CN114783770B - External electrode slurry of multilayer ceramic capacitor and preparation method thereof - Google Patents
External electrode slurry of multilayer ceramic capacitor and preparation method thereof Download PDFInfo
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Images
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/228—Terminals
- H01G4/232—Terminals electrically connecting two or more layers of a stacked or rolled capacitor
- H01G4/2325—Terminals electrically connecting two or more layers of a stacked or rolled capacitor characterised by the material of the terminals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/14—Conductive material dispersed in non-conductive inorganic material
- H01B1/16—Conductive material dispersed in non-conductive inorganic material the conductive material comprising metals or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/30—Stacked capacitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/06—Solid dielectrics
- H01G4/08—Inorganic dielectrics
- H01G4/12—Ceramic dielectrics
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Inorganic Chemistry (AREA)
- Ceramic Capacitors (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
Abstract
The invention provides external electrode slurry of a multilayer ceramic capacitor and a preparation method thereof. The invention also provides a method for preparing the external electrode slurry of the multilayer ceramic capacitor by using the grinder. The connectivity of the external electrode and the internal electrode is improved by adding the second metal powder; the homogeneity of the slurry is improved by using a mill. The sintered MLCC inner and outer electrode slurry has the advantages of good connectivity, high quality, simple production process and capability of realizing industrial production.
Description
Technical Field
The invention belongs to the field of electrode slurry, and relates to external electrode slurry of a multilayer ceramic capacitor with high connectivity and high quality with an internal electrode and a preparation method thereof.
Background
The electronic components include capacitors, inductors, piezoelectric elements, piezoresistors, thermistors, and the like. Among Ceramic electronic components, a multilayer Ceramic Capacitor (MLCC), which is one of three major types of passive components, has advantages of small volume, large capacity, and easy mounting.
Due to the advantages, the multilayer ceramic capacitor has very wide application in the fields of mobile phones, digital terminals, automobiles, aerospace, military industry and the like, the world demand for MLCC is continuously increased, and the market prospect is very wide. The multilayer ceramic capacitor is used for charging and discharging, and its size and number of layers are different depending on the application and capacity. With the miniaturization of electronic products, the market demand for multilayer ceramic capacitors is also moving toward miniaturization and high capacity.
In recent years, in terms of external electrodes, copper paste is used at home and abroad as external electrode paste of multilayer ceramic capacitors in order to reduce production cost, but copper powder is easily oxidized, has low sintering activity, is easy to form sintering defects, and often shows poor compactness after end-capping sintering, insufficient connectivity of internal and external electrodes and the like, thereby seriously affecting the yield and reliability of products. Therefore, it is necessary to develop an external electrode paste that can improve this problem.
In the preparation process of the slurry, most manufacturers use a three-roll mill, the copper external electrode slurry for the MLCC has high viscoelasticity, the conditions of material throwing, material leakage and the like are easily generated in the rolling process, the slurry components are not uniform in the preparation process, and the consistency of the slurry is poor.
Therefore, in order to solve the defects in the prior art, it is necessary to develop a new copper paste and a preparation method thereof.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the external electrode slurry of the multilayer ceramic capacitor with high connectivity and high quality with the internal electrode and the preparation method thereof. On one hand, the invention improves the copper external electrode slurry, adjusts the slurry formula, and improves the connectivity of the sintered external electrode and the internal electrode by adding a certain amount of silver-coated nickel-copper alloy powder; on the other hand adopts the vacuum to beat and ulcerate the machine, can effectively avoid using the circumstances such as the material that gets rid of, leaks material that the three-roller mill produced through the stirring pestle stirring with the grinding effect, and the homogeneity of thick liquids is good, and the quality is higher.
Specifically, one aspect of the present invention provides a multilayer ceramic capacitor external electrode paste comprising the following components: 50-70 wt% of first metal powder, 5-20 wt% of second metal powder, 3-10 wt% of glass powder, 10-30 wt% of organic carrier and 0-2wt% of additive; the first metal powder comprises spherical copper powder and flake copper powder, and the second metal powder is silver-coated nickel-copper alloy powder.
In one or more embodiments, the first metal powder comprises from 20wt% to 30wt% spherical copper powder and from 70wt% to 80wt% flake copper powder.
In one or more embodiments, theThe average grain diameter of the first metal powder is 1 to 3 mu m, and the tap density is 4.58 to 5.50g/cm 3 The specific surface area is 1.03 to 1.51cm 2 /g。
In one or more embodiments, the spherical copper powder has an average particle size of 1 to 1.9 μm, and the flake copper powder has an average particle size of 1.5 to 3 μm.
In one or more embodiments, the second metal powder contains 20wt% to 30wt% silver, 25wt% to 35wt% nickel, and 40wt% to 50wt% copper.
In one or more embodiments, the average particle diameter of the second metal powder is 0.50 to 1.22 μm, and the tap density is 4.30 to 6.65g/cm 3 The specific surface area is 2.40 to 3.52cm 2 /g。
In one or more embodiments, the raw materials of the glass frit include 35wt% to 55wt% MnO 2 25-40 wt% of B 2 O 3 10 to 30wt% of SiO 2 5 to 20 weight percent of K 2 O, 5-15 wt% of Al 2 O 3 And 1wt% -10 wt% of Li 2 O。
In one or more embodiments, the glass powder has an average particle size of 1.6 to 2 μm and a softening point of 550 to 600 ℃.
In one or more embodiments, the organic carrier includes a resin and an organic solvent, and the mass fraction of the resin in the organic carrier is 10% to 30%, and the mass fraction of the organic solvent in the organic carrier is 70% to 90%.
In one or more embodiments, the resin has a number average molecular weight of 100000 to 800000.
In one or more embodiments, the resin is selected from one or more of acrylic, ethylcellulose, epoxy, vinyl, and phenolic resins.
In one or more embodiments, the organic solvent is selected from one or more of terpineol, hydrogenated terpineol, dihydroxy terephthalic acid, methyl acetate, propylene oxide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, cyclohexanone, and toluene cyclohexanone.
Another aspect of the present invention provides a method for preparing a multilayer ceramic capacitor external electrode paste, including the step of vacuum grinding a mixture of components of the multilayer ceramic capacitor external electrode paste using a vacuum agitator mill.
In one or more embodiments, the method produces a multilayer ceramic capacitor external electrode paste as described in any of the embodiments herein.
Another aspect of the present invention provides a multilayer ceramic capacitor having external electrodes prepared from the external electrode paste for a multilayer ceramic capacitor according to any one of the embodiments or prepared by the method according to any one of the embodiments.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) cross-sectional view of an MLCC prepared by sintering the external electrode paste of example 2 at 780 ℃.
FIG. 2 is a Scanning Electron Microscope (SEM) cross-sectional view of an MLCC prepared after the external electrode paste of comparative example 1 was sintered at 780 ℃.
Detailed Description
To make the features and effects of the present invention comprehensible to those skilled in the art, general description and definitions are made below with reference to terms and expressions mentioned in the specification and claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The theory or mechanism described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
The terms "comprising," "including," "containing," and the like, herein, encompass the meanings of "consisting essentially of 8230 \8230%, \8230composition" and "consisting of 8230 \823030composition," for example, when "a comprises B and C" is disclosed herein, "a consists essentially of B and C" and "a consists of B and C" should be considered to have been disclosed herein.
All features defined herein as numerical ranges or percentage ranges, such as values, amounts, levels and concentrations, are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to cover and specifically disclose all possible subranges and individual numerical values (including integers and fractions) within the range.
Herein, unless otherwise specified, percentages refer to mass percentages and ratios to mass ratios.
As used herein, the sum of the percentages of the components of the composition is 100%.
Herein, when embodiments or examples are described, it is understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.
In the present context, for the sake of brevity, all possible combinations of various features in various embodiments or examples are not described. Therefore, the respective features in the respective embodiments or examples may be arbitrarily combined as long as there is no contradiction between the combinations of the features, and all the possible combinations should be considered as the scope of the present specification.
The external electrode paste for the multilayer ceramic capacitor comprises or consists of first metal powder, second metal powder, glass powder, an organic carrier and an additive.
First metal powder
In the present invention, the first metal powder is copper powder, and preferably a mixture of spherical copper powder and flake copper powder. Preferably, the first metal powder comprises from 20% to 30% by weight, such as 25 + -2% by weight, of spherical copper powder and from 70% to 80% by weight, such as 75 + -2% by weight, of flake copper powder.
The average particle diameter of the entire first metal powder is preferably 1 to 3 μm, for example, 1.5 μm, 1.8 μm, 2.1 μm, 2.3 μm, 2.5 μm, and the tap density is preferably 4.58 to 5.50g/cm 3 E.g. 4.70g/cm 3 、4.80g/cm 3 、4.90g/cm 3 、5.00g/cm 3 、5.30g/cm 3 The specific surface area is preferably 1.03 to 1.51cm 2 In g, e.g. 1.20cm 2 /g、1.30cm 2 /g、1.40cm 2 /g、1.48cm 2 /g、1.50cm 2 /g。
In the embodiment where the first metal powder comprises spherical copper powder and flake copper powder, the average particle diameter of the spherical copper powder is preferably 1 to 1.9. Mu.m, for example, 1.2. Mu.m, 1.5. Mu.m, 1.6. Mu.m, 1.8. Mu.m, and the average particle diameter of the flake copper powder is preferably 1.5 to 3. Mu.m, for example, 1.8. Mu.m, 2. Mu.m, 2.2. Mu.m, 2.4. Mu.m, 2.6. Mu.m.
In the external electrode paste for a multilayer ceramic capacitor according to the present invention, the content of the first metal powder may be 50wt% to 70wt%, for example, 55wt%, 60wt%, 65wt%, 68wt%.
Second metal powder
In the invention, the second metal powder is silver-coated nickel-copper alloy powder, namely nickel-copper alloy powder coated with silver on the surface. The average particle diameter of the second metal powder is preferably 0.50 to 1.22. Mu.m, for example, 0.6. Mu.m, 0.8. Mu.m, 1. Mu.m, 1.2. Mu.m, and the tap density is preferably 4.30 to 6.65g/cm 3 E.g. 4.5g/cm 3 、5g/cm 3 、5.5g/cm 3 、6g/cm 3 The specific surface area is preferably 2.40 to 3.52cm 2 In g, e.g. 2.6cm 2 /g、2.8cm 2 /g、2.9cm 2 /g、3cm 2 /g、3.2cm 2 (ii) in terms of/g. The particle size, tap density and specific surface area of the second metal powder are controlled within the ranges, so that the effects of enhancing the slurry connecting force and improving the electrical property are exerted. The second metal powder preferably contains 20wt% to 30wt% of silver, 25wt% to 35wt% of nickel and 40wt% to 50wt% of copper, for example, the second metal powder may contain 25wt% of silver, 30wt% of nickel and 45wt% of copper. The metal content ratio of the second metal powder is controlled within the range, so that the effects of enhancing the slurry connecting force and improving the electrical property are exerted.
The invention provides application of the second metal powder in preparing external electrode paste of a multilayer ceramic capacitor or external electrodes of the multilayer ceramic capacitor, and application of the second metal powder in improving the connecting force and/or the electrical property of the external electrode paste of the multilayer ceramic capacitor or the external electrodes of the multilayer ceramic capacitor. The present invention also provides a method of preparing a multilayer ceramic capacitor external electrode paste or a multilayer ceramic capacitor external electrode having improved connection force and/or electrical properties. The application and the method comprise adding the second metal powder into the external electrode slurry of the multilayer ceramic capacitor, and further can comprise preparing the external electrode slurry of the multilayer ceramic capacitor added with the second metal powder into the external electrode of the multilayer ceramic capacitor.
The silver-coated nickel-copper alloy powder suitable for the present invention can be obtained by coating silver on the surface of copper-nickel alloy powder. The silver-coated nickel-copper alloy powder can be prepared by the following method:
(1) Preparing a copper-nickel alloy powder suspension: adding copper-nickel alloy powder into an alkaline solution for ultrasonic treatment, and dispersing the copper-nickel alloy powder into water after washing to obtain a suspension of the copper-nickel alloy powder;
(2) Silver plating on the surface of the copper-nickel alloy powder: and (2) dripping polyvinylpyrrolidone solution into the copper-nickel alloy powder suspension obtained in the step (1) under stirring, controlling the temperature to react for 15 to 30min at 25-30 ℃, dripping silver ammonia solution and glucose solution under stirring, controlling the temperature to react for 40-50 min at 25-30 ℃, raising the reaction temperature to 60-70 ℃, and reacting for 60-120 min to obtain the silver-coated nickel-copper alloy powder.
In step (1), the time of the ultrasonic treatment may be 10 to 60min, for example, 20 to 40min, 30min. The purpose of ultrasonic treatment is to remove oxides on the surface of the nickel-copper alloy powder. The lye may be NaOH solutions having a concentration of 0.2 to 0.5g/L, for example 0.3 g/L. The solid content of the prepared copper-nickel alloy powder suspension can be 20-40 g/L, such as 25g/L, 30g/L and 35g/L.
In the step (2), the concentration of the polyvinylpyrrolidone solution can be 1-3 g/L, for example 2g/L, and the dosage can be 5-10 vol% of the volume of the copper-nickel alloy powder suspension. The concentration of the silver ammonia solution can be 25-30 g/L, such as 26g/L, 27g/L, 28g/L and 29g/L, and the dosage can be 4-60 vol% of the volume of the copper-nickel alloy powder suspension. The concentration of the glucose solution can be 22-29 g/L, such as 23g/L, 25g/L and 27g/L, and the dosage can be 4-60 vol% of the volume of the copper-nickel alloy powder suspension. In the step (2), the stirring may be mechanical stirring, or may be accompanied by ultrasonic stirring.
In the external electrode paste for a multilayer ceramic capacitor according to the present invention, the content of the second metal powder may be 5wt% to 20wt%, for example, 10wt%, 14wt%, 15wt%, 17wt%.
Glass powder
The glass powder suitable for the invention is preferably Mn-B-Si glass powder, i.e. the raw material is mainly MnO 2 、B 2 O 3 And SiO 2 The glass frit of (2). In some embodiments, the raw material of the glass frit comprises MnO 2 、B 2 O 3 、SiO 2 、K 2 O、Al 2 O 3 And Li 2 O, or consist of the above components; wherein, mnO 2 Can be present in an amount of 35 wt.% to 55 wt.%, e.g., 40 wt.%, 42 wt.%, 45 wt.%, 50 wt.%, B 2 O 3 Can be present in an amount of 25 wt.% to 40 wt.%, e.g., 26 wt.%, 30 wt.%, 35 wt.%, siO 2 Can be present in an amount of 10 wt.% to 30 wt.%, e.g., 11 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, K 2 The content of O may be 5wt% to 20wt%, e.g. 8wt%, 10wt%, 15wt%, al 2 O 3 Can be present in an amount of 5wt% to 15wt%, e.g., 10wt%, li 2 The content of O can be 1wt% to 10wt%, e.g., 3wt%, 5wt%. The glass powder is obtained by mixing the raw materials of the glass powder in proportion, and then smelting, quenching, drying and refining. The glass powder preferably has an average particle diameter of 1.6 to 2 μm, for example, 1.7 μm, 1.8 μm, 1.9 μm, and a softening point of 550 to 600 ℃, for example, 560 ℃, 570 ℃, 580 ℃, 590 ℃.
In the external electrode paste for the multilayer ceramic capacitor of the present invention, the content of the glass frit may be 3wt% to 10wt%, for example, 4wt%, 5wt%, 6wt%, 8wt%.
Organic vehicle
In the present invention, the organic vehicle includes a resin and an organic solvent. The resin in the organic vehicle may be one or more selected from acrylic resin, ethyl cellulose, epoxy resin, vinyl resin, phenolic resin. The number average molecular weight of the resin is preferably 100000 to 800000, for example 200000, 400000, 450000, 500000, 600000. In some embodiments, the resin is an acrylic resin having a number average molecular weight of 400000 to 450000, e.g., 420000. The organic solvent may be one or more selected from terpineol, hydrogenated terpineol, dihydroxy terephthalic acid, methyl acetate, propylene oxide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, cyclohexanone and toluene cyclohexanone. In some embodiments, the organic solvent is hydrogenated terpineol and methyl acetate in a mass ratio of 2 to 4, e.g., 3. The mass fraction of the resin in the organic carrier may be 10% to 30%, for example 20%, and the mass fraction of the organic solvent in the carrier may be 70% to 90%, for example 80%. Stirring the resin and the organic solvent at 50-70 ℃ for 3-4 h to obtain the organic carrier after the resin is completely dissolved.
In the external electrode paste for a multilayer ceramic capacitor according to the present invention, the content of the organic vehicle may be 10wt% to 30wt%, for example, 15wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%.
Additive agent
In the present invention, the additive is optionally or preferably added. The additive suitable for use in the present invention may be various additives known to be useful for external electrode pastes for multilayer ceramic capacitors. The additives may include thixotropic agents and/or dispersing agents. Examples of thixotropic agents include LBCB-1 thixotropic lubricants, organobentonites, asbestos, kaolin, hydrogenated castor oil, triethylhexylphosphoric acid, and the like. Examples of dispersants include fatty acid polyglycol esters, sodium tripolyphosphate, sodium hexametaphosphate, oleic acid acyl, stearic acid monoglyceride, oleic acid, and the like. In some embodiments, the additive comprises an organobentonite and a fatty acid polyglycol ester.
In the external electrode paste for a multilayer ceramic capacitor of the present invention, the content of the additive may be 0 to 2wt%, for example, 0.5wt%, 0.6wt%, 1wt%, 1.3wt%, 1.5wt%. The amounts of the various additives may be conventional. In embodiments where the additive comprises an organobentonite and a fatty acid polyglycol ester, the mass ratio of the organobentonite to the aliphatic polyglycol ester may be from 1 to 1, for example 2.
External electrode paste for multilayer ceramic capacitor
Generally, the components of the electrode paste are mixed uniformly and then rolled into the electrode paste by a three-high mill. The invention discovers that the dispersibility of the slurry can be effectively improved by using the vacuum stirring and grinding machine to carry out vacuum grinding on the mixed material, thereby improving the electrical property. The invention therefore provides a method for preparing electrode paste, in particular external electrode paste for a multilayer ceramic capacitor, and application of a vacuum stirring and kneading machine in preparing electrode paste, in particular external electrode paste for a multilayer ceramic capacitor. The method and application comprise the step of carrying out vacuum grinding on the mixture of the components of the external electrode slurry of the multilayer ceramic capacitor by using a vacuum stirring and grinding machine.
In some embodiments, the external electrode paste for a multilayer ceramic capacitor of the present invention may be prepared using a method comprising the steps of:
(1) Preparing materials: uniformly mixing all components of the external electrode slurry of the multilayer ceramic capacitor according to the formula proportion; preferably, sequentially adding the first metal powder, the second metal powder, the additive, the glass powder and the organic carrier, and stirring in a stirrer for 10 to 30min in vacuum so that the materials are uniformly stirred without obvious agglomeration;
(2) Mixing and grinding: putting the material obtained in the step (1) into a vacuum stirring and grinding machine for vacuum grinding; preferably, grinding for 1 to 3h in vacuum until the fineness is below 8 mu m;
(3) And (3) filtering: filtering the slurry to obtain external electrode slurry of the multilayer ceramic capacitor; preferably, a 350-mesh filter screen is used for carrying out vacuum filtration on the slurry ground by the mill.
Multilayer ceramic capacitor
And coating the external electrode slurry of the multilayer ceramic capacitor on two ends of a ceramic chip of the multilayer ceramic capacitor, and sintering to form the external electrode of the multilayer ceramic capacitor, thus obtaining the multilayer ceramic capacitor. The sintering temperature can be 750 to 800 ℃, and the sintering time can be 60 to 90 minutes. The present invention includes a multilayer ceramic capacitor external electrode made using the multilayer ceramic capacitor external electrode paste of the present invention and a multilayer ceramic capacitor including the external electrode.
The invention has the following advantages:
(1) According to the invention, the submicron silver-coated nickel-copper alloy powder is used, during the sintering process, the silver in the external electrode is firstly melted and then the wetting effect of the glass is combined, so that the melting of the internal nickel-copper alloy can be effectively accelerated, the nickel-copper alloy in the external electrode slurry can form a bridging effect with the nickel electrode in the multilayer ceramic capacitor, and good connection is achieved, thereby improving the connectivity after sintering.
(2) According to the invention, the vacuum grinding machine is adopted, and the slurry is not contacted with the external environment through the vacuum stirring and grinding effects of the stirring pestle, so that the throwing and leaking of the viscoelastic slurry can be effectively avoided, the dispersibility of the slurry is effectively improved, the surface roughness is obviously reduced, and the quality of the slurry is improved.
(3) The external electrode made of the external electrode slurry of the multilayer ceramic capacitor has improved electrical property, and is obviously improved in one or more performance indexes of capacitance value, loss and withstand voltage.
The present invention will be illustrated below by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the present invention. Instrumentation conventional in the art is used in the following examples. The following examples are conducted under conventional conditions or conditions recommended by the manufacturers, unless otherwise specified. The various starting materials used in the following examples, unless otherwise specified, were conventional commercially available products, the specifications of which are conventional in the art.
The first metal powder used in examples and comparative examples was a mixture of 25% by weight of spherical copper powder and 75% by weight of flake copper powder, and had an average particle diameter of 2.1 μm and a tap density of 4.81g/cm 3 Specific surface area of 1.48cm 2 (iv) g; wherein the average grain diameter of the spherical copper powder is 1.89 mu m, and the average grain diameter of the flake copper powder is 2.22 mu m.
The second metal powder used in the examples and comparative examples was silver-coated nickel-copper alloy powder prepared by the method comprising:
1. preparing a copper-nickel alloy powder suspension: adding 19.05g of copper-nickel alloy powder (2 of the mass ratio of nickel to copper and 3 of 2) with the average particle size of 1.01 mu m into 500ml of NaOH solution with the concentration of 0.3g/L, carrying out ultrasonic treatment for 30min, washing for 3 times by using deionized water, and adding 800ml of deionized water to obtain a suspension of the copper-nickel alloy powder;
2. silver plating on the surface of the copper-nickel alloy powder: dripping 50ml of polyvinylpyrrolidone solution with the concentration of 2g/L into the copper-nickel alloy powder suspension obtained in the step 1 under the conditions of ultrasonic stirring and mechanical stirring, controlling the temperature to react for 20min at 25 ℃, simultaneously dripping 400ml of silver-ammonia solution with the concentration of 25g/L and 400ml of glucose solution with the concentration of 22.8g/L into the copper-nickel alloy powder suspension under the conditions of ultrasonic stirring and mechanical stirring, controlling the temperature to react for 50min at 25 ℃, raising the reaction temperature to 60 ℃ and reacting for 120min, washing, filtering and drying the obtained coating powder to obtain the silver-coated nickel-copper alloy powder, wherein the silver content is 25wt%, the average particle size is 1.18 mu m, and the tap density is 5.01g/cm 3 Specific surface area of 2.88cm 2 /g。
The raw material compositions of the glass powder used in the examples and comparative examples were: mnO 2 42wt%、B 2 O 3 26wt%、SiO 2 11wt%、K 2 O 8wt%、Al 2 O 3 10wt%、Li 2 O3 wt%. The glass powder had an average particle diameter of 1.81 μm and a softening point of 570 ℃.
The organic vehicle used in the examples and comparative examples was prepared by mixing 20wt% of an acrylic resin having a number average molecular weight of 420000, 60wt% of hydrogenated terpineol, and 20wt% of methyl acetate, and was prepared by the following process: the resin and the organic solvent are stirred for 3.5h at 65 ℃, and the organic carrier is obtained after the resin is completely dissolved.
The additives used in examples and comparative examples were prepared by mixing 40wt% of organobentonite and 60wt% of fatty acid polyethylene glycol ester at room temperature with stirring.
The formulations and process parameters of the slurries of the examples and comparative examples are shown in table 1.
Table 1: formulation proportions and Process parameters of examples and comparative examples
Example 1
This example provides an external electrode paste for a multilayer ceramic capacitor, which is prepared as follows:
1. preparing materials: according to the formula proportion shown in table 1, 68wt% of first metal powder, 5wt% of second metal powder, 0.6wt% of additive, 4wt% of glass powder and 22.4wt% of organic carrier are sequentially added into a batching barrel; stirring for 10min in vacuum by using a stirrer to ensure that the materials are uniformly stirred without obvious agglomeration;
2. mixing and grinding: putting the material obtained in the step 1 into a vacuum stirring mill, and grinding for 1 hour in vacuum, wherein the fineness is below 8 mu m;
3. and (3) filtering: and carrying out vacuum filtration on the slurry ground by the grinder by using a 350-mesh filter screen to obtain the multilayer ceramic capacitor external electrode slurry with high connectivity and high quality of the internal electrode and the solid content of 77 wt%.
Example 2
This example provides an external electrode paste for a multilayer ceramic capacitor, which is prepared as follows:
1. preparing materials: according to the formula proportion shown in table 1, 60wt% of first metal powder, 10wt% of second metal powder, 1.3wt% of additive, 6wt% of glass powder and 22.7wt% of organic carrier are sequentially added into a dosing barrel; stirring for 15min in vacuum by using a stirrer to ensure that the materials are stirred uniformly without obvious agglomeration;
2. mixing and grinding: putting the material obtained in the step 1 into a vacuum stirring and grinding machine, and grinding for 1.5h in vacuum, wherein the fineness is below 8 mu m;
3. and (3) filtering: and carrying out vacuum filtration on the slurry ground by the grinder by using a 350-mesh filter screen to obtain the multilayer ceramic capacitor external electrode slurry with high connectivity and high quality of the internal electrode and the solid content of 76 wt%.
Example 3
This example provides an external electrode paste for a multilayer ceramic capacitor, which is prepared as follows:
1. preparing materials: according to the formula proportion shown in Table 1, 55wt% of first metal powder, 14wt% of second metal powder, 1.5wt% of additive, 8wt% of glass powder and 21.5wt% of organic carrier are sequentially added into a batching barrel; stirring in vacuum for 20min with a stirrer to make the materials uniformly stirred without obvious agglomeration;
2. mixing and grinding: putting the material obtained in the step 1 into a vacuum stirring mill, and carrying out vacuum grinding for 2 hours until the fineness is below 8 mu m;
3. and (3) filtering: and (3) carrying out vacuum filtration on the slurry ground by the grinder by using a 350-mesh filter screen to obtain the multilayer ceramic capacitor external electrode slurry with high connectivity and high quality of the internal electrode and the solid content of 77 wt%.
Example 4
This example provides an external electrode paste for a multilayer ceramic capacitor, which is prepared as follows:
1. preparing materials: according to the formula proportion shown in table 1, 50wt% of first metal powder, 17wt% of second metal powder, 2wt% of additive, 10wt% of glass powder and 21wt% of organic carrier are sequentially added into a batching barrel; stirring in vacuum for 30min by using a stirrer to ensure that the materials are stirred uniformly without obvious agglomeration;
2. mixing and grinding: putting the material obtained in the step 1 into a vacuum stirring and grinding machine, and grinding for 2.5 hours in vacuum, wherein the fineness is below 8 mu m;
3. and (3) filtering: and (3) carrying out vacuum filtration on the slurry ground by the grinder by using a 350-mesh filter screen to obtain the multilayer ceramic capacitor external electrode slurry with high connectivity and high quality of the internal electrode and the solid content of 77 wt%.
Comparative example 1
The present comparative example provides an external electrode paste for a multilayer ceramic capacitor, which was prepared as follows:
1. preparing materials: according to the formula proportion shown in table 1, 70wt% of first metal powder, 0wt% of second metal powder, 1.3wt% of additive, 6wt% of glass powder and 22.7wt% of organic carrier are sequentially added into a batching barrel; stirring for 15min in vacuum by using a stirrer to ensure that the materials are stirred uniformly without obvious agglomeration;
2. mixing and grinding: putting the material obtained in the step 1 into a vacuum stirring mill, and carrying out vacuum grinding for 1.5h, wherein the fineness is below 8 mu m;
3. and (3) filtering: and carrying out vacuum filtration on the slurry ground by the grinder by using a 350-mesh filter screen to obtain the multilayer ceramic capacitor external electrode slurry with the solid content of 76 wt%.
Comparative example 2
The present comparative example provides an external electrode paste for a multilayer ceramic capacitor, which was prepared as follows:
1. preparing materials: according to the formula proportion shown in Table 1, 55wt% of first metal powder, 14wt% of second metal powder, 1.5wt% of additive, 8wt% of glass powder and 21.5wt% of organic carrier are sequentially added into a batching barrel; stirring in vacuum for 20min with a stirrer to make the materials uniformly stirred without obvious agglomeration;
2. mixing and grinding: rolling and grinding the material obtained in the step 1 for 10 times by a three-roll mill, wherein the fineness is below 8 mu m;
3. and (3) filtering: and (3) carrying out vacuum filtration on the slurry ground by a three-high mill by using a 350-mesh filter screen to obtain the external electrode slurry of the multilayer ceramic capacitor with the solid content of 77 wt%.
Comparative example 3
The present comparative example provides an external electrode paste for a multilayer ceramic capacitor, which was prepared as follows:
1. preparing materials: according to the formula proportion shown in table 1, 70wt% of first metal powder, 0wt% of second metal powder, 1.3wt% of additive, 6wt% of glass powder and 22.7wt% of organic carrier are sequentially added into a batching barrel; stirring for 15min in vacuum by using a stirrer to ensure that the materials are uniformly stirred without obvious agglomeration;
2. mixing and grinding: rolling and grinding the material obtained in the step 1 for 10 times by a three-roll mill, wherein the fineness is below 8 mu m;
3. and (3) filtering: and carrying out vacuum filtration on the slurry ground by a three-high mill by using a 350-mesh filter screen to obtain the multilayer ceramic capacitor external electrode slurry with the solid content of 76 wt%.
Test example
MLCCs of specification 0603X104K250NBH were made using the external electrode pastes of examples 1-4 and comparative examples 1-3, in which the external electrode pastes were sintered at 780 ℃ for 70 minutes.
Fig. 1 and 2 are SEM pictures of MLCCs prepared using the external electrode pastes of example 2 and comparative example 1, respectively, and it can be known that comparative example 1 paste without the second metal powder has more holes inside the external electrode after 780 ℃ sintering and a break point in connectivity of the internal and external electrodes (fig. 2); in the case of the slurry of example 2 to which the second metal powder was added, no break point was observed under the same sintering conditions, and the inner and outer electrodes were tightly connected (fig. 1).
MLCCs made using the external electrode pastes of examples 1-4 and comparative examples 1-3 were subjected to capacitance, loss, withstand voltage and insulation resistance tests by: by adopting a four-parameter testing machine, the capacitance value, the loss, the withstand voltage and the insulation resistance of the MLCC can be tested at the same time, the test voltage is 1V, and the frequency is 1kHz. The results are shown in Table 2, wherein the capacitance, loss and breakdown voltage are the average values of 500 MLCC finished capacitors, and the withstand voltage is the range value of 500 MLCC finished capacitors.
The MLCC capacitor for 0603X104K250NBH has electrical performance requirements of: the allowable range of the capacitance value is 90 to 110 mu F, the loss DF is less than or equal to 3.5 percent, the withstand voltage BV is more than or equal to 62.5V, and the insulation resistance IR multiplied by C is more than or equal to 100s.
Table 2: electrical Properties of MLCCs corresponding to examples 1-4 and comparative examples 1-3
The MLCC terminals produced from the external electrode pastes of examples 1-4 and comparative examples 1-3 were subjected to strength tests, and the results are shown in Table 3. The test method comprises the following steps: and after the MLCC terminal is sealed and sintered, plating nickel and plating tin to obtain an MLCC finished product, welding a lead at one end of an external electrode by using soldering tin, vertically fixing a welded and molded sample on a tensile testing machine, testing and recording the tensile force.
Table 3: results of MLCC terminal Strength test for examples 1 to 4 and comparative examples 1 to 3
The external electrode pastes of examples 1 to 4 and comparative examples 1 to 3 were coated on a glass slide to a coating thickness of 50 d, dried at 150 c for 10min, and the surface roughness of the dried paste was measured, with the results shown in table 4.
Table 4: examples 1 to 4 and comparative examples 1 to 3 external electrode paste surface roughness test results
As can be seen from comparing the electrical properties of the MLCCs obtained in example 3 and comparative example 2 in table 2, the slurry obtained after dispersion grinding using a vacuum mill (example 3) has a higher capacitance value, lower loss and higher withstand voltage than when a three-roll mill (comparative example 2) is used. As can be seen by comparing the electrical properties of MLCCs corresponding to comparative example 1 and comparative example 3 in table 2, the slurry prepared using the mill (comparative example 1) has better electrical properties than those prepared using a conventional three-roll mill (comparative example 3). As can be seen by comparing the electrical properties of MLCCs corresponding to example 2 and comparative example 1 in table 2, the addition of the second metal powder (example 2) can improve the electrical properties of the paste.
As can be seen from the results of the tab strength test in table 3, the tab strength of the MLCCs corresponding to examples 1 to 4 and comparative example 2 to which the second metal powder was added was higher than those of comparative examples 1 and 3 to which the second metal powder was not added; as can be seen from a comparison of the results of example 3 and comparative example 2, and comparative example 1 and comparative example 3 in table 3, respectively, the use of the kneader to prepare the slurry enables the improvement of the terminal strength.
As can be seen from the test results of the surface roughness in table 4, the slurries of examples 1 to 4 and comparative example 1 using the kneader dispersion process had a significantly better surface roughness after drying than comparative example 2 and comparative example 3 using the conventional roll process.
In conclusion, in the preparation process of the external electrode slurry, the second metal powder is added to improve the bonding strength of the slurry after sintering, the slurry dispersibility can be improved by using the preparation process of the mill, and the capacitance value, the loss and the voltage resistance can be improved and the strength of the leading-out terminal can be improved by adding the second metal powder and adopting the dispersion process of the vacuum mill.
Claims (10)
1. An external electrode paste for a multilayer ceramic capacitor, comprising the following components: 50-70 wt% of first metal powder, 10-15 wt% of second metal powder, 3-10 wt% of glass powder, 10-30 wt% of organic carrier and 0-2wt% of additive; the first metal powder comprises spherical copper powder and flake copper powder, and the second metal powder is silver-coated nickel-copper alloy powder; the external electrode paste for the multilayer ceramic capacitor is prepared by vacuum grinding a mixture of the components of the external electrode paste for the multilayer ceramic capacitor.
2. The external electrode paste for multilayer ceramic capacitors as claimed in claim 1, wherein said first metal powder comprises 20 to 30wt% of spherical copper powder and 70 to 80wt% of flake copper powder.
3. The external electrode paste for multilayer ceramic capacitors as claimed in claim 1,
the average grain diameter of the first metal powder is 1 to 3 mu m, and the tap density is 4.58 to 5.50g/cm 3 The specific surface area is 1.03 to 1.51cm 2 (ii)/g; and/or
The average grain diameter of the spherical copper powder is 1 to 1.9 mu m, and the average grain diameter of the flaky copper powder is 1.5 to 3 mu m.
4. The external electrode paste for multilayer ceramic capacitors as claimed in claim 1, wherein said second metal powder contains 20-30 wt% silver, 25-35 wt% nickel and 40-50 wt% copper.
5. The external electrode paste for multilayer ceramic capacitors as claimed in claim 1, wherein the average particle diameter of the second metal powder is 0.50 to 1.22 μm, and the tap density is 4.30 to 6.65g/cm 3 The specific surface area is 2.40 to 3.52cm 2 /g。
6. The multilayer ceramic capacitor external electrode paste according to claim 1,
the raw material of the glass powder comprises 35-55 wt% of MnO 2 25-40 wt% of B 2 O 3 10 to 30wt% of SiO 2 5 to 20 weight percent of K 2 O, 5-15 wt% of Al 2 O 3 And 1wt% -10 wt% of Li 2 O; and/or
The average grain diameter of the glass powder is 1.6 to 2 mu m, and the softening point is 550 to 600 ℃.
7. The external electrode paste for multilayer ceramic capacitors as claimed in claim 1, wherein the organic vehicle comprises a resin and an organic solvent, the resin has a number average molecular weight of 100000 to 800000, the mass fraction of the resin to the organic vehicle is 10% to 30%, and the mass fraction of the organic solvent to the organic vehicle is 70% to 90%.
8. The external electrode paste for multilayer ceramic capacitor according to claim 7,
the resin is selected from one or more of acrylic resin, ethyl cellulose, epoxy resin, vinyl resin and phenolic resin; and/or
The organic solvent is selected from one or more of terpineol, hydrogenated terpineol, dihydroxy terephthalic acid, methyl acetate, propylene oxide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, cyclohexanone and toluene cyclohexanone.
9. A method for producing the external electrode paste for a multilayer ceramic capacitor according to any one of claims 1 to 8, comprising the step of vacuum grinding a mixture of components of the external electrode paste for a multilayer ceramic capacitor using a vacuum agitator mill.
10. A multilayer ceramic capacitor, wherein the external electrode of the multilayer ceramic capacitor is prepared from the external electrode paste for a multilayer ceramic capacitor according to any one of claims 1 to 8 or the external electrode paste for a multilayer ceramic capacitor prepared by the method according to claim 9.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109689250A (en) * | 2016-08-31 | 2019-04-26 | 同和电子科技有限公司 | The coating alloy powder of silver, conductive paste, electronic component and electric device |
| CN113178327A (en) * | 2021-03-30 | 2021-07-27 | 大连海外华昇电子科技有限公司 | MLCC copper-clad nickel alloy inner electrode slurry and application thereof |
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