High thermal conductivity diamond / copper composite material and sintering process thereof by spark plasma sintering

Abstract

The application provides a high-thermal-conductivity diamond / copper composite material and an SPS sintering process thereof, raw material pretreatment: selecting three kinds of monocrystalline diamond particles with different particle sizes, mixing the titanium-plated diamond obtained after vacuum titanium plating treatment; solid dry powder mixing: uniformly mixing a solid additive and graphene modified copper powder to prepare a copper-based composite dry powder; nitrogen intermittent airflow suspension dispersion: adding the titanium-plated diamond into a sealed covering tank to make the titanium-plated diamond suspended and dispersed in the sealed covering tank; atomization covering makes the copper-based composite dry powder uniformly covered on the surface of the titanium-plated diamond to obtain composite particles; vacuum low-temperature degreasing to obtain the composite particles after degreasing, and SPS sintering demolding to obtain the high-thermal-conductivity diamond / copper composite material. The coating is uniform and dense, has no exposure and no agglomeration, and significantly reduces porosity and interface thermal resistance; the proportioning is accurate, the degreasing is thorough, and there is no residue; the generation of brittle phases is inhibited, and the interface combination is excellent; the thermal conductivity is stable and greater than 700 W / (m*K), and the density is greater than or equal to 99%.

Description

Technical Field

[0001] This invention belongs to the technical field of metal-based high thermal conductivity composite materials, specifically relating to a diamond / copper composite material with a thermal conductivity >700 W / (m·K), and particularly to a preparation process that employs intermittent nitrogen gas flow suspension dispersion, mixing of solid binder with copper powder dry powder, independent atomization coating with isopropanol, combined with vacuum degreasing and spark plasma sintering (SPS). Background Technology

[0002] With the rapid development of high-power semiconductor devices, laser equipment, 5G communications, and new energy vehicle industries, high-end electronic components place extremely high demands on the thermal conductivity of heat sink materials. Traditional copper, aluminum, and alloy materials can no longer meet the heat dissipation requirements of ultra-high power devices. Diamond / copper composite materials combine the ultra-high thermal conductivity and low coefficient of thermal expansion of diamond with the excellent electrical and thermal conductivity and processability of copper, making them the preferred choice for next-generation high-end heat dissipation packaging materials. However, their industrial application still faces many technical bottlenecks.

[0003] In existing diamond / copper composite material preparation processes, coating methods such as mechanical mixing, wet stirring, and ball milling are prone to problems such as copper powder agglomeration, insufficient uniform distribution, exposure of coarse-grained diamond surfaces, and particle oxidation and damage. This results in high internal porosity and high interfacial thermal resistance. Simultaneously, improper formulation of conventional organic additives leads to poor slurry atomization, uneven coating layers, and residual impurities after degreasing, further reducing the material's thermal conductivity. Consequently, the thermal conductivity of similar products in the industry is generally below 700 W / (m·K), failing to meet the heat dissipation requirements of high-end devices. Furthermore, traditional sintering processes involve slow heating and long holding times, easily triggering excessive reactions at the diamond-copper matrix interface, generating brittle phases and compromising the overall material properties. Therefore, developing a process that achieves uniform, oxidation-free diamond coating, scientifically proportioned additives, precise sintering, and stable preparation of diamond / copper composite materials with a thermal conductivity >700 W / (m·K) has become a pressing technical problem to be solved in this field. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies, such as uneven diamond distribution, difficulty in achieving thermal conductivity exceeding 700 W / (m·K), and poor interfacial bonding. It provides a high thermal conductivity diamond / copper composite material and its SPS sintering process. Through a nitrogen intermittent gas flow suspension atomization coating process, combined with a specialized binder, inhibitor, and diluent system, and precise temperature-controlled degreasing and SPS sintering, uniform distribution of coarse-grained titanium-plated diamond particles is achieved. This results in a high-density, ultra-high thermal conductivity composite material with a stable thermal conductivity exceeding 700 W / (m·K). The process is innovative and suitable for industrial mass production.

[0005] According to a first aspect of the present invention, one or more embodiments of this application provide an SPS sintering process for a high thermal conductivity diamond / copper composite material, comprising the following steps: S1. Raw material pretreatment: Select at least one of three different particle sizes of single crystal diamond particles, namely 50-60 mesh, 80-100 mesh, and 100-120 mesh, and perform vacuum titanium plating treatment on each of them before mixing to obtain titanium-plated diamond; select 8-20μm graphene-modified copper powder for later use. S2. Solid dry powder mixing: Solid powdered acrylic resin BR118, solid powdered polyethylene glycol and graphene modified copper powder are uniformly mixed to obtain copper-based composite dry powder. S3. Nitrogen intermittent airflow suspension and dispersion: Add titanium-plated diamond to a sealed coating tank, introduce nitrogen to replace the air in the tank until the oxygen content is ≤0.1%, and use nitrogen airflow with a pressure of 0.2~0.4 MPa and an interval of 3~5s to intermittently purge, so that the titanium-plated diamond is suspended and dispersed in the sealed coating tank. S4. Atomized Coating: Copper-based composite dry powder is uniformly added to the suspended and dispersed titanium-plated diamond, while isopropanol is separately atomized and sprayed into a sealed coating tank through a high-pressure atomizing nozzle, so that the copper-based composite dry powder is uniformly coated on the surface of the titanium-plated diamond to obtain composite particles. S5. Vacuum low-temperature degreasing: Place the composite particles in a vacuum degreasing furnace, evacuate to a vacuum degree ≤500Pa, heat to 350-400℃ at a rate of 5-8℃ / min, and hold for 1-2 hours to degrease, and obtain degreased composite particles. S6, SPS sintering: After degreasing, the composite particles are loaded into a graphite mold. Under a vacuum or argon protective atmosphere, the sintering temperature is set to 850-950 ℃, the sintering pressure to 30-50 MPa, the heating rate to 100-300 ℃ / min, and the holding time to 3-5 min. The mixture is then cooled to room temperature in the furnace and demolded to obtain a high thermal conductivity diamond / copper composite material.

[0006] According to the above-described technical solution of the present invention, the following improvements can also be made: Preferably, in step S1, the titanium-plated diamond is graded by the following mass percentages: 70% for 50-60 mesh, 15% for 80-100 mesh, and 15% for 100-120 mesh.

[0007] Preferably, the graphene doping mass fraction in the graphene-modified copper powder is 0.5% to 0.8%.

[0008] Preferably, in step S2, the copper-based composite dry powder comprises, by mass percentage, 1.0% to 3.0% solid powdered acrylic resin BR118, 0.2% to 0.6% solid powdered polyethylene glycol, and the remainder is graphene-modified copper powder.

[0009] Preferably, the nitrogen intermittent gas flow suspension dispersion coating time in step S3 is 60–120 min.

[0010] Preferably, the atomization coating process in step S4 is repeated 5 to 10 times.

[0011] Preferably, the atomization coating process continues until the diamond weight gain ratio is 72% to 78%.

[0012] Preferably, in step S6, the inner wall of the graphite mold, the bottom surface of the upper punch, and the top surface of the lower punch are all covered with graphite paper with a thickness of 0.1 mm.

[0013] According to another aspect of the present invention, a high thermal conductivity diamond / copper composite material is provided, which is prepared by SPS sintering process of the high thermal conductivity diamond / copper composite material described in any one of the above claims, wherein the high thermal conductivity diamond / copper composite material has a thermal conductivity >700 W / (m·K) and a density ≥99%.

[0014] Preferably, the graphene-modified copper powder is tightly and uniformly coated on the surface of the titanium-plated diamond particles, forming a dense coating layer without exposed areas or agglomerations, and there is no obvious brittle reaction phase at the interface between the diamond and the copper matrix.

[0015] The beneficial effects of this invention are as follows: This invention provides a high thermal conductivity diamond / copper composite material and its SPS sintering process, which results in uniform and dense coating without exposure or agglomeration, significantly reducing porosity and interfacial thermal resistance; the solid additive dry powder is mixed and isopropanol is atomized separately, with precise proportions, thorough degreasing, and no residue; the titanium-plated interface + SPS rapid sintering inhibits the formation of brittle phases and provides excellent interfacial bonding; the thermal conductivity is stable >700W / (m·K), and the density is ≥99%; the process is simple, highly controllable, and suitable for industrial mass production. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the steps in an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0018] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in one or more embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] like Figure 1 As shown, an SPS sintering process for a high thermal conductivity diamond / copper composite material according to one or more embodiments of this application includes the following specific steps: S1. Raw material selection and pretreatment: Select single crystal diamond particles with particle sizes of 50-60 mesh, 80-100 mesh, and 100-120 mesh. Diamond particles of different particle sizes are treated with vacuum titanium plating process to make the surface of the diamond titanium plating layer uniform and controllable. The titanium layer transition enhances the interfacial bonding force between the diamond and the copper substrate, while isolating oxygen to prevent diamond oxidation in subsequent processes. The copper powder used is graphene-modified copper powder with a thickness of 8–20 μm, wherein the graphene doping mass fraction is 0.5%–0.8%. The thermal conductivity of this graphene copper powder is ≥420 W / (m·K). The graphene is uniformly dispersed inside the copper powder grains, which further optimizes the thermal conduction network of the composite material and improves the overall thermal conductivity.

[0020] S2. Solid dry powder mixing: Graphene-modified copper powder, solid acrylic resin BR118, and solid polyethylene glycol are uniformly mixed to obtain copper-based composite dry powder. By mass percentage: solid acrylic resin BR118: 1.0%~3.0%, solid polyethylene glycol: 0.2%~0.6%, and the balance is graphene-modified copper powder.

[0021] S3. Nitrogen-protected intermittent dispersion: The graded titanium-plated diamond particles are placed in a sealed encapsulated tank, and high-purity nitrogen is continuously introduced to replace the air in the tank until the oxygen content in the tank is ≤0.1%. The entire process is protected by an inert nitrogen atmosphere to prevent the oxidation of the raw materials. The process employs an intermittent airflow purging drive, with an airflow pressure of 0.2–0.4 MPa and an intermittent cycle of 3–5 seconds. The nitrogen airflow intermittently blows up the diamond particles in the can, causing them to move up and down in a reciprocating motion within the can, ensuring that the particles are completely dispersed without agglomeration or accumulation, thus laying the foundation for uniform coating.

[0022] S4. Isopropanol Independent Atomization Coating: Under nitrogen suspension and dispersion, copper-based composite dry powder is uniformly added into the coating tank, while isopropanol is separately atomized and sprayed into the tank through a high-pressure atomizing nozzle. Isopropyl alcohol wets the diamond surface and slightly dissolves solid acrylic resin and polyethylene glycol, forming a temporary adhesive liquid film that allows the copper-based composite dry powder to be uniformly and densely coated on the diamond surface.

[0023] Depending on the required coating thickness, repeat the feeding-atomization operation 5–10 times, control the diamond weight gain ratio to 72%–78%, and the total airflow dispersion coating time to 60–120 minutes.

[0024] S5. Vacuum Low-Temperature Degreasing: The alternately coated composite diamond particles are transferred to a vacuum degreasing furnace, and the vacuum is drawn to a vacuum degree ≤500 Pa. The temperature is increased to 350–400 ℃ at a heating rate of 5–8 ℃ / min, and held at this temperature for 1–2 h for vacuum degreasing treatment. This process completely removes organic components such as acrylic resin BR118, isopropanol, and polyethylene glycol. The entire degreasing process is carried out in a vacuum and oxygen-free environment to avoid oxidation of the particle surface. After degreasing, composite particles with a firm coating and no organic residue are obtained.

[0025] S6, SPS hot pressing sintering molding: mold pretreatment: select high-purity graphite mold, and evenly lay 0.1 mm thick high-purity graphite paper on the inner wall of the mold, the bottom surface of the upper punch, and the top surface of the lower punch. Loading: Flatten the vacuum-degreased composite granules into a graphite mold lined with graphite paper; Spark plasma (SPS) sintering: vacuum or argon protection, sintering temperature: 850–950℃, sintering pressure: 30–50MPa, heating rate: 100–300℃ / min, holding time: 3–5min; after sintering, cool to room temperature in the furnace and demold to obtain the high thermal conductivity diamond copper composite material product.

[0026] The following examples further illustrate the process and the properties of the composite materials obtained through this process: Example

[0027] Raw materials: Titanium-plated diamond gradation 50-60 mesh 70%, 80-100 mesh 15%, 100-120 mesh 15%; graphene-modified copper powder 15μm, graphene content 0.6%.

[0028] Copper-based composite dry powder: BR118 acrylic resin 2%, polyethylene glycol 0.4%, balance copper powder.

[0029] Nitrogen suspension: 0.3 MPa, intermittent 4 s, oxygen content ≤0.1%.

[0030] Coating: Dry powder feeding + isopropyl alcohol independent atomization, cycled 8 times, weight gain ratio 75%.

[0031] Degreasing: 300 Pa, 6 ℃ / min to 380 ℃, hold for 1.5 h.

[0032] Sintering: 900 ℃, 40 MPa, 200 ℃ / min, holding for 3 min.

[0033] Composite material properties: density 99.3%, thermal conductivity 728 W / (m·K). Example

[0034] Raw materials: Titanium-plated diamond gradation 50-60 mesh 70%, 80-100 mesh 15%, 100-120 mesh 15%; Graphene-modified copper powder 10μm, graphene content 0.5%.

[0035] Dry powder ratio: BR118 1.5%, PEG 0.3%.

[0036] After 6 cycles of coating, the weight gain was 73%.

[0037] Degreasing: 370 ℃, keep warm for 2 h.

[0038] Sintering: 920 ℃, 45 MPa, hold for 4 min.

[0039] Composite material properties: density 99.1%, thermal conductivity 716 W / (m·K). Example

[0040] Single-grid 50–60 mesh titanium-plated diamond.

[0041] Dry powder formulation: BR118 3%, PEG 0.6%.

[0042] After 10 cycles of coating, the weight gain was 78%.

[0043] Degreasing: 400 ℃, keep warm for 1 h.

[0044] Sintering: 950 ℃, 50 MPa, 300 ℃ / min, holding for 5 min.

[0045] Composite material properties: density 99.0%, thermal conductivity 702 W / (m·K).

[0046] As can be clearly seen from the above embodiments, this embodiment provides a high thermal conductivity diamond / copper composite material and its SPS sintering process. Through a nitrogen intermittent airflow suspension atomization coating process, combined with a special binder, inhibitor and diluent system, and combined with precise temperature control degreasing and SPS sintering, the uniform distribution of coarse-grained titanium-plated diamond particles is achieved, and a high-density, ultra-high thermal conductivity composite material is prepared. Its thermal conductivity stably exceeds 700 W / (m·K). The process is innovative and suitable for industrial mass production.

[0047] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0048] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A SPS sintering process for high thermal conductivity diamond / copper composite materials, characterized in that, Includes the following steps: S1. Raw material pretreatment: Select at least one of three different particle sizes of single crystal diamond particles, namely 50-60 mesh, 80-100 mesh, and 100-120 mesh, and perform vacuum titanium plating treatment on each of them before mixing to obtain titanium-plated diamond; select 8-20μm graphene-modified copper powder for later use. S2. Solid dry powder mixing: Solid powdered acrylic resin BR118, solid powdered polyethylene glycol and graphene modified copper powder are uniformly mixed to obtain copper-based composite dry powder. S3. Nitrogen intermittent airflow suspension and dispersion: Add titanium-plated diamond to a sealed coating tank, introduce nitrogen to replace the air in the tank until the oxygen content is ≤0.1%, and use nitrogen airflow with a pressure of 0.2~0.4 MPa and an interval of 3~5s to intermittently purge, so that the titanium-plated diamond is suspended and dispersed in the sealed coating tank. S4. Atomized Coating: Copper-based composite dry powder is uniformly added to the suspended and dispersed titanium-plated diamond, while isopropanol is separately atomized and sprayed into a sealed coating tank through a high-pressure atomizing nozzle, so that the copper-based composite dry powder is uniformly coated on the surface of the titanium-plated diamond to obtain composite particles. S5. Vacuum low-temperature degreasing: Place the composite particles in a vacuum degreasing furnace, evacuate to a vacuum degree ≤500Pa, heat to 350-400℃ at a rate of 5-8℃ / min, and hold for 1-2 hours to degrease, and obtain degreased composite particles. S6, SPS sintering: After degreasing, the composite particles are loaded into a graphite mold. Under a vacuum or argon protective atmosphere, the sintering temperature is set to 850-950 ℃, the sintering pressure to 30-50 MPa, the heating rate to 100-300 ℃ / min, and the holding time to 3-5 min. The mixture is then cooled to room temperature in the furnace and demolded to obtain a high thermal conductivity diamond / copper composite material.

2. The SPS sintering process for the high thermal conductivity diamond / copper composite material according to claim 1, characterized in that, In step S1, the titanium-plated diamonds are graded by the following mass percentages: 70% for 50-60 mesh, 15% for 80-100 mesh, and 15% for 100-120 mesh.

3. The SPS sintering process for the high thermal conductivity diamond / copper composite material according to claim 1, characterized in that, The graphene doping mass fraction in graphene-modified copper powder is 0.5% to 0.8%.

4. The SPS sintering process for the high thermal conductivity diamond / copper composite material according to claim 1, characterized in that, In step S2, the copper-based composite dry powder, by mass percentage, comprises 1.0% to 3.0% solid powdered acrylic resin BR118, 0.2% to 0.6% solid powdered polyethylene glycol, and the remainder is graphene-modified copper powder.

5. The SPS sintering process for the high thermal conductivity diamond / copper composite material according to claim 1, characterized in that, In step S3, the nitrogen intermittent gas flow suspension dispersion coating time is 60–120 min.

6. The SPS sintering process for the high thermal conductivity diamond / copper composite material according to claim 1, characterized in that, The atomization coating process in step S4 is repeated 5 to 10 times.

7. The SPS sintering process for the high thermal conductivity diamond / copper composite material according to claim 6, characterized in that, The atomization coating process continues until the diamond weight gain ratio reaches 72%–78%.

8. The SPS sintering process for the high thermal conductivity diamond / copper composite material according to claim 1, characterized in that, In step S6, 0.1 mm thick graphite paper is laid on the inner wall of the graphite mold, the bottom surface of the upper punch, and the top surface of the lower punch.

9. A high thermal conductivity diamond / copper composite material, characterized in that, The high thermal conductivity diamond / copper composite material is prepared by SPS sintering process according to any one of claims 1–8, wherein the high thermal conductivity diamond / copper composite material has a thermal conductivity > 700 W / (m·K) and a density ≥ 99%.

10. The high thermal conductivity diamond / copper composite material according to claim 9, characterized in that, The graphene-modified copper powder is tightly and uniformly coated on the surface of the titanium-plated diamond particles, forming a dense coating layer without any exposed areas or agglomerations. There is no obvious brittle reaction phase at the interface between the diamond and the copper matrix.

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