CN115365494A - Preparation method of silver-coated copper powder and application of silver-coated copper powder in conductive paste - Google Patents

Preparation method of silver-coated copper powder and application of silver-coated copper powder in conductive paste Download PDF

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CN115365494A
CN115365494A CN202211111459.XA CN202211111459A CN115365494A CN 115365494 A CN115365494 A CN 115365494A CN 202211111459 A CN202211111459 A CN 202211111459A CN 115365494 A CN115365494 A CN 115365494A
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copper powder
silver
solution
coated copper
mixing
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CN115365494B (en
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颜志勇
胡英
王晓馨
姚勇波
于利超
易洪雷
张葵花
李喆
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Jiaxing University
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Jiaxing University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/17—Metallic particles coated with metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/102—Metallic powder coated with organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/105—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing inorganic lubricating or binding agents, e.g. metal salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/107—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing organic material comprising solvents, e.g. for slip casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • B22F1/145—Chemical treatment, e.g. passivation or decarburisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
    • C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
    • C23C18/1827—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment only one step pretreatment
    • C23C18/1834—Use of organic or inorganic compounds other than metals, e.g. activation, sensitisation with polymers
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/42—Coating with noble metals
    • C23C18/44—Coating with noble metals using reducing agents
    • 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

Abstract

The invention relates to a preparation method of silver-coated copper powder and application of the silver-coated copper powder in conductive paste. The method comprises the steps of adopting lysozyme as a pre-protection layer of the copper powder to prevent the copper powder from being oxidized, then adopting the lysozyme as a transition layer to reduce silver ions on the surface of the lysozyme in situ to form an even silver shell layer, and then carrying out low-temperature heating treatment to prepare the silver-coated copper powder. The invention also provides application of the silver-coated copper powder in conductive paste, the conductive paste prepared by mixing the silver-coated copper powder with an organic carrier, an inorganic binder and a sintering inhibitor has good compactness and oxidation resistance after sintering and curing, and also has good conductivity, the resistivity is as low as 1.3 multiplied by 10 ‑5 Ω·cm。

Description

Preparation method of silver-coated copper powder and application of silver-coated copper powder in conductive paste
Technical Field
The invention relates to a preparation method of conductive paste, in particular to a preparation method of silver-coated copper powder and application of the silver-coated copper powder in the conductive paste.
Background
At present, in the field of electronic industry, the amount of silver powder is increasing continuously, and in order to reduce cost, people expect to develop conductive powder with low cost and high conductivity, wherein silver-coated copper powder is considered as an ideal substitute product of silver powder, because copper powder is low in price and is expected to reduce 30% -50% of silver paste cost, the conductivity is close to that of silver, but the silver coating layer on the surface of the copper powder in the prior art is often deposited incompactly and unevenly, the surface of the inner layer of copper powder is partially exposed, the exposed copper powder is more easily oxidized, and the combination of silver and copper is not firm and is easy to fall off during high-temperature sintering, so that the conductivity of the silver-coated copper powder is poor.
Lysozyme is a natural antibacterial protein, widely exists in plant juice, animal secretion, tears, saliva, milk, poultry eggs and partial bacteria, can enable contents with broken cell walls to escape to dissolve the bacteria, can be directly combined with virus proteins with negative charges to form double salts with DNA, RNA and apoprotein, and can inactivate the viruses, so that lysozyme is mostly applied to the fields of antibiosis, antiphlogosis, antivirus and the like. The lysozyme contains a plurality of functional groups such as carboxyl, hydroxyl, amino, thiol and the like, and a disulfide bond in the lysozyme structure can be opened by a reducing agent tris (2-carbonylethyl) phosphate (TCEP), so that the configuration of the lysozyme is changed, and a stable and uniform phase-change lysozyme nano-film is formed on the surface of a carrier.
However, in the prior art, no report is made that lysozyme is used as a pre-protection layer of the copper powder, and then lysozyme is used as a transition layer to reduce silver ions on the surface of the copper powder to form a uniform silver shell layer. The invention provides a preparation method of silver-coated copper powder, which can solve the problems of poor compactness, uniformity and conductivity of the silver-coated copper powder in the prior art.
Disclosure of Invention
In order to solve the technical problems that compactness and uniformity of a silver shell layer in the silver-coated copper powder are poor and conductivity of the silver-coated copper powder needs to be improved continuously in the prior art, the invention provides a preparation method of the silver-coated copper powder. In addition, the invention also provides application of the silver-coated copper powder in conductive paste, the conductive paste prepared by mixing the silver-coated copper powder with an organic carrier, an inorganic binder and a sintering inhibitor has good conductivity after sintering and curing, and the resistivity is as low as 1.3 multiplied by 10 -5 Ω·cm。
For clearly illustrating the preparation method of the silver-coated copper powder, the preparation of the silver-coated copper powder is carried out according to the following steps:
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 30-55mmol/L of tri (2-carboxyethyl) phosphine, and adjusting the pH value to 4.5-6.5 by using sodium hydroxide to obtain solution A; weighing lysozyme powder, adding the lysozyme powder into N-2-hydroxyethyl piperazine-N '-2-ethanesulfonic acid buffer solution to prepare N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 5-15mg/mL lysozyme, and adjusting the pH value to 6.5-7.0 by using sodium hydroxide to obtain solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C;
2) Weighing copper powder, uniformly mixing the copper powder with the solution C, standing at room temperature, forming a pre-protective film on the surface of the copper powder, and then centrifuging, washing with deionized water and drying to obtain pretreated copper powder;
3) Uniformly stirring and mixing the silver-ammonia solution, the sodium citrate solution and the polyvinylpyrrolidone solution at room temperature to obtain a silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding a vitamin C solution in batches, mixing for 2-4 times, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
In the step 1), the molecular weight of the lysozyme is 14.4kDa, and the activity of the lysozyme is 30000-70000U/mg, preferably 40000-50000U/mg; the lysozyme is preferably egg white lysozyme, and the lysozyme is purchased from maclin reagent net.
Optionally, the copper powder is at least one of spherical copper powder, sphere-like copper powder, flake copper powder, rod copper powder and dendritic copper powder; wherein the content of the first and second substances,
the median diameter D of the spherical copper powder 50 =1-2 μm or 500nm, median diameter D of the flake copper powder 50 =0.5-3 μm, average thickness 0.1-0.2 μm; and D 50 Spherical copper powder of =1-2 μm in 60-100wt.% of said copper powder, D 50 Spherical copper powder with the particle size of 500nm and the median diameter of D 50 Flake copper powder with the average thickness of 0.1-0.2 μm and the average thickness of 0.5-3 μm respectively accounts for 10-40 wt% of the copper powder; and the tap density of the spherical copper powder is 4.5-5.5g/cm 3 The tap density of the flake copper powder is 4.5-6.0g/cm 3 The sphere-like copper powder, the rod-like copper powder and the treeThe tap density of the dendritic copper powder is 4.5-6.0g/cm 3 。
According to the invention, by adjusting the grading proportion of the copper powder, different kinds of copper powder can be mixed, and when the copper powder is applied to conductive paste sintering, copper powder particles can be mutually engaged, so that the sintering compactness is enhanced, the sintering yield of products is improved, and the conductivity of the sintered material is enhanced.
Further optionally, the mass-volume ratio of the copper powder to the solution C is 0.1-1g; preferably, the mass volume ratio of the copper powder to the solution C is 0.5-1g:100-200mL to ensure that lysozyme can form a uniform and compact protective film on the surface of the copper powder; and the solution C is wasted due to too much addition amount, and the copper powder cannot be effectively coated due to too little addition amount.
In addition, the pretreated copper powder is formed by forming a layer of lysozyme nano film with the thickness of 3-5nm on the surface of the copper powder.
It is noted that 4 pairs of disulfide bonds in the lysozyme structure maintain the configuration of lysozyme, and the reducing agent tris (2-carbonyl ethyl) phosphorus acts on the disulfide bonds to cause the configuration of lysozyme to be changed, so that a stable and uniform phase-change lysozyme nano-film is formed on the surface of copper powder. This phase transition lysozyme nanometer film can be at the inseparable protective layer of copper powder surface adhesion formation, avoids the copper powder to take place the oxidation, has effectively solved the problem that copper powder is oxidized or is corroded in preparation silver-clad copper powder in-process to can improve silver-clad copper powder's electric conductivity.
The lysozyme contains a plurality of functional groups such as carboxyl, hydroxyl, amino, thiol and the like, on one hand, the functional groups such as the carboxyl and the hydroxyl can chelate silver ions to ensure that silver particles are stably adsorbed on the surface layer of the lysozyme, on the other hand, the thiol functional group can form Ag-S bonding action with the silver ions to firmly combine silver salts on the surface of the lysozyme and form a compact silver coating layer on the surface of copper powder.
Optionally, the preparation method of the silver ammonia solution comprises the following steps: dispersing silver nitrate in water to obtain a silver nitrate solution with the mass fraction of 5wt.%, then adding ammonia water with the mass fraction of 16-25wt.%, and uniformly stirring and mixing until the mixture is clarified to obtain a silver ammonia solution;
the silver-ammonia solution dispersion liquid contains 1-3wt.% of silver-ammonia solution, 0.1-0.5wt.% of sodium citrate solution, 0.1-1wt.% of polyvinylpyrrolidone solution and 1-5wt.% of vitamin C solution; further, the mass ratio of silver nitrate, sodium citrate, polyvinylpyrrolidone and vitamin C in each 120mL of water in the silver-ammonia solution dispersion liquid is 1-2.0:0.2-0.5:0.2-0.8:2.0-5.0.
Wherein the solvents in the sodium citrate solution, the polyvinylpyrrolidone solution and the vitamin C solution are absolute ethyl alcohol or deionized water, preferably deionized water.
The sodium citrate is a short molecular chain dispersing agent and plays a role in dispersing to generate nano silver particles; the polyvinylpyrrolidone is a long molecular chain dispersant and is matched with sodium citrate for use, so that uniform and compact nano silver-coated copper powder particles are generated in a better dispersing mode. The vitamin C is a reducing agent and is used for reducing silver ions in silver nitrate.
Optionally, the mass-to-volume ratio of the pretreated copper powder to the silver-ammonia solution dispersion is 1-50mg:100-300mL, and mixing in an acoustic resonance mixing device for 5-10min to fully disperse the copper powder in the silver-ammonia solution dispersion liquid.
And the vitamin C solution is added into the acoustic resonance mixing equipment in three times by the same volume, and the mixing is carried out for 5-10min after each addition, so that the silver powder is fully reduced by the vitamin C.
It should be noted that the acoustic resonance mixing technology is a whole-field mixing technology, and the acoustic resonance mixing technology is a novel mixing technology based on vibration macro-mixing and acoustic flow micro-mixing coupling effects, not only can realize whole-field uniform dispersion of the mixed material through bulk mixing and micro-mixing, but also can avoid physical damage to the mixed material caused by shearing of blades or friction collision with walls, and because the mixing mode uses low-frequency acoustic flow, no violent thermal effect occurs. Compared with the traditional impeller type mixing, the acoustic resonance mixing technology has the advantages of no intrusive blade stimulation, high mixing speed, good mixing uniformity, easy cleaning of a container, capability of realizing in-situ mixing and the like, and can be used for mixing solid-solid, solid-liquid, liquid-liquid and liquid-gas. The invention adopts acoustic resonance mixing equipment and equipment with the model number of G2000 sold by Waideblue Bokejiu (Shenzhen) Limited company.
Furthermore, the grain diameter of the silver powder on the surface of the pretreated copper powder is 0.5-2.0 mu m, and the specific surface area is 0.5-7 m 2 (ii)/g; the particle size of the silver-coated copper powder is 0.6-5.2 mu m, and the specific surface area is 0.4-6 m 2 (ii)/g; and preserving the heat of the primary silver-coated copper powder in a vacuum oven at 45 ℃ for 30min to obtain the silver-coated copper powder.
The invention also claims application of the silver-coated copper powder prepared by the method in conductive paste.
The conductive paste comprises the following components in percentage by mass:
55-85% of silver-coated copper powder, 15-45% of organic carrier, 2-10% of inorganic binder and 0.5-2% of sintering inhibitor;
wherein the organic carrier is prepared from organic resin, an organic solvent, a dispersing agent and a defoaming agent according to the mass percentage of 10-40%:60-85%:0.1-1.0%:0.1-1.0 percent;
the method for preparing the silver-coated copper powder conductive paste specifically comprises the following steps:
s1: respectively weighing the organic resin, the organic solvent, the dispersant and the defoamer according to the mass percent, and ultrasonically stirring and uniformly mixing until the organic resin, the organic solvent, the dispersant and the defoamer are completely dissolved to obtain an organic carrier;
s2: and uniformly mixing the silver-coated copper powder, the inorganic binder and the sintering inhibitor, then mixing the mixture with the organic carrier prepared in the step S1, dispersing, rolling for 3-5 times, and filtering by using a filter screen with the diameter of 2-6 mu m to obtain the silver-coated copper powder conductive slurry.
Optionally, the mass percentage of the silver-coated copper powder in the conductive paste is 65-80wt.%; in the sintering process of the conductive paste, when the temperature exceeds 200 ℃, lysozyme in the silver-coated copper powder is thermally decomposed, so that the silver-coated copper powder is bonded more compactly;
the mass percentage of the organic carrier in the conductive paste is 20-40wt.%. The organic carrier is used for adjusting the viscosity of the conductive paste and regulating and controlling the shrinkage rate of the conductive paste during drying and sintering, so that better sintering adhesion between the conductive paste and the carrier is obtained.
Optionally, the organic resin is a polypyrrolidone, an epoxy resin, a phenolic resin, an acrylic, a urethane, a silicone, a polyalkylene carbonate, a polyvinyl acetal, or a cellulose; preferably the organic resin is selected from polyvinyl formal, polyacrylate, polyvinyl alcohol, polyvinyl pyrrolidone or carboxyethyl cellulose;
the organic solvent is ethanol, alpha-terpineol, diethylene glycol butyl ether, tributyl citrate, diethylene glycol butyl ether acetate, alcohol ester dodeca, dimethyl succinate or dimethyl glutarate;
the dispersant is at least one of polyethylene glycol, polyacrylic acid (PAA-800-PAA-5000), polyvinyl alcohol, myristyl alcohol, dodecylamine, oleylamine, castor oil, octyl mercaptan and dodecyl mercaptan;
the defoaming agent is tributyl phosphate or polyether defoaming agent GPE-3000.
Optionally, the inorganic binder is glass powder, the softening point of the glass powder is 250-350 ℃, and the content of each component of the inorganic binder is as follows by mol percent:
V 2 O 5 45-55wt.％，P 2 O 5 5-15wt.％，Al 2 O 3 3-8wt.％，TeO 2 20-35wt.％，SiO 2 2-7wt.％，ZnO3-10wt.％，Bi 2 O 3 2-6wt.%; v in the inorganic binder 2 O 5 Has the function of effectively reducing the melting temperature of the glass powder, al 2 O 3 The glass powder has the advantages of improving the stability and toughness of the glass powder and reducing the problem of different thermal expansion coefficients during sintering, and Bi 2 O 3 The function of making the contact surface of Ag and Si in the conductive paste more continuous and reducing the softening point and the packaging temperature is achieved, and SiO 2 、P 2 O 5 Acting as a network former, siO 2 ZnO prevents the conductive paste from being excessively sintered, and improves the contact between the silver-coated copper powder particles and the surface of a semiconductor;
the sintering inhibitor is graphite alkyne, and has the function of preventing the shrinkage effect between the semiconductor and the conductive paste in the sintering process, so that the contact resistance is reduced, the microcracks generated at the contact sites of the conductive paste and the semiconductor are reduced, and the conductive capacity and the sintering conversion factor are improved. The semiconductor can be silicon, silicon carbide; the graphdine is purchased from pioneer nano-scale, and the product model is XFY01. The graphdiyne is a high-temperature resistant material, can keep a stable crystal structure at high temperature, and can avoid sintering failure caused by overhigh sintering temperature.
Based on the above, compared with the prior art, the preparation method of the silver-coated copper powder and the application of the silver-coated copper powder in the conductive paste provided by the invention have the following advantages:
(1) The invention provides a preparation method of silver-coated copper powder, which comprises the steps of adopting lysozyme as a pre-protection layer of the copper powder to effectively isolate oxygen and prevent the copper powder from being oxidized, reducing silver ions on the surface of the copper powder in situ by using the lysozyme as a transition layer to form a uniform silver shell layer, and then carrying out low-temperature heating treatment to prepare the silver-coated copper powder. The molecular structure of the lysozyme contains a plurality of functional groups such as carboxyl, hydroxyl, amino, thiol and the like, on one hand, the functional groups such as the carboxyl and the hydroxyl can chelate silver ions to ensure that silver particles are stably adsorbed on the surface layer of the lysozyme, on the other hand, the thiol functional group can form Ag-S bonding action with the silver ions to firmly combine the silver salt on the surface of the lysozyme and form a compact silver coating layer on the surface of copper powder;
(2) The invention also provides application of the silver-coated copper powder in conductive paste, and the conductive paste prepared by mixing the silver-coated copper powder with an organic carrier, an inorganic binder and a sintering inhibitor has good conductivity after sintering and curing and has the resistivity as low as 1.3 multiplied by 10 -5 Omega cm. The silver-coated copper powder with different particle sizes, which is prepared by selecting copper powder with different particle sizes, is used for adjusting reasonable powder gradation, improving the sintering compactness and the sintered product yield and enhancing the conductivity of the sintered material; the high-temperature resistant material graphite alkyne is innovatively used as a sintering inhibitor, so that the contact resistance can be reduced, microcracks generated at contact sites of the conductive slurry and a semiconductor can be reduced, and the conductive capability can be improved; the above-mentionedThe organic carrier and the inorganic binder can adjust the viscosity of the conductive paste, regulate and control the shrinkage rate of the conductive paste during drying and sintering, ensure better sintering adhesion between the conductive paste and the carrier, and improve the contact between the silver-coated copper powder particles and the surface of a semiconductor.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the 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 derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The water used in the present invention is deionized water unless otherwise specified. The reagents are all commercially available reagents unless otherwise specified.
The invention will now be further illustrated, but is not limited, by the following specific examples.
Example 1
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 40mmol/L tris (2-carboxyethyl) phosphine, and adjusting the pH to 6.3 by using sodium hydroxide to obtain solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the lysozyme concentration of 12mg/mL and the lysozyme activity of 40000U/mg, adjusting the pH value to 6.5 by using sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C;
2) Weighing a certain amount of copper powder, uniformly mixing the copper powder with the solution C according to a mass-volume ratio of 1g to 250mL, standing at room temperature for 60min to form a pre-protective film on the surface of the copper powder, and centrifuging, washing with deionized water and drying to obtain pre-treated copper powder;
the copper powder is D 50 Spherical copper powder of =1 to 2 μm, said D 50 Spherical copper powder with the particle size of 1-2 μm accounts for 100% of the total mass of the copper powder.
3) Stirring and uniformly mixing 3wt.% of silver-ammonia solution, 0.5wt.% of sodium citrate solution and 0.8wt.% of polyvinylpyrrolidone solution at room temperature according to a certain mass ratio to obtain silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, then adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding 5wt.% vitamin C solution with the same volume for three times, mixing for the 4 th time, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein the silver ammonia solution dispersion comprises silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C accounts for 1.5g:0.4g:0.6g:4.0g; the mass-to-volume ratio of the pretreated copper powder to the 3wt.% silver-ammonia solution dispersion is 50mg:250mL, and 10min for the first mixing and the subsequent three mixing in an acoustic resonance mixing device.
Example 2
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 45mmol/L tris (2-carboxyethyl) phosphine, and adjusting the pH to 6.0 by using sodium hydroxide to obtain solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with lysozyme concentration of 15mg/mL and lysozyme activity of 40000U/mg, adjusting the pH value to 6.5 by using sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C;
2) Weighing a certain amount of copper powder, uniformly mixing the copper powder with the solution C according to the mass volume ratio of 1g to 200mL, standing at room temperature for 90min to form a pre-protection film on the surface of the copper powder, and centrifuging, washing with deionized water and drying to obtain pre-treated copper powder;
the copper powder is D 50 Spherical copper powder of =1-2 μm and D 50 Flake copper powder with an average thickness of 0.1-0.2 μm and a particle size of 0.5-3 μm, wherein D is 50 Spherical copper powder with the particle size of 1-2 μm accounts for 60% of the total mass of the copper powder, and D 50 Flake copper powder with the average thickness of 0.1-0.2 μm and the average thickness of 0.5-3 μm accounts for 40% of the total mass of the copper powder.
3) Stirring and uniformly mixing 2.5wt.% of silver-ammonia solution, 0.5wt.% of sodium citrate solution and 1.0wt.% of polyvinylpyrrolidone solution at room temperature according to a certain mass ratio to obtain silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, then adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding 5wt.% vitamin C solution with the same volume for three times, mixing for 3 times, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein the silver ammonia solution dispersion comprises silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C accounts for 2.0g by mass: 0.5g:0.8g:5.0g; the mass-to-volume ratio of the pretreated copper powder to the 2.5wt.% silver-ammonia solution dispersion is 50mg:200mL, and the time for mixing for the first time and the subsequent three times in an acoustic resonance mixing device is 8min.
Comparative example 1
Comparative example 1 differs from example 2 in that the copper powder was not lysozyme coated and the other operating steps were the same as in example 2. The specific procedure of comparative example 1 was as follows:
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 45mmol/L tris (2-carboxyethyl) phosphine, and adjusting the pH to 6.0 by using sodium hydroxide to obtain solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the lysozyme concentration of 15mg/mL and the lysozyme activity of 40000U/mg, adjusting the pH value to 6.5 by using sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C;
2) Weighing 1g of copper powder, wherein the copper powder is D 50 Spherical copper powder of =1-2 μm and D 50 Flake copper powder with an average thickness of 0.1-0.2 μm and a particle size of 0.5-3 μm, wherein D is 50 Spherical copper powder of =1-2 μm accounts for 60% of the total mass of the copper powder, and the D 50 Flake copper powder with the average thickness of 0.1-0.2 μm and the average thickness of 0.5-3 μm accounts for 40% of the total mass of the copper powder;
3) Stirring and uniformly mixing 2.5wt.% of silver-ammonia solution, 0.5wt.% of sodium citrate solution and 1.0wt.% of polyvinylpyrrolidone solution at room temperature according to a certain mass ratio to obtain silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, then adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding 5wt.% vitamin C solution with the same volume for three times, mixing for 3 times, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein the silver ammonia solution dispersion comprises silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C accounts for 2.0g by mass: 0.5g:0.8g:5.0g; the mass-to-volume ratio of the pretreated copper powder to the 2.5wt.% silver-ammonia solution dispersion is 50mg:200mL, and the time for mixing for the first time and the three subsequent times in an acoustic resonance mixing device is 8min.
Example 3
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 30mmol/L tris (2-carboxyethyl) phosphine, and adjusting the pH to 5.0 by using sodium hydroxide to obtain solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with 10mg/mL of lysozyme concentration and 30000U/mg of lysozyme activity, adjusting the pH value to 6.5 by using sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C;
2) Weighing a certain amount of copper powder, uniformly mixing the copper powder with the solution C according to the mass volume ratio of 0.8g to 200mL, standing at room temperature for 45min to form a pre-protection film on the surface of the copper powder, and performing centrifugation, deionized water washing and drying to obtain pretreated copper powder;
the copper powder is D 50 =1-2 μm and D 50 Spherical copper powder of =500nm, said D 50 Spherical copper powder of =1-2 mu m accounting for 70% of the total mass of the copper powder, and the D 50 Spherical copper powder with the particle size of 500nm accounts for 30 percent of the total mass of the copper powder.
3) Stirring and uniformly mixing 2.0wt.% of silver-ammonia solution, 0.3wt.% of sodium citrate solution and 0.5wt.% of polyvinylpyrrolidone solution at room temperature according to a certain mass ratio to obtain silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, then adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding 4wt.% vitamin C solution with the same volume for three times, mixing for 3 times, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein the silver nitrate in each 120mL of water in the silver ammonia solution dispersion solution is: sodium citrate: polyvinylpyrrolidone: the vitamin C accounts for 1.5g:0.4g:0.7g:3.0g; the mass-to-volume ratio of the pretreated copper powder to the 2.0wt.% silver-ammonia solution dispersion was 30mg:250mL, and the time for mixing for the first time and the three subsequent times in the acoustic resonance mixing device is 9min.
Example 4
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 35mmol/L tris (2-carboxyethyl) phosphine, and adjusting the pH to 4.5 by using sodium hydroxide to obtain solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the lysozyme concentration of 12mg/mL and the lysozyme activity of 50000U/mg, adjusting the pH value to 7.0 by using sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C;
2) Weighing a certain amount of copper powder, uniformly mixing the copper powder with the solution C according to the mass volume ratio of 1g to 220mL, standing at room temperature for 50min to form a pre-protective film on the surface of the copper powder, and centrifuging, washing with deionized water and drying to obtain pre-treated copper powder;
the copper powder is D 50 Spherical copper powder of =1-2 μm, D 50 Spherical copper powder of =500nm and D 50 Flake copper powder with an average thickness of 0.1-0.2 μm and a particle size of 0.5-3 μm, wherein D is 50 Spherical copper powder with the particle size of 1-2 μm accounts for 60% of the total mass of the copper powder, and D 50 Spherical copper powder of =500nm in an amount of 25% by mass of the total copper powder, and D 50 Flake copper powder with the average thickness of 0.1-0.2 μm and the thickness of 0.5-3 μm accounts for 15% of the total mass of the copper powder.
3) Stirring and uniformly mixing 3.0wt.% of silver-ammonia solution, 0.5wt.% of sodium citrate solution and 1.0wt.% of polyvinylpyrrolidone solution at room temperature according to a certain mass ratio to obtain silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid in an acoustic resonance mixing device, then adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding a vitamin C solution with the same volume of 4.5wt.% for three times, mixing for 3 times, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein the silver ammonia solution dispersion comprises silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C is prepared from 2.0g:0.5g:0.6g:5.0g; the mass-to-volume ratio of the pretreated copper powder to the 3.0wt.% silver-ammonia solution dispersion is 40mg:250mL, and the time for mixing for the first time and the three subsequent times in an acoustic resonance mixing device is 7min.
Example 5
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 30mmol/L tris (2-carboxyethyl) phosphine, and adjusting the pH to 5.0 by using sodium hydroxide to obtain solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the lysozyme concentration of 10mg/mL and the lysozyme activity of 60000U/mg, adjusting the pH value to 6.8 by using sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C; weighing a certain amount of copper powder, uniformly mixing the copper powder with the solution C according to a mass-volume ratio of 1g to 240mL, standing at room temperature for 30min to form a pre-protection film on the surface of the copper powder, and centrifuging, washing with deionized water and drying to obtain pre-treated copper powder;
2) The copper powder is D 50 Spherical copper powder of =1-2 μm, D 50 Spherical copper powder of =500nm and D 50 Flake copper powder with average thickness of 0.1-0.2 μm and =0.5-3 μm, wherein D is 50 Spherical copper powder of =1-2 μm accounts for 70% of the total mass of the copper powder, and the D 50 Spherical copper powder of =500nm in an amount of 15% by mass of the total copper powder, and D 50 Flake copper powder with the average thickness of 0.1-0.2 μm and the weight ratio of 0.5-3 μm to 15％。
3) Stirring and uniformly mixing 1.0wt.% of silver-ammonia solution, 0.2wt.% of sodium citrate solution and 0.1wt.% of polyvinylpyrrolidone solution at room temperature according to a certain mass ratio to obtain silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, then adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding 4.5wt.% vitamin C solution with the same volume for three times, mixing for 3 times, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein the silver ammonia solution dispersion comprises silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C accounts for 1.0g:0.3g:0.2g:3.0g; the mass-to-volume ratio of the pretreated copper powder to the 1.0wt.% silver-ammonia solution dispersion was 40mg:200mL, and 5min for the first mixing and the subsequent three mixing in the acoustic resonance mixing device.
The following examples 6 to 13 are processes for preparing conductive pastes.
Example 6
The preparation method of the conductive paste comprises the following steps:
s1: weighing 20.5g of epoxy resin E44, 78g of alpha-terpineol, 1g of polyethylene glycol (PEG 4000) and 0.5g of tributyl phosphate, and uniformly mixing by ultrasonic stirring until the epoxy resin E44, the alpha-terpineol, the polyethylene glycol and the tributyl phosphate are completely dissolved to obtain an organic carrier;
s2: and (3) uniformly mixing 78.5g of the silver-coated copper powder prepared in the example 1, 5g of the inorganic binder and 0.5g of the graphdiyne, mixing with 16g of the organic carrier prepared in the step S1, dispersing, rolling for 5 times, and filtering by using a filter screen with the diameter of 5 microns to obtain the silver-coated copper powder conductive paste.
The inorganic binder consists of V 2 O 5 48wt.％，P 2 O 5 7wt.％，Al 2 O 3 6wt.％，TeO 2 22wt.％，SiO 2 4wt.％，ZnO8wt.％，Bi 2 O 3 5wt.% of the components are mixed according to the proportion.
Example 7
The preparation method of the conductive paste comprises the following steps:
s1: weighing 20.5g of epoxy resin E44, 78g of alpha-terpineol, 1g of polyethylene glycol (PEG 4000) and 0.5g of tributyl phosphate, and uniformly mixing by ultrasonic stirring until the epoxy resin E44, the alpha-terpineol, the polyethylene glycol and the tributyl phosphate are completely dissolved to obtain an organic carrier;
s2: and (3) uniformly mixing 78.5g of the silver-coated copper powder prepared in the example 2, 5g of the inorganic binder and 0.5g of the graphdiyne, mixing with 16g of the organic carrier prepared in the step S1, dispersing, rolling for 5 times, and filtering by using a filter screen with the diameter of 5 microns to obtain the silver-coated copper powder conductive slurry.
The inorganic binder consists of V 2 O 5 48wt.％，P 2 O 5 7wt.％，Al 2 O 3 6wt.％，TeO 2 22wt.％，SiO 2 4wt.％，ZnO8wt.％，Bi 2 O 3 5wt.% of the components are mixed according to the proportion.
Example 8
The preparation method of the conductive paste comprises the following steps:
s1: weighing 20.5g of epoxy resin E44, 78g of alpha-terpineol, 1g of polyethylene glycol (PEG 4000) and 0.5g of tributyl phosphate, and uniformly mixing by ultrasonic stirring until the epoxy resin E44, the alpha-terpineol, the polyethylene glycol and the tributyl phosphate are completely dissolved to obtain an organic carrier;
s2: and (3) uniformly mixing 78.5g of the silver-coated copper powder prepared in the embodiment 4, 5g of the inorganic binder and 0.5g of the graphdiyne, mixing with 16g of the organic carrier prepared in the step S1, dispersing, rolling for 5 times, and filtering by using a filter screen with the diameter of 5 microns to obtain the silver-coated copper powder conductive paste.
The inorganic binder consists of V 2 O 5 48wt.％，P 2 O 5 7wt.％，Al 2 O 3 6wt.％，TeO 2 22wt.％，SiO 2 4wt.％，ZnO8wt.％，Bi 2 O 3 5wt.% of the components are mixed according to the proportion.
Example 9
The preparation method of the conductive paste comprises the following steps:
s1: weighing 25g of polyvinyl formal, 73g of diethylene glycol monobutyl ether, 1g of polyacrylic acid (PAA-800) and 1.0g of tributyl phosphate, and ultrasonically stirring and uniformly mixing until the polyvinyl formal, the diethylene glycol monobutyl ether, the polyacrylic acid (PAA-800) and the tributyl phosphate are completely dissolved to obtain an organic carrier;
s2: and (3) uniformly mixing 70g of the silver-coated copper powder prepared in the embodiment 4, 6g of the inorganic binder and 1.0g of the graphite alkyne, mixing 23g of the silver-coated copper powder with the organic carrier prepared in the step S1, dispersing, rolling for 4 times, and filtering by using a filter screen with the diameter of 6 microns to obtain the silver-coated copper powder conductive paste.
The inorganic binder consists of V 2 O 5 50wt.％，P 2 O 5 5wt.％，Al 2 O 3 8wt.％，TeO 2 20wt.％，SiO 2 4wt.％，ZnO9wt.％，Bi 2 O 3 4wt.% of the components are mixed according to the proportion.
Example 10
The preparation method of the conductive paste comprises the following steps:
s1: weighing 30g of polyvinyl alcohol (PVA-0588), 69g of diethylene glycol butyl ether acetate, 0.5g of myristyl alcohol and 0.5g of polyether defoamer GPE-3000, and uniformly mixing by ultrasonic stirring until the polyvinyl alcohol, the diethylene glycol butyl ether acetate and the polyether defoamer are completely dissolved to obtain an organic carrier;
s2: 69g of the silver-coated copper powder prepared in the embodiment 4, 8g of the inorganic binder and 1.5g of the graphdine are uniformly mixed, then the mixture is mixed with 21.5g of the organic carrier prepared in the S1, and the mixture is dispersed, rolled for 3 times and filtered by a filter screen with the diameter of 4 mu m to obtain the silver-coated copper powder conductive slurry.
The inorganic binder consists of V 2 O 5 45wt.％，P 2 O 5 7wt.％，Al 2 O 3 6wt.％，TeO 2 25wt.％，SiO 2 4wt.％，ZnO9wt.％，Bi 2 O 3 4wt.% of the components are mixed according to the proportion.
Example 11
The preparation method of the conductive paste comprises the following steps:
s1: weighing 30g of polyvinyl formal, 69g of dimethyl succinate, 0.5g of octyl mercaptan and 0.5g of tributyl phosphate, and uniformly mixing by ultrasonic stirring until the polyvinyl formal, the dimethyl succinate and the octyl mercaptan are completely dissolved to obtain an organic carrier;
s2: and (3) uniformly mixing 80g of the silver-coated copper powder prepared in the embodiment 4, 2g of the inorganic binder and 2.0g of the graphdine, mixing 16g of the mixture with the organic carrier prepared in the step S1, dispersing, rolling for 5 times, and filtering by using a filter screen with the diameter of 5 microns to obtain the silver-coated copper powder conductive slurry.
The inorganic binder consists of V 2 O 5 45wt.％，P 2 O 5 7wt.％，Al 2 O 3 6wt.％，TeO 2 25wt.％，SiO 2 4wt.％，ZnO9wt.％，Bi 2 O 3 4wt.% of the components are mixed according to the proportion.
The conductive paste prepared above was sintered and cured at 500 ℃ under nitrogen protection, and the resistivity values were measured as shown in table 1.
Comparative example 2
Comparative example 2 differs from example 8 in that the silver-coated copper powder was a commercially available product from Yinfeng Metal technology, inc. (China), guangzhou, having a product type YF-1705 and a tap density of 4.5-4.9g/cm 3 The other steps of the spherical powder of (3) were the same as in example 8.
Comparative example 3
Comparative example 3 compared to example 7, the silver-coated copper powder used was devoid of lysozyme encapsulation and the other steps were the same as in example 7. The preparation method of the conductive paste in the comparative example 3 is prepared by the following steps:
s1: weighing 20.5g of epoxy resin E44, 78g of alpha-terpineol, 1g of polyethylene glycol (PEG 4000) and 0.5g of tributyl phosphate, and uniformly mixing by ultrasonic stirring until the epoxy resin E44, the alpha-terpineol, the polyethylene glycol and the tributyl phosphate are completely dissolved to obtain an organic carrier;
s2: and (3) uniformly mixing 78.5g of the silver-coated copper powder prepared in the comparative example 1, 5g of the inorganic binder and 0.5g of the graphdiyne, mixing with 16g of the organic carrier prepared in the step S1, dispersing, rolling for 5 times, and filtering by using a filter screen with the diameter of 5 microns to obtain the silver-coated copper powder conductive paste.
The inorganic binder consists of V 2 O 5 48wt.％，P 2 O 5 7wt.％，Al 2 O 3 6wt.％，TeO 2 22wt.％，SiO 2 4wt.％，ZnO8wt.％，Bi 2 O 3 5wt.% of the components are mixed according to the proportion.
The conductive paste prepared above was sintered and cured at 500 ℃ under nitrogen protection, and the resistivity values were measured as shown in table 1.
Comparative example 4
Comparative example 4 differs from example 10 in that the sintering inhibitor graphdine was not added in comparative example 3, and the other steps are the same as in example 10.
After sintering and curing the conductive paste in the above examples 6 to 11 and comparative examples 2 to 4, the resistivity of the obtained sample was tested by using a four-probe tester; in the damp-heat test, the silver-coated copper powders prepared in the examples 6 to 11 and the comparative examples 2 to 4 are placed in a damp-heat environment with high temperature of 150 ℃ and relative humidity of 100% for 72 hours to test the change condition of the resistivity, the damp-heat test reflects the oxidation resistance of the silver-coated copper powders, and compared with the resistance before the damp-heat test, if the resistivity is increased much after the damp-heat test, the oxidation resistance of the silver-coated copper powders is weak, otherwise, the oxidation resistance of the silver-coated copper powders is strong.
The conductive paste without the sintering inhibitor was subjected to sintering curing at a temperature of 500 ℃ under nitrogen protection, and the resistivity values thereof were measured as shown in table 1.
Table 1 test results of resistivity of each example
Figure BDA0003843426360000191
As can be seen from Table 1, the resistivity of the conductive paste in comparative example 2 after sintering and curing was 1.17X 10 -4 Omega cm, the resistivity of the conductive paste in example 8 after sintering and curing is 1.31X 10 -5 Omega cm, the resistivity in the comparative example 2 is about 9 times of the resistivity in the experiment 8, which shows that the silver-coated copper powder prepared by the method has better conductivity; the resistivity of comparative example 2 increased by 20.5% after the hydrothermal test, and the resistivity of example 8 increased by 13.7% after the hydrothermal test, whereby the change in resistivity was small in example 8 compared to comparative example 2. The damp-heat experiment is an experiment for rapidly testing the oxidation and corrosion resistance of a sample in a high-temperature and high-humidity environment. This is probably because: grading proportion of silver-coated copper powder prepared by the methodThe conductive paste is more suitable, and is more tightly combined through sintering and curing, so that the contact resistance between the silver-coated copper powder is effectively reduced, the resistivity is smaller, and the conductive performance is better; on the other hand, lysozyme can effectively prevent copper powder from being oxidized as a pre-coating layer of the copper powder, and meanwhile lysozyme is subjected to physical and chemical adsorption and deposits compact silver particles on the surface of the copper powder depending on active groups on the surface of the lysozyme, so that the silver-coated copper powder is more compact, and the resistivity is smaller.
In contrast to example 7, the silver-coated copper powder used in comparative example 3 lacks lysozyme coating, and the resistivity in example 7 is 1.38X 10 -5 Ω · cm, while the resistivity in comparative example 3 is 2.75 × 10 -4 Ohm cm, the resistivity is respectively raised by 17.4% and 25.5% through a damp-heat test, which shows that the conductivity of the conductive paste in the embodiment 7 of the invention is better than that of the conductive paste in the comparative example 3 after sintering and curing, and the difference of the oxidation resistance performances of the embodiment 7 and the comparative example 3 is larger through the damp-heat test. This is probably because: according to the invention, lysozyme is subjected to physical and chemical adsorption and deposits compact silver particles on the surface of copper powder depending on active groups on the surface of the lysozyme, the lysozyme can effectively prevent the copper powder from being oxidized when being used as a pre-coating layer of the copper powder, and the obtained resistivity is relatively low. The silver-coated copper powder in the comparative example 3 which is not treated by the lysozyme has a less dense silver layer on the surface, the copper powder in the silver-coated copper powder is partially exposed, so that the oxidation resistance is not strong, and the resistivity in the comparative example 3 is increased to a greater extent through a damp-heat test.
In addition, as is clear from table 1, the resistivity of example 10 and comparative example 4 was 1.34 × 10 -5 Omega. Cm and 1.36X 10 -5 Omega cm, the resistivity obtained without addition of a graphite alkyne sintering inhibitor is relatively high, and the conductivity is slightly poor. Therefore, the contact resistance can be reduced to a certain extent by the graphdiyne, and the conductivity is improved. Through the damp-heat test, the resistivity of the conductive paste in the embodiment 10 and the resistivity of the conductive paste in the comparative example 4 are respectively increased by 17.9% and 22.1%, which indicates that the existence of the graphite alkyne can improve the conductivity of the conductive paste after sintering, and probably because the graphite alkyne sintering inhibitor can reduce the generation of microcracks at the contact sites of the conductive paste and the semiconductor in the sintering process, so that the oxidation corrosion can be more easily generated in a high-temperature and high-humidity environmentEtching causes a large increase in resistivity and a decrease in conductivity.
In summary, the change of resistivity of the conductive pastes of examples 6 to 11 and comparative examples 2 to 4 after sintering and curing is analyzed to show that: along with the increase of the addition amount of the silver-coated copper powder in the conductive paste, the resistivity of the conductive paste after sintering and curing is reduced, and the conductivity is better; compared with the examples 6-8, the grading and proportion of the copper powder used in the silver-coated copper powder are optimized, so that the prepared silver-coated copper powder also has the corresponding grading and proportion, the sintering compactness is improved, the conductivity of a sintered product is reduced, and the conductivity of the sintered material is enhanced; various active functional groups on the surface of the lysozyme can form a compact silver coating layer on the surface of the copper powder through the physical and chemical adsorption effect, so that the compactness of the silver coating layer on the surface of the copper powder is ensured, and the compactness can be proved through a damp-heat test; the existence of the graphite alkyne can improve the conductivity of the sintered conductive paste on one hand and prevent microcracks of the sintered conductive paste on the other hand, so that the resistivity is effectively maintained after a damp-heat experiment, and the conductivity of the sintered conductive paste is not affected as the addition amount of the graphite alkyne is increased.
Therefore, the silver-coated copper powder prepared by the technical scheme of the invention has the characteristics of good compactness, good conductivity and excellent oxidation resistance, adds a new preparation method for the conductive paste, and has good application prospect in the electronic field.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. The preparation method of the silver-coated copper powder is characterized by comprising the following steps of:
1) Preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 30-55mmol/L of tri (2-carboxyethyl) phosphine, and adjusting the pH value to 4.5-6.5 by using sodium hydroxide to obtain solution A; weighing lysozyme powder, adding the lysozyme powder into N-2-hydroxyethyl piperazine-N '-2-ethanesulfonic acid buffer solution to prepare N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 5-15mg/mL lysozyme, and adjusting the pH value to 6.5-7.0 by using sodium hydroxide to obtain solution B; uniformly mixing the solution A and the solution B in equal volume to obtain a solution C;
2) Weighing copper powder, uniformly mixing the copper powder with the solution C, standing at room temperature, forming a pre-protective film on the surface of the copper powder, and then centrifuging, washing with deionized water and drying to obtain pretreated copper powder;
3) Uniformly stirring and mixing the silver-ammonia solution, the sodium citrate solution and the polyvinylpyrrolidone solution at room temperature to obtain a silver-ammonia solution dispersion liquid; then placing the silver-ammonia solution dispersion liquid in an acoustic resonance mixing device, adding the pretreated copper powder, mixing for the first time in the acoustic resonance mixing device, adding a vitamin C solution in batches, mixing for the 2 nd to 4 th times, reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water, and drying to obtain primary silver-coated copper powder; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
2. The method for preparing silver-coated copper powder according to claim 1, wherein the molecular weight of lysozyme is 14.4kDa, and the activity of lysozyme is 30000-70000U/mg.
3. The method for preparing the silver-coated copper powder according to claim 1, wherein in the step 2), the copper powder is at least one of spherical copper powder, spheroidal copper powder, flake copper powder, rod copper powder and dendritic copper powder; wherein the content of the first and second substances,
the median diameter D of the spherical copper powder 50 =1-2 μm or 500nm, median diameter D of the flake copper powder 50 =0.5-3 μm and average thickness of 0.1-0.2 μm; and D is 50 Spherical copper powder of =1-2 μm in 60-100wt.% of said copper powder, D 50 Spherical copper powder of =500nm and median particle diameter D 50 Flake copper powder with the average thickness of 0.1-0.2 μm and the average thickness of 0.5-3 μm accounts for 10-40 wt% of the copper powder; and the tap density of the spherical copper powder is 4.5-5.5g/cm 3 The tap density of the flake copper powder is 4.5-6.0g/cm 3 The tap densities of the sphere-like copper powder, the rod-like copper powder and the dendritic copper powder are all 4.5-6.0g/cm 3 。
4. The method for preparing the silver-coated copper powder according to claim 1 or 3, wherein the mass-to-volume ratio of the copper powder to the solution C is 0.1-1g; and the pretreated copper powder is formed by forming a layer of lysozyme nanometer film with the thickness of 3-5nm on the surface of the copper powder.
5. The method for preparing silver-coated copper powder according to claim 1, wherein the method for preparing the silver-ammonia solution comprises: dispersing silver nitrate in water to obtain a silver nitrate solution with the mass fraction of 5wt.%, then adding ammonia water with the mass fraction of 16-25wt.%, and uniformly stirring and mixing until the mixture is clarified to obtain a silver ammonia solution;
the silver-ammonia solution dispersion liquid contains 1-3wt.% of silver-ammonia solution, 0.1-0.5wt.% of sodium citrate solution, 0.1-1wt.% of polyvinylpyrrolidone solution and 1-5wt.% of vitamin C solution; further, the mass ratio of silver nitrate, sodium citrate, polyvinylpyrrolidone and vitamin C in each 120mL of water in the silver-ammonia solution dispersion liquid is 1-2.0:0.2-0.5:0.2-0.8:2.0-5.0.
6. The method for preparing silver-coated copper powder according to claim 1 or 5, wherein the mass-to-volume ratio of the pretreated copper powder to the silver-ammonia solution dispersion is 1-50mg:100-300mL, and the first mixing time is 5-10min;
adding the vitamin C solution with the same volume into the acoustic resonance mixing equipment for three times, and mixing for 5-10min after adding the vitamin C solution each time.
7. The method for preparing silver-coated copper powder according to claim 1, wherein the particle diameter of the silver powder on the surface of the pretreated copper powder is 0.5 to 2.0 μm, and the specific surface area is 0.5 to 7m 2 (ii)/g; the particle size of the silver-coated copper powder is 0.6-5.2 mu m, and the specific surface area is 0.4-6 m 2 (iv) g; and preserving the heat of the primary silver-coated copper powder in a vacuum oven at 45 ℃ for 30min to obtain the silver-coated copper powder.
8. Use of silver-coated copper powder prepared according to any one of claims 1 to 7 in an electroconductive paste, wherein the electroconductive paste comprises, in mass percent:
55-85% of silver-coated copper powder, 15-45% of organic carrier, 2-10% of inorganic binder and 0.5-2% of sintering inhibitor;
wherein the organic carrier is prepared from organic resin, an organic solvent, a dispersing agent and a defoaming agent according to the mass percentage of 10-40%:60-85%:0.1-1.0%:0.1-1.0 percent;
the method for preparing the silver-coated copper powder conductive paste specifically comprises the following steps:
s1: respectively weighing the organic resin, the organic solvent, the dispersant and the defoamer according to the mass percent, and ultrasonically stirring and uniformly mixing until the organic resin, the organic solvent, the dispersant and the defoamer are completely dissolved to obtain an organic carrier;
s2: and uniformly mixing the silver-coated copper powder, the inorganic binder and the sintering inhibitor, then mixing the mixture with the organic carrier prepared in the step S1, dispersing, rolling for 3-5 times, and filtering by using a filter screen with the diameter of 2-6 mu m to obtain the silver-coated copper powder conductive slurry.
9. Use according to claim 8, wherein the organic resin is a polypyrrolidone, an epoxy resin, a phenolic resin, an acrylic, a urethane, a silicone, a polyalkylene carbonate, a polyvinyl acetal or a cellulose;
the organic solvent is ethanol, alpha-terpineol, diethylene glycol butyl ether, tributyl citrate, diethylene glycol butyl ether acetate, alcohol ester dodeca, dimethyl succinate or dimethyl glutarate;
the dispersant is at least one of polyethylene glycol, polyacrylic acid (PAA-800-PAA-5000), polyvinyl alcohol, myristyl alcohol, dodecylamine, oleylamine, castor oil, octyl mercaptan and dodecyl mercaptan;
the defoaming agent is tributyl phosphate or polyether defoaming agent GPE-3000.
10. The use according to claim 8, wherein the inorganic binder is glass frit, the glass frit has a softening point of 250-350 ℃, and the inorganic binder comprises the following components in mol percent:
V 2 O 5 45-55wt.％，P 2 O 5 5-15wt.％，Al 2 O 3 3-8wt.％，TeO 2 20-35wt.％，SiO 2 2-7wt.％，ZnO 3-10wt.％，Bi 2 O 3 2-6wt.％；
the sintering inhibitor is graphdiyne.
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