A non-oxygen copper plate and a preparation method thereof

Abstract

The application relates to the technical field of high-end metal material preparation, and provides oxygen-free copper plate and a preparation method thereof, which comprises the following steps: preparing carbon-coated copper powder through a gas deposition method; forming the carbon-coated copper powder into carbon-coated copper powder green bodies through cold isostatic pressing; obtaining sintered bodies by sintering heat treatment of the carbon-coated copper powder green bodies; forming the sintered bodies into dense bodies through hot isostatic pressing densification treatment; and forming the dense bodies into oxygen-free copper plate through hot rolling deformation treatment. According to the oxygen-free copper plate and the preparation method thereof, the oxygen content can be effectively controlled and the conductivity can be improved, the compactness and the performance stability of the material structure are significantly improved, fine and uniform microstructure and excellent toughening effect are obtained, and the high-temperature stability and service performance of the material are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of high-end metal material preparation technology, and in particular to an oxygen-free copper plate and its preparation method. Background Technology

[0002] Oxygen-free copper sheets, with their superior electrical and thermal conductivity, good plasticity, and chemical stability, have become key materials in high-end fields such as aerospace heat dissipation components, semiconductor packaging lead frames, 5G communication base station RF modules, and new energy vehicle power modules. Their core function is to achieve efficient electron transfer and heat dissipation, ensuring the stable and reliable operation of various precision electronic devices under harsh conditions such as high temperature, high frequency, and high current.

[0003] Currently, the mainstream preparation technologies for oxygen-free copper plates are mainly divided into three categories, but all of them have varying degrees of technical bottlenecks.

[0004] The first type is the upward continuous casting-continuous extrusion / rolling process. This process involves continuously casting molten electrolytic copper in an inert or reducing atmosphere, followed by multiple extrusion and rolling passes to obtain the sheet material. Its advantages lie in high production efficiency and suitability for large-scale continuous production, often used to manufacture low- to mid-range general-purpose products. However, its drawbacks include: the melting process easily introduces oxygen impurities and oxide inclusions, making it difficult to stably control the oxygen content of the material below 10 ppm, thus deteriorating its core electrical and thermal conductivity; defects such as subsurface shrinkage and grain boundary segregation are easily generated during continuous casting and rolling. During subsequent high-temperature annealing, residual oxides react with hydrogen to generate water vapor, leading to bubbles on the sheet surface. To reduce oxygen content, existing technologies typically increase the number of peeling passes to remove near-surface defects, but this method significantly reduces material utilization, increases production costs, and cannot fundamentally eliminate oxygen impurities and defects within the material.

[0005] The second type is the pyrometallurgical refining process, which mainly uses scrap copper as raw material. Impurities are removed through oxidation-reduction refining to directly produce high-purity oxygen-free copper. This process has strong raw material adaptability and a shorter process flow, which helps reduce raw material costs. Its core drawbacks are: the refining process easily generates harmful gases and waste residue, putting significant environmental pressure on the industry; at the same time, it is difficult to precisely control the content of trace impurities, resulting in poor uniformity of the prepared substrate structure and large fluctuations in conductivity, failing to meet the stringent requirements for material performance consistency in high-end applications such as semiconductor packaging. Although existing technologies attempt to optimize the process and improve purity by adding various refining agents, the residue of the refining agents themselves can introduce new impurities, potentially further deteriorating material performance.

[0006] The third category is traditional powder metallurgy, which uses conventional electrolytic copper powder as raw material, and densifies it through pressing and sintering to prepare plates. Theoretically, this approach can reduce impurity content and produce high-purity oxygen-free copper by controlling the purity of the raw materials. However, to address the problems of easy oxidation and insufficient density of conventional copper powder during sintering, existing technologies use hydrogen reduction sintering or add antioxidants. However, the added antioxidants remain inside the material, forming second-phase impurities that significantly impair the material's electrical and thermal conductivity. At the same time, conventional electrolytic copper powder is prone to abnormal grain growth during sintering, leading to a decrease in the mechanical properties of the plate, making it difficult to meet the requirements of applications such as ultra-thin strips and precision electrodes that require a synergistic optimization of strength and conductivity.

[0007] In summary, oxygen-free copper substrates prepared using existing technologies generally exhibit three major common defects in applications: 1. High oxygen and impurity content, making it difficult to consistently achieve conductivity above 99% IACS, resulting in significant signal transmission loss and heat accumulation issues in ultra-high-end applications such as high-frequency communication and low-temperature superconductivity; 2. Poor material uniformity and large grain size fluctuations, leading to differences in mechanical and processing properties across different regions of the substrate. This can easily cause cracks, delamination, and dimensional deviations during subsequent precision stamping, welding, and other processing, reducing yield; 3. Insufficient high-temperature stability, making it prone to grain coarsening during high-temperature processes such as ceramic-copper welding, affecting the connection strength and thermal cycling resistance of the encapsulated components.

[0008] Therefore, how to provide a preparation method that can fundamentally control oxygen content and impurities and precisely regulate microstructure, and through innovation in powder metallurgy processes, synergistically achieve high density and uniform grain structure of materials, and avoid performance degradation caused by excessive porosity or abnormal grain growth, has become an urgent technical problem to be solved. Summary of the Invention

[0009] In view of this, in order to overcome the shortcomings of the prior art, the present invention aims to provide an oxygen-free copper plate and a method for preparing the same.

[0010] According to a first aspect of the present invention, a method for preparing oxygen-free copper sheet is provided, the method comprising: preparing carbon-coated copper powder by vapor deposition, forming the carbon-coated copper powder into a carbon-coated copper powder green blank by cold isostatic pressing, sintering the carbon-coated copper powder green blank to obtain a sintered blank, forming the sintered blank into a dense blank by hot isostatic pressing densification treatment, and forming the dense blank into an oxygen-free copper sheet by hot rolling deformation treatment.

[0011] Optionally, in the method for preparing oxygen-free copper plates of the present invention, graphite is used as a carbon source, carbon vapor is generated by excitation with 50-200kw power, and -200 mesh electrolytic copper powder is fed to the hot melt coating zone at 800-1000℃ at a powder feeding rate of 20-120g / min, so that the vaporized carbon vapor coats the surface of the copper powder to prepare carbon-coated copper powder.

[0012] Optionally, in the method for preparing oxygen-free copper sheet of the present invention, carbon-coated copper powder is filled into a silicone sleeve mold, compacted and sealed, and then placed in a cold isostatic press. The pressure is increased to 100-300 MPa at a pressurization rate of 10-40 MPa / min, and the pressure is held for 5-30 minutes before demolding to obtain a carbon-coated copper powder green blank.

[0013] Optionally, in the method for preparing oxygen-free copper plates of the present invention, carbon-coated copper powder green blanks are sintered and heat-treated in a sintering atmosphere composed of a mixture of nitrogen and hydrogen, wherein the nitrogen flow rate is 2.1 L / min and the hydrogen flow rate is 0.7 L / min.

[0014] Optionally, in the method for preparing oxygen-free copper plates of the present invention, carbon-coated copper powder green blanks are heated to 820-980°C at a rate of 5-10°C / min in a sintering atmosphere, held at that temperature for 1-2 hours, and then cooled in the furnace to obtain sintered blanks.

[0015] Optionally, in the method for preparing oxygen-free copper plates of the present invention, the sintered billet is placed in a hot isostatic pressing furnace under an argon atmosphere, heated to 760-960°C, and simultaneously pressurized to 80-150 MPa using argon as the transfer medium. After both temperature and pressure are reached, the billet is held at the temperature and pressure for 1-2 hours. After the holding and pressurization are completed, the billet is cooled to room temperature at a rate of 10°C / min, and simultaneously depressurized to atmospheric pressure at a rate of 10 MPa / min to obtain a dense billet.

[0016] Optionally, in the oxygen-free copper plate preparation method of the present invention, the heating rate is 5-10℃ / min and the pressurization rate is 0.5-1MPa / min.

[0017] Optionally, in the method for preparing oxygen-free copper sheet of the present invention, a dense billet is hot rolled in multiple passes in a high-purity argon atmosphere. After hot rolling, the billet is slowly cooled in the furnace to 400°C and then air-cooled to obtain oxygen-free copper sheet.

[0018] Optionally, in the method for preparing oxygen-free copper sheet of the present invention, the initial rolling temperature is 800-900℃, the single reduction deformation is 20-50%, the intermediate rolling temperature is 700-850℃, the single reduction deformation is 10-20%, and the final rolling temperature is 650-750℃, the single reduction deformation is 5-10%.

[0019] According to a second aspect of the present invention, an oxygen-free copper sheet is provided, which is prepared according to the method described above.

[0020] The oxygen-free copper plate and its preparation method of the present invention have the following beneficial technical effects:

[0021] 1. Effectively control oxygen content and improve conductivity

[0022] A carbon layer is uniformly coated onto the surface of electrolytic copper powder using vapor deposition, forming a core-shell structure of carbon-coated copper powder. During subsequent sintering and densification, the coated carbon reacts with residual oxygen in the copper powder to generate CO2 gas, which is then released from the system. This process actively eliminates oxygen impurities at the source, resulting in oxygen-free copper sheets with a stable oxygen content below 10 ppm. This extremely low oxygen content significantly reduces electron scattering centers, ensuring that the material's conductivity consistently reaches and exceeds 100% IACS, meeting the stringent requirements for extremely low transmission loss in ultra-high-end applications such as high-frequency communication and low-temperature superconductivity.

[0023] 2. Significantly improves the density and performance stability of the material structure.

[0024] By employing a densification path combining cold isostatic pressing (CIP) and sintering with hot isostatic pressing (HIP), the density of the preform is progressively increased, significantly reducing the scattering of electrons and phonons (heat carriers) by pores. This lays the structural foundation for high electrical and thermal conductivity, enhances the material's mechanical properties, and improves its reliability during service. Since the sintered preform itself possesses high density and excellent resistance to media penetration, the subsequent HIP process eliminates the need for the metal sheathing required in traditional processes. This eliminates the entire process of sheath design, preparation, and removal, significantly reducing costs and time. It also eliminates product defects caused by uneven sheathing constraints, interface contamination, or differences in heat transfer, improving the dimensional accuracy, microstructure uniformity, and performance stability of the final product.

[0025] 3. Achieve fine and uniform microstructure and excellent toughening effect.

[0026] During the high-temperature treatment of carbon-coated copper powder, residual carbon elements agglomerate at the grain boundaries. The subsequent multi-pass temperature-controlled hot rolling deformation refines the carbon dispersed at the grain boundaries, creating a strong "pinning" effect that effectively hinders grain boundary migration. The oxygen-free copper sheet prepared by this invention has a fine and uniform equiaxed grain structure, with the grain size effectively controlled within 3-10 micrometers. This results in a significant grain refinement strengthening effect, improving the material's strength and hardness while maintaining good plasticity, achieving synergistic optimization of strength and conductivity.

[0027] 4. Significantly improves the high-temperature stability and service performance of materials.

[0028] Carbon pinned to grain boundaries not only strengthens the material at room temperature, but more importantly, it effectively inhibits abnormal grain growth during subsequent high-temperature processing (such as ceramic-copper welding) or high-temperature service conditions. This allows the material to maintain structural stability at high temperatures, avoiding the risk of decreased mechanical properties and interface failure caused by grain coarsening. The combined effect of low oxygen content and carbon pinning to grain boundaries hinders the diffusion of oxygen atoms along the grain boundaries, improving the material's oxidation and corrosion resistance and extending its service life in harsh environments. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The images show the microstructure of the 200-mesh electrolytic copper powder in Examples 1-5 of this invention, magnified 2000 times.

[0031] Figure 2 These are 500x magnification images of the -200 mesh electrolytic copper powder used in Examples 1-5 of this invention.

[0032] Figure 3 This is a 2000x magnification image of the carbon-coated copper powder prepared in Example 2 of the present invention.

[0033] Figure 4 This is a copper element distribution diagram of the carbon-coated copper powder prepared in Example 2 of the present invention;

[0034] Figure 5 This is a carbon element distribution diagram of the carbon-coated copper powder prepared in Example 2 of the present invention;

[0035] Figure 6 This is a 100x magnification metallographic image of the sintered billet prepared in Example 2 of the present invention.

[0036] Figure 7 This is a 400x magnification metallographic image of the sintered blank prepared in Example 2 of the present invention;

[0037] Figure 8 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 1 of the present invention.

[0038] Figure 9 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 2 of the present invention;

[0039] Figure 10 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 3 of the present invention.

[0040] Figure 11 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 4 of the present invention.

[0041] Figure 12 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 5 of the present invention. Detailed Implementation

[0042] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0043] It should be noted that, in the absence of conflict, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0044] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0045] Example 1

[0046] Step 1: Preparation of carbon-coated copper powder

[0047] Using graphite as a carbon source, carbon vapor is generated by excitation with 50kw power. -200 mesh electrolytic copper powder is fed to the hot melt coating zone at 800℃ at a powder feeding rate of 20g / min, so that the vaporized carbon vapor coats the surface of the copper powder to obtain carbon-coated copper powder.

[0048] Step 2: Preparation of carbon-coated copper powder green body

[0049] Carbon-coated copper powder is filled into a silicone sleeve mold, compacted and sealed, and then placed in a cold isostatic press. The pressure is increased to 100 MPa at a rate of 40 MPa / min, and the pressure is held for 30 minutes before demolding to obtain a carbon-coated copper powder green body.

[0050] Step 3: Sintering heat treatment

[0051] Carbon-coated copper powder green blanks are placed in a tube sintering furnace with permeable atmosphere. After the air is removed, a nitrogen-hydrogen mixed gas is introduced to maintain the sintering atmosphere. The nitrogen flow rate is 2.1 L / min and the hydrogen flow rate is 0.7 L / min. The temperature is raised to 980℃ at a rate of 5℃ / min, held for 1 hour, and then cooled with the furnace to obtain sintered green blanks.

[0052] Step 4: Hot Isostatic Pressing Densification Treatment

[0053] The sintered billet was placed in a hot isostatic pressing furnace under an argon atmosphere and heated to 760°C at a rate of 5°C / min. Simultaneously, it was pressurized to 150MPa at a rate of 1MPa / min using argon as the transfer medium. After both temperature and pressure were reached, the billet was held at the temperature and pressure for 1 hour. After the holding and pressure were completed, the billet was cooled to room temperature at a rate of 10°C / min and simultaneously depressurized to atmospheric pressure at a rate of 10MPa / min to obtain a dense billet.

[0054] Step 5: Hot Rolling Deformation Treatment

[0055] In a high-purity argon atmosphere, a dense billet is subjected to multiple hot rolling passes. The initial rolling temperature is 800℃ with a single reduction of 50%, the intermediate rolling temperature is 800℃ with a single reduction of 20%, and the final rolling temperature is 650℃ with a single reduction of 10%. After hot rolling, the billet is slowly cooled in the furnace to 400℃ and then air-cooled to obtain oxygen-free copper sheet.

[0056] Example 2

[0057] Step 1: Preparation of carbon-coated copper powder

[0058] Using graphite as a carbon source, carbon vapor is generated by excitation with 85kw power. -200 mesh electrolytic copper powder is fed to the hot melt coating zone at 860℃ at a powder feeding rate of 50g / min, so that the vaporized carbon vapor coats the surface of the copper powder to obtain carbon-coated copper powder.

[0059] Step 2: Preparation of carbon-coated copper powder green body

[0060] The carbon-coated copper powder is filled into a silicone sleeve mold, compacted and sealed, and then placed in a cold isostatic press. The pressure is increased to 150 MPa at a rate of 30 MPa / min, and the pressure is held for 25 minutes before demolding to obtain a carbon-coated copper powder green body.

[0061] Step 3: Sintering heat treatment

[0062] Carbon-coated copper powder green blanks are placed in a tube sintering furnace with permeable atmosphere. After the air is removed, a nitrogen-hydrogen mixed gas is introduced to maintain the sintering atmosphere. The nitrogen flow rate is 2.1 L / min and the hydrogen flow rate is 0.7 L / min. The temperature is raised to 950℃ at a rate of 7℃ / min, held for 1 hour, and then cooled with the furnace to obtain sintered green blanks.

[0063] Step 4: Hot Isostatic Pressing Densification Treatment

[0064] The sintered billet was placed in a hot isostatic pressing furnace under an argon atmosphere and heated to 800°C at a rate of 8°C / min. Simultaneously, it was pressurized to 100MPa at a rate of 1MPa / min using argon as the transfer medium. After both temperature and pressure were reached, the billet was held at the temperature and pressure for 1 hour. After the holding and pressure were completed, the billet was cooled to room temperature at a rate of 10°C / min and simultaneously depressurized to atmospheric pressure at a rate of 10MPa / min to obtain a dense billet.

[0065] Step 5: Hot Rolling Deformation Treatment

[0066] In a high-purity argon atmosphere, a dense billet is hot rolled in multiple passes. The initial rolling temperature is 860℃ with a single reduction of 40%, the intermediate rolling temperature is 800℃ with a single reduction of 10%, and the final rolling temperature is 750℃ with a single reduction of 8%. After hot rolling, the billet is slowly cooled in the furnace to 400℃ and then air-cooled to obtain oxygen-free copper sheet.

[0067] Example 3

[0068] Step 1: Preparation of carbon-coated copper powder

[0069] Using graphite as a carbon source, carbon vapor is generated by excitation with 120kw power. -200 mesh electrolytic copper powder is fed to the hot melt coating zone at 950℃ at a powder feeding rate of 100g / min, so that the vaporized carbon vapor coats the surface of the copper powder to obtain carbon-coated copper powder.

[0070] Step 2: Preparation of carbon-coated copper powder green body

[0071] The carbon-coated copper powder was filled into a silicone sleeve mold, compacted and sealed, and then placed in a cold isostatic press. The pressure was increased to 200 MPa at a rate of 25 MPa / min, and the mold was demolded after holding the pressure for 20 minutes to obtain a carbon-coated copper powder green body.

[0072] Step 3: Sintering heat treatment

[0073] Carbon-coated copper powder green blanks are placed in a tube sintering furnace with permeable atmosphere. After the air is removed, a nitrogen-hydrogen mixed gas is introduced to maintain the sintering atmosphere. The nitrogen flow rate is 2.1 L / min and the hydrogen flow rate is 0.7 L / min. The temperature is raised to 900℃ at a rate of 7℃ / min, held for 1.5 h, and then cooled with the furnace to obtain sintered green blanks.

[0074] Step 4: Hot Isostatic Pressing Densification Treatment

[0075] The sintered billet was placed in a hot isostatic pressing furnace under an argon atmosphere and heated to 850°C at a rate of 5°C / min. Simultaneously, it was pressurized to 136 MPa at a rate of 0.8 MPa / min using argon as the transfer medium. After both temperature and pressure were reached, the billet was held at the temperature and pressure for 1.5 hours. After the holding and pressure were completed, the billet was cooled to room temperature at a rate of 10°C / min and simultaneously depressurized to atmospheric pressure at a rate of 10 MPa / min to obtain a dense billet.

[0076] Step 5: Hot Rolling Deformation Treatment

[0077] In a high-purity argon atmosphere, a dense billet is subjected to multiple hot rolling passes. The initial rolling temperature is 800℃ with a single reduction of 30%, the intermediate rolling temperature is 700℃ with a single reduction of 15%, and the final rolling temperature is 700℃ with a single reduction of 10%. After hot rolling, the billet is slowly cooled in the furnace to 400℃ and then air-cooled to obtain oxygen-free copper sheet.

[0078] Example 4

[0079] Step 1: Preparation of carbon-coated copper powder

[0080] Using graphite as a carbon source, carbon vapor is generated by excitation with 160kw power. -200 mesh electrolytic copper powder is fed to the hot melt coating zone at 900℃ at a powder feeding rate of 120g / min, so that the vaporized carbon vapor coats the surface of the copper powder to obtain carbon-coated copper powder.

[0081] Step 2: Preparation of carbon-coated copper powder green body

[0082] Carbon-coated copper powder is filled into a silicone sleeve mold, compacted and sealed, and then placed in a cold isostatic press. The pressure is increased to 260 MPa at a rate of 15 MPa / min, and the pressure is held for 10 minutes before demolding to obtain a carbon-coated copper powder green body.

[0083] Step 3: Sintering heat treatment

[0084] Carbon-coated copper powder green blanks are placed in a tube sintering furnace with permeable atmosphere. After the air is removed, a nitrogen-hydrogen mixed gas is introduced to maintain the sintering atmosphere. The nitrogen flow rate is 2.1 L / min and the hydrogen flow rate is 0.7 L / min. The temperature is raised to 850℃ at a rate of 10℃ / min, held for 2 hours, and then cooled with the furnace to obtain sintered green blanks.

[0085] Step 4: Hot Isostatic Pressing Densification Treatment

[0086] The sintered billet was placed in a hot isostatic pressing furnace under an argon atmosphere and heated to 900°C at a rate of 10°C / min. Simultaneously, it was pressurized to 100MPa at a rate of 1MPa / min using argon as the transfer medium. After both temperature and pressure were reached, the billet was held at the temperature and pressure for 2 hours. After the holding and pressure were completed, the billet was cooled to room temperature at a rate of 10°C / min and simultaneously depressurized to atmospheric pressure at a rate of 10MPa / min to obtain a dense billet.

[0087] Step 5: Hot Rolling Deformation Treatment

[0088] In a high-purity argon atmosphere, a dense billet is subjected to multiple hot rolling passes. The initial rolling temperature is 900℃ with a single reduction of 20%, the intermediate rolling temperature is 850℃ with a single reduction of 15%, and the final rolling temperature is 750℃ with a single reduction of 5%. After hot rolling, the billet is slowly cooled to 400℃ in the furnace and then air-cooled to obtain oxygen-free copper sheet.

[0089] Example 5

[0090] Step 1: Preparation of carbon-coated copper powder

[0091] Using graphite as a carbon source, carbon vapor is generated by excitation with 200kw power. -200 mesh electrolytic copper powder is fed to the hot melt coating zone at 1000℃ at a powder feeding rate of 120g / min, so that the vaporized carbon vapor coats the surface of the copper powder to obtain carbon-coated copper powder.

[0092] Step 2: Preparation of carbon-coated copper powder green body

[0093] Carbon-coated copper powder is filled into a silicone sleeve mold, compacted and sealed, and then placed in a cold isostatic press. The pressure is increased to 300 MPa at a rate of 10 MPa / min, and the mold is demolded after holding the pressure for 5 minutes to obtain a carbon-coated copper powder green body.

[0094] Step 3: Sintering heat treatment

[0095] Carbon-coated copper powder green blanks are placed in a tube sintering furnace with permeable atmosphere. After the air is removed, a nitrogen-hydrogen mixed gas is introduced to maintain the sintering atmosphere. The nitrogen flow rate is 2.1 L / min and the hydrogen flow rate is 0.7 L / min. The temperature is raised to 820℃ at a rate of 10℃ / min, held for 2 hours, and then cooled with the furnace to obtain sintered green blanks.

[0096] Step 4: Hot Isostatic Pressing Densification Treatment

[0097] The sintered billet was placed in a hot isostatic pressing furnace under an argon atmosphere and heated to 960°C at a rate of 6°C / min. Simultaneously, the pressure was increased to 80 MPa at a rate of 0.5 MPa / min using argon as the transfer medium. After both temperature and pressure were reached, the billet was held at the temperature and pressure for 2 hours. After the holding and pressure were completed, the billet was cooled to room temperature at a rate of 10°C / min and simultaneously depressurized to atmospheric pressure at a rate of 10 MPa / min to obtain a dense billet.

[0098] Step 5: Hot Rolling Deformation Treatment

[0099] In a high-purity argon atmosphere, a dense billet is hot rolled in multiple passes. The initial rolling temperature is 800℃ with a single reduction of 30%, the intermediate rolling temperature is 750℃ with a single reduction of 10%, and the final rolling temperature is 700℃ with a single reduction of 5%. After hot rolling, the billet is slowly cooled in the furnace to 400℃ and then air-cooled to obtain oxygen-free copper sheet.

[0100] Example 6

[0101] The microstructure of the -200 mesh electrolytic copper powder in Examples 1-5 was analyzed using a Hitachi SU8020 scanning electron microscope. The accelerating voltage used was 5 kV, and the magnification was 500x and 2000x. Figure 1These are 2000x magnification images of the microstructure of the -200 mesh electrolytic copper powder used in Examples 1-5 of this invention. Figure 2 The image shows the microstructure of the 200-mesh electrolytic copper powder in Examples 1-5 of this invention, magnified 500 times.

[0102] like Figure 1 and Figure 2 As shown, the electrolytic copper powder used in the embodiments of the present invention has a dendritic morphology with certain sharp edges, excellent loose density, flowability, and formability. The well-developed dendritic morphology facilitates molding and sintering. The pressed green body has high strength, and the particles are tightly bonded during sintering, which can improve the material density (up to 95% or more). At the same time, its particle size and particle size distribution are controllable, and it has high compatibility with powder metallurgy processes and atmosphere sintering, making it suitable for large-scale production. It is a high-quality raw material for preparing high-quality oxygen-free copper.

[0103] The carbon-coated copper powder prepared in Example 2 was subjected to microstructure analysis and energy dispersive spectroscopy analysis using a Hitachi SU8020 scanning electron microscope. The accelerating voltage was 15 kV and the magnification was 2000x. Figure 3 This is a 2000x magnification image of the carbon-coated copper powder prepared in Example 2 of the present invention. Figure 4 This is a copper element distribution diagram of the carbon-coated copper powder prepared in Example 2 of the present invention. Figure 5 This is a carbon element distribution diagram of the carbon-coated copper powder prepared in Example 2 of the present invention.

[0104] like Figure 3 As shown, after carbon coating treatment, the dendritic morphology remains unchanged, and the surface becomes smooth. Figure 3 and Figure 4 As shown, the EDS surface distribution scan results reveal that the copper powder, after carbon coating treatment, exhibits a core-shell structure: Cu elements are concentrated in the particle core, while C elements are uniformly coated on the surface of the Cu core, forming a continuous and complete carbon layer. During the densification process of the carbon-coated copper powder, carbon reacts with oxygen in the copper powder to generate CO2, which is released and helps reduce the oxygen content. The remaining carbon exists in the form of a thin film, dispersed in the matrix, acting as a grain boundary pinning agent, effectively inhibiting grain growth at high temperatures, and significantly improving the heat resistance of oxygen-free copper.

[0105] The densities of the green, sintered, and dense blanks prepared in Examples 1-5 were determined using the Archimedes' displacement method. Samples were taken using a DK7702 wire EDM machine, with a sample size of φ10mm*10mm. The densities of the green, sintered, and dense blanks prepared in Examples 1-5 of this invention are shown in Table 1.

[0106] Table 1

[0107]

[0108] As shown in Table 1, the density of the green billet increases with increasing cold isostatic pressing pressure. Sintered billets all achieve a density of over 95%, exhibiting excellent resistance to high-pressure media penetration. Hot isostatic pressing eliminates the need for a casing, offering advantages such as: eliminating the entire process of casing design, preparation, and removal, significantly reducing costs and shortening the cycle time; eliminating casing-related unevenness, interface contamination, and differences in heat transfer, improving product dimensional accuracy, microstructure uniformity, and performance stability; overcoming casing size limitations, adapting to complex / large-sized billets, enhancing production flexibility, and reducing environmental and safety risks. The density of the dense billet is greater than 99%, significantly reducing the scattering effect of pores on electron and phonon conduction, which helps improve electrical and thermal conductivity (>100% IACS), enhances mechanical properties, and is suitable for high-end electronic heat dissipation scenarios, improving service reliability.

[0109] The oxygen content of the oxygen-free copper plates prepared in Examples 1-5 of this invention was tested using a 0-3000 oxygen content analyzer. Samples were taken using a DK7702 wire cutting machine, with a sample size of φ2mm*5mm. The electrical conductivity of the oxygen-free copper plates prepared in Examples 1-5 was tested using a PZ60A metal conductivity meter. Samples were taken using a DK7702 wire cutting machine, with a sample size of φ30mm*10mm.

[0110] The oxygen content and electrical conductivity of the oxygen-free copper plates prepared in Examples 1-5 of this invention are shown in Table 2.

[0111] Table 2

[0112]

[0113] As shown in Table 2, the oxygen content of the oxygen-free copper plates prepared in Examples 1-5 is ≤10ppm, which can significantly reduce the obstruction of electron conduction by oxygen impurities, and make the conductivity of oxygen-free copper stably reach 100% or more. At the same time, it can eliminate grain boundary brittleness, enhance oxidation and corrosion resistance, and extend service life.

[0114] As shown in Table 2, the electrical conductivity of the oxygen-free copper plates prepared in Examples 1-5 is greater than 100% IACS, which can significantly reduce electron / heat transfer loss and is suitable for scenarios such as low-temperature superconductivity, high-frequency communication, and high-power heat dissipation, thereby reducing transmission loss and temperature rise. At the same time, relying on ultra-high purity and uniform structure, the processing plasticity and service stability are improved, and the manufacturing cost is reduced.

[0115] The microstructure of the sintered billet prepared in Example 2 and the oxygen-free copper plates prepared in Examples 1-5 were analyzed using a LEICA DM 2500M upright wide-field metallographic microscope. Samples were taken using a DK7702 wire cutting machine with a sample size of φ10mm*10mm. Figure 6 This is a 100x magnification metallographic image of the sintered billet prepared in Example 2 of the present invention. Figure 7This is a 400x magnification metallographic image of the sintered blank prepared in Example 2 of the present invention. Figure 8 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 1 of this invention. Figure 9 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 2 of the present invention. Figure 10 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 3 of the present invention. Figure 11 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 4 of the present invention. Figure 12 This is a 2000x magnification metallographic image of the oxygen-free copper plate prepared in Example 5 of the present invention.

[0116] like Figure 6 and Figure 7 As shown, the sintered billet prepared in Example 2 has a grain size of 50-100 μm, no obvious porosity, and excellent resistance to high-pressure media penetration. Hot isostatic pressing does not require a casing, and the core benefits are significant: First, it eliminates the entire process of casing design, preparation, and removal, greatly reducing costs and shortening the cycle; second, it eliminates uneven casing constraints, interface contamination, and differences in heat transfer, improving product dimensional accuracy, microstructure uniformity, and performance stability; third, it breaks through the limitations of casing size, adapts to complex / large-sized billets, enhances production flexibility, and reduces environmental and safety risks.

[0117] like Figure 8-12 As shown, the oxygen-free copper plates prepared in Examples 1-5 have a fine and uniform microstructure with a grain size of 3-10 μm and black material pinning the grain boundaries. Combined with the previous carbon coating process and compositional characterization results, this was confirmed to be elemental carbon, a product of the carbon coating layer segregating at the grain boundaries during high-temperature densification. The fine grain size helps withstand higher operating temperatures; the carbon pinning at the grain boundaries effectively hinders grain boundary migration and grain coarsening, effectively suppressing grain growth and contributing to improved stability under high-temperature conditions, achieving synergistic optimization of strength and conductivity; simultaneously, it can prevent oxygen atoms from diffusing along the grain boundaries, improving oxidation and corrosion resistance.

[0118] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing oxygen-free copper sheet, characterized in that, The method includes: preparing carbon-coated copper powder by vapor deposition; forming the carbon-coated copper powder into a carbon-coated copper powder green blank by cold isostatic pressing; sintering and heat-treating the carbon-coated copper powder green blank to obtain a sintered blank; forming the sintered blank into a dense blank by hot isostatic pressing densification treatment; and forming the dense blank into an oxygen-free copper plate by hot rolling deformation treatment. Using graphite as a carbon source, carbon vapor is generated by excitation with a power of 50-200 kW. -200 mesh electrolytic copper powder is fed at a powder feeding rate of 20-120 g / min to a hot-melt coating zone at 800-1000℃, so that the vaporized carbon vapor coats the surface of the copper powder, thus preparing carbon-coated copper powder. The carbon-coated copper powder is filled into a silicone sleeve mold, compacted and sealed, and then placed in a cold isostatic press. The pressure is increased to 100-300 MPa at a pressurization rate of 10-40 MPa / min, and held at pressure. After 5-30 minutes, the carbon-coated copper powder green blank is demolded to obtain a carbon-coated copper powder green blank. The carbon-coated copper powder green blank is sintered and heat-treated in a sintering atmosphere composed of a nitrogen and hydrogen mixture, wherein the nitrogen flow rate is 2.1 L / min and the hydrogen flow rate is 0.7 L / min. In the sintering atmosphere, the carbon-coated copper powder green blank is heated to 820-980℃ at a rate of 5-10℃ / min, held at this temperature for 1-2 hours, and then cooled in the furnace to obtain a sintered blank. The sintered blank is placed in a hot isostatic pressing furnace in an argon atmosphere, heated to 760-960℃, and simultaneously pressurized to 80-150MPa using argon as the transfer medium. After both temperature and pressure are reached, the blank is held at this temperature and pressure for 1-2 hours. After the holding and pressurization are completed, the blank is cooled to room temperature at a rate of 10℃ / min, and simultaneously depressurized to atmospheric pressure at a rate of 10MPa / min to obtain a dense blank.

2. The method for preparing oxygen-free copper plate according to claim 1, characterized in that, During hot isostatic pressing, the heating rate is 5-10℃ / min, and the pressurization rate is 0.5-1MPa / min.

3. The method for preparing oxygen-free copper plate according to claim 1, characterized in that, In a high-purity argon atmosphere, a dense billet is hot rolled in multiple passes. After hot rolling, it is slowly cooled in the furnace to 400°C and then air-cooled to obtain oxygen-free copper sheet.

4. The method for preparing oxygen-free copper plate according to claim 3, characterized in that, The initial rolling temperature is 800-900℃, with a single reduction deformation of 20-50%; the intermediate rolling temperature is 700-850℃, with a single reduction deformation of 10-20%; and the final rolling temperature is 650-750℃, with a single reduction deformation of 5-10%.

5. An oxygen-free copper plate, characterized in that, The oxygen-free copper plate is prepared by the method according to any one of claims 1 to 4.

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