CN108281215B - Silver terminal electrode slurry for low-temperature cured thermoplastic polyimide MLCC and preparation method thereof - Google Patents
Silver terminal electrode slurry for low-temperature cured thermoplastic polyimide MLCC and preparation method thereof Download PDFInfo
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- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1046—Polyimides containing oxygen in the form of ether bonds in the main chain
- C08G73/105—Polyimides containing oxygen in the form of ether bonds in the main chain with oxygen only in the diamino moiety
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1046—Polyimides containing oxygen in the form of ether bonds in the main chain
- C08G73/1053—Polyimides containing oxygen in the form of ether bonds in the main chain with oxygen only in the tetracarboxylic moiety
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- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1057—Polyimides containing other atoms than carbon, hydrogen, nitrogen or oxygen in the main chain
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
- C08G73/1071—Wholly aromatic polyimides containing oxygen in the form of ether bonds in the main chain
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- H—ELECTRICITY
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/30—Stacked capacitors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-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
Abstract
The invention discloses silver terminal electrode slurry for a low-temperature cured thermoplastic polyimide MLCC and a preparation method thereof, the prepared silver terminal electrode slurry for the low-temperature cured thermoplastic polyimide MLCC consists of conductive particles and polyamide acid resin, wherein the conductive particles and the polyamide acid resin are uniformly mixed, and the mass fraction of the conductive particles in the silver terminal electrode slurry is between 60 and 85 percent. The electrode prepared by the silver terminal electrode slurry has excellent mechanical property, the heat-resistant temperature is as high as 400 ℃, the electrode can be widely applied in a wider range, and the electrode prepared by the slurry has longer service life because the slurry does not contain a curing agent and is cured by imidization reaction.
Description
Technical Field
The invention relates to the technical field of electrodes for MLCC (multilayer ceramic capacitor), in particular to silver end electrode slurry for low-temperature curing thermoplastic polyimide MLCC and a preparation method thereof.
Background
In recent years, in chip-type electronic components such as multilayer ceramic dielectric capacitors MLCCs, resin electrodes formed by applying and sintering a metal-containing resin terminal electrode paste have been widely used as external electrodes. The existing external electrode forming methods are generally divided into two types:
one type is a high-temperature sintering type, the forming process of the slurry needs low-temperature drying to remove a solvent in the slurry, resin components in an electrode are removed through a high-temperature sintering furnace, then a metal sintering process is carried out at the temperature of 600-850 ℃, so that metal powder and glass powder form a compact electrode layer, the resin usually adopts ethyl cellulose, alkyd resin, acrylic resin, phenolic resin and the like, and the metal content is generally 60-80 wt.%;
the other type is low-temperature curing type, the surface of a sintered silver electrode is coated with a layer of the paste, the forming process only needs to be carried out by drying at low temperature to remove the solvent in the paste, then the electrode is formed by curing reaction at about 200 ℃, the resin usually adopts epoxy resin, polyurethane resin, phenolic aldehyde modified epoxy resin and the like, and amine, triazole, imidazole and the like are also added as curing agents, and the silver content is generally high.
The substrate of the multilayer ceramic dielectric capacitor is generally made of one type of ceramic and two types of ceramic, wherein the two types of ceramic have larger dielectric constants, so that the two types of ceramic are generally selected as the substrate to meet the development trend of the multilayer ceramic dielectric capacitor with small volume and large capacity, but the two types of ceramic have the unique defects that the strength of a ceramic body is lower, and the ceramic body cracks can be caused under the stress action, so that the capacitor is short-circuited and fails. Therefore, in order to overcome the defects, a low-temperature curing silver terminal electrode paste is usually selected, and an electrode layer formed by the paste is also provided with resin, which is equivalent to an elastic layer, so that the external stress can be absorbed more effectively, the capacitor is protected, and the capacitor is still not damaged under the bending deformation of the PCB caused by the influence of the manufacturing process and the external environment (such as vibration, temperature change and the like). Therefore, the condition of short circuit is avoided to a great extent, and the capacitor using the paste is more suitable for the environment with higher requirements on reliability in the field of military industry, automobiles, power supply lines and the like.
However, this type of slurry also has some disadvantages, one being: the use temperature of the epoxy resin generally selected by the existing slurry does not exceed 200 ℃, but in the high-temperature welding process of wave soldering, reflow soldering and the like, in order to reach the melting temperature of the solder, the welding temperature is usually over 230 ℃, so a small part of resin can be heated and decomposed in the welding process, and the delamination phenomenon is generated between the electrode layers of the product, so that the product fails, and the epoxy resin is brittle after being cured and has poor toughness; secondly, the following steps: the existing curing resin slurry is usually added with a curing agent, and the resin and the curing agent coexist for a long time to cause the deterioration of the resin, so that the service cycle of an electrode made of the existing curing resin slurry is short, and generally does not exceed 6 months.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the silver terminal electrode slurry for the low-temperature cured thermoplastic polyimide MLCC, which comprises conductive particles and polyamide acid resin, wherein the conductive particles and the polyamide acid resin are uniformly mixed, and the mass fraction of the conductive particles in the silver terminal electrode slurry is 60-85%.
Optionally, the conductive particles are one or a combination of spherical particles and plate-shaped particles.
Optionally, the mass ratio of the spherical particles to the flaky particles in the conductive particles is 0-5: 1.
Optionally, the spherical particles have a particle size in the range of 0.5um to 5um, and the platelet particles have a particle size in the range of 0.5um to 10 um.
Correspondingly, the invention also provides a preparation method of the silver terminal electrode slurry for the low-temperature cured thermoplastic polyimide MLCC, which comprises the following steps:
adding conductive particles into an organic solvent, adding a coupling agent into the organic solvent, performing ultrasonic dispersion, and filtering to obtain pretreated conductive particles, wherein the addition amount of the coupling agent is 0.5-5% of the mass of the conductive particles;
obtaining polyamic acid resin through polymerization of diamine and dianhydride, wherein the viscosity of the polyamic acid resin is 10000-40000 mPa.s;
adding the pretreated conductive particles into the polyamic acid resin, and then stirring in a reaction kettle to uniformly disperse the pretreated conductive particles in the polyamic acid resin to obtain a mixture of the pretreated conductive particles and the polyamic acid resin;
pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the mixture;
rolling the defoamed mixture by a grinder to obtain slurry with the fineness of below 10 um;
and filtering the slurry through filter cloth, and canning and storing the filtered slurry.
Alternatively, the step of obtaining a polyamic acid resin by polymerization of a diamine and a dianhydride comprises:
placing dianhydride and diamine in a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa for 4 hours, and drying;
dissolving dried diamine in a solvent, and adding dried dianhydride into the solvent to react for 5 hours after the diamine is completely dissolved to obtain a polyamic acid resin solution; the mass fraction of the polyamic acid resin in the solution is between 3% and 18%;
adding a plasticizer into the solution to obtain polyamic acid resin with the viscosity of 10000-40000 mPa.s; the addition amount of the plasticizer is 5-30% of the mass of the polyamic acid resin.
Optionally, the mesh number of the filter cloth in the step of filtering the slurry through the filter cloth and then canning and storing is 500 meshes.
Optionally, the stirring time in the step of uniformly dispersing the pretreated conductive particles in the polyamic acid resin in the reaction kettle is 4-6 hours.
Optionally, the dianhydride is one of pyromellitic dianhydride, 4-oxydiphthalic anhydride, and trimellitic anhydride chloride; the diamine is one of 4, 4-diaminodiphenyl ether, 4-diaminodiphenylmethane, p-phenylenediamine, 2 '-dimethyl-4, 4' -diaminobiphenyl, 1, 4-bis (4-aminophenoxy) benzene and 1, 3-bis (4-aminophenoxy) benzene; the plasticizer is dimethyl phthalate.
Optionally, the organic solvent is one of N, N-dimethylformamide, N-dimethylacetamide and N-methylpyrrolidone; the coupling agent is a titanate coupling agent or a silane coupling agent.
The silver terminal electrode slurry for the low-temperature cured thermoplastic polyimide MLCC is prepared by directly mixing the conductive particles and the polyamic acid resin, and the preparation method is simple and convenient. In addition, the electrode prepared by the silver terminal electrode slurry has excellent mechanical property, and the heat-resistant temperature can reach 250-400 ℃, so the electrode can be widely applied in a wider range.
Drawings
FIG. 1 is a schematic diagram of a MLCC chip plated with the silver terminal electrode paste of the present invention to form a finished product.
Description of reference numerals:
1: MLCC chip, 2: metal electrode underlayer, 3: an electrode layer of a conductive resin,
4: nickel metal plating metal layer, 5: tin or tin-lead is plated with the metal layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
First embodiment
Putting pyromellitic dianhydride monomer and 4, 4-diaminodiphenyl ether monomer into a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa, and standing for 4 hours for drying treatment; then dissolving 4, 4-diaminodiphenyl ether with formula amount in N, N-Dimethylformamide (DMF) solvent until 4, 4-diaminodiphenyl ether is completely dissolved, adding pyromellitic dianhydride with formula amount and reacting for 5 hours, controlling the mass fraction of the polyamide acid resin in the solution at 18% to obtain polyamide acid resin solution with red brown or light yellow, and then adding plasticizer into the polyamide acid resin solution, controlling the viscosity of the polyamide acid resin at 40000 +/-1000 mPa.s, wherein the adding amount of the plasticizer is 20% of the mass of the polyamide acid resin.
Adding silver powder into a solvent N, N-Dimethylformamide (DMF), adding a titanate coupling agent accounting for 0.5 percent of the mass of the silver powder, and obtaining pretreated silver powder after ultrasonic dispersion and filtration; and then adding the pretreated silver powder into the reacted polyamic acid resin solution, and stirring for 4-6 hours at a high speed by using a stirring reaction kettle. Then pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the polyamide acid resin; pouring the defoamed slurry into a three-roller grinder for rolling to obtain slurry with the fineness meeting the requirement, filtering the slurry through 500-mesh filter cloth, and bottling and storing the filtered slurry.
The process of rolling the defoamed slurry by the three-roller grinder can ensure that the silver powder in the slurry is fully mixed in the slurry and the agglomerated silver powder is ground. The silver powder accounts for 60% of the slurry, the silver powder is formed by mixing spherical particles and flaky particles, the mass ratio of the spherical particles to the flaky particles in the silver powder is 1:5, the particle size of the spherical particles is 0.5-5 um, and the particle size of the flaky particles is 0.5-10 um.
The silver powder can be replaced by silver-coated copper powder, silver-coated aluminum powder, silver-coated carbon fiber powder, silver-coated glass bead powder or other metal coating powder, and the mass fraction of metal contained in the metal coating powder is 10-70%.
The decomposition temperature of the slurry prepared by the method is 350 ℃. When in use, coating the paste prepared in the manner on two ends of the MLCC chip 1 on which the metal electrode bottom layer 2 is formed by using an end coating machine, and then drying the product coated with the paste according to a specific drying curve, wherein the temperature is increased in a gradient manner from 80 ℃ to 150 ℃ during drying so as to further remove the solvent in the paste, thereby forming a polyamic acid resin dry film; and finally, treating the MLCC chip in an oven at 160 ℃ for 1h, and then at 200 ℃ for 4h to finish imidization so as to form conductive resin electrode layers 3 at two ends of the MLCC chip 1, and then sequentially carrying out links of generating a nickel metal plating metal layer 4 and a tin or tin-lead plating metal layer 5, wherein the final finished product is shown in figure 1.
Second embodiment
Putting a biphenyltetracarboxylic dianhydride monomer and a 4, 4-diaminodiphenylmethane monomer into a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa, and standing for 4 hours for drying treatment; and then dissolving 4, 4-diaminodiphenylmethane with the formula amount in a solvent N, N-dimethylacetamide (DMAc), adding the biphenyl tetracarboxylic anhydride dianhydride with the formula amount after the 4, 4-diaminodiphenylmethane is completely dissolved, reacting for 5 hours, controlling the mass fraction of the polyamide acid resin in the solution to be 15 percent to obtain a polyamide acid resin solution with red brown or light yellow, and then adding a plasticizer into the polyamide acid resin solution to control the viscosity of the polyamide acid resin to be 35000 +/-1000 mPa.s. The amount of the plasticizer added is 30% by mass of the polyamic acid resin.
Adding silver powder into a solvent N, N-dimethylacetamide (DMAc), adding a silane coupling agent accounting for 1% of the mass of the silver powder, and performing ultrasonic dispersion and filtration to obtain pretreated silver powder; and then adding the pretreated silver powder into the reacted polyamic acid resin solution, and stirring for 4-6 hours at a high speed by using a stirring reaction kettle. Then pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the polyamide acid resin; pouring the defoamed slurry into a three-roller grinder for rolling to obtain slurry with the fineness meeting the requirement, filtering the slurry through 500-mesh filter cloth, and bottling and storing the filtered slurry.
The process of rolling the defoamed slurry by the three-roller grinder can ensure that the silver powder in the slurry is fully mixed in the slurry and the agglomerated silver powder is ground. The silver powder accounts for 65% of the mass fraction of the slurry, the silver powder is formed by mixing spherical particles and flaky particles, the ratio of the spherical particles to the flaky particles in the silver powder is 1:1, the particle size of the spherical particles is 0.5-5 um, and the particle size of the flaky particles is 0.5-10 um.
The decomposition temperature of the slurry prepared in the above manner was 320 ℃. When in use, coating the paste prepared in the manner on two ends of the MLCC chip 1 on which the metal electrode bottom layer 2 is formed by using an end coating machine, and then drying the product coated with the paste according to a specific drying curve, wherein the temperature is increased in a gradient manner from 80 ℃ to 150 ℃ during drying so as to further remove the solvent in the paste, thereby forming a polyamic acid resin dry film; and finally, treating the MLCC chip in an oven at 160 ℃ for 1h, and then at 200 ℃ for 4h, so as to finish imidization to form conductive resin electrode layers 3 at two ends of the MLCC chip 1, and then sequentially generating a nickel metal plating metal layer 4 and a tin or tin-lead plating metal layer 5. The final product is shown in fig. 1.
Third embodiment
Putting 4, 4-oxydiphthalic anhydride monomer and p-phenylenediamine monomer into a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa, and standing for 4 hours for drying treatment; and then dissolving the formula amount of p-phenylenediamine in a solvent N-methyl pyrrolidone (NMP), adding the formula amount of 4, 4-oxydiphthalic anhydride and reacting for 5 hours after the p-phenylenediamine is completely dissolved, controlling the mass fraction of the polyamic acid resin in the solution to be 12% to obtain a polyamic acid resin solution presenting red brown or light yellow, and adding a plasticizer into the polyamic acid resin solution, wherein the viscosity of the polyamic acid resin is controlled to be 30000 +/-1000 mPa.s, and the adding amount of the plasticizer is 25% of the mass of the polyamic acid resin.
Adding silver powder into a solvent N-methylpyrrolidone (NMP), adding a titanate coupling agent accounting for 2% of the mass of the silver powder, and obtaining pretreated silver powder after ultrasonic dispersion and filtration; and then adding the pretreated silver powder into the reacted polyamic acid resin solution, and stirring for 4-6 hours at a high speed by using a stirring reaction kettle. Then pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the polyamide acid resin; pouring the defoamed slurry into a three-roller grinder for rolling to obtain slurry with the fineness meeting the requirement, filtering the slurry through 500-mesh filter cloth, and bottling and storing the filtered slurry.
The process of rolling the defoamed slurry by the three-roller grinder can ensure that the silver powder in the slurry is fully mixed in the slurry and the agglomerated silver powder is ground. The silver powder accounts for 70% of the slurry, the silver powder is formed by mixing spherical particles and flaky particles, the ratio of the spherical particles to the flaky particles in the silver powder is 5:1, the particle size of the spherical particles is 0.5-5 um, and the particle size of the flaky particles is 0.5-10 um.
The decomposition temperature of the slurry prepared in the above manner was 340 ℃. When in use, coating the paste prepared in the manner on two ends of the MLCC chip 1 on which the metal electrode bottom layer 2 is formed by using an end coating machine, and then drying the product coated with the paste according to a specific drying curve, wherein the temperature is increased in a gradient manner from 80 ℃ to 150 ℃ during drying so as to further remove the solvent in the paste, thereby forming a polyamic acid resin dry film; and finally, treating the MLCC chip in an oven at 160 ℃ for 1h, and then at 200 ℃ for 4h to finish imidization so as to form conductive resin electrode layers 3 at two ends of the MLCC chip 1, and then sequentially carrying out links of generating a nickel metal plating metal layer 4 and a tin or tin-lead plating metal layer 5, wherein the final finished product is shown in figure 1.
Fourth embodiment
Placing trimellitic anhydride acyl chloride monomer and 2,2 '-dimethyl-4, 4' -diaminobiphenyl monomer into a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa, and standing for 4 hours for drying treatment; then dissolving 2,2 '-dimethyl-4, 4' -diaminobiphenyl with formula amount in solvent N, N-Dimethylformamide (DMF) until 2,2 '-dimethyl-4, 4' -diaminobiphenyl is completely dissolved, adding trimellitic anhydride acyl chloride with formula amount and reacting for 5 hours, controlling the mass fraction of polyamide acid resin in the solution to be 9% to obtain polyamide acid resin solution with reddish brown or light yellow, adding plasticizer into the polyamide acid resin solution, controlling the viscosity of the polyamide acid resin to be 25000 +/-1000 mPa.s, and controlling the adding amount of the plasticizer to be 10% of the mass of the polyamide acid resin.
Adding silver powder into a solvent N, N-Dimethylformamide (DMF), adding a silane coupling agent accounting for 3% of the mass of the silver powder, and performing ultrasonic dispersion and filtration to obtain pretreated silver powder; and then adding the pretreated silver powder into the reacted polyamic acid resin solution, and stirring for 4-6 hours at a high speed by using a stirring reaction kettle. Then pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the polyamide acid resin; pouring the defoamed slurry into a three-roller grinder for rolling to obtain slurry with the fineness meeting the requirement, filtering the slurry through 500-mesh filter cloth, and bottling and storing the filtered slurry.
The process of rolling the defoamed slurry by the three-roller grinder can ensure that the silver powder in the slurry is fully mixed in the slurry and the agglomerated silver powder is ground. The silver powder accounts for 75% of the mass of the slurry, the silver powder is formed by mixing spherical particles and flaky particles, the ratio of the spherical particles to the flaky particles in the silver powder is 1:3, the particle size of the spherical particles is 0.5-5 um, and the particle size of the flaky particles is 0.5-10 um.
The decomposition temperature of the slurry prepared in the above manner was 380 ℃. When in use, coating the paste prepared in the manner on two ends of the MLCC chip 1 on which the metal electrode bottom layer 2 is formed by using an end coating machine, and then drying the product coated with the paste according to a specific drying curve, wherein the temperature is increased in a gradient manner from 80 ℃ to 150 ℃ during drying so as to further remove the solvent in the paste, thereby forming a polyamic acid resin dry film; and finally, treating the MLCC chip in an oven at 160 ℃ for 1h, and then at 200 ℃ for 4h to finish imidization so as to form conductive resin electrode layers 3 at two ends of the MLCC chip 1, and then sequentially carrying out links of generating a nickel metal plating metal layer 4 and a tin or tin-lead plating metal layer 5, wherein the final finished product is shown in figure 1.
Fifth embodiment
Putting pyromellitic dianhydride monomer and 1, 4-bis (4-aminophenoxy) benzene monomer into a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa, and standing for 4 hours for drying treatment; then dissolving 1, 4-bis (4-aminophenoxy) benzene with the formula amount in a solvent N, N-dimethylacetamide (DMAc) until the 1, 4-bis (4-aminophenoxy) benzene is completely dissolved, adding pyromellitic dianhydride with the formula amount and reacting for 5 hours, controlling the mass fraction of the polyamic acid resin in the solution to be 6 percent to obtain a polyamic acid resin solution with reddish brown or light yellow, and adding a plasticizer into the polyamic acid resin solution, wherein the viscosity of the polyamic acid resin is controlled to be 20000 +/-1000 mPa.s, and the adding amount of the plasticizer is 5 percent of the mass of the polyamic acid resin.
Adding silver powder into a solvent N, N-dimethylacetamide (DMAc), adding a titanate coupling agent accounting for 5% of the mass of the silver powder, and performing ultrasonic dispersion and filtration to obtain pretreated silver powder; and then adding the pretreated silver powder into the reacted polyamic acid resin solution, and stirring for 4-6 hours at a high speed by using a stirring reaction kettle. Then pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the polyamide acid resin; pouring the defoamed slurry into a three-roller grinder for rolling to obtain slurry with the fineness meeting the requirement, filtering the slurry through 500-mesh filter cloth, and bottling and storing the filtered slurry.
The process of rolling the defoamed slurry by the three-roller grinder can ensure that the silver powder in the slurry is fully mixed in the slurry and the agglomerated silver powder is ground. Wherein the mass fraction of the silver powder in the obtained slurry is 80%, the silver powder is mainly flaky particles, and the granularity of the flaky particles forming the silver powder is between 0.5um and 10 um.
The decomposition temperature of the slurry prepared by the method is 400 ℃. When in use, coating the paste prepared in the manner on two ends of the MLCC chip 1 on which the metal electrode bottom layer 2 is formed by using an end coating machine, and then drying the product coated with the paste according to a specific drying curve, wherein the temperature is increased in a gradient manner from 80 ℃ to 150 ℃ during drying so as to further remove the solvent in the paste, thereby forming a polyamic acid resin dry film; and finally, treating the MLCC chip in an oven at 160 ℃ for 1h, and then at 200 ℃ for 4h to finish imidization so as to form conductive resin electrode layers 3 at two ends of the MLCC chip 1, and then sequentially carrying out links of generating a nickel metal plating metal layer 4 and a tin or tin-lead plating metal layer 5, wherein the final finished product is shown in figure 1.
Sixth embodiment
Placing trimellitic anhydride acyl chloride monomer and 1,3 bis (4-aminophenoxy) benzene monomer into a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa, and placing for 4 hours for drying treatment; then dissolving 1,3 bis (4-aminophenoxy) benzene with the formula amount in a solvent N-methyl pyrrolidone (NMP) until the 1,3 bis (4-aminophenoxy) benzene is completely dissolved, adding trimellitic anhydride acyl chloride with the formula amount, reacting for 5 hours, controlling the mass fraction of the polyamic acid resin in the solution to be 3 percent to obtain a polyamic acid resin solution presenting reddish brown or light yellow, and adding a plasticizer into the polyamic acid resin solution, wherein the viscosity of the polyamic acid resin is controlled to be 10000 +/-1000 mPa.s, and the adding amount of the plasticizer is 15 percent of the mass of the polyamic acid resin.
Adding silver powder into a solvent N-methylpyrrolidone (NMP), adding a silane coupling agent accounting for 5% of the mass of the silver powder, and performing ultrasonic dispersion and filtration to obtain pretreated silver powder; and then adding the pretreated silver powder into the reacted polyamic acid resin solution, and stirring for 4-6 hours at a high speed by using a stirring reaction kettle. Then pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the polyamide acid resin; pouring the defoamed slurry into a three-roller grinder for rolling to obtain slurry with the fineness meeting the requirement, filtering the slurry through 500-mesh filter cloth, and bottling and storing the filtered slurry.
The process of rolling the defoamed slurry by the three-roller grinder can ensure that the silver powder in the slurry is fully mixed in the slurry and the agglomerated silver powder is ground. The mass fraction of the silver powder in the obtained slurry is 85%, the silver powder is formed by mixing spherical particles and flaky particles, the mass ratio of the spherical particles to the flaky particles in the silver powder is 3:1, the particle size of the spherical particles is 0.5-5 um, and the particle size of the flaky particles is 0.5-10 um.
The decomposition temperature of the slurry prepared by the method is 350 ℃. When in use, coating the paste prepared in the manner on two ends of the MLCC chip 1 on which the metal electrode bottom layer 2 is formed by using an end coating machine, and then drying the product coated with the paste according to a specific drying curve, wherein the temperature is increased in a gradient manner from 80 ℃ to 150 ℃ during drying so as to further remove the solvent in the paste, thereby forming a polyamic acid resin dry film; and finally, treating the MLCC chip in an oven at 160 ℃ for 1h, and then at 200 ℃ for 4h to finish imidization so as to form conductive resin electrode layers 3 at two ends of the MLCC chip 1, and then sequentially carrying out links of generating a nickel metal plating metal layer 4 and a tin or tin-lead plating metal layer 5, wherein the final finished product is shown in figure 1.
The silver terminal electrode slurry for the low-temperature cured thermoplastic polyimide MLCC is prepared by directly mixing the conductive particles and the polyamic acid resin, and the preparation method is simple and convenient. In addition, the electrode prepared by the silver terminal electrode slurry has excellent mechanical property, and the heat-resistant temperature can reach 250-400 ℃, so the electrode can be widely applied in a wider range.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or terminal that comprises the element.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A preparation method of silver end electrode slurry for low-temperature cured thermoplastic polyimide MLCC is characterized in that,
the silver end electrode slurry is coated on the metal electrode bottom layers at two ends of the MLCC chip and dried to form conductive resin electrode layers; sequentially electroplating a nickel metal electroplating metal layer and a tin or tin-lead electroplating metal layer on the conductive resin electrode layer; the silver end electrode slurry comprises conductive particles and polyamide acid resin, the silver end electrode slurry does not contain a curing agent, the polyamide acid resin is thermoplastic polyimide, and the curing is realized by imidization; the conductive particles and the polyamic acid resin are uniformly mixed, the mass fraction of the conductive particles in the silver end electrode slurry is between 60% and 85%, and the viscosity of the polyamic acid resin is between 10000mPa.s and 40000 mPa.s; the conductive particles are a combination of spherical particles and flaky particles, and the conductive particles are silver powder; the mass ratio of spherical particles to flaky particles in the conductive particles is 1:5 or 1: 3; the granularity range of the spherical particles is between 0.5um and 5um, and the granularity of the flaky particles is between 0.5um and 10 um;
the preparation method comprises the following steps:
adding conductive particles into an organic solvent, adding a coupling agent into the organic solvent, performing ultrasonic dispersion, and filtering to obtain pretreated conductive particles, wherein the addition amount of the coupling agent is 0.5-5% of the mass of the conductive particles;
obtaining polyamic acid resin through polymerization of diamine and dianhydride, wherein the viscosity of the polyamic acid resin is 10000-40000 mPa.s;
adding the pretreated conductive particles into the polyamic acid resin, and stirring for 4-6 hours in a reaction kettle to uniformly disperse the pretreated conductive particles in the polyamic acid resin to obtain a mixture of the pretreated conductive particles and the polyamic acid resin;
pouring the mixture into a vacuum defoaming kettle, and removing bubbles in the mixture;
rolling the defoamed mixture by a grinder to obtain slurry with the fineness of below 10 um;
filtering the slurry through filter cloth, and then canning and storing the slurry;
wherein the step of obtaining the polyamic acid resin by polymerization of a diamine and a dianhydride comprises:
placing dianhydride and diamine in a vacuum drying oven with the temperature of 60 ℃ and the vacuum degree of 0.01MPa for 4 hours, and drying;
dissolving dried diamine in a solvent, and adding dried dianhydride into the solvent to react for 5 hours after the diamine is completely dissolved to obtain a polyamic acid resin solution; the mass fraction of the polyamic acid resin in the solution is between 3% and 18%;
adding a plasticizer into the solution, wherein the plasticizer is dimethyl phthalate to obtain polyamide acid resin with the viscosity of 10000-40000 mPa.s; the addition amount of the plasticizer is 5-30% of the mass of the polyamic acid resin.
2. The method for preparing silver terminal electrode paste for a low temperature cured thermoplastic polyimide MLCC according to claim 1, wherein the mesh number of the filter cloth in the step of canning and storing the paste after filtering the paste through the filter cloth is 500 meshes.
3. The method for preparing silver end electrode paste for low temperature curing thermoplastic polyimide MLCC according to claim 1, wherein the dianhydride is one of pyromellitic dianhydride, 4-oxydiphthalic anhydride, trimellitic anhydride acid chloride; the diamine is one of 4, 4-diaminodiphenyl ether, 4-diaminodiphenylmethane, p-phenylenediamine, 2 '-dimethyl-4, 4' -diaminobiphenyl, 1, 4-bis (4-aminophenoxy) benzene and 1, 3-bis (4-aminophenoxy) benzene.
4. The method for preparing silver terminal electrode paste for low temperature cured thermoplastic polyimide MLCC according to claim 1, wherein the organic solvent is one of N, N-dimethylformamide, N-dimethylacetamide and N-methylpyrrolidone; the coupling agent is a titanate coupling agent or a silane coupling agent.
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| CN113192664A (en) * | 2021-06-17 | 2021-07-30 | 航天特种材料及工艺技术研究所 | High-temperature-resistant resin-based conductive silver paste and preparation method thereof |
| CN115458330A (en) * | 2022-09-20 | 2022-12-09 | 广州创天电子科技有限公司 | Conductive resin composition, ceramic capacitor and preparation method thereof |
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