Conductive silver paste for co-fired ceramic inner electrode and preparation method of conductive silver paste

Abstract

The invention discloses conductive silver paste for a co-fired ceramic inner electrode and a preparation method of the conductive silver paste. The conductive silver paste comprises the following components in percentage by mass: 80%-90% of silver particles, 0%-10% of an inorganic additive, 5%-20% of a carrier, 0.6%-0.9% of an inorganic additive, 0.3%-1% of an auxiliary agent, 0.2%-0.4% of an organic additive and 0.8%-5% of an organic solvent. The preparation method comprises the following steps: mixing raw materials, dispersing, adjusting and filtering. Conductive silver particles are prepared through a chemical synthesis method, and the silver powder particles are further stirred and sheared to be refined, so that the purity of the silver particles is higher, and the conductivity is improved; meanwhile, the dispersity and the stability of the conductive particles are improved by adding auxiliaries, and the fluidity and the viscosity of the slurry are adjusted by utilizing an organic solvent, so that the slurry can cover the surface of a ceramic body in a better fit manner, the situation that silver ions permeate and diffuse to the ceramic substrate in the co-firing process of the electric silver slurry and the ceramic substrate is avoided, and the insulativity of the ceramic substrate is improved.

Description

Technical Field

[0001] The invention relates to the technical field of conductive pastes, in particular to a conductive silver paste for co-fired ceramic inner electrodes and a preparation method thereof. Background Art

[0002] Low temperature co-fired ceramic technology is a technology that prints interconnected conductors, components and circuits on unsintered cast ceramic materials, and then laminates and presses the structure together, and then sinters it into an integrated ceramic multilayer material technology. The printed conductors are metals such as silver, copper, and gold. They can be made into high-density circuits that do not interfere with each other in three-dimensional space, or three-dimensional circuit substrates with built-in passive components. Integrated circuits (ICs) and active devices can be mounted on its surface to make active / passive integrated functional modules, further miniaturizing and densifying the circuit. With the development of science and technology, the demand for miniaturization and high-density integration of electronic integration is getting higher and higher, especially in special fields such as aerospace, communications, military, and medical care, which has brought unprecedented challenges to the electronic packaging industry.

[0003] At present, China is still far behind foreign countries in the overall development progress of LTCC electronic components, especially in terms of the practicality and popularity of ceramic raw tapes and matching complete sets of electronic pastes, which are still behind well-known foreign companies, such as Dupont and Ferro in the United States, Dazhou in South Korea, and Daiken in Japan. LTCC silver paste is divided into four types: internal electrode conductive silver paste, hole electrode conductive silver paste, surface electrode conductive silver paste and terminal electrode conductive silver paste. Due to different functions and application locations, they have different special performance requirements, which also increases the difficulty of developing conductive pastes. In particular, the internal electrode conductive silver paste, hole electrode conductive silver paste and surface electrode conductive silver paste are co-fired electronic pastes. In addition to considering the sintering performance of the silver layer itself, they must also have good co-fired matching with the LTCC ceramic body. Otherwise, if the co-fired matching is not matched, defects such as bending of the ceramic body after sintering and deformation of the electrode line shrinkage path will occur, which seriously affects the product quality and practicality. As a co-fired conductive silver paste in the application of LTCC technology, surface electrode conductive silver paste is mainly used for printing on the outer surface of LTCC components for connecting external circuits, such as delay lines, etc. Therefore, its sintering density, shrinkage matching with the ceramic body, and adhesion are particularly important. Compared with traditional conductive silver paste, during the co-firing process of LTCC conductive silver paste and ceramic substrate, silver ions will penetrate and diffuse into the ceramic substrate, resulting in a decrease in the insulation of the ceramic substrate, the risk of circuit breakdown and other sintering defects. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a conductive silver paste for co-fired ceramic inner electrodes and a preparation method thereof, so as to solve the problem that the existing silver ions will penetrate and diffuse into the ceramic matrix, resulting in a decrease in the insulation of the ceramic matrix.

[0005] Embodiment 1 To achieve the above objectives, the present invention is implemented through the following technical scheme: a conductive silver paste for co-fired ceramic inner electrodes, which includes the following components calculated by mass percentage: 80% to 90% of silver particles, 0% to 10% of inorganic additives, 5% to 20% of carriers, 0.6% to 0.9% of inorganic additives, 0.3% to 1% of additives, 0.2% to 0.4% of organic additives, and 0.8% to 5% of organic solvents.

[0006] Preferably, the silver particles are obtained by adding a reducing agent to a silver salt or nitrate solution to obtain nano-scale silver particles.

[0007] Preferably, the inorganic additive comprises the following components calculated by mass percentage: 27% Al2O3, 21.62% SiO2, 18.92% Bi2O3, 24.32% CaCO3, and 8.11% SrCaO3.

[0008] Preferably, the carrier comprises a mixture of the following components calculated by mass percentage: 10% to 30% of a special resin and 80% to 85% of a solvent, and the special resin is selected from one or a mixture of two or more of esters, alcohol esters, and celluloses, and the solvent is selected from one or a mixture of two of alcohols and ethers.

[0009] Preferably, the organic additives include at least a leveling agent, a coupling agent, a defoaming agent, and a thixotropic agent.

[0010] Preferably, the auxiliary agent includes a silane coupling agent.

[0011] Preferably, the organic solvent is selected from one or two of alcohols and ethers, the alcohol includes one or a mixture of terpineol and butyl carbitol acetate, and the ether includes one or a mixture of two or more of diethylene glycol butyl ether, diethylene glycol ethyl ether and diethylene glycol butyl ether acetate.

[0012] A method for preparing a conductive silver paste for inner electrodes of co-fired ceramics, which is applied to the conductive silver paste for inner electrodes of co-fired ceramics described above, comprises the following steps: S1. Mixing and stirring the raw materials: mixing polymer resins of different component strengths in a certain proportion, and then mixing with organic solvents and organic additives in a certain proportion and fully dissolving them to obtain the required organic carrier; then uniformly mixing glass powder, inorganic additives and a part of the organic carrier, and then fully grinding them with a three-roll mill to obtain glass slurry with moderate viscosity and good dispersibility, and then uniformly mixing the glass slurry with the remaining organic carrier and silver particles to obtain a mixture.

[0013] S2, dispersing the mixture obtained after mixing S1: using a high-speed mixer for high-speed stirring and shearing to further refine the silver powder particles and improve the conductive performance. The time and speed need to be controlled during the dispersion process to ensure that the silver powder particles reach the required fineness. The dispersion fineness of the slurry is controlled to be no more than 5 microns, and the viscosity of the slurry is controlled in the range of 100-200 Pa·s.

[0014] S3. After dispersion, adjust the conductive silver paste according to specific requirements: add additives to the silver paste, adjust viscosity and conductivity, etc. Additives can improve the stability and processability of the conductive silver paste, and adjusting the viscosity can control the thickness and fluidity of the coating.

[0015] S4. Filter the adjusted conductive silver paste: The adjusted conductive silver paste needs to be filtered to remove impurities and particles therein. Usually, a microporous filter membrane or mesh filter is used for filtering to ensure the purity and stability of the conductive silver paste.

[0016] Preferably, the silver particles, the organic solvent and the surfactant are mixed in a certain proportion to ensure that the silver particles are fully wetted and to avoid accumulation and agglomeration.

[0017] The present invention provides a conductive silver paste for co-fired ceramic inner electrodes and a preparation method thereof, which has the following beneficial effects: The present invention prepares conductive silver particles by a chemical synthesis method, and further stirs and shears the silver powder particles to refine them, so that the purity of the silver particles is higher and the conductive performance is improved; at the same time, auxiliary agents are added to improve the dispersibility and stability of the conductive particles, and the fluidity and viscosity of the slurry are adjusted by an organic solvent, so that the slurry can be more closely covered on the surface of the ceramic body, and silver ions are prevented from penetrating and diffusing into the ceramic matrix during the co-firing process of the electro-silver slurry and the ceramic matrix, thereby improving the insulation of the ceramic matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the preparation process of the present invention; DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] Embodiment 1 A conductive silver paste for co-fired ceramic inner electrodes comprises the following components calculated by mass percentage: 80% to 90% of silver particles, 0% to 10% of inorganic additives, 5% to 20% of carriers, 0.6% to 0.9% of inorganic additives, 0.3% to 1% of auxiliary agents, 0.2% to 0.4% of organic additives, and 0.8% to 5% of organic solvents.

[0021] In this embodiment, silver particles are obtained by adding a reducing agent to a silver salt or nitrate solution to obtain nano-scale silver particles; as a preferred embodiment, first, a silver salt, such as silver nitrate, is added to a solvent, and then, the silver salt is reduced to nano-scale silver particles by the action of a reducing agent, and finally, pure conductive particles are obtained through steps such as centrifugation and washing.

[0022] In this embodiment, the inorganic additives include the following components calculated by mass percentage: 27% Al2O3, 21.62% SiO2, 18.92% Bi2O3, 24.32% CaCO3, and 8.11% SrCaO3.

[0023] In this embodiment, the carrier comprises a mixture of the following components calculated by mass percentage: 10% to 30% of a special resin and 80% to 85% of a solvent, and the special resin is selected from one or a mixture of two or more of esters, alcohol esters, and celluloses, and the solvent is selected from one or a mixture of two of alcohols and ethers.

[0024] In this embodiment, the organic additives include at least a leveling agent, a coupling agent, a defoaming agent, and a thixotropic agent. As a preferred embodiment, by adding a leveling agent, the slurry forms a flat, smooth, and uniform coating during the drying and film-forming process. The leveling agent is a type of substance that can effectively reduce the surface tension of the slurry and improve its leveling and uniformity. At the same time, it can improve the permeability of the slurry, increase its coverage, and make the film formation uniform and natural.

[0025] In this embodiment, the auxiliary agent includes a silane coupling agent. By adding the silane coupling agent, the bonding strength, water resistance, weather resistance and other properties of the slurry can be improved, and the overall performance of the electrode conductive silver paste can be enhanced.

[0026] In this embodiment, the organic solvent is selected from one or two of alcohols and ethers, the alcohol includes one or a mixture of pineol and butyl carbitol acetate, and the ether includes one or a mixture of diethylene glycol butyl ether, diethylene glycol ethyl ether, and diethylene glycol butyl ether acetate.

[0027] Embodiment 2 A method for preparing a conductive silver paste for co-fired ceramic inner electrodes, which is applied to the above-mentioned conductive silver paste for co-fired ceramic inner electrodes, comprises the following steps: S1. Mixing and stirring the raw materials: mixing polymer resins of different component strengths in a certain proportion, and then mixing with organic solvents and organic additives in a certain proportion and fully dissolving them to obtain the required organic carrier; then uniformly mixing glass powder, inorganic additives and a part of the organic carrier, and then fully grinding them with a three-roll mill to obtain glass slurry with moderate viscosity and good dispersibility, and then uniformly mixing the glass slurry with the remaining organic carrier and silver particles to obtain a mixture.

[0028] As a preferred embodiment, the prepared conductive particles are mixed with materials such as dispersants, solvents and additives to form a slurry. The addition of dispersants can improve the dispersibility and stability of the conductive particles, the solvent is used to adjust the fluidity and viscosity of the slurry, and the addition of additives can improve the processing performance of the conductive slurry.

[0029] S2, dispersing the mixture obtained after mixing S1: using a high-speed mixer for high-speed stirring and shearing to further refine the silver powder particles and improve the conductive performance. The time and speed need to be controlled during the dispersion process to ensure that the silver powder particles reach the required fineness. The dispersion fineness of the slurry is controlled to be no more than 5 microns, and the viscosity of the slurry is controlled in the range of 100-200 Pa·s.

[0030] As a preferred embodiment, the conductive particles in the conductive silver paste tend to aggregate, affecting its conductive properties. Therefore, the paste needs to be dispersed. Commonly used dispersion methods include ultrasonic dispersion, mechanical shear dispersion, etc. These methods can effectively disperse the conductive particles and improve the uniformity and stability of the conductive silver paste.

[0031] S3. After dispersion, adjust the conductive silver paste according to specific requirements: add additives to the silver paste, adjust viscosity and conductivity, etc. Additives can improve the stability and processability of the conductive silver paste, and adjusting the viscosity can control the thickness and fluidity of the coating.

[0032] As a preferred embodiment, the obtained slurry usually needs to go through a series of adjustment and optimization processes. First, the viscosity of the slurry needs to be adjusted to adapt to different processing requirements. Second, the conductivity and stability of the slurry need to be optimized to improve its use effect. The slurry performance can be optimized by adding appropriate amounts of additives and adjusting process parameters.

[0033] S4. Filter the adjusted conductive silver paste: The adjusted conductive silver paste needs to be filtered to remove impurities and particles therein. Usually, a microporous filter membrane or mesh filter is used for filtering to ensure the purity and stability of the conductive silver paste.

[0034] As a preferred embodiment, the conductive silver paste after dispersion treatment needs to be filtered and dried to remove impurities and solvents therein. First, the slurry is filtered to remove solid substances such as particles and impurities, and then the solvent in the slurry is completely removed by drying to obtain pure conductive silver paste.

[0035] In this embodiment, silver particles, organic solvent and surfactant are mixed in a certain proportion to ensure that the silver particles are fully wetted and to avoid accumulation and agglomeration. The conductive particles are usually prepared by chemical synthesis.

[0036] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A conductive silver paste for co-fired ceramic inner electrodes, characterized in that: The composition includes the following components calculated by mass percentage: 80% to 90% of silver particles, 0% to 10% of inorganic additives, 5% to 20% of carriers, 0.6% to 0.9% of inorganic additives, 0.3% to 1% of auxiliary agents, 0.2% to 0.4% of organic additives, and 0.8% to 5% of organic solvents.

2. The conductive silver paste for co-fired ceramic inner electrodes according to claim 1, characterized in that: The silver particles are obtained by adding a reducing agent into a silver salt or nitrate solution to obtain nanometer-scale silver particles.

3. The conductive silver paste for co-fired ceramic inner electrodes according to claim 1, characterized in that: The inorganic additives include the following components calculated by mass percentage: 27% Al2O3, 21.62% SiO2, 18.92% Bi2O3, 24.32% CaCO3, and 8.11% SrCaO3.

4. The conductive silver paste for co-fired ceramic inner electrodes according to claim 1, characterized in that The carrier comprises a mixture of the following components calculated by mass percentage: 10% to 30% of a special resin and 80% to 85% of a solvent, and the special resin is selected from one or a mixture of two or more of esters, alcohol esters, and celluloses, and the solvent is selected from one or a mixture of two of alcohols and ethers.

5. The conductive silver paste for co-fired ceramic inner electrodes according to claim 1, characterized in that: The organic additives at least include a leveling agent, a coupling agent, a defoaming agent, and a thixotropic agent.

6. The conductive silver paste for co-fired ceramic inner electrodes and the preparation method thereof according to claim 1, characterized in that: The auxiliary agent includes a silane coupling agent.

7. The conductive silver paste for co-fired ceramic inner electrodes according to claim 1, characterized in that: The organic solvent is selected from one or two of alcohols and ethers, the alcohol includes one or a mixture of terpineol and butyl carbitol acetate, and the ether includes one or a mixture of diethylene glycol butyl ether, diethylene glycol ethyl ether, and diethylene glycol butyl ether acetate.

8. A method for preparing a conductive silver paste for inner electrodes of co-fired ceramics, applied to the conductive silver paste for inner electrodes of co-fired ceramics as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Mixing and stirring the raw materials: mixing polymer resins of different strengths in a certain proportion, and then mixing with organic solvents and organic additives in a certain proportion to fully dissolve to obtain the required organic carrier; then uniformly mixing glass powder, inorganic additives and a part of the organic carrier, and then fully grinding with a three-roll mill to obtain glass slurry with moderate viscosity and good dispersibility, and then uniformly mixing the glass slurry with the remaining organic carrier and silver particles to obtain a mixture S2, dispersing the mixture obtained after mixing S1: using a high-speed mixer for high-speed stirring and shearing to further refine the silver powder particles and improve the conductivity. The time and speed need to be controlled during the dispersion process to ensure that the silver powder particles reach the required fineness. The dispersion fineness of the slurry is controlled to be no more than 5 microns, and the viscosity of the slurry is controlled in the range of 100-200 Pa·s S3. After dispersion, adjust the conductive silver paste according to specific requirements: add additives to the silver paste, adjust viscosity and conductivity, etc. Additives can improve the stability and processability of the conductive silver paste, and adjusting the viscosity can control the thickness and fluidity of the coating. S4. Filter the adjusted conductive silver paste: The adjusted conductive silver paste needs to be filtered to remove impurities and particles therein. Usually, a microporous filter membrane or mesh filter is used for filtering to ensure the purity and stability of the conductive silver paste.

9. The method for preparing a conductive silver paste for co-fired ceramic inner electrodes according to claim 8, characterized in that: Silver particles, organic solvents and surfactants are mixed in a certain proportion to ensure that the silver particles are fully wetted to avoid accumulation and agglomeration.

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