Modified resin for MLCC (multilayer ceramic capacitor), external electrode copper paste and preparation method of external electrode copper paste

Abstract

The invention discloses modified resin for MLCC, external electrode copper paste and a preparation method of the modified resin. The preparation method of the modified resin comprises the steps that ethyl cellulose serves as a raw material, ethyl cellulose with different substitution degrees and molecular weights is selected, 2-bromoisobutyryl bromide is used for esterification modification, and an EC-Br macroinitiator is prepared; the preparation method comprises the following steps: by taking EC-Br as an initiator, adding a solvent dimethylformamide into a Sureng bottle, adding monomers methyl methacrylate and butyl methacrylate, a ligand and a catalyst after the initiator is completely dissolved, and heating for polymerization reaction after three freeze-thaw cycle processes; and filtering the reaction solution with a neutral alumina column until the reaction solution is neutral, precipitating in deionized water, centrifuging, and carrying out vacuum drying until the weight is constant to obtain the modified resin EC-g-P (MMA-co-BMA). The modified resin is dissolved in an organic solvent to prepare an organic carrier, then the organic carrier is homogenized and mixed with metal copper powder and glass powder, and the external electrode copper paste with excellent rheological property and sintering property for MLCC end capping can be obtained after squeezing.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic pastes, and in particular relates to a modified resin for MLCC, an external electrode copper paste and a preparation method thereof. Background Art

[0002] Multilayer ceramic capacitors (MLCCs) are ranked first among the three major passive components in the electronics industry due to their unique structure and material advantages. MLCCs are in high demand and irreplaceable in communications equipment, automotive electronics, and industrial equipment.

[0003] Polyacrylic acid is a polymer prepared by polymerizing acrylic acid or acrylic acid derivatives or copolymerizing with other unsaturated compounds. It is a commonly used thickener for electronic pastes and exhibits excellent rheological and thixotropic properties. However, in copper electronic pastes, achieving commercial copper paste viscosity requires a relatively high dosage. Under a nitrogen atmosphere, this prevents the organic vehicle from being completely expelled during debinding and sintering, resulting in residual carbon. This hinders contact between copper particles, affects sintering neck formation and grain growth, and in turn, impacts the density and uniformity of the terminal electrodes, resulting in poor reliability and stability of MLCCs. Ethyl cellulose, another commonly used thickener for electronic pastes, exhibits excellent film-forming and adhesive properties, requiring only a small amount to achieve commercial copper paste viscosity. However, the paste exhibits poor rheological properties, exhibiting a small phase angle under low shear, behaving as a viscoelastic liquid and having difficulty maintaining its shape. End-capping can easily produce concave ends and sagging, resulting in poor end-capping morphology. Summary of the Invention

[0004] The main purpose of the present invention is to address the shortcomings of polyacrylic resin and ethyl cellulose in the application of MLCC copper end electronic paste, and provide a modified resin for MLCC, external electrode copper paste and preparation method thereof. The hydroxyl groups of ethyl cellulose that are not replaced by ethoxy groups are used to prepare ethyl cellulose-acrylic resin copolymer EC-gP (MMA-co-BMA) by ATRP graft polymerization. By changing the amount of methyl methacrylate and butyl methacrylate, the molecular weight and side chain length of the copolymer can be adjusted, thereby adjusting the thermal degradation performance, thixotropy and rheology of the resin, to obtain MLCC external electrode copper paste with good end-capping morphology, complete debinding sintering and pyrolysis, good sintering density and viscosity that meets commercial requirements.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a modified resin for MLCC comprises the following steps:

[0007] Using ethyl cellulose as raw material, ethyl cellulose with different substitution degree and molecular weight was selected and modified by esterification with 2-bromoisobutyryl bromide to prepare EC-Br macroinitiator.

[0008] EC-Br was used as the initiator, and dimethylformamide solvent was added to a Sulenk flask. After the initiator was completely dissolved, monomers methyl methacrylate and butyl methacrylate, a ligand, and a catalyst were added. After three freeze-thaw cycles, the polymerization reaction was carried out by heating. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. The modified resin EC-gP (MMA-co-BMA) was obtained by vacuum drying to constant weight.

[0009] Furthermore, the degree of substitution of the ethyl cellulose is within the range of 2.1 to 2.5, and the weight average molecular weight is within the range of 20,000 to 60,000.

[0010] Furthermore, the specific process for preparing EC-Br macroinitiator is as follows:

[0011] Ethyl cellulose and 4-dimethylaminopyridine were dissolved in tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was mixed evenly with tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 hours. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

[0012] Furthermore, the molar ratio of the macroinitiator EC-Br to the polymerization monomer is 1:x, and x ranges from 50 to 500.

[0013] Furthermore, the polymerization reaction temperature is 60° C. and the time is 24 h.

[0014] The present invention also includes a modified resin for MLCC, which is prepared using the preparation method of the modified resin provided by the present invention.

[0015] The present invention also includes a method for preparing an external electrode copper paste for MLCC, based on the modified resin provided by the present invention, comprising the following steps:

[0016] The modified resin and thixotropic agent provided by the present invention are dissolved in an organic solvent to obtain an organic carrier, the organic carrier, metal copper powder and glass powder are mixed in proportion, mixed using a homogenizer and then pulped using a three-roll pulping machine to obtain an external electrode copper paste for MLCC capping.

[0017] Furthermore, the thixotropic agent is specifically hydrogenated castor oil;

[0018] The organic solvent is specifically a mixed solvent of terpineol and diethylene glycol butyl ether acetate, or a mixed solvent of terpineol and diethylene glycol butyl ether, wherein the ratio of terpineol to diethylene glycol butyl ether acetate or diethylene glycol butyl ether in the two mixed solvents is 1:1;

[0019] The metal copper powder includes flake copper powder and spherical copper powder, both of which have a D50 of 0.5 to 1 μm and a mass ratio of 1:1.

[0020] Furthermore, in the organic vehicle, the mass ratio of the modified resin, the thixotropic agent and the organic solvent is x:y:z, where x is in the range of 15 to 30, y is in the range of 1.5 to 3, and z is in the range of 70 to 80;

[0021] The mass ratio of the organic carrier, the metal copper powder and the glass powder in the external electrode copper paste is a:b:c, where a is in the range of 20-30, b is in the range of 70-80, and c is in the range of 6-10.

[0022] The present invention also includes an external electrode copper paste for MLCC, which is prepared using the preparation method of the external electrode copper paste provided by the present invention.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. The present invention uses ethyl cellulose as a starting material, initiates the copolymerization of methyl methacrylate and butyl methacrylate through an ATRP reaction, and obtains a modified resin EC-gP (MMA-co-BMA); the resin is dissolved in an organic solvent to prepare an organic carrier, and then homogeneously mixed with metallic copper powder and glass powder, and slurry is rolled to obtain an MLCC copper-terminated electronic paste with excellent rheological and sintering properties; the present invention addresses the respective shortcomings of existing ethyl cellulose and acrylic resin and provides a modification method, which can adjust the molecular weight and side chain length of the resin by controlling the molecular weight and substitution degree of ethyl cellulose, the type and ratio of monomers, and further adjust the rheological and sintering properties of the copper paste, thereby achieving high-value utilization of ethyl cellulose and acrylic resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the preparation method of the present invention;

[0026] Figure 2 is the NMR image of the modified resin EC-gP (MMA-co-BMA) prepared in Example 2;

[0027] Figure 3 This is a graph showing an amplitude sweep test of the outer electrode copper paste obtained in Example 3;

[0028] Figure 4 1 and 2 are cross-sectional SEM images of MLCCs of Example 4 and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0030] Example 1

[0031] This embodiment takes the preparation of a modified resin and external electrode copper paste for MLCC as an example.

[0032] like Figure 1 As shown, a method for preparing a modified resin for MLCC comprises the following steps:

[0033] (1) Ethyl cellulose (degree of substitution 2.3, weight-average molecular weight 28295) and 4-dimethylaminopyridine were dissolved in 100 mL of tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was then mixed evenly with 5 mL of tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 h. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

[0034] (2) The macromolecular initiator EC-Br and 30 mL of solvent dimethylformamide were added to a Sulenk flask. After the initiator was completely dissolved, the ligand, catalyst, monomer methyl methacrylate (2.5 g, 25 mmol) and butyl methacrylate (3.55 g, 25 mmol) were added in sequence. After three freeze-thaw cycles (freezing-vacuuming-nitrogen filling), the mixture was placed in an oil bath and stirred at 60°C for 24 h. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. The modified resin EC-gP (MMA-co-BMA) was obtained by vacuum drying to constant weight.

[0035] Based on the obtained modified resin EC-gP (MMA-co-BMA), a copper paste for an external electrode of MLCC is prepared, comprising the following steps:

[0036] (3) Modified resin (2.0 g) and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (4 g) and diethylene glycol butyl ether acetate (4 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 min, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0037] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace for sintering at 790°C for 20 minutes to obtain the external electrode.

[0038] Testing showed that the bromine content of the EC-Br macroinitiator prepared in this example was 0.29 mmol / g, the weight-average molecular weight of the modified resin obtained by the ATRP reaction was 30532, and the copper paste prepared using the modified resin in this example had an initial phase angle of 52.2° in the linear viscoelastic region. Under low shear, it behaved as a viscous liquid. After capping, the copper paste had concave ends and sagging. The electrode density after sintering was 97.3%.

[0039] Example 2

[0040] This embodiment takes the preparation of a modified resin and external electrode copper paste for MLCC as an example.

[0041] A method for preparing a modified resin for MLCC comprises the following steps:

[0042] (1) Ethyl cellulose (degree of substitution 2.1, weight-average molecular weight 39624) and 4-dimethylaminopyridine were dissolved in 100 mL of tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was then mixed evenly with 5 mL of tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 h. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

[0043] (2) The macromolecular initiator EC-Br and 30 mL of solvent dimethylformamide were added to a Sulenk flask. After the initiator was completely dissolved, the ligand, catalyst, monomer methyl methacrylate (2.5 g, 25 mmol) and butyl methacrylate (3.55 g, 25 mmol) were added in sequence. After three freeze-thaw cycles, the mixture was placed in an oil bath and stirred at 60 ° C for 24 h. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. It was vacuum dried to constant weight to obtain the modified resin EC-gP (MMA-co-BMA).

[0044] like Figure 2 Shown is the NMR image of the prepared modified resin EC-gP (MMA-co-BMA);

[0045] Based on the obtained modified resin EC-gP (MMA-co-BMA), a copper paste for an external electrode of MLCC is prepared, comprising the following steps:

[0046] (3) Modified resin (2.0 g) and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (4 g) and diethylene glycol butyl ether acetate (4 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 min, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0047] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0048] Testing showed that the bromine content of the EC-Br macroinitiator prepared in this example was 0.45 mmol / g, the weight-average molecular weight of the modified resin obtained by the ATRP reaction was 40921, and the copper paste prepared using the modified resin in this example had an initial phase angle of 45.8° in the linear viscoelastic region. Under low shear, it behaved as a viscous liquid. After end-capping, there was a slight concave end but it was within the product qualification range. There was no sagging phenomenon, and the electrode density after sintering was 99.2%.

[0049] Example 3

[0050] This embodiment takes the preparation of a modified resin and external electrode copper paste for MLCC as an example.

[0051] A method for preparing a modified resin for MLCC comprises the following steps:

[0052] (1) Ethyl cellulose (degree of substitution 2.1, weight-average molecular weight 48522) and 4-dimethylaminopyridine were dissolved in 100 mL of tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was then mixed evenly with 5 mL of tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 h. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

[0053] (2) The macromolecular initiator EC-Br and 30 mL of solvent dimethylformamide were added to a Sulenk flask. After the initiator was completely dissolved, the ligand, catalyst, monomer methyl methacrylate (2.5 g, 25 mmol) and butyl methacrylate (3.55 g, 25 mmol) were added in sequence. After three freeze-thaw cycles, the mixture was placed in an oil bath and stirred at 60 ° C for 24 h. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. It was vacuum dried to constant weight to obtain the modified resin EC-gP (MMA-co-BMA).

[0054] Based on the obtained modified resin EC-gP (MMA-co-BMA), a copper paste for an external electrode of MLCC is prepared, comprising the following steps:

[0055] (3) Modified resin (2.0 g) and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (4 g) and diethylene glycol butyl ether acetate (4 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 min, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0056] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0057] Testing showed that the bromine content of the EC-Br macroinitiator prepared in this embodiment was 0.66 mmol / g, the weight-average molecular weight of the modified resin obtained by the ATRP reaction was 50492, and the copper paste prepared using the modified resin in this embodiment had an initial phase angle of 39.9° in the linear viscoelastic region. Under low shear, it behaved as an elastic solid and could maintain a good end-capping morphology. The electrode density after sintering was 99.9%, indicating excellent compactness.

[0058] like Figure 3 Shown is an amplitude sweep test curve of the obtained external electrode copper paste.

[0059] Example 4

[0060] This embodiment takes the preparation of a modified resin and external electrode copper paste for MLCC as an example.

[0061] A method for preparing a modified resin for MLCC comprises the following steps:

[0062] (1) Ethyl cellulose (degree of substitution 2.1, weight-average molecular weight 48522) and 4-dimethylaminopyridine were dissolved in 100 mL of tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was then mixed evenly with 5 mL of tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 h. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

[0063] (2) The macromolecular initiator EC-Br and 30 mL of solvent dimethylformamide were added to a Sulenk flask. After the initiator was completely dissolved, the ligand, catalyst, and monomer methyl methacrylate (5.0 g, 50 mmol) were added in sequence. After three freeze-thaw cycles, the mixture was placed in an oil bath and stirred at 60°C for 24 h. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. The modified resin EC-gP (MMA-co-BMA) was obtained by vacuum drying to constant weight.

[0064] Based on the obtained modified resin EC-gP (MMA-co-BMA), a copper paste for an external electrode of MLCC is prepared, comprising the following steps:

[0065] (3) Modified resin (2.0 g) and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (4 g) and diethylene glycol butyl ether acetate (4 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 min, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0066] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0067] Testing showed that the bromine content of the EC-Br macroinitiator prepared in this example was 0.66 mmol / g, the weight-average molecular weight of the modified resin obtained by the ATRP reaction was 48121, and the copper paste prepared using the modified resin in this example had an initial phase angle of 53.2° in the linear viscoelastic region. Under low shear, it behaved as a viscous liquid. After capping, the copper paste had a concave phenomenon, and sagging was observed to cause defects. The electrode density after sintering was 95.1%.

[0068] Example 5

[0069] This embodiment takes the preparation of a modified resin and external electrode copper paste for MLCC as an example.

[0070] A method for preparing a modified resin for MLCC comprises the following steps:

[0071] (1) Ethyl cellulose (degree of substitution 2.1, weight-average molecular weight 48522) and 4-dimethylaminopyridine were dissolved in 100 mL of tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was then mixed evenly with 5 mL of tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 h. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

[0072] (2) The macromolecular initiator EC-Br and 30 mL of solvent dimethylformamide were added to a Sulenk flask. After the initiator was completely dissolved, the ligand, catalyst, and monomer butyl methacrylate (7.1 g, 50 mmol) were added in sequence. After three freeze-thaw cycles, the mixture was placed in an oil bath and stirred at 60°C for 24 h. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. The modified resin EC-gP (MMA-co-BMA) was obtained by vacuum drying to constant weight.

[0073] Based on the obtained modified resin EC-gP (MMA-co-BMA), a copper paste for an external electrode of MLCC is prepared, comprising the following steps:

[0074] (3) Modified resin (2.0 g) and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (4 g) and diethylene glycol butyl ether acetate (4 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 min, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0075] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0076] Testing showed that the bromine content of the EC-Br macroinitiator prepared in this example was 0.66 mmol / g, the weight-average molecular weight of the modified resin obtained by the ATRP reaction was 54440, and the copper paste prepared using the modified resin in this example had an initial phase angle of 28.2° in the linear viscoelastic region. It behaved as an elastic solid under low shear conditions, exhibited a slight convex end phenomenon after end-capping, and had an electrode density of 99.7% after sintering.

[0077] Example 6

[0078] This embodiment takes the preparation of a modified resin and external electrode copper paste for MLCC as an example.

[0079] A method for preparing a modified resin for MLCC comprises the following steps:

[0080] (1) Ethyl cellulose (degree of substitution 2.1, weight-average molecular weight 48522) and 4-dimethylaminopyridine were dissolved in 100 mL of tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was then mixed evenly with 5 mL of tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 h. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

[0081] (2) The macromolecular initiator EC-Br and 30 mL of solvent dimethylformamide were added to a Sulenk flask. After the initiator was completely dissolved, the ligand, catalyst, monomer methyl methacrylate (5.0 g, 50 mmol) and butyl methacrylate (7.1 g, 50 mmol) were added in sequence. After three freeze-thaw cycles, the mixture was placed in an oil bath and stirred at 60°C for 24 h. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. The modified resin EC-gP (MMA-co-BMA) was obtained by vacuum drying to constant weight.

[0082] Based on the obtained modified resin EC-gP (MMA-co-BMA), a copper paste for an external electrode of MLCC is prepared, comprising the following steps:

[0083] (3) Modified resin (2.0 g) and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (4 g) and diethylene glycol butyl ether acetate (4 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 min, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0084] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0085] Testing showed that the bromine content of the EC-Br macroinitiator prepared in this embodiment was 0.66 mmol / g, the weight-average molecular weight of the modified resin obtained by the ATRP reaction was 77431, and the copper paste prepared using the modified resin in this embodiment had an initial phase angle of 18.2° in the linear viscoelastic region. Under low shear, it behaved as an elastic solid. After capping, the convex end phenomenon was severe, the surrounding copper layer was relatively thin, and there was leakage of the inner electrode after sintering. The terminal electrode density was 90.2%.

[0086] Example 7

[0087] This embodiment is based on the modified resin EC-gP (MMA-co-BMA) prepared in Example 5 to prepare the external electrode copper paste for MLCC, including the following steps:

[0088] The EC-gP (MMA-co-BMA) modified resin (Mw = 54440, 2.0 g) prepared in Example 5 and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (4 g) and diethylene glycol butyl ether (4 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 minutes, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0089] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0090] After testing, the copper paste prepared using the solvent system of this embodiment has an initial phase angle of 35.4° in the linear viscoelastic region, behaves as an elastic solid under low shear, has a slight convex end phenomenon after capping, and the electrode density after sintering is 96.2%.

[0091] Example 8

[0092] This embodiment is based on the modified resin EC-gP (MMA-co-BMA) prepared in Example 5 to prepare the external electrode copper paste for MLCC, including the following steps:

[0093] The EC-gP (MMA-co-BMA) modified resin (Mw = 54440, 2.0 g) prepared in Example 5 and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (8 g) to prepare an organic vehicle. The organic vehicle (10.0 g), metallic copper powder (36.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 minutes, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0094] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0095] After testing, the copper paste prepared using the solvent system of this embodiment has an initial phase angle of 55.2° in the linear viscoelastic region, behaves as a viscous liquid under low shear, has severe concave ends and sagging after the copper paste is capped, and the electrode density after sintering is 86.3%.

[0096] Example 9

[0097] This embodiment is based on the modified resin EC-gP (MMA-co-BMA) prepared in Example 5 to prepare the external electrode copper paste for MLCC, including the following steps:

[0098] The EC-gP (MMA-co-BMA) modified resin (Mw = 54440, 3.0 g) prepared in Example 5 and hydrogenated castor oil (0.2 g) were dissolved in a mixed solvent consisting of terpineol (6 g) and diethylene glycol butyl ether acetate (6 g) to prepare an organic vehicle. The organic vehicle (15.0 g), metallic copper powder (31.0 g), and glass powder (4.0 g) were homogenized in a homogenizer at 2000 rpm / min for 6 minutes, then removed and mixed using a three-roll mill to obtain an external electrode copper paste.

[0099] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0100] After testing, the copper paste prepared using the solvent system of this embodiment has an initial phase angle of 78.5° in the linear viscoelastic region. Under low shear, it behaves as a viscous liquid with low viscosity. After the copper paste is capped, there are severe concave ends and sagging phenomena. The electrode density after sintering is 90.3%.

[0101] Comparative Example 1

[0102] A method for preparing a copper slurry using ethyl cellulose as a thickener comprises the following steps:

[0103] To achieve commercial copper paste viscosity, a low amount of ethyl cellulose was used. Ethyl cellulose (1.0g) and hydrogenated castor oil (0.2g) were dissolved in a mixed solvent consisting of terpineol (4.5g) and diethylene glycol butyl ether acetate (4.5g) to prepare an organic vehicle. The organic vehicle (10.0g), metallic copper powder (36.0g), and glass powder (4.0g) were homogenized in a homogenizer at 2000rpm / min for 6 minutes, then removed and mixed using a three-roll mill to produce the external electrode copper paste.

[0104] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0105] After testing, the copper paste prepared using the resin of this example has an initial phase angle of 54.7° in the linear viscoelastic region, and behaves as a viscous liquid under low shear. After capping, the copper paste is severely concave and has sagging. The electrode density after sintering is 97.2%.

[0106] Comparative Example 2

[0107] A method for preparing a copper slurry using polymethyl methacrylate as a thickener comprises the following steps:

[0108] To achieve commercial copper paste viscosity, a large amount of polymethyl methacrylate was used. Polymethyl methacrylate (3.0g) and hydrogenated castor oil (0.2g) were dissolved in a mixed solvent consisting of terpineol (3.5g) and diethylene glycol butyl ether acetate (3.5g) to prepare an organic vehicle. The organic vehicle (10.0g), metallic copper powder (36.0g), and glass powder (4.0g) were homogenized in a homogenizer at 2000rpm / min for 6 minutes, then removed and mixed using a three-roll mill to produce the external electrode copper paste.

[0109] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0110] After testing, the copper paste prepared using the resin of this example had an initial phase angle of 44.9° in the linear viscoelastic region, behaved as an elastic solid under low shear, had a slight concave end and sagging after end sealing, and the electrode density after sintering was 89.7%, which was unqualified.

[0111] Comparative Example 3

[0112] A method for preparing a copper slurry using polybutyl methacrylate as a thickener comprises the following steps:

[0113] To achieve commercial copper paste viscosity, a large amount of polybutyl methacrylate was used. The organic vehicle was prepared by dissolving polybutyl methacrylate (3.0g) and hydrogenated castor oil (0.2g) in a mixed solvent consisting of terpineol (3.5g) and diethylene glycol butyl ether acetate (3.5g). The organic vehicle (10.0g), metallic copper powder (36.0g), and glass powder (4.0g) were homogenized in a homogenizer at 2000rpm / min for 6 minutes, then removed and mixed using a three-roll mill to produce the external electrode copper paste.

[0114] Finally, the 0603 specification MLCC was capped by a capping machine, and the capped copper paste was dried at 120°C for 10 minutes, and then sent into a nitrogen furnace and sintered at 790°C for 20 minutes to obtain the external electrode.

[0115] After testing, the copper paste prepared using the resin of this example has an initial phase angle of 24.2° in the linear viscoelastic region, behaves as an elastic solid under low shear, has a convex end phenomenon after sealing, and the electrode density after sintering is 86.7%, which is unqualified.

[0116] like Figure 4 Shown are SEM images of the MLCC cross sections of Example 4 and Comparative Examples 1, 2, and 3.

[0117] It should also be noted that, in this specification, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or apparatus comprising the element.

[0118] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a modified resin for MLCC, characterized in that: The following steps are involved: Using ethyl cellulose as raw material, ethyl cellulose with different substitution degree and molecular weight was selected and modified by esterification with 2-bromoisobutyryl bromide to prepare EC-Br macroinitiator. EC-Br was used as the initiator, and dimethylformamide solvent was added to a Sulenk flask. After the initiator was completely dissolved, monomers methyl methacrylate and butyl methacrylate, a ligand, and a catalyst were added. After three freeze-thaw cycles, the polymerization reaction was carried out by heating. The reaction solution was filtered through a neutral alumina column until neutral, precipitated in deionized water, and centrifuged. The modified resin EC-gP (MMA-co-BMA) was obtained by vacuum drying to constant weight.

2. The method for preparing a modified resin for MLCC according to claim 1, wherein: The degree of substitution of the ethyl cellulose is within the range of 2.1 to 2.5, and the weight average molecular weight is within the range of 20,000 to 60,000.

3. The method for preparing a modified resin for MLCC according to claim 1, wherein: The specific process of preparing EC-Br macroinitiator is as follows: Ethyl cellulose and 4-dimethylaminopyridine were dissolved in tetrahydrofuran and placed in an ice-water bath at 0°C. 2-Bromoisobutyryl bromide was mixed evenly with tetrahydrofuran and added dropwise to a beaker. The mixture was stirred at room temperature for 24 hours. After the reaction, the reaction solution was dripped into deionized water and filtered. The product was dried in a vacuum oven at 60°C to constant weight to obtain EC-Br macroinitiator.

4. The method for preparing a modified resin for MLCC according to claim 1, wherein: The molar ratio of the macromolecular initiator EC-Br to the polymerization monomer is 1:x, and the range of x is 50-500.

5. The method for preparing a modified resin for MLCC according to claim 1, wherein: The polymerization temperature was 60°C and the time was 24 h.

6. A modified resin for MLCC, characterized in that, The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing an external electrode copper paste for MLCC, characterized in that: Based on the modified resin according to claim 6, the method comprises the following steps: The modified resin and thixotropic agent described in claim 6 are dissolved in an organic solvent to obtain an organic carrier, the organic carrier, metal copper powder and glass powder are mixed in proportion, mixed using a homogenizer and then pulped using a three-roll pulping machine to obtain an external electrode copper paste for MLCC termination.

8. The method for preparing an external electrode copper paste for MLCC according to claim 7, characterized in that: The thixotropic agent is specifically hydrogenated castor oil; The organic solvent is specifically a mixed solvent of terpineol and diethylene glycol butyl ether acetate, or a mixed solvent of terpineol and diethylene glycol butyl ether, wherein the ratio of terpineol to diethylene glycol butyl ether acetate or diethylene glycol butyl ether in the two mixed solvents is 1:1; The metal copper powder includes flake copper powder and spherical copper powder, both of which have a D50 of 0.5 to 1 μm and a mass ratio of 1:

1.

9. The method for preparing an external electrode copper paste for MLCC according to claim 7, characterized in that: In the organic carrier, the mass ratio of the modified resin, the thixotropic agent and the organic solvent is x:y:z, where x is in the range of 15 to 30, y is in the range of 1.5 to 3, and z is in the range of 70 to 80; The mass ratio of the organic carrier, the metal copper powder and the glass powder in the external electrode copper paste is a:b:c, where a is in the range of 20-30, b is in the range of 70-80, and c is in the range of 6-10.

10. A copper paste for external electrodes of MLCC, characterized in that: The invention is prepared by the preparation method according to any one of claims 7 to 9.

Images