CN115365494B - 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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CN115365494B
CN115365494B CN202211111459.XA CN202211111459A CN115365494B CN 115365494 B CN115365494 B CN 115365494B CN 202211111459 A CN202211111459 A CN 202211111459A CN 115365494 B CN115365494 B CN 115365494B
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copper powder
silver
solution
coated copper
mixing
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CN115365494A (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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    • 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 silver-coated copper powder is prepared by adopting lysozyme as a pre-protection layer of copper powder to prevent oxidation of the copper powder, reducing silver ions on the surface of the copper powder in situ by adopting lysozyme as a transition layer to form a uniform silver shell, and then performing low-temperature heating treatment. The invention also provides an application of the silver-coated copper powder in the 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 solidification, and also has good conductivity, and the resistivity is as low as 1.3x10 ‑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 use amount of silver powder is continuously increased, so that in order to reduce the cost, it is expected to develop a 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 hopefully reduces 30% -50% of silver paste cost, and conductivity is similar to silver, however, a silver coating layer on the surface of copper powder in the prior art is often deposited to be not compact and uneven, partial exposed surface of inner-layer copper powder appears, the exposed copper powder is more easily oxidized, and the combination between 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 which is widely used in plant juice, animal secretion, tears, saliva, milk, eggs and partial bacteria, and can make cell wall rupture content escape to dissolve bacteria, and can also be directly combined with negatively charged viral proteins to form double salts with DNA, RNA and apoprotein to inactivate 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, disulfide bonds in the lysozyme structure can be opened by a reducing agent of tris (2-carbonyl ethyl) phosphorus hydrochloride (TCEP), so that the configuration of the lysozyme is converted, and a stable and uniform phase-converted lysozyme nano film is formed on the surface of a carrier.
However, there is no report in the prior art that lysozyme is used as a pre-protective layer of copper powder, and then silver ions are reduced on the surface of the pre-protective layer to form a uniform silver shell layer by using lysozyme as a transition layer. The invention provides a preparation method for preparing silver-coated copper powder, which can solve the problems of poor compactness, uniformity and conductivity of silver-coated copper powder in the prior art.
Disclosure of Invention
To solve the problems existing in the prior art that the silver in the silver-coated copper powderThe invention provides a preparation method of silver-coated copper powder, which adopts lysozyme as a pre-protective layer of the copper powder to prevent oxidation of the copper powder, reduces silver ions in situ on the surface of the copper powder by using lysozyme as a transition layer to form a uniform silver shell, and carries out low-temperature heating treatment to obtain the silver-coated copper powder. In addition, the invention also provides an application of the silver-coated copper powder in the conductive paste, and the prepared conductive paste has good conductivity and low resistivity of 1.3 multiplied by 10 after being sintered and solidified by mixing with an organic carrier, an inorganic binder and a sintering inhibitor -5 Ω·cm。
For clearly illustrating the preparation method of the silver-coated copper powder in the invention, the preparation of the silver-coated copper powder is carried out according to the following steps:
1) Preparing a buffer solution of N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid with the concentration of 30-55mmol/L tri (2-carboxyethyl) phosphine, and regulating the pH value to 4.5-6.5 by using sodium hydroxide, and recording as a solution A; weighing lysozyme powder, adding the lysozyme powder into N-2-hydroxyethyl piperazine-N '-2-ethanesulfonic acid buffer solution, preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 5-15mg/mL lysozyme, adjusting the pH value to 6.5-7.0 by sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C;
2) Weighing copper powder and uniformly mixing the copper powder with the solution C, standing at room temperature, forming a pre-protecting film on the surface of the copper powder, and then centrifuging, washing with deionized water and drying to obtain pretreated copper powder;
3) Stirring and mixing the silver-ammonia solution, the sodium citrate solution and the polyvinylpyrrolidone solution uniformly at room temperature to obtain silver-ammonia solution dispersion; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, adding the pretreated copper powder, adding a vitamin C solution in batches after first mixing in the acoustic resonance mixing device, carrying out 2-4 times of mixing, 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 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 a microphone reagent net.
Optionally, the copper powder is at least one of spherical copper powder, spheroidal copper powder, flaky copper powder, rod-shaped copper powder and dendritic copper powder; wherein, the liquid crystal display device comprises a liquid crystal display device,
median particle diameter D of the spherical copper powder 50 =1-2 μm or 500nm, median particle diameter D of the flake copper powder 50 =0.5-3 μm, average thickness 0.1-0.2 μm; and D is 50 Spherical copper powder=1-2 μm accounts for 60-100wt.% of the copper powder, D 50 Spherical copper powder of 500nm and median particle diameter D 50 Flake copper powder with an average thickness of 0.1-0.2 μm, accounting for 10-40wt.% of the copper powder, respectively, =0.5-3 μm; 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 density of the quasi-spherical copper powder, the rod-shaped copper powder and the dendritic copper powder is 4.5-6.0g/cm 3 。
According to the invention, through adjusting the grading proportion of copper powder, after different types of copper powder are mixed, copper powder particles can be mutually meshed more tightly when the copper powder is applied to sintering of conductive paste, so that the sintering compactness is enhanced, the sintering yield of a product is improved, and the conductivity of a sintered material is enhanced.
Further alternatively, the mass volume ratio of the copper powder to the solution C is 0.1-1g:100-250mL, and the standing time is 30-90min; preferably, the mass volume ratio of copper powder to solution C is 0.5-1g:100-200mL to ensure that lysozyme can form a uniform and compact protective film on the surface of copper powder; and too much solution C is added to cause waste, and too little can not effectively wrap copper powder.
In addition, the pretreatment copper powder is characterized in that a lysozyme nano film with the thickness of 3-5nm is formed on the surface of the copper powder.
The configuration of lysozyme is maintained by 4 pairs of disulfide bonds in the lysozyme structure, and the disulfide bonds are acted by the reducing agent tri (2-carbonyl ethyl) phosphorus, so that the configuration of lysozyme is converted, and a stable and uniform phase-converted lysozyme nano film is formed on the surface of copper powder. The phase-transition lysozyme nano film can be attached to the surface of copper powder to form a compact protective layer, so that oxidation of the copper powder is avoided, the problem that the copper powder is oxidized or corroded in the process of preparing silver-coated copper powder is effectively solved, and the conductivity of the silver-coated copper powder can be improved.
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 carboxyl and 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 groups can form Ag-S bond action with the silver ions, so that silver salt is firmly combined on the surface of the lysozyme, and a compact silver coating layer is formed 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 5 wt%, adding ammonia water with the mass fraction of 16-25 wt%, and stirring and mixing uniformly until the silver nitrate solution is clarified to obtain a silver ammonia solution;
and 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 dispersing agent and is matched with sodium citrate for use, so that uniform and compact nano silver-coated copper powder particles are generated by better dispersing. The vitamin C is a reducing agent for reducing silver ions in the silver nitrate.
Optionally, the mass 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 in the same volume fraction in the sound resonance mixing equipment for three times, and the mixing is carried out for 5-10min after each addition, so that the vitamin C fully reduces the silver powder.
It should be noted that the acoustic resonance mixing technology is a whole-field mixing technology, and is a novel mixing technology based on the coupling effect of vibration macroscopic mixing and acoustic flow microscopic mixing, so that not only can the whole-field uniform dispersion of the mixed materials be realized through massive mixing and micromixing, but also physical damage to the mixed materials caused by shearing of paddles or friction collision with wall surfaces can be avoided, and because the mixing mode uses low-frequency acoustic flow, severe thermal effects can not occur. Compared with the traditional impeller type mixing, the acoustic resonance mixing technology has the advantages of no intervening 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 sound resonance mixing equipment and adopts equipment sold by Waldebrand technology (Shenzhen) and with the model G2000.
Further, the grain diameter of 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 /g; the grain diameter of the silver-coated copper powder is 0.6-5.2 mu m, and the specific surface area is 0.4-6 m 2 /g; and the primary silver-coated copper powder is subjected to vacuum oven heat preservation at 45 ℃ for 30min to obtain the silver-coated copper powder.
The invention also claims the application of the silver-coated copper powder prepared by the method in conductive slurry.
The composition of 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% of the composition;
and, the method for preparing silver coated copper powder conductive paste specifically comprises:
s1: respectively weighing the organic resin, the organic solvent, the dispersing agent and the defoaming agent according to the mass percentages, and stirring and mixing uniformly by ultrasonic until the organic resin, the organic solvent, the dispersing agent and the defoaming agent are completely dissolved to obtain an organic carrier;
s2: and uniformly mixing silver-coated copper powder, an inorganic binder and a sintering inhibitor, then mixing with the organic carrier prepared in the step S1, dispersing, rolling for 3-5 times, and filtering through a filter screen with the diameter of 2-6 mu m to obtain the silver-coated copper powder conductive paste.
Optionally, the mass percentage of the silver-coated copper powder in the conductive paste is 65-80wt.%; during sintering of the conductive paste, lysozyme in the silver-coated copper powder is subjected to thermal decomposition when the temperature exceeds 200 ℃, so that the silver-coated copper powder is more densely combined;
the mass percentage of the organic carrier in the conductive paste is 20-40wt.%. The organic carrier has the function of adjusting the viscosity of the conductive paste, and adjusting and controlling the shrinkage rate of the conductive paste during drying and sintering, so that better sintering adhesive force between the conductive paste and the carrier is obtained.
Optionally, the organic resin is polypyrrolidone, epoxy resin, phenolic resin, acrylic acid, carbamate, silicone resin, polyalkylene carbonate, polyvinyl acetal or cellulose; preferably the organic resin is selected from the group consisting of polyvinyl formal, polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone or carboxyethyl cellulose;
the organic solvent is ethanol, alpha-terpineol, diethylene glycol butyl ether, tributyl citrate, diethylene glycol butyl ether acetate, alcohol ester twelve, dimethyl succinate or dimethyl glutarate;
the dispersing agent is at least one of polyethylene glycol, polyacrylic acid (PAA-800-PAA-5000), polyvinyl alcohol, myristyl alcohol, dodecyl amine, oleyl amine, castor oil, octyl mercaptan and dodecyl mercaptan;
the defoamer is tributyl phosphate or polyether defoamer 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 in mole 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 Playing a role 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, reducing the problem of different thermal expansion coefficients during sintering, and reducing the Bi 2 O 3 The contact surface of Ag and Si in the conductive paste is more continuous, the softening point and the packaging temperature are reduced, and the SiO is prepared 2 、P 2 O 5 Acting as a network former, siO 2 ZnO prevents the conductive paste from being excessively sintered, and Gao Yinbao copper powder particles are contacted with the surface of the semiconductor;
the sintering inhibitor is graphite alkyne and has the functions of preventing the shrinkage effect between the semiconductor and the conductive paste in the sintering process, thereby reducing the contact resistance, reducing microcracks generated at the contact sites between the conductive paste and the semiconductor, and improving the conductivity and the sintering conversion factor. The semiconductor can be silicon or silicon carbide; the graphite alkyne is purchased from pioneer nanometer, and the product model is XFY01. Graphite alkyne is a high temperature resistant material, can maintain a stable crystal structure at high temperature, and can avoid sintering failure caused by overhigh sintering temperature.
Based on the above, the preparation method of the silver-coated copper powder and the application of the silver-coated copper powder in the conductive paste disclosed by the invention have the following advantages compared with the prior art:
(1) The invention provides a preparation method of silver-coated copper powder, which adopts lysozyme as a pre-protective layer of copper powder to effectively isolate oxygen and prevent oxidation of copper powder, and then uses lysozyme as a transition layer to reduce silver ions on the surface of the copper powder in situ to form a uniform silver shell, and then carries out low-temperature heating treatment to prepare the silver-coated copper powder. The molecular structure of lysozyme contains carboxyl, hydroxyl, amino, thiol and other functional groups, on one hand, the carboxyl and hydroxyl functional groups can chelate silver ions to ensure that silver particles are stably adsorbed on the surface layer of lysozyme, on the other hand, the thiol functional groups can form Ag-S bonding action with silver ions to firmly bond silver salt on the surface of lysozyme, and a compact silver coating layer is formed on the surface of copper powder;
(2) The invention also provides an application of the silver-coated copper powder in the 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 solidification, and the resistivity is as low as 1.3 multiplied by 10 -5 Omega cm. The silver-coated copper powder with different particle sizes prepared by selecting copper powder with different particle sizes is used for adjusting reasonable powder grading, improving the compactness of sintering and the yield of sintered products, and enhancing the conductivity of the sintered material; the graphite alkyne which is a high-temperature resistant material is innovatively used as a sintering inhibitor, so that the contact resistance can be reduced, microcracks generated at contact sites between the conductive paste and a semiconductor can be reduced, and the conductivity can be improved; the organic carrier and the inorganic binder can adjust the viscosity of the conductive paste, adjust 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 the semiconductor.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The water used in the invention is deionized water unless specified otherwise. The reagents are commercially available unless otherwise specified.
The invention is further illustrated, but is not limited, by the following examples.
Example 1
1) Preparing an N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with the concentration of 40mmol/L of tri (2-carboxyethyl) phosphine, regulating the pH value to 6.3 by using sodium hydroxide, and marking as a solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with lysozyme concentration of 12mg/mL and lysozyme activity of 40000U/mg, regulating pH to 6.5 by sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C;
2) Weighing a certain amount of copper powder and solution C, uniformly mixing according to the mass volume ratio of 1g to 250mL, standing at room temperature for 60min, forming a pre-protecting film on the surface of the copper powder, and obtaining pretreated copper powder through centrifugation, washing with deionized water and drying;
the copper powder is D 50 Spherical copper powder of =1-2 μm, said D 50 Spherical copper powder=1-2 μm accounts for 100% of the total mass of the copper powder.
3) Uniformly stirring and 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; then placing silver-ammonia solution dispersion liquid into acoustic resonance mixing equipment, adding the pretreated copper powder, adding vitamin C solution with the same volume of 5wt.% for three times after first mixing in the acoustic resonance mixing equipment, carrying out 4 th mixing, 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, each 120mL of water in the silver ammonia solution dispersion liquid is corresponding to silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C comprises 1.5g by mass: 0.4g:0.6g:4.0g; the mass volume ratio of the pretreated copper powder to the 3wt.% silver-ammonia solution dispersion is 50mg:250mL, and the first mixing and the subsequent three mixing times in the acoustic resonance mixing apparatus were 10min.
Example 2
1) Preparing an N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with the concentration of 45mmol/L of tris (2-carboxyethyl) phosphine, regulating the pH value to 6.0 by using sodium hydroxide, and marking as a solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with lysozyme concentration of 15mg/mL and lysozyme activity of 40000U/mg, regulating pH to 6.5 by sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C;
2) Weighing a certain amount of copper powder and solution C, uniformly mixing according to the mass-volume ratio of 1g to 200mL, standing for 90min at room temperature, forming a pre-protecting film on the surface of the copper powder, and obtaining pretreated copper powder through centrifugation, washing with deionized water and drying;
the copper powder is D 50 Spherical copper powder of =1-2 μm and D 50 Sheet copper powder having an average thickness of 0.1 to 0.2 μm and =0.5 to 3 μm, the D 50 Spherical copper powder of 1-2 μm accounting for 60% of the total mass of the copper powder, said D 50 Flake copper powder with the average thickness of 0.1-0.2 μm accounting for 40% of the total mass of the copper powder, wherein the copper powder is in a range of 0.5-3 μm.
3) Uniformly stirring and 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; then placing silver-ammonia solution dispersion liquid into acoustic resonance mixing equipment, adding the pretreated copper powder, adding vitamin C solution with the same volume of 5wt.% for three times after first mixing in the acoustic resonance mixing equipment, carrying out 3 times of mixing, and obtaining primary silver-coated copper powder after reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water and drying; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein, each 120mL of water in the silver ammonia solution dispersion liquid is corresponding to silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C is 2.0g:0.5g:0.8g:5.0g; the mass volume ratio of the pretreated copper powder to the 2.5wt.% silver-ammonia solution dispersion is 50mg:200mL, and 8min for both the first mixing and the subsequent three mixing times in the acoustic resonance mixing apparatus.
Comparative example 1
Comparative example 1 was different from example 2 in that the copper powder was not subjected to lysozyme coating treatment, and the other operation steps were the same as in example 2. The specific procedure of comparative example 1 is as follows:
1) Preparing an N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with the concentration of 45mmol/L of tris (2-carboxyethyl) phosphine, regulating the pH value to 6.0 by using sodium hydroxide, and marking as a solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with lysozyme concentration of 15mg/mL and lysozyme activity of 40000U/mg, regulating pH to 6.5 by sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C;
2) 1g of copper powder is weighed, wherein the copper powder is D 50 Spherical copper powder of =1-2 μm and D 50 Sheet copper powder having an average thickness of 0.1 to 0.2 μm and =0.5 to 3 μm, the D 50 Spherical copper powder of 1-2 μm accounting for 60% of the total mass of the copper powder, said D 50 Flake copper powder with the average thickness of 0.1-0.2 μm accounting for 40% of the total mass of the copper powder, wherein the copper powder is in a range of 0.5-3 μm;
3) Uniformly stirring and 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; then placing silver-ammonia solution dispersion liquid into acoustic resonance mixing equipment, adding the pretreated copper powder, adding vitamin C solution with the same volume of 5wt.% for three times after first mixing in the acoustic resonance mixing equipment, carrying out 3 times of mixing, and obtaining primary silver-coated copper powder after reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing with water and drying; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein, each 120mL of water in the silver ammonia solution dispersion liquid is corresponding to silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C is 2.0g:0.5g:0.8g:5.0g; the mass volume ratio of the pretreated copper powder to the 2.5wt.% silver-ammonia solution dispersion is 50mg:200mL, and 8min for both the first mixing and the subsequent three mixing times in the acoustic resonance mixing apparatus.
Example 3
1) Preparing a buffer solution of N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid with the concentration of 30mmol/L of tri (2-carboxyethyl) phosphine, regulating the pH value to 5.0 by using sodium hydroxide, and marking as a solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with the lysozyme concentration of 10mg/mL and the lysozyme activity of 30000U/mg, adjusting the pH value to 6.5 by sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C;
2) Weighing a certain amount of copper powder and solution C, uniformly mixing according to the mass-volume ratio of 0.8g to 200mL, standing for 45min at room temperature, forming a pre-protecting film on the surface of the copper powder, and obtaining pretreated copper powder through centrifugation, washing with deionized water and drying;
the copper powder is D 50 =1-2 μm and D 50 Spherical copper powder=500 nm, said D 50 Spherical copper powder of=1-2 μm accounting for 70% of the total mass of the copper powder, said D 50 Spherical copper powder=500 nm accounts for 30% of the total mass of the copper powder.
3) Uniformly stirring and 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; then placing silver-ammonia solution dispersion liquid into acoustic resonance mixing equipment, adding the pretreated copper powder, adding vitamin C solution with the same volume of 4wt.% for three times after first mixing in the acoustic resonance mixing equipment, carrying out 3 times of mixing, and obtaining primary silver-coated copper powder after silver ions on the surface of the pretreated copper powder are reduced into nano silver particles, taking out, centrifuging, washing and drying; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein, each 120mL of water in the silver ammonia solution dispersion liquid is corresponding to silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C comprises 1.5g by mass: 0.4g:0.7g:3.0g; the mass volume ratio of the pretreated copper powder to the 2.0wt.% silver-ammonia solution dispersion is 30mg:250mL, and the first mixing and the subsequent three mixing times in the acoustic resonance mixing apparatus were 9min.
Example 4
1) Preparing an N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with the concentration of 35mmol/L of tri (2-carboxyethyl) phosphine, regulating the pH value to 4.5 by using sodium hydroxide, and marking as a solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid buffer solution with lysozyme concentration of 12mg/mL and lysozyme activity of 50000U/mg, regulating pH to 7.0 by sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C;
2) Weighing a certain amount of copper powder and solution C, uniformly mixing according to the mass-volume ratio of 1g to 220mL, standing for 50min at room temperature, forming a pre-protecting film on the surface of the copper powder, and obtaining pretreated copper powder through centrifugation, washing with deionized water and drying;
the copper powder is D 50 Spherical copper powder of =1-2 μm, D 50 Spherical copper powder of =500 nm and D 50 Sheet copper powder having an average thickness of 0.1 to 0.2 μm and =0.5 to 3 μm, the D 50 Spherical copper powder of 1-2 μm accounting for 60% of the total mass of the copper powder, said D 50 Spherical copper powder=500 nm accounting for 25% of the total mass of the copper powder, said D 50 Flake copper powder with the average thickness of 0.1-0.2 μm accounting for 15% of the total mass of the copper powder, wherein the copper powder is in a range of 0.5-3 μm.
3) Uniformly stirring and 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; then placing silver-ammonia solution dispersion liquid into acoustic resonance mixing equipment, adding the pretreated copper powder, adding vitamin C solution with the same volume of 4.5wt.% for three times after first mixing in the acoustic resonance mixing equipment, carrying out 3 times of mixing, and obtaining primary silver-coated copper powder after reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing and drying; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein, each 120mL of water in the silver ammonia solution dispersion liquid is corresponding to silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C is 2.0g:0.5g:0.6g:5.0g; the mass volume ratio of the pretreated copper powder to the 3.0wt.% silver-ammonia solution dispersion is 40mg:250mL, and 7min for both the first mixing and the subsequent three mixing times in the acoustic resonance mixing apparatus.
Example 5
1) Preparing a buffer solution of N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid with the concentration of 30mmol/L of tri (2-carboxyethyl) phosphine, regulating the pH value to 5.0 by using sodium hydroxide, and marking as a solution A; taking N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic 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 sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C; weighing a certain amount of copper powder and solution C according to the mass volume ratio of 1g to 240mL, uniformly mixing, standing for 30min at room temperature, forming a pre-protecting film on the surface of the copper powder, and obtaining pretreated copper powder through centrifugation, washing with deionized water and drying;
2) The copper powder is D 50 Spherical copper powder of =1-2 μm, D 50 Spherical copper powder of =500 nm and D 50 Sheet copper powder having an average thickness of 0.1 to 0.2 μm and =0.5 to 3 μm, the D 50 Spherical copper powder of=1-2 μm accounting for 70% of the total mass of the copper powder, said D 50 Spherical copper powder of 500nm 15% of the total mass of the copper powder, said D 50 Flake copper powder with the average thickness of 0.1-0.2 μm accounting for 15% of the total mass of the copper powder, wherein the copper powder is in a range of 0.5-3 μm.
3) Uniformly stirring and 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; then placing silver-ammonia solution dispersion liquid into acoustic resonance mixing equipment, adding the pretreated copper powder, adding vitamin C solution with the same volume of 4.5wt.% for three times after first mixing in the acoustic resonance mixing equipment, carrying out 3 times of mixing, and obtaining primary silver-coated copper powder after reducing silver ions on the surface of the pretreated copper powder into nano silver particles, taking out, centrifuging, washing and drying; and finally, drying the primary silver-coated copper powder to obtain the silver-coated copper powder.
Wherein, each 120mL of water in the silver ammonia solution dispersion liquid is corresponding to silver nitrate: sodium citrate: polyvinylpyrrolidone: the vitamin C comprises the following components in percentage by mass: 0.3g:0.2g:3.0g; the mass volume ratio of the pretreated copper powder to the 1.0wt.% silver-ammonia solution dispersion is 40mg:200mL, and the time for the first mixing and the subsequent three mixing in the acoustic resonance mixing apparatus was 5min.
The following examples 6 to 13 are the preparation processes of the conductive paste.
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 stirring and mixing uniformly by ultrasonic until the components are completely dissolved to obtain an organic carrier;
s2: 78.5g of silver-coated copper powder prepared in the example 1, 5g of inorganic binder and 0.5g of graphite alkyne are uniformly mixed, 16g of the silver-coated copper powder is mixed with the organic carrier prepared in the S1, dispersed and rolled for 5 times, and filtered by a 5 mu m filter screen, so that the silver-coated copper powder conductive paste is obtained.
The inorganic binder is formed by 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.
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 stirring and mixing uniformly by ultrasonic until the components are completely dissolved to obtain an organic carrier;
s2: 78.5g of silver-coated copper powder prepared in the example 2, 5g of inorganic binder and 0.5g of graphite alkyne are uniformly mixed, 16g of the silver-coated copper powder is mixed with the organic carrier prepared in the S1, dispersed and rolled for 5 times, and filtered by a 5 mu m filter screen, so that the silver-coated copper powder conductive paste is obtained.
The inorganic binder is formed by 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.
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 stirring and mixing uniformly by ultrasonic until the components are completely dissolved to obtain an organic carrier;
s2: 78.5g of silver-coated copper powder prepared in example 4, 5g of inorganic binder and 0.5g of graphite alkyne are uniformly mixed, 16g of the silver-coated copper powder is mixed with the organic carrier prepared in S1, dispersed and rolled for 5 times, and filtered by a 5 mu m filter screen, so that the silver-coated copper powder conductive paste is obtained.
The inorganic binder is formed by 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.
Example 9
The preparation method of the conductive paste comprises the following steps:
s1: weighing 25g of polyvinyl formal, 73g of diethylene glycol butyl ether, 1g of polyacrylic acid (PAA-800) and 1.0g of tributyl phosphate, and stirring and mixing uniformly by ultrasonic until the polyvinyl formal, the diethylene glycol butyl ether, the polyacrylic acid and the tributyl phosphate are completely dissolved to obtain an organic carrier;
s2: 70g of silver-coated copper powder prepared in the example 4, 6g of inorganic binder and 1.0g of graphite alkyne are uniformly mixed, 23g of the silver-coated copper powder is mixed with the organic carrier prepared in the S1, dispersed and rolled for 4 times, and filtered by a 6 mu m filter screen, so that the silver-coated copper powder conductive paste is obtained.
The inorganic binder is formed by 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.% are mixed in 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 stirring and mixing uniformly by ultrasonic until the polyvinyl alcohol and the diethylene glycol butyl ether acetate are completely dissolved to obtain an organic carrier;
s2: 69g of silver-coated copper powder prepared in the example 4, 8g of inorganic binder and 1.5g of graphite alkyne are uniformly mixed, 21.5g of the silver-coated copper powder is mixed with the organic carrier prepared in the S1, dispersed and rolled for 3 times, and filtered by a 4 mu m filter screen, so that the silver-coated copper powder conductive paste is obtained.
The inorganic binder is formed by 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.% are mixed in 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 octanethiol and 0.5g of tributyl phosphate, and stirring and mixing uniformly by ultrasonic until the polyvinyl formal, the dimethyl succinate, the octanethiol and the tributyl phosphate are completely dissolved to obtain an organic carrier;
s2: 80g of silver-coated copper powder prepared in the example 4, 2g of inorganic binder and 2.0g of graphite alkyne are uniformly mixed, 16g of the silver-coated copper powder is mixed with the organic carrier prepared in the S1, dispersed and rolled for 5 times, and filtered by a 5 mu m filter screen, so that the silver-coated copper powder conductive paste is obtained.
The inorganic binder is formed by 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.% are mixed in proportion.
The prepared conductive paste is sintered and solidified at 500 ℃ under the protection of nitrogen, and the resistivity value is tested as shown in table 1.
Comparative example 2
Comparative example 2 differs from example 8 in that the silver-coated copper powder was commercially available from silver peak metal technologies, inc. (China) in Guangzhou, model YF-1705, tap density of 4.5-4.9g/cm 3 The procedure of example 8 was followed except for the above-mentioned steps.
Comparative example 3
Comparative example 3 the silver-coated copper powder used was devoid of lysozyme encapsulation compared to example 7, with the other steps being identical to example 7. The preparation method of the conductive paste in comparative example 3 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 stirring and mixing uniformly by ultrasonic until the components are completely dissolved to obtain an organic carrier;
s2: 78.5g of silver-coated copper powder prepared in comparative example 1, 5g of inorganic binder and 0.5g of graphite alkyne are uniformly mixed, 16g of the silver-coated copper powder is mixed with the organic carrier prepared in S1, dispersed and rolled for 5 times, and filtered by a 5 mu m filter screen, so that the silver-coated copper powder conductive paste is obtained.
The inorganic binder is formed by 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.
The prepared conductive paste is sintered and solidified at 500 ℃ under the protection of nitrogen, and the resistivity value is tested as shown in table 1.
Comparative example 4
Comparative example 4 differs from example 10 in that the sintering inhibitor graphite alkyne was not added in comparative example 3, and the other steps were the same as in example 10.
The conductive pastes of examples 6 to 11 and comparative examples 2 to 4 above were sintered and cured, and then the resistivity of the obtained samples was measured using a four-probe tester; the wet heat test is to place the silver-coated copper powder prepared in examples 6-11 and comparative examples 2-4 in a wet heat environment with a high temperature of 150 ℃ and a relative humidity of 100% for 72 hours, and test the change condition of the resistivity, wherein the wet heat test reflects the oxidation resistance of the silver-coated copper powder, and compared with the silver-coated copper powder before the wet heat test, if the resistivity is increased much after the wet heat test, the oxidation resistance of the silver-coated copper powder is weak, otherwise, the oxidation resistance of the silver-coated copper powder 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 tested as shown in table 1.
Table 1 results of resistivity testing for various examples
Figure BDA0003843426360000191
As can be seen from Table 1, the resistivity of the conductive paste of comparative example 2 after sintering and curing was 1.17X10 -4 Omega cm, resistivity of the conductive paste of example 8 after sintering and curing was 1.31X10 -5 The resistivity in the comparative example 2 is about 9 times that in the experiment 8, which shows that the silver-coated copper powder prepared in the invention has better conductivity; the resistivity of comparative example 2 was increased by 20.5% after the wet heat test, and the resistivity of example 8 was increased by 13.7% after the wet heat test, whereby the range of change in resistivity was smaller in example 8 than in comparative example 2. The damp-heat experiment is an experiment for rapidly testing the oxidation corrosion resistance of the test sample in a high-temperature high-humidity environment. This may be because: the silver-coated copper powder prepared by the method has more proper grading proportion, and the conductive paste 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 property is better; on the other hand, when lysozyme is used as a pre-coating layer of copper powder, the lysozyme can effectively prevent copper powder from oxidizing, and the lysozyme depends on active groups on the surface of the lysozyme to be subjected to physical and chemical adsorption on the surface of the copper powder and deposit compact silver particles, so that the silver-coated copper powder is more compact, and the resistivity is smaller.
In comparison with example 7, the silver-coated copper powder used in comparative example 3 lacks lysozyme coating, and has a resistivity of 1.38X10 in example 7 -5 Omega cm, whereas the resistivity in comparative example 3 was 2.75X10 -4 According to the wet heat test, the resistivity of the conductive paste is respectively increased by 17.4 percent and 25.5 percent, which shows that the conductive paste in the embodiment 7 of the invention is better in conductivity than the conductive paste in the comparative example 3 after sintering and curing, and the wet heat test shows that the oxidation resistance performance difference between the embodiment 7 and the comparative example 3 is larger. This may be because: in the invention, lysozyme relies on active groups on the surface of the lysozyme to be subjected to physical and chemical adsorption on the surface of copper powder and deposit compact silver particles, and the lysozyme is used asThe pre-coating layer for the copper powder can effectively prevent the copper powder from oxidizing, and the obtained resistivity is smaller. However, the silver layer on the surface of the silver-coated copper powder in the comparative example 3 which is not subjected to lysozyme treatment is not compact enough, and the oxidation resistance is not strong due to partial exposure of the copper powder in the silver-coated copper powder, and the resistivity in the comparative example 3 is increased to a larger extent through a damp-heat test.
Further, as can be seen from Table 1, the resistivity of example 10 and comparative example 4 was 1.34×10 -5 Omega cm and 1.36×10 -5 The resistivity obtained without adding graphite alkyne sintering inhibitor is larger in omega cm, and the conductivity is slightly poor. From this, it can be seen that the graphite alkyne can reduce contact resistance to some extent and improve conductivity. However, through the damp-heat test, the resistivity of the embodiment 10 and the comparative example 4 are respectively increased by 17.9% and 22.1%, which indicates that the presence of the graphite alkyne can improve the conductivity of the conductive paste after sintering, and this is probably because the graphite alkyne sintering inhibitor can reduce the microcrack generated by the contact site between the conductive paste and the semiconductor in the sintering process, so that the oxidation corrosion is more likely to occur under the high-temperature and high-humidity environment, and the resistivity is greatly increased and the conductivity is reduced.
In summary, the resistivity change after sintering and curing of the conductive pastes in examples 6 to 11 and comparative examples 2 to 4 was analyzed to show: as the addition amount of the silver-coated copper powder in the conductive paste increases, the resistivity of the conductive paste after sintering and solidification also decreases, and the conductivity is better; comparative examples 6-8 show that the prepared silver-coated copper powder also has corresponding gradation and proportion by optimizing the gradation and proportion of copper powder used in the silver-coated copper powder, which is beneficial to improving the compactness of sintering, reducing the conductivity of a sintered product and enhancing the conductivity of a sintered material; the surface of lysozyme can form a compact silver coating layer on the surface of copper powder through physical and chemical adsorption, so that the compactness of the silver coating layer on the surface of copper powder is ensured, which can be verified from a damp-heat experiment, if the compactness is bad, the oxidation resistance of the conductive paste after sintering and solidification is easy to be reduced after the damp-heat experiment; the existence of the graphite alkyne can improve the conductivity of the conductive paste after sintering, and can prevent microcracks of the conductive paste after sintering, so that the resistivity is effectively maintained after a damp-heat experiment, and the conductivity of the conductive paste after sintering is not adversely affected along with the increase of the addition amount of the graphite alkyne.
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 a buffer solution of N-2-hydroxyethyl piperazine-N' -2-ethane sulfonic acid with the concentration of 30-55mmol/L tri (2-carboxyethyl) phosphine, and regulating the pH value to 4.5-6.5 by using sodium hydroxide, and recording as a solution A; weighing lysozyme powder, adding the lysozyme powder into N-2-hydroxyethyl piperazine-N '-2-ethanesulfonic acid buffer solution, preparing N-2-hydroxyethyl piperazine-N' -2-ethanesulfonic acid buffer solution with the concentration of 5-15mg/mL lysozyme, adjusting the pH value to 6.5-7.0 by sodium hydroxide, and marking as solution B; uniformly mixing the solution A and the solution B in equal volumes to obtain a solution C;
2) Weighing copper powder and uniformly mixing the copper powder with the solution C, standing at room temperature, forming a pre-protecting film on the surface of the copper powder, and then centrifuging, washing with deionized water and drying to obtain pretreated copper powder;
3) Stirring and mixing the silver-ammonia solution, the sodium citrate solution and the polyvinylpyrrolidone solution uniformly at room temperature to obtain silver-ammonia solution dispersion; then placing the silver-ammonia solution dispersion liquid into an acoustic resonance mixing device, adding the pretreated copper powder, adding a vitamin C solution in batches after first mixing in the acoustic resonance mixing device, mixing for 2-4 times, and taking out, centrifuging, washing and drying to obtain primary silver-coated copper powder after reducing silver ions on the surface of the pretreated copper powder into nano silver particles; 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 the lysozyme is 14.4kDa, and the activity of the lysozyme is 30000-70000U/mg.
3. The method for preparing silver-coated copper powder according to claim 1, wherein in the step 2), the copper powder is one or a combination of more than two of spherical copper powder, spheroidal copper powder, flaky copper powder, rod-shaped copper powder and dendritic copper powder; wherein, the liquid crystal display device comprises a liquid crystal display device,
median particle diameter D of the spherical copper powder 50 =1-2 μm or 500nm, median particle diameter D of the flake copper powder 50 =0.5-3 μm, average thickness 0.1-0.2 μm; and D is 50 Spherical copper powder=1-2 μm accounts for 60-100wt.% of the copper powder, D 50 Spherical copper powder of 500nm and median particle diameter D 50 Flake copper powder with an average thickness of 0.1-0.2 μm, which is 0.5-3 μm, all account for 10-40wt.% of the copper powder; 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 density of the quasi-spherical copper powder, the rod-shaped copper powder and the dendritic copper powder is 4.5-6.0g/cm 3 。
4. The method for preparing silver-coated copper powder according to claim 1 or 3, wherein the mass-volume ratio of the copper powder to the solution C is 0.1-1g:100-250mL, and the standing time is 30-90min; and the pretreatment copper powder is characterized in that a lysozyme nano film with the thickness of 3-5nm is formed 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 the following steps: dispersing silver nitrate in water to obtain a silver nitrate solution with the mass fraction of 5 wt%, adding ammonia water with the mass fraction of 16-25 wt%, and stirring and mixing uniformly until the silver nitrate solution is clarified to obtain a silver ammonia solution;
and the silver ammonia solution dispersion liquid contains 1-3wt.% of silver ammonia solution, 0.1-0.5wt.% of sodium citrate solution and 0.1-1wt.% of polyvinylpyrrolidone solution.
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, wherein the first mixing time is 5-10min;
the same volume of vitamin C solution was added three times in the acoustic resonance mixing apparatus and mixing was performed 5-10min after each addition of vitamin C solution.
7. The method for preparing silver-coated copper powder according to claim 1, wherein the particle size of silver powder on the surface of the pretreated copper powder is 0.5-2.0 μm and the specific surface area is 0.5-7 m 2 /g; the grain diameter of the silver-coated copper powder is 0.6-5.2 mu m, and the specific surface area is 0.4-6 m 2 /g; and the primary silver-coated copper powder is subjected to vacuum oven heat preservation 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 a conductive paste, wherein the composition of the conductive 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% of the composition;
and, the method for preparing silver coated copper powder conductive paste specifically comprises:
s1: respectively weighing the organic resin, the organic solvent, the dispersing agent and the defoaming agent according to the mass percentages, and stirring and mixing uniformly by ultrasonic until the organic resin, the organic solvent, the dispersing agent and the defoaming agent are completely dissolved to obtain an organic carrier;
s2: and uniformly mixing silver-coated copper powder, an inorganic binder and a sintering inhibitor, then mixing with the organic carrier prepared in the step S1, dispersing, rolling for 3-5 times, and filtering through a filter screen with the diameter of 2-6 mu m to obtain the silver-coated copper powder conductive paste.
9. The use according to claim 8, wherein the organic resin is a polypyrrolidone, epoxy resin, phenolic resin, acrylic, urethane, silicone resin, polyalkylene carbonate, polyvinyl acetal or cellulose;
the organic solvent is ethanol, alpha-terpineol, diethylene glycol butyl ether, tributyl citrate, diethylene glycol butyl ether acetate, alcohol ester twelve, dimethyl succinate or dimethyl glutarate;
the dispersing agent is one or more than two of polyethylene glycol, polyacrylic acid, polyvinyl alcohol, myristyl alcohol, dodecyl mercaptan, castor oil, octyl mercaptan and dodecyl mercaptan;
the defoamer is tributyl phosphate or polyether defoamer.
10. The use according to claim 8, wherein the inorganic binder is a glass frit having a softening point of 250-350 ℃, and the inorganic binder comprises the following components in mole 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 graphite alkyne.
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