High-conductivity conductive silver paste and preparation method thereof
阅读说明：本技术 一种高导电性导电银浆及其制备方法 (High-conductivity conductive silver paste and preparation method thereof ) 是由 孙娅 刘飞全 马锦 于 2020-12-24 设计创作，主要内容包括：本发明公开了一种高导电性导电银浆及其制备方法,包括以下步骤：S1、功能相银粉和掺杂银粉分别与玻璃粉和有机载体混合均匀,过三辊轧机制得功能相银浆和掺杂银浆,各银粉与玻璃粉和有机载体混合的质量份数比例为60-85∶3-12∶12-30；S2、将功能相银浆和掺杂银浆按30-85∶15-70份搅拌混合均匀,制得高导电性导电银浆。通过不同的银粉先分别制备银浆,再按比例搅拌混合成高导电性导电银浆,避免各银粉因不同的粒度同时通过三辊轧机时,造成的研磨混合不均；同时便于对高导电性导电银浆按不同含量的银浆进行配比,混合过程更方便快捷,利于实验探究。(The invention discloses a high-conductivity conductive silver paste and a preparation method thereof, wherein the preparation method comprises the following steps: s1, respectively and uniformly mixing the functional phase silver powder and the doped silver powder with the glass powder and the organic carrier, and preparing the functional phase silver paste and the doped silver paste through a three-roll mill, wherein the mixing mass part ratio of the silver powder to the glass powder to the organic carrier is 60-85: 3-12: 12-30; s2, stirring and mixing the functional phase silver paste and the doped silver paste uniformly according to the ratio of 30-85: 15-70 to obtain the high-conductivity conductive silver paste. Silver pastes are respectively prepared through different silver powders, and then are stirred and mixed according to a proportion to form the high-conductivity conductive silver paste, so that the problem of uneven grinding and mixing caused by the fact that the silver powders pass through a three-roller mill simultaneously due to different particle sizes is avoided; meanwhile, the high-conductivity conductive silver paste is conveniently matched according to silver pastes with different contents, the mixing process is more convenient and quicker, and experimental exploration is facilitated.)
1. The preparation method of the high-conductivity conductive silver paste is characterized by comprising the following steps:
s1, respectively and uniformly mixing the functional phase silver powder and the doped silver powder with the glass powder and the organic carrier, and preparing the functional phase silver paste and the doped silver paste through a three-roll mill, wherein the mixing mass part ratio of the silver powder to the glass powder to the organic carrier is 60-85: 3-12: 12-30;
s2, stirring and mixing the functional phase silver paste and the doped silver paste uniformly according to the ratio of 30-85: 15-70 to obtain the high-conductivity conductive silver paste.
2. The method for preparing the high-conductivity conductive silver paste according to claim 1, wherein the functional phase silver powder and the doped silver powder are prepared by using the same dispersant system.
3. The method for preparing high-conductivity conductive silver paste according to claim 1 or 2, wherein in step S1, the functional phase silver powder is micron-sized spherical silver powder, the doped silver powder is one or both of nano silver powder and micron-sized flake silver powder, and the fineness of the functional phase silver powder and the doped silver powder is less than 10 μm.
4. The method for preparing high-conductivity conductive silver paste according to claim 3, wherein the doped silver powder is nano silver powder and micron-sized flake silver powder, and the nano-doped silver paste and the micron-sized flake doped silver paste are prepared by mixing the doped silver powder with glass powder and an organic carrier respectively and passing the mixture through a three-roll mill, wherein the mixing ratio of the functional phase silver paste to the nano-doped silver paste to the micron-sized flake doped silver paste in the high-conductivity conductive silver paste is 35-85: 5-25: 5-40.
5. The method for preparing high-conductivity conductive silver paste according to claim 4, wherein the micron-sized spherical silver powder has an average particle size of 1.0-3.0 μm and tap density>4.0g/cm3The average particle diameter of the nano silver powder is 100nm-200nm, the average flake diameter of the flake silver powder is 1.0-2.0 mu m, and the thickness of the flake layer<100nm。
6. The method for preparing high-conductivity conductive silver paste according to claim 5, wherein the micron-sized spherical silver powder, the nanometer silver powder and the micron-sized plate-shaped silver powder are prepared by using the same dispersant, and the dispersant comprises any one of citric acid, sodium citrate, polyvinylpyrrolidone, polymethacrylamide and ethyl cellulose.
7. The method for preparing high-conductivity conductive silver paste according to claim 6, wherein in step S1, the glass frit is B2O3-SiO2-ZnO-based glass powder.
8. The method for preparing a highly conductive silver paste as recited in claim 7, wherein in step S1, the organic vehicle includes an organic solvent and a thickener, the organic solvent includes one or a mixture of terpineol, butyl carbitol acetate and tributyl citrate, and the thickener includes one or a mixture of ethyl cellulose and nitrocellulose.
9. The method for preparing high-conductivity conductive silver paste according to claim 8, wherein the organic vehicle further comprises an auxiliary agent for adjusting the performance of the organic vehicle, and the auxiliary agent comprises any one of lecithin or castor oil.
10. The high-conductivity conductive silver paste prepared by the preparation method of the high-conductivity conductive silver paste according to any one of claims 1 to 9, wherein the high-conductivity conductive silver paste is subjected to screen printing, drying and sintering to obtain a conductive pattern, and the sheet resistance is tested to be less than 6.0m Ω/□.
Technical Field
The invention belongs to the field of electronic functional materials, relates to a preparation method of conductive paste, and particularly relates to high-conductivity conductive silver paste and a preparation method thereof.
Background
The conductive silver paste is an extremely important conductive and heat-conducting connecting material and is widely applied to the fields of high-power LED patches, solar cell panels, flat panel display panel wire connection, radio frequency identification tags, touch screen frame wiring, thin film switches and the like. In recent years, with the rapid development of industries such as flexible display, capacitive touch screen, thin-film solar cell and the like, the requirements of academic circles and industrial circles on the performance of silver paste are continuously improved; high-performance silver paste materials have become key materials for technical development in various fields. The main components of the silver paste are silver powder and resin, and in order to achieve higher conductivity, the silver content in the silver paste is at least 75% (mass percentage); the conductive silver paste in the current market still faces a plurality of problems such as high cost and poor conductivity. How to reduce the silver content of the silver paste and improve the performances of electric conduction, heat conduction, mechanical connection, reliability and the like of the silver paste while ensuring that the product has good electric conductivity is the key for improving the performances of the silver paste and promoting the mass production of high-end silver paste products. Therefore, in recent years, research on how to reduce the silver content and improve the conductivity has been mainly focused at home and abroad.
The Chinese patent with the application number of 201910119183.1 discloses a mixed conductive silver paste for packaging a nano chip, micron silver powder and nano silver powder are uniformly ground in a three-roller grinding machine to prepare the conductive silver paste, but the particle diameters of the silver powders are different, the silver powders with larger particle diameters are ground firstly in the grinding process, and the mixing uniformity of the silver powders in the ground conductive silver paste is insufficient; the invention discloses a Chinese patent application No. 201710519233.6 and discloses a low-temperature sintering mixed type conductive silver paste for chip packaging and a preparation method thereof, wherein nano-scale spherical silver powder, micron-scale flaky silver powder and submicron-scale spherical silver powder are mixed and stirred uniformly with an organic carrier to prepare the mixed type conductive silver paste, the fineness of each silver powder in the conductive silver paste is not uniform, the surface of each silver powder needs to be modified in the preparation process, the operation is complex, and the mixed type conductive silver paste is difficult to apply to large-scale industrial production.
In view of the above, a new method for preparing a hybrid conductive silver paste is needed to solve the above problems.
Disclosure of Invention
In order to solve the problems of high cost and poor conductivity of the existing conductive silver paste, the invention provides the high-conductivity conductive silver paste and the preparation method thereof. By adopting a proper formula of the glass powder and the organic carrier, the requirements of the slurry on performances such as printing, sintering and the like are met, and the slurry can be applied to the field of electronic functional materials.
The preparation method of the high-conductivity conductive silver paste comprises the following steps:
s1, respectively and uniformly mixing the functional phase silver powder and the doped silver powder with the glass powder and the organic carrier, and preparing the functional phase silver paste and the doped silver paste through a three-roll mill, wherein the mass part ratio of the mixed silver powder to the glass powder to the doped silver paste is 60-85: 3-12: 12-30;
s2, stirring and mixing the functional phase silver paste and the doped silver paste uniformly according to the ratio of 30-85: 15-70 to obtain the high-conductivity conductive silver paste.
Further, the functional phase silver powder and the doped silver powder are obtained by preparation, and the same dispersant system is adopted in the preparation process.
The silver powder is prepared by the existing preparation process, silver salt and deionized water are mixed, dispersant and reducer are added, and after reduction reaction, solid-liquid separation and drying are carried out to obtain the silver powder. The silver salt is silver nitrate.
Further optionally, in step S1, the functional phase silver powder is micron-sized spherical silver powder, the doped silver powder is one or two of nanometer silver powder and micron-sized flake silver powder, and the fineness of the functional phase silver powder and the doped silver powder is less than 10 μm.
Preferably, the doped silver powder is nano silver powder and micron-sized flake silver powder, and is mixed with the glass powder and the organic carrier respectively and then is processed by a three-roll mill to prepare nano doped silver paste and micron-sized flake doped silver paste, and the mixing ratio of the functional phase silver paste to the nano doped silver paste and the micron-sized flake doped silver paste in the high-conductivity conductive silver paste is 35-85: 5-25: 5-40.
Further, the micronThe average grain diameter of the grade spherical silver powder is 1.0-3.0 mu m, and the tap density>4.0g/cm3The average particle diameter of the nano silver powder is 100nm-200nm, the average flake diameter of the flake silver powder is 1.0-2.0 mu m, and the thickness of the flake layer<100nm。
Further, the micron-sized spherical silver powder, the nanometer silver powder and the micron-sized flaky silver powder are prepared by adopting the same dispersing agent, and the dispersing agent comprises any one of citric acid, sodium citrate, polyvinylpyrrolidone, polymethacrylamide and ethyl cellulose.
Preferably, the dispersant comprises citric acid, sodium citrate.
Further, in step S1, the glass frit is B2O3-SiO2-ZnO-based glass powder.
Specifically, the B2O3-SiO2Proportion B of each component in-ZnO glass powder2O350 to 70 percent of SiO210 to 20 percent of ZnO and 20 to 40 percent of ZnO.
Further, in step S1, the organic vehicle includes an organic solvent and a thickener, the organic solvent includes one or a mixture of more of terpineol, butyl carbitol acetate and tributyl citrate, and the thickener includes one or a mixture of two of ethyl cellulose and nitrocellulose.
Further, the organic carrier also comprises an auxiliary agent, wherein the auxiliary agent comprises any one of lecithin or castor oil, and the auxiliary agent is used for adjusting the thixotropy and the dispersibility of the organic carrier.
Specifically, the organic solvent and the thickening agent are fully stirred and dissolved under the condition of heating to 80-90 ℃, and then the auxiliary agent is added, fully stirred and uniformly mixed to prepare the organic carrier.
Further, the proportion of the organic solvent, the thickening agent and the auxiliary agent is 70-80: 15-25: 1-5.
According to the high-conductivity conductive silver paste prepared by the preparation method, the high-conductivity conductive silver paste is subjected to screen printing, drying and sintering to obtain a conductive pattern, and the sheet resistance is tested to be less than 6.0m omega/□.
Compared with the prior art, the invention has the beneficial effects that:
1. silver pastes are respectively prepared through different silver powders, and then are stirred and mixed according to a proportion to form the high-conductivity conductive silver paste, so that the problem of uneven grinding and mixing caused by the fact that the silver powders pass through a three-roller mill simultaneously due to different particle sizes is avoided; meanwhile, the high-conductivity conductive silver paste is conveniently matched according to silver pastes with different contents, the mixing process is more convenient and quicker, and experimental exploration is facilitated.
2. The same dispersing system is adopted when the silver powders are prepared, so that the residual dispersing agent system on the surface of each silver powder is the same, surface modification is not needed in the mixing process, different silver powders can be uniformly mixed, the dispersing is uniform during mixing, and the nano silver powder is prevented from being agglomerated and sintered at first.
3. Through the mode of doping nanometer silver powder or slice silver powder in spherical silver powder, the doping of nanometer silver can fill up the space between the spherical silver powder, reduces the distance between the silver powder, increases the electric conductivity of silver thick liquid, and the surface effect of nanometer silver makes its fusing point be less than micron order spherical silver powder simultaneously, can make the sintering compacter as sintering auxiliary agent, and the area of contact between the silver powder also can be increased in the doping of slice silver powder, increases the electric conductivity of silver thick liquid.
4. The conductivity of the doped silver powder is better, the percolation threshold value is reduced, the proportion of the silver powder required by the silver paste to reach higher conductivity is reduced, and the production cost can be reduced.
5. The glass powder used is B2O3-SiO2The ZnO glass powder can be well matched with an AlN ceramic substrate, and the application range of the slurry is enlarged.
6. The prepared conductive silver paste has good printing performance and conductivity, and can be applied to the field of electronic functional materials.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
Example 1
The conductive silver paste is prepared according to the following mixture ratio:
average particle size of 1.0-3.0 μm, tap density>4g/cm3Spherical silver powder of (2): 55g of the total weight of the mixture;
average particle size 100-: 10g of a mixture;
B2O3-SiO2-ZnO glass frit: 5g, proportion of each component B in the glass powder2O360% of SiO215% and 25% ZnO;
organic carrier: 30 g.
Preparation of organic vehicle: adding 6g of ethyl cellulose into a mixture of 15g of terpineol and 8.5g of butyl carbitol under the heating condition, keeping the temperature at 80-90 ℃, fully stirring until the ethyl cellulose is completely dissolved, adding 0.5g of castor oil, fully stirring and uniformly mixing, wherein the ratio of the organic solvent, the thickening agent and the auxiliary agent is 78.3: 20: 1.7.
Preparing conductive silver paste: the two silver powders are respectively and fully mixed with glass powder and an organic carrier, and 55g of spherical silver powder, 4g of glass powder and 24.5g of organic carrier are mixed; 10g of nano silver powder, 1g of glass powder and 5.5g of organic carrier are mixed, then the mixture is ground to the fineness of less than 10 mu m by a three-roll mill respectively, the prepared conductive silver paste is stirred and mixed uniformly, namely, the functional phase silver paste and the doped silver paste are stirred and mixed uniformly according to the ratio of 83.5: 16.5, and a conductive pattern is obtained by screen printing, drying and sintering, so that the conductivity of a sample is tested.
Example 2
The conductive silver paste is prepared according to the following mixture ratio:
average particle size of 1.0-3.0 μm, tap density>4g/cm3Spherical silver powder of (2): 55g of the total weight of the mixture;
average particle size 100-: 10g of a mixture;
flake silver powder with average flake diameter of 1.0-2.0 μm and flake thickness of less than 100 nm: 5g of the total weight of the mixture;
B2O3-SiO2-ZnO glassPowder: 5g, proportion of each component B in the glass powder2O3Is 65% of SiO210% and 25% ZnO;
organic carrier: 25 g.
Preparation of organic vehicle: adding 6.25g of nitrocellulose into a mixture of 10.5g of terpineol and 7.25g of butyl carbitol under the heating condition, keeping the temperature at 80-90 ℃, fully stirring until the nitrocellulose is completely dissolved, then adding 0.5g of lecithin and 0.5g of castor oil, fully stirring and uniformly mixing, namely the ratio of the organic solvent, the thickening agent and the auxiliary agent is 71: 25: 4.
Preparing conductive silver paste: mixing silver powder, glass powder and organic carrier, and mixing 55g of spherical silver powder, 3.5g of glass powder and 21g of organic carrier; 10g of nano silver powder, 1g of glass powder and 2.5g of organic carrier are mixed; 5g of flake silver powder, 0.5g of glass powder and 1.5g of organic carrier are mixed, then the mixture is ground to the fineness of less than 10 mu m by a three-roll mill, the mixture is stirred and mixed uniformly, namely the nano-scale doped silver paste and the micron-scale flake doped silver paste are stirred and mixed uniformly according to the ratio of 79.5: 13.5: 7, the prepared conductive silver paste is subjected to screen printing, drying and sintering to obtain a conductive pattern, and the conductivity of a sample is tested.
Example 3
The conductive silver paste is prepared according to the following mixture ratio:
average particle size of 1.0-3.0 μm, tap density>4g/cm3Spherical silver powder of (2): 30g of the total weight of the mixture;
average particle size 100-: 15g of the total weight of the mixture;
flake silver powder with average flake diameter of 1.0-2.0 μm and flake thickness of less than 100 nm: 20g of the total weight of the mixture;
B2O3-SiO2-ZnO glass frit: 5g, proportion of each component B in the glass powder2O360% of SiO212% and 28% ZnO;
organic carrier: 30 g.
Preparation of organic vehicle: adding 6g of nitrocellulose into a mixture of 15g of tributyl citrate and 8g of butyl carbitol under the heating condition, keeping the temperature at 80-90 ℃, fully stirring until the nitrocellulose is completely dissolved, adding 0.5g of lecithin and 0.5g of castor oil, and fully stirring and uniformly mixing, namely the ratio of the organic solvent, the thickening agent and the auxiliary agent is 76.7: 20: 3.3.
Preparing conductive silver paste: mixing silver powder, glass powder and an organic carrier fully, and mixing 30g of spherical silver powder, 2.3g of glass powder and 13.5g of organic carrier; mixing 15g of nano silver powder, 1g of glass powder and 7g of organic carrier; 20g of flake silver powder, 1.7g of glass powder and 9.5g of organic carrier are mixed, then the mixture is ground to the fineness of less than 10 mu m by a three-roll mill respectively, the mixture is stirred and mixed uniformly, namely the nano-scale doped silver paste and the micron-scale flake doped silver paste are stirred and mixed uniformly according to the ratio of 45.8: 23: 31.2, the prepared conductive silver paste is subjected to silk-screen printing, drying and sintering to obtain a conductive pattern, and the conductivity of a sample is tested.
Example 4
The conductive silver paste is prepared according to the following mixture ratio:
average particle size of 1.0-3.0 μm, tap density>4g/cm3Spherical silver powder of (2): 35g of a soybean milk powder;
flake silver powder with average flake diameter of 1.0-2.0 μm and flake thickness of less than 100 nm: 30g of the total weight of the mixture;
B2O3-SiO2-ZnO glass frit: 5g, proportion of each component B in the glass powder2O357% of SiO215% and 28% ZnO;
organic carrier: 30 g.
Preparation of organic vehicle: adding 6g of ethyl cellulose into a mixture of 15g of terpineol and 8.5g of butyl carbitol acetate under the heating condition, keeping the temperature at 80-90 ℃, fully stirring until the ethyl cellulose is completely dissolved, continuously adding 0.5g of castor oil, fully stirring and uniformly mixing, namely the ratio of the organic solvent, the thickening agent and the auxiliary agent is 78.3: 20: 1.67.
Preparing conductive silver paste: mixing silver powder, glass powder and an organic carrier fully, and mixing 35g of spherical silver powder, 2.7g of glass powder and 16.5g of organic carrier; 30g of flake silver powder, 2.3g of glass powder and 13.5g of organic carrier are mixed, then the mixture is ground to the fineness of less than 10 mu m by a three-roll mill respectively, the prepared conductive silver paste is stirred and mixed uniformly, namely, the functional phase silver paste and the doped silver paste are stirred and mixed uniformly according to the ratio of 54.2: 45.8, and a conductive pattern is obtained by screen printing, drying and sintering, and the conductivity of a sample is tested.
The experimental comparison shows that: the following comparative example 1 is a conductive silver paste prepared without doping of the nano silver powder and the flake silver powder, and the conductivity of the conductive silver paste obtained in the comparative examples 1-2 is compared with that of the conductive silver paste obtained in the examples 1-4.
Comparative example 1
The conductive silver paste is prepared according to the following mixture ratio:
average particle size of 1.0-3.0 μm, tap density>4g/cm3Spherical silver powder of (2): 65g of the total weight of the mixture;
B2O3-SiO2-ZnO glass frit: 5g, proportion of each component B in the glass powder2O3Is 65% of SiO215% and 20% ZnO;
organic carrier: 30 g.
Preparation of organic vehicle: adding 6g of ethyl cellulose into a mixture of 15g of terpineol and 8.5g of butyl carbitol under the heating condition, keeping the temperature at 80-90 ℃, fully stirring until the ethyl cellulose is completely dissolved, adding 0.5g of castor oil, fully stirring and uniformly mixing.
Preparing conductive silver paste: and fully mixing the silver powder, the glass powder and the organic carrier, then grinding the mixture by a three-roll mill until the fineness is less than 10 mu m, obtaining a conductive pattern by screen printing, drying and sintering the prepared conductive silver paste, and testing the conductivity of the sample.
Comparative example 2
The conductive silver paste is prepared according to the following mixture ratio:
average particle size of 1.0-3.0 μm, tap density>4g/cm3Spherical silver powder of (2): 35g of a soybean milk powder;
average particle size 100-: 15g of the total weight of the mixture;
flake silver powder with average flake diameter of 1.0-2.0 μm and flake thickness of less than 100 nm: 15g of the total weight of the mixture;
B2O3-SiO2-ZnO glass frit: 5g, proportion of each component B in the glass powder2O360% of SiO215% and 25% ZnO;
organic carrier: 30 g.
Preparation of organic vehicle: adding 6g of ethyl cellulose into a mixture of 15g of terpineol and 8.5g of butyl carbitol acetate under the heating condition, keeping the temperature at 80-90 ℃, fully stirring until the ethyl cellulose is completely dissolved, continuously adding 0.5g of castor oil, fully stirring and uniformly mixing.
Preparing conductive silver paste: and fully mixing the silver powder, the glass powder and the organic carrier, then grinding the mixture by a three-roll mill until the fineness is less than 10 mu m, obtaining a conductive pattern by screen printing, drying and sintering the prepared conductive silver paste, and testing the conductivity of the sample.
TABLE 1
As can be seen from the above examples and comparative examples, the conductive paste prepared by the method of the present invention has a small sheet resistance and a good conductivity.
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