Graphene / CuCrZr composite wire with high thermal conductivity and low temperature rise as well as preparation method and application of graphene / CuCrZr composite wire

Abstract

The invention discloses a graphene / CuCrZr composite wire with high thermal conductivity and low temperature rise as well as a preparation method and application of the graphene / CuCrZr composite wire, and the graphene / CuCrZr composite wire comprises the following components in percentage by mass: 0.04 to 0.6 weight percent of Cr, 0.015 to 0.35 weight percent of Zr, 0.02 to 0.8 weight percent of graphene and the balance of Cu. Due to the existence of the Cu / carbide / graphene heterojunction, uniform diffusion of graphene is realized, a continuously distributed graphene network is formed, an efficient heat transfer channel is successfully constructed, the heat dissipation efficiency is improved, and the graphene / CuCrZr composite wire has relatively high heat-conducting property and low temperature rise.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of copper-based composite materials, and particularly relates to a graphene / CuCrZr composite wire with high thermal conductivity and low temperature rise and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of electronic devices towards high power density, miniaturization and integration, the heat generated during operation accumulates rapidly, leading to a significant increase in device temperature, which seriously restricts the system stability and service life. High-efficiency heat dissipation has become one of the core bottlenecks of the development of electronic packaging and interconnection technology.

[0003] At present, traditional pure copper is widely used as a heat dissipation material due to its high thermal conductivity (about 400 W / m·K). However, the thermal conductivity of pure copper has approached its theoretical limit, and there are problems such as high thermal expansion coefficient and mechanical property decay at high temperature, which makes it difficult to meet the heat dissipation requirements of new-generation high-power chips, lasers and power electronic devices.

[0004] In recent years, graphene is considered as an ideal reinforcing body for improving the thermal conductivity of copper matrix due to its ultra-high thermal conductivity (about 5300 W / m·K) and ultra-high intrinsic carrier mobility.

[0005] The patent document with the publication number CN113441716A discloses a method for preparing graphene-coated CuCrZr alloy by spark plasma sintering, which comprises the following steps: S1: first, prepare CuCrZr alloy powder by vacuum air atomization method; S2: pretreat the CuCrZr alloy powder prepared in step S1 by coating a network structure of graphene on the surface using the oxidation-reduction method; S3: use the graphene-coated CuCrZr alloy powder as raw material, place the raw material in a spark plasma sintering device, and then obtain the finished product by spark plasma sintering; S4: subject the finished product obtained in step S3 to solid solution treatment, cold rolling and aging treatment. The new copper alloy prepared by the preparation method improves the electrical conductivity, thermal conductivity, ductility and wear resistance of the material compared with traditional materials. However, the new copper alloy of the application only has one graphene coating layer and is not dispersed in the copper alloy, so the improvement of thermal conductivity is limited.

[0006] To disperse graphene in the copper alloy, there are still key challenges: poor uniformity of dispersion, because the density of graphene is much lower than that of copper melt, which easily floats and agglomerates in traditional smelting process, making it difficult to achieve uniform dispersion, not only weakening the continuity of the heat conduction path, but also possibly introducing defects as thermal resistance points.

[0007] The prior art attempts to improve the dispersibility by methods such as ball milling, electrodeposition or chemical plating, but ball milling easily destroys the structure of graphene, and wet process introduces impurities and is difficult to scale up. Although individual studies use carbides (such as TiC and Cr3C2) to modify the interface, they mostly rely on additional carbide particles, and the synergistic effect of the carbide particles with graphene is limited, and the problem of the reinforcement floating on the surface has not been effectively solved.

[0008] The patent document with publication number CN118703816A discloses a graphene reinforced copper alloy composite material and a preparation method thereof. The preparation method comprises: S1, adding a bisoleic acid phosphite solution and a boric acid ester solution into a container containing an aqueous solution and stirring uniformly, adding graphene powder into the container containing the mixed solution of the bisoleic acid phosphite solution, the boric acid ester solution and the aqueous solution, and stirring uniformly; S2, adding polytetrafluoroethylene micro powder into the container containing the mixed solution of the graphene powder, the bisoleic acid phosphite solution and the aqueous solution, heating the container and stirring the liquid in the container, and performing suction filtration and drying on the obtained composite solution to obtain modified graphene powder; S3, adding the modified graphene powder, copper powder, silver powder and nickel powder into a container containing an ethanol solution and stirring, adding the mixed ethanol solution into a ball mill for compounding to obtain copper composite powder; S4, performing suction filtration and drying on the copper composite powder obtained in step 3; and S5, performing hot-pressing sintering on the copper composite powder to obtain the graphene reinforced copper alloy composite material. Although the application realizes uniform combination of graphene and copper powder, the graphene needs to be modified by adding polytetrafluoroethylene to increase the strength of the graphene, and the application scenario is more inclined to prepare wear-resistant and high-strength copper alloys without emphasizing the improvement of the heat conduction performance.

[0009] Therefore, it is of urgent significance to develop a copper-based composite material preparation technology that can realize uniform dispersion of graphene and construct an efficient heat transfer channel to break through the heat dissipation bottleneck of high-power electronic devices. SUMMARY

[0010] In view of the deficiencies of the prior art, the first aspect of the present application provides a high-thermal-conductivity and low-temperature-rise graphene / CuCrZr composite wire, which has high thermal conductivity and low temperature rise under power-on conditions.

[0011] The high-thermal-conductivity and low-temperature-rise graphene / CuCrZr composite wire provided by the present application comprises the following components by mass percentage: Cr content of 0.04-0.6 wt.%, Zr content of 0.015-0.35 wt.%, graphene content of 0.02-0.8 wt.%, and the balance being Cu.

[0012] The application promotes Cr and Zr solute atoms to react with graphene by adding a small amount of Cr and Zr alloying elements in the copper matrix, in-situ generates Cu / carbide / graphene heterojunction, the presence of Cu / carbide / graphene heterojunction can uniformly disperse graphene during melting, reduces sintering loss caused by graphene floating as much as possible, and forms a continuous distribution of graphene network, successfully builds an efficient heat transfer channel, improves the heat dissipation efficiency, and further improves the thermal conductivity of the composite material and the temperature rise under the working condition of power application.

[0013] Preferably, in the graphene / CuCrZr composite wire organization, the graphene presents a three-dimensional network distribution.

[0014] Preferably, the thermal conductivity of the graphene / CuCrZr composite wire is 438-541 W•m -1 •K -1 , the current density is 18-20 A / mm 2 , and the temperature rise is reduced by 14.3-26.1% compared with the base copper material, which is a CuCrZr wire with the same composition.

[0015] In a second aspect, the application also provides a preparation method of a graphene / CuCrZr composite wire with high thermal conductivity and low temperature rise, comprising: (1) preparing CuCrZr alloy powder by high-pressure atomization powdering process; (2) mixing the CuCrZr alloy powder and graphene powder by acoustic resonance to obtain graphene / CuCrZr mixed powder; (3) vacuum hot-pressing sintering the graphene / CuCrZr mixed powder to obtain graphene / CuCrZr composite blank, in the graphene / CuCrZr composite blank, the mass percentage of each component is that the content of graphene is 0.5-2wt.%, the content of Cr is 0.8-1.2wt.%, the content of Zr is 0.3-0.7wt.%, and the balance is Cu; (4) vacuum melting and stirring the oxygen-free copper material and the graphene / CuCrZr composite blank, then performing downward continuous casting, continuous extrusion, continuous drawing and online non-contact annealing to obtain the graphene / CuCrZr composite wire; In step (4), the temperature of downward continuous casting is 1150-1200℃.

[0016] By controlling the content of graphene, Cr element and Zr element in the graphene / CuCrZr composite blank, the application promotes Cr and Zr solute atoms in the alloy to react with graphene, forms carbide, and forms a covalent bond with copper, in-situ generates more Cu / carbide / graphene heterojunction.

[0017] On the one hand, the carbon compound can serve as a bridge between copper and graphene, allowing the two to be closely connected; on the other hand, the density of the Cu / carbon compound / graphene heterojunction is significantly improved compared with graphene. Therefore, the presence of the Cu / carbon compound / graphene heterojunction can effectively inhibit the floating of graphene during the smelting process, and help the uniform dispersion of graphene in the copper melt. The uniformly distributed graphene can serve as a rapid heat transfer channel to improve the thermal conductivity of the graphene / CuCrZr composite wire. At the same time, the content of Cr and Zr elements is avoided to be too high, so that the residual Cr and Zr solute atoms cannot react with graphene to form Cu / carbon compound / graphene heterojunction, but are dissolved into the copper melt in the subsequent smelting process, causing lattice distortion and reducing the electrical conductivity and thermal conductivity of the graphene / CuCrZr composite wire. At the same time, the content of Cr and Zr elements is avoided to be too low, so that insufficient amount of Cu / carbon compound / graphene heterojunction cannot be generated in situ, and the unreacted graphene will continue to float on the surface of the melt, cannot be uniformly dispersed in the melt, causing a large loss of graphene, and the thermal conductivity will also decrease. In addition, the Cu / carbon compound / graphene heterojunction is also beneficial to load transfer, reduces the interfacial thermal resistance, and improves the heat dissipation capacity, thereby realizing low temperature rise and excellent processability of the graphene / CuCrZr composite wire.

[0018] Furthermore, the present application also controls the temperature of the downward continuous casting to be slightly higher than the melting point of copper, so that the copper melt maintains a certain viscosity, in order to avoid the flowability of the copper melt being too strong due to the temperature of the downward continuous casting being too high. Even if the Cu / carbon compound / graphene heterojunction with relatively high density is generated, it will also float on the surface of the copper melt due to the flowability of the copper melt, causing the graphene to be difficult to uniformly disperse in the copper melt, thereby reducing the thermal conductivity of the graphene / CuCrZr composite wire.

[0019] Preferably, in step (1), the specific steps are as follows: the raw materials, electrolytic copper (purity 99.99%) and Cu-10Cr and Cu-20Zr intermediate alloys, are weighed and dried according to the proportions. Then the electrolytic copper is melted at 1300-1400°C, and then the Cu-10Cr and Cu-20Zr intermediate alloys are added. The alloy melt is superheated to 1400-1500°C, and then poured into an atomization device, and high-purity argon gas with a pressure greater than 3 MPa is introduced for atomization to obtain CuCrZr alloy powder, and then a sieve is used to screen out CuCrZr alloy powder with a particle size less than 75 μm.

[0020] Further preferably, in step (1), after the electrolytic copper is completely melted, the melt needs to be covered with dried charcoal; and the atomization device is filled with high-purity argon gas in advance, and the atomization device is controlled to be slightly positive during atomization, so as to prevent the surface of the raw material electrolytic copper and the CuCrZr alloy from being oxidized and introducing unnecessary impurities, thereby causing the quality of the CuCrZr alloy powder to decrease.

[0021] Preferably, in step (2), the graphene powder has a diameter < 20 μm, a number of layers < 10, and a specific surface area of ​​50~150 m². 2 / g.

[0022] Preferably, in step (2), the conditions for the acoustic resonance mixing are: an acceleration of 50~100 g (1g≈9.8 m / s²). 2 The vibration frequency is 20~80 Hz, the vibration intensity is 20~50%, and the mixing time is 1~10 min. This invention uses acoustic resonance mixing technology to promote the movement of CuCrZr alloy powder and graphene powder by using a low-frequency, high-intensity sound field, thereby achieving uniform mixing of graphene.

[0023] Preferably, in step (3), the vacuum hot pressing sintering temperature is 950~1050℃, the time is 3~5 h, the pressure is 20~50 MPa, and the vacuum degree is 10. -3 ~10 -1 Pa.

[0024] This invention controls the parameters of vacuum hot pressing sintering to allow Cr and Zr solute atoms to diffuse and react as much as possible at the defects on the graphene surface, generating more Cu / carbide / graphene heterojunctions in situ, further improving the floating phenomenon of graphene, helping to uniformly disperse graphene in copper melt, and improving the thermal conductivity of graphene / CuCrZr composite wire.

[0025] Preferably, in step (3), the graphite mold and the mixed powder in the vacuum hot pressing sintering are separated by a copper sheet with a thickness of 0.02~0.08 mm to prevent the Cr and Zr elements in the mixed powder and the C elements in the graphite mold from reacting and sticking together, making it impossible to demold.

[0026] Preferably, in step (4), the mass ratio of the graphene / CuCrZr composite billet to the oxygen-free copper material is 1:1~19.

[0027] This invention controls the composition and graphene addition amount of the graphene / CuCrZr composite wire by controlling the ratio of graphene / CuCrZr composite blank to oxygen-free copper material.

[0028] Preferably, in step (4), the vacuum degree of the vacuum melting is 10. -3 ~10 -1 Pa, with an Ar protective atmosphere, and a melting temperature of 1300~1400℃.

[0029] Preferably, in step (4), after the graphene / CuCrZr composite blank is completely melted, electromagnetic stirring is started, the frequency of the electromagnetic stirring is 40-100 Hz, and the current is 250-500 A. In the vacuum melting process, electromagnetic stirring is used to uniformly mix the graphene / CuCrZr composite blank and the oxygen-free copper material after they are melted, so that the graphene is uniformly dispersed in the copper matrix.

[0030] Preferably, in step (4), the speed of the downward continuous casting is 5-15 mm / s, the ratio of the running time to the stopping time of the downward continuous casting is 1:1-2:1, and the specification of the downward drawing rod of the downward continuous casting is φ10-12.5 mm.

[0031] Preferably, in step (4), the temperature of the continuous extrusion is 450-550℃, the extrusion speed is 20-40 m / min, the extrusion pressure is 40-60 MPa, the rotation speed of the extrusion wheel is 8-12 rpm, and the specification of the material after the continuous extrusion is φ6-8 mm.

[0032] Preferably, in step (4), the drawing speed in the continuous drawing step is 450-550 m / min, and the specification of the material after the continuous drawing is φ1-2 mm.

[0033] Preferably, in step (4), in the online non-contact annealing step, the annealing temperature is 500-580℃, the annealing speed is 0.4-0.6 m / min, and the annealing atmosphere is high-purity Ar. Through the online non-contact annealing, the Cr and Zr elements in the copper matrix that have not completely reacted with the graphene are fully aged and precipitated at the copper / graphene interface, and the copper matrix is recrystallized, so that the electrical conductivity and thermal conductivity of the graphene / CuCrZr composite wire are improved.

[0034] In a third aspect, the application also provides the application of the graphene / CuCrZr composite wire with high thermal conductivity and low temperature rise in density electronic packaging and interconnection.

[0035] The graphene / CuCrZr composite wire with high thermal conductivity and low temperature rise provided by the application can be applied to, for example, the internal thermal interface material / thermal diffusion layer of a chip package, as a fine wire for the heat conduction path between a chip and a heat sink or between different layers inside the chip, significantly reduces the hotspot temperature, and improves the performance and reliability of the chip.

[0036] Compared with the prior art, the application has the following beneficial effects: The application promotes Cr and Zr elements to react with graphene by adding trace amounts of Cr and Zr elements in the copper matrix, in-situ generates Cu / carbide / graphene heterojunction, the structure can effectively inhibit the floating phenomenon of graphene in the melting process, thereby realizing the uniform dispersion of graphene in the copper melt, forming a continuous three-dimensional heat conduction network, and improving the heat conduction performance and low temperature rise of the graphene / CuCrZr composite wire.

[0037] The preparation method provided by the application also promotes the reaction of Cr and Zr solute atoms in the alloy with graphene by controlling the content of graphene, Cr elements and Zr elements in the graphene / CuCrZr composite initial blank, forms carbide, in-situ generates more Cu / carbide / graphene heterojunction, the density of the Cu / carbide / graphene heterojunction is not only improved compared with graphene, and the carbide closely connects copper and graphene, and inhibits the floating of graphene in the smelting process. In addition, the application also controls the temperature of the down-drawing continuous casting, so that the copper melt maintains a certain viscosity, and avoids the Cu / carbide / graphene heterojunction generated from the copper melt due to the good fluidity of the copper melt. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 a is the SEM image and EDS-mapping element map of the CuCrZr alloy powder screened in the embodiments 1-3 and the comparative examples 2-6 of the application, Figure 1 b and c are the SEM image and Raman spectrum of the graphene powder in the embodiments 1-3 of the application, respectively; Figure 2 is the SEM image and EDS-mapping element map of the graphene / CuCrZr composite wire in the embodiment 3 of the application. DETAILED DESCRIPTION

[0039] The technical solutions of the application will be described clearly and completely in combination with the embodiments below. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application. The application provides three embodiments and six comparative examples. It can be understood that unavoidable impurities will be obtained in some embodiments, and the mass percentage content of the unavoidable impurities is <0.005%.

[0040] Embodiment 1 The graphene / CuCrZr composite wire with a graphene addition amount of 0.05 wt.% is prepared, which specifically includes the following steps: (1) Using 8.75 kg of electrolytic copper (99.99% purity) and 1 kg of Cu-10Cr and 0.25 kg of Cu-20Zr master alloys as raw materials, Cu-1Cr-0.5Zr alloy powder was prepared by high-pressure atomization powder preparation process. First, the raw materials were weighed and dried in a forced-air drying oven. Then, the electrolytic copper was melted in an induction furnace at a melting temperature of about 1350℃. After the electrolytic copper was completely melted, Cu-10Cr and Cu-20Zr master alloys were added. The melt was covered with dried charcoal to prevent oxidation. After uniform melting, CuCrZr alloy melt of the target composition was obtained. The alloy melt was superheated to 1450℃ and poured into an atomization device. High-purity argon gas with a pressure greater than 3 MPa was used to atomize the CuCrZr alloy melt into CuCrZr alloy powder through the atomizer. Powder with a particle size of less than 75 μm was sieved from the prepared CuCrZr alloy powder for use.

[0041] (2) Using an acoustic resonance mixing process, CuCrZr alloy powder (10 kg) with a particle size less than 75 μm and a diameter < 15 μm, with fewer than 6 layers and a specific surface area of ​​100 m² are mixed. 2 50g of graphene powder was mixed evenly. The acceleration of acoustic resonance mixing was 60g (1g≈9.8 m / s²). 2 The vibration frequency was 65 Hz, the vibration intensity was 38%, and the mixing time was 5 min.

[0042] (3) The graphene / CuCrZr mixed powder was loaded into the graphite mold of the hot press and sintered under vacuum at 1020℃ for 4 h, with a pressure of 35 MPa and a vacuum degree of 10. -3 Pa. A 0.05 mm thick copper sheet separates the graphite mold from the mixed powder to prevent the Cr and Zr elements in the mixed powder from reacting with the C element in the graphite mold, causing adhesion and preventing demolding. After furnace cooling, milling is performed to obtain a graphene / CuCrZr composite preform. In the graphene / CuCrZr composite preform, the mass percentage of each component is as follows: graphene content is 0.5 wt.%, Cr content is 1 wt.%, Zr content is 0.5 wt.%, and the balance is Cu.

[0043] (4) Place the oxygen-free copper material and the graphene / CuCrZr composite billet (mass ratio 9:1) into the graphite crucible of the vacuum continuous casting furnace, and then evacuate to 100°C. -3Pa, and then high-purity Ar was introduced as a protective gas. Then, the heating and melting of the oxygen-free copper material and the graphene / CuCrZr composite initial blank were started, with a melting temperature of 1400°C. After complete melting, electromagnetic stirring was started, with a frequency of 80 Hz and a current of 300 A. Then, the temperature was lowered for heat preservation. After the liquid surface was stable, downward continuous casting was performed, with a continuous casting temperature of 1150°C, a continuous casting speed of 10 mm / s, a ratio of running time to stopping time of 2:1, and a specification of the downward drawing rod of φ12.5 mm. Subsequently, the graphene / CuCrZr downward drawing rod was continuously extruded to φ8, with an extrusion deformation temperature of 500°C, an extrusion speed of 25 m / min, an extrusion pressure of 50 MPa, and an extrusion wheel rotating speed of 9 rpm. Then, the φ8 continuous extruded graphene / CuCrZr rod was continuously drawn to φ1.7 mm, with a drawing speed of 500 m / min. Finally, the graphene / CuCrZr composite wire was subjected to online non-contact annealing, with an annealing temperature of 550°C, an annealing speed of 0.5 m / min, and an annealing atmosphere of high-purity Ar.

[0044] Example 2 The graphene / CuCrZr composite wire with a graphene addition amount of 0.1 wt.% was prepared, specifically including the following steps: (1) Cu-1Cr-0.5Zr alloy powder was prepared by high-pressure atomization powdering process, with 8.75 kg of electrolytic copper (purity 99.99%) and 1 kg of Cu-10Cr and 0.25 kg of Cu-20Zr intermediate alloy as raw materials. First, the raw materials were weighed and dried in a blast drying oven. Then, the electrolytic copper was melted in an induction furnace, with a melting temperature of about 1350°C. After the electrolytic copper was completely melted, the Cu-10Cr and Cu-20Zr intermediate alloys were added, and the melt was covered with dried charcoal to prevent oxidation. After uniform smelting, a CuCrZr alloy melt with the target composition was obtained. The alloy melt was superheated to 1450°C, and the CuCrZr alloy melt was atomized into CuCrZr alloy powder by passing high-purity argon gas with a pressure greater than 3 MPa through the atomizer. The powder with a particle size less than 75 μm was sieved from the prepared CuCrZr alloy powder for use.

[0045] (2) The CuCrZr alloy powder with a particle size less than 75 μm (10 kg) and the graphene powder with a diameter of <15 μm, a layer number of <6 layers, and a specific surface area of 100 m 2 / g (100 g) were uniformly mixed by acoustic resonance mixing process. The acceleration of acoustic resonance mixing was 60 g (1 g≈9.8 m / s 2 ), the vibration frequency was 65 Hz, the vibration intensity was 38%, and the mixing time was 5 min.

[0046] (3) The graphene / CuCrZr mixed powder is loaded into a graphite mold of a hot press, vacuum hot-pressed and sintered at 1020°C for 4 h at a pressure of 35 MPa and a vacuum degree of 10 -3 Pa. A copper sheet with a thickness of 0.05 mm is used to separate the graphite mold and the mixed powder to prevent the reaction between the Cr and Zr elements in the mixed powder and the C element in the graphite mold, and to prevent adhesion and demolding. After cooling in the furnace, the graphene / CuCrZr composite blank is milled, and in the graphene / CuCrZr composite blank, the mass percentage of each component is as follows: the content of graphene is 1 wt.%, the content of Cr is 1 wt.%, the content of Zr is 0.5 wt.%, and the balance is Cu.

[0047] (4) The oxygen-free copper material and the graphene / CuCrZr composite blank (mass ratio of 9:1) are placed in a graphite crucible of a downward continuous casting furnace under vacuum, and then vacuum is drawn to 10 -3 Pa, and then high-purity Ar is introduced as a protective gas. Then, the oxygen-free copper material and the graphene / CuCrZr composite blank are heated and melted, the melting temperature is 1400°C, and after complete melting, electromagnetic stirring is started, the frequency is 80 Hz, and the current is 300 A. Then, the temperature is lowered for heat preservation, and after the liquid surface is stable, downward continuous casting is performed, the continuous casting temperature is 1150°C, the continuous casting speed is 10 mm / s, the ratio of the running time to the stopping time of the continuous casting is 2:1, and the specification of the downward drawing rod is φ12.5 mm. Then, the graphene / CuCrZr downward drawing rod is continuously extruded to φ8, the extrusion deformation temperature is 500°C, the extrusion speed is 25 m / min, the extrusion pressure is 50 MPa, and the extrusion wheel rotating speed is 9 rpm. Then, the φ8 continuously extruded graphene / CuCrZr rod is continuously drawn to φ1.7 mm at a drawing speed of 500 m / min. Finally, the graphene / CuCrZr composite wire is subjected to online non-contact annealing, the annealing temperature is 550°C, the annealing speed is 0.5 m / min, and the annealing atmosphere is high-purity Ar.

[0048] Example 3 A graphene / CuCrZr composite wire with a graphene addition amount of 1 wt.% is prepared, specifically including the following steps: (1) Using 8.75 kg of electrolytic copper (99.99% purity) and 1 kg of Cu-10Cr and 0.25 kg of Cu-20Zr master alloys as raw materials, Cu-1Cr-0.5Zr alloy powder was prepared by high-pressure atomization powder preparation process. First, the raw materials were weighed and dried in a forced-air drying oven. Then, the electrolytic copper was melted in an induction furnace at a melting temperature of about 1350℃. After the electrolytic copper was completely melted, Cu-10Cr and Cu-20Zr master alloys were added. The melt was covered with dried charcoal to prevent oxidation. After uniform melting, CuCrZr alloy melt of the target composition was obtained. The alloy melt was superheated to 1450℃ and poured into an atomization device. High-purity argon gas with a pressure greater than 3 MPa was used to atomize the CuCrZr alloy melt into CuCrZr alloy powder through the atomizer. Powder with a particle size of less than 75 μm was sieved from the prepared CuCrZr alloy powder for use.

[0049] (2) Using an acoustic resonance mixing process, CuCrZr alloy powder (10 kg) with a particle size less than 75 μm and a diameter < 15 μm, with fewer than 6 layers and a specific surface area of ​​100 m² are mixed. 2 200g of graphene powder was mixed uniformly. The acceleration of acoustic resonance mixing was 60g (1g≈9.8 m / s²). 2 The vibration frequency was 65 Hz, the vibration intensity was 38%, and the mixing time was 5 min.

[0050] (3) The graphene / CuCrZr mixed powder was loaded into the graphite mold of the hot press and sintered under vacuum at 1020℃ for 4 h, with a pressure of 35 MPa and a vacuum degree of 10. -3 Pa. A 0.05 mm thick copper sheet separates the graphite mold from the mixed powder to prevent the Cr and Zr elements in the mixed powder from reacting with the C element in the graphite mold, causing adhesion and preventing demolding. After furnace cooling, milling is performed to obtain a graphene / CuCrZr composite preform. In the graphene / CuCrZr composite preform, the mass percentage of each component is as follows: graphene content is 2 wt.%, Cr content is 1 wt.%, Zr content is 0.5 wt.%, and the balance is Cu.

[0051] (4) Place the oxygen-free copper material and the graphene / CuCrZr composite billet (mass ratio 1:1) into the graphite crucible of the vacuum casting furnace, and then evacuate to 100°C. -3Pa, and then high-purity Ar was introduced as a protective gas. Then, the oxygen-free copper material and the graphene / CuCrZr composite blank were melted at a temperature of 1400°C, and electromagnetic stirring was started after complete melting at a frequency of 80 Hz and a current of 300 A. Then, the temperature was lowered for heat preservation, and after the liquid surface was stable, downward continuous casting was performed at a temperature of 1150°C and a speed of 10 mm / s, with a ratio of running time to stopping time of 2:1, and a specification of the downward drawing rod of φ12.5 mm. Subsequently, the graphene / CuCrZr downward drawing rod was continuously extruded to φ8 at an extrusion deformation temperature of 500°C, an extrusion speed of 25 m / min, an extrusion pressure of 50 MPa, and an extrusion wheel rotating speed of 9 rpm. Then, the φ8 continuously extruded graphene / CuCrZr rod was continuously drawn to φ1.7 mm at a drawing speed of 500 m / min. Finally, the graphene / CuCrZr composite wire was subjected to online non-contact annealing at a temperature of 550°C, an annealing speed of 0.5 m / min, and an annealing atmosphere of high-purity Ar.

[0052] Comparative Example 1 A graphene / Cu composite wire with a graphene addition amount of 0.05 wt.% was prepared, specifically including the following steps: (1) Cu powder was prepared by high-pressure atomization powdering process using 10 kg of electrolytic copper (purity 99.99%) as raw material. First, the raw material was weighed and dried in a blast drying oven, and then the electrolytic copper was melted in an induction furnace at a melting temperature of about 1150°C. After complete melting of the electrolytic copper, the melt was covered with dried charcoal to prevent oxidation, and then the melt was superheated to 1250°C and poured into an atomization device, and the Cu melt was atomized into Cu powder by high-purity argon gas with a pressure greater than 3 MPa through the atomizer. The powder with a particle size less than 75 μm was sieved from the prepared Cu powder for use.

[0053] (2) The Cu powder (10 kg) with a particle size less than 75 μm and the graphene powder (50 g) with a diameter <15 μm, a number of layers <6, and a specific surface area of 100 m 2 / g were uniformly mixed by acoustic resonance mixing process. The acceleration of acoustic resonance mixing was 60 g (1 g ≈ 9.8 m / s 2 ), the vibration frequency was 65 Hz, the vibration intensity was 38%, and the mixing time was 5 min.

[0054] (3) The graphene / Cu mixed powder was loaded into a graphite mold of a hot press, and vacuum hot-pressing sintering was performed at 1000°C for 4 h at a pressure of 35 MPa and a vacuum degree of 10 -3Pa. The graphite mold and the mixed powder were separated by a copper sheet with a thickness of 0.05 mm. After furnace cooling, the graphene / Cu composite initial blank was obtained by milling, in which the content of graphene was 0.5 wt.%.

[0055] (4) The oxygen-free copper material and the graphene / Cu composite initial blank (mass ratio of 9:1) were put into the graphite crucible of the downward continuous casting furnace under vacuum, and then vacuum was extracted to 10 -3 Pa, and then high-purity Ar was introduced as a protective gas. Then, the oxygen-free copper material and the graphene / Cu composite initial blank were heated and melted, the melting temperature was 1200℃, and after complete melting, electromagnetic stirring was started, the frequency was 80 Hz, and the current was 300 A. Then, the temperature was lowered for heat preservation, and after the liquid surface was stable, downward continuous casting was carried out, the continuous casting temperature was 1120℃, the continuous casting speed was 10 mm / s, the ratio of running time to stopping time of continuous casting was 2:1, and the specification of the downward drawing rod was φ12.5 mm. Then, the graphene / Cu downward drawing rod was continuously extruded to φ8, the extrusion deformation temperature was 500℃, the extrusion speed was 25 m / min, the extrusion pressure was 50 MPa, and the extrusion wheel rotating speed was 9 rpm. Then, the φ8 continuous extruded graphene / Cu rod was continuously drawn to φ1.7 mm, the drawing speed was 500 m / min. Finally, the graphene / Cu composite wire was subjected to online non-contact annealing, the annealing temperature was 550℃, the annealing speed was 0.5 m / min, and the annealing atmosphere was high-purity Ar.

[0056] Comparative Example 2 The difference from Example 1 is that the continuous casting temperature of Comparative Example 2 is 1250℃.

[0057] Comparative Example 3 The Cu-0.1Cr-0.05Zr alloy wire with a graphene addition amount of 0 wt.% was prepared, specifically including the following steps: (1) Cu-1Cr-0.5Zr alloy powder was prepared by high-pressure atomization process using 8.75 kg electrolytic copper (purity 99.99%) and 1 kg Cu-10Cr, 0.25 kg Cu-20Zr master alloy as raw materials. First, the raw materials were weighed and dried in a blast drying oven. Then, the electrolytic copper was melted in an induction furnace, and the melting temperature was about 1350°C. After the electrolytic copper was completely melted, Cu-10Cr and Cu-20Zr master alloys were added, and the melt was covered with dried charcoal to prevent oxidation. After uniform melting, the CuCrZr alloy melt with the target composition was obtained. The alloy melt was superheated to 1450°C and poured into the atomization device. The CuCrZr alloy melt was atomized into CuCrZr alloy powder by high-purity argon gas with a pressure greater than 3 MPa through the atomizer. The powder with a particle size less than 75 μm was sieved from the prepared CuCrZr alloy powder for use.

[0058] (2) The CuCrZr powder was loaded into a graphite mold of a hot press, vacuum hot-pressed and sintered at 1020°C for 4 h, with a pressure of 35 MPa and a vacuum degree of 10 -3 Pa. A copper sheet with a thickness of 0.05 mm was used to separate the graphite mold and the powder to prevent the reaction between Cr, Zr elements in the powder and C element in the graphite mold, resulting in adhesion and difficulty in demolding. After cooling in the furnace, the CuCrZr preform was milled to obtain the CuCrZr preform with a Cr content of 1 wt.% and a Zr content of 0.5 wt.%.

[0059] (3) Oxygen-free copper material and CuCrZr preform (mass ratio 9:1) were placed in a graphite crucible of a downward continuous casting furnace under vacuum, followed by vacuum pumping to 10 -3 Pa, and then high-purity Ar was introduced as a protective gas. Then, the oxygen-free copper material and the CuCrZr preform were melted by turning on the heating, and the melting temperature was 1400°C. After complete melting, electromagnetic stirring was started with a frequency of 80 Hz and a current of 300 A. Then, the temperature was lowered for heat preservation, and after the liquid surface was stable, downward continuous casting was performed at a continuous casting temperature of 1150°C and a continuous casting speed of 10 mm / s. The ratio of running time to stopping time of continuous casting was 2:1, and the specification of the downward drawing rod was φ12.5 mm. Then, the CuCrZr downward drawing rod was continuously extruded to φ8 with an extrusion deformation temperature of 500°C, an extrusion speed of 25 m / min, an extrusion pressure of 50 MPa, and an extrusion wheel speed of 9 rpm. Subsequently, the φ8 continuously extruded CuCrZr rod was continuously drawn to φ1.7 mm at a drawing speed of 500 m / min. Finally, the CuCrZr wire was subjected to online non-contact annealing at an annealing temperature of 550°C, an annealing speed of 0.5 m / min, and an annealing atmosphere of high-purity Ar.

[0060] Comparative Example 4 A Cu-0.5Cr-0.25Zr alloy wire with 0 wt.% graphene additive was prepared, specifically including the following steps: (1) Cu-1Cr-0.5Zr alloy powder was prepared by high-pressure atomization powdering process using 8.75 kg electrolytic copper (purity 99.99%) and 1 kg Cu-10Cr, 0.25 kg Cu-20Zr intermediate alloy as raw materials. First, the raw materials were weighed and dried in a blast drying oven, then the electrolytic copper was melted in an induction furnace, and the melting temperature was about 1350°C. After the electrolytic copper was completely melted, Cu-10Cr and Cu-20Zr intermediate alloy were added, and the melt was covered with dried charcoal to prevent oxidation. After uniform smelting, the CuCrZr alloy melt with the target composition was obtained. The alloy melt was superheated to 1450°C and poured into the atomization device. The CuCrZr alloy melt was atomized into CuCrZr alloy powder by a high-purity argon gas with a pressure greater than 3 MPa through the atomizer. The powder with a particle size less than 75 μm was sieved from the prepared CuCrZr alloy powder for use.

[0061] (2) The CuCrZr powder was loaded into the graphite mold of the hot press, vacuum hot-pressed and sintered at 1020°C for 4 h, with a pressure of 35 MPa and a vacuum degree of 10 -3 Pa. A copper sheet with a thickness of 0.05 mm was used to separate the graphite mold and the powder to prevent the reaction between the Cr and Zr elements in the powder and the C element in the graphite mold, resulting in adhesion and inability to demold. After cooling in the furnace, the CuCrZr initial blank was milled to obtain a CuCrZr initial blank with a Cr content of 1 wt.% and a Zr content of 0.5 wt.% for use.

[0062] (3) The oxygen-free copper material and the CuCrZr initial blank (mass ratio 1:1) were placed in the graphite crucible of the vacuum continuous casting furnace, and then the vacuum was drawn to 10 -3Pa, and then high-purity Ar was introduced as a protective gas. Then, the oxygen-free copper material and the CuCrZr primary blank were heated and melted, with a melting temperature of 1400°C. After complete melting, electromagnetic stirring was started, with a frequency of 80 Hz and a current of 300 A. Then, the temperature was lowered for heat preservation. After the liquid surface was stable, downward continuous casting was performed, with a continuous casting temperature of 1150°C, a continuous casting speed of 10 mm / s, a ratio of running time to stopping time of 2:1, and a specification of the downward drawing rod of φ12.5 mm. Subsequently, the CuCrZr downward drawing rod was continuously extruded to φ8, with an extrusion deformation temperature of 500°C, an extrusion speed of 25 m / min, an extrusion pressure of 50 MPa, and an extrusion wheel rotating speed of 9 rpm. Then, the φ8 continuous extrusion state CuCrZr rod was continuously drawn to φ1.7 mm, with a drawing speed of 500 m / min. Finally, the CuCrZr wire was subjected to online non-contact annealing, with an annealing temperature of 550°C, an annealing speed of 0.5 m / min, and an annealing atmosphere of high-purity Ar.

[0063] Comparative Example 5 The only difference between Example 1 and the present comparative example 5 is that the graphene / CuCrZr composite primary blank prepared in step (3) of the present comparative example 5 has a Cr content of 1.6 wt.%, a Zr content of 0.8 wt.%, and a graphene content of 0.1 wt.% by mass percentage. The mass ratio of the oxygen-free copper material and the graphene / CuCrZr composite primary blank in step (4) is 1:1.

[0064] Comparative Example 6 The only difference between Example 1 and the present comparative example 6 is that the graphene / CuCrZr composite primary blank prepared in step (3) of the present comparative example 6 has a Cr content of 0.04 wt.%, a Zr content of 0.02 wt.%, and a graphene content of 0.1 wt.% by mass percentage. The mass ratio of the oxygen-free copper material and the graphene / CuCrZr composite primary blank in step (4) is 1:1.

[0065] Performance Test Figure 1 a are SEM images and EDS-mapping element images of the CuCrZr alloy powder screened in Examples 1-3 and Comparative Examples 2-6 of the present application, from which it can be seen that the prepared CuCrZr alloy powder is smooth and spherical in shape, and the Cu, Cr, and Zr elements are uniformly distributed in the alloy powder. The measured chemical composition is Cu-1Cr-0.5Zr (wt.%). Figure 1 a can be seen that the graphene is of a micrometer-level lamellar structure, with a smooth surface. Its Raman spectrum (Figure 2b) shows that the graphene has a D band at 1350 cm-1, a G band at 1580 cm-1, and a 2D band at 2700 cm-1, which are characteristic peaks of graphene.

[0066] Figure 1 b are SEM images of the graphene powder in Examples 1-3 of the present application, from which it can be seen that the graphene is of a micrometer-level lamellar structure, with a smooth surface. Its Raman spectrum (Figure 2b) shows that the graphene has a D band at 1350 cm-1, a G band at 1580 cm-1, and a 2D band at 2700 cm-1, which are characteristic peaks of graphene. Figure 1 b can be seen that the graphene is of a micrometer-level lamellar structure, with a smooth surface. Its Raman spectrum (Figure 2b) shows that the graphene has a D band at 1350 cm-1, a G band at 1580 cm-1, and a 2D band at 2700 cm-1, which are characteristic peaks of graphene. Figure 1c) three characteristic peaks of graphene (D peak, G peak and 2D peak) appeared at about 1350 cm -1 , 1580 cm -1 and 2700 cm -1 .

[0067] Figure 2 SEM images and EDS-mapping element images of the graphene / CuCrZr composite wire prepared in Example 3 of the present application. It can be seen that the graphene is uniformly distributed, and the surface is enriched with Cr and Zr elements at the same time, in which the enrichment of Cr element is more obvious. This indicates that both Cr and Zr atoms diffuse to the graphene and react during the high-temperature sintering process, in which the reaction of Cr is more obvious. Figure 2

[0068] Table 1 shows the chemical composition, graphene content, thermal conductivity and temperature rise performance data of the composite wires in Examples 1-3 and Comparative Examples 1-6 of the present application. The C content in the composite wire is tested using a carbon-sulfur instrument to characterize the actual content of graphene therein, the principle of which is mainly to burn the sample at high temperature, and calculate the C content in the sample by detecting the amount of CO2 generated.

[0069] Since copper and graphene are not solid-soluble and do not react at high temperatures, the interface affinity of graphene and copper is poor, so the present application adds Cr and Zr alloying elements to react with graphene to form carbides, form a covalent bond with copper, and generate a Cu / carbide / graphene heterojunction, which modifies the Cu / graphene interface and is conducive to the successful addition and dispersion of graphene in copper.

[0070] In Comparative Example 1, no Cr and Zr elements are added, and the interface between copper and graphene is not improved, resulting in poor interface affinity and low content of graphene successfully introduced into copper. The continuous casting temperature in Comparative Example 2 is relatively high, resulting in excessive fluidity of the copper melt. Even if the Cu / carbide / graphene heterojunction with relatively high density is generated, it will float to the surface of the copper melt due to the fluidity of the copper melt, resulting in a large loss of graphene.

[0071] Compared with Comparative Examples 3-6, the present application controls the content of graphene, Cr element and Zr element in the graphene / CuCrZr composite blank, in-situ generates more Cu / carbide / graphene heterojunctions, and the density of the Cu / carbide / graphene heterojunction is not only improved compared with graphene, but also the carbide tightly connects copper and graphene, inhibits the floating of graphene during the smelting process, and helps the uniform dispersion of graphene in copper to form a connected thermal conduction network.

[0072] ​Moreover, the graphene content of the prepared graphene / CuCrZr composite wire is close to the raw material content of the added graphene, which is due to the existence of Cu / carbide / graphene heterojunction, effectively reducing the loss of graphene in the smelting process and improving the utilization rate of graphene. In addition, the existence of Cu / carbide / graphene heterojunction is also conducive to reducing the interface thermal resistance, thereby realizing the improvement of the thermal conductivity of graphene / CuCrZr composite wire and reducing the temperature rise under the working condition of power application.

[0073] Table 1 Composition, graphene content, thermal conductivity and temperature rise performance of composite wire

Claims

1. A high thermal conductive low temperature rise graphene / CuCrZr composite wire, characterized in that, The graphene / CuCrZr composite wire includes the following components in the following mass percentages: Cr content of 0.04-0.6 wt.%, Zr content of 0.015-0.35 wt.%, graphene content of 0.02-0.8 wt.%, and the balance of Cu.

2. The high thermal conductive low temperature rise graphene / CuCrZr composite wire of claim 1, wherein, In the graphene / CuCrZr composite wire structure, the graphene is in a three-dimensional network distribution.

3. The high thermal conductive low temperature rise graphene / CuCrZr composite wire of claim 1, wherein, The thermal conductivity of the graphene / CuCrZr composite wire is 438-541 W•m -1 •K -1 The temperature rise under a current density of 18-20 A / mm 2 is reduced by 14.3-26.1% compared with the base copper material.

4. A method of producing the high-thermal-conductivity low-temperature-rise graphene / CuCrZr composite wire according to any one of claims 1 to 3, characterized by, The preparation method includes: (1) preparing CuCrZr alloy powder by high-pressure atomization powdering process; (2) mixing the CuCrZr alloy powder and graphene powder by acoustic resonance to obtain graphene / CuCrZr mixed powder; (3) vacuum hot-pressing sintering the graphene / CuCrZr mixed powder to obtain graphene / CuCrZr composite blank, in which the mass percentages of the components are as follows: graphene content of 0.5-2 wt.%, Cr content of 0.8-1.2 wt.%, Zr content of 0.3-0.7 wt.%, and the balance of Cu; (4) vacuum smelting the oxygen-free copper material and the graphene / CuCrZr composite blank, stirring, then conducting downward continuous casting, continuous extrusion, continuous drawing, and online non-contact annealing to obtain the graphene / CuCrZr composite wire. In step (4), the temperature of the downward continuous casting is 1150-1200℃.

5. The method for preparing the high thermal conductivity and low temperature rise graphene / CuCrZr composite wire according to claim 4, characterized in that, The acoustic resonance mixing conditions are as follows: acceleration of 50-100 g, vibration frequency of 20-80 Hz, vibration intensity of 20-50%, and mixing time of 1-10 min.

6. The method for preparing the high thermal conductivity and low temperature rise graphene / CuCrZr composite wire according to claim 4, characterized in that, The graphene powder has a diameter < 20 μm, a layer number < 10, and a specific surface area of 50-150 m 2 / g.

7. The method for preparing the high thermal conductivity and low temperature rise graphene / CuCrZr composite wire according to claim 4, characterized in that, The temperature of the vacuum hot-press sintering is 950-1050℃, the time is 3-5 h, the pressure is 20-50 MPa, and the vacuum degree is 10 -3 ~10 -1 Pa.

8. The method for preparing the high thermal conductivity and low temperature rise graphene / CuCrZr composite wire according to claim 4, characterized in that, The mass ratio of the graphene / CuCrZr composite blank to the oxygen-free copper material is 1:1-19.

9. The method for preparing the high thermal conductivity and low temperature rise graphene / CuCrZr composite wire according to claim 4, characterized in that, In the online non-contact annealing step, the annealing temperature is 500-580℃, the annealing speed is 0.4-0.6 m / min, and the annealing atmosphere is argon.

10. Application of the graphene / CuCrZr composite wire with high thermal conductivity and low temperature rise according to any one of claims 1-3 in density electronic packaging and interconnection.

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