Stainless steel metal slurry for photocuring and preparation method thereof

Abstract

The invention discloses stainless steel metal slurry for photocuring and a preparation method, and belongs to the technical field of additive manufacturing. The metal slurry contains the following components in percentage by mass: 75%-95% of stainless steel powder, 3%-15% of a reactive diluent, 0.5%-5.5% of an oligomer, 0.3%-1.5% of a photoinitiator, 0.8%-3% of a dispersing agent, 0.05%-0.5% of a polymerization inhibitor and 0.05%-0.5% of a chelating agent; the preparation method comprises the steps of powder screening, premixing of the reactive diluent and the polymerization inhibitor, ultrasonic mixing of components such as the photoinitiator and the like, and homogeneous dispersion. The polymerization inhibitor inhibits free radical polymerization, the chelating agent is complexed with free metal ions to eliminate catalytic activity, and the storage stability is synergistically improved; and the powder dispersity (high Zeta potential) is improved through homogeneous dispersion. The slurry is free of caking after being stored for a long time, stable in curing depth and scraping fineness, and suitable for high-precision photocuring forming.

Description

Technical Field

[0001] This application belongs to the field of additive manufacturing technology, and specifically relates to a photocurable stainless steel metal paste and its preparation method. Background Technology

[0002] Photopolymerization technology, with its significant advantages such as high forming precision, excellent surface finish, and fast forming speed, has been widely used in high-end manufacturing fields such as aerospace, automotive manufacturing, medical devices, and electronic components. Stainless steel, with its excellent corrosion resistance and good mechanical strength, continues to be in high demand for structural and functional components. Combining stainless steel with photopolymerization technology enables rapid and high-precision forming of complex stainless steel parts, effectively overcoming the limitations of traditional casting and forging processes in manufacturing complex structures. This meets the production needs of high-end manufacturing for personalized and customized parts, possessing extremely high industrial value.

[0003] The photocurable stainless steel process consists of four core steps: slurry preparation, photocuring, debinding, and sintering. Among these, the photocurable stainless steel slurry is the technological foundation, directly affecting printability, green strength, and the mechanical properties and density of the final part. As both a "binder" for the stainless steel powder and a "carrier" for photocuring, this slurry must simultaneously meet three major requirements: dispersibility, stability, and curability. Therefore, it has become a key research direction in photocurable stainless steel technology.

[0004] However, the additive manufacturing photocurable silver paste and its preparation method disclosed in invention patent CN116230290A improve the stability and dispersibility of the paste; the photocurable 3D printing metal paste and its preparation method disclosed in patent CN119241745A also improve the stability and cured thickness of the metal paste. However, the photocurable stainless steel metal paste prepared using the above methods still suffers from the problem of trace metal ions precipitating from the stainless steel surface into the paste system under specific temperature and humidity conditions. These metal ions catalyze the resin polymerization reaction, leading to caking and other adverse phenomena in the paste, causing paste failure and preventing printing. Summary of the Invention

[0005] This application provides a photocurable stainless steel metal paste and its preparation method. Under the synergistic effect of polymerization inhibitor and metal ion chelating agent, the monomer is effectively protected and stabilized and free metal ions are bound to form a stable, cyclic complex structure, eliminating the catalytic activity of metal ions, thereby solving the problem of clumping in stainless steel metal paste during long-term storage.

[0006] To achieve the above objectives, this application provides a photocurable stainless steel metal paste, which, by mass ratio, comprises 75% to 95% stainless steel metal powder, 3% to 15% reactive diluent, 0.5% to 5.5% oligomer, 0.3% to 1.5% photoinitiator, 0.8% to 3% dispersant, 0.05% to 0.5% polymerization inhibitor, and 0.05% to 0.5% metal ion chelating agent.

[0007] In one embodiment, the reactive diluent is selected from one or more of polyethylene glycol diacrylate, isobornyl acrylate, lauryl acrylate, vinyl caprolactam, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and neopentyl glycol diacrylate.

[0008] In one embodiment, the oligomer is selected from one or more of epoxy acrylate resin, polyurethane acrylate resin, polyester acrylate resin, and polyether acrylate resin.

[0009] In one embodiment, the photoinitiator is selected from one or more of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, isopropylthioxanthone, benzophenone, bis(2,6-difluoro-3-pyrrolidinyldipentadienyl) and hydroxycyclohexylphenyl ketone.

[0010] In one embodiment, the photoinitiator is selected from one or more of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, isopropylthioxanthone, benzophenone, bis(2,6-difluoro-3-pyrrolidinyldipentadienyl) and hydroxycyclohexylphenyl ketone.

[0011] In one embodiment, the dispersant is selected from one or more of Hypermer™ KD16, Hypermer™ KD20, Hypermer™ KD24, BYK2001, BYK9076, and BYK220; the polymerization inhibitor is selected from one or more of hydroquinone, p-hydroxyanisole, p-tert-butylcatechol, and ZJ-701; and the metal ion chelating agent is selected from acetylacetone and trifluoroacetylacetone.

[0012] A method for preparing a photocurable stainless steel metal paste includes the following steps: S1. Sieve the stainless steel metal powder in a vibrating screen powder machine to remove large-diameter particles and set it aside. S2. According to the mass percentage, add the reactive diluent and the polymerization inhibitor to a magnetic stirrer and mix evenly to obtain a premixed solution; S3. Transfer the premixed liquid to an ultrasonic cleaner, and add photoinitiator, metal ion chelating agent and dispersant to the premixed liquid in sequence. After complete dissolution, add oligomer and mix to obtain a mixed slurry. S4. Add the sieved stainless steel metal powder to the mixed slurry, stir it evenly by hand, and then place it in a homogenizer for dispersion. After even dispersion, a stainless steel metal slurry is obtained.

[0013] In one embodiment, in step S1, the mesh size of the vibrating sieve is 400 to 500 mesh.

[0014] In one embodiment, in step S2, the temperature of the working environment is 20℃~27℃ and the humidity is 25%~45%; the operating temperature of the magnetic stirrer is 40℃~70℃ and the rotation speed is 100 r / min~550 r / min.

[0015] In one embodiment, in step S4, the dispersion process of the homogenizer is divided into four steps; The program consists of four steps: the first step is a speed of 800 r / min to 1500 r / min for 10 to 30 seconds; the second step is a speed of 1500 r / min to 2500 r / min for 30 to 60 seconds; the third step is a speed of 3000 r / min to 4000 r / min for 30 to 40 seconds; and the fourth step is a speed of 1000 r / min to 2500 r / min for 10 to 30 seconds.

[0016] Compared with the prior art, the beneficial effects of this application are: The prepared photocurable stainless steel slurry exhibits excellent long-term storage stability. The polymerization inhibitor reacts with free radicals generated in the system, effectively preventing monomer polymerization and providing chemical stability. The metal ion chelating agent, acetylacetone, coordinates free metal ions to form a stable cyclic complex structure, eliminating their catalytic activity. Through the synergistic effect of the polymerization inhibitor and the metal ion chelating agent, the stainless steel slurry achieves long-term stable storage, with key performance indicators such as curing depth and scraping fineness remaining stable.

[0017] Meanwhile, by using a homogenizer to perform four-stage dispersion treatment on the metal slurry, the stainless steel powder obtained a high Zeta potential, which makes it less likely for the stainless steel powder to agglomerate in the slurry. Attached Figure Description

[0018] 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.

[0019] Figure 1This is a schematic flowchart of the method for preparing photocurable stainless steel metal paste provided in this application; Figure 2 The state of the photocurable stainless steel metal paste provided in this application after three months of storage. Detailed Implementation

[0020] 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.

[0021] See Figures 1 to 2 As shown, the stainless steel metal paste for photocuring and its preparation method provided in this application include, by mass ratio, 75% to 95% stainless steel metal powder, 3% to 15% reactive diluent, 0.5% to 5.5% oligomer, 0.3% to 1.5% photoinitiator, 0.8% to 3% dispersant, 0.05% to 0.5% polymerization inhibitor, and 0.05% to 0.5% metal ion chelating agent.

[0022] The reactive diluent is selected from one or more of polyethylene glycol diacrylate, isobornyl acrylate, lauryl acrylate, vinyl caprolactam, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and neopentyl glycol diacrylate; the oligomer is selected from one or more of epoxy acrylate resin, polyurethane acrylate resin, polyester acrylate resin, and polyether acrylate resin; the photoinitiator is selected from one or more of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, isopropylthioxanthanone, benzophenone, bis(2,6-difluoro-3-pyrrolidinyl)dicentectan, and hydroxycyclohexylphenyl ketone; the dispersant is selected from one or more of Hypermer™ KD16 and Hypermer™ One or more of KD20, Hypermer™ KD24, BYK2001, BYK9076, and BYK220 are selected; the polymerization inhibitor is selected from one or more of hydroquinone, p-hydroxyanisole, p-tert-butylcatechol, and ZJ-701; the metal ion chelating agent is selected from acetylacetone and trifluoroacetylacetone.

[0023] It should be noted that the surface of stainless steel metal powder is not completely inert. It may react with trace amounts of moisture or acidic components in the resin system, causing trace metal ions to be released from the surface of the metal powder into the resin system. Under certain temperature and humidity conditions, these metal ions will catalyze the polymerization or coordination reaction of acrylate double bonds in the resin system, thereby causing the slurry to clump.

[0024] The polymerization inhibitor can capture free radicals generated in the system and react with them to inhibit the polymerization of acrylate double bonds, thus effectively preventing polymerization of the slurry during storage and providing chemical stability to the system. Meanwhile, the metal ion chelating agent acetylacetone binds to free metal ions through coordination bonds to form stable cyclic complexes, further eliminating the catalytic activity of the metal ions. The synergistic effect of these two agents inhibits the free radical chain reaction initiated by metal ions, ensuring the stability of the stainless steel slurry during long-term storage. This avoids clumping while maintaining stability in curing depth and scraping fineness, ensuring consistent slurry performance.

[0025] A method for preparing a photocurable stainless steel metal paste includes the following steps: S1. The stainless steel metal powder is screened in a vibrating screen powder machine to remove large-diameter particles and then set aside for later use. The screen mesh of the vibrating screen powder machine is 400 mesh to 500 mesh.

[0026] S2. According to the mass percentage, add the reactive diluent and polymerization inhibitor to a magnetic stirrer and mix evenly to obtain a premixed solution. The operating environment temperature is 20℃~27℃, and the humidity is 25%~45%; the operating temperature of the magnetic stirrer is 40℃~70℃, and the rotation speed is 100 r / min~550 r / min.

[0027] S3. Transfer the premixed liquid to an ultrasonic cleaner, and add a photoinitiator, a metal ion chelating agent and a dispersant to the premixed liquid in sequence. After they are completely dissolved, add the oligomer. After mixing, a mixed slurry is obtained.

[0028] S4. Add the sieved stainless steel metal powder to the mixed slurry, stir it evenly by hand, and then place it in a homogenizer for dispersion. After even dispersion, a stainless steel metal slurry is obtained.

[0029] The homogenizer's dispersion program consists of four steps: the first step involves a rotation speed of 800 r / min to 1500 r / min for 10 to 30 seconds; the second step involves a rotation speed of 1500 r / min to 2500 r / min for 30 to 60 seconds; the third step involves a rotation speed of 3000 r / min to 4000 r / min for 30 to 40 seconds; and the fourth step involves a rotation speed of 1000 r / min to 2500 r / min for 10 to 30 seconds.

[0030] 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.

[0031] Example 1

[0032] Stainless steel powder was placed on a vibrating screen and sieved through a 400-mesh screen to remove large particles. The powder was then set aside for later use. In an environment with a temperature of 20°C and a humidity of 25%, 3.2% polyethylene glycol diacrylate, 3.2% lauryl acrylate, and 0.2% N-nitrosophenyl aluminum salt (polymerization inhibitor) were taken by mass percentage and placed in a magnetic stirrer. The mixture was stirred evenly at 70°C and 250 r / min. After mixing, a premixed liquid was obtained. The premixed liquid was transferred to an ultrasonic cleaner and 0.4% photoinitiator (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 0.2% photoinitiator hydroxycyclohexylphenyl ketone, 0.2% metal ion chelating agent acetylacetone, 1.3% dispersant Hypermer™ KD16 and 0.5% dispersant BYK2001 were added in sequence. After they were fully dissolved, 1.8% oligomeric epoxy acrylate resin was added and the mixture was continued to be mixed evenly under ultrasonic conditions to obtain a mixed slurry. 89% of the sieved stainless steel metal powder was added to the above mixed slurry and stirred manually until uniform. Then, it was placed in a homogenizer for homogenization and dispersion.

[0033] The homogenizer dispersion process consisted of four steps: an initial rotation speed of 900 r / min for 20 seconds, followed by increasing the speed to 1500 r / min for 60 seconds, then increasing it to 3800 r / min for 30 seconds, and finally reducing the speed to 2000 r / min for 10 seconds. After this process, a photocured stainless steel slurry was obtained. This stainless steel slurry exhibited good flowability and stability, a zeta potential of +47 mV, and no clumping occurred after three months of storage.

[0034] Example 2

[0035] Stainless steel powder was placed on a vibrating sieve and large particles were removed using a 425-mesh sieve. The remaining powder was set aside. At 27°C and 45% humidity, 7% isobornyl acrylate, 5% dipropylene glycol diacrylate, and 0.1% p-hydroxyanisole (polymer inhibitor) were mixed in a magnetic stirrer at 60°C and 550 rpm until homogeneous, yielding a premix. The premix was then transferred to an ultrasonic cleaner, where 0.3% isopropylthioxanthrone (photoinitiator), 0.3% benzophenone (photoinitiator), 0.5% trifluoroacetylacetone (metal ion chelating agent), and 0.5% Hypermer™ (dispersant) were added sequentially. After KD20 and 0.3% dispersant BYK220 are fully dissolved, 2.3% oligomeric polyurethane acrylic resin is added and mixed evenly under ultrasonic conditions to form a mixed slurry. Then, 83.7% sieved stainless steel metal powder is added to the mixed slurry, and after being stirred evenly by hand, it is placed in a homogenizer for homogenization and dispersion.

[0036] The homogenizer dispersion process consisted of four steps: an initial speed of 1000 r / min for 10 seconds, followed by increasing the speed to 1800 r / min for 40 seconds, then increasing it to 3500 r / min for 40 seconds, and finally reducing the speed to 2500 r / min for 30 seconds. After this process, a light-cured stainless steel slurry was obtained. This stainless steel slurry exhibited good flowability and stability, a zeta potential of +41 mV, and no clumping occurred after three months of storage.

[0037] Example 3

[0038] Stainless steel powder was placed in a vibrating sieve and large particles were removed using a 500-mesh sieve. The remaining powder was set aside. Under conditions of 25°C and 32% humidity, 6% (by weight) of the reactive diluent 1,6-hexanediol diacrylate, 3% (by weight) of the reactive diluent tripropylene glycol diacrylate, 5.2% (by weight) of the reactive diluent neopentyl glycol diacrylate, and 0.5% (by weight) of the polymerization inhibitor p-tert-butylcatechol were added to a magnetic stirrer. The magnetic stirrer was set to 40°C and 400 rpm. After thorough mixing, the resulting mixture was transferred to an ultrasonic cleaner. Then, 0.8% (by weight) of the photoinitiator bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), 0.7% (by weight) of the photoinitiator bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 0.3% (by weight) of the metal ion chelating agent trifluoroacetylacetone, and 2% (by weight) of the dispersant Hypermer™ were added sequentially. After KD24 and 1% dispersant BYK9076 are fully dissolved, 5.5% oligomeric polyether acrylic resin is added and mixed evenly under ultrasonic conditions to form a mixed slurry. Then, 75% sieved stainless steel metal powder is added to the mixed slurry, and after being stirred manually until uniform, it is placed in a homogenizer for dispersion treatment.

[0039] The homogenizer dispersion process consisted of four steps: an initial speed of 1500 r / min for 20 seconds, followed by increasing the speed to 2000 r / min for 50 seconds, then increasing it to 4000 r / min for 30 seconds, and finally reducing the speed to 1000 r / min for 20 seconds. After this process, a photocured stainless steel slurry was obtained. This stainless steel slurry exhibited good flowability and stability, a zeta potential of +49 mV, and no clumping occurred after three months of storage.

[0040] Example 4

[0041] Stainless steel powder was placed in a vibrating sieve and large particles were removed using a 400-mesh sieve. The remaining powder was set aside. Under conditions of 27°C and 45% humidity, 4.5% (by weight) of dipropylene glycol diacrylate, 2.1% (by weight) of polyethylene glycol diacrylate, and 0.1% (by weight) of polymerization inhibitor ZJ-701 were added to a magnetic stirrer and mixed at 50°C and 300 rpm. After thorough mixing, a premix was obtained. This premix was then transferred to an ultrasonic cleaner, where 0.2% (by weight) of photoinitiator bis(2,6-difluoro-3-pyrrolephenyl)titanium carbonate, 0.2% (by weight) of photoinitiator hydroxycyclohexylphenyl ketone, 0.1% (by weight) of metal ion chelating agent acetylacetone, and 0.5% (by weight) of dispersant Hypermer™ were added sequentially. After KD20 and 0.8% dispersant BYK220 are fully dissolved, 1.5% oligomeric polyester acrylic resin is added and mixed evenly to obtain a mixed slurry. Then, 90% sieved stainless steel metal powder is added to the mixed slurry, manually stirred until uniform, and then placed in a homogenizer for dispersion treatment.

[0042] The homogenizer dispersion process consisted of four steps: an initial speed of 800 rpm for 20 seconds, followed by increasing the speed to 2500 rpm for 35 seconds, then increasing the speed to 3000 rpm for 35 seconds, and finally reducing the speed to 1500 rpm for 30 seconds. After this process, a photocured stainless steel slurry was obtained. This stainless steel slurry exhibited good flowability and stability, a zeta potential of +43 mV, and no clumping occurred after three months of storage.

[0043] Example 5

[0044] Stainless steel powder was placed in a vibrating sieve and large particles were removed using a 425-mesh sieve. The remaining powder was set aside. Under conditions of 25°C and 40% humidity, 5.4% (by weight) of the reactive diluent 1,6-hexanediol diacrylate, 4.3% (by weight) of the reactive diluent polyvinyl caprolactam, and 0.3% (by weight) of the polymerization inhibitor p-tert-butylcatechol were added to a magnetic stirrer and mixed at 55°C and 350 rpm. After thorough mixing, a premix was obtained. This premix was then transferred to an ultrasonic cleaner, where 0.2% (by weight) of the photoinitiator benzophenone, 0.1% (by weight) of the photoinitiator hydroxycyclohexylphenyl ketone, 0.3% (by weight) of the metal ion chelating agent acetylacetone, and 2.4% (by weight) of the dispersant Hypermer™ were added sequentially. After KD16 is fully dissolved, add 3% oligomeric polyurethane acrylic resin and continue stirring until uniform. After mixing, a mixed slurry is obtained. Add 84% sieved stainless steel metal powder to the mixed slurry, stir manually until uniform, and then place it in a homogenizer for dispersion.

[0045] The homogenizer dispersion process consisted of four steps: an initial speed of 1200 r / min for 20 seconds, followed by increasing the speed to 2200 r / min for 45 seconds, then increasing the speed to 3500 r / min for 35 seconds, and finally reducing the speed to 1500 r / min for 20 seconds. After this process, a photocured stainless steel slurry was obtained. This stainless steel slurry exhibited good flowability and stability, a zeta potential of +46 mV, and no clumping occurred after three months of storage.

[0046] 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 stainless steel paste for photocuring, characterized by: The stainless steel metal paste comprises, by mass percentage, 75-95% of stainless steel metal powder, 3-15% of active diluent, 0.5-5.5% of oligomer, 0.3-1.5% of photoinitiator, 0.8-3% of dispersant, 0.05-0.5% of polymerization inhibitor and 0.05-0.5% of metal ion chelating agent.

2. The stainless steel paste for photocuring according to claim 1, characterized by: The active diluent is selected from one or more of polyethylene glycol diacrylate, isobornyl acrylate, lauryl acrylate, vinyl caprolactam, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate and neopentyl glycol diacrylate.

3. The stainless steel paste for photocuring according to claim 1, characterized by: The oligomer is selected from one or more of epoxy acrylate resin, polyurethane acrylate resin, polyester acrylate resin and polyether acrylate resin.

4. The photocurable stainless steel paste according to claim 1, wherein: The photoinitiator is selected from one or more of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, isopropyl thioxanthone, benzophenone, bis 2,6-difluoro-3-pyrrolylphenyl titanium complex and hydroxycyclohexyl phenyl ketone.

5. The photocurable stainless steel paste of claim 1, wherein: The photoinitiator is selected from one or more of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, isopropyl thioxanthone, benzophenone, bis 2,6-difluoro-3-pyrrolylphenyl titanium complex and hydroxycyclohexyl phenyl ketone.

6. The stainless steel paste for photocuring according to claim 1, characterized by: The dispersant is selected from one or more of HypermerTM KD16, HypermerTM KD20, HypermerTM KD24, BYK2001, BYK9076 and BYK220; the polymerization inhibitor is selected from one or more of hydroquinone, p-hydroxyanisole, p-tert-butylcatechol and ZJ-701; and the metal ion chelating agent is selected from acetylacetone or trifluoroacetylacetone.

7. A method for preparing a light-cured stainless steel metal paste, characterized by, The use of the stainless steel metal paste for photocuring according to claim 1 comprises the following steps: S1, screening the stainless steel metal powder in a vibrating screen powder machine, removing large particle size particles and reserving; S2, adding the active diluent and the polymerization inhibitor into a magnetic stirrer according to the mass percentage, uniformly mixing to obtain a premix liquid; S3, transferring the premix liquid into an ultrasonic cleaning machine, sequentially adding the photoinitiator, the metal ion chelating agent and the dispersant into the premix liquid, after completely dissolving, adding the oligomer, after mixing, obtaining a mixed slurry; S4, adding the screened stainless steel metal powder into the mixed slurry, manually stirring uniformly, placing in a homogenizer for dispersion, after uniformly dispersing, obtaining a stainless steel metal paste.

8. The method of claim 7, wherein the method further comprises the step of: In step S1, the screen mesh of the vibrating screen powder machine is 400-500 mesh. ​ 9. The method for preparing photocurable stainless steel metal paste according to claim 7, characterized in that: In step S2, the temperature of the working environment is 20-27℃ and the humidity is 25-45%; the working temperature of the magnetic stirrer is 40-70℃ and the rotating speed is 100-550 r / min.

10. The method for preparing photocurable stainless steel metal paste according to claim 7, characterized in that: In step S4, the dispersion program of the homogenizer is divided into four steps; The first step is 800-1500 r / min for 10-30 seconds; the second step is 1500-2500 r / min for 30-60 seconds; the third step is 3000-4000 r / min for 30-40 seconds; and the fourth step is 1000-2500 r / min for 10-30 seconds. The first step is 800-1500 r / min for 10-30 seconds; the second step is 1500-2500 r / min for 30-60 seconds; the third step is 3000-4000 r / min for 30-40 seconds; and the fourth step is 1000-2500 r / min for 10-30 seconds.

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