Graphene coated copper powder thermosetting conductive adhesive film and preparation method thereof

Abstract

The invention belongs to the technical field of conductive adhesives, and particularly relates to a graphene coated copper powder thermosetting conductive adhesive film and a preparation method thereof. The graphene-coated copper powder thermosetting conductive adhesive film comprises a thermosetting resin matrix and a graphene-coated copper powder conductive filler, the graphene coated copper powder conductive filler comprises a copper powder inner layer and a graphene coating layer, and the graphene coating layer is composed of graphene and a low-melting-point metal binding phase. The preparation method comprises the following steps: mixing graphene powder and low-melting-point metal powder, heating in an inert atmosphere to melt the low-melting-point metal powder to obtain a graphene coating material, and coating copper powder in a fluidized bed with the graphene coating material in an atomization spraying manner to obtain the graphene-coated copper powder conductive filler, and uniformly mixing the conductive filler with a thermosetting resin glue solution, and carrying out hot-pressing curing to obtain the graphene coated copper powder thermosetting conductive adhesive film. The conductive adhesive film has the advantages of good conductivity and good stability, the preparation process is simple, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the field of conductive adhesive technology, specifically relating to a graphene-coated copper powder thermosetting conductive adhesive film and its preparation method. Background Technology

[0002] Conductive adhesive is a type of adhesive that exhibits a certain degree of conductivity after curing. It is typically composed of conductive fillers, a resin matrix, and additives. The resin matrix primarily serves as a binder and includes epoxy resin, acrylic resin, urethane resin, silicone rubber resin, bismaleimide resin, phenolic resin, melamine resin, and polyimide resin. Conductive fillers are used to form conductive pathways and can include carbon powder, silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-plated copper powder, and metal-plated resin balls. Copper powder is widely used due to its excellent conductivity and low cost, but its application in conductive adhesives requiring high conductivity and high adhesion stability has some limitations. On the one hand, increasing the filler content is necessary to improve conductivity, but a high filler content leads to higher costs and reduces the amount of binding resin, which in turn reduces the adhesive strength and adhesion stability of the conductive adhesive film.

[0003] Graphene is a nanomaterial (GNP) with a hexagonal two-dimensional lattice structure composed of carbon atoms. It has the advantages of high strength, good thermal conductivity, and good electrical conductivity, and has been hailed as an excellent reinforcement for metal matrix composites since its discovery. Due to the high electrical conductivity of graphene and the excellent electrical conductivity of copper, graphene-coated copper powder has been widely used in electronic materials, conductive coatings, electromagnetic shielding, heat transfer materials, and mechanical reinforcement materials.

[0004] The main methods for preparing graphene-coated copper powder include powder metallurgy mixing, in-situ synthesis, electrochemical deposition, and chemical vapor deposition. Among these, powder metallurgy mixing offers advantages such as simple processing and low equipment requirements, but the poor wettability between graphene and copper powder leads to poor coating results. In-situ synthesis and electrochemical deposition require strict process control, resulting in graphene coatings with poor quality stability. Chemical vapor deposition offers excellent coating results, but it demands sophisticated equipment and involves complex processes. None of these methods are suitable for the industrial application and cost constraints of conductive films. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a graphene-coated copper powder thermosetting conductive adhesive film.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned graphene-coated copper powder thermosetting conductive film.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A graphene-coated copper powder thermosetting conductive film includes a thermosetting resin matrix and a graphene-coated copper powder conductive filler; the graphene-coated copper powder conductive filler includes a copper powder inner layer and a graphene coating layer, wherein the graphene coating layer is composed of graphene and a low-melting-point metal binder phase.

[0009] Furthermore, the thermosetting resin matrix is ​​a thermosetting phenolic resin, epoxy resin, urethane resin, melamine resin, alkyd resin, or polyimide resin.

[0010] Furthermore, the graphene-coated copper powder conductive filler has a mass percentage content of 30-70% in the conductive film.

[0011] Furthermore, the inner layer of copper powder is preferably dendritic copper powder with a size of 5-50 μm. Dendritic copper powder is a conventional commercial raw material in the art. Compared with conventional spherical copper powder, the dendritic copper powder used in this invention has a higher specific surface area and better conductivity, resulting in better bonding with the graphene coating layer and better conductivity of the resulting conductive film.

[0012] Furthermore, the mass of the graphene coating layer is 1 to 20% of the mass of the copper powder inner layer.

[0013] Furthermore, the graphene has a size of 0.01~5μm. Preferably, the size is 50~500nm. Graphene with the above size can achieve a good coating effect and has a good cost advantage.

[0014] Furthermore, the low-melting-point metal binder phase includes any one or more alloys of Zn, Bi, Sn, Pb, Cd, and In.

[0015] This invention uses a low-melting-point metal binder phase as the wetting binder phase between graphene and copper powder, which can significantly improve the coating and bonding effect of graphene and copper powder, thereby significantly improving the conductivity and stability of the resulting conductive adhesive.

[0016] Furthermore, in the graphene coating layer, the mass ratio of graphene to the low-melting-point metal binder phase is 0.1 to 1:1.

[0017] The preparation method of the above-mentioned graphene-coated copper powder thermosetting conductive adhesive film includes the following preparation steps:

[0018] (1) After mixing graphene powder with low melting point metal powder, heat the mixture under an inert atmosphere to melt the low melting point metal powder to obtain graphene coating material;

[0019] (2) Add copper powder into a fluidized bed, and then coat the copper powder with the graphene coating material from step (1) by atomization spraying to obtain graphene-coated copper powder conductive filler.

[0020] (3) The graphene-coated copper powder conductive filler is mixed evenly with thermosetting resin liquid and then hot-pressed and cured to obtain a graphene-coated copper powder thermosetting conductive film.

[0021] Furthermore, in step (1), the temperature at which the low-melting-point metal powder is melted is 50~150℃ higher than the melting point of the low-melting-point metal powder; in step (2), the temperature inside the fluidized bed is controlled below the melting point temperature of the low-melting-point metal powder; and the atomization spraying adopts gas atomization spraying or ultrasonic atomization spraying.

[0022] This invention uses a low-melting-point metal as the coating binder for graphene, which has a low melting point and requires less sophisticated atomization equipment. Copper powder suspended in a fluidized bed is uniformly coated and modified via atomization spraying. The low-melting-point metal solidifies and bonds graphene to the copper powder surface, forming a granular graphene coating layer. This further increases the specific surface area of ​​the copper powder, improving its adhesion to the thermosetting resin matrix and thus enhancing the stability and adhesion of the resulting conductive adhesive. Furthermore, the graphene composite coating layer synergistically improves the conductivity of the copper powder, thereby enhancing the conductivity of the resulting conductive adhesive.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) The present invention uses graphene to coat conductive copper powder, which can significantly improve the conductivity and stability of the resulting conductive adhesive film. Furthermore, the granular graphene coating layer formed by low-melting-point metal curing and bonding can further increase the specific surface area of ​​copper powder, improve the bonding force with the thermosetting resin matrix, and help improve the stability and adhesion of the resulting conductive adhesive.

[0025] (2) The present invention uses a low melting point metal binder phase as the wetting binder phase between graphene and copper powder, which can significantly improve the coating and bonding effect of graphene and copper powder. Moreover, the coating process is simple, has low equipment requirements, low preparation cost, and is easy to industrialize. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0027] Example 1

[0028] A method for preparing a graphene-coated copper powder thermosetting conductive adhesive film includes the following preparation steps:

[0029] (1) Commercial graphene powder with an average particle size of 80~100nm and tin powder (average particle size of 5~10μm) are mixed at a mass ratio of 0.4:1 and added to the heating furnace of the gas atomization device. The mixture is heated to 350℃ under an inert atmosphere to melt the tin powder and obtain graphene coating material.

[0030] (2) Commercial dendritic copper powder with an average particle size of 15~25μm is added to an inert airflow fluidized bed. Then, the graphene coating material from step (1) is atomized and uniformly sprayed into the fluidized bed to coat the copper powder. The mass of the graphene coating material added is 10% of the mass of the copper powder. The temperature in the fluidized bed is controlled at 150℃. After the coating is completed, the material is cooled and discharged to obtain graphene-coated copper powder conductive filler.

[0031] (3) The graphene-coated copper powder conductive filler and the thermosetting epoxy resin liquid are mixed evenly at a mass ratio of 1:1 and then hot-pressed and cured to obtain a graphene-coated copper powder thermosetting conductive film.

[0032] The conductive film obtained in this embodiment has an initial resistivity (iSR) of 3.2 × 10⁻⁶. -3 The resistivity (htSR) after high-temperature treatment at 85℃ for 12 hours is 3.8 × 10 Ω·cm. -3 Ω·cm; resistivity after 100 repeated 90° bends is 4.7 × 10⁻⁶ Ω·cm. -3 Ω·cm.

[0033] Comparative Example 1

[0034] Compared to Example 1, this comparative example uses a mixture of graphene powder, tin powder, and dendritic copper powder to prepare a conductive film, including the following preparation steps:

[0035] (1) Commercial graphene powder with an average particle size of 80~100nm is mixed with tin powder (average particle size of 5~10μm) and commercial dendritic copper powder with an average particle size of 15~25μm. The mass ratio of graphene powder to tin powder is 0.4:1, and the total mass of graphene powder and tin powder is 10% of the mass of copper powder to obtain a composite conductive filler.

[0036] (2) The composite conductive filler and thermosetting epoxy resin are mixed evenly at a mass ratio of 1:1 and then hot-pressed and cured to obtain a graphene composite copper powder thermosetting conductive film.

[0037] The conductive film obtained in this comparative example had an initial resistivity (iSR) of 8.5 × 10⁻⁶. -3 The resistivity (htSR) after high-temperature treatment at 85℃ for 12 hours is 1.3 × 10 Ω·cm. -2 Ω·cm; after being repeatedly bent at 90° 100 times, the resistivity is 2.4 × 10⁻⁶ Ω·cm. -2 Ω·cm.

[0038] The comparison results with Example 1 show that the present invention can significantly improve the conductivity, heat resistance and deformation resistance of the obtained conductive adhesive by forming a coating layer structure composed of graphene and low melting point metal binder.

[0039] Example 2

[0040] A method for preparing a graphene-coated copper powder thermosetting conductive adhesive film includes the following preparation steps:

[0041] (1) Commercial graphene powder with an average particle size of 50~80nm and zinc powder (average particle size of 5~10μm) are mixed at a mass ratio of 0.8:1 and added to the heating furnace of the gas atomization device. The mixture is heated to 520℃ under an inert atmosphere to melt the zinc powder and obtain graphene coating material.

[0042] (2) Commercial dendritic copper powder with an average particle size of 15~25μm is added to an inert airflow fluidized bed. Then, the graphene coating material from step (1) is atomized and uniformly sprayed into the fluidized bed to coat the copper powder. The mass of the graphene coating material added is 15% of the mass of the copper powder. The temperature in the fluidized bed is controlled at 300℃. After the coating is completed, the material is cooled and discharged to obtain graphene-coated copper powder conductive filler.

[0043] (3) The graphene-coated copper powder conductive filler and the thermosetting epoxy resin liquid are mixed evenly at a mass ratio of 1:2, and then hot-pressed and cured to obtain a graphene-coated copper powder thermosetting conductive film.

[0044] The conductive film obtained in this embodiment has an initial resistivity (iSR) of 5.6 × 10⁻⁶. -2 The resistivity (htSR) after high-temperature treatment at 85℃ for 12 hours is 7.0 × 10 Ω·cm. -2 Ω·cm; after being repeatedly bent at 90° 100 times, the resistivity is 8.6×10 Ω·cm. -2 Ω·cm.

[0045] Comparative Example 2

[0046] Compared to Example 2, this comparative example uses a mixture of graphene powder, zinc powder, and dendritic copper powder to prepare a conductive film, including the following preparation steps:

[0047] (1) Commercial graphene powder with an average particle size of 50~80nm is mixed with zinc powder (average particle size of 5~10μm) and commercial dendritic copper powder with an average particle size of 15~25μm. The mass ratio of graphene powder to zinc powder is 0.8:1, and the total mass of graphene powder and zinc powder is 15% of the mass of copper powder to obtain a composite conductive filler.

[0048] (2) The composite conductive filler and thermosetting epoxy resin are mixed evenly at a mass ratio of 1:2, and then hot-pressed and cured to obtain a graphene composite copper powder thermosetting conductive film.

[0049] The conductive film obtained in this comparative example had an initial resistivity (iSR) of 0.12 Ω·cm; a resistivity (htSR) of 0.20 Ω·cm after being treated at 85℃ for 12 hours; and a resistivity of 0.33 Ω·cm after being repeatedly bent at 90° for 100 times.

[0050] The comparison results with Example 2 show that the present invention can significantly improve the conductivity, heat resistance and deformation resistance of the obtained conductive adhesive by forming a coating layer structure composed of graphene and low melting point metal binder.

[0051] Example 3

[0052] A method for preparing a graphene-coated copper powder thermosetting conductive adhesive film includes the following preparation steps:

[0053] (1) Commercial graphene powder with an average particle size of 150~200nm and Sn-Bi alloy powder (average particle size of 5~10μm) are mixed at a mass ratio of 0.2:1 and added to the heating furnace of the gas atomization device. The alloy powder is heated to 260℃ under an inert atmosphere to melt it and obtain graphene coating material.

[0054] (2) Commercial dendritic copper powder with an average particle size of 15~25μm is added to an inert airflow fluidized bed. Then, the graphene coating material from step (1) is atomized and uniformly sprayed into the fluidized bed to coat the copper powder. The mass of the graphene coating material added is 20% of the mass of the copper powder. The temperature in the fluidized bed is controlled at 100℃. After the coating is completed, the material is cooled and discharged to obtain graphene-coated copper powder conductive filler.

[0055] (3) The graphene-coated copper powder conductive filler and the thermosetting epoxy resin liquid are mixed evenly at a mass ratio of 2:1, and then hot-pressed and cured to obtain a graphene-coated copper powder thermosetting conductive film.

[0056] The conductive film obtained in this embodiment has an initial resistivity (iSR) of 1.8 × 10⁻⁶. -5 The resistivity (htSR) after high-temperature treatment at 85℃ for 12 hours is 2.1 × 10 Ω·cm. -5 Ω·cm; after being repeatedly bent at 90° 100 times, the resistivity is 3.4 × 10⁻⁶ Ω·cm. -5 Ω·cm.

[0057] Comparative Example 3

[0058] Compared to Example 3, this comparative example uses a mixture of graphene powder, Sn-Bi alloy powder, and dendritic copper powder to prepare a conductive film, including the following preparation steps:

[0059] (1) Commercial graphene powder with an average particle size of 150~200nm is mixed with Sn-Bi alloy powder (average particle size of 5~10μm) and commercial dendritic copper powder with an average particle size of 15~25μm. The mass ratio of graphene powder to Sn-Bi alloy powder is 0.2:1, and the total mass of graphene powder and Sn-Bi alloy powder is 20% of the mass of copper powder to obtain a composite conductive filler.

[0060] (2) The composite conductive filler and thermosetting epoxy resin are mixed evenly at a mass ratio of 2:1, and then hot-pressed and cured to obtain a graphene composite copper powder thermosetting conductive film.

[0061] The conductive film obtained in this comparative example had an initial resistivity (iSR) of 9.5 × 10⁻⁶. -5 The resistivity (htSR) after high-temperature treatment at 85℃ for 12 hours is 2.7 × 10 Ω·cm. -4 Ω·cm; after being repeatedly bent at 90° 100 times, the resistivity is 6.8 × 10⁻⁶ Ω·cm. -4 Ω·cm.

[0062] The comparison results with Example 3 show that the present invention can significantly improve the conductivity, heat resistance and deformation resistance of the obtained conductive adhesive by forming a coating layer structure composed of graphene and low melting point metal binder.

[0063] Example 4

[0064] A method for preparing a graphene-coated copper powder thermosetting conductive adhesive film includes the following preparation steps:

[0065] (1) Commercial graphene powder with an average particle size of 300~400nm and Zn-Sn alloy powder (average particle size of 5~10μm) are mixed at a mass ratio of 0.6:1 and added to the heating furnace of the gas atomization device. The alloy powder is heated to 350℃ under an inert atmosphere to melt it and obtain graphene coating material.

[0066] (2) Commercial dendritic copper powder with an average particle size of 15~25μm is added to an inert airflow fluidized bed. Then, the graphene coating material from step (1) is atomized and uniformly sprayed into the fluidized bed to coat the copper powder. The mass of the graphene coating material added is 5% of the mass of the copper powder. The temperature in the fluidized bed is controlled at 150℃. After the coating is completed, the material is cooled and discharged to obtain graphene-coated copper powder conductive filler.

[0067] (3) The graphene-coated copper powder conductive filler and the thermosetting epoxy resin liquid are mixed evenly at a mass ratio of 1:1.5, and then hot-pressed and cured to obtain a graphene-coated copper powder thermosetting conductive film.

[0068] The conductive film obtained in this embodiment has an initial resistivity (iSR) of 1.5 × 10⁻⁶. -2The resistivity (htSR) after high-temperature treatment at 85℃ for 12 hours is 1.9 × 10 Ω·cm. -2 Ω·cm; after being repeatedly bent at 90° 100 times, the resistivity is 2.2×10 Ω·cm. -2 Ω·cm.

[0069] Comparative Example 4

[0070] Compared to Example 4, this comparative example uses a mixture of graphene powder, Zn-Sn alloy powder, and dendritic copper powder to prepare a conductive film, including the following preparation steps:

[0071] (1) Commercial graphene powder with an average particle size of 300~400nm is mixed with Zn-Sn alloy powder (average particle size of 5~10μm) and commercial dendritic copper powder with an average particle size of 15~25μm. The mass ratio of graphene powder to Zn-Sn alloy powder is 0.6:1, and the total mass of graphene powder and Zn-Sn alloy powder is 5% of the mass of copper powder to obtain a composite conductive filler.

[0072] (2) The composite conductive filler and thermosetting epoxy resin are mixed evenly at a mass ratio of 1:1.5 and then hot-pressed and cured to obtain a graphene composite copper powder thermosetting conductive film.

[0073] The conductive film obtained in this comparative example had an initial resistivity (iSR) of 6.1 × 10⁻⁶. -2 The resistivity (htSR) after high-temperature treatment at 85℃ for 12 hours is 8.5 × 10 Ω·cm. -2 Ω·cm; resistivity after 100 repeated 90° bends is 9.7 × 10⁻⁶ Ω·cm. -2 Ω·cm.

[0074] The comparison results with Example 4 show that the present invention can significantly improve the conductivity, heat resistance and deformation resistance of the obtained conductive adhesive by forming a coating layer structure composed of graphene and low melting point metal binder.

[0075] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A graphene-coated copper powder thermosetting conductive adhesive film, characterized in that: It includes a thermosetting resin matrix and graphene-coated copper powder conductive filler; the graphene-coated copper powder conductive filler includes a copper powder inner layer and a graphene coating layer, the graphene coating layer being composed of graphene and a low-melting-point metal binder phase.

2. The graphene-coated copper powder thermosetting conductive adhesive film according to claim 1, characterized in that: The thermosetting resin matrix is ​​a thermosetting phenolic resin, epoxy resin, urethane resin, melamine resin, alkyd resin, or polyimide resin.

3. The graphene-coated copper powder thermosetting conductive film according to claim 1, characterized in that: The graphene-coated copper powder conductive filler has a mass percentage content of 30-70% in the conductive film.

4. The graphene-coated copper powder thermosetting conductive adhesive film according to claim 1, characterized in that: The inner layer of the copper powder is dendritic copper powder with a size of 5~50μm.

5. The graphene-coated copper powder thermosetting conductive film according to claim 1, characterized in that: The mass of the graphene coating layer is 1 to 20% of the mass of the copper powder inner layer.

6. The graphene-coated copper powder thermosetting conductive adhesive film according to claim 1, characterized in that: The graphene has a size of 0.01~5μm.

7. The graphene-coated copper powder thermosetting conductive film according to claim 1, characterized in that: The low-melting-point metal binder phase includes any one or more alloys of Zn, Bi, Sn, Pb, Cd, and In.

8. The graphene-coated copper powder thermosetting conductive adhesive film according to claim 1, characterized in that: In the graphene coating layer, the mass ratio of graphene to the low-melting-point metal binder phase is 0.1 to 1:

1.

9. A method for preparing a graphene-coated copper powder thermosetting conductive adhesive film according to any one of claims 1 to 8, characterized in that... The preparation steps include the following: (1) After mixing graphene powder with low melting point metal powder, heat the mixture under an inert atmosphere to melt the low melting point metal powder to obtain graphene coating material; (2) Add copper powder into a fluidized bed, and then coat the copper powder with the graphene coating material from step (1) by atomization spraying to obtain graphene-coated copper powder conductive filler. (3) The graphene-coated copper powder conductive filler is mixed evenly with thermosetting resin liquid and then hot-pressed and cured to obtain a graphene-coated copper powder thermosetting conductive film.

10. The method for preparing a graphene-coated copper powder thermosetting conductive film according to claim 9, characterized in that: In step (1), the heating temperature that melts the low-melting-point metal powder is 50~150℃ higher than the melting point of the low-melting-point metal powder; in step (2), the temperature inside the fluidized bed is controlled below the melting point temperature of the low-melting-point metal powder; and the atomization spraying adopts gas atomization spraying or ultrasonic atomization spraying.