Metal paste, method for preparing the same, metal pattern printing and laser sintering method

Abstract

The application discloses a metal paste, a preparation method thereof, and a metal pattern printing and laser sintering method. The metal paste is mainly formed by uniformly mixing metal powder, tar, N-methyl pyrrolidone and polyvinyl pyrrolidone, and the tar is coal tar or ethylene tar. By adding tar into the metal paste, the absorption rate of the metal paste to laser energy is enhanced, so that the required laser power of the metal paste in the laser sintering process can be reduced by 1 to 2 orders of magnitude compared with traditional laser additive technology, and refractory metals such as molybdenum and tungsten and high reflectivity metals such as copper can also be sintered or melted; the tar also acts as an antioxidant, so that the laser sintering process does not need a protective atmosphere, and the processing cost is reduced. The metal paste can be used for manufacturing a metal pattern and structure with high conductivity through 3D printing and laser sintering, and can be applied to part repair and sensor manufacturing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal additive manufacturing, in particular to a metal paste, a preparation method thereof, and a metal pattern printing and laser sintering method. BACKGROUND

[0002] Metal 3D printing as a new advanced forming technology has great market potential and application prospect in many fields such as aviation, medical treatment, and electronics. Selective laser sintering (SLS) technology as one of the mainstream metal 3D printing technologies is to use micro metal powder as raw material, and to use high-energy laser to scan the metal powder bed layer by layer, so as to sinter or melt the metal powder and form a metal part.

[0003] The SLS technology has the following problems: 1. It needs to be carried out in an inert gas protection environment. 2. It relies on high-energy laser (laser power of several hundred to thousands of watts) heating to sinter the powder, and the laser energy utilization rate is low, which is difficult to sinter refractory metals (melting point higher than 2000℃) such as molybdenum and tungsten, and high reflectivity metals such as copper; 3. The powder uniformity and sphericity are required to be high, and the powder feeding and laying device is complex, and the equipment is large in size and expensive in cost. SUMMARY

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present application is to provide a metal paste which can be sintered by laser and does not require a protective atmosphere during the sintering process; has a high absorption rate of laser energy, and can sinter or melt refractory metals such as molybdenum and tungsten, and high reflectivity metals such as copper; has a low requirement for the uniformity and sphericity of the metal powder, and can simplify the complexity of the metal 3D printing equipment and reduce the cost of the metal 3D printing equipment.

[0005] The second aspect of the present application is to provide a preparation method of the metal paste.

[0006] The third aspect of the present application is to provide a metal pattern printing and laser sintering method.

[0007] The metal paste according to the first aspect of the present application is mainly composed of metal powder, tar, N-methyl pyrrolidone, and polyvinyl pyrrolidone uniformly mixed, wherein the tar is coal tar and / or ethylene tar.

[0008] The metal paste according to the embodiment of the first aspect of the present application has the following advantages: first, by adding tar into the metal paste, the absorption rate of the metal paste to laser is enhanced, and the energy utilization rate of the metal paste under laser irradiation is improved, so that the laser power can be reduced by 1 to 2 orders of magnitude compared with the traditional laser additive technology when the metal paste of the present application is subjected to laser sintering, and refractory metals such as molybdenum and tungsten and high reflectivity metals such as copper can also be sintered or melted; second, by adding tar into the metal paste, the tar acts as an antioxidant and forms a protective atmosphere under laser irradiation, so that oxidation of the metal powder during laser sintering can be prevented, and thus the metal pattern after laser sintering can have good electrical conductivity, meeting the application requirements; third, the metal paste system of the present application is stable and suitable for 3D printing, and the initial pattern printed has good shape retention, which can be better applied to sensor manufacturing and part defect repair scenes; fourth, the metal paste of the present application has low requirements for the uniformity and sphericity of the metal powder, which can simplify the complexity of the metal 3D printing equipment and reduce the cost of the printing equipment.

[0009] According to some embodiments of the present application, the metal powder is one or more of aluminum powder, copper powder, nickel powder, molybdenum powder, and tungsten powder.

[0010] According to some embodiments of the present application, the particle size of the metal powder is 1-5 μm.

[0011] According to some embodiments of the present application, the metal paste further comprises ethylene glycol butyl ether.

[0012] The preparation method of the metal paste according to the embodiment of the second aspect of the present application is used for preparing the metal paste according to the embodiment of the first aspect of the present application, and comprises the following steps:

[0013] S1: completely dissolving the polyvinylpyrrolidone powder in the N-methylpyrrolidone to obtain a PVP-NMP solution;

[0014] S2: uniformly mixing the PVP-NMP solution and the tar to obtain a first mixed solution;

[0015] S3: uniformly mixing the metal powder and the first mixed solution to obtain a second mixed solution;

[0016] S4: ball milling the second mixed solution;

[0017] S5: vacuum degassing the slurry obtained by ball milling to obtain the metal paste.

[0018] According to the preparation method of the metal paste according to the second aspect of the present application, in addition to the advantages of the first aspect of the present application, the following advantages are also achieved: a metal paste with high viscosity and uniform dispersion can be prepared, the mass fraction of the metal is more than 80%, the viscosity can reach 10 Pa·s, the metal paste has good shear thinning characteristics, is beneficial to 3D printing, has strong printing shape retention, and the prepared metal paste can be used to print patterns on a curved substrate, and is suitable for part defect repair and sensor manufacturing. 4 Pa·s, while having good shear thining characteristics, being beneficial to 3D printing, having strong printing shape retention, and the prepared metal paste can be used to print patterns on a curved substrate, and is suitable for part defect repair and sensor manufacturing.

[0019] According to some embodiments of the present application, in the step S1, the mass ratio of the polyvinylpyrrolidone powder to the N-methylpyrrolidone is 1:1-1.5; in the step S2, the mass ratio of the PVP-NMP solution to the tar is 1:2-3; and in the step S3, the mass ratio of the first mixed solution to the metal powder is 1:5-8.

[0020] According to some embodiments of the present application, the step S2 further comprises adding ethylene glycol butyl ether, wherein the mass ratio of the ethylene glycol butyl ether to the PVP-NMP solution is less than 0.2.

[0021] According to the metal pattern printing and laser sintering method according to the third aspect of the present application, the following steps are included:

[0022] S6: 3D printing is performed using a metal paste to obtain an initial pattern, wherein the metal paste is the metal paste according to the first aspect of the present application or the metal paste prepared by the preparation method of the metal paste according to the second aspect of the present application;

[0023] S7: The initial pattern is scanned using a laser to obtain a sintered metal pattern.

[0024] According to the metal pattern printing and laser sintering method according to the third aspect of the present application, in addition to the advantages of the first aspect of the present application, the following advantages are also achieved: the laser sintering printing pattern has the advantages of low energy consumption, short time consumption, high flexibility, and no need for a protective atmosphere compared to the high-temperature furnace sintering method, the required laser energy is 1 to 2 orders of magnitude lower than that of the SLS technology, and no protective atmosphere is required, so that non-oxidizing sintering can be achieved in an atmospheric environment, the sintering process is simple and convenient, and the device for manufacturing the metal pattern can be simplified.

[0025] According to some embodiments of the present application, in the step S7, the speed of scanning the initial pattern using the laser is 50-200 mm / min, and the spot diameter of the laser on the initial pattern is not less than the line width of the initial pattern.

[0026] According to some embodiments of the present application, in the step S7, the power of the laser is 2-10 W.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0029] Figure 1 This is a flowchart illustrating a method for preparing metal paste according to a second aspect of the present invention.

[0030] Figure 2 This is a flowchart illustrating a metal pattern printing and laser sintering method according to a third aspect of the present invention.

[0031] Figure 3 This is a schematic diagram of the apparatus for creating metal patterns according to a fourth aspect embodiment of the present invention.

[0032] Figure 4 This is a scanning electron microscope image of the copper metal paste printed in Example 1.

[0033] Figure 5 This is a scanning electron microscope image of the copper metal slurry after laser sintering in Example 1.

[0034] Figure 6 A photograph of a metallic pattern created on a sphere.

[0035] Figure 7 This is a scanning electron microscope image of the printed molybdenum metal paste from Example 2.

[0036] Figure 8 This is a scanning electron microscope image of the molybdenum metal slurry after laser sintering in Example 2.

[0037] Figure label:

[0038] Device for creating metal patterns 100; planar motion output mechanism 1; planar motion platform 2; rotary output mechanism 3;

[0039] 4. Workpiece stage; 5. Base plate; 6. Support frame; 7. Vertical motion output mechanism; 8. Connecting plate;

[0040] 11. Laser focusing lens; 12. Laser fiber; 21. Slurry storage tube; 22. Air inlet tube; 23. Printing needle. Detailed Implementation

[0041] Embodiments of the present application are described below in detail with reference to the accompanying drawings, wherein the same or similar components are denoted by the same or similar reference numerals throughout. The embodiments described below by reference to the accompanying drawings are exemplary only, and are for the purpose of explanation of the present application, and are not to be understood as limiting the present application.

[0042] The metal paste and the preparation method thereof, the metal pattern printing and the laser sintering method of the present application are described below in combination with Figures 1 to 8

[0043] The metal paste according to the first embodiment of the present application is mainly composed of coal tar and / or ethylene tar, metal powder, N-methyl pyrrolidone and polyvinyl pyrrolidone, which are uniformly mixed.

[0044] Specifically, the polyvinyl pyrrolidone (PVP) powder is used as a dispersant to achieve good dispersion of the metal powder, and the N-methyl pyrrolidone (NMP) is used as a solvent, and the polyvinyl pyrrolidone powder is easily soluble in the N-methyl pyrrolidone, so that a good and stable colloidal solution can be formed.

[0045] The addition of the coal tar can enhance the absorption rate of the metal paste to the laser and improve the energy utilization rate of the metal paste when it is irradiated by the laser, and the coal tar can also act as an antioxidant to form a protective atmosphere under laser irradiation.

[0046] The metal paste according to the first embodiment of the present application has the following advantages. First, the addition of the coal tar to the metal paste can enhance the absorption rate of the metal paste to the laser and improve the energy utilization rate of the metal paste when it is irradiated by the laser, so that the laser power can be reduced by 1 to 2 orders of magnitude compared with the traditional laser additive technology when the metal paste of the present application is subjected to laser sintering, and it can also be used to sinter or melt refractory metals such as molybdenum and tungsten, and high reflectivity metals such as copper, etc. Second, the coal tar added to the metal paste can act as an antioxidant to form a protective atmosphere under laser irradiation, so that the oxidation of the metal powder during the laser sintering process can be prevented, and the metal pattern after laser sintering can have good electrical conductivity to meet the application requirements. Third, the metal paste system of the present application is stable and suitable for 3D printing, and the initial pattern printed has good shape retention, which can be better applied to the scenes of sensor manufacturing and part defect repair, etc. Fourth, the metal paste of the present application has low requirements for the uniformity and sphericity of the metal powder, which can simplify the complexity of the metal 3D printing equipment and reduce the cost of the printing equipment.

[0047] ​According to some embodiments of the present application, the metal powder is one or more of aluminum powder, copper powder, nickel powder, molybdenum powder, tungsten powder. That is, the metal paste of the present application can contain refractory metals (melting point higher than 2000℃) such as molybdenum, tungsten, and high reflectivity metals such as copper, and the metal paste containing molybdenum, tungsten, and copper of the present application can be sintered or melted by laser irradiation to prepare a metal pattern, so that the application range of the metal paste of the present application is wider, and it can be applied to more actual application scenarios. It can be understood that one type of metal powder can be added to one metal paste according to actual needs, or multiple types of metal powder can be added at the same time.

[0048] According to some embodiments of the present application, the particle size of the metal powder is 1-5 μm. It should be noted that through experiments, it has been verified that the metal powder in this particle size range has good stacking property, is easy to disperse, the metal pattern obtained by sintering has high density and good conductivity. It should be noted that, compared with the SLS technology, the metal paste of the present application has low requirements for the uniformity of the powder, and in one paste, only one type of metal powder with the same particle size can be added, or multiple types of metal powder with different particle sizes can be added, for example, 1 μm metal powder and 5 μm metal powder can be added at the same time in one paste to obtain a metal paste with better stacking density and better shape retention capability; compared with the SLS technology, the present application also has low requirements for the sphericity of the metal powder, and the metal paste made of irregular metal powder such as elliptical and strip-shaped metal powder can be used without affecting the printing effect.

[0049] According to some embodiments of the present application, the metal paste further comprises ethylene glycol butyl ether. It should be noted that ethylene glycol butyl ether is used as a surfactant, and the addition of ethylene glycol butyl ether can reduce the agglomeration of the metal powder, facilitate the dispersion of the metal powder, facilitate 3D printing, and facilitate the formation of a metal pattern with uniform properties, size, and appearance.

[0050] The second aspect of the present application is to provide a preparation method of a metal paste.

[0051] As shown in Figure 1 The preparation method of the metal paste according to the second aspect of the present application is used to prepare the metal paste according to the first aspect of the present application, and comprises the following steps:

[0052] S1: completely dissolving polyvinylpyrrolidone powder in N-methylpyrrolidone to obtain a PVP-NMP solution, wherein the mass ratio of the polyvinylpyrrolidone powder to the N-methylpyrrolidone is 1:1-1.5. Optionally, the mass ratio of the polyvinylpyrrolidone powder to the N-methylpyrrolidone can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc., which can be selected according to the type, size of the metal powder, and the rheological requirements of the slurry, etc.

[0053] Further, step S1 specifically comprises adding the polyvinylpyrrolidone powder into the N-methylpyrrolidone, then stirring and heating to 50-70°C until the polyvinylpyrrolidone powder is completely dissolved in the N-methylpyrrolidone to obtain the PVP-NMP solution (colloidal solution). The average molecular weight of the polyvinylpyrrolidone powder is 8000-30000.

[0054] S2: uniformly mixing the PVP-NMP solution with the tar to obtain a first mixed solution, wherein the mass ratio of the PVP-NMP solution to the tar is 1:2-3. For example, the mass ratio of the PVP-NMP solution to the tar can be 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc.

[0055] S3: uniformly mixing the metal powder with the first mixed solution to obtain a second mixed solution, and the mass ratio of the first mixed solution to the metal powder is 1:5-8. The mass ratio of the first mixed solution to the metal powder within the range can ensure a relatively high viscosity and light absorption rate of the metal slurry, and on the other hand, can ensure sufficient reaction of the organic components and good sintering of the metal under laser irradiation. Specifically, the mass ratio of the first mixed solution to the metal powder can be 1:5, 1:6, 1:7, 1:8, which can be selected according to actual conditions.

[0056] Further, step S3 specifically comprises stirring the first mixed solution, adding the metal powder in small amounts for multiple times while stirring, and continuing to stir for 15-25 min after the addition of the metal powder is completed, which is conducive to uniform dispersion. The stirring can be performed by using an electric mixer to stir the first mixed solution.

[0057] S4: ball milling the second mixed solution; it should be noted that the ball milling of the second mixed solution is used to further increase the mixing uniformity of the metal slurry, which is conducive to the 3D printing process, and the uniformity of the initial pattern obtained by printing is better.

[0058] Further, the step S4 specifically includes pouring the second mixed solution into a ball milling tank, adding ball milling beads with the same mass as the second mixed solution into the ball milling tank, installing the ball milling tank on a planetary ball mill, and rotating the ball milling tank at a speed of 600-1000 r / min for 20-30 minutes.

[0059] S5: performing vacuum defoaming treatment on the slurry obtained through the ball milling to obtain a metal slurry. It should be noted that the vacuum defoaming treatment on the slurry obtained through the ball milling is beneficial to continuous printing and better uniformity of the surface of the metal pattern obtained after sintering.

[0060] Further, the step S5 specifically includes loading the slurry obtained through the ball milling into a slurry storage tube, and performing vacuum defoaming treatment for 15-20 minutes by using a planetary defoaming machine to remove bubbles in the slurry. The defoaming process herein can stir the slurry to achieve sufficient defoaming.

[0061] In addition to the advantages of the first aspect of the present application, the method for preparing the metal slurry according to the second aspect of the present application has the following advantages: high-viscosity and uniformly dispersed metal slurry can be prepared, the mass fraction of the metal is more than 80%, the viscosity can reach 10 4 Pa·s, and the metal slurry has good shear thinning characteristics, is beneficial to 3D printing, has strong shape retention, and can be used to print patterns on a curved substrate, and is suitable for part defect repair and sensor manufacturing.

[0062] According to some embodiments of the present application, the step S2 further includes adding ethylene glycol butyl ether, and the ratio of the mass of the ethylene glycol butyl ether to the mass of the PVP-NMP solution is less than 0.2. It should be noted that the ethylene glycol butyl ether is used as a surfactant, and the addition of the ethylene glycol butyl ether can reduce the agglomeration of the metal powder, which is beneficial to more uniform dispersion of the metal powder, beneficial to 3D printing, and beneficial to forming a metal pattern with uniform properties, size, and appearance. The ethylene glycol butyl ether can be added before the PVP-NMP solution and the tar are uniformly mixed, can be added together with the PVP-NMP solution into the tar, or can be added after the PVP-NMP solution and the tar are uniformly mixed. It has been verified through experiments that when the ratio of the mass of the ethylene glycol butyl ether to the mass of the PVP-NMP solution is within the range, the printing and sintering effects are better.

[0063] The third aspect of the present application is to provide a metal pattern printing and laser sintering method.

[0064] As shown in Figure 2 Fig. 3, the metal pattern printing and laser sintering method according to the third aspect of the present application includes the following steps:

[0065] S6: 3D printing is performed by using the metal paste to obtain an initial pattern, wherein the metal paste is the metal paste prepared by the preparation method of the metal paste according to the first aspect of the present application or the metal paste according to the second aspect of the present application; that is, the metal paste according to the present application is used as a base material to perform the 3D printing process, for example, the metal paste is extruded on a substrate according to a certain path to form an initial pattern.

[0066] S7: The initial pattern is scanned by using a laser to obtain a sintered metal pattern. It can be understood that when the initial pattern is scanned by using a laser, the metal paste in the initial pattern will absorb the laser energy, so that when the laser energy is low, the metal paste will undergo a sintering process, and when the laser energy is high, the metal paste will undergo a melting process, and both sintering and melting of the metal paste should be within the protection scope of the present application.

[0067] According to the metal pattern printing and laser sintering method according to the third aspect of the present application, in addition to the advantages of the first aspect of the present application, the following advantages are also provided: the laser sintering printing pattern has the advantages of low energy consumption, short time consumption, high flexibility, no need for a protective atmosphere, and the like, compared with the high-temperature furnace sintering method; compared with the SLS technology, the required laser energy is 1 to 2 orders of magnitude lower, and there is no need for a protective atmosphere, so that the non-oxidizing sintering can be realized in an atmospheric environment, the sintering process is simple and convenient, and the device for manufacturing the metal pattern can be simplified, in addition, the metal pattern manufactured by the present application has good electrical conductivity and structural strength.

[0068] Further, the metal pattern printing and laser sintering method of the present application further includes the following steps:

[0069] S8: 3D printing is performed by using the metal paste on the formed metal pattern to obtain a second initial pattern;

[0070] S9: The second initial pattern is scanned by using a laser to obtain a second metal pattern;

[0071] S10: Steps S8 to S9 are cyclically performed according to requirements until a metal piece with a target number of layers is obtained. That is, the already formed metal pattern can be used as a base or a substrate to perform the stacking printing and the laser scanning, so as to form a multi-layer metal pattern to meet different application requirements.

[0072] According to some embodiments of the present application, in step S7, the speed of scanning the initial pattern by using a laser is 50 to 200 mm / min, that is, the speed of laser scanning according to the present application is slow, which is beneficial to guarantee the full reaction removal of the organic component and obtain a metal pattern with good electrical conductivity and structural strength.

[0073] According to some embodiments of the present invention, in step S7, the diameter of the laser spot on the initial pattern is not less than the line width of the initial pattern, thereby ensuring the complete sintering of the initial pattern.

[0074] According to some embodiments of the present invention, in step S7, the laser power is 2 to 10 W. That is to say, the laser power of the present invention during laser sintering is much lower than the laser power required by the existing SLS technology, and the utilization rate of laser energy is greatly improved.

[0075] A fourth aspect of the present invention also provides an apparatus 100 for creating metal patterns.

[0076] like Figure 3 As shown, the apparatus 100 for producing metal patterns according to a fourth aspect embodiment of the present invention is used to implement the metal pattern printing and laser sintering method according to a third aspect embodiment of the present invention, comprising:

[0077] A paste printing system is used to extrude metal paste onto a substrate 5;

[0078] The motion system is used to drive the substrate 5 and the paste printing system to move along a preset path;

[0079] The laser output system is used to output laser light to perform laser scanning on the metal paste on the substrate 5.

[0080] According to some embodiments of the present invention, the slurry printing system includes a slurry storage tube 21 and a printing needle 23. The slurry storage tube 21 is used to store metal slurry, and the metal slurry in the slurry storage tube 21 is extruded from the head of the printing needle 23 under the drive of a pneumatic extrusion mechanism or a screw extrusion mechanism.

[0081] More specifically, the pneumatic extrusion mechanism includes an air inlet pipe 22 and a pneumatic dispensing machine. The slurry storage pipe 21 is connected to the pneumatic dispensing machine through the air inlet pipe 22. Under the pneumatic push of the pneumatic dispensing machine, the slurry is extruded from the printing needle 23.

[0082] The motion system comprises a planar motion output mechanism 1, a planar motion platform 2, a rotary output mechanism 3, a workpiece table 4, a base plate 5, a support frame 6, a vertical motion output mechanism 7 and a connecting plate 8, the planar motion output mechanism 1 is used to drive the planar motion platform 2 to move horizontally along the x direction and the y direction, the rotary output mechanism 3 is connected between the workpiece table 4 and the planar motion platform 2 and is used to drive the workpiece table 4 to rotate along the z direction, and the base plate 5 is arranged on the workpiece table 4; the vertical motion output mechanism 7 is arranged on the support frame 6 and is used to drive the connecting plate 8 to move horizontally along the z direction, and the slurry printing system is arranged on the connecting plate 8. It should be noted that the rotary output mechanism 3 is used to increase the degree of freedom of the motion system, and when a spiral pattern or other similar patterns need to be printed, the rotary output mechanism 3 can be arranged to simplify the motion path calculation of the motion system.

[0083] The laser output system comprises a laser focusing mirror 11 or a laser scanning galvanometer, the laser focusing mirror 11 or the laser scanning galvanometer is connected with a laser generator through a laser fiber 12, and the laser focusing mirror 11 or the laser scanning galvanometer is arranged on the connecting plate 8. When the laser output system comprises the laser scanning galvanometer, the laser scanning galvanometer can directly control the movement of the laser spot, and the workpiece table 4 does not need to move. It should be noted that by adjusting the distance between the laser focusing mirror 11 or the laser scanning galvanometer and the base plate 5, the spot diameter of the laser on the initial pattern can be adjusted.

[0084] Under the control of the motion controller, the planar motion output mechanism 1, the rotary output mechanism 3 and the vertical motion output mechanism 7 move coordinately to complete the 3D printing and laser sintering tasks.

[0085] More specifically, the device 100 for manufacturing a metal pattern comprises the following working steps:

[0086] Q1: control the motion system to align the printing needle 23 with the rotation center of the workpiece table 4, and set the initial position for 3D printing;

[0087] Q2: turn on the laser indicating light, control the motion system to align the indicating light spot output by the laser focusing mirror 11 with the rotation center of the workpiece table 4, and set the initial position for laser sintering;

[0088] Q3: turn on the dispensing machine, make the metal slurry be extruded through the printing needle 23, print the set pattern on the base plate 5 under the driving of the motion system, and then turn on the laser when the motion system reaches the initial position of the laser, drive the laser spot to scan the initial pattern obtained by printing, and complete the sintering of the pattern.

[0089] According to some embodiments of the present application, the inner diameter of the printing needle 23 is 150-300 μm, and the propelling air pressure of the dispensing machine can be selected as 0.2-0.7 MPa according to the solid content and the viscosity of the metal slurry.

[0090] According to some embodiments of the present application, the type of laser generator can be a carbon dioxide laser, a semiconductor laser or a fiber laser.

[0091] Two specific examples are given below to more specifically illustrate the present application. Embodiments of the present application can be all embodiments obtained by combining the aforementioned technical solutions, without being limited to the specific examples described below.

[0092] Example 1: Preparation, printing and laser sintering of copper paste

[0093] First, 2 grams of N-methyl pyrrolidone was added into a 25 milliliter beaker, followed by slowly adding 2 grams of polyvinyl pyrrolidone powder (average molecular weight 8000), stirring at 60°C for 10 minutes by a magnetic stirrer to obtain a colorless gel-like solution.

[0094] 1 gram of the above-obtained colorless gel-like solution was taken and added to 3 grams of black viscous coal tar, and stirred and mixed by an electric mixer. Then, 12 grams of copper powder with a powder particle size of 1 μm and 12 grams of copper powder with a powder particle size of 5 μm were weighed and slowly added to the above mixture, and stirring was continued for 20 minutes to obtain a high-viscosity copper paste.

[0095] The above high-viscosity copper paste was transferred to a ball mill jar, and an equal amount of ball milling beads was added, and mixed by a vacuum planetary ball mill at a speed of 1000 revolutions per minute for 30 minutes to obtain a uniformly dispersed copper paste.

[0096] Finally, the uniformly dispersed copper paste was transferred to a paste storage tube, and defoamed by a vacuum defoaming machine for 15 minutes to complete the preparation of the paste.

[0097] The 3D printing and laser sintering of the copper paste were carried out by using the device 100 for making metal patterns as shown in Figure 3 The printing was carried out by using a conical needle with an inner diameter of 150 μm, and the printing effect is shown in Figure 4 The sintering of the printed pattern was carried out by using a semiconductor laser with a wavelength of 976 nm, the laser output power was set to 8 W, the scanning line speed was set to 50 mm / min, and the laser spot diameter was adjusted to 200 μm, and the scanning electron microscope picture of the surface of the sintered pattern is shown in Figure 5 The metal pattern obtained by using the above method has a micro-porous morphology, and due to the anti-oxidation function of the coal tar under laser irradiation, the obtained pattern has not been obviously oxidized, and has good electrical conductivity, with a resistivity of 1.27 μΩ·m. By using the device 100 for making metal patterns as shown in Figure 3 A spiral-shaped metal pattern was made on a spherical surface by using the device 100 for making metal patterns as shown in Figure 6

[0098] Example 2: Preparation, printing and laser sintering of molybdenum paste​

[0099] Take 2 grams of polyvinylpyrrolidone powder (average molecular weight 8000) into 3 grams of N-methylpyrrolidone, stir by magnetic stirrer at 60℃ for 10 minutes to obtain a colorless gel solution.

[0100] Take 1.5 grams of the above obtained colorless gel solution into 3 grams of black viscous coal tar, and then add 0.2 grams of ethylene glycol butyl ether, stir and mix by electric mixer to obtain a mixed solution. Weigh 16 grams of molybdenum powder, slowly add it into the above mixed solution, and continue to stir for 20 minutes to obtain a high viscosity molybdenum slurry.

[0101] Transfer the high viscosity molybdenum slurry into a ball milling tank, add an equal amount of ball milling beads, and mix by using a vacuum planetary ball mill at a speed of 1000 revolutions per minute for 30 minutes to obtain a uniformly dispersed molybdenum slurry.

[0102] Finally, transfer the uniformly dispersed molybdenum slurry into a slurry storage tube, and defoam by using a vacuum defoaming machine for 15 minutes to complete the preparation of the molybdenum metal slurry.

[0103] The 3D printing and laser sintering of the molybdenum slurry are carried out by using the device 100 for making metal patterns shown in Figure 3 The printing effect is shown in Figure 7 The printed pattern is sintered by using a semiconductor laser with a wavelength of 976 nm, the laser output power is set to 6 W, the scanning line speed is set to 50 mm / min, and the laser spot diameter is adjusted to 250 μm. The scanning electron microscope picture of the surface of the sintered pattern is shown in Figure 8 It presents a porous morphology. It is worth mentioning that the melting point of molybdenum metal is as high as 2610℃, and the low-power laser can be used for non-oxidizing sintering in air environment by using the method of the present application, and the sintered pattern has good electrical conductivity with a resistivity of 1.19 μΩ·m.

[0104] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0105] In the description of the application, the terms "first", "second", "third", "fourth" are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an indicated order of importance of the described technical features. Thus, a feature defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "a plurality" is two or more, unless otherwise expressly specified.

[0106] Although embodiments of the present application have been shown and described, it would be appreciated by those skilled in the art that changes, modifications, alternatives and variations to these embodiments could be made without departing from the principles and spirit of the application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method of preparing a metal paste, characterized by, The method comprises the following steps: S1: completely dissolving polyvinylpyrrolidone powder in N-methylpyrrolidone to obtain a PVP-NMP solution; S2: uniformly mixing the PVP-NMP solution with tar to obtain a first mixed solution; S3: uniformly mixing metal powder with the first mixed solution to obtain a second mixed solution; S4: performing ball milling treatment on the second mixed solution; S5: performing vacuum defoaming treatment on the slurry obtained through ball milling to obtain a metal slurry; In the step S1, the mass ratio of the polyvinylpyrrolidone powder to the N-methylpyrrolidone is 1:1-1.5; in the step S2, the mass ratio of the PVP-NMP solution to the tar is 1:2-3; in the step S3, the mass ratio of the first mixed solution to the metal powder is 1:5-8. The metal powder is one or more of aluminum powder, copper powder, nickel powder, molybdenum powder and tungsten powder.

2. The method of claim 1, wherein the metal paste is prepared by the steps of: The step S2 further comprises adding ethylene glycol butyl ether, wherein the mass ratio of the ethylene glycol butyl ether to the PVP-NMP solution is less than 0.

2.

3. A metal paste, which is prepared by the method for preparing a paste according to any one of claims 1 to 2, characterized in that, The metal slurry is mainly formed by uniformly mixing metal powder, tar, N-methylpyrrolidone and polyvinylpyrrolidone, wherein the tar is coal tar or ethylene tar.

4. The metal paste of claim 3, wherein The particle size of the metal powder is 1-5 μm.

5. The metal paste of claim 3, wherein The ethylene glycol butyl ether is further included.

6. A method of metal pattern printing and laser sintering, characterized by, The method comprises the following steps: S6: performing 3D printing by using the metal slurry to obtain an initial pattern, wherein the metal slurry is the metal slurry according to any one of claims 3-5; S7: performing laser scanning on the initial pattern to obtain a sintered metal pattern.

7. The metal pattern printing and laser sintering method according to claim 6, wherein, In the step S7, the speed of the laser scanning on the initial pattern is 50-200 mm / min, and the spot diameter of the laser on the initial pattern is not less than the line width of the initial pattern.

8. The method of metal pattern printing and laser sintering according to claim 6, wherein, In the step S7, the power of the laser is 2-10 W.

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