Multi-element copper powder synergistic high-stability photocuring copper slurry and preparation method thereof

Abstract

The invention discloses multi-element copper powder synergistic high-stability photocuring copper paste and a preparation method thereof, and belongs to the technical field of additive manufacturing. The slurry comprises 73%-94% of metal powder, 0.17%-0.8% of small organic molecules, 3%-15% of a reactive diluent, 0.5%-8% of an oligomer, 0.2%-1.3% of a photoinitiator, 0.8%-3.5% of a dispersing agent and 0.05%-0.5% of an antioxidant. The metal powder is composed of nano copper powder, spherical micron copper powder and flaky copper powder. During preparation, the copper powder is subjected to V-shaped mixing and then treated with an organic micromolecule ethanol solution to form a surface passivation layer, and then the surface passivation layer is mixed with a resin premixed solution containing the antioxidant through a homogenizer. The stability and sintering performance of the slurry are synergistically improved through the multi-element copper powder, the oxidation resistance is synergistically enhanced through the small organic molecule passivation layer and the antioxidant, and the additive manufacturing method is suitable for additive manufacturing of high-precision metal parts.

Description

Technical Field

[0001] This application belongs to the field of additive manufacturing technology, and specifically relates to a highly stable photocurable copper paste with synergistic effects of multiple copper powders and its preparation method. Background Technology

[0002] In recent years, the electronic components and semiconductor industries have developed rapidly, leading to a continuous increase in demand for high-performance metallic materials. Copper, with its excellent conductivity, superior oxidation resistance, and corrosion resistance, has become an indispensable key material in this field. In the manufacturing of printed circuit boards (PCBs), microprocessors, chip interconnects, and high-power-density radio frequency (RF) modules, copper plays a crucial role in significantly reducing signal loss and improving energy efficiency. However, when faced with the manufacturing requirements of complex curved surfaces and precision structural parts, traditional processing methods have significant shortcomings in terms of forming accuracy, structural freedom, and process adaptability, restricting the application of copper in a wider range of fields.

[0003] Photopolymer 3D printing technology, as a high-precision additive manufacturing method, has opened up new pathways for metal material processing. This technology mixes metal powder with photosensitive resin to form a photopolymer slurry, which is then cured layer by layer to form a green body. After debinding and sintering, high-precision, high-density metal parts are produced, demonstrating significant technological potential. In the field of photopolymer copper slurry, numerous studies and patents have emerged. Patent CN116809921A relates to a highly photosensitive slurry for pure copper photopolymer 3D printing and its preparation method. It proposes using a combination of α-aminoketone and thioxanthone derivatives as a photoinitiator system. Utilizing the high molar extinction coefficient of thioxanthone in the 360nm–405nm wavelength range, it competitively absorbs ultraviolet light and undergoes energy transfer with α-aminoketone, thereby improving photopolymerization efficiency. However, this method still fails to effectively solve the problems of poor slurry stability and easy oxidation. Furthermore, excessive use of photoinitiators increases costs and introduces impurities. Patent CN104658707A relates to a method for preparing photocurable copper electronic paste, which uses hydrazine hydrate and polyvinylpyrrolidone (PVP) to pretreat copper powder to enhance its dispersibility and stability in the paste. However, this process involves toxic reagents, posing challenges to both the environment and large-scale production. In summary, existing photocurable copper paste technologies still generally suffer from problems such as easy oxidation, insufficient stability, low curing efficiency, poor environmental performance, and difficulty in adapting to large-scale production. Summary of the Invention

[0004] This application provides a highly stable photocurable copper paste with synergistic effects of multiple copper powders and its preparation method, aiming to solve the problems of easy oxidation, poor stability and low curing efficiency of copper pastes in the prior art.

[0005] To achieve the above objectives, this application provides a highly stable photocurable copper paste with synergistic effects of multiple copper powders. The photocurable copper paste, by mass ratio, comprises 73%–94% metal powder, 0.17%–0.8% organic small molecules, 3%–15% reactive diluent, 0.5%–8% oligomer, 0.2%–1.3% photoinitiator, 0.8%–3.5% dispersant, and 0.05%–0.5% antioxidant.

[0006] In one embodiment, the metal powder is composed of nano copper powder with a particle size distribution of 5 μm to 500 μm, spherical micro copper powder with a particle size distribution of 1 μm to 5 μm, and flake copper powder with a thickness of 0.1 μm to 0.5 μm and a planar size of 5 μm to 40 μm.

[0007] In one embodiment, the mass percentage of the nano-copper powder in the slurry is 10% to 20%, the mass percentage of the spherical micron copper powder in the slurry is 30% to 60%, and the mass percentage of the flake copper powder in the slurry is 20% to 40%.

[0008] In one embodiment, the organic small molecule is one of benzotriazole, 2-mercaptobenzimidazole, and citric acid; the reactive diluent is selected from one or more combinations of polyethylene glycol diacrylate, isobornyl acrylate, and 1,6-hexanediol diacrylate; and the photoinitiator is selected from one or more combinations of di(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-dimethoxy-2-phenylacetophenone, trimethylbenzoyl diphenylphosphine oxide, and 1-hydroxycyclohexylbenzophenone.

[0009] In one embodiment, the oligomer is selected from one or more combinations of epoxy acrylate, polyurethane acrylate, and polyester acrylate; the antioxidant is selected from one or more combinations of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, diphenyl pentaerythritol diphosphite, and bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite.

[0010] In one embodiment, the dispersant is selected from one or more combinations of Solsperse 41000, Solsperse 61000, EFKA-4580, Tego 685, and EFKA-4310.

[0011] A method for preparing a highly stable photocurable copper paste with synergistic effects of multiple copper powders includes the following steps: S1. Add the metal powder to the V-type mixer according to the proportion to obtain a uniformly mixed copper powder mixture; S2. Dissolve the small organic molecules in an ethanol solution according to the specified ratio to obtain an ethanol solution of the small organic molecules; S3. The organic small molecule ethanol solution is added to the V-type mixer and mixed with the copper powder mixture. After the ethanol has completely evaporated, modified copper powder with a surface passivation layer is formed. S4. Mix the reactive diluent and photoinitiator according to the ratio until they are miscible. Then add the oligomer and antioxidant in sequence and mix. After mixing, the copper paste premix is ​​obtained. S5. Add the dispersant to the copper paste premix according to the ratio and mix thoroughly to obtain a copper paste mixture. S6. Add the modified copper powder and the copper paste mixture to a homogenizer, start the homogenizer to mix them evenly, and obtain a highly stable photocurable copper paste.

[0012] In one embodiment, in steps S1 and S3, the rotation speed of the V-type mixer is controlled between 100 r / min and 300 r / min, and the mixing time is between 10 min and 60 min.

[0013] In one embodiment, the mass ratio of the copper powder mixture to the ethanol solution is 1:0.1 to 0.5.

[0014] In one embodiment, in step S6, the homogenization program of the homogenizer is set as follows: first, the speed is increased to 1000 r / min to 1500 r / min for 30 s to 60 s, then the speed is increased to 2000 r / min to 3500 r / min for 50 s to 90 s, and finally the speed is increased to 2500 r / min to 3000 r / min for 10 s to 40 s.

[0015] Compared with the prior art, the beneficial effects of this application are as follows: 1. This invention utilizes a multi-component copper powder system to significantly improve the stability and sintering performance of photocurable copper paste through the synergistic effect of its components. The system comprises nano-copper powder, spherical micron-sized copper powder, and flake-shaped copper powder. Nano-copper powder possesses an extremely high specific surface area, effectively filling the fine pores in the photocurable copper paste, greatly enhancing system stability. It also preferentially participates in the reaction during photocuring and sintering, promoting interconnection and sintering between copper powders. The spherical micron-sized copper powder has a low angle of repose, and its regular morphology optimizes the packing structure through rolling rearrangement during curing and sintering, thereby enhancing the photocuring penetration depth and the conductivity of the copper parts. The flake-shaped copper powder, with its large specific surface area and unique two-dimensional structure, oriented in the paste to form a highly efficient two-dimensional anti-settling network, simultaneously inhibiting the propagation of curing cracks and improving the mechanical properties and electrical stability of the copper parts.

[0016] 2. This invention significantly enhances the antioxidant properties of photocurable copper paste and green body by constructing a passivation layer on the surface of copper powder using small organic molecules and synergistically combining it with antioxidants in the photosensitive resin. The small organic molecules encapsulate the copper powder surface, and the N, S, and O atoms they contain form stable coordination bonds with the copper powder surface, constructing a dense monomolecular protective film that effectively blocks moisture and oxygen erosion, greatly improving the antioxidant capacity of the copper powder. Simultaneously, hindered phenolic and phosphite antioxidants are introduced into the photosensitive resin system to efficiently scavenge peroxide free radicals generated within the paste, blocking oxidation chain reactions. The synergistic effect of the organic passivation layer on the copper powder surface and the antioxidants in the paste significantly improves the overall antioxidant properties of the photocurable paste and its green body. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is an overall schematic diagram of the photopolymerization molding method for preparing high-precision metal green bodies provided in this application. Figure 2 Storage state diagram of the highly stable photocurable copper paste with synergistic effects of multiple copper powders provided in this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0020] See Figures 1 to 2 As shown, the high-stability photocurable copper paste with synergistic effects of multiple copper powders provided in this application comprises, by mass ratio, 73%–94% metal powder, 0.17%–0.8% organic small molecules, 3%–15% reactive diluent, 0.5%–8% oligomer, 0.2%–1.3% photoinitiator, 0.8%–3.5% dispersant, and 0.05%–0.5% antioxidant.

[0021] The metal powder consists of nano-copper powder with a particle size distribution of 5μm to 500μm, spherical micron-sized copper powder with a particle size distribution of 1μm to 5μm, and flake-shaped copper powder with a thickness of 0.1μm to 0.5μm and a planar size of 5μm to 40μm. The mass percentage of nano-copper powder in the slurry is 10% to 20%, the mass percentage of spherical micron-sized copper powder in the slurry is 30% to 60%, and the mass percentage of flake-shaped copper powder in the slurry is 20% to 40%.

[0022] The organic small molecule is one of benzotriazole, 2-mercaptobenzimidazole, and citric acid; the reactive diluent is one or more combinations of polyethylene glycol diacrylate, isobornyl acrylate, and 1,6-hexanediol diacrylate; the photoinitiator is one or more combinations of di(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-dimethoxy-2-phenylacetophenone, trimethylbenzoyl diphenylphosphine oxide, and 1-hydroxycyclohexylbenzophenone. The oligomer is one or more combinations of epoxy acrylate, polyurethane acrylate, and polyester acrylate; the antioxidant is one or more combinations of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, diphenylpentaerythritol diphosphite, and bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite.

[0023] The dispersant is selected from one or more combinations of Solsperse 41000, Solsperse 61000, EFKA-4580, Tego 685, and EFKA-4310.

[0024] The method for preparing a highly stable photocurable copper paste with synergistic effects of multiple copper powders provided in this application includes the following steps: S1. Add the metal powder to the V-type mixer according to the proportion to obtain a uniformly mixed copper powder mixture; S2. Dissolve the small organic molecules in an ethanol solution according to the specified ratio to obtain an ethanol solution of the small organic molecules; S3. Add the organic small molecule ethanol solution to a V-type mixer and mix it with the copper powder mixture. After the ethanol has completely evaporated, modified copper powder with a surface passivation layer is formed. The mass ratio of the copper powder mixture to the ethanol solution is 1:0.1 to 0.5.

[0025] S4. Mix the reactive diluent and photoinitiator according to the ratio until they are miscible. Then add the oligomer and antioxidant in sequence and mix. After mixing, the copper paste premix is ​​obtained. S5. Add the dispersant to the copper paste premix according to the ratio and mix thoroughly. After thorough mixing, a copper paste mixture is obtained. S6. Add the modified copper powder and copper paste mixture to the homogenizer, start the homogenizer to mix them evenly, and obtain a highly stable photocurable copper paste.

[0026] In steps S1 and S3, the rotation speed of the V-type mixer is controlled between 100 r / min and 300 r / min, and the mixing time is between 10 min and 60 min.

[0027] In step S6, the homogenization program of the homogenizer is set as follows: first, the speed is increased to 1000 r / min to 1500 r / min for 30s to 60s, then the speed is increased to 2000 r / min to 3500 r / min for 50s to 90s, and finally the speed is increased to 2500 r / min to 3000 r / min for 10s to 40s.

[0028] The present invention will be further described below with reference to specific embodiments. It should be understood that conventional instruments and equipment in the art are used in the following embodiments. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Various raw materials used in the following embodiments are all conventional commercially available products with specifications in the art, unless otherwise stated. In the specification of this invention and in the following embodiments, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0029] Example 1

[0030] 87% of nano-copper powder, spherical micron-sized copper powder, and flake-shaped copper powder were added to a V-type mixer at a mass ratio of 10:50:40 and mixed at 100 rpm for 40 minutes to obtain a homogeneous copper powder mixture. 0.35% benzotriazole was dissolved in an ethanol solution, with the mass ratio of the copper powder mixture to the ethanol solution being 1:0.3, to obtain an organic small-molecule ethanol solution. This organic small-molecule ethanol solution was added to the V-type mixer and mixed with the copper powder mixture. After the ethanol completely evaporated, modified copper powder with a surface passivation layer was formed.

[0031] Subsequently, 7% of the reactive diluent polyethylene glycol diacrylate, 0.3% of the photoinitiator bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 0.2% of the photoinitiator 2,2-dimethoxy-2-phenylacetophenone were mixed and miscible. Then, 2.45% of epoxy acrylate resin, 0.1% of the antioxidant 2,6-di-tert-butyl-p-cresol, and 0.1% of the antioxidant tris(2,4-di-tert-butylphenyl) phosphite were added sequentially to obtain the copper paste premix.

[0032] Add 2.5% of dispersant Solsperse 41000 to the copper paste premix and mix thoroughly to obtain a copper paste mixture. Finally, add the modified copper powder and copper paste mixture to a homogenizer for homogenization.

[0033] The homogenizer's mixing program is set as follows: first, the speed is 1000 r / min for 40 seconds, then the speed is increased to 2500 r / min for 70 seconds, and finally the speed is adjusted to 1500 r / min for 30 seconds. After mixing, a uniform and stable high-stability photocurable copper paste is obtained.

[0034] like Figure 2 As shown, the photocurable copper paste prepared in Example 1 maintained good fluidity and dispersibility after 30 days of storage, without agglomeration or sedimentation, and the surface showed no oxidation or discoloration, indicating that it has excellent long-term storage stability.

[0035] Example 2

[0036] 94% of nano-copper powder, spherical micron-sized copper powder, and flake-shaped copper powder were added to a V-type mixer at a mass ratio of 15:45:40 and mixed at a rate of 300 r / min for 30 min. After mixing, a uniformly mixed copper powder mixture was obtained. 0.5% of 2-mercaptobenzimidazole was dissolved in an ethanol solution, wherein the mass ratio of the copper powder mixture to the ethanol solution was 1:0.5, to obtain an organic small molecule ethanol solution. The organic small molecule ethanol solution was added to the V-type mixer and mixed with the copper powder mixture. After the ethanol was completely evaporated, modified copper powder with a surface passivation layer was formed.

[0037] Subsequently, 2% of the reactive diluent polyisoborneol acrylate, 1% of the reactive diluent 1,6-hexanediol diacrylate, 0.1% of the photoinitiator 1-hydroxycyclohexyl benzophenone, and 0.1% of the photoinitiator 2,2-dimethoxy-2-phenylacetophenone were mixed and dissolved. Then, 1% of polyurethane acrylic resin, 0.2% of the antioxidant pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), and 0.1% of the antioxidant bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite were added sequentially and mixed evenly to obtain the copper paste premix.

[0038] 1% of dispersant Solsperse 61000 was added to the copper paste premix and thoroughly mixed to obtain a copper paste mixture. Finally, the modified copper powder and the copper paste mixture were placed in a homogenizer for homogenization. The homogenizer's mixing program was set as follows: first, the speed was 1500 r / min for 30 seconds, then increased to 3000 r / min for 80 seconds, and finally decreased to 2500 r / min for 20 seconds. After mixing, a uniform photocurable copper paste was obtained.

[0039] Example 3

[0040] 73% of nano-copper powder, spherical micron-sized copper powder, and flake-shaped copper powder were added to a V-type mixer at a mass ratio of 20:50:30 and mixed at 200 r / min for 60 min, resulting in a homogeneous copper powder mixture. 0.17% citric acid was dissolved in an ethanol solution, with the copper powder mixture being mixed to the ethanol solution at a mass ratio of 1:0.1, yielding an organic small-molecule ethanol solution. This organic small-molecule ethanol solution was added to the V-type mixer and blended with the copper powder mixture. After the ethanol completely evaporated, modified copper powder with a surface passivation layer was formed.

[0041] Subsequently, 8% of the reactive diluent polyethylene glycol diacrylate, 7% of the reactive diluent 1,6-hexanediol diacrylate, 0.65% of the photoinitiator 2,2-dimethoxy-2-phenylacetophenone, and 0.65% of the photoinitiator trimethylbenzoyl diphenylphosphine oxide were mixed and miscible. Then, 6.53% of polyester acrylic resin, 0.25% of the antioxidant pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), and 0.25% of the antioxidant diphenylpentaerythritol diphosphite were added sequentially and mixed evenly to obtain the copper paste premix.

[0042] 1.75% of dispersant Solsperse 41000 and 1.75% of dispersant EFKA-4310 were added to the copper paste premix and thoroughly mixed to form a copper paste mixture. The modified copper powder and copper paste mixture were then placed in a homogenizer for homogenization. The homogenizer's mixing program was set as follows: first, the speed was 1200 r / min for 60 seconds, then increased to 3000 r / min for 50 seconds, and finally decreased to 1000 r / min for 40 seconds. After mixing, a uniform photocurable copper paste was obtained.

[0043] Example 4

[0044] 86% of nano-copper powder, spherical micron-sized copper powder, and flake-shaped copper powder were added to a V-type mixer at a mass ratio of 15:60:25 and mixed at 100 r / min for 60 min, resulting in a homogeneous copper powder mixture. 0.8% of the organic small molecule 2-mercaptobenzimidazole was dissolved in an ethanol solution, with the mass ratio of the copper powder mixture to the ethanol solution being 1:0.1, to obtain an organic small molecule ethanol solution. This organic molecule ethanol solution was added to the V-type mixer and mixed with the copper powder mixture. After the ethanol completely evaporated, modified copper powder with a surface passivation layer was formed.

[0045] Subsequently, 5% of the reactive diluent isoborneol acrylate, 5% of the reactive diluent 1,6-hexanediol diacrylate, 0.45% of the photoinitiator di(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 0.45% of the photoinitiator trimethylbenzoyl diphenylphosphine oxide were mixed and miscible. Then, 4% of the oligomeric polyether acrylic resin, 0.2% of the antioxidant pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), and 0.2% of the antioxidant bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite were added sequentially to obtain the copper paste premix.

[0046] 1.5% of dispersant Tego 685 and 1.5% of dispersant EFKA-4580 were added to the copper paste premix and thoroughly mixed to form a copper paste mixture. The modified copper powder and copper paste mixture were then placed in a homogenizer for homogenization. The homogenizer's mixing program was set as follows: first, the speed was increased to 1000 r / min for 60 seconds, then increased to 2500 r / min for 60 seconds, and finally decreased to 1000 r / min for 40 seconds. After mixing, a uniform photocurable copper paste was obtained.

[0047] It should be noted that in Examples 1 to 4 above, a multi-scale composite structure of nano-copper powder, spherical micron-sized copper powder, and flake-shaped copper powder was constructed. The nano-copper powder has an extremely high specific surface area, which can effectively fill micropores and defects in the system, enhancing density and significantly improving system stability. Simultaneously, it preferentially reacts during photocuring and sintering, promoting interconnection between copper particles and accelerating the sintering densification process. The spherical micron-sized copper powder, due to its good flowability and low angle of repose, easily undergoes rolling rearrangement during curing, optimizing the particle packing structure and improving the photocuring penetration depth and the final conductivity of the copper part. The flake-shaped copper powder, with its large specific surface area and two-dimensional planar structure, forms a directional network structure in the slurry, effectively inhibiting copper powder sedimentation and hindering crack propagation paths, significantly enhancing the mechanical strength and electrical stability of the sintered body.

[0048] Furthermore, by constructing a passivation layer on the surface of copper powder using small organic molecules, and through synergistic action with antioxidants in the photosensitive resin system, the oxidation reaction of copper powder during storage and processing is effectively inhibited. The small organic molecules encapsulate the surface of the copper powder, with their N, S, and O heteroatoms forming stable coordination bonds with the copper surface, constructing a dense monomolecular protective layer that effectively blocks oxygen and moisture corrosion, significantly enhancing the oxidation resistance of the copper powder. Simultaneously, the hindered phenolic and phosphite antioxidants introduced into the photosensitive resin can rapidly capture free radicals generated in the slurry, interrupting the oxidation chain reaction and further slowing down the oxidation rate of the copper powder. This synergistic effect not only improves the stability of the photocured copper slurry under room temperature storage conditions but also effectively ensures the integrity of the conductive network in the green body during subsequent heat treatment, thereby significantly improving the overall performance of the final copper parts.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A highly stable photocurable copper paste with synergistic effects of multiple copper powders, characterized in that: The photocurable copper paste, by mass ratio, comprises 73%–94% metal powder, 0.17%–0.8% small organic molecules, 3%–15% reactive diluent, 0.5%–8% oligomer, 0.2%–1.3% photoinitiator, 0.8%–3.5% dispersant, and 0.05%–0.5% antioxidant.

2. The highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 1, characterized in that: The metal powder consists of nano copper powder with a particle size distribution of 5μm to 500μm, spherical micro copper powder with a particle size distribution of 1μm to 5μm, and flake copper powder with a thickness of 0.1μm to 0.5μm and a planar size of 5μm to 40μm.

3. The highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 2, characterized in that: The nano-copper powder accounts for 10% to 20% of the mass of the slurry, the spherical micron copper powder accounts for 30% to 60% of the mass of the slurry, and the flake copper powder accounts for 20% to 40% of the mass of the slurry.

4. The highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 1, characterized in that: The organic small molecule is one of benzotriazole, 2-mercaptobenzimidazole, and citric acid; the reactive diluent is one or a combination of polyethylene glycol diacrylate, isobornyl acrylate, and 1,6-hexanediol diacrylate; the photoinitiator is one or a combination of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-dimethoxy-2-phenylacetophenone, trimethylbenzoyl diphenylphosphine oxide, and 1-hydroxycyclohexylbenzophenone.

5. The highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 1, characterized in that: The oligomer is selected from one or more combinations of epoxy acrylate, polyurethane acrylate, and polyester acrylate; the antioxidant is selected from one or more combinations of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, diphenyl pentaerythritol diphosphite, and bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite.

6. The highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 1, characterized in that: The dispersant is selected from one or more combinations of Solsperse 41000, Solsperse 61000, EFKA-4580, Tego 685, and EFKA-4310.

7. A method for preparing a highly stable photocurable copper paste with synergistic effects of multiple copper powders, characterized in that, Using the highly stable photocurable copper paste with synergistic effects of multiple copper powders as described in claim 1 includes the following steps: S1. Add the metal powder to the V-type mixer according to the proportion to obtain a uniformly mixed copper powder mixture; S2. Dissolve the small organic molecules in an ethanol solution according to the specified ratio to obtain an ethanol solution of the small organic molecules; S3. The organic small molecule ethanol solution is added to the V-type mixer and mixed with the copper powder mixture. After the ethanol has completely evaporated, modified copper powder with a surface passivation layer is obtained. S4. Mix the reactive diluent and photoinitiator according to the ratio until they are miscible. Then add the oligomer and antioxidant in sequence and mix. After mixing, the copper paste premix is ​​obtained. S5. Add the dispersant to the copper paste premix according to the ratio and mix thoroughly to obtain a copper paste mixture. S6. Add the modified copper powder and the copper paste mixture to a homogenizer, start the homogenizer to mix them evenly, and obtain a highly stable photocurable copper paste.

8. The method for preparing a highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 7, characterized in that: In steps S1 and S3, the rotation speed of the V-type mixer is controlled between 100 r / min and 300 r / min, and the mixing time is between 10 min and 60 min.

9. The method for preparing a highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 7, characterized in that: The mass ratio of the copper powder mixture to the ethanol solution is 1:0.1 to 0.

5.

10. The method for preparing a highly stable photocurable copper paste with synergistic effects of multiple copper powders according to claim 7, characterized in that: In step S6, the homogenization program of the homogenizer is set as follows: first, it runs at a speed of 1000 r / min to 1500 r / min for 30 to 60 seconds, then the speed is increased to 2000 r / min to 3500 r / min for 50 to 90 seconds, and finally the speed is increased to 2500 r / min to 3000 r / min for 10 to 40 seconds.

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