A conductive copper paste, its preparation method and application
Patent Information
- Application Number
- CN202610819408.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-08
- Publication Date
- 2026-09-01
AI Technical Summary
[0002]导电铜浆广泛应用于厚膜电路、MLCC电极、压敏电阻电极等领域，由于铜的导电性能优异，并且成本也远远低于银，是理想的导电填料，然而，现有导电铜浆在实际应用中导电性、抗高温氧化性与工艺适应性难以兼顾，比如为了提高导电性，通常需要提高烧结温度，现有技术多为650-700℃，并使铜粉致密堆积，但高温下铜粉极易氧化，导致电阻率升高，现有有机载体，如粘结剂、溶剂、触变剂等在高温烧结后残碳量高，通常≥0.3-0.5%，残碳包裹铜颗粒会进一步阻断导电通路；另一方面，若降低烧结温度以避免氧化，则铜粉烧结不充分，导电网络不连续，电阻率难以降低
[0014]本发明具有的有益效果是：通过片状、树枝状、纳米三级铜粉的复配构建致密导电网络，同时采用苯并三氮唑与亚磷酸酯复配实现常温至高温的接力式抗氧化保护，并利用乙基纤维素与聚乙烯醇缩丁醛复配粘结剂、氢化蓖麻油与改性聚酰胺蜡复配触变剂、二乙二醇单丁醚与二乙二醇丁醚醋酸酯复配溶剂，使各组分在烧结过程中产生协同作用，降低铜粉氧化率以及残碳量，并通过三级铜粉复配，构建致密的导电网络，提升导电性能，解决低温烧结下导电性不足的问题。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of conductive copper paste technology, and in particular to a conductive copper paste, its preparation method, and its application. Background Technology
[0002] Conductive copper paste is widely used in thick-film circuits, MLCC electrodes, varistor electrodes, and other fields. Due to its excellent conductivity and significantly lower cost than silver, copper is an ideal conductive filler. However, existing conductive copper pastes struggle to balance conductivity, high-temperature oxidation resistance, and process adaptability in practical applications. For instance, to improve conductivity, the sintering temperature is typically increased, usually to 650-700℃, requiring dense packing of copper powder. However, copper powder is highly susceptible to oxidation at high temperatures, leading to increased resistivity. Existing organic carriers, such as binders, solvents, and thixotropic agents, have high residual carbon content after high-temperature sintering, typically ≥0.3-0.5%. This residual carbon encapsulates the copper particles, further blocking the conductive path. On the other hand, lowering the sintering temperature to avoid oxidation results in insufficient sintering of the copper powder, discontinuous conductive network, and difficulty in reducing resistivity.
[0003] Based on the above situation, it is necessary to design a conductive copper paste and its preparation method to solve the above problems. Summary of the Invention
[0004] This invention provides a conductive copper paste, its preparation method, and its application to solve the problems existing in the prior art.
[0005] The technical problem solved by this invention is achieved by the following technical solution: A conductive copper paste comprises the following components in parts by weight: 50-70 parts of flake copper powder; 10-30 parts of dendritic copper powder; 2-10 parts of nano copper powder; 3-8 parts of ethyl cellulose; 1-5 parts of polyvinyl butyral; 10-25 parts of diethylene glycol monobutyl ether; 5-20 parts of diethylene glycol butyl ether acetate; 0.1–0.5 parts of benzotriazole; Phosphite 0.1–0.6 parts; 0.2–0.7 parts of hydrogenated castor oil; 0.1 to 0.4 parts of modified polyamide wax; 0.1–0.3 parts of γ-aminopropyltriethoxysilane; Defoamer 0.05-0.2 parts.
[0006] Preferably, the particle size D50 of the flake copper powder is 1-10 μm and the thickness is 100-500 nm; the particle size D50 of the dendritic copper powder is 5-20 μm; and the particle size D50 of the nano copper powder is 10-100 nm.
[0007] Preferably, the weight ratio of the flake copper powder, dendritic copper powder and nano copper powder is (60-80):(15-30):(2-5).
[0008] Preferably, the weight ratio of ethyl cellulose to polyvinyl butyral is (2-4):1, the weight ratio of diethylene glycol monobutyl ether to diethylene glycol butyl ether acetate is (1.5-3):1, and the weight ratio of hydrogenated castor oil to modified polyamide wax is (1.5-3):1.
[0009] Preferably, the weight ratio of benzotriazole to phosphite is (1:1) to (1:2).
[0010] Preferably, the γ-aminopropyltriethoxysilane is present in 0.1 to 0.2 parts by weight.
[0011] The present invention provides a method for preparing conductive copper paste, comprising the following steps: S1: Preparation of thixotropic mother liquor: Diethylene glycol monobutyl ether and diethylene glycol butyl ether acetate are mixed in proportion, heated to 90-95°C, hydrogenated castor oil and modified polyamide wax are slowly added, stirred for 30-40 minutes until completely transparent, and cooled to below 50°C for later use. S2: Preparation of binder solution: Add ethyl cellulose and polyvinyl butyral to the remaining solvent, heat to 60-70℃, stir for 20-30 min until completely dissolved, and cool to room temperature; S3: Dispersing copper powder: Add flake copper powder, dendritic copper powder, and nano copper powder to a high-speed disperser, add γ-aminopropyltriethoxysilane, disperse at low speed for 10 min, then add the binder solution prepared in step 2, disperse at high speed for 30 min to obtain copper powder dispersion. S4: Copper paste preparation: Add the thixotropic mother liquor, benzotriazole, phosphite, and defoamer obtained in step 1 to the copper powder dispersion obtained in step 3, disperse at high speed for 20-30 minutes, and then grind with a three-roll mill until the particle size is ≤5μm to obtain the target conductive copper paste.
[0012] Preferably, in step 3, the linear velocity of low-speed dispersion is 3-5 m / s, and the linear velocity of high-speed dispersion is 10-15 m / s.
[0013] On the other hand, conductive copper paste can be used in the fabrication of varistor electrodes, multilayer ceramic capacitor electrodes, thermistor electrodes, printed circuit boards, or solar cell grid lines.
[0014] The beneficial effects of this invention are as follows: a dense conductive network is constructed by compounding sheet-like, dendritic, and nano-sized copper powders; a relay-style antioxidant protection from room temperature to high temperature is achieved by compounding benzotriazole and phosphite; and ethyl cellulose and polyvinyl butyral are used as binders, hydrogenated castor oil and modified polyamide wax are used as thixotropic agents, and diethylene glycol monobutyl ether and diethylene glycol butyl ether acetate are used as solvents, so that the components produce a synergistic effect during sintering, reducing the oxidation rate of copper powder and the amount of residual carbon. Furthermore, the dense conductive network constructed by the compounding of the three-level copper powders improves the conductivity and solves the problem of insufficient conductivity under low-temperature sintering. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0016] Figure 1 This is a schematic diagram of the preparation process provided by the present invention. Detailed Implementation
[0017] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.
[0018] This embodiment provides a conductive copper paste, the composition of which is shown in Table 1.
[0019] Table 1
[0020] Preparation method 1. Preparation of thixotropic mother liquor: Mix DEGB and DBA at a weight ratio of 14:8, heat to 92°C, slowly add HCO and modified polyamide wax while stirring, continue stirring for 35 minutes until completely transparent, cool to 45°C, and set aside.
[0021] 2. Preparation of adhesive solution: Add EC and PVB to the remaining DEGB and DBA (total solvent 22 parts, after deducting the part used in the mother liquor, about 10 parts remain), heat to 65°C, stir for 25 minutes until completely dissolved, cool to room temperature, and set aside.
[0022] 3. Dispersing copper powder: Add flake copper powder, dendritic copper powder, and nano copper powder to a high-speed disperser, add KH-550, and disperse at a low speed of 4m / s for 10min (so that the coupling agent can uniformly coat the surface of the copper powder). Then add the binder solution prepared in step 2 and disperse at a high speed of 12m / s for 30min to obtain a uniform copper powder dispersion.
[0023] 4. Prepare copper paste: Add the thixotropic mother liquor, BTA, phosphite and defoamer obtained in step / 1 to the copper powder dispersion, disperse at high speed for 25 minutes, and then grind it 3 times through a three-roll mill until the fineness of the slurry is ≤5μm to obtain conductive copper paste.
[0024] Performance testing: Viscosity at 25°C was measured using a Forte 4 cup viscometer; thixotropic index (TI = η6 / η60) was measured using a rotational viscometer (6 rpm and 60 rpm). Conductive copper paste was screen-printed onto alumina ceramic substrates and sintered at 600°C for 30 minutes under nitrogen protection (purity ≥99.99%). The resistivity of the sintered copper film was measured using the four-probe method; the oxidation rate and residual carbon content of copper powder were determined using thermogravimetric analysis (TGA); the adhesion strength between the coating and the substrate was measured using a universal tensile testing machine (pull-out method); the coating pass rate (number of substrates without sagging, pinholes, or screen blockage out of 100 substrates) and the resistivity change after 12 months of sealed storage at 25°C were also evaluated. The test results are shown in Table 2.
[0025] Table 2 Performance test results of Example 1
[0026] Example 2 In this embodiment, the copper powder ratio is adjusted, while other components remain the same as in Example 1. Specifically, it consists of 58 parts of flake copper powder, 25 parts of dendritic copper powder, and 2 parts of nano copper powder, prepared using the same method as in Example 1.
[0027] Performance test results: viscosity 12500 mPa·s, thixotropic index 3.8, sintering temperature 610℃, resistivity 2.05 μΩ·cm, oxidation rate 0.42%, residual carbon content 0.09%, bond strength 1.28 MPa, coating qualification rate 98%, resistivity change greater than 4.1% after 12 months of storage, bending radius 5 mm.
[0028] Example 3 In this embodiment, the copper powder ratio is adjusted, while other components are the same as in Example 1. Specifically, the ratio is 68 parts of flake copper powder, 15 parts of dendritic copper powder, and 4 parts of nano copper powder. The preparation method is the same as in Example 1.
[0029] Performance test results: viscosity 9800 mPa·s, thixotropic index 4.2, sintering temperature 590℃, resistivity 1.85 μΩ·cm, oxidation rate 0.35%, residual carbon content 0.07%, bond strength 1.42 MPa, coating qualification rate 99%, resistivity change greater than 2.8% after 12 months of storage, bending radius 3 mm.
[0030] Comparative Example 1 (Spherical copper powder instead of dendritic copper powder) Formula: 62 parts of flake copper powder, 20 parts of spherical micron copper powder (D50=12μm), 3 parts of nano copper powder, the rest are the same as in Example 1, and the preparation method is the same as in Example 1.
[0031] Performance test results: resistivity 2.65 μΩ·cm, oxidation rate 0.55%, residual carbon content 0.12%, thixotropic index 3.5, coating qualification rate 92%, and bonding strength 1.05 MPa, indicating that the branch structure of dendritic copper powder plays an irreplaceable role in connecting sheet copper powder and reducing resistivity.
[0032] Comparative Example 2 (using BTA as an antioxidant only) Formulation: Same as in Example 1, but without the addition of phosphite, and the amount of BTA is increased to 0.5 parts. The preparation method is the same as in Example 1.
[0033] Performance test results: resistivity 2.20 μΩ·cm, oxidation rate 1.8% (significantly increased), residual carbon content 0.10%, and bonding strength 1.30 MPa, indicating that BTA alone has insufficient antioxidant capacity at high temperatures, and that the combination of BTA and phosphite has a synergistic effect.
[0034] Comparative Example 3 (using only EC as an adhesive, without PVB) Formula: Same as Example 1, but without adding PVB, and the amount of EC is increased to 7 parts. The preparation method is the same as in Example 1.
[0035] Performance test results: resistivity 2.15 μΩ·cm, residual carbon content 0.28%, and adhesion strength 0.95 MPa, indicating that the combination of EC and PVB can significantly reduce residual carbon and improve adhesion.
[0036] Comparative Example 4 (using only HCO as a thixotropic agent, without adding modified polyamide wax) Formulation: Same as in Example 1, but without the addition of modified polyamide wax, and the amount of HCO is increased to 0.6 parts. The preparation method is the same as in Example 1.
[0037] Performance test results: Thixotropic index 2.8, coating pass rate 91%, and significant sedimentation after 3 months of storage. This indicates that only a combination of HCO and modified polyamide wax can achieve ideal thixotropic properties and storage stability.
[0038] Comparative Example 5 (single solvent DEGB, without DBA) Formulation: The solvent was all DEGB (22 parts), and the rest was the same as in Example 1. The preparation method was the same as in Example 1.
[0039] Performance test results: Gun clogging occurred during the spraying process, orange peel defects appeared on the film surface, and the pinhole rate increased significantly after sintering, with a pass rate of only 85%. This indicates that the combination of DEGB and DBA can achieve a smooth evaporation rate and improve process adaptability.
[0040] Table 3
[0041] As can be seen from Table 3, Examples 1-3 of the present invention all achieved comprehensive performance with resistivity ≤2.05μΩ·cm, oxidation rate ≤0.42%, residual carbon content ≤0.09%, thixotropic index 3.8-4.2, and coating qualification rate ≥98% at relatively low sintering temperatures (590-610℃). However, after changing the copper powder morphology, antioxidant, binder, thixotropic agent, or solvent system in Comparative Examples 1-5, at least one or more properties decreased significantly, proving that the synergistic effect between the components of the present invention is the key to achieving comprehensive performance.
[0042] Industrial applicability The conductive copper paste provided by this invention is readily available, has a simple preparation process, can be sintered at low temperatures of 580-620℃, has low energy consumption, and exhibits extremely low copper powder oxidation rate and negligible residual carbon content. It has excellent conductivity and can be widely used in the preparation of varistor electrodes, multilayer ceramic capacitor (MLCC) electrodes, thermistor (NTC) electrodes, printed circuit boards, and solar cell grid lines. It is especially suitable for electronic components that are sensitive to sintering temperature.
[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A conductive copper paste, characterized in that, The composition includes the following components in parts by weight: 50-70 parts of flake copper powder; 10-30 parts of dendritic copper powder; 2-10 parts of nano copper powder; 3-8 parts of ethyl cellulose; 1-5 parts of polyvinyl butyral; 10-25 parts of diethylene glycol monobutyl ether; 5-20 parts of diethylene glycol butyl ether acetate; 0.1–0.5 parts of benzotriazole; Phosphite 0.1–0.6 parts; 0.2–0.7 parts of hydrogenated castor oil; 0.1 to 0.4 parts of modified polyamide wax; 0.1–0.3 parts of γ-aminopropyltriethoxysilane; Defoamer 0.05-0.2 parts.
2. The conductive copper paste according to claim 1, characterized in that, The flake copper powder has a particle size D50 of 1-10 μm and a thickness of 100-500 nm; the dendritic copper powder has a particle size D50 of 5-20 μm; and the nano copper powder has a particle size D50 of 10-100 nm.
3. The conductive copper paste according to claim 1 or 2, characterized in that, The weight ratio of the flake copper powder, dendritic copper powder and nano copper powder is (60-80):(15-30):(2-5).
4. The conductive copper paste according to claim 1, characterized in that, The weight ratio of ethyl cellulose to polyvinyl butyral is (2-4):1, the weight ratio of diethylene glycol monobutyl ether to diethylene glycol butyl ether acetate is (1.5-3):1, and the weight ratio of hydrogenated castor oil to modified polyamide wax is (1.5-3):
1.
5. The conductive copper paste according to claim 1, characterized in that, The weight ratio of benzotriazole to phosphite is (1:1)-(1:2).
6. The conductive copper paste according to claim 1, characterized in that, The γ-aminopropyltriethoxysilane is present in parts by weight of 0.1 to 0.
2.
7. A method for preparing conductive copper paste according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Preparation of thixotropic mother liquor: Diethylene glycol monobutyl ether and diethylene glycol butyl ether acetate are mixed in proportion, heated to 90-95°C, hydrogenated castor oil and modified polyamide wax are slowly added, stirred for 30-40 minutes until completely transparent, and cooled to below 50°C for later use. S2: Preparation of binder solution: Add ethyl cellulose and polyvinyl butyral to the remaining solvent, heat to 60-70℃, stir for 20-30 min until completely dissolved, and cool to room temperature; S3: Dispersing copper powder: Add flake copper powder, dendritic copper powder, and nano copper powder to a high-speed disperser, add γ-aminopropyltriethoxysilane, disperse at low speed for 10 min, then add the binder solution prepared in step 2, disperse at high speed for 30 min to obtain copper powder dispersion. S4: Copper paste preparation: Add the thixotropic mother liquor, benzotriazole, phosphite, and defoamer obtained in step 1 to the copper powder dispersion obtained in step 3, disperse at high speed for 20-30 minutes, and then grind with a three-roll mill until the particle size is ≤5μm to obtain the target conductive copper paste.
8. The preparation method according to claim 7, characterized in that, In step 3, the linear velocity of low-speed dispersion is 3-5 m / s, and the linear velocity of high-speed dispersion is 10-15 m / s.
9. The application of a conductive copper paste according to any one of claims 1 to 6 or a conductive copper paste prepared by the preparation method according to claim 7 in the preparation of varistor electrodes, multilayer ceramic capacitor electrodes, thermistor electrodes, printed circuit boards or solar cell grid lines.