A copper-silver composite paste suitable for 3D printing and a preparation method thereof

Abstract

The application provides a copper-silver composite slurry suitable for 3D printing, which comprises silver particles, copper-silver composite particles and an organic carrier, wherein the weight ratio of the organic carrier is 5%-40%; the copper-silver composite particles comprise copper particles and silver particles, and the copper particles and the silver particles are chelated by an organic ligand. In the application, the organic ligand is added after the preparation of copper nanoparticles and silver nanoparticles, respectively, and the organic ligand can be chelated with the two kinds of metal ions through heating reaction, so that part of the small-size silver nanoparticles are attached to the surface of the large-size copper particles, thereby forming a copper-silver nano mixed metal slurry. After sintering, the silver particles on the surface of the copper form a conductive path, which can significantly improve the conductive performance, and can effectively reduce the cost of the slurry and the oxidation problem of the copper particles in the storage process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive manufacturing technology, in particular to a copper-silver composite slurry suitable for 3D printing and a preparation method thereof. BACKGROUND

[0002] 3D printing is a kind of rapid prototyping technology, also known as additive manufacturing, which is a technology that constructs objects through layer-by-layer printing based on digital model files. Compared with traditional processes, it has incomparable advantages in shortening new product development and implementation cycle, efficiently forming more complex structures, realizing integration and lightweight design, etc. With the development of related technologies, 3D printing is gradually applied to conductive materials such as semiconductor leads and PCB lines. In similar application scenarios, conductor paste needs to be used for printing, and the final product is obtained after sintering. The conductivity of the conductor in the conductor paste has high requirements. If noble metals such as silver, gold and palladium are used, the price is high, which is not economical, and it limits the wide use. Copper is low in price and has conductivity second only to silver, which can be used as a substitute for silver conductive material.

[0003] However, the specific surface area of ultra-fine nano copper powder is large, the chemical property is active, and the surface is easy to generate oxide and lose conductivity. In order to obtain high oxidation resistance copper powder, a layer of silver is coated on the surface of copper powder, which improves the conductivity and greatly improves the oxidation resistance of copper powder. The conventional preparation method is not uniform because of the large surface energy of ultra-fine copper powder, easy agglomeration, large specific gravity and easy sinking, the coating layer is not dense, which ultimately leads to poor oxidation resistance, poor conductivity and poor stability, which restricts the application of silver-coated copper conductive powder.

[0004] In addition, most of the methods for coating silver on copper are through displacement reaction to replace copper on the surface of copper particles with silver. In the process, copper is easy to be oxidized, and silver is easy to grow on a certain crystal face, making it difficult to achieve complete coating of copper particles. SUMMARY

[0005] In view of the above problems existing in the prior art, the present application provides a copper-silver composite slurry suitable for 3D printing and a preparation method thereof.

[0006] The present application discloses a copper-silver composite slurry suitable for 3D printing, which comprises copper-silver composite particles, organic ligand and organic carrier, wherein the weight ratio of the organic carrier is 5% to 40%; the copper-silver composite particles comprise copper particles and silver particles, and the copper particles and silver particles are chelated by the organic ligand.

[0007] Further, the molar ratio of copper particles to silver particles in the copper-silver composite slurry is 6-9:4-1.

[0008] Further, the organic ligand accounts for 0.1% to 10% of the total molar amount of the copper-silver composite particles, and the organic ligand is any one or combination of polyvinylpyrrolidone, polyacrylic acid, polyethylene glycol, polyvinyl alcohol, Tween, Span and gelatin.

[0009] Further, the copper particle size is 50 nm to 2 microns, and the silver particle size is 20 to 200 nm.

[0010] Further, the organic carrier is composed of a weak reducing agent, a binder, an organic solvent, a wet dispersant and a surfactant; the weak reducing agent is any one or combination of polyethylene glycol, polyphosphoric acid, citric acid, oxalic acid and ascorbic acid; the binder is any one or combination of polyethylene glycol, ethyl cellulose, hydroxyethyl cellulose, acrylic resin, phenolic resin, polyurethane and epoxy resin; the organic solvent is any one or combination of terpineol, ethylene glycol monomethyl ether, n-butanol, diethylene glycol butyl ether, butyl carbitol acetate, glycerol, isopropyl alcohol and ethylene glycol; the wet dispersant is any one or combination of BYK-190, BYK-192, BYK-193, BYK-110 and deionized water; the surfactant is any one or combination of lauric acid, cetyltrimethylammonium bromide and sodium butanedioate diethyl sulfonate; and the weight ratio of the weak reducing agent, the binder, the organic solvent, the wet dispersant and the surfactant is 5% to 20%: 2% to 10%: 50% to 70%: 20% to 40%: 1% to 5%.

[0011] The application further discloses a preparation method of the copper-silver composite slurry suitable for 3D printing, which comprises the following steps: S1, obtaining a copper particle solution and a silver particle solution; the molar ratio of copper to silver in the copper particle solution and the silver particle solution is 6-9:4-1; S2, uniformly mixing the copper particle solution and the silver particle solution, then adding an organic ligand, and then heating and reacting, wherein the heating temperature is any temperature between 60 and 90 DEG C, and the reaction time is any time length between 0.5 and 2 hours; S3, purifying and drying the product after the reaction in step S2 to obtain a solid intermediate product; and S4, mixing the solid intermediate product obtained in step S3 with an organic carrier, uniformly stirring, and then obtaining the copper-silver composite slurry.

[0012] Further, the organic ligand in step S2 accounts for 0.1% to 10% of the total moles of the copper-silver composite particles, and the organic ligand is any one or combination of polyvinylpyrrolidone, polyacrylic acid, polyethylene glycol, polyvinyl alcohol, Tween, Span and gelatin; the weight ratio of the organic carrier in the copper-silver composite slurry in step S4 is 5% to 40%; the organic carrier is composed of a weak reducing agent, a binder, an organic solvent, a wet dispersant and a surfactant; the weak reducing agent is any one or combination of polyethylene glycol, polyphosphoric acid, citric acid, oxalic acid and ascorbic acid; the binder is any one or combination of polyethylene glycol, ethyl cellulose, hydroxyethyl cellulose, acrylic resin, phenolic resin, polyurethane and epoxy resin; the organic solvent is any one or combination of terpineol, ethylene glycol monomethyl ether, n-butanol, diethylene glycol butyl ether, butyl carbitol acetate, glycerol, isopropyl alcohol and ethylene glycol; the wet dispersant is any one or combination of BYK-190, BYK-192, BYK-193, BYK-110 and deionized water; the surfactant is any one or combination of lauric acid, cetyltrimethylammonium bromide and sodium butanedioate diethyl sulfonate; the weight ratio of the weak reducing agent, the binder, the organic solvent, the wet dispersant and the surfactant is 5% to 20%: 2% to 10%: 50% to 70%: 20% to 40%: 1% to 5%.

[0013] Further, the purification process in step S3 is as follows: after the reaction in step S2 is completed, the temperature is lowered to room temperature, a purification solvent is added, and the mixture is uniformly mixed and then left to settle; after the settling is completed, the precipitate is taken out and subjected to centrifugal treatment; after the treatment, the purification solvent is added again, the mixture is uniformly mixed and then subjected to centrifugal treatment again, and then left to settle; after the settling is completed, the precipitate is taken out; and the drying process in step 3 is as follows: the purified product is dried at any temperature ranging from room temperature to 60°C under vacuum for any time ranging from 1 to 24 hours to obtain a solid intermediate product.

[0014] Further, the purification solution is a mixed liquid of a strong polar organic solvent and a weak polar organic solvent, and the volume ratio of the strong polar organic solvent to the weak polar organic solvent is 1-2:3-6.

[0015] Further, the strong polar organic solvent is any one or combination of methanol, acetone and ethanol; and the weak polar organic solvent is ethyl acetate.

[0016] Further, the copper particle solution and / or the silver particle solution in step S1 is a suspension and / or a colloidal dispersion of copper elementary particles and / or silver elementary particles in a liquid medium; the copper particle size is 50 nm to 2 μm; and the silver particle size is 20 to 200 nm.

[0017] Further, the step S1 copper particle solution preparation process includes the following steps: S111, preparing a reducing agent aqueous solution and a copper salt aqueous solution; S112, adding the copper salt aqueous solution obtained in step S111 into an excess of the reducing agent aqueous solution at a drop rate of any rate between 0.1-4 ml / s, reacting at room temperature, and reacting for any length of time between 0.5-2 h; the copper salt is any one or combination of more than one of copper sulfate pentahydrate, copper hydroxide, copper acetate monohydrate, copper nitrate, copper formate, and copper chloride; the reducing agent is any one or combination of more than one of hydrazine hydrate, hypophosphorous acid, sodium hypophosphite, citric acid, ascorbic acid, isobutanolamine, ethanolamine, and diethanolamine.

[0018] Further, the step 1 silver particle solution preparation process includes the following steps: S121, preparing a silver salt aqueous solution; S122, adding an organic ligand to the silver salt aqueous solution and stirring to mix; the organic ligand is 0.05%-5% of the molar amount of silver particles; S123, adding an excess of a reducing agent to the solution obtained in step S122 at a drop rate of any rate between 0.1-8 ml / s, reacting at room temperature, and reacting for any length of time between 2-12 h; the silver salt is any one or combination of more than one of silver nitrate, silver acetate, silver chlorate, silver citrate, silver carbonate, and silver benzoate; the reducing agent is any one or combination of more than one of hydrazine hydrate, hypophosphorous acid, sodium hypophosphite, citric acid, ascorbic acid, isobutanolamine, ethanolamine, and diethanolamine.

[0019] After the copper nanoparticles and silver nanoparticles are prepared respectively, the organic ligand is added, and the organic ligand is chelated with the two kinds of metal ions through a heating reaction, so that part of the small-size silver nanoparticles are attached to the surface of the large-size copper particles, thereby forming a copper-silver nano mixed metal slurry, and after sintering, the silver particles on the surface of the copper form a conductive path, which can significantly improve the conductive performance, and can effectively reduce the cost of the slurry and the oxidation problem of the copper particles during storage. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The SEM image of the copper-silver composite particles is an embodiment of the present application. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions in the present application will be described below in conjunction with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0022] The application provides a copper-silver composite slurry suitable for 3D printing, which comprises silver particles, copper-silver composite particles and an organic carrier, wherein the weight ratio of the organic carrier is 5-40%; the copper-silver composite particles comprise copper particles and silver particles, and the copper particles and the silver particles are chelated by an organic ligand; the molar ratio of the copper particles to the silver particles in the copper-silver composite slurry is 6-9:4-1; the diameter of the copper particles is 50-2000 nm; and the diameter of the silver particles is 20-200 nm.

[0023] The application further discloses a preparation method of the copper-silver composite slurry suitable for 3D printing, which comprises the following steps:

[0024] S1, obtaining a copper particle solution and a silver particle solution; the molar ratio of copper to silver in the copper particle solution and the silver particle solution is 6-9:4-1;

[0025] S2, mixing the copper particle solution and the silver particle solution uniformly, then adding an organic ligand, and then heating and reacting, wherein the heating temperature is 60-90 DEG C, and the reaction time is 0.5-2 h;

[0026] S3, purifying and drying the product after the reaction in step S2 to obtain a solid intermediate product;

[0027] S4, mixing the solid intermediate product obtained in step S3 with an organic carrier, stirring uniformly to obtain the copper-silver composite slurry.

[0028] The organic ligand is any one or a combination of multiple of polyvinylpyrrolidone, polyacrylic acid, polyethylene glycol, polyvinyl alcohol, Tween, Span and gelatin.

[0029] The weight ratio of the organic carrier to the copper-silver composite slurry is 5% to 40%; the organic carrier is composed of a weak reducing agent, a binder, an organic solvent, a wet dispersant, and a surfactant; the weak reducing agent is any one or a combination of more than one of polyethylene glycol, polyphosphoric acid, citric acid, oxalic acid, and ascorbic acid; the binder is any one or a combination of more than one of polyethylene glycol, ethyl cellulose, hydroxyethyl cellulose, acrylic resin, phenolic resin, polyurethane, and epoxy resin; the organic solvent is any one or a combination of more than one of terpineol, ethylene glycol monomethyl ether, n-butanol, diethylene glycol butyl ether, butyl carbitol acetate, glycerol, isopropyl alcohol, and ethylene glycol; the wet dispersant is any one or a combination of more than one of BYK-190, BYK-192, BYK-193, BYK-110, and deionized water, BYK-190, BYK-192, BYK-193, and BYK-110 being dispersant products of BYK Germany; and the surfactant is any one or a combination of more than one of lauric acid, cetyltrimethylammonium bromide, and sodium butanedioate diethyl sulfonate; the weight ratio of the weak reducing agent, the binder, the organic solvent, the wet dispersant, and the surfactant is 5% to 20%: 2% to 10%: 50% to 70%: 20% to 40%: 1% to 5%.

[0030] The purification process in step 3 is mainly carried out by a purification solution, specifically, after the reaction in step S2 is completed, the temperature is lowered to room temperature, the purification solution is added, and after being mixed uniformly, precipitation is carried out; after the precipitation is completed, the precipitate is taken out and subjected to centrifugal treatment, after the treatment, the purification solution is added again, and after being mixed uniformly, centrifugal treatment is carried out again, and then precipitation is carried out; after the precipitation is completed, the precipitate is taken out.

[0031] The purification solution is a mixed liquid of a strong polar organic solvent and a weak polar organic solvent, and the volume ratio of the strong polar organic solvent to the weak polar organic solvent is 1-2:3-6. The strong polar organic solvent is any one or a combination of more than one of methanol, acetone, and ethanol; and the weak polar organic solvent is ethyl acetate.

[0032] The precipitation time and the rotation speed of the centrifugal treatment can be reasonably selected according to the actual production situation and the equipment situation.

[0033] The drying process in step 3 can select a suitable drying method according to the production demand, and attention should be paid to selecting a drying method that has less influence on the particle size of the product and avoids oxidation of the product, and specifically, vacuum drying can be selected, and the specific drying process can be reasonably selected according to the actual production situation and the equipment situation.

[0034] In step 4, the solid intermediate product is mixed with the organic carrier, and the equipment and process parameters used can be reasonably selected according to the actual production situation and the equipment situation.

[0035] In the selection of the copper particle solution and / or the silver particle solution, a suspension and / or a colloidal dispersion of copper single particles and / or silver single particles in a liquid medium can be directly selected; the copper particle size is 50 nm to 2 μm; and the silver particle size is 20 to 200 nm.

[0036] However, the direct selection of single particles needs to solve the problems of particle oxidation and easy agglomeration of particles in the liquid medium, and therefore the copper particle solution and the silver particle solution can be prepared by a liquid phase reduction method. The complete preparation process is described below in combination with specific examples.

[0037] Example 1

[0038] 1) Preparation of a copper solution

[0039] (1) 21 g of secondary phosphoric acid was weighed and mixed with 20 g of deionized water to form a uniform solution;

[0040] (2) 17.5 g (0.07 mol) of copper sulfate pentahydrate was weighed and dissolved in 40 g of deionized water to form a solution;

[0041] (3) The solution in (1) was added dropwise to the solution in (2) at a rate of 0.4 ml / s, and stirred at 65°C for 1 h to form a red-brown solution.

[0042] 2) Preparation of a silver solution

[0043] (1) 5.1 g of silver nitrate (0.03 mol) was dissolved in 20 g of deionized water, and 0.75 g of PAA (MW 5000) was added and stirred to mix well;

[0044] (2) 40 ml of ascorbic acid solution (2 mol / l) was added dropwise to (1) at a rate of 1 ml / s, and a yellow-gray solution was formed after reaction at room temperature for 5 h.

[0045] 3) Preparation of a copper-silver paste

[0046] (1) The copper particle solution and the silver particle solution were mixed and stirred, and 3.5 g of PAA (MW 5000) was added and reacted at 65°C for 1 h;

[0047] (2) The temperature was lowered to room temperature, 300 ml of ethyl acetate and 150 ml of methanol were added, and the mixture was allowed to stand and precipitate;

[0048] (3) The supernatant was discarded, the precipitate was centrifuged at 9000 r / min, 20 ml of ethyl acetate and 10 ml of methanol were added, and the mixture was ultrasonically mixed and then centrifuged at 9000 r / min again, and the precipitate was dried;

[0049] (4) 40°C vacuum drying for 12h, 3g organic carrier is added, the ratio of organic carrier is polyphosphoric acid: acrylic resin: BYK-192: hexadecyl trimethyl ammonium bromide: glycerol = 1:0.8:3.5:0.2:6.5, the particles and the organic carrier are fully dispersed by mixing in a mixer for multiple times at 2000r / min, forming copper-silver paste.

[0050] Example 2

[0051] 1) Preparation of copper solution

[0052] (1) 16g of hydrazine hydrate solution is weighed and mixed with 20g of deionized water to form a uniform solution;

[0053] (2) 17.5g (0.07mol) of copper sulfate pentahydrate is weighed and dissolved in 40g of deionized water to form a uniform solution;

[0054] (3) The solution described in (2) is added dropwise to the solution described in (1) at a rate of 0.5ml / s, and the red-brown solution is formed at room temperature for 1h.

[0055] 2) Preparation of silver solution

[0056] (1) 5.1g of silver nitrate (0.03mol) is taken and dissolved in 20g of deionized water, and 0.825g of PVP (MW 5500) is added and stirred thoroughly;

[0057] (2) 12g of diethanolamine is added dropwise to (1) at a rate of 1ml / s, and a brown-yellow solution is formed after 6h of reaction at room temperature.

[0058] 3) Preparation of copper-silver paste

[0059] (1) The copper particle solution and the silver particle solution are mixed and stirred, and 3.85g of PVP (MW 5500) is added and reacted at 65°C for 1h;

[0060] (2) After cooling to room temperature, 300ml of ethyl acetate and 150ml of methanol are added, and the precipitate is allowed to settle;

[0061] (3) The supernatant is discarded, and the precipitate is centrifuged at 9000r / min, then 20ml of ethyl acetate and 10ml of acetone are added and ultrasonically mixed to form a uniform solution, which is then centrifuged at 9000r / min, and the precipitate is dried;

[0062] (4) 40°C vacuum drying for 6h, 3g of organic carrier is added, the ratio of organic carrier is polyethylene glycol PEG300: epoxy resin: BYK-193: hexadecyl trimethyl ammonium bromide: ethylene glycol = 1:0.8:3.5:0.2:6.5, the particles and the organic carrier are fully dispersed by mixing in a mixer for multiple times at 1500r / min, forming copper-silver paste.

[0063] In addition to the copper salt and silver salt selected in Examples 1 and 2, the copper salt can also be any one or a combination of copper sulfate pentahydrate, copper hydroxide, copper acetate monohydrate, copper nitrate, copper formate, and copper chloride; and the silver salt can also be any one or a combination of silver nitrate, silver acetate, silver chlorate, silver citrate, silver carbonate, and silver benzoate.

[0064] In addition to the hydrazine hydrate, hypophosphorous acid, diethanolamine, and citric acid used in the examples, any one or a combination of sodium hypophosphite, ascorbic acid, isobutanolamine, and ethanolamine can also be used.

[0065] In terms of the ratio of the specific copper salt and silver salt to the reducing agent, the reducing agent is required to be in excess to ensure complete reaction, and the specific ratio can be reasonably set according to the selection of raw materials.

[0066] Comparative Example 1

[0067] The preparation of the copper solution and the silver solution was the same as in Example 1.

[0068] 3) Preparation of copper-silver slurry

[0069] (1) After mixing and stirring the copper particle solution and the silver particle solution, the mixture was reacted at 65°C for 0.5 h;

[0070] (2) The temperature was lowered to room temperature, 300 ml of ethyl acetate and 150 ml of methanol were added, and the mixture was allowed to stand to precipitate;

[0071] (3) The supernatant was discarded, the precipitate was centrifuged at 9000 r / min, 20 ml of ethyl acetate and 10 ml of methanol were added, the mixture was uniformly ultrasonicated, and then centrifuged again at 9000 r / min, and the precipitate was air-dried;

[0072] (4) Vacuum drying at 40°C for 12 h, adding 3 g of organic carrier, the ratio of the organic carrier being polyphosphoric acid: acrylic resin: BYK-192: cetyltrimethylammonium bromide: glycerol = 1:0.8:3.5:0.2:6.5, mixing the slurry multiple times in a slurry mixer at 2000 r / min to fully disperse the particles and the organic carrier, and forming a copper-silver slurry.

[0073] Performance test experimental method:

[0074] (1) Particle size observation: using a scanning electron microscope to characterize the size and morphology of the copper nanoparticles: ① A small amount of slurry was diluted in deionized water or an organic solvent at a ratio of 1:500; ② The diluted solution was ultrasonically dispersed, a small amount was taken with a dropper and added to the surface of a silicon wafer, and the excess solvent was removed by heating; ③ After sample preparation and gold spraying, the sample was observed to obtain size and morphology images of the copper nanoparticles.

[0075] (2) Resistivity test: using the FT-340 four-probe square resistance tester to test the resistivity of the slurry: ① The prepared conductive slurry was coated on the glass substrate by a coating machine, and sintered at 260°C for 1h in a nitrogen atmosphere to obtain a conductive copper film; ② The thickness of the metal film sample after high-temperature sintering was measured by a step tester; ③ Set the corresponding parameters in the square resistance tester, and adjust the four probes to lightly touch the sample vertically; ④ Record the resistivity data after the reading is stable.

[0076] (3) Printing test: using the Nordson EFD dispenser to test the printing of the slurry: ① The prepared slurry was filled into a 3ml tube and a 20μm glass needle was connected, and the whole device was filled into a pressure pen and connected to the dispenser; ② The pressure was adjusted to 140psi, and the needle was placed in the material box; ③ Record the material output time for 10h, and if the material is blocked within 10h, it is judged as blocked.

[0077] The relevant indicators of the products prepared in the above examples and comparative examples were detected to obtain the following table.

[0078] Table 1 Resistivity of slurry after sintering at 260°C and printing test of each slurry

[0079]

[0080] From Table 1, it can be seen that in Comparative Example 1, since no organic ligand is added after mixing the two metal solutions, the prepared copper-silver particles cannot be tightly chelated together, so that the surface of the copper particles is exposed to the air and reacts with oxygen in the air, resulting in serious oxidation and reduced conductivity; The surface of copper and silver is not protected, and the particles are easy to agglomerate to form large particles, which can easily block the material during printing, and cannot meet the printing demand below 20μm. In Example 1, an organic ligand is added, which firmly anchors the silver particles on the surface of the copper particles. After heating and sintering, the silver particles form a dense silver layer, achieving good densification effect, so that the copper particles are completely isolated from the air, and the conductivity is obviously improved; And the particles chelated by the organic ligand will not agglomerate during the later treatment process, which can meet the printing demand below 20μm.

[0081] From Examples 1 and 2, it can be seen that the selection of different reducing agents and organic ligands required by the present application in the preparation process has certain influence on the performance of the final product, but it is obviously better than Comparative Example 1.

[0082] On the basis of the above examples and comparative examples, the present application also sets up a plurality of different examples to illustrate the actual influence or technical effect of the process points involved in the present application. The relevant parameter settings of each example and comparative example are shown in the following table.

[0083] Table 2 Relevant parameter settings of each example and comparative example

[0084]

[0085] The product-related indexes of the above examples and comparative examples were detected to obtain the following table.

[0086]

[0087]

[0088] Examples 3, 4 and Comparative Example 2 can illustrate the influence of the dropping speed on the particle size, and in the present application, the particle size of the copper and silver particles needs to be controlled during the preparation process to achieve a better particle size ratio of the copper and silver particles, so as to improve the covering effect of the silver particles.

[0089] Examples 5, 6 and Comparative Example 3 illustrate the heating condition of S2, that is, the copper particle solution, the silver particle solution and the organic ligand are mixed and then heated for reaction, and if the heating temperature is too high, the copper and silver particles may be aggregated, which affects the effect of the slurry.

[0090] Examples 7, 8 and Comparative Example 4 can illustrate the influence of the copper-silver molar ratio, and in the case of meeting the good covering of the silver particles, the amount of the silver particles is less better from the cost point of view, but in the actual production, the amount of the silver particles needs to consider the particle size of the copper and silver particles, the complete covering amount of the silver particles and other parameters, and the present application preferably ranges from 6-9:4-1 to achieve the balance of the cost and performance.

[0091] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a copper-silver composite paste suitable for 3D printing, characterized in that, The method comprises the following steps: S1, obtaining a copper particle solution and a silver particle solution; the molar ratio of copper to silver in the copper particle solution and the silver particle solution is 6-9:4-1; S2, mixing the copper particle solution and the silver particle solution uniformly, then adding an organic ligand, and then heating and reacting, the heating temperature is any temperature between 60-90℃, and the reaction time is any time length between 0.5-2h; S3, obtaining a solid intermediate product after purifying and drying the product after the reaction in step S2; S4, mixing the solid intermediate product obtained in step S3 with an organic carrier, stirring uniformly, and then obtaining a copper-silver composite slurry; The preparation process of the copper particle solution in step S1 comprises the following steps: S111, preparing a reducing agent aqueous solution and a copper salt aqueous solution; S112, adding the copper salt aqueous solution obtained in step S111 into an excessive reducing agent aqueous solution dropwise, the dropwise adding rate is any rate between 0.1-2ml / s; The preparation process of the silver particle solution in step S1 comprises the following steps: S121, preparing a silver salt aqueous solution; S122, adding an organic ligand into the silver salt aqueous solution, and stirring uniformly; S123, adding an excessive reducing agent into the solution obtained in step S122 dropwise at a rate of any rate between 0.1-8ml / s.

2. The method for preparing a copper-silver composite paste suitable for 3D printing according to claim 1, characterized in that, In step S2, the organic ligand accounts for 0.1%-10% of the total molar amount of the copper-silver composite particles, and the organic ligand is any one or combination of polyvinylpyrrolidone, polyacrylic acid, polyethylene glycol, polyvinyl alcohol, Tween, Span and gelatin; in step S4, the weight ratio of the organic carrier to the copper-silver composite slurry is 5%-40%; the organic carrier is composed of a weak reducing agent, a binder, an organic solvent, a wet dispersant and a surfactant; the weak reducing agent is any one or combination of polyethylene glycol, polyphosphoric acid, citric acid, oxalic acid and ascorbic acid; the binder is any one or combination of polyethylene glycol, ethyl cellulose, hydroxyethyl cellulose, acrylic resin, phenolic resin, polyurethane and epoxy resin; the organic solvent is any one or combination of terpineol, ethylene glycol monomethyl ether, n-butanol, diethylene glycol butyl ether, butyl carbitol acetate, glycerol, isopropyl alcohol and ethylene glycol; the wet dispersant is any one or combination of BYK-190, BYK-192, BYK-193, BYK-110 and deionized water; the surfactant is any one or combination of lauric acid, cetyltrimethylammonium bromide and sodium butanedioate sulfonate; the weight ratio of the weak reducing agent, the binder, the organic solvent, the wet dispersant and the surfactant is 5%-20%:2%-10%:50%-70%:20%-40%:1%-5%.

3. The method for preparing a copper-silver composite paste for 3D printing according to claim 1, wherein In step S3, after the reaction in step S2 is completed, the temperature is lowered to room temperature, a purification solvent is added, and then the mixture is left to stand after being stirred uniformly; after the precipitation is completed, the precipitate is taken out and centrifuged; after the treatment, the purification solvent is added again, the mixture is stirred uniformly, and then centrifuged again; after the precipitation is completed, the precipitate is taken out; The drying process in step S3 is vacuum drying at any temperature between room temperature and 60℃ for any time between 1 and 24 hours to obtain a solid intermediate product.

4. The method for preparing a copper-silver composite paste suitable for 3D printing according to claim 3, characterized in that, The purification solvent is a mixed liquid of a strong polar organic solvent and a weak polar organic solvent, wherein the volume ratio of the strong polar organic solvent to the weak polar organic solvent is 1-2:3-6.

5. The method for preparing a copper-silver composite paste suitable for 3D printing according to claim 4, characterized in that, The strong polar organic solvent is any one or a combination of methanol, acetone and ethanol; the weak polar organic solvent is ethyl acetate.

6. The method for preparing a copper-silver composite paste suitable for 3D printing according to claim 1, characterized in that, The copper particle solution and / or the silver particle solution in step S1 is a suspension and / or a colloidal dispersion of copper and / or silver particles in a liquid medium; the copper particle size is 50nm-2μm; the silver particle size is 20-200nm.

7. The method for preparing a copper-silver composite paste suitable for 3D printing according to claim 1, characterized in that, The preparation process of the copper particle solution further comprises the following steps: After the aqueous copper salt solution is added dropwise into the excess aqueous reducing agent solution, normal temperature reaction is performed for any time between 0.5 and 2 hours; The copper salt is any one or a combination of copper sulfate pentahydrate, copper hydroxide, copper acetate monohydrate, copper nitrate, copper formate and copper chloride; the reducing agent is any one or a combination of hydrazine hydrate, hypophosphorous acid, sodium hypophosphite, citric acid, ascorbic acid, isobutanolamine, ethanolamine and diethanolamine.

8. The method for preparing a copper-silver composite paste suitable for 3D printing according to claim 1, characterized in that, The preparation process of the silver particle solution further comprises the following steps: The organic ligand is 0.05%-5% of the molar amount of the silver particles; After the excess reducing agent is added dropwise into the solution obtained in step S122, normal temperature reaction is performed for any time between 2 and 12 hours; The silver salt is any one or a combination of silver nitrate, silver acetate, silver chlorate, silver citrate, silver carbonate and silver benzoate; the reducing agent is any one or a combination of hydrazine hydrate, hypophosphorous acid, sodium hypophosphite, citric acid, ascorbic acid, isobutanolamine, ethanolamine and diethanolamine.

9. A copper-silver composite paste suitable for 3D printing, prepared according to the method of claim 1. The copper-silver composite slurry comprises copper-silver composite particles, an organic ligand and an organic carrier, wherein the weight ratio of the organic carrier is 5%-40%; the copper-silver composite particles comprise copper particles and silver particles, and the copper particles and the silver particles are chelated by the organic ligand. 10.The copper-silver composite paste for 3D printing according to claim 9, wherein, The molar ratio of the copper particles to the silver particles in the copper-silver composite slurry is 6-9:4-1. 11.The copper-silver composite paste for 3D printing according to claim 9, wherein, The organic ligand in the copper-silver composite particles accounts for 0.1%-10% of the total molar amount of the copper-silver composite particles, and the organic ligand is any one or a combination of polyvinylpyrrolidone, polyacrylic acid, polyethylene glycol, polyvinyl alcohol, Tween, Span and gelatin.

12. The copper-silver composite paste as claimed in claim 9, wherein, The copper particle size is 50nm-2μm; the silver particle size is 20-200nm.

13. The copper-silver composite paste as claimed in claim 9, wherein, The organic carrier is composed of a weak reducing agent, a binder, an organic solvent, a wet dispersant and a surfactant; the weak reducing agent is any one or a combination of more of polyethylene glycol, polyphosphoric acid, citric acid, oxalic acid and ascorbic acid; the binder is any one or a combination of more of polyethylene glycol, ethyl cellulose, hydroxyethyl cellulose, acrylic resin, phenolic resin, polyurethane and epoxy resin; the organic solvent is any one or a combination of more of terpineol, ethylene glycol monomethyl ether, n-butanol, diethylene glycol butyl ether, butyl carbitol acetate, glycerol, isopropyl alcohol and ethylene glycol; the wet dispersant is any one or a combination of more of BYK-190, BYK-192, BYK-193, BYK-110 and deionized water; the surfactant is any one or a combination of more of lauric acid, cetyltrimethylammonium bromide and sodium butanedioate diethyl sulfonate; and the weight ratio of the weak reducing agent, the binder, the organic solvent, the wet dispersant and the surfactant is 5%-20%:2%-10%:50%-70%:20%-40%:1%-5%.

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