CN114783770A - 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 PDF

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CN114783770A
CN114783770A CN202210694692.9A CN202210694692A CN114783770A CN 114783770 A CN114783770 A CN 114783770A CN 202210694692 A CN202210694692 A CN 202210694692A CN 114783770 A CN114783770 A CN 114783770A
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external electrode
multilayer ceramic
ceramic capacitor
powder
electrode paste
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CN114783770B (en
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不公告发明人
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Xian Hongxing Electronic Paste Technology Co Ltd
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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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  • 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 MLCC inner and outer electrodes after the outer electrode slurry is sintered have good connectivity, high quality and simple production process, and can realize industrial production.

Description

External electrode slurry of multilayer ceramic capacitor and preparation method thereof
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 the number of stacked layers are different depending on the use 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 the external electrode field, copper paste is used as external electrode paste of multilayer ceramic capacitors at home and abroad in place of silver paste in order to reduce production cost, but copper powder is easily oxidized, has low sintering activity, is easily formed with sintering defects, and is often represented by poor compactness after end-capping sintering, insufficient connectivity of internal and external electrodes, and the like, thereby seriously affecting 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 external electrode slurry of a multilayer ceramic capacitor with high connectivity with an internal electrode and high quality and a 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 material, hourglass material of getting rid of that three-roller mill produced through the stirring pestle stirring and grinding action, 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 0-2 wt% 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 includes from 20wt% to 30wt% spherical copper powder and from 70wt% to 80wt% flake copper powder.
In one or more embodiments, the first metal powder has an average particle diameter of 1 to 3 μm and a tap density of 4.58 to 5.50g/cm3The specific surface area is 1.03-1.51 cm2/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 second metal powder has an average particle diameter of 0.50 to 1.22 μm and a tap density of 4.30 to 6.65g/cm3The specific surface area is 2.40-3.52 cm2/g。
In one or more embodiments, the raw materials of the glass frit include 35wt% to 55wt% MnO225 to 40wt% of B2O310 to 30wt% of SiO25 to 20wt% of K2O, 5-15 wt% of Al2O3And 1wt% -10 wt% of Li2O。
In one or more embodiments, the glass frit 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 vehicle includes a resin and an organic solvent, and the mass fraction of the resin in the organic vehicle is 10% to 30%, and the mass fraction of the organic solvent in the organic vehicle 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 an external electrode paste for a multilayer ceramic capacitor, the method 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.
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 photograph of an MLCC prepared by sintering the outer electrode paste of example 2 at 780 ℃.
FIG. 2 is a Scanning Electron Microscope (SEM) cross-sectional photograph of an MLCC prepared by sintering the outer electrode paste of comparative example 1 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 being limited by any particular theory or mechanism.
The terms "comprising," including, "" containing, "and the like, herein, encompass the meanings of" consisting essentially of … … "and" consisting of … …, "e.g., when" A comprises B and C, "A consists essentially of B and C" and "A consists of B and C" are disclosed herein, and are to be considered as having been disclosed herein.
All features defined herein as numerical ranges or percentage ranges, such as values, amounts, levels and concentrations, are provided 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 to be 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, as long as there is no contradiction between combinations of these technical features, any combinations of the technical features in the respective embodiments or examples may be made, and all possible combinations should be considered as the scope of the present specification.
The external electrode slurry of 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 20wt% to 30wt%, such as 25 ± 2wt% spherical copper powder and from 70wt% to 80wt%, such as 75 ± 2wt% flake copper powder.
The first metal powder preferably has an average particle diameter of 1 to 3 μm, for example, 1.5 μm, 1.8 μm, 2.1 μm, 2.3 μm, 2.5 μm, and a tap density of 4.58 to 5.50g/cm3E.g. 4.70g/cm3、4.80g/cm3、4.90g/cm3、5.00g/cm3、5.30g/cm3The specific surface area is preferably 1.03-1.51 cm2In g, e.g. 1.20cm2/g、1.30cm2/g、1.40cm2/g、1.48cm2/g、1.50cm2/g。
In the embodiment where the first metal powder comprises spherical copper powder and flake copper powder, the average particle size of the spherical copper powder is preferably 1 to 1.9 μm, for example, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, and the average particle size of the flake copper powder is preferably 1.5 to 3 μm, for example, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm.
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%, 68 wt%.
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 second metal powder preferably has an average particle diameter of 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 a tap density of 4.30 to 6.65g/cm3E.g. 4.5g/cm3、5g/cm3、5.5g/cm3、6g/cm3The specific surface area is preferably 2.40-3.52 cm2In g, e.g. 2.6cm2/g、2.8cm2/g、2.9cm2/g、3cm2/g、3.2cm2(ii) in terms of/g. Controlling the particle size, tap density and specific surface area of the second metal powder within the above ranges is beneficial to exerting the functions of enhancing the slurry connecting force and improving the electrical property. The second metal powder preferably contains silver, nickel and copper in a mass ratio of 20wt% to 30wt%, 25wt% to 35wt% and 40wt% to 50wt%, for example, the second metal powder may contain silver, nickel and copper in a mass ratio of 25wt%, 30wt% and 45 wt%. Controlling the metal content ratio of the second metal powder within the above range is beneficial to exerting the effects of enhancing the slurry connecting force and improving the electrical property.
The present invention provides use of the second metal powder of the present invention in preparing external electrode paste for a multilayer ceramic capacitor or external electrodes for a multilayer ceramic capacitor, and use of the second metal powder of the present invention in improving the joining force and/or electrical properties of the external electrode paste for a multilayer ceramic capacitor or external electrodes for a 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) dropwise adding a polyvinylpyrrolidone solution into the copper-nickel alloy powder suspension obtained in the step (1) under stirring, controlling the temperature to react for 15-30 min at 25-30 ℃, simultaneously dropwise adding a silver ammonia solution and a glucose solution under stirring, controlling the temperature to react for 40-50 min at 25-30 ℃, then raising the reaction temperature to 60-70 ℃, and reacting for 60-120 min to obtain the silver-coated nickel-copper alloy powder.
In the step (1), the time of the ultrasonic treatment may be 10-60 min, for example, 20-40 min, 30 min. The purpose of ultrasonic treatment is to remove oxides on the surface of the nickel-copper alloy powder. The alkali solution can be NaOH solution with the concentration of 0.2-0.5 g/L, such as 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 35 g/L.
In the step (2), the concentration of the polyvinylpyrrolidone solution may be 1 to 3g/L, for example, 2g/L, and the amount may be 5 to 10vol% 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%, 17 wt%.
Glass powder
The glass powder suitable for the invention is preferably Mn-B-Si glass powder, i.e. the raw material is mainly MnO2、B2O3And SiO2The glass frit of (2). In some embodiments, the starting material for the glass frit comprises MnO2、B2O3、SiO2、K2O、Al2O3And Li2O, or consist of the above components; wherein, MnO is2Can be present in an amount of 35wt% to 55wt%, e.g., 40wt%, 42wt%, 45wt%, 50wt%, B2O3Can be present in an amount of 25 wt.% to 40 wt.%, e.g., 26 wt.%, 30 wt.%, 35 wt.%, SiO2Can be present in an amount of 10 wt.% to 30 wt.%, e.g., 11 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, K2The content of O may be 5wt% to 20wt%, e.g. 8wt%, 10wt%, 15wt%, Al2O3Is composed ofIn an amount of 5wt% to 15wt%, e.g., 10wt%, Li2The content of O can be 1wt% to 10wt%, e.g., 3wt%, 5 wt%. 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 suitable for use in the present invention 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%, 8 wt%.
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 2:1 to 4:1, such as 3: 1. The mass fraction of the resin in the organic carrier can be 10-30%, for example 20%, and the mass fraction of the organic solvent in the carrier can be 70-90%, for example 80%. And 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%, 25 wt%.
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 according to the present invention, the content of the additive may be 0 to 2wt%, for example, 0.5wt%, 0.6wt%, 1wt%, 1.3wt%, 1.5 wt%. 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 and the fatty acid polyglycol ester may be from 1:1 to 1:2, for example 2: 3.
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 materials, so that the electrical property is improved. 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, the first metal powder, the second metal powder, the additive, the glass powder and the organic carrier are sequentially added, and the mixture is stirred for 10-30 min in vacuum by using a stirrer, 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 1-3 h 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 750-800 ℃, and the sintering time can be 60-90 minutes. The present invention includes a multilayer ceramic capacitor external electrode manufactured 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 sintering, 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, good connection is achieved, and the connectivity after sintering is improved.
(2) According to the invention, the vacuum grinding machine is adopted, the slurry is not contacted with an external environment through the vacuum stirring and grinding actions of the stirring pestle, the material 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 prepared by 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. The following examples use instrumentation conventional in the art. The following examples are conducted under conventional conditions or conditions recommended by the manufacturer, without specifying specific conditions. 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 the examples and comparative examples was a mixture of 25wt% of spherical copper powder and 75wt% of flake copper powder, and had an average particle diameter of 2.1 μm and a tap density of 4.81g/cm3Specific surface area of 1.48cm2(ii)/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 (the mass ratio of nickel to copper is 2: 3) with the average particle size of 1.01 mu m into 500ml of NaOH solution with the concentration of 0.3g/L for 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/cm3Specific surface area of 2.88cm2/g。
The raw material compositions of the glass powder used in the examples and comparative examples were: MnO2 42wt%、B2O3 26wt%、SiO211wt%、K2O 8wt%、Al2O3 10wt%、Li2And O3 wt%. The average particle diameter of the glass powder was 1.81 μm, and the softening point was 570 ℃.
The organic vehicle used in the examples and comparative examples was prepared by mixing 20wt% of acrylic resin having a number average molecular weight of 420000, 60wt% of hydrogenated terpineol, and 20wt% of methyl acetate, and was prepared by: 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 ratios and processing parameters of examples and comparative examples
Figure 990963DEST_PATH_IMAGE002
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 dosing 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 and grinding machine, and grinding for 1h 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 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 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 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 dosing barrel; stirring in vacuum for 30min 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 and grinding machine, and grinding for 2.5 hours 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%.
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 dosing 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: 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 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 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 stirred uniformly 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 slurry of example 2 in 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 1 kHz. 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 90-110 mu F, the loss DF is less than or equal to 3.5%, 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 100 s.
Table 2: electrical Properties of MLCCs corresponding to examples 1-4 and comparative examples 1-3
Figure 173683DEST_PATH_IMAGE004
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 sealed MLCC terminal is sintered, plating nickel and 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 formed sample on a tensile testing machine, testing, and recording the tensile force.
Table 3: results of MLCC terminal Strength test corresponding to examples 1 to 4 and comparative examples 1 to 3
Figure 953420DEST_PATH_IMAGE006
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, the results of which are shown in table 4.
Table 4: examples 1 to 4 and comparative examples 1 to 3 results of surface roughness test of external electrode paste
Figure 348629DEST_PATH_IMAGE008
As can be seen from comparing the electrical properties of the MLCCs of example 3 and comparative example 2 in table 2, the slurry after dispersion grinding using the vacuum mill (example 3) has a higher capacitance value, lower loss and higher withstand voltage than when using the triple roll mill (comparative example 2). 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 mill dispersion process have a significantly better surface roughness after drying than comparative example 2 and comparative example 3 using the conventional rolling 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. 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 0-2 wt% 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.
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 particle diameter of the first metal powder is 1-3 mu m, and the tap density is 4.58-5.50 g/cm3The specific surface area is 1.03-1.51 cm2(iv) g; and/or
The average particle size of the spherical copper powder is 1-1.9 μm, and the average particle size of the flake copper powder is 1.5-3 μm.
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 according to claim 1, wherein the second metal powder has an average particle diameter of 0.50 to 1.22 μm and a tap density of 4.30 to 6.65g/cm3The specific surface area is 2.40-3.52 cm2/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 MnO225-40 wt% of B2O310 to 30 weight percent of SiO25 to 20wt% of K2O, 5-15 wt% of Al2O3And 1wt% -10 wt% of Li2O; and/or
The average particle size of the glass powder is 1.6-2 mu m, and the softening point is 550-600 ℃.
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 resin accounts for 10% to 30% by mass of the organic vehicle, and the organic solvent accounts for 70% to 90% by mass of the organic vehicle.
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 mixer.
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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