A preparation process for thick film copper metal ceramic-based thick film circuit board

Abstract

The present invention discloses a preparation process for a thick-film copper metal ceramic-based thick-film circuit board, which relates to the technical field of circuit boards. The process comprises the following steps: Step 1: Under a nitrogen atmosphere, a binder is added to a solvent and stirred evenly to obtain an organic carrier; pretreated copper particles are added and stirred at a temperature of 40-50°C for 20-30 minutes; glass powder is added and ground and mixed to obtain a thick-film copper slurry; Step 2: the copper slurry is evenly printed on a ceramic substrate; the substrate is pre-baked at 150-160°C for 10-30 minutes in a sintering furnace under a nitrogen atmosphere; the substrate is heated to 220-230°C and baked for 10-30 minutes; the substrate is heated to 450-550°C and calcined for a primary calcination for 30-40 minutes; the substrate is secondary calcined at 800-900°C for 20-30 minutes; the substrate is cooled and placed at room temperature for 1-2 hours to form a thick-film copper layer; and a thick-film circuit board with excellent conductivity and adhesion is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of circuit boards, in particular to a preparation process of a thick-film copper metal ceramic-based thick-film circuit board. Background Art

[0002] Thick-film circuit boards are widely used in the electronics industry due to their excellent electrical performance, high reliability, and high thermal conductivity. Thick-film copper-metal ceramic-based circuit boards are a special type of thick-film circuit board; they combine the excellent conductivity of copper metal with the high heat resistance of ceramic substrates to meet the needs of high-performance electronic products.

[0003] Thick film circuit boards are generally made by coating a conductive paste on a ceramic substrate through a printing process and sintering it. In copper-based thick film circuit boards, the preparation and sintering process of thick film copper paste are key technologies that affect the conductivity, adhesion and other properties of thick film circuit boards. In the existing technology, thick film copper paste is prepared from copper particles, organic carriers, and glass powder; common copper particles are generally copper powders of about 5μm, but single, larger-sized copper powder pastes have the disadvantages of high porosity, poor uniformity and density after sintering, resulting in high resistance and poor adhesion of the thick film copper layer. On the other hand, organic carriers generally include solvents and binders. Common binders have a high residual carbon rate after sintering, which affects the conductivity of the thick film copper layer; binders generally do not promote the dispersion of inorganic matter, resulting in unevenness, affecting the quality of the thick film copper layer.

[0004] In summary, it is of great significance to solve the above problems and prepare a thick film circuit board based on thick film copper metal ceramic. Summary of the Invention

[0005] The object of the present invention is to provide a preparation process for a thick film copper metal ceramic-based thick film circuit board to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A process for preparing a thick film copper metal ceramic-based thick film circuit board comprises the following steps:

[0008] Step 1: (1) Washing copper particles in dilute hydrochloric acid, deionized water, and ethanol in sequence to obtain pretreated copper particles; (2) Adding a binder to a solvent and stirring evenly under a nitrogen atmosphere to obtain an organic vehicle; adding the pretreated copper particles, stirring at a temperature of 40 to 50° C. for 20 to 30 minutes; adding glass powder and grinding and mixing to obtain a thick film copper slurry;

[0009] Step 2: Print the copper paste evenly on the ceramic substrate; place it in a sintering furnace, pre-bake at 150-160°C under a nitrogen atmosphere for 10-30 minutes; heat it to 220-230°C and bake it for 10-30 minutes; heat it to 450-550°C and calcine it once for 30-40 minutes; heat it to 800-900°C and calcine it again for 20-30 minutes; cool it and place it at room temperature for 1-2 hours to form a thick film copper layer; and obtain a thick film circuit board.

[0010] More optimally, the raw materials of the thick film copper paste include the following substances: by weight, 74 to 76 parts of copper particles, 4 to 6 parts of glass powder, 3 to 6 parts of binder, and 14 to 17 parts of solvent.

[0011] More optimally, the copper particles include 1±0.5 μm copper powder, 50±20 nm copper powder, and copper-based graphene in a mass ratio of (2.8-2.9):1:(0.1-0.2).

[0012] More optimally, the preparation method of the copper-based graphene is: urea and graphene oxide are added to deionized water in sequence, dispersed evenly, and hydrothermally reacted at 120-150° C. for 6-12 hours; washed, dried, and ground to obtain nitrogen-doped graphene; ultrasonically dispersed in dimethylformamide, copper nitrate, titanium tetrachloride, and boric acid are added and stirred evenly; placed in a microwave reactor, under a nitrogen atmosphere, set the power to 800-1000 W, and heated for 1-3 minutes; filtered, washed, and dried to obtain copper-based graphene.

[0013] More optimally, in the raw material of the nitrogen-doped graphene, the mass ratio of urea to graphene oxide is 2-3:1; in the raw material of the copper-based graphene, the ratio of nitrogen-doped graphene, copper nitrate, titanium tetrachloride, and boric acid is 1:(1.5-1.8):(0.1-0.2):(0.3-0.5).

[0014] More optimally, the preparation method of the adhesive is as follows: (1) under a nitrogen atmosphere, methyl methacrylate, acrylamide, 2-butyl methacrylic acid, and azobisisobutyronitrile are sequentially added to toluene, the temperature is set to 60-80°C, and the reaction is stirred for 2-4 hours; cysteine ​​is added dropwise, and the reaction is continued for 1-2 hours; the product is washed with n-hexane and dried to obtain an acrylic copolymer; (2) the acrylic copolymer is added to dimethylformamide, an epoxy silane coupling agent is added, the reaction is stirred at 80-85°C for 1-2 hours, and the mixture is washed and dried to obtain an adhesive.

[0015] More optimally, in the raw materials of the acrylic copolymer, the molar ratio of methyl methacrylate, acrylamide, 2-butyl methacrylic acid, and cysteine ​​is (35-38):(4-7):58:3; in the raw materials of the adhesive, the mass ratio of the acrylic copolymer to the epoxy silane coupling agent is 1:0.1-0.2.

[0016] More optimally, the solvent comprises dimethylformamide, terpineol, diethylene glycol butyl ether and deionized water in a mass ratio of 50: (40-43): (5-8): 2.

[0017] More optimally, the heating rate of the pre-baking is 5-6°C / min; the heating rate of the intermediate baking is 10-15°C / min; the heating rate of the primary calcination is 65-75°C / min; and the heating rate of the secondary calcination is 50-60°C / min.

[0018] More optimally, the thickness of the thick copper layer is 30-80 μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects: by setting up multi-level copper particles, preparing a binder with a specific chain segment, and formulating an adaptive solvent to form a thick-film copper slurry; and by coordinating a specific heating rate and a multi-level temperature calcination treatment, the adhesion and conductivity of the thick-film copper metal ceramic-based thick-film circuit board are effectively maximized, thereby improving its quality and applicability.

[0020] In this scheme, the copper particles comprise micron-sized copper powder, nano-sized copper powder, and copper-based graphene. This multi-stage formulation effectively improves the uniformity of the slurry and enhances printing performance, resulting in a smooth coating. The nano-sized copper powder effectively fills the voids within the micron-sized copper powder, effectively enhancing post-sintering density and suppressing cracking, thereby improving manufacturing efficiency and the stability of the thick copper layer. Furthermore, the copper-based graphene is introduced as a conductive reinforcement phase, effectively reducing resistance and enhancing conductivity. To improve the dispersion of graphene in the copper powder, enhance its interface with the copper powder, and maximize performance enhancement, the scheme employs nitrogen-doped graphene oxide, followed by pre-charged copper and titanium ions on its surface. Microwave doping is then used to produce reduced metal-doped graphene. The copper pre-doping improves the graphene's fluidity during the copper powder sintering process, enhancing its uniform dispersion and interface within the thick copper layer. Furthermore, the introduction of boric acid facilitates copper and titanium loading, while the presence of boron enhances oxidation resistance during sintering and strengthens the mechanical properties of the thick copper layer. The introduction of low-content titanium can improve the dimensional stability of copper grains during sintering, thereby ensuring high conductivity.

[0021] In this scheme, a binder with specific chain segments is prepared. It is first copolymerized with methyl methacrylate, acrylamide, and 2-butyl methacrylate in specific ratios to form an acrylic copolymer; this is then prepared using an amino-grafted epoxy silane coupling agent. By limiting the molar amounts of methyl methacrylate, acrylamide, and 2-butyl methacrylate, their wettability on copper particles is ensured while sintering properties are maximized and carbon residue is reduced. Excessive amounts of methyl methacrylate should be avoided, as this increases carbon residue and resistance. 2-Butyl methacrylate, due to its butyl group content, is prone to rapid thermal decomposition. The carboxyl groups it contains can complex with metal ions. The grafted cysteine ​​and subsequent grafted silane coupling agent effectively disperse the nanoparticles, inhibit aggregation, and evenly disperse the copper particles. This improves the film-forming properties of the thick-film copper paste, enhances smoothness, and strengthens the adhesion of the thick-film copper layer.

[0022] In the scheme, a solvent is optimized based on the binder, copper particles, and glass powder. The solvent has high wettability for copper particles and glass powder, which is beneficial to dispersion and sintering uniformity. In addition, the solvent can dissolve the binder very well, thereby improving the film quality. Moreover, due to its good solubility, it can effectively reduce thermal degradation residues. Among them, the solvents include dimethylformamide, terpineol, diethylene glycol butyl ether, and deionized water. Deionized water and dimethylformamide are low-boiling point solvents, so the previous pre-baking can be effectively volatilized, and the heating rate in this process should not be too high. Too high a temperature will lead to a faster volatilization rate, resulting in a large amount of exhaust and increased porosity. Then the temperature is increased to the medium baking temperature to volatilize the higher boiling point terpineol and diethylene glycol butyl ether in layers. This can effectively ensure wettability and combine with subsequent multi-step sintering to reduce the residual carbon rate of the binder and ensure the quality of the thick film copper layer.

[0023] In this scheme, the coagulant pyrolysis begins at approximately 160°C, with the pyrolysis plateaus at around 270°C and 350°C. After the intermediate bake, a faster heating rate is used to decompose the binder, improving the fluidity of the glass powder and subsequent wettability of the glass powder on the copper particles. Simultaneously, a faster temperature rise reduces the amount of residual binder, thereby enhancing the adhesion and density of the copper layer and the conductivity of the thick-film circuit board. After the primary calcination, the organic vehicle is essentially completely pyrolyzed, with minimal residue. The temperature is then raised to the secondary calcination temperature. During this stage, the temperature is slightly lowered to reduce porosity, enhance glass powder wettability on the copper particles, and improve adhesion and density. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] It should be noted that the following parts are calculated by weight, and the purchase manufacturers of all raw materials involved in the present invention are exemplified without any special restrictions: in the following embodiments, the glass powder has an initial melting temperature of 430°C, a model of FR01, and a mesh size of 2000 mesh; the model of 1 μm copper powder is XH-Cu-001, and the brand is Xiaohuang Nano; the brand of 50 nm copper powder is YB-1, and the brand is Yinbai; the average thickness of graphene oxide is 1.5 nm, and the brand is Zhitai; copper nitrate is copper nitrate trihydrate, the CAS number of methyl methacrylate is 80-62-6, the CAS number of acrylamide is 79-06-1, the CAS number of 2-butyl-methacrylic acid is 97-86-9, and the CAS number of cysteine ​​is 52-90-4, and other raw materials are commercially purchased; in the following embodiments, the thickness of the thick film copper layer is 50 μm;

[0026] Example 1: A process for preparing a thick film copper cermet-based thick film circuit board, comprising the following steps:

[0027] Pre-preparation: Urea and graphene oxide in a mass ratio of 3:1 were added to deionized water and dispersed uniformly, and hydrothermally reacted at 150°C for 8 hours; washed, dried, and ground to obtain nitrogen-doped graphene; 10 parts of nitrogen-doped graphene were ultrasonically dispersed in 100 parts of dimethylformamide, and 16 parts of copper nitrate, 1.5 parts of titanium tetrachloride, and 4 parts of boric acid were added and stirred uniformly; the mixture was placed in a microwave reactor under a nitrogen atmosphere at a power of 1000 W and heated for 3 minutes; filtered, washed, and dried to obtain copper-based graphene;

[0028] Under nitrogen atmosphere, methyl methacrylate, acrylamide, and 2-butyl-methacrylic acid in a molar ratio of 36:6:58 were added to toluene in sequence, and azobisisobutyronitrile (the amount added was 2 wt% of the mixed monomers) was added; the temperature was set to 75°C and stirred for 3 hours; cysteine ​​(the molar ratio of 2-butyl-methacrylic acid to cysteine ​​was 58:3) was added dropwise and the reaction was continued for 1 hour; the product was washed with n-hexane and dried to obtain an acrylic copolymer; (2) 10 parts of the acrylic copolymer was added to dimethylformamide, 1.5 parts of epoxy silane coupling agent KH560 were added, and the mixture was stirred at 80°C for 2 hours, washed, and dried to obtain a binder;

[0029] Step 1: 75 parts of copper particles (1 μm copper powder, 50 nm copper powder, and copper-based graphene in a ratio of 2.84:1:0.16) were placed in a 5 wt% dilute hydrochloric acid aqueous solution and ultrasonicated for 10 minutes, followed by rinsing with deionized water and ethanol in sequence to obtain pretreated copper particles;

[0030] Under a nitrogen atmosphere, 4 parts of the binder were added to 16 parts of a solvent (50:42:6:2 of dimethylformamide, terpineol, diethylene glycol butyl ether, and deionized water) and stirred to obtain an organic vehicle; pretreated copper particles were added and stirred at 45°C for 30 minutes; 5 parts of glass powder were added and ground to obtain a thick film copper slurry;

[0031] Step 2: Print the copper slurry evenly on the ceramic substrate; place it in a sintering furnace, under a nitrogen atmosphere, set the heating rate to 5℃ / min at room temperature, heat it to 160℃ for pre-bake for 20 minutes; set the heating rate to 15℃ / min, heat it to 225℃ and bake it for 20 minutes; set the heating rate to 70℃ / min, heat it to 520℃ and calcine it for 30 minutes; set the heating rate to 55℃ / min, heat it to 880℃ and calcine it for 30 minutes; cool it and place it at room temperature for 2 hours to form a thick film copper layer; and obtain a thick film circuit board.

[0032] Example 2: A process for preparing a thick film copper cermet-based thick film circuit board, comprising the following steps:

[0033] Pre-preparation: Urea and graphene oxide in a mass ratio of 3:1 were added to deionized water and dispersed uniformly, and hydrothermally reacted at 150°C for 8 hours; washed, dried, and ground to obtain nitrogen-doped graphene; 10 parts of nitrogen-doped graphene were ultrasonically dispersed in 100 parts of dimethylformamide, and 16 parts of copper nitrate, 1.5 parts of titanium tetrachloride, and 4 parts of boric acid were added and stirred uniformly; the mixture was placed in a microwave reactor under a nitrogen atmosphere at a power of 1000 W and heated for 3 minutes; filtered, washed, and dried to obtain copper-based graphene;

[0034] Under nitrogen atmosphere, methyl methacrylate, acrylamide, and 2-butyl-methacrylic acid in a molar ratio of 36:6:58 were added to toluene in sequence, and azobisisobutyronitrile (the amount added was 2 wt% of the mixed monomers) was added; the temperature was set to 75°C and stirred for 3 hours; cysteine ​​(the molar ratio of 2-butyl-methacrylic acid to cysteine ​​was 58:3) was added dropwise and the reaction was continued for 1 hour; the product was washed with n-hexane and dried to obtain an acrylic copolymer; (2) 10 parts of the acrylic copolymer was added to dimethylformamide, 1.5 parts of epoxy silane coupling agent KH560 were added, and the mixture was stirred at 80°C for 2 hours, washed, and dried to obtain a binder;

[0035] Step 1: 74 parts of copper particles (1 μm copper powder, 50 nm copper powder, and copper-based graphene in a ratio of 2.9:1:0.1) were placed in a 5 wt% dilute hydrochloric acid aqueous solution and ultrasonicated for 10 minutes, followed by rinsing with deionized water and ethanol in sequence to obtain pretreated copper particles;

[0036] Under a nitrogen atmosphere, 3 parts of the binder were added to 14 parts of a solvent (50:40:8:2 of dimethylformamide, terpineol, diethylene glycol butyl ether, and deionized water) and stirred to obtain an organic vehicle; pretreated copper particles were added and stirred at 45°C for 30 minutes; 4 parts of glass powder were added and ground to obtain a thick film copper slurry;

[0037] Step 2: Print the copper slurry evenly on the ceramic substrate; place it in a sintering furnace, under a nitrogen atmosphere, set the heating rate to 5℃ / min at room temperature, heat it to 160℃ for pre-bake for 20 minutes; set the heating rate to 15℃ / min, heat it to 225℃ and bake it for 20 minutes; set the heating rate to 70℃ / min, heat it to 450℃ and calcine it for 30 minutes; set the heating rate to 55℃ / min, heat it to 900℃ and calcine it for 30 minutes; cool it and place it at room temperature for 2 hours to form a thick film copper layer; obtain a thick film circuit board.

[0038] Example 3: A process for preparing a thick film copper cermet-based thick film circuit board, comprising the following steps:

[0039] Pre-preparation: Urea and graphene oxide in a mass ratio of 3:1 were added to deionized water and dispersed uniformly, and hydrothermally reacted at 150°C for 8 hours; washed, dried, and ground to obtain nitrogen-doped graphene; 10 parts of nitrogen-doped graphene were ultrasonically dispersed in 100 parts of dimethylformamide, and 16 parts of copper nitrate, 1.5 parts of titanium tetrachloride, and 4 parts of boric acid were added and stirred uniformly; the mixture was placed in a microwave reactor under a nitrogen atmosphere at a power of 1000 W and heated for 3 minutes; filtered, washed, and dried to obtain copper-based graphene;

[0040] Under nitrogen atmosphere, methyl methacrylate, acrylamide, and 2-butyl-methacrylic acid in a molar ratio of 36:6:58 were added to toluene in sequence, and azobisisobutyronitrile (the amount added was 2 wt% of the mixed monomers) was added; the temperature was set to 75°C and stirred for 3 hours; cysteine ​​(the molar ratio of 2-butyl-methacrylic acid to cysteine ​​was 58:3) was added dropwise and the reaction was continued for 1 hour; the product was washed with n-hexane and dried to obtain an acrylic copolymer; (2) 10 parts of the acrylic copolymer was added to dimethylformamide, 1.5 parts of epoxy silane coupling agent KH560 were added, and the mixture was stirred at 80°C for 2 hours, washed, and dried to obtain a binder;

[0041] Step 1: 76 parts of copper particles (1 μm copper powder, 50 nm copper powder, and copper-based graphene in a ratio of 2.8:1:0.2) were placed in a 5 wt% dilute hydrochloric acid aqueous solution and ultrasonicated for 10 minutes, and then rinsed with deionized water and ethanol in sequence to obtain pretreated copper particles;

[0042] Under a nitrogen atmosphere, 6 parts of a binder were added to 17 parts of a solvent (50:43:5:2 of dimethylformamide, terpineol, diethylene glycol butyl ether, and deionized water) and stirred to obtain an organic vehicle; pretreated copper particles were added and stirred at 45°C for 30 minutes; 6 parts of glass powder were added and ground to obtain a thick film copper slurry;

[0043] Step 2: Print the copper slurry evenly on the ceramic substrate; place it in a sintering furnace, under a nitrogen atmosphere, set the heating rate to 5℃ / min at room temperature, heat it to 160℃ and pre-bake for 20 minutes; set the heating rate to 15℃ / min, heat it to 225℃ and bake it for 20 minutes; set the heating rate to 70℃ / min, heat it to 550℃ and calcine it for 30 minutes; set the heating rate to 55℃ / min, heat it to 900℃ and calcine it for 30 minutes; cool it and place it at room temperature for 2 hours to form a thick film copper layer; obtain a thick film circuit board.

[0044] Comparative Example 1: Based on Example 1, the microwave reaction method in the preparation of copper-based graphene was replaced by a calcination method; the rest was the same as Example 1; the specific differences are as follows:

[0045] Urea and graphene oxide in a mass ratio of 3:1 were added to deionized water in sequence and dispersed evenly, and hydrothermally reacted at 150°C for 8 hours; washed, dried and ground to obtain nitrogen-doped graphene; 10 parts of nitrogen-doped graphene were ultrasonically dispersed in 100 parts of dimethylformamide, and 16 parts of copper nitrate, 1.5 parts of titanium tetrachloride and 4 parts of boric acid were added and stirred for 3 to 6 hours; after drying, the mixture was placed in a nitrogen atmosphere, calcined at 200°C for 2 hours, and cooled to obtain copper-based graphene.

[0046] Comparative Example 2: Based on Example 1, the amount of copper-based graphene introduced was increased; the rest was the same as Example 1; the specific differences were as follows:

[0047] Step 1: 75 parts of copper particles (1 μm copper powder, 50 nm copper powder, and copper-based graphene in a ratio of 2.7:1:0.3) were placed in a 5 wt% dilute hydrochloric acid aqueous solution and ultrasonicated for 10 minutes, followed by rinsing with deionized water and ethanol in sequence to obtain pretreated copper particles;

[0048] Under a nitrogen atmosphere, 4 parts of the binder were added to 16 parts of a solvent (50:42:6:2 of dimethylformamide, terpineol, diethylene glycol butyl ether, and deionized water) and stirred evenly to obtain an organic vehicle; pretreated copper particles were added and stirred at 45°C for 30 minutes; 5 parts of glass powder were added and ground and mixed to obtain a thick film copper slurry.

[0049] Comparative Example 3: Based on Example 1, in the preparation of the binder, the molar amounts of methyl methacrylate and 2-butyl methacrylic acid were exchanged; the rest was the same as Example 1; the specific differences are as follows:

[0050] Under nitrogen atmosphere, methyl methacrylate, acrylamide, and 2-butyl-methacrylic acid in a molar ratio of 58:6:36 were added to toluene in sequence, and azobisisobutyronitrile (the amount added was 2 wt% of the mixed monomers) was added; the temperature was set to 75°C and stirred for 3 hours; cysteine ​​(the molar ratio of 2-butyl-methacrylic acid to cysteine ​​was 58:3) was added dropwise and the reaction was continued for 1 hour; the product was washed with n-hexane and dried to obtain an acrylic copolymer; (2) 10 parts of the acrylic copolymer was added to dimethylformamide, 1.5 parts of epoxy silane coupling agent KH560 were added, and the mixture was stirred and reacted at 80°C for 2 hours, washed, and dried to obtain a binder.

[0051] Comparative Example 4: Based on Example 1, the solvent was adjusted, dimethylformamide was not introduced, and pre-baking was not performed. The specific differences are as follows:

[0052] Step 1: 75 parts of copper particles (1 μm copper powder, 50 nm copper powder, and copper-based graphene in a ratio of 2.84:1:0.16) were placed in a 5 wt% dilute hydrochloric acid aqueous solution and ultrasonicated for 10 minutes, followed by rinsing with deionized water and ethanol in sequence to obtain pretreated copper particles;

[0053] Under nitrogen atmosphere, 4 parts of binder were added to 16 parts of solvent (93:5:2 terpineol, diethylene glycol butyl ether, deionized water) and stirred to obtain an organic vehicle; pretreated copper particles were added and stirred at 45°C for 30 minutes; 5 parts of glass powder were added and ground to obtain a thick film copper slurry;

[0054] Step 2: Print the copper slurry evenly on the ceramic substrate; place it in a sintering furnace, under a nitrogen atmosphere, set the heating rate to 15℃ / min at room temperature, heat it to 225℃ and bake it for 20 minutes; set the heating rate to 70℃ / min, heat it to 520℃ and calcine it for 30 minutes; set the heating rate to 55℃ / min, heat it to 880℃ and calcine it for 30 minutes; cool it and place it in a room temperature environment for 2 hours to form a thick film copper layer; and obtain a thick film circuit board.

[0055] Performance Test 1: The thick film circuit boards prepared in the examples and comparative examples were subjected to relevant performance tests; based on the standard method of GB / T17473.3: (1) using a digital ohmmeter to measure the square resistance of the thick film copper layer; (2) using a spiral puller and soldering a lead wire section on its surface (2×2mm) with the help of solder liquid. 2 ), and use a tensile testing machine to test its adhesion; the obtained data are shown in the following table:

[0056] sample Square resistance (mΩ / □) <![CDATA[Adhesion force (N / cm 2 )]]> Example 1 2.38 24.7 Example 2 2.43 24.2 Example 3 2.46 24.0 Comparative Example 1 2.56 23.3 Comparative Example 2 2.60 22.5 Comparative Example 3 2.91 22.1 Comparative Example 4 2.87 23.2

[0057] Conclusion: From the data in the above table, it can be seen that: the present application has obtained a thick-film copper metal ceramic-based thick-film circuit board with conductivity and adhesion by optimizing copper particles, binders and corresponding solvents. From the data of Comparative Example 1, it can be seen that: compared with the roasting process, the microwave reaction method can obtain better dispersed copper-based graphene with low surface defects, which makes the thick-film circuit board have better conductivity and adhesion; in Comparative Example 2, due to the high content of copper-based graphene, the uniform dispersion is reduced, resulting in a decline in performance; in Comparative Example 3, due to the exchange of the molar amounts of methyl methacrylate and 2-butyl-methacrylic acid in the binder, the residual carbon content is increased, resulting in an increase in square resistance; in Comparative Example 4, due to the adjustment of the solvent and pre-baking steps, the surface pore distribution is deteriorated, resulting in a decline in the quality of the thick-film copper layer, a decrease in adhesion, and an increase in square resistance.

[0058] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A process for preparing a thick film copper cermet-based thick film circuit board, characterized by: The following steps are involved: Step 1: (1) Wash the copper particles in dilute hydrochloric acid, deionized water, and ethanol in sequence; obtaining pretreated copper particles; (2) Under a nitrogen atmosphere, the binder is added to the solvent and stirred evenly to obtain an organic vehicle; the pretreated copper particles are added and stirred at a temperature of 40 to 50° C. for 20 to 30 minutes; the glass powder is added and ground and mixed to obtain a thick film copper slurry; Step 2: Print the copper paste evenly on the ceramic substrate; place it in a sintering furnace, pre-bake it at 150-160°C under a nitrogen atmosphere for 10-30 minutes; heat it to 220-230°C and bake it for 10-30 minutes; heat it to 450-550°C and calcine it once for 30-40 minutes; heat it to 800-900°C and calcine it again for 20-30 minutes; cool it and place it at room temperature for 1-2 hours to form a thick film copper layer; and obtain a thick film circuit board; The copper particles include 1±0.5 μm copper powder, 50±20 nm copper powder, and copper-based graphene in a mass ratio of (2.8-2.9):1:(0.1-0.2); The preparation method of the copper-based graphene comprises the following steps: adding urea and graphene oxide to deionized water in sequence, dispersing them uniformly, and subjecting them to a hydrothermal reaction at 120-150° C. for 6-12 hours; washing, drying, and grinding to obtain nitrogen-doped graphene; ultrasonically dispersing the graphene in dimethylformamide, adding copper nitrate, titanium tetrachloride, and boric acid, and stirring the mixture uniformly; placing the mixture in a microwave reactor under a nitrogen atmosphere, setting the power to 800-1000 W, and heating the mixture for 1-3 minutes; and filtering, washing, and drying to obtain the copper-based graphene.

2. The process for preparing a thick film copper metal ceramic-based thick film circuit board according to claim 1, characterized in that: The raw materials of the thick film copper paste include the following substances: by weight, 74 to 76 parts of copper particles, 4 to 6 parts of glass powder, 3 to 6 parts of binder, and 14 to 17 parts of solvent.

3. The process for preparing a thick film copper metal ceramic-based thick film circuit board according to claim 1, characterized in that: In the raw materials of the nitrogen-doped graphene, the mass ratio of urea to graphene oxide is 2-3:1; in the raw materials of the copper-based graphene, the ratio of nitrogen-doped graphene, copper nitrate, titanium tetrachloride, and boric acid is 1:(1.5-1.8):(0.1-0.2):(0.3-0.5).

4. The process for preparing a thick film copper metal ceramic-based thick film circuit board according to claim 1, characterized in that: The preparation method of the adhesive is as follows: (1) under a nitrogen atmosphere, methyl methacrylate, acrylamide, 2-butyl methacrylic acid, and azobisisobutyronitrile are sequentially added to toluene, and the temperature is set to 60-80° C. and stirred for reaction for 2-4 hours; cysteine ​​is added dropwise and the reaction is continued for 1-2 hours; the product is washed with n-hexane and dried to obtain an acrylic copolymer; (2) the acrylic copolymer is added to dimethylformamide, an epoxy silane coupling agent is added, the reaction is stirred at 80-85° C. for 1-2 hours, and the reaction is washed and dried to obtain an adhesive.

5. The process for preparing a thick film copper metal ceramic-based thick film circuit board according to claim 4, characterized in that: In the raw materials of the acrylic copolymer, the molar ratio of methyl methacrylate, acrylamide, 2-butyl methacrylic acid, and cysteine ​​is (35-38):(4-7):58:3; in the raw materials of the adhesive, the mass ratio of the acrylic copolymer to the epoxy silane coupling agent is 1:0.1-0.

2.

6. The process for preparing a thick film copper cermet-based thick film circuit board according to claim 1, characterized in that: The solvent comprises dimethylformamide, terpineol, diethylene glycol butyl ether and deionized water in a mass ratio of 50: (40-43): (5-8):

2.

7. The process for preparing a thick film copper cermet-based thick film circuit board according to claim 1, characterized in that: The heating rate of the pre-baking is 5-6°C / min; the heating rate of the intermediate baking is 10-15°C / min; the heating rate of the primary calcination is 65-75°C / min; and the heating rate of the secondary calcination is 50-60°C / min.

8. The process for preparing a thick film copper cermet-based thick film circuit board according to claim 1, characterized in that: The thickness of the thick copper layer is 30 to 80 μm.