High-reliability MLCC structure and preparation method thereof

Abstract

The invention discloses a high-reliability MLCC structure and a preparation method thereof, and relates to the technical field of MLCC structures. The high-reliability MLCC structure comprises an inner electrode, a ceramic body, an outer electrode copper layer, a conductive resin layer, a nickel plating layer and a tin plating layer, the preparation method comprises the following specific steps: coating a to-be-terminated product with copper slurry, and drying to form an outer electrode copper layer; coating an outer electrode copper layer with conductive resin slurry, then performing curing treatment, and performing nickel plating and tin plating in sequence after a conductive resin layer is formed; wherein the thickness of the outer electrode copper layer is 20-40 [mu] m, and the coating depth of the copper paste is 220-400 [mu] m; the thickness of the conductive resin layer is 4-12 [mu] m, and the coating depth of the conductive resin layer is 70-100 [mu] m.

Description

Technical Field

[0001] This invention relates to the field of MLCC structure technology, specifically a high-reliability MLCC structure and its fabrication method. Background Technology

[0002] Currently, the commonly used MLCC terminal electrode structure typically employs a copper / nickel / tin three-layer structure. First, copper paste is physically adhered to the ceramic substrate. This is followed by high-temperature sintering to form a dense copper layer. Then, electroplating reduces nickel / tin onto the copper substrate. Existing copper layers generally consist of copper powder (spherical copper, sheet copper, etc.), glass powder, and resin. During the high-temperature sintering process, the resin in the copper paste easily volatilizes from the copper layer surface, creating voids. During electroplating, the nickel plating solution can easily corrode the copper layer and penetrate the ceramic substrate along these voids, causing product deterioration and affecting reliability. To address the issue of nickel intrusion in electroplating, existing technologies typically employ methods such as modifying the copper paste material or adding a barrier layer. However, these methods involve lengthy processes and high costs, making them difficult to scale up in actual production. Adding a barrier layer, which completely encloses the copper end to improve its density and reliability, carries the risk of exceeding dimensional limits and incurs high costs, while also being complex in its process. Therefore, there is an urgent need to find a highly reliable MLCC structure that can avoid the risks of exceeding dimensional limits and high costs, while also having a simple process that can be completed using existing equipment. Summary of the Invention

[0003] The purpose of this invention is to provide a high-reliability MLCC structure and its fabrication method to solve the problems raised in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A high-reliability MLCC structure includes an inner electrode, a ceramic body, an outer electrode copper layer, a conductive resin layer, a nickel plating layer, and a tin plating layer. The inner electrode is connected to one side of the outer electrode copper layer; the other side of the outer electrode copper layer consists of conductive resin, a nickel plating layer, and a tin plating layer, arranged sequentially from the inside to the outside. A method for fabricating a high-reliability MLCC structure includes the following fabrication steps: S1. After the inner electrode is exposed after the product is chamfered, the end is coated with copper paste; S2. The product coated with copper paste for the external electrode is dried to form a copper layer for the external electrode. S3. The copper layer of the outer electrode is coated with conductive resin paste; S4 involves curing the product coated with conductive resin slurry to form a conductive resin layer. S5. The product with the conductive resin layer is electroplated to form a nickel plating layer; S6. Electroplating is performed on the product with the nickel plating layer to form a tin plating layer; Preferably, the specific steps of S1 and S2 are as follows: the end of the beveled product is sealed with copper paste once, and the product covered with copper paste for the outer electrode is dried; Preferably, the thickness of the copper layer of the external electrode is 20μm~40μm, and the depth of the copper paste coating is 220μm~400μm; Preferably, the drying process parameters in S2 are as follows: nitrogen is used as the drying atmosphere, the nitrogen pressure is 0.060MPa~0.080MPa, the vacuum degree is -0.06MPa~-0.095MPa, the temperature is 450℃~600℃, and the time is 55min~75min; Preferably, the specific steps of S3 are: the product forming the outer electrode copper layer is subjected to secondary sealing with conductive resin, and the product coated with conductive resin slurry is dried. Preferably, the drying process parameters in step S3 are as follows: nitrogen is used as the drying atmosphere, the nitrogen pressure is 0.050MPa~0.070MPa, the vacuum degree is -0.055MPa~-0.085MPa, the temperature is 100℃~180℃, and the time is 5min~18min.

[0005] Preferably, the process parameters for the curing treatment in S4 are as follows: nitrogen is used as the drying atmosphere, the nitrogen pressure is 0.060MPa~0.070MPa, the vacuum degree is -0.075MPa~-0.095MPa, the temperature is 200℃~400℃, and the time is 60min~140min; Preferably, the thickness of the conductive resin layer is 4μm to 12μm, and the coating depth of the conductive resin is 70μm to 110μm.

[0006] Preferably, the preparation steps of the conductive resin slurry are as follows: s1: Epoxy resin and aniline are mixed, propylene glycol methyl ether is added, and the mixture is heated to 140°C for 4 hours under a nitrogen atmosphere. The mixture is then poured into anhydrous ethanol to precipitate, filtered and dried to obtain thermoplastic resin. s2: After dissolving the thermoplastic resin in a solvent by stirring, epoxy resin, curing agent and filler are added in sequence, and after mixing and degassing, conductive resin slurry is obtained; Preferably, in step s1, the mass ratio of epoxy resin, aniline, and propylene glycol methyl ether is 4:1:4.

[0007] Preferably, the conductive paste comprises the following components by weight: 50-80 parts thermoplastic resin, 2-5 parts epoxy resin, 200-400 parts filler, 2-5 parts curing agent, and 100-200 parts solvent. More preferably, the filler is prepared by compounding modified graphene and modified silver-coated copper in a mass ratio of 1:(0.5~2); The preparation steps of modified graphene are as follows: Mix graphene oxide and montmorillonite, add deionized water and sonicate for 6-8 hours, add polyvinylpyrrolidone and potassium tartrate, stir for 20-30 minutes, add silver nitrate, sonicate for 30 minutes, add sodium borohydride aqueous solution, stir for 30-50 minutes, centrifuge, wash, and dry to obtain modified graphene. The mass ratio of graphene oxide, montmorillonite, and silver nitrate is (1~3):10:(3~8); The preparation steps of modified silver-coated copper are as follows: copper powder is successively alkali washed and acid washed for activation, then washed with water and dispersed in deionized water. Polyvinylpyrrolidone and potassium tartrate are added, and the mixture is stirred for 20-30 min. Silver nitrate is then added, and the mixture is sonicated for 30-40 min. Sodium borohydride aqueous solution is then added, and the mixture is stirred for 30-50 min. After centrifugation and drying, the mixture is finally heat-treated to obtain silver-coated copper powder. The silver-coated copper powder is placed in deionized water, stirred in a 70℃ water bath and nitrogen gas is introduced. Styrene and azobisisobutyronitrile are added and reacted for 12 h. After washing with water and drying, modified silver-coated copper is obtained. The mass ratio of copper powder to silver nitrate is 1:(0.2-0.4); the mass ratio of silver-coated copper powder to styrene is 1:(20-30). The MLCC end caps prepared by the above method use light plating and copper paste coating to reduce the amount of precious metals used. The raw material price is lower than that of pure silver soft ends, effectively saving the manufacturer's production costs.

[0008] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a high-reliability MLCC structure and its preparation method, effectively preventing product deterioration caused by nickel plating intrusion. The MLCC structure includes an inner electrode, a ceramic dielectric, an outer electrode, a conductive resin, a nickel plating layer, and a tin plating layer. The ceramic dielectric contains a plurality of inner electrodes arranged at equal intervals, with both ends of the inner electrodes wrapped with outer electrodes. One end of each inner electrode extends to the outside of the ceramic dielectric and contacts the corresponding outer electrode. Both ends of the outer electrodes are wrapped with conductive resin, and a nickel plating layer and a tin plating layer are sequentially plated on the side of the conductive resin opposite to the outer electrodes. This invention reduces the reliability degradation caused by nickel plating intrusion by adding a conductive resin layer as a barrier layer. The conductive resin layer is made from thermoplastic resin combined with fillers and other additives. The fillers include modified graphene and modified silver-coated copper. The modified graphene mainly consists of montmorillonite inserted into the gaps between graphene oxide particles, with silver particles loaded on the surface to further enhance the conductivity of the graphene and strengthen the barrier performance of the conductive resin layer. The modified silver-coated copper introduces polystyrene segments onto its surface, improving the dispersion of the silver-coated copper in the resin matrix and achieving low-cost conductivity. The thickness of the conductive resin slurry barrier layer is controlled at 12 μm, while simultaneously reducing the end-capping length of the barrier layer. Using the end-capping tip of this invention for MLCCs not only improves the density of the end caps, reduces dimensional risks and economic costs, but also enhances the reliability of MLCC products. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the existing conductive resin layer end-capping process (1 is the inner electrode, 2 is the ceramic body, 3 is the outer electrode copper layer, 4 is the conductive resin layer, 5 is the nickel plating layer, and 6 is the tin plating layer). Figure 2 This is a partial enlarged view of the existing conductive resin layer end-capping process. Figure 3 This is a schematic diagram of the conductive resin layer end-capping process of the present invention; Figure 4 This is a partially enlarged view of the conductive resin layer capping process of the present invention; Figure 5 The images are scanning electron microscope (SEM) images of the end-capping process without a conductive resin layer in Comparative Example 1 of this invention at different magnifications (3a is 600×, 3b is 2500×, and 3c is 5000×). Figure 6 The following is a comparison diagram of the number of pinholes at the ends of Examples 1-5 and Comparative Example 1 under different end-sealing processes in this invention (4a is Comparative Example 1, 4b is Example 1, 4c is Example 2, 4d is Example 3, 4e is Example 4, and 4f is Example 5). Figure 7 The images show the end-plate nickel penetration images of Examples 1-5 and Comparative Example 1 in this invention (5a is Comparative Example 1, 5b is Example 1, 5c is Example 2, 5d is Example 3, 5e is Example 4, and 5f is Example 5). Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] In the experiment, the preparation steps of the conductive resin slurry were as follows: s1: Epoxy resin and aniline are mixed, propylene glycol methyl ether is added, and the mixture is heated to 140°C for 4 hours under a nitrogen atmosphere. The mixture is then poured into anhydrous ethanol to precipitate, filtered and dried to obtain thermoplastic resin. The mass ratio of epoxy resin, aniline and propylene glycol methyl ether is 4:1:4. s2: By weight, 60 parts of thermoplastic resin are placed in 150 parts of dimethylacetamide and stirred to dissolve. Then, 5 parts of epoxy resin, 5 parts of diethyltoluenediamine and 280 parts of filler are added in sequence. After mixing and degassing, conductive resin slurry is obtained. The filler is obtained by compounding modified graphene and modified silver-coated copper in a mass ratio of 1:1; The preparation steps of modified graphene are as follows: Take 5g of graphene oxide and 25g of montmorillonite, add 500mL of deionized water and sonicate for 8h, add 9g of polyvinylpyrrolidone and 3g of potassium tartrate, stir for 30min, add 15g of silver nitrate, sonicate for 30min, add 100mL of aqueous solution containing 40g of sodium borohydride, stir for 50min, centrifuge, wash, and dry to obtain modified graphene. The preparation steps of modified silver-coated copper are as follows: 5g of copper powder is successively alkali washed and acid washed for activation, then washed with water and dispersed in 100mL of deionized water. 1g of polyvinylpyrrolidone and 0.4g of potassium tartrate are added, and the mixture is stirred for 30min. 2g of silver nitrate is added, and the mixture is sonicated for 30min. 20mL of aqueous solution containing 5g of sodium borohydride is added, and the mixture is stirred for 30-50min. After centrifugation and drying, the mixture is finally heat-treated to obtain silver-coated copper powder. 5g of silver-coated copper powder is placed in 100mL of deionized water, stirred in a 70℃ water bath and nitrogen gas is introduced. 100g of styrene and 10g of azobisisobutyronitrile are added, and the mixture is reacted for 12h. After washing with water and drying, modified silver-coated copper is obtained. The epoxy resin is bisphenol A epoxy resin, model number 0164, purchased from Nantong Xingchen. Graphene oxide was prepared using the Hummers method; copper powder with a particle size of 1 μm was purchased from Aladdin. The copper paste consists of 75% copper powder, 4% ethyl cellulose, 13% terpineol and 8% tetrazol by weight; the ethyl cellulose was purchased from Aladdin, catalog number E110668. Example 1: This example provides a method for fabricating a high-reliability MLCC structure, including the following fabrication steps: S1. Using capacitors of model CSA0402X7R104K250GT as the end to be sealed, the ends are coated with copper paste. S2. The product coated with external electrode copper paste is placed in an oven for drying. Nitrogen is used as the drying atmosphere. The nitrogen pressure is 0.070 MPa and the vacuum degree in the oven is -0.06 MPa. The product is dried at 400℃ for 55 min to form external electrode copper layer 3. The thickness of the external electrode copper layer is 20 μm and the depth of copper paste coating is 220 μm. S3. Coat the outer electrode copper layer 3 with conductive resin slurry, place it in an oven to dry, use nitrogen as the drying atmosphere, the pressure of nitrogen is 0.060MPa, the vacuum degree in the oven is -0.055MPa, the temperature is 100℃, and the time is 5min. S4. The product coated with conductive resin slurry is cured by placing it in an oven with a nitrogen pressure of 0.065 MPa, a vacuum degree of -0.075 MPa, a temperature of 200℃, and a time of 60 min to form a conductive resin layer 4; the thickness of the conductive resin layer is 12 μm, and the coating depth of the conductive resin is 70 μm. S5. The product with the conductive resin layer formed is subjected to electroplating treatment using a nickel sulfamate electrolyte with a concentration of 300 g / L and a current density of 12 A / dm³. 2 The electroplating time is 120 minutes, forming a nickel plating layer of 5; S6. The product with the nickel plating layer is subjected to electroplating treatment using a 200 mL / L stannous methanesulfonate electrolyte and a current density of 12 A / dm³. 2 The electroplating time was 120 min, forming a tin plating layer 6, and obtaining structural sample 1.

[0012] Example 2: This example provides a method for fabricating a high-reliability MLCC structure, including the following fabrication steps: S1. Using capacitors of model CSA0402X7R104K250GT as the end to be sealed, the ends are coated with copper paste. S2. The product coated with external electrode copper paste is placed in an oven for drying. Nitrogen is used as the drying atmosphere. The nitrogen pressure is 0.070 MPa and the vacuum degree in the oven is -0.065 MPa. The product is dried at 450℃ for 60 min to form external electrode copper layer 3. The thickness of the external electrode copper layer is 25 μm and the depth of copper paste coating is 240 μm. S3. Coat the copper layer of the outer electrode with conductive resin slurry, place it in an oven to dry, use nitrogen as the drying atmosphere, the pressure of nitrogen is 0.060MPa, the vacuum degree in the oven is -0.06MPa, the temperature is 120℃, and the time is 8min. S4 The product coated with conductive resin slurry is placed in an oven for curing treatment. The nitrogen pressure is 0.065MPa, the vacuum degree is -0.08MPa, the temperature is 250℃, and the time is 80min, forming a conductive resin layer 4. The thickness of the conductive resin layer is 10μm, and the coating depth of the conductive resin is 80μm. S5. The product with the conductive resin layer formed is subjected to electroplating treatment using a nickel sulfamate electrolyte with a concentration of 300 g / L and a current density of 12 A / dm³. 2 The electroplating time is 120 minutes, forming a nickel plating layer of 5; S6. The product with the nickel plating layer is subjected to electroplating treatment using a 200 mL / L stannous methanesulfonate electrolyte and a current density of 12 A / dm³. 2 The electroplating time was 120 min, forming a tin plating layer 6, and obtaining structural sample 2.

[0013] Example 3: This example provides a method for fabricating a high-reliability MLCC structure, including the following fabrication steps: S1. Using capacitors of model CSA0402X7R104K250GT as the end to be sealed, the ends are coated with copper paste. S2. Place the product coated with external electrode copper paste in an oven for drying, using nitrogen as the drying atmosphere, with a nitrogen pressure of 0.070 MPa and a vacuum degree of -0.07 MPa in the oven. Dry at 500℃ for 65 min to form external electrode copper layer 3. The thickness of the external electrode copper layer is 30 μm, and the depth of copper paste coating is 260 μm. S3. Coat the copper layer of the outer electrode with conductive resin slurry, place it in an oven to dry, use nitrogen as the drying atmosphere, the pressure of nitrogen is 0.060MPa, the vacuum degree in the oven is -0.065MPa, the temperature is 140℃, and the time is 11min. S4 The product coated with conductive resin slurry is placed in an oven for curing treatment. The nitrogen pressure is 0.065MPa, the vacuum degree is -0.085MPa, the temperature is 300℃, and the time is 100min, forming a conductive resin layer 4. The thickness of the conductive resin layer is 8μm, and the coating depth of the conductive resin is 90μm. S5. The product with the conductive resin layer formed is subjected to electroplating treatment using a nickel sulfamate electrolyte with a concentration of 300 g / L and a current density of 12 A / dm³. 2 The electroplating time is 120 minutes, forming a nickel plating layer of 5; S6. The product with the nickel plating layer is subjected to electroplating treatment using a 200 mL / L stannous methanesulfonate electrolyte and a current density of 12 A / dm³. 2 The electroplating time was 120 min, forming a tin plating layer 6, and obtaining structural sample 3.

[0014] Example 4: This example provides a method for fabricating a high-reliability MLCC structure, including the following fabrication steps: S1. Using capacitors of model CSA0402X7R104K250GT as the end to be sealed, the ends are coated with copper paste. S2. The product coated with external electrode copper paste is placed in an oven for drying. Nitrogen is used as the drying atmosphere. The nitrogen pressure is 0.070 MPa and the vacuum degree in the oven is -0.075 MPa. The product is dried at 550℃ for 70 min to form external electrode copper layer 3. The thickness of the external electrode copper layer is 35 μm and the depth of copper paste coating is 280 μm. S3. Coat the copper layer of the outer electrode with conductive resin slurry, place it in an oven to dry, use nitrogen as the drying atmosphere, the pressure of nitrogen is 0.060MPa, the vacuum degree in the oven is -0.07MPa, the temperature is 160℃, and the time is 14min. S4 The product coated with conductive resin slurry is placed in an oven for curing treatment. The nitrogen pressure is 0.065MPa, the vacuum degree is -0.09MPa, the temperature is 350℃, and the time is 120min, forming a conductive resin layer 4. The thickness of the conductive resin layer is 6μm, and the coating depth of the conductive resin is 100μm. S5. The product with the conductive resin layer formed is subjected to electroplating treatment using a nickel sulfamate electrolyte with a concentration of 300 g / L and a current density of 12 A / dm³. 2 The electroplating time is 120 minutes, forming a nickel plating layer of 5; S6. The product with the nickel plating layer is subjected to electroplating treatment using a 200 mL / L stannous methanesulfonate electrolyte and a current density of 12 A / dm³. 2 The electroplating time was 120 min, forming a tin plating layer 6, and obtaining structural sample 4.

[0015] Example 5: This example provides a method for fabricating a high-reliability MLCC structure, including the following fabrication steps: S1. Using capacitors of model CSA0402X7R104K250GT as the end to be sealed, the ends are coated with copper paste. S2. Place the product coated with external electrode copper paste in an oven for drying, using nitrogen as the drying atmosphere, with a nitrogen pressure of 0.070 MPa and a vacuum degree of -0.08 MPa in the oven. Dry at 600℃ for 75 min to form external electrode copper layer 3. The thickness of the external electrode copper layer is 40 μm, and the depth of copper paste coating is 300 μm. S3. The copper layer of the outer electrode is coated with conductive resin slurry and dried in an oven using nitrogen as the drying atmosphere. The nitrogen pressure is 0.060 MPa, the vacuum degree in the oven is -0.075 MPa, the temperature is 180℃, and the time is 18 min. S4 The product coated with conductive resin slurry is placed in an oven for curing treatment. The nitrogen pressure is 0.065MPa, the vacuum degree is -0.095MPa, the temperature is 400℃, and the time is 140min, forming a conductive resin layer 4. The thickness of the conductive resin layer is 4μm, and the coating depth of the conductive resin is 120μm. S5. The product with the conductive resin layer formed is subjected to electroplating treatment using a nickel sulfamate electrolyte with a concentration of 300 g / L and a current density of 12 A / dm³. 2 The electroplating time is 120 minutes, forming a nickel plating layer of 5; S6. The product with nickel plating layer 5 is subjected to electroplating treatment using a 200 mL / L stannous methanesulfonate electrolyte and a current density of 12 A / dm³. 2 The electroplating time was 120 min, forming a tin plating layer 6, and obtaining structural sample 5.

[0016] Comparative Example: A method for fabricating an MLCC structure, the specific steps of which are as follows: S1. Using capacitor product of model CSA0402X7R104K250GT as the end to be sealed, copper paste is applied to the end; the product with copper paste applied to the outer electrode is placed in an oven for drying, with nitrogen as the drying atmosphere, nitrogen pressure of 0.070MPa, vacuum degree in the oven of -0.06MPa, and dried at 400℃ for 55min, the copper layer thickness is 50μm, and the coating depth is 400μm; S2. The product coated with copper paste for the external electrode is subjected to electroplating treatment using a nickel sulfamate electrolyte with a concentration of 300 g / L and a current density of 12 A / dm³. 2 The electroplating time is 120 minutes to form a nickel plating layer; S3. The product with the nickel plating layer is subjected to electroplating treatment using a 200 mL / L stannous methanesulfonate electrolyte and a current density of 12 A / dm³. 2 The electroplating time was 120 minutes to form a tin plating layer, resulting in structural sample 6. The parameters of Examples 1-5 and the comparative examples above have been compiled and are shown in Table 1: Table 1

[0017] Testing and experimentation: 1. Conduct experiments on Examples 1-5 and the comparative example above, and compare the following performance characteristics of the product end: 1) Compactness: The number of pinholes per unit area was compared and evaluated using SEM electron microscopy. 2) Weldability: The criterion is that 95% of the area should be welded uniformly and continuously; 3) High-acceleration aging: The judgment criteria are that after being treated with 200V at 125℃ for 96 hours, the absolute value of the capacitance change rate is ≤12.5% ​​and the loss is ≤12.5%; 4) Aging: The criterion is that after being treated with 200V at 125℃ for 1000h, the absolute value of the capacitance change rate is ≤12.5% ​​and the loss is ≤12.5%; The test results are shown in Table 2: 2. A cross-sectional analysis was performed on the CSA0402X7R104K250GT product to compare the specific nickel penetration. The results are shown in Table 3. Table 2

[0018] Table 3

[0019] Conclusion: The data above shows that the lack of a conductive resin layer in the control ratio has a significant impact on product performance.

[0020] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A high-reliability MLCC structure, characterized in that, The high-reliability MLCC structure includes: an inner electrode (1), a ceramic body (2), an outer electrode copper layer (3), a conductive resin layer (4), a nickel plating layer (5), and a tin plating layer (6); the inner electrode (1) is connected to one side of the outer electrode copper layer (3); the other side of the outer electrode copper layer (3) consists of conductive resin (4), a nickel plating layer (5), and a tin plating layer (6) from the inside to the outside.

2. A method for fabricating a high-reliability MLCC structure, characterized in that, The preparation steps include the following: S1. After the inner electrode (1) is exposed after chamfering, the end is coated with copper paste; S2. The product coated with copper paste for the outer electrode is dried to form a copper layer for the outer electrode (3). S3. Coating the copper layer of the outer electrode with conductive resin slurry (3); S4 cures the product coated with conductive resin slurry to form a conductive resin layer (4). S5. The product with the conductive resin layer is electroplated to form a nickel plating layer (5). S6. The product with the nickel plating layer is electroplated to form a tin plating layer (6).

3. The method for fabricating a high-reliability MLCC structure according to claim 2, characterized in that, The specific steps of S1 and S2 are as follows: the end of the chamfered product is sealed with copper paste once, and the product coated with copper paste for the outer electrode is dried; the thickness of the outer electrode copper layer (3) is 20μm~40μm, and the depth of the copper paste coating is 220μm~400μm; the drying process parameters are: nitrogen is used as the drying atmosphere, the pressure of nitrogen is 0.060MPa~0.080MPa, the vacuum degree is -0.06MPa~-0.095MPa, the temperature is 450℃~600℃, and the time is 55min~75min.

4. The method for fabricating a high-reliability MLCC structure according to claim 2, characterized in that, The specific steps of S3 are as follows: the product with the outer electrode copper layer (3) is subjected to secondary sealing with conductive resin, and the product coated with conductive resin slurry is dried; the drying process parameters are as follows: nitrogen is used as the drying atmosphere, the pressure of nitrogen is 0.050MPa~0.070MPa, the vacuum degree is -0.055MPa~-0.075MPa, the temperature is 100℃~180℃, and the time is 5min~10min.

5. The method for fabricating a high-reliability MLCC structure according to claim 2, characterized in that, The process parameters for curing in S4 are as follows: nitrogen is used as the drying atmosphere, the pressure of nitrogen is 0.060MPa~0.070MPa, the vacuum degree is -0.075MPa~-0.095MPa, the temperature is 200℃~400℃, and the time is 60min~140min; the thickness of the conductive resin layer (4) is 4μm~12μm, and the coating depth of the conductive resin is 70μm~100μm.

6. The method for fabricating a high-reliability MLCC structure according to claim 2, characterized in that, The preparation steps of the conductive resin slurry are as follows: s1: Mix epoxy resin with aniline, add propylene glycol methyl ether, heat to 140℃ under nitrogen atmosphere for 4-6 hours, then pour into anhydrous ethanol to precipitate, filter and dry to obtain thermoplastic resin. s2: After dissolving the thermoplastic resin in a solvent by stirring, epoxy resin, curing agent and filler are added in sequence, and after mixing and degassing, conductive resin slurry is obtained; In step s1, the mass ratio of epoxy resin, aniline, and propylene glycol methyl ether is 4:1:

4.

7. The method for fabricating a high-reliability MLCC structure according to claim 6, characterized in that, The conductive paste comprises the following components by weight: 50-80 parts thermoplastic resin, 2-5 parts epoxy resin, 200-400 parts filler, 2-5 parts curing agent, and 100-200 parts solvent; the filler is obtained by compounding modified graphene and modified silver-coated copper in a mass ratio of 1:(0.5-2).

8. The method for fabricating a high-reliability MLCC structure according to claim 7, characterized in that, The preparation steps of the modified graphene are as follows: graphene oxide and montmorillonite are mixed, deionized water is added and ultrasonicated for 6-8 hours, polyvinylpyrrolidone and potassium tartrate are added, and the mixture is stirred for 20-30 minutes. Silver nitrate is added, and the mixture is ultrasonicated for 30 minutes. Sodium borohydride aqueous solution is added and stirred for 30-50 minutes. The mixture is centrifuged, washed, and dried to obtain modified graphene. The mass ratio of graphene oxide, montmorillonite and silver nitrate is (1-3):10:(3-8).

9. The method for fabricating a high-reliability MLCC structure according to claim 7, characterized in that, The preparation steps of the modified silver-coated copper are as follows: copper powder is successively alkali washed and acid washed for activation, then washed with water and dispersed in deionized water. Polyvinylpyrrolidone and potassium tartrate are added, and the mixture is stirred for 20 min to 30 min. Silver nitrate is then added, and the mixture is sonicated for 30 min to 40 min. Sodium borohydride aqueous solution is then added, and the mixture is stirred for 30 min to 50 min. After centrifugation and drying, the mixture is finally heat-treated to obtain silver-coated copper powder. The silver-coated copper powder is placed in deionized water, stirred in a 70°C water bath and nitrogen gas is introduced. Styrene and azobisisobutyronitrile are added and reacted for 12 h. After washing with water and drying, the modified silver-coated copper is obtained.

10. The method for fabricating a high-reliability MLCC structure according to claim 9, characterized in that, The mass ratio of copper powder to silver nitrate is 1:(0.2~0.4); the mass ratio of silver-coated copper powder to styrene is 1:(20~30).

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