CN118814005A - A method for preparing a high thermal conductivity Cu-Cr-GR composite material - Google Patents

Abstract

A method for preparing a high thermal conductivity Cu-Cr-GR composite material comprises the following steps: (1) material pretreatment; (2) preparation of a binder and chromium and graphite slurry; (3) slurry coating; (4) spark plasma sintering; (5) aging treatment. The present invention improves the interface properties of copper-graphite by adding the transition element Cr and adopting an aging treatment method. After sintering, the Cr atoms dissolved in the copper matrix diffuse to the interface after aging treatment and react with graphite to form chromium carbides, thereby reducing the interfacial gap of copper-graphite and effectively improving the thermal conductivity of the composite material; the copper matrix is introduced in the form of copper foil, and the graphite orientation is directional-controlled by a tape casting method plus a lamination method, thereby further improving the thermal conductivity of the composite material, preparing a high thermal conductivity Cu-Cr-GR composite material, and solving the problem that it is difficult to control the orientation of graphite in the copper matrix when preparing copper-graphite composite materials by the traditional powder metallurgy method, thereby limiting the improvement of its thermal conductivity.

Description

A method for preparing a high thermal conductivity Cu-Cr-GR composite material

Technical Field

The invention belongs to the technical field of high thermal conductivity strengthening of copper-graphite composite materials, and specifically relates to a method for preparing a high thermal conductivity Cu-Cr-GR composite material, which is prepared by introducing a transition element Cr and performing aging treatment, and adopting a lamination method and spark plasma sintering.

Background Art

As electronic components develop towards high power, high frequency and miniaturization, traditional electronic packaging materials such as W-Cu and Mo-Cu can no longer meet their higher performance requirements. Copper-graphite composite materials have gradually become a new generation of electronic packaging materials due to their excellent thermal conductivity, low thermal expansion coefficient and density.

It is an excellent method to use graphite with high thermal conductivity in the extension direction to strengthen the thermal properties of the copper matrix. Graphite has the characteristics of high thermal conductivity, low thermal expansion coefficient and low density. Compared with other carbon materials, graphite has a wider source and lower price. Copper-graphite composite materials are excellent high thermal conductivity materials.

The traditional method of preparing copper-graphite composite materials is to evenly mix copper matrix powder and graphite and then sinter them. However, the wettability between copper matrix and graphite is poor, there is a gap between copper and graphite, and it is impossible to ensure that the graphite is fully distributed in the transverse plane of the copper matrix in the span direction, making it difficult to exert its excellent thermal conductivity. It is an important topic of the times to give full play to the design freedom of materials, explore the preparation process of high-performance and low-cost copper-graphite composite materials, and promote the development of high-performance electronic component packaging materials.

Summary of the invention

The present invention provides a preparation method of a high thermal conductivity Cu-Cr-GR composite material, wherein a copper matrix is introduced in the form of copper foil, a transition element Cr and copper-plated graphite are added to the copper matrix by a tape casting method, and then spark plasma sintering is performed by a stacking method, so that the orientation of graphite in the copper matrix is directionally regulated and the thermal conductivity of the composite material is improved, and finally the sintered sample is subjected to aging treatment, so that the Cr atoms dissolved in the matrix after sintering are promoted to diffuse to the boundary, the problem of poor wettability between copper and graphite is reduced, and the comprehensive performance of the material is improved.

The technical solution of the present invention:

A method for preparing a high thermal conductivity Cu-Cr-GR composite material comprises the following steps:

(1) Material pretreatment

The copper foil and the copper-plated graphite are respectively placed in an HCl solution for ultrasonic cleaning to remove surface impurities and oxides, the copper foil is cut into a certain size and shape, the copper-plated graphite is sieved with a sieve, and the copper foil and the sieved copper-plated graphite are cleaned with anhydrous ethanol until no obvious dirt appears on the surface, and then the required materials are placed in anhydrous ethanol for storage;

(2) Preparation of binder, chromium and graphite slurry

Add polyvinyl butyral and anhydrous ethanol in a certain proportion to a beaker, stir magnetically at 30°C until the mixture is clear and free of colloid, take out and let stand until no bubbles are generated, thereby preparing a binder, add a certain amount of high-purity chromium powder and the copper-plated graphite in step (1) to the prepared binder, stir magnetically for 30 minutes until the mixture is evenly mixed, thereby preparing a graphite slurry;

(3) Slurry coating

Using a scraper, the graphite slurry prepared in step (2) is evenly coated on one side of the copper foil in step (1), and the copper foil coated with the slurry is placed in a tube furnace for calcination and reduction;

(4) Spark plasma sintering

The copper foil coated with the slurry in step (3) is sequentially placed in the same direction into the graphite mold, the graphite mold is pre-pressed and compacted, and then placed into the spark plasma sintering furnace chamber, and sintered according to the set program under a vacuum environment to obtain a Cu-Cr-GR composite material;

(5) Timeliness treatment

After removing the carbon paper from the surface of the composite material obtained in step (4), the composite material is placed in a tubular furnace and subjected to aging treatment by passing high-purity hydrogen gas, thereby finally obtaining a high thermal conductivity Cu-Cr-GR composite material.

The copper foil in step (1) is an electrolytic copper foil, and its size and shape are a round piece with a thickness of 30 μm and a diameter of 25 mm.

The specification of the copper-plated graphite required in step (1) is 500 μm.

In the step (1), the ultrasonic cleaning is performed for 30 min, and the ultrasonic cleaner used is a JK-5200B ultrasonic cleaner with a power of 200 W and a frequency of 40 KHz.

In the step (2), the mass ratio of polyvinyl butyral to anhydrous ethanol is 1:8.

In the step (2), the content of chromium powder is 0.25 wt%, and the content of copper-plated graphite is 20 vol%.

The magnetic stirrer used in step (2) is a DF-101S heat-collecting magnetic stirrer.

In the step (3), the content of chromium powder in the slurry coated on the single copper foil is 0.25 wt%, and the content of copper-plated graphite is 5.54 wt%.

The model of the tube furnace in step (3) is GSL-1200X, and the setting program is as follows: increase the temperature from room temperature to 200°C at 10°C/min, keep it at that temperature for 2 h, and then cool it to room temperature with the furnace.

The flow rate of hydrogen introduced in step (3) is 300 mL/min.

The total mass of the copper foil placed in the graphite mold in step (4) is 25 g.

The pre-pressing pressure in step (4) is 10 MPa.

The spark plasma sintering system in step (4) is LaboxTM-300, and a thermocouple is used for temperature measurement. The program is set as follows: the temperature is raised to 600°C at a rate of 100°C/min and kept at that temperature for 5 min; then the temperature is raised to 920°C at a rate of 100°C/min, during which the pressure is increased from 10 MPa to 50 MPa, and the temperature is kept at that temperature for 5 min before rapid cooling.

The model of the tube furnace in step (5) is GSL-1200X, and the setting program is as follows: increase the temperature from room temperature to 400-500°C at 10°C/min, keep the temperature for 2 h, and then cool to room temperature with the furnace.

The flow rate of hydrogen introduced in step (5) is 300 mL/min.

The beneficial effects of the present invention are as follows: the present invention improves the interface properties of copper-graphite by adding the transition element Cr and adopting an aging treatment method; the Cr atoms dissolved in the copper matrix after sintering diffuse to the interface after aging treatment and react with graphite to generate chromium carbide, thereby reducing the interface gap between copper and graphite and effectively improving the thermal conductivity of the composite material; the present invention introduces the copper matrix in the form of copper foil and adopts a casting method plus a lamination method to directionally control the orientation of graphite, thereby further improving the thermal conductivity of the composite material, and finally preparing a high thermal conductivity Cu-Cr-GR composite material, thereby solving the problem that it is difficult to control the orientation of graphite in the copper matrix when preparing the copper-graphite composite material by the traditional powder metallurgy method, thereby limiting the improvement of its thermal conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a surface morphology of the Cu-Cr-GR composite material after aging treatment at 450°C;

FIG2 is an X-ray diffraction pattern of the Cu-Cr-GR, Cu-Cr-GR 400°C aging treatment, Cu-Cr-GR 450°C aging treatment and Cu-Cr-GR 500°C aging treatment composite materials;

FIG3 is an X-ray diffraction pattern of the red dashed box area in FIG2 .

DETAILED DESCRIPTION

The present invention is further described below with reference to the accompanying drawings and specific implementation examples.

Embodiment 1:

The Cu-GR composite material in this embodiment is prepared by tape casting, calcination reduction, lamination, spark plasma sintering and aging treatment, wherein the volume fraction of copper-plated graphite is 20%, and the rest is electrolytic copper foil.

The preparation method of the Cu-GR composite material in this embodiment is as follows:

(1) Material pretreatment

HCl solution was used to ultrasonically clean 30 μm electrolytic copper foil and copper-plated graphite at room temperature for 30 min. After cleaning, the copper foil was cut into discs with a diameter of 25 mm and the copper-plated graphite was sieved through 500 μm. Polyvinyl butyral and anhydrous ethanol were added into a beaker at a mass ratio of 1:8 and magnetically stirred at 30 °C until clear and free of colloid. The mixture was taken out and allowed to stand until no bubbles were generated to prepare a binder. 1.38 g of 500 μm copper-plated graphite was weighed and added into the prepared binder and magnetically stirred for 30 min until uniformly mixed to prepare a graphite slurry.

(2) Slurry coating

Weigh 23.62 g of 30 μm cut electrolytic copper foil, use a scraper to evenly coat the prepared graphite slurry on one side of the copper foil, the mass fraction of copper-plated graphite on a single copper foil is 5.54%, then place the copper foil coated with the slurry in a tubular furnace for calcination and reduction, and introduce high-purity hydrogen at a flow rate of 300 mL/min. The program is set as follows: increase the temperature from room temperature to 200 °C at 10 °C/min, keep warm for 2 h, and then cool to room temperature with the furnace;

(3) Spark plasma sintering

The reduced copper foil was placed in the graphite mold wrapped with carbon paper in the same direction. The graphite mold was pre-pressed and placed in the spark plasma sintering furnace chamber. It was sintered according to the set program under a vacuum environment. The temperature was measured by a thermocouple. The set program was as follows: the temperature was increased to 600 ℃ at a rate of 100 ℃/min and kept for 5 min; then it was increased to 920 ℃ at a rate of 100 ℃/min. During this process, the pressure was increased from 10 MPa to 50 MPa. After keeping for 5 min, it was quickly cooled to obtain the Cu-GR composite material.

Embodiment 2:

The Cu-Cr-GR composite material in this embodiment is prepared by tape casting, calcination reduction, lamination, spark plasma sintering and aging treatment, wherein the mass fraction of Cr is 0.25%, the volume fraction of copper-plated graphite is 20%, and the rest is electrolytic copper foil.

The preparation method of the Cu-Cr-GR composite material in this embodiment is as follows:

(1) Material pretreatment

HCl solution was used to ultrasonically clean 30 μm electrolytic copper foil and copper-plated graphite at room temperature for 30 min. After cleaning, the copper foil was cut into discs with a diameter of 25 mm and the copper-plated graphite was sieved through 500 μm. Polyvinyl butyral and anhydrous ethanol were added into a beaker in a mass ratio of 1:8 and magnetically stirred at 30 °C until clear and free of colloid. The mixture was taken out and allowed to stand until no bubbles were generated to prepare a binder. 0.06 g of high-purity chromium powder and 1.38 g of 500 μm copper-plated graphite were weighed and added into the prepared binder and magnetically stirred for 30 min until uniformly mixed to prepare a graphite slurry.

(2) Slurry coating

Weigh 23.56 g of 30 μm cut electrolytic copper foil, use a scraper to evenly coat the prepared graphite slurry on one side of the copper foil. The mass fraction of chromium on the single copper foil is 0.25%, and the mass fraction of copper-plated graphite is 5.54%. Then, the copper foil coated with the slurry is placed in a tubular furnace for calcination and reduction, and high-purity hydrogen is introduced at a flow rate of 300 mL/min. The program is set as follows: increase the temperature from room temperature to 200 °C at 10 °C/min, keep warm for 2 h, and then cool to room temperature with the furnace;

(3) Spark plasma sintering

The reduced copper foil was placed in the graphite mold wrapped with carbon paper in the same direction. The graphite mold was pre-pressed and placed in the spark plasma sintering furnace chamber. It was sintered according to the set program under a vacuum environment. The temperature was measured by a thermocouple. The set program was as follows: the temperature was increased to 600 ℃ at a rate of 100 ℃/min and kept for 5 min; then it was increased to 920 ℃ at a rate of 100 ℃/min. During this process, the pressure was increased from 10 MPa to 50 MPa. After keeping for 5 min, it was quickly cooled to obtain the Cu-Cr-GR composite material.

Embodiment 3:

The Cu-Cr-GR composite material in this embodiment is prepared by tape casting, calcination reduction, lamination, spark plasma sintering and aging treatment, wherein the mass fraction of Cr is 0.25%, the volume fraction of copper-plated graphite is 20%, and the rest is electrolytic copper foil.

The preparation method of the Cu-Cr-GR composite material in this embodiment is as follows:

(1) Material pretreatment

HCl solution was used to ultrasonically clean 30 μm electrolytic copper foil and copper-plated graphite at room temperature for 30 min. After cleaning, the copper foil was cut into discs with a diameter of 25 mm and the copper-plated graphite was sieved through 500 μm. Polyvinyl butyral and anhydrous ethanol were added into a beaker at a mass ratio of 1:8 and magnetically stirred at 30 °C until clear and free of colloid. The mixture was taken out and allowed to stand until no bubbles were generated to prepare a binder. 0.06 g of high-purity chromium powder and 1.38 g of 500 μm copper-plated graphite were weighed and added into the prepared binder and magnetically stirred for 30 min until uniformly mixed to prepare a graphite slurry.

(2) Slurry coating

Weigh 23.56 g of 30 μm cut electrolytic copper foil, use a scraper to evenly coat the prepared graphite slurry on one side of the copper foil. The mass fraction of chromium on the single copper foil is 0.25%, and the mass fraction of copper-plated graphite is 5.54%. Then, the copper foil coated with the slurry is placed in a tubular furnace for calcination and reduction, and high-purity hydrogen is introduced at a flow rate of 300 mL/min. The program is set as follows: increase the temperature from room temperature to 200 °C at 10 °C/min, keep warm for 2 h, and then cool to room temperature with the furnace;

(3) Spark plasma sintering

The reduced copper foil was placed in the same direction into the graphite mold wrapped with carbon paper, and the graphite mold was pre-pressed and compacted before being placed in the spark plasma sintering furnace. The sintering was performed according to the set program under vacuum environment, and the temperature was measured by thermocouple. The set program was as follows: the temperature was increased to 600 °C at a rate of 100 °C/min and kept for 5 min; then the temperature was increased to 920 °C at a rate of 100 °C/min, and the pressure was increased from 10 MPa to 50 MPa during the process. After keeping for 5 min, the temperature was rapidly cooled to obtain the Cu-Cr-GR composite material.

(4) Timeliness treatment

The Cu-Cr-GR composite material obtained by spark plasma sintering was removed from the surface carbon paper and placed in a tubular furnace for aging treatment. High-purity hydrogen was introduced at a flow rate of 300 mL/min. The program was set as follows: the temperature was increased from room temperature to 400 ℃ at 10 ℃/min, and then kept warm for 2 h and cooled to room temperature with the furnace. Finally, a high thermal conductivity Cu-Cr-GR composite material was obtained.

Embodiment 4:

The Cu-Cr-GR composite material in this embodiment is prepared by tape casting, calcination reduction, lamination, spark plasma sintering and aging treatment, wherein the mass fraction of Cr is 0.25%, the volume fraction of copper-plated graphite is 20%, and the rest is electrolytic copper foil.

The preparation method of the Cu-Cr-GR composite material in this embodiment is as follows:

(1) Material pretreatment

HCl solution was used to ultrasonically clean 30 μm electrolytic copper foil and copper-plated graphite at room temperature for 30 min. After cleaning, the copper foil was cut into discs with a diameter of 25 mm and the copper-plated graphite was sieved through 500 μm. Polyvinyl butyral and anhydrous ethanol were added into a beaker in a mass ratio of 1:8 and magnetically stirred at 30 °C until clear and free of colloid. The mixture was taken out and allowed to stand until no bubbles were generated to prepare a binder. 0.06 g of high-purity chromium powder and 1.38 g of 500 μm copper-plated graphite were weighed and added into the prepared binder and magnetically stirred for 30 min until uniformly mixed to prepare a graphite slurry.

(2) Slurry coating

Weigh 23.56 g of 30 μm cut electrolytic copper foil, use a scraper to evenly coat the prepared graphite slurry on one side of the copper foil. The mass fraction of chromium on the single copper foil is 0.25%, and the mass fraction of copper-plated graphite is 5.54%. Then, the copper foil coated with the slurry is placed in a tubular furnace for calcination and reduction, and high-purity hydrogen is introduced at a flow rate of 300 mL/min. The program is set as follows: increase the temperature from room temperature to 200 °C at 10 °C/min, keep warm for 2 h, and then cool to room temperature with the furnace;

(3) Spark plasma sintering

The reduced copper foil was placed in the same direction into the graphite mold wrapped with carbon paper, and the graphite mold was pre-pressed and compacted before being placed in the spark plasma sintering furnace. The sintering was performed according to the set program under vacuum environment, and the temperature was measured by thermocouple. The set program was as follows: the temperature was increased to 600 °C at a rate of 100 °C/min and kept for 5 min; then the temperature was increased to 920 °C at a rate of 100 °C/min, and the pressure was increased from 10 MPa to 50 MPa during the process. After keeping for 5 min, the temperature was rapidly cooled to obtain the Cu-Cr-GR composite material.

(4) Timeliness treatment

The Cu-Cr-GR composite material obtained by spark plasma sintering was removed from the surface carbon paper and placed in a tubular furnace for aging treatment. High-purity hydrogen was introduced at a flow rate of 300 mL/min. The program was set as follows: the temperature was increased from room temperature to 450 ℃ at 10 ℃/min, and then kept warm for 2 h and cooled to room temperature with the furnace. Finally, a high thermal conductivity Cu-Cr-GR composite material was obtained.

Embodiment 5:

The Cu-Cr-GR composite material in this embodiment is prepared by tape casting, calcination reduction, lamination, spark plasma sintering and aging treatment, wherein the mass fraction of Cr is 0.25%, the volume fraction of copper-plated graphite is 20%, and the rest is electrolytic copper foil.

The preparation method of the Cu-Cr-GR composite material in this embodiment is as follows:

(1) Material pretreatment

HCl solution was used to ultrasonically clean 30 μm electrolytic copper foil and copper-plated graphite at room temperature for 30 min. After cleaning, the copper foil was cut into discs with a diameter of 25 mm and the copper-plated graphite was sieved through 500 μm. Polyvinyl butyral and anhydrous ethanol were added into a beaker in a mass ratio of 1:8 and magnetically stirred at 30 °C until clear and free of colloid. The mixture was taken out and allowed to stand until no bubbles were generated to prepare a binder. 0.06 g of high-purity chromium powder and 1.38 g of 500 μm copper-plated graphite were weighed and added into the prepared binder and magnetically stirred for 30 min until uniformly mixed to prepare a graphite slurry.

(2) Slurry coating

Weigh 23.56 g of 30 μm cut electrolytic copper foil, use a scraper to evenly coat the prepared graphite slurry on one side of the copper foil. The mass fraction of chromium on the single copper foil is 0.25%, and the mass fraction of copper-plated graphite is 5.54%. Then, the copper foil coated with the slurry is placed in a tubular furnace for calcination and reduction, and high-purity hydrogen is introduced at a flow rate of 300 mL/min. The program is set as follows: increase the temperature from room temperature to 200 °C at 10 °C/min, keep warm for 2 h, and then cool to room temperature with the furnace;

(3) Spark plasma sintering

The reduced copper foil was placed in the same direction into the graphite mold wrapped with carbon paper, and the graphite mold was pre-pressed and compacted before being placed in the spark plasma sintering furnace. The sintering was performed according to the set program under vacuum environment, and the temperature was measured by thermocouple. The set program was as follows: the temperature was increased to 600 °C at a rate of 100 °C/min and kept for 5 min; then the temperature was increased to 920 °C at a rate of 100 °C/min, and the pressure was increased from 10 MPa to 50 MPa during the process. After keeping for 5 min, the temperature was rapidly cooled to obtain the Cu-Cr-GR composite material.

(4) Timeliness treatment

The Cu-Cr-GR composite material obtained by spark plasma sintering was removed from the surface carbon paper and placed in a tubular furnace for aging treatment. High-purity hydrogen was introduced at a flow rate of 300 mL/min. The program was set as follows: the temperature was increased from room temperature to 500 ℃ at a rate of 10 ℃/min, and then cooled to room temperature with the furnace after keeping the temperature for 2 h. Finally, a high thermal conductivity Cu-Cr-GR composite material was obtained.

Table 1 below is a table of thermal and mechanical properties of Cu-GR, Cu-Cr-GR, Cu-Cr-GR 400℃ aging treatment, Cu-Cr-GR 450℃ aging treatment and Cu-Cr-GR 500℃ aging treatment composite materials. Compared with the unaged Cu-GR composite material and the Cu-Cr-GR composite material, the thermal conductivity of the material decreases slightly after the addition of Cr, because the low thermal conductivity Cr atoms are dissolved in the copper matrix, resulting in a decrease in the overall thermal conductivity. After the aging treatment, the thermal conductivity of the material is significantly improved; after the introduction of Cr, the tensile strength of the composite material increases slightly, because after sintering, Cr forms a solid solution in the copper matrix, which plays a role in solid solution strengthening, resulting in an increase in tensile strength. After the aging treatment, there is no obvious trend in the tensile strength of the material, but it is higher than the composite material in the original state, which confirms that the tensile strength of the composite material is the result of the combined effect of solid solution strengthening and grain boundary strengthening.

Table 1 Performance table of sample blocks

As can be seen from Figure 1, the surface of the Cu-0.25%wtCr-20%volGR(Cu) composite material shows three obvious regions of matrix-interface-graphite. The interface layer is located between copper and graphite, which improves the interface properties of the two, proving that aging treatment can improve the interface properties by generating an interface layer.

As can be seen from Figures 2 and 3, CrC phase was detected in the composite material after aging treatment, while it was not detected in the untreated material, which proves that aging treatment can promote the diffusion of Cr atoms dissolved in the copper matrix to the grain boundaries and react with graphite to form carbides.

The invention improves the interface property of copper-graphite by adding transition element Cr and performing aging treatment. After sintering, Cr atoms dissolved in the copper matrix diffuse to the interface after aging treatment and react with graphite to generate chromium carbide, thereby reducing the interface gap between copper and graphite and effectively improving the thermal conductivity of the composite material. It is difficult to control the orientation of graphite in the copper matrix when preparing the copper-graphite composite material by the traditional powder metallurgy method, which limits the improvement of its thermal conductivity. By introducing the copper matrix in the form of copper foil and adopting the tape casting method plus the lamination method to directionally control the orientation of graphite, the thermal conductivity of the composite material is further improved, and finally a high thermal conductivity Cu-Cr-GR composite material is prepared.

The above embodiments only illustrate specific implementations of the present disclosure, but the implementations of the present disclosure are not limited by the above contents. Any changes, modifications, substitutions, combinations, and simplifications made without substantially departing from the main idea and principle of the inventive concept of the present disclosure shall be equivalent replacement methods and shall be included in the scope of protection determined by the claims.

Claims (10)

1. A method for preparing a high thermal conductivity Cu-Cr-GR composite material, characterized in that it comprises the following steps: (1) Material pretreatment The copper foil and the copper-plated graphite are respectively placed in an HCl solution for ultrasonic cleaning to remove surface impurities and oxides, the copper foil is cut into a certain size and shape, the copper-plated graphite is sieved with a sieve, and the copper foil and the sieved copper-plated graphite are cleaned with anhydrous ethanol until no obvious dirt appears on the surface, and then the required materials are placed in anhydrous ethanol for storage; (2) Preparation of binder, chromium and graphite slurry Add polyvinyl butyral and anhydrous ethanol in a certain proportion to a beaker, stir magnetically at 30°C until the mixture is clear and free of colloid, take out and let stand until no bubbles are generated, thereby preparing a binder, add a certain amount of high-purity chromium powder and the copper-plated graphite in step (1) to the prepared binder, stir magnetically for 30 minutes until the mixture is evenly mixed, thereby preparing a graphite slurry; (3) Slurry coating Using a scraper, the graphite slurry prepared in step (2) is evenly coated on one side of the copper foil in step (1), and the copper foil coated with the slurry is placed in a tube furnace for calcination and reduction; (4) Spark plasma sintering The copper foil coated with the slurry in step (3) is sequentially placed in the same direction into the graphite mold, the graphite mold is pre-pressed and compacted, and then placed into the spark plasma sintering furnace chamber, and sintered according to the set program under a vacuum environment to obtain a Cu-Cr-GR composite material; (5) Timeliness treatment After removing the carbon paper from the surface of the composite material obtained in step (4), the composite material is placed in a tubular furnace and subjected to aging treatment by passing high-purity hydrogen gas, thereby finally obtaining a high thermal conductivity Cu-Cr-GR composite material. 2. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: the copper foil in step (1) is an electrolytic copper foil, the size and shape of which is a round piece with a thickness of 30 μm and a diameter of 25 mm, and the specification of the required copper-plated graphite is 500 μm. 3. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: in the step (1), the ultrasonic cleaning is performed for 30 min, and the ultrasonic cleaner used is a JK-5200B ultrasonic cleaner with a power of 200 W and a frequency of 40 KHz. 4. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: in the step (2), the mass ratio of polyvinyl butyral to anhydrous ethanol is 1:8, the content of chromium powder in the step (2) is 0.25 wt%, and the content of copper-plated graphite is 20 vol%. 5. The method for preparing a high thermal conductivity Cu-Cr-GR composite material according to claim 1, characterized in that the magnetic stirrer used in step (2) is a DF-101S heat-collecting magnetic stirrer. 6. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: in the slurry coated on the single copper foil in the step (3), the content of chromium powder is 0.25 wt%, and the content of copper-plated graphite is 5.54 wt%. 7. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: the tubular furnace model in the step (3) is GSL-1200X, and the setting program is as follows: increase the temperature from room temperature to 200°C at 10°C/min, keep warm for 2 hours, and then cool to room temperature with the furnace, and the hydrogen flow rate introduced in step (3) is 300 mL/min. 8. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: the total mass of the copper foil placed in the graphite mold in the step (4) is 25 g, and the pre-pressing pressure is 10 MPa. 9. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: in the step (4), the spark plasma sintering system model is LaboxTM-300, and a thermocouple is used to measure the temperature. The setting program is as follows: increase the temperature to 600°C at a rate of 100°C/min and keep it warm for 5 min; then increase the temperature to 920°C at a rate of 100°C/min, during which the pressure is increased from 10 MPa to 50 MPa, keep it warm for 5 min, and then cool rapidly. 10. A method for preparing a high thermal conductivity Cu-Cr-GR composite material as claimed in claim 1, characterized in that: the tubular furnace model in step (5) is GSL-1200X, and the setting program is as follows: increase the temperature from room temperature to 400-500°C at 10°C/min, keep warm for 2 hours, and then cool to room temperature with the furnace, and the hydrogen flow rate in step (5) is 300 mL/min.