Preparation method of metal slurry and copper film

Abstract

The invention discloses a preparation method of metal slurry, which comprises the following steps: selecting copper powder with different morphologies, and pretreating in a reducing atmosphere and a protective atmosphere to obtain different types of prefabricated copper powder; different types of prefabricated copper powder are mixed to form slurry copper powder; the preparation method comprises the following steps: selecting two or more of terpilenol, tributyl citrate, dibutyl phthalate, butyl carbopicryl and dodecanol ester, and mixing with glycerol to form an organic carrier; mixing the slurry copper powder and the organic carrier, and homogenizing in a homogenizer to form a semi-finished product metal slurry; grinding the semi-finished product metal slurry, and finally, decompressing and defoaming to obtain metal slurry; the slurry copper powder accounts for 70-90 wt% of the total weight of the metal slurry, and the organic carrier accounts for 10-30 wt% of the total weight of the metal slurry. The metal slurry is simple in composition, high-molecular polymers such as high-molecular resin are abandoned, the possibility of carbon residues in the sintering process is reduced, and waste gas emission and environmental pollution are effectively reduced. The invention also provides a copper film which is obtained by sintering the metal slurry.

Description

Technical Field

[0001] The present application relates to the field of copper conductive slurry preparation, and specifically to a method for preparing a metal slurry and a copper film. Background Art

[0002] With the widespread popularity of electronic devices, the demand for electronic pastes has shown a significant growth trend. As copper is a low-cost and high-performance conductive material, it occupies a core position in replacing precious metals such as silver.

[0003] The prepared copper-based conductive paste shows broad application potential in the printed electronics industry. The key characteristics of this paste are that it can achieve rapid sintering and densification at low temperatures, while also having excellent conductivity and adhesion strength. However, the current copper paste sintering process has problems such as high complexity, excessive organic additives, incomplete debinding, and the waste gas generated during the debinding process has an adverse impact on the environment, so it is not suitable for large-scale production applications. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a method for preparing a metal slurry, comprising the following steps: Copper powders with different morphologies are selected and pretreated in reducing atmosphere and protective atmosphere to obtain different types of prefabricated copper powders; Mixing different types of the prefabricated copper powders to form slurry copper powder; Select two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarpirol, and dodecanol, and mix them with glycerol to form an organic carrier; After mixing the slurry copper powder and the organic carrier, the mixture is placed in a homogenizer for homogenization to form a semi-finished metal slurry; Grinding the semi-finished metal slurry, and finally decompressing and degassing to obtain the metal slurry; The total weight % of all components constituting the metal slurry is 100wt%, the slurry copper powder accounts for 70-90wt% of the total weight of the metal slurry, and the organic carrier accounts for 10-30wt% of the total weight of the metal slurry.

[0005] In some embodiments of the present application, the reducing atmosphere is hydrogen, and the protective atmosphere is one or both of nitrogen or ammonia.

[0006] In some embodiments of the present application, the copper powders of different morphologies include spherical copper powders and flake copper powders, the particle sizes of the spherical copper powders and the flake copper powders are 0.1-20 μm, and the weight ratio of the spherical copper powders to the flake copper powders is 1:3.

[0007] In some embodiments of the present application, two or more of the terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol occupy 90-99% of the volume of the organic carrier, and the glycerol occupies 1-10% of the volume of the organic carrier.

[0008] In some embodiments of the present application, the pressure of the homogenizer during the homogenization process is 0.1~0.5MPa and the speed is 2000~5000r / min.

[0009] In some embodiments of the present application, the semi-finished metal slurry is ground by a three-roll grinder, the rotation speed of the three-roll grinder is 50~150r / min, the pressure is 1~5MPa, and the semi-finished metal slurry is rolled 2~8 times.

[0010] In some embodiments of the present application, the semi-finished metal slurry is decompressed and degassed in a vacuum degassing machine, and the pressure of the semi-finished metal slurry during decompression and degassing is -80 to -90 KPa.

[0011] In some embodiments of the present application, the copper powder in the slurry accounts for 80 wt % of the total weight of the metal slurry, and the organic vehicle accounts for 20 wt % of the total weight of the metal slurry.

[0012] The present application also provides a copper film, which is prepared by film forming and sintering the metal slurry described above.

[0013] In some embodiments of the present application, the sintering temperature is less than or equal to 300°C.

[0014] In some embodiments of the present application, the metal slurry is sintered using a temperature gradient during the film-forming sintering process.

[0015] Beneficial effects of this application: 1. The use of copper powders with different morphologies and particle sizes can effectively improve the fluidity of the metal slurry, making it easier to evenly distribute the metal slurry during coating, spraying and other processes, thereby improving uniformity and consistency. Secondly, the diversity of particle size distribution helps to optimize the filling performance of the metal slurry, so that the pores between the copper powders can be better filled during the preparation of the metal slurry, enhancing the density and strength of the metal slurry. In addition, mixing copper powders of different particle sizes can also reduce the viscosity of the metal slurry, making it easier to adjust the construction performance of the metal slurry to meet the needs of different processes and equipment.

[0016] 2. In the copper powder pretreatment process, in order to ensure the quality and performance of the copper powder, a reducing atmosphere and a protective atmosphere treatment method are used. This treatment method is intended to effectively prevent the copper powder from oxidizing during the pretreatment stage, thereby ensuring the purity and stability of the copper powder raw materials.

[0017] 3. By selecting a specific weight ratio of spherical copper powder and flake copper powder (1:3) and adjusting the particle size range (0.1~20μm), the densification degree of the copper end sintering can be effectively delayed, thereby ensuring that the gas exhaust channel remains unobstructed for a long enough time during sintering, thereby avoiding the occurrence of bubbling. At the same time, it can also effectively inhibit the edge cracking problem caused by significant shrinkage of the copper end during the sintering stage.

[0018] 4. The metal paste in this application successfully achieves the preparation of conductive copper paste with different rheological properties by optimizing the volume ratio of glycerol in the organic carrier (1-10%). This enables the metal paste to flexibly adapt to different printing conditions, such as different printing pressures, speeds and material properties. In addition, the metal paste also exhibits excellent rheological properties while maintaining excellent conductive properties, thereby ensuring stability and consistency during the printing process.

[0019] 5. In the metal paste of this application, the content of the organic carrier is relatively low (10~30wt%), and the boiling point of the organic carrier is in the range below 350℃, which can ensure that it can be efficiently and completely discharged from the gas discharge channel during the low-temperature treatment stage. This feature allows the metal paste copper paste to complete the sintering process below 300℃ without the need for additional debinding steps, thereby simplifying the process and improving production efficiency.

[0020] 6. During the sintering process of the metal paste to form the copper film, the organic carrier adopts a layered volatilization method, that is, temperature gradient sintering is performed in different temperature sections (for example, from 100℃-200℃-300℃), so as to achieve layered volatilization of the organic carrier. This method significantly reduces the risk caused by concentrated volatilization of the organic carrier in the same temperature stage. Through layered volatilization, the volatilization rate of each solvent in the organic carrier can be effectively controlled, thereby avoiding the formation of defects such as bubbles inside the copper film.

[0021] 7. The metal slurry composition in this application is simplified, consisting only of copper powder and several organic solvents, and abandons polymers such as polymer resins. It not only simplifies the preparation process of the metal slurry, but also significantly reduces the possibility of carbon residues during the sintering process, thereby reducing production costs. At the same time, due to the omission of additives such as polymers, waste gas emissions and environmental pollution are also effectively reduced, reflecting the concept of environmentally friendly production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings required for use in the description of the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 It is a schematic flow chart of the method for preparing the metal slurry of the present invention; Figure 2 A to Figure 2 E is a graph showing the experimental results of the copper film embodiments 1 to 5 after sintering; Figure 3 A to Figure 3 E is a graph showing the experimental results of the copper film after sintering of Embodiments 6 to 10; Figure 4 A to Figure 4 E is a diagram showing the experimental results of the copper films of Example 11 to Example 15 after sintering. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other alternative implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] Example 1 of metal slurry preparation method S100: selecting spherical copper powder and flake copper powder and pretreating them under a reducing atmosphere and a protective atmosphere to obtain prefabricated spherical copper powder and prefabricated flake copper powder; wherein the reducing atmosphere is hydrogen, the protective atmosphere is one or both of nitrogen or ammonia, the particle size of the spherical copper powder and the flake copper powder is 0.1-20 μm, and the weight ratio of the spherical copper powder to the flake copper powder is 1:3; S200: mixing the prefabricated spherical copper powder and the prefabricated flake copper powder to form a slurry copper powder; S300: selecting two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopol, and dodecanol, and putting them into a container with glycerol and stirring (stirring speed is 500-2000r / min) to form an organic carrier; wherein two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopol, and dodecanol occupy 99% of the volume of the organic carrier, and glycerol occupies 1% of the volume of the organic carrier; S400: After mixing the slurry copper powder and the organic carrier, put them into a homogenizer for homogenization to form a semi-finished metal slurry; during the homogenization process, the pressure of the homogenizer is 0.1~0.5MPa and the speed is 2000~5000r / min.

[0025] S500: grinding the semi-finished metal slurry, and finally degassing under reduced pressure to obtain the metal slurry, wherein the semi-finished metal slurry is ground by a three-roll grinder, the speed of the three-roll grinder is 50-150r / min, the pressure is 1-5MPa, and the semi-finished metal slurry is rolled 2-8 times; the semi-finished metal slurry is degassing under reduced pressure in a vacuum degassing machine, and the pressure of the semi-finished metal slurry during degassing is -80--90Kpa; The total weight % of all components constituting the metal slurry is 100wt%, the slurry copper powder accounts for 90wt% of the total weight of the metal slurry, and the organic carrier accounts for 10wt% of the total weight of the metal slurry.

[0026] Example 2 of the method for preparing metal slurry This embodiment is basically the same as the first embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 97% of the volume of the organic carrier, and propylene glycol occupies 3% of the volume of the organic carrier.

[0027] Example 3 of the method for preparing metal slurry This embodiment is basically the same as the first embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 95% of the volume of the organic carrier, and propylene glycol occupies 5% of the volume of the organic carrier.

[0028] Example 4 of the method for preparing metal slurry This embodiment is basically the same as the first embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 93% of the volume of the organic carrier, and propylene glycol occupies 7% of the volume of the organic carrier.

[0029] Example 5 of the method for preparing metal slurry This embodiment is basically the same as the first embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 90% of the volume of the organic carrier, and propylene glycol occupies 10% of the volume of the organic carrier.

[0030] Example 6 of the method for preparing metal slurry This embodiment is basically the same as the first embodiment of the method for preparing metal slurry, except that the copper powder in the slurry accounts for 80wt% of the total weight of the metal slurry, and the organic carrier accounts for 20wt% of the total weight of the metal slurry.

[0031] Example 7 of the method for preparing metal slurry This embodiment is basically the same as the seventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 97% of the volume of the organic carrier, and propylene glycol occupies 3% of the volume of the organic carrier.

[0032] Example 8 of the method for preparing metal slurry This embodiment is basically the same as the seventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 95% of the volume of the organic carrier, and propylene glycol occupies 5% of the volume of the organic carrier.

[0033] Example 9 of the method for preparing metal slurry This embodiment is basically the same as the seventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecyl ester occupy 93% of the volume of the organic carrier, and propylene glycol occupies 7% of the volume of the organic carrier.

[0034] Example 10 of the method for preparing metal slurry This embodiment is basically the same as the seventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 90% of the volume of the organic carrier, and propylene glycol occupies 10% of the volume of the organic carrier.

[0035] Example 11 of the method for preparing metal slurry This embodiment is basically the same as the first embodiment of the method for preparing metal slurry, except that the copper powder in the slurry accounts for 70wt% of the total weight of the metal slurry, and the organic carrier accounts for 30wt% of the total weight of the metal slurry.

[0036] Example 12 of the method for preparing metal slurry This embodiment is basically the same as the eleventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 97% of the volume of the organic carrier, and propylene glycol occupies 3% of the volume of the organic carrier.

[0037] Example 13 of the metal slurry preparation method This embodiment is basically the same as the eleventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 95% of the volume of the organic carrier, and propylene glycol occupies 5% of the volume of the organic carrier.

[0038] Example 14 of the method for preparing metal slurry This embodiment is basically the same as the eleventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 93% of the volume of the organic carrier, and propylene glycol occupies 7% of the volume of the organic carrier.

[0039] Example 15 of the method for preparing metal slurry This embodiment is basically the same as the eleventh embodiment of the metal slurry preparation method, except that two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol, and dodecanol ester occupy 90% of the volume of the organic carrier, and propylene glycol occupies 10% of the volume of the organic carrier.

[0040] Copper Film Embodiments 1 to 15 Copper film embodiments 1 to 15 are obtained by sintering the metal paste prepared by the above-mentioned metal paste preparation method embodiments 1 to 15, respectively, and the sintering temperature is less than 300°C; and temperature gradient sintering is adopted, and there is a temperature gradient change during the sintering process, for example, the sintering temperature is from 100°C-200°C-300°C, and there are two levels of temperature gradient changes. Figure 2 A to Figure 2 As shown in E, Figure 2 A to Figure 2 E are respectively the experimental results of the copper film embodiments 1 to 5 after sintering; Figure 3 A to Figure 3 E are respectively the experimental results of the copper film embodiments 6 to 10 after sintering; Figure 4 A to Figure 4 E are respectively the experimental result diagrams of the copper film embodiments 11 to 15 after sintering; the present application also carries out printability evaluation, conductivity evaluation and adhesion evaluation on the copper film embodiments 1 to 15 respectively.

[0041] The printability evaluation refers to: in the stereomicroscope photograph of the substrate with the transferred copper film, the sample with a flat, smooth and uniform copper film surface without unevenness or wrinkles, the shape consistent with the template, and clear boundaries is evaluated as √; the sample with a certain degree of uneven deformation or other defects on the surface of the copper film but clear boundaries is evaluated as ○; the sample with significant deformation or defects on the surface of the copper film and blurred edges of the pattern is evaluated as ×.

[0042] Conductivity evaluation refers to: using a standardized resistance tester to measure the resistance value of the copper film. Sheet resistance, as a key electrical performance indicator for evaluating the quality of metal slurry, refers to the resistance value of the material per unit length and unit width under given film thickness conditions. According to the standard test method, the film width of the sample copper film pattern is set to 1 mm. Under this condition, a sheet resistance unit (symbolized as □) is defined as an area of ​​1 mm x 1 mm, and the specific length of the test is specified as 100 sheet resistance units.

[0043] Adhesion evaluation refers to an important parameter to examine whether the metal paste and the substrate material are firmly sealed or not, and it is also a major parameter to determine whether the metal paste is usable. If the adhesion is too small, the metal paste after sintering and curing will easily fall off the substrate, causing the electronic device to fail. This application uses metal leads to weld on the copper film, and then uses a tension and compression dynamometer to test the adhesion of the copper thick film to the substrate.

[0044] Please refer to Table 1 for the evaluation results of copper film embodiments 1 to 5.

[0045] Table 1:

[0046] It can be seen from Table 1 that at the same sintering temperature, the surfaces of the copper films prepared using the metal slurries of Examples 1 to 5 all had deformation or defects, and the edge boundaries of the patterns were blurred; the square resistance of the copper films was less than 3, and the adhesion was greater than or equal to 17 N / mm2.

[0047] Please refer to Table 2 for the evaluation results of copper film embodiments 6 to 10.

[0048] Table 2:

[0049] It can be seen from Table 2 that at the same sintering temperature, the copper films prepared using the metal slurries of Examples 6 to 10 are all flat, smooth and uniform, without unevenness or wrinkles, and with clear boundaries; the square resistance of the copper films is less than 3.5, and the adhesion is greater than or equal to 20N / mm2.

[0050] Table 3:

[0051] It can be seen from Table 3 that at the same sintering temperature, the copper films prepared using the metal slurries of Examples 11 to 15 all produced a certain degree of concave-convex deformation or other defects, but the boundaries were clear; the square resistance of the copper films was less than 4.0, and the adhesion was greater than or equal to 23N / mm2.

[0052] Finally, it should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0053] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0054] The above are only implementation methods of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a metal slurry, characterized in that: include: Copper powders with different morphologies are selected and pretreated in reducing atmosphere and protective atmosphere to obtain different types of prefabricated copper powders; Mixing different types of the prefabricated copper powders to form slurry copper powder; Select two or more of terpineol, tributyl citrate, dibutyl phthalate, butylcarpirol, and dodecanol, and mix them with glycerol to form an organic carrier; After mixing the slurry copper powder and the organic carrier, the mixture is placed in a homogenizer for homogenization to form a semi-finished metal slurry; Grinding the semi-finished metal slurry, and finally decompressing and degassing to obtain the metal slurry; The total weight % of all components constituting the metal slurry is 100wt%, the slurry copper powder accounts for 70-90wt% of the total weight of the metal slurry, and the organic carrier accounts for 10-30wt% of the total weight of the metal slurry.

2. The method for preparing the metal slurry according to claim 1, characterized in that: The copper powders with different morphologies include spherical copper powder and flaky copper powder. The particle sizes of the spherical copper powder and the flaky copper powder are 0.1-20 μm, and the weight ratio of the spherical copper powder to the flaky copper powder is 1:

3.

3. The method for preparing the metal slurry according to claim 1, characterized in that: Two or more of the terpineol, tributyl citrate, dibutyl phthalate, butylcarbopyrrol and dodecyl ester occupy 90-99% of the volume of the organic carrier, and the glycerol occupies 1-10% of the volume of the organic carrier.

4. The method for preparing the metal slurry according to claim 1, characterized in that: The homogenizer has a pressure of 0.1-0.5 MPa and a speed of 2000-5000 r / min during the homogenization process.

5. The method for preparing the metal slurry according to claim 1, characterized in that: The semi-finished metal slurry is ground by a three-roll grinder, the rotation speed of the three-roll grinder is 50-150 r / min, the pressure is 1-5 MPa, and the semi-finished metal slurry is rolled 2-8 times.

6. The method for preparing the metal slurry according to claim 1, characterized in that: The semi-finished metal slurry is decompressed and degassed in a vacuum degassing machine, and the pressure of the semi-finished metal slurry during decompression and degassing is -80 to -90 KPa.

7. The method for preparing the metal slurry according to claim 1, characterized in that: The copper powder in the slurry accounts for 80wt% of the total weight of the metal slurry, and the organic vehicle accounts for 20wt% of the total weight of the metal slurry.

8. A copper film, characterized in that: The copper film is prepared by sintering the metal slurry according to any one of claims 1 to 7.

9. The copper film according to claim 8, characterized in that: The sintering temperature is less than or equal to 300°C.

10. The copper film according to claim 9, characterized in that: The metal slurry is sintered by temperature gradient during the film forming sintering process.

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