone peroxide treatment in step 1), and then perform the glue removal process; 3) Transfer the ceramic green body and coated nickel mesh from step 2) that have undergone debinding treatment to a tunnel furnace, then introduce nitrogen and hydrogen gas, controlling the oxygen content inside the tunnel furnace to 1×10⁻⁶. -10 vol%~10×10 -10 The first stage of sintering is carried out at vol%, and the oxygen content in the tunnel furnace is controlled at 1×10⁻⁶. -14 vol%~1×10 -10 The second stage of sintering is carried out at vol%, and the oxygen content in the tunnel furnace is controlled at 1×10⁻⁶. -8 vol%~10×10 -8 The third stage of sintering is carried out at vol%, which is to produce multilayer chip ceramic capacitors. Step 1) The oxidation treatment is carried out at 800℃~1100℃ for 1h~20h; Step 3) The specific operation of the first sintering stage is as follows: heat up to 700℃ to 1000℃ at a heating rate of 1℃ / min to 3℃ / min, and then hold for 1h to 10h. Step 3) The specific operation of the second stage sintering is as follows: heat up to 1150℃~1350℃ at a heating rate of 8℃ / min~12℃ / min, and then hold for 1h~10h. Step 3) The specific operation of the third sintering stage is as follows: cool down to 800℃~1100℃ at a cooling rate of 8℃ / min~12℃ / min, and then hold for 1h~10h.

2. The sintering method for a multilayer ceramic chip capacitor according to claim 1, characterized in that: Step 1) The coated nickel mesh has a mesh size of 20 to 120 mesh.

3. The sintering method for a multilayer ceramic chip capacitor according to claim 1, characterized in that: Step 2) The stacking amount of the ceramic preform on the nickel-coated mesh is 1 g / cm³. 2 ~4g / cm 2 .

4. The sintering method for a multilayer ceramic chip capacitor according to claim 1 or 3, characterized in that: Step 2) The glue removal process is carried out at 230℃~310℃ for 40h~80h.

5. The sintering method for a multilayer ceramic chip capacitor according to claim 1 or 3, characterized in that: Step 2) The adhesive removal process is carried out in an air atmosphere.

6. The sintering method for a multilayer ceramic chip capacitor according to claim 1, characterized in that: Step 3) The oxygen content is measured using a trace oxygen analyzer.

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