Preparation method of high-reliability MLCC

Abstract

The application relates to a preparation method of a high-reliability MLCC, and belongs to the technical field of electronic ceramic original devices. The MLCC after glue removal is subjected to heat treatment, the inner electrode layer is partially oxidized, and then sintering is performed; the oxidation layer on the surface of the inner electrode can improve the sintering shrinkage temperature, delays the shrinkage of the inner electrode layer, and through limiting the temperature and holding time and other parameters in the heat treatment process, the continuity and flatness of the inner electrode layer are improved, and the product performance of the MLCC is improved; the method does not need to modify the MLCC raw materials and manufacturing equipment, and can realize higher capacity and pressure resistance of the MLCC product by adopting a traditional sintering mode, and has a wide application prospect in the preparation of electronic materials.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramic components technology, and in particular to a method for preparing high-reliability MLCCs. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs), as fundamental electronic components, are widely used in fields such as electronic information, communication technology, integrated circuits, and aerospace, holding a vital strategic position in national economic and defense construction. MLCCs are primarily made of ceramic dielectric and metal internal electrode paste. To reduce costs, civilian MLCCs currently mostly use base metals, such as Ni, as the internal electrode material. Because the internal electrode material is easily oxidized in air and loses its conductivity, base metal internal electrode MLCCs require sintering in a N2+H2 reducing atmosphere to ensure the internal electrode is not oxidized. The conventional MLCC sintering process is generally debinding followed by sintering. Debinding removes organic matter from the blank, but because the internal electrode shrinks at a lower temperature and at a faster rate than the dielectric during sintering, it easily leads to a certain degree of sphericity after sintering, resulting in poor continuity and affecting the product's basic electrical performance and reliability. In high-capacitance MLCC products, since the dielectric thickness is generally less than 2μm, the spherical shape and discontinuity of the internal electrode can easily lead to defects in the dielectric. Therefore, the sintering state of the internal electrode has a more significant impact on the capacitance, withstand voltage, and reliability of high-capacitance MLCCs. Consequently, manufacturers have conducted extensive research on the continuity of the internal electrode in MLCCs, focusing on materials, processes, and equipment.

[0003] Patents CN108878143A, CN108695072A, and CN108878147A report that by adding nano-ceramic powder as a co-material to the Ni internal electrode slurry, preferably with a particle size <10nm and uniform distribution, the shrinkage of the Ni internal electrode during sintering is delayed, the spheroidization of the Ni internal electrode is suppressed, the electrode continuity is improved, and MLCC sintering cracking is prevented. Patent CN104174841A improves the dispersion of Ni powder and ceramic powder co-material in the Ni slurry, thereby improving the uniformity of the Ni electrode and enhancing the voltage resistance and reliability of ultra-high capacitance MLCC products. All of the above patents improve the materials. Patent KR2021016700W improves the continuity of the Ni internal electrode and enhances the electrical performance of the product by using a microwave sintering method in an inert gas environment and through rapid heating, but this method has low production capacity, complex equipment, and is not suitable for mass production.

[0004] To address the above issues, the current research focus is on developing a method that can achieve good continuity of internal electrodes without modifying materials or equipment, and thus fabricate high-reliability MLCCs using only traditional sintering methods. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a preparation method that can improve the capacity and withstand voltage characteristics of MLCCs. MLCC products prepared by this method have high reliability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for manufacturing high-reliability MLCCs, the method comprising the following steps:

[0007] S1. Mix the main components and dopants and grind them to make a porcelain slurry;

[0008] S2. The ceramic slurry is made into a film, an internal electrode layer is formed on the surface of the film, and the film is pressed into shape to obtain a green MLCC blank. The green MLCC blank is then debonded.

[0009] S3. After debinding, heat-treat the MLCC at 280-300℃ for 6-8 hours and then remove it.

[0010] S4. The heat-treated MLCC is sintered and post-treated to obtain the high-reliability MLCC.

[0011] Sintering is an essential process in MLCC manufacturing, enabling MLCC products to achieve ceramic-like structure and corresponding dielectric properties. However, the shrinkage temperature of the inner electrode layer during sintering is typically lower than that of the dielectric powder formed by the main components and dopants, and the shrinkage rate is faster. This can easily lead to a certain degree of spheroidization after sintering, resulting in poor electrode continuity and affecting the basic electrical properties and reliability of the MLCC product. Therefore, this invention involves heat-treating the MLCC after debinding to partially oxidize the inner electrode layer. During subsequent sintering, the oxide layer on the surface of the inner electrode can increase the sintering shrinkage temperature, delay the shrinkage of the inner electrode layer during subsequent sintering, improve the continuity and flatness of the inner electrode, and enhance the performance of the MLCC product.

[0012] The inventors further discovered that the heat treatment temperature has a significant impact on the performance of MLCCs. When the heat treatment temperature is within the range of this invention, the oxidation rate of the inner electrode layer can be reasonably set at 1.5%-2.4%, and the continuity of the inner electrode layer is >85%. If the heat treatment temperature is too high (>300°C), the oxidation rate of the inner electrode layer will be too high (>3%), making it difficult for the inner electrode layer to be reduced during sintering. If the heat treatment temperature is too low (<280°C), the oxidation rate of the inner electrode layer will be too low (<0.6%). Temperatures exceeding the range of this invention will also affect the continuity of the inner electrode layer.

[0013] Meanwhile, the inventors discovered that excessively long (>8h) or excessively short (<6h) heat treatment time can affect the oxidation rate and continuity of the inner electrode layer, resulting in poor capacity and withstand voltage of MLCC products.

[0014] In a preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, in step S1, the main component is an ABO3-based ceramic material, such as CaTiO3, BaZrO3 or BaTiO3, and the present invention selects BaTiO3.

[0015] As a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, in step S1, BaTiO3 is prepared by hydrothermal method.

[0016] In a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, the particle size of BaTiO3 in step S1 is 150-210 nm.

[0017] In a preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, in step S1, the dopant includes at least one of rare oxides, alkaline earth metal oxides or their carbonates, transition metal oxides or their carbonates, vanadium oxides, and chromium oxides.

[0018] As a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, in step S1, the dopant includes at least one of BaSiO3, Dy2O3, MnO, MgO, and V2O5.

[0019] In a preferred embodiment of the high-reliability MLCC preparation method of the present invention, in step S1, the molar percentage of the dopant in the main component is 2.5%-3.1%. By controlling the molar percentage of the dopant in the main component, the electrical performance of the MLCC product can be guaranteed to remain unaffected.

[0020] In a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, in step S1, the dopant contains the following components in molar percentage: BaSiO3 1.0%, Dy2O3 0.4%, MnO 0.15%, MgO 1.0%, and V2O5 0.5%.

[0021] As a preferred embodiment of the preparation method of the high reliability MLCC of the present invention, in step S1, the grinding method is as follows: after mixing the main component and dopant, solvent, dispersant, plasticizer and binder are added, and the mixture is mixed and ground in a sand mill to prepare a ceramic slurry to be cast.

[0022] As a more preferred embodiment of the preparation method of the high reliability MLCC of the present invention, in step S1, the grinding method is as follows: after mixing the main component and the dopant, the following components in parts by weight are added: 40-50 parts of solvent, 0.8-1.5 parts of dispersant, 4-6 parts of plasticizer, and 20-25 parts of binder.

[0023] In the most preferred embodiment of the high-reliability MLCC preparation method of the present invention, in step S1, the solvent during grinding is ethanol or toluene, and the dispersant, plasticizer and binder are all commonly used reagents in the art. The dispersant of the present invention is AKM0531 dispersant, the plasticizer is dioctyl phthalate (DOP) and the binder is polyvinyl butyral (PVB).

[0024] As a preferred embodiment of the high-reliability MLCC preparation method of the present invention, in step S2, the method of making the ceramic slurry into a film is as follows: the ceramic slurry is uniformly coated onto the film using a casting machine. This step requires ensuring that the coating surface is flat, and the thickness of the film can be selected according to actual needs.

[0025] In a more preferred embodiment of the method for preparing high-reliability MLCCs of the present invention, in step S2, the casting machine is a coating casting machine or a doctor blade casting machine.

[0026] As a preferred embodiment of the high-reliability MLCC preparation method of the present invention, in step S2, the method of forming an inner electrode layer on the surface of the film can be a method commonly used in the art. In the present invention, the inner electrode paste is printed on the surface of the film to form an inner electrode layer.

[0027] In a preferred embodiment of the high-reliability MLCC preparation method of the present invention, in step S2, the electrode paste is printed by screen printing or roller printing.

[0028] In a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, in step S2, the internal electrode paste is at least one of Ni paste, Cu paste, and Al paste.

[0029] In the most preferred embodiment of the high-reliability MLCC preparation method of the present invention, the internal electrode paste in step S2 is Ni paste.

[0030] As a preferred embodiment of the high-reliability MLCC preparation method of the present invention, the pressing step in step S2 is as follows: the film with the printed inner electrode layer is stacked according to the design requirements, the stacked block is laminated in a static press to ensure that each layer is tightly bonded, and after lamination, it is cut into MLCC blanks of the required size.

[0031] As a preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, the glue removal step in step S2 is as follows: the MLCC preform is heated to 400-450℃ in a nitrogen atmosphere at a heating rate of 0.5-1℃ / min and kept at the temperature for 3-4h to remove the glue. The purpose of glue removal is to remove the adhesive, plasticizer and other organic matter in the MLCC preform.

[0032] As a preferred embodiment of the preparation method of the high reliability MLCC of the present invention, the heat treatment step in step S3 is as follows: the MLCC after debinding is placed in a tube furnace and kept at a temperature of 280-300℃ for 6-8 hours before being taken out.

[0033] In a more preferred embodiment of the method for preparing the high-reliability MLCC of the present invention, the heat treatment in step S3 is carried out in an air atmosphere.

[0034] As a preferred embodiment of the preparation method of the high reliability MLCC of the present invention, the sintering step in step S4 is as follows: the heat-treated MLCC is placed in a tunnel furnace and heated to 1150-1180°C at a heating rate of 10-15°C / min in a reducing atmosphere, and sintered for 1-1.5h to obtain the MLCC blank.

[0035] In a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, in step S4, the reducing atmosphere during sintering is H2 with a concentration of 0.3%.

[0036] In a preferred embodiment of the high-reliability MLCC preparation method of the present invention, the post-processing in step S4 includes chamfering, end sealing, end burning, and deposition.

[0037] As a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, the chamfering step in step S4 is: grinding away the edges of the MLCC ceramic blank to expose the electrode and form chamfered ceramic particles.

[0038] As a more preferred embodiment of the preparation method of the high reliability MLCC of the present invention, in step S4, the end-sealing step is as follows: the exposed chamfered ceramic particles are erected, the broken ends are sealed with copper or silver to form copper or silver electrodes, and the electrode plates are bonded to form end-sealed ceramic particles.

[0039] As a more preferred embodiment of the preparation method of the high-reliability MLCC of the present invention, the step of sintering the end in step S4 is: sintering the end-sealing ceramic particles again to make the copper end or silver end in close contact with the electrode plate.

[0040] This invention also provides the application of the high-reliability MLCCs prepared by the method in electronic materials.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing a high-reliability MLCC. By heat-treating the MLCC after debinding, the inner electrode layer is partially oxidized and then sintered. During the sintering process, the oxide layer on the surface of the inner electrode can increase the sintering shrinkage temperature and delay the shrinkage of the inner electrode layer during subsequent sintering. By limiting parameters such as temperature and holding time during the heat treatment process, the continuity and flatness of the inner electrode are improved, thereby enhancing the product performance of the MLCC. The method described in the present invention does not require modification of the MLCC raw materials and manufacturing equipment. High capacity and withstand voltage of MLCC products can be achieved using traditional sintering methods, which has broad application prospects in the preparation of electronic materials. Attached Figure Description

[0042] Figure 1 This is a structural diagram of the MLCC described in this invention. Detailed Implementation

[0043] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments; unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially.

[0044] Example 1

[0045] The high-reliability MLCC fabrication method described in this embodiment includes the following steps:

[0046] S1. Take 1 mol of BaTiO3 powder with a particle size of 200 nm and mix it with 0.01 mol BaSiO3, 0.004 mol Dy2O3, 0.0015 mol MnO, 0.01 mol MgO and 0.005 mol V2O5. Add ethanol, toluene, AKM0531 dispersant, DOP and PVB. Mix and mill the above components in a sand mill to prepare a ceramic slurry to be cast.

[0047] S2. The ceramic slurry is cast into a film with a thickness of 1.4μm using a coating casting machine. Ni paste is printed on the surface of the film as an inner electrode layer. After stacking, lamination and cutting, MLCC green preform is obtained. The MLCC green preform is heated to 400℃ in a nitrogen atmosphere at a heating rate of 0.5℃ / min and held for 3h for debinding.

[0048] S3. Place the de-adhesive MLCC in an air atmosphere for heat treatment at a temperature of 280℃ for 6 hours.

[0049] S4. The heat-treated MLCC is placed in a tunnel furnace and heated to 1160°C at a heating rate of 10°C / min in a 0.3% H2 atmosphere. It is then held at this temperature for 1 hour for sintering to obtain an MLCC blank. After chamfering, end sealing, end firing, and deposition of the blank, the high-reliability MLCC is obtained.

[0050] Example 2

[0051] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment holding time is 7 hours, while the other steps are the same as in Embodiment 1.

[0052] Example 3

[0053] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment holding time is 8 hours, while the other steps are the same as in Embodiment 1.

[0054] Example 4

[0055] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment temperature is 290°C, while the other steps are the same as in Embodiment 1.

[0056] Example 5

[0057] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment temperature is 290℃ and the heat treatment holding time is 7h. All other steps are the same as in Embodiment 1.

[0058] Example 6

[0059] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment temperature is 290℃ and the heat treatment holding time is 8h. All other steps are the same as in Embodiment 1.

[0060] Example 7

[0061] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment temperature is 300°C, while the other steps are the same as in Embodiment 1.

[0062] Example 8

[0063] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment temperature is 300℃ and the heat treatment holding time is 7h. All other steps are the same as in Embodiment 1.

[0064] Example 9

[0065] The only difference between this embodiment and Embodiment 1 is that in step S3, the heat treatment temperature is 300℃ and the heat treatment holding time is 8h. All other steps are the same as in Embodiment 1.

[0066] Comparative Example 1

[0067] The only difference between this comparative example and Example 1 is that in step S3, the heat treatment holding time is 9 hours, while the other steps are the same as in Example 1.

[0068] Comparative Example 2

[0069] The only difference between this comparative example and Example 1 is that in step S3, the heat treatment temperature is 300℃ and the heat treatment holding time is 5h. All other steps are the same as in Example 1.

[0070] Comparative Example 3

[0071] The only difference between this comparative example and Example 1 is that in step S3, the heat treatment temperature is 310°C and the heat treatment holding time is 4 hours. All other steps are the same as in Example 1.

[0072] Comparative Example 4

[0073] The only difference between this comparative example and Example 1 is that in step S3, the heat treatment holding time is 5 hours, while the other steps are the same as in Example 1.

[0074] Comparative Example 5

[0075] The only difference between this comparative example and Example 1 is that heat treatment is not performed, i.e., step S3 is omitted; all other steps are the same as in Example 1.

[0076] Comparative Example 6

[0077] The only difference between this comparative example and Example 1 is that in step S3, the heat treatment temperature is 260°C, while the other steps are the same as in Example 1.

[0078] Comparative Example 7

[0079] The only difference between this comparative example and Example 1 is that in step S3, the heat treatment temperature is 300℃ and the heat treatment holding time is 9h. All other steps are the same as in Example 1.

[0080] Comparative Example 8

[0081] The only difference between this comparative example and Example 1 is that in step S3, the heat treatment temperature is 310°C, while the other steps are the same as in Example 1.

[0082] Example of effect

[0083] The MLCC products prepared in Examples 1-9 and Comparative Examples 1-8 of this invention were subjected to performance tests. The test results for each performance are shown in Table 1 below, and the test methods for each performance are as follows:

[0084] Electrode continuity test: Figure 1 The LT surface of the MLCC product shown is polished to the 1 / 2W position, and the SEM image of the polished surface is obtained by scanning electron microscopy (ZEISS SUPRA 55 SAPPHIRE). The length L1 of the discontinuity of the Ni internal electrode layer and the total length L2 of the Ni internal electrode layer are measured. The continuity of the Ni internal electrode layer = (L2-L1) / L2*100%.

[0085] Ni electrode oxidation rate: The magnetization M1 of the heat-treated MLCC was measured using a VersaLab vibrating sample magnetometer (VSM). The sample after testing was reduced in a 500℃, 1.0% H2 atmosphere for 1 hour to reduce the Ni oxide in the MLCC to Ni. The VSM test was performed again to obtain the magnetization M2 of the reduced sample. Then the Ni oxidation rate = (M2-M1) / M2*100%.

[0086] Pressure resistance (BDV) test: obtained using a pressure resistance testing machine (eec SE7430);

[0087] Capacitance (C) and loss (DF) testing: The test was conducted using a precision capacitance tester (Agilent E4980A) at 1V and 1KHz.

[0088] Insulation resistance (IR) test: The insulation resistance tester (HIOKI SM 7110) was used for the test, and the test conditions were 10V and 25℃.

[0089] Failure rate: 1000 MLCCs were sampled from each group of products and placed in an oven at 85℃ with an external DC voltage of 9.5V for 1000 hours. Products with a resistance of less than 1×106Ω were considered to have failed.

[0090] Table 1

[0091]

[0092]

[0093] As shown in Table 1, in Examples 1-9, when the heat treatment temperature was 280-300℃ and the heat treatment holding time was 6-8h, the oxidation rate of the Ni electrode was 1.5%-2.4%, and the continuity was higher than 89%. It can be seen that reasonable oxidation conditions and oxidation rate can effectively improve the continuity of Ni electrode. The improvement of Ni electrode continuity can effectively improve the capacity and withstand voltage of MLCC products, and its reliability is also improved. There were no failures in the lifespan of 1000 products.

[0094] Comparative Examples 1-2 suffered from excessively high heat treatment temperatures or excessively long heat treatment holding times after debinding, resulting in Ni electrode oxidation rates ≤0.6% and electrode continuity below 80%, with 3-4 electrodes failing out of 1000. In Comparative Example 3, the excessively high heat treatment temperature and excessively short heat treatment holding time led to a Ni electrode oxidation rate of 3.2%, which was difficult to reduce during sintering, resulting in an electrode continuity of only 75.5% and low capacity. This was because excessive Ni electrode oxidation caused Ni electrode volume expansion, leading to excessive stress and defects inside the product, resulting in a low BDV and a failure rate of 6 / 1000. Comparative Example 4 also suffered from poor electrode continuity due to excessively short heat treatment holding times. Comparative Example 5, without heat treatment, had a final Ni electrode oxidation rate of only 0.1%. Comparative Examples 6 and 7 also suffered from poor final performance because the heat treatment temperatures or times were outside the range provided by this invention. Comparative Example 8 suffered from severe Ni electrode oxidation and excessive volume expansion due to excessively high heat treatment temperatures, leading to cracking of the final product.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for manufacturing a high-reliability MLCC, characterized in that, The method includes the following steps: S1. Mix the main components and dopants and grind them to make a porcelain slurry; S2. The ceramic slurry is made into a film, an internal electrode layer is formed on the surface of the film, and the film is pressed into shape to obtain a green MLCC blank. The green MLCC blank is then debonded. S3. After debinding, heat-treat the MLCC at 280-300℃ for 6-8 hours and then remove it. The heat treatment was carried out in an air atmosphere; S4. The heat-treated MLCC is sintered and post-treated to obtain the high-reliability MLCC. In step S1, the grinding method is as follows: after mixing the main component and the dopant, add the following components by weight: 40-50 parts solvent, 0.8-1.5 parts dispersant, 4-6 parts plasticizer, and 20-25 parts binder. Mix and grind the above components in a sand mill to prepare a ceramic slurry to be cast. In step S4, the sintering step is as follows: the heat-treated MLCC is placed in a tunnel furnace and heated to 1150-1180℃ in a reducing atmosphere at a heating rate of 10-15℃ / min, and held at that temperature for 1-1.5h to obtain the MLCC ceramic blank.

2. The method for preparing a high-reliability MLCC as described in claim 1, characterized in that, In step S1, the main component is BaTiO3.

3. The method for preparing a high-reliability MLCC as described in claim 1, characterized in that, In step S1, the dopant includes at least one of rare oxides, alkaline earth metal oxides or their carbonates, transition metal oxides or their carbonates, vanadium oxides, and chromium oxides.

4. The method for preparing a high-reliability MLCC as described in claim 3, characterized in that, The dopant contains at least one of BaSiO3, Dy2O3, MnO, MgO, and V2O5.

5. The method for preparing a high-reliability MLCC as described in claim 1, characterized in that, In step S1, the molar percentage of the dopant in the main component is 2.5%-3.1%.

6. The method for preparing a high-reliability MLCC as described in claim 1, characterized in that, In step S2, the internal electrode slurry is at least one of Ni slurry, Cu slurry, and Al slurry.

7. The method for preparing a high-reliability MLCC as described in claim 6, characterized in that, The internal electrode paste is a Ni paste.

8. The method for preparing a high-reliability MLCC as described in claim 1, characterized in that, In step S2, the pressing and molding step is as follows: the film with the printed inner electrode layer is stacked, the stacked block is laminated, and then cut into MLCC blanks of the required size.

9. The method for preparing a high-reliability MLCC as described in claim 1, characterized in that, In step S4, the post-processing includes chamfering, end sealing, end burning, and deposition.

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