An integrated diamond copper fin heat sink and a preparation method thereof

Abstract

The application belongs to the field of heat dissipation materials, and discloses an integrated diamond copper fin heat sink and a preparation method thereof. The preparation method comprises the following steps: preparing a diamond copper tray with a diamond volume fraction of 60-70%, a diamond copper fin with a diamond volume fraction of 45-60%, and a diamond copper blank with a diamond volume fraction of 70-85%; providing a foamed copper mold with grooves, embedding the mold into the tray positioning step, and injecting Cu-based solder; embedding the fin into the groove, placing the blank at the bottom of the fin gap to obtain an assembly; installing a graphite limiting tool, sintering in an 850-950 ℃ normal pressure atmosphere furnace, and melting the foamed copper to make the components metallurgically combined, and the copper matrix remains solid. The application solves the problems of fin forming difficulty, high interface thermal resistance, high mass production cost and low machining yield in the preparation process of the existing diamond copper fin heat sink, realizes near-net forming of high aspect ratio fins, eliminates interface thermal resistance, and is suitable for batch production.

Description

Technical Field

[0001] This invention belongs to the field of heat dissipation material technology, and specifically discloses an integrated diamond copper fin heat sink and its preparation method. This invention adopts a split diamond copper prefabricated structure based on foam copper assembly and normal pressure atmosphere sintering to obtain a diamond copper fin heat sink, which can achieve rapid, low-cost, and mass production. Background Technology

[0002] Diamond-copper composite materials are considered a new generation of high-performance thermal management materials because they combine the high thermal conductivity and low coefficient of thermal expansion of diamond with the good electrical and thermal conductivity and ductility of copper. They are widely used in heat dissipation substrates and packaging shells of high-power electronic devices.

[0003] When finned structures are required, existing technologies mainly employ the following approach: metallized diamond particles are mixed with copper powder, pre-pressed to obtain a diamond-copper green blank, which is then placed in pre-drilled holes in a copper plate, covered with copper powder on both sides, and sintered to obtain a sandwich-structured heat dissipation substrate. However, the bonding strength between the upper and lower copper layers and the middle diamond-copper layer in this structure is poor, making it difficult to meet practical application requirements. Especially when heat dissipation devices with finned structures are needed, due to the complexity of the structure, existing methods cannot achieve one-time sintering. Typically, laser processing or CNC milling is used to machine the sintered diamond-copper block to form a fin array. However, diamond-copper material has high hardness and brittleness; during machining, thin-walled fins are prone to chipping, corner collapse, and micro-cracks, resulting in a machining yield generally below 60%, severe tool wear, low processing efficiency, and high costs. While laser processing can achieve complex shapes, it is time-consuming, expensive, and the metal vapors emitted during processing pose environmental and personal safety hazards. Furthermore, the processed fins often have a taper, making it difficult to meet the high precision requirements of downstream products for fin flow channels.

[0004] Furthermore, existing technologies using high-pressure melting or hot-pressing sintering to integrally form fin structures require pressures of tens to hundreds of megapascals and temperatures exceeding the melting point of copper (1083 °C). High temperature and high pressure not only lead to high equipment costs (millions of dollars), small single-batch sintering volumes, and difficulty in mass production, but also cause thin-walled fins to easily collapse under high pressure. At high temperatures, the complete melting of the copper substrate leads to fin collapse and bending, while diamond undergoes graphitization and agglomeration, severely reducing the material's thermal conductivity and mechanical properties. Although separate brazing solutions allow for the separate fabrication of the substrate and fins before connection, the brazing layer introduces additional interfacial thermal resistance, making delamination and separation highly likely during thermal cycling, resulting in poor long-term reliability.

[0005] Therefore, how to achieve high-yield, low-cost, and mass production of diamond copper fin structures, while eliminating interfacial thermal resistance and avoiding damage to material properties caused by high temperature and high pressure, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] One of the objectives of this invention is to solve the technical problems existing in the preparation of diamond copper fin structures, such as difficulty in fin forming, high interfacial thermal resistance, high mass production cost, and low machining yield.

[0007] Therefore, this invention provides an integrated diamond copper finned heat sink and its preparation method. The method includes a pre-sintered diamond copper billet with a high diamond volume fraction, and a diamond copper tray and diamond copper fins with high thermal conductivity prepared by melt infiltration. Precise positioning and assembly of the fins and tray are achieved through a foamed copper groove structure, and Cu-based solder is filled inside the foamed copper. During sintering, the copper substrate remains solid, and the foamed copper and Cu-based solder melt together to achieve a full metallurgical bond between the diamond copper fins, the diamond copper tray, and the diamond copper billet, thus obtaining an integrated diamond copper finned heat sink. This preparation method can significantly improve the fin forming yield (≥90%), eliminate interfacial contact thermal resistance, avoid damage to the material caused by high temperature and high pressure, and reduce the overall production cost by 40%–60%, making it suitable for heat dissipation applications in high-power electronic devices.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an integrated diamond copper finned heat sink, comprising the following steps: Step 1: Prepare diamond copper trays with a diamond volume fraction of 60%–70%, diamond copper fins with a diamond volume fraction of 45%–60%, and diamond copper blanks with a diamond volume fraction of 70%–85%. Step 2: Provide a foam copper mold, on which grooves are machined to correspond one-to-one with the diamond copper fins, and the depth of the grooves matches the embedding depth of the fins; Step 3: Place the grooved foam copper mold into the positioning step of the diamond copper tray, and inject Cu-based solder into the pores of the foam copper mold. Step 4: Insert the diamond copper fins one by one into the grooves of the foamed copper, and place the diamond copper blank at the bottom of the gap between the fins to obtain the assembly; Step 5: Install graphite limiting fixtures on the assembly; the graphite limiting fixtures include a bottom positioning base, a side fixing block and a top limiting pressure block, the top limiting pressure block is provided with limiting grooves that correspond one-to-one with the top of the fins, and the pressure block generates a micro pressure of 0.5 to 2 kPa due to its own weight. Step 6: Place the assembly with the graphite limiting fixture installed in an atmospheric furnace and sinter it at a temperature of 850-950 ℃. The foamed copper mold melts and the components are metallurgically bonded. During the sintering process, the copper matrix in the diamond copper tray, diamond copper fins and diamond copper billet remains solid, thus obtaining an integrated diamond copper finned heat sink.

[0009] A further improvement to the fabrication method of an integrated diamond copper finned heat sink: Preferably, the aspect ratio of the diamond copper fins is ≥10:1; the dimensions of the diamond copper blank are: length 0.3 mm to 200 mm, width 0.3 mm to 3 mm, and height 1 to 30 mm; the dimensions of the diamond copper tray are: length 50 mm to 200 mm, width 50 mm to 200 mm, and height 0.3 mm to 5 mm.

[0010] Preferably, the preparation method of the diamond copper tray, diamond copper fins and diamond copper blank in step one is as follows: Bimodal graded diamond is used as raw material, with a volume ratio of coarse particles to fine particles of 7:3, wherein the particle size of the coarse particles is 120-250 μm and the particle size of the fine particles is 10-20 μm; a metal layer of 30-100 nm is first deposited on the diamond surface to obtain metallized diamond with different diamond volume fractions; then the metallized diamond is uniformly mixed with a composite binder and dried, and then subjected to cold pressing molding and pressure melting to obtain the diamond copper tray, diamond copper fins and diamond copper blank.

[0011] Preferably, the material of the metal layer is selected from one or more of Ti, Ta, Cr, and Mo, and the deposition method is vacuum evaporation, electroplating, or physical vapor deposition.

[0012] Preferably, the metallized diamond and the composite binder are mixed at a mass ratio of 100:(2-4), and anhydrous ethanol is added as a dispersant. The composite binder is composed of polyethylene glycol (PEG) and polyvinyl alcohol (PVA), wherein the molecular weight of PEG is 4000 and the degree of polymerization of PVA is 1700. Anhydrous ethanol is added as a dispersant, and the mixture is uniformly mixed so that the binder uniformly coats the metallized diamond.

[0013] Preferably, the specific steps of the cold pressing molding and pressure melting are as follows: the metallized diamond, which is uniformly mixed with the composite binder and dried, is placed under a pressure of 150-250 MPa and held for 3-5 min to remove the binder; then it is placed in a high-purity graphite crucible, and a copper ingot is placed on top of the blank for pressure melting, wherein the process parameters are: reaction temperature 900-1200 ℃, heating rate: 5-10 ℃ / min, holding time 30-60 min, cooling rate 2 ℃ / min, cooling down to 800 ℃, and then naturally cooling to room temperature.

[0014] Preferably, the foam copper mold in step two is a low-melting-point alloy foam copper with a melting point ≤950 ℃, an alloy element content of 1-5 wt%, and an alloy composition of one or more of Ag, Ti, Sn, and Zn, a porosity of 85-90%, and a pore size of 400-600 μm; the groove depth accounts for 30%-50% of the total thickness of the foam copper.

[0015] Preferably, in step three, Cu-based solder, comprising 5-10% of the volume of the foamed copper mold, is injected into the pores of the foamed copper mold.

[0016] Preferably, the sintering in step six is ​​carried out under a flowing reducing atmosphere, wherein the reducing atmosphere is argon containing 1-3% hydrogen by volume and 0.1-0.5% methane by volume, with an oxygen content ≤5ppm and a flow rate of 1-2L / min.

[0017] The second objective of this invention is to provide an integrated diamond copper finned heat sink prepared by the above-described method, which structurally comprises: Diamond copper tray; The diamond copper fins are arranged in an array, with multiple diamond copper fins arranged in parallel and spaced apart, and their roots are embedded in the upper surface of the diamond copper tray. The diamond copper blank is set at the bottom of the gap between adjacent diamond copper fins. The side surface is bonded to the side surface of the adjacent fins through a continuous atomic-level metallurgical copper layer, and the lower surface is bonded to the upper surface of the diamond copper tray through a continuous atomic-level metallurgical copper layer. The diamond volume fraction of the diamond copper tray is 60% to 70%, the diamond volume fraction of the fins is 45% to 60%, and the diamond volume fraction of the diamond copper blank is 70% to 85%.

[0018] Existing melt infiltration methods can only prepare simple bulk materials and cannot directly form fin structures; hot pressing methods easily crush thin-walled fins; and separate brazing presents thermal resistance at heterogeneous interfaces. This invention addresses these problems by making systematic innovations in the design, positioning, assembly, and control of the diamond copper tray, diamond copper fins, and diamond copper blank, as well as in low-temperature sintering.

[0019] First, diamond copper trays with a diamond volume fraction of 60%–70%, diamond copper fins with a diamond volume fraction of 45%–60%, and diamond copper blanks with a diamond volume fraction of 70%–85% were prepared using a melt infiltration method. By prefabricating in zones and independently controlling the diamond volume fraction in each zone, the diamond copper trays were made to have high thermal conductivity and low expansion characteristics to match the chip, the diamond copper fins had high toughness to resist brittle fracture, and the diamond copper blanks had extreme thermal conductivity to achieve lateral heat expansion, thereby achieving spatial synergy between thermophysical and mechanical properties at the material level.

[0020] Secondly, a foamed copper mold with grooves is provided, with each groove corresponding to a diamond copper fin and its depth matching the fin embedding depth. The foamed copper mold is nested within the positioning step of the diamond copper tray, and Cu-based solder is injected. Then, the diamond copper fins are embedded one by one into the grooves, and the diamond copper blank is placed at the bottom of the fin gaps. The foamed copper mold achieves precise pre-positioning of the fin array, and its porous structure generates capillary force during subsequent sintering, driving the molten solder to fill all interface gaps without dead angles, ensuring that the interfaces are fully wetted and filled.

[0021] Next, a graphite positioning fixture consisting of a bottom positioning base, side fixing blocks, and a top limiting pressure block is installed on the assembly. A shrinkage gap is reserved between the side fixing blocks and the assembly, allowing for positioning without applying pressure, thus enabling free shrinkage during sintering without generating constraint stress. The top limiting pressure block has limiting grooves corresponding to the tips of the fins, applying a micro-pressure of 0.5–2 kPa solely by its own weight. This pressure is far below the crushing critical value of thin-walled fins, serving only to prevent the fins from floating or collapsing. High-purity isostatic graphite, with a thermal expansion coefficient matching that of diamond-copper, is selected as the fixture material to avoid structural damage caused by deformation differences during heating.

[0022] Finally, the assembly with the graphite limiting fixture installed is placed in an atmospheric furnace and sintered at 850–950°C without pressure. This temperature is far below the melting point of pure copper (1083°C). The copper matrix in the diamond copper preform remains solid throughout the process, providing rigid support for the fins and preventing deformation and collapse caused by high-temperature full melting. The foamed copper mold and Cu-based solder partially melt and uniformly fill the interface under capillary force. After cooling, they form a continuous atomic-level metallurgical bond with the copper matrix and diamond. This achieves near-net-shape forming of high aspect ratio fins without high pressure, while eliminating heterogeneous brazing interfaces and realizing uninterrupted heat conduction throughout the entire path from the chip to the fin tip.

[0023] The advantages of this invention compared to the prior art are as follows: 1. This invention provides a method for preparing an integrated diamond copper finned heat sink. The method involves preparing diamond copper trays, diamond copper fins, and diamond copper blanks with different diamond volume fractions using a melt infiltration method. A foamed copper mold with grooves corresponding to the fins is provided. The fin preforms are fitted into the grooves, and the diamond copper blanks are placed at the bottom of the fin gaps. A graphite positioning fixture consisting of a bottom positioning base, side fixing blocks, and a top limiting pressure block is installed. A sintering shrinkage gap of 0.1–0.2 mm is reserved between the side fixing blocks and the assembly. The top limiting pressure block applies a micro-pressure of 0.5–2 kPa based solely on its own weight. The heat sink is then sintered at low temperature (850–950°C) in an atmospheric furnace. These steps, working together as a whole, solve the problems of difficult fin forming, high interfacial thermal resistance, high mass production cost, and low machining yield. Specifically: (1) High yield and high precision. No high-pressure sintering and subsequent precision machining are required, which completely avoids structural collapse and cracking. For fins with high aspect ratio, the sintering yield is increased from less than 60% with existing machining to more than 90%, and the dimensional qualification rate is close to 100%. High-density fin arrays with feature size less than 0.5mm can be prepared.

[0024] (2) No damage to material properties. The sintering temperature is controlled below 950℃, far below the melting point of pure copper (1083℃). The copper matrix in the diamond copper preform remains solid throughout the process, and there is no problem of diamond floating or agglomeration. At the same time, the lower temperature, combined with the isolation protection of the PVD gradient coating and the methane carbon-controlling atmosphere, inhibits the carbon dissolution reaction, graphitization and oxidation of diamond from both thermodynamic and kinetic mechanisms. After sintering, the density is ≥98%, the atomic-level metallurgical copper layer is continuous and uniform, the thickness is 1~5μm, and there are no voids, cracks and debonding at the interface.

[0025] (3) Equipment and production costs are significantly reduced. Only a regular atmospheric furnace is needed, and the equipment cost is 1 / 5 to 1 / 10 of that of hot pressing or discharge plasma sintering equipment. Energy consumption per batch is reduced by more than 60%, the overall production cost is reduced by 40% to 60%, and the processing cost of a single product is reduced by more than 60%.

[0026] (4) Mass production capacity is greatly improved. No expensive high-pressure equipment is required. The furnace can be designed for large size, supporting batch sintering of multiple workpieces. It can also be adapted to pusher kiln and mesh belt kiln to achieve continuous production. The mass production capacity is more than 10 times higher than that of hot pressing process.

[0027] (5) Shortened R&D and production cycle. Only the foamed copper groove mold and graphite limiting tooling need to be replaced to adapt to different fin structures. No special tools and processing programs are required, and the R&D and production cycle is shortened by more than 70%.

[0028] (6) Breaking through technological biases and realizing industrial-scale application. This invention breaks through the bottleneck that diamond copper heat sinks have long relied on high-end customization and are difficult to promote in civilian use, enabling them to be applied on a large scale to the thermal management of high-power electronic devices in civilian industrial fields, and providing a low-cost, mass-producible solution for solving the heat dissipation problem of high heat flux density devices.

[0029] 2. This invention provides an integrated diamond copper finned heat sink, comprising a diamond copper tray, a diamond copper blank, and diamond copper fins. The diamond volume fraction of the diamond copper tray is 60%–70%, the diamond volume fraction of the fins is 45%–60%, and the diamond volume fraction of the diamond copper blank is 70%–85%. The diamond copper tray, diamond copper blank, and fins are bonded together by copper phase melting and recrystallization to form a continuous atomic-level metallurgical bond, without any brazing or bonding interfaces. Based on the above structure, this heat sink has the following beneficial effects: (1) Eliminate interfacial thermal resistance and adapt to heat flux density of ≥500W / cm². The fin root is completely embedded in the diamond copper blank and forms a continuous atomic-level metallurgical bonding path with the diamond copper tray. There is no heterogeneous brazing interface as in traditional split brazing schemes, which eliminates the risk of contact thermal resistance and thermal cycle debonding from the source.

[0030] (2) Achieve gradient performance customization, taking into account both thermal conductivity and toughness. The diamond copper tray uses 60% to 70% diamond volume fraction to obtain high lateral thermal conductivity and low thermal expansion coefficient matching the chip; the fins use 45% to 60% diamond volume fraction, which improves structural toughness while maintaining high thermal conductivity and avoids brittle fracture of fins caused by a single high volume fraction formula; the 70% to 85% diamond copper blank filling the gaps between the fins further enhances the overall thermal conductivity.

[0031] (3) High product consistency and service reliability. The sintering process is completed in a uniform temperature and atmosphere field, eliminating the pressure field unevenness problem of hot pressing. The density and interfacial bonding force of the entire workpiece are uniform and consistent, and the performance fluctuation during mass production can be controlled within 5%. The porous structure of the foamed copper skeleton can buffer the thermal expansion mismatch stress during sintering and service, preventing interface cracking; the perpendicularity and dimensional tolerance of the finished fins can be controlled within ±0.02 mm, possessing mechanical and thermal reliability for long-term service. Attached Figure Description

[0032] Figure 1 This is a structural diagram of the diamond copper tray and the foam copper mold nested together in step three of embodiments 2 to 5 of the present invention.

[0033] Figure 2 This is a structural diagram of step three in embodiments 2-5 of the present invention, after the diamond copper tray and the foam copper mold are nested and solder is injected.

[0034] Figure 3 This is a structural diagram of the assembled diamond copper fins, diamond copper blank, and foam copper mold in step four of embodiments 2-5 of the present invention.

[0035] Figure 4This is a structural diagram of the assembly after installing the graphite limiting fixture on the assembly in step five of embodiments 2 to 5 of the present invention.

[0036] Figure 5 This is a structural diagram of the integrated diamond copper fin heat sink of the present invention.

[0037] The markings in the attached diagram have the following meanings: 1. Diamond copper tray; 2. Diamond copper fins; 3. Diamond copper billet; 4. Foam copper mold; 5. Solder; 6. Graphite limiting fixture; 61. Bottom positioning base; 62. Side fixing block; 63. Top limiting pressure block; 7. Metallurgical copper layer. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0039] Example 1 This embodiment provides an integrated diamond copper finned heat sink, the structure of which is as follows: Figure 5 As shown, its composition includes a diamond copper tray 1, diamond copper fins 2, a diamond copper blank 3, and a metallurgical copper layer 7.

[0040] The diamond copper tray 1 is flat and contains 60% to 70% diamond by volume. Its dimensions are 50 mm to 200 mm in length, 50 mm to 200 mm in width, and 0.3 to 5 mm in height.

[0041] Multiple diamond copper fins 2 are arranged in parallel and spaced apart, with the root of the fin embedded in the upper surface of the diamond copper tray 1; the volume fraction of diamond contained is 45% to 60%, and the aspect ratio is ≥10:1.

[0042] A diamond-copper billet 3 is disposed at the bottom of the gap between adjacent diamond-copper fins 2. Its side surface is bonded to the side surface of the adjacent fins by a continuous atomic-level metallurgical copper layer 7, and its lower surface is bonded to the upper surface of the diamond-copper tray 1 by a continuous atomic-level metallurgical copper layer 7. The thickness of the metallurgical copper layer 7 is 1–5 μm. The diamond volume fraction in the diamond-copper billet 3 is 70%–85%, and its dimensions are 0.3 mm–200 mm in length, 0.3 mm–3 mm in width, and 1–30 mm in height. Its width matches the spacing between adjacent fins.

[0043] Examples 2-5 Examples 2-5 provide a method for preparing an integrated diamond copper finned heat sink, comprising the following steps: Step 1: Preparation of diamond copper trays, diamond copper fins, and diamond copper blanks: Bimodal graded diamond was used as the raw material, with a coarse-to-fine particle volume ratio of 7:3. The coarse particles had a diameter of 120–250 μm, and the fine particles had a diameter of 10–20 μm. A metal layer with a thickness of 30–100 nm was deposited on the diamond surface to obtain metallized diamond. The metal layer material was selected from one or more of Ti, Ta, Cr, and Mo, and the deposition method was vacuum evaporation, electroplating, or physical vapor deposition.

[0044] Metallized diamond and composite binder were mixed at a mass ratio of 100:(2-4), with anhydrous ethanol added as a dispersant. The mixture was ball-milled and then dried. The composite binder consisted of PEG and PVA, with PEG having a molecular weight of 4000 and PVA having a degree of polymerization of 1700. The dried mixture was then cold-pressed at 150-250 MPa for 3-5 min to obtain diamond copper tray preforms, diamond copper fin preforms, and diamond copper billet preforms, with diamond volume fractions of 60%-70%, 45%-60%, and 70%-85%, respectively.

[0045] The aforementioned preforms were placed in high-purity graphite crucibles, with copper ingots of ≥99.99% purity placed on top. Pressure melting and infiltration were performed at 900–1200℃, held for 30–60 min, with a heating rate of 5–10℃ / min and a cooling rate of 2℃ / min. After cooling to 800℃, the mixture was allowed to cool naturally in the furnace, sequentially producing a diamond copper tray, diamond copper fins, and a diamond copper billet. The dimensions of the diamond copper tray are: length 50mm–200mm, width 50mm–200mm, height 0.3–5mm, and a bearing area depth of 0.1–3mm. The diamond copper fins are rectangular sheets with an aspect ratio ≥10:1 and a length of 0.3–200 mm. The size of the diamond copper billet is adapted to the enclosing area of ​​adjacent diamond copper fins and the foam copper mold, with dimensions of: length 0.3mm–200mm, width 0.3mm–3mm, and height 1–30mm.

[0046] Step 2: Provide the foam copper mold: Low-melting-point alloy foam copper with a melting point ≤950℃ is selected, and its dimensions are adapted to the dimensions of the diamond copper tray's bearing area. Its alloy element content is 1–5 wt%, and the alloy composition is one or more of Ag, Ti, Sn, and Zn. The porosity of the foam copper is 85%–90%, and the pore size is 400–600 μm. Grooves corresponding to the diamond copper fins are machined into the foam copper. The single-sided gap between the groove and the fin is 0.05±0.02 mm, the groove depth accounts for 30%–50% of the total thickness of the foam copper, the positional tolerance is ±0.05 mm, and the flatness is ≤0.02 mm. After pickling to remove oxidation and vacuum drying, the foam copper mold is obtained.

[0047] Step 3: Foam copper mold nesting and solder injection: The diamond copper tray and foam copper mold are sandblasted, then ultrasonically cleaned with anhydrous ethanol for 10–30 minutes. The grooved foam copper mold is then nested into the positioning step of the diamond copper tray (e.g., ...). Figure 1 (As shown). Then, inject 5%–10% Cu-based solder, comprising the volume of the foamed copper mold, into the pores of the foamed copper mold, such as… Figure 2 As shown.

[0048] Step 4: Fin Fitting and Assembly: Diamond copper fins are individually embedded into the grooves of a foam copper mold, with the height difference between the fin tips ≤ 0.02 mm; a diamond copper blank is placed at the bottom of the fin gap to obtain the assembly, such as... Figure 3 As shown.

[0049] Step 5: Install the graphite limit fixture: A graphite limiting fixture is fabricated using high-purity isostatic graphite. The fixture includes a bottom positioning base, side fixing blocks, and a top limiting pressure block. It is calcined at 1000℃ for 2 hours in a vacuum environment and then cooled for later use. The top limiting pressure block has limiting grooves that correspond one-to-one with the top tips of the fins.

[0050] Place the assembly into the bottom positioning base, leaving a sintering shrinkage gap of 0.1–0.2 mm between the side fixing block and one side of the assembly. The top limiting pressure block applies a slight pressure of 0.5–2 kPa solely by its own weight. Figure 4 As shown.

[0051] Step Six: Sintering at atmospheric pressure: The assembly with the graphite limiting fixture installed is placed in an atmospheric furnace and pressurelessly sintered at 850–950°C under a flowing reducing atmosphere. The reducing atmosphere is argon containing 1%–3% hydrogen and 0.1%–0.5% methane by volume, with an oxygen content ≤5 ppm and a flow rate of 1–2 L / min.

[0052] During the sintering process, the copper matrix in the diamond copper tray, diamond copper fins, and diamond copper billet remains solid. After the foamed copper melts with the Cu-based solder, a full metallurgical bond is achieved between the diamond copper fins, the diamond copper tray, and the diamond copper billet, resulting in an integrated diamond copper finned heat sink. Figure 5 As shown. The density after sintering is ≥98%, and the thickness of the TiC transition layer at the interface is 1~5μm. The fin perpendicularity tolerance was tested to be ≤±0.02mm.

[0053] The specific process parameters for each step in the preparation processes of Examples 2-5 are shown in Table 1 below: Table 1. Specific process parameters for each step in Examples 2-5

[0054] Performance testing

[0055] The thermal conductivity of the integrated diamond copper finned heat sinks prepared in Examples 2-5 was tested. The specific testing procedure was as follows: Following the standard GB / T 22588-2008 "Measurement of Thermal Diffusion Coefficient or Thermal Conductivity by Flash Method", a laser flash thermal conductivity tester was used, and the tests were conducted at room temperature (25℃) under an argon protective atmosphere. Standard test samples of Φ10mm×1mm were cut from the diamond copper tray and copper fin areas of the integrated heat sink. Before testing, both sides of the samples were precisely polished and uniformly coated with a graphite coating to ensure consistent laser absorption. Three sets of samples were tested in parallel for each area. The thermal diffusion coefficient and specific heat capacity at constant pressure were collected. The thermal conductivity value was calculated by combining the measured density of the samples, and the arithmetic mean was taken as the thermal conductivity result for the corresponding area. The test data are shown in Table 2 below.

[0056] Table 2. Thermal conductivity test results of the integrated diamond copper fins prepared in Examples 2-5

[0057] The test data shows that the integrated diamond copper finned heat sinks prepared in Examples 2-5 have a stable thermal conductivity of 610-650 W / (m²) for the tray (diamond copper). The thermal conductivity of the finned area is consistently between 605 and 630 W / (m·K), indicating an extremely high level of thermal conductivity. The difference in thermal conductivity between the tray and the fins is only 5 to 20 W / (m·K), demonstrating excellent matching of their thermal conductivity properties. This indicates extremely low thermal resistance at the interface formed by the metallurgical bonding layer, allowing heat to be efficiently and evenly conducted from the ceramic tray to the fin side. This completely avoids the problems of high interface contact thermal resistance and prominent heat transfer bottlenecks found in traditional assembled and bonded heat sinks. The high thermal conductivity diamond ceramic tray can quickly diffuse the concentrated heat generated by power devices laterally and conduct it longitudinally to the fin structure. Combined with the efficient convection heat transfer of the fins, the overall heat dissipation capacity is significantly better than traditional silicon nitride and alumina ceramic-based copper finned heat sinks, effectively overcoming the high-density heat dissipation bottleneck of high-power third-generation semiconductor devices.

[0058] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing an integrated diamond copper finned heat sink, characterized in that, Includes the following steps: Step 1: Prepare diamond copper trays with a diamond volume fraction of 60%–70%, diamond copper fins with a diamond volume fraction of 45%–60%, and diamond copper blanks with a diamond volume fraction of 70%–85%. Step 2: Provide a foam copper mold, on which grooves are machined to correspond one-to-one with the diamond copper fins, and the depth of the grooves matches the embedding depth of the fins; Step 3: Place the grooved foam copper mold into the positioning step of the diamond copper tray, and inject Cu-based solder into the pores of the foam copper mold. Step 4: Insert the diamond copper fins one by one into the grooves of the foamed copper, and place the diamond copper blank at the bottom of the gap between the fins to obtain the assembly; Step 5: Install graphite limiting fixtures on the assembly; the graphite limiting fixtures include a bottom positioning base, a side fixing block and a top limiting pressure block, the top limiting pressure block is provided with limiting grooves that correspond one-to-one with the top of the fins, and the pressure block generates a micro pressure of 0.5 to 2 kPa due to its own weight. Step 6: Place the assembly with the graphite limiting fixture installed in an atmospheric furnace and sinter it at a temperature of 850-950 ℃. The foamed copper mold melts and the components are metallurgically bonded. During the sintering process, the copper matrix in the diamond copper tray, diamond copper fins and diamond copper billet remains solid, thus obtaining an integrated diamond copper finned heat sink.

2. The method for preparing the integrated diamond copper finned heat sink according to claim 1, characterized in that, The aspect ratio of the diamond copper fins is ≥10:1; the dimensions of the diamond copper blank are: length 0.3 mm to 200 mm, width 0.3 mm to 3 mm, and height 1 to 30 mm; the dimensions of the diamond copper tray are: length 50 mm to 200 mm, width 50 mm to 200 mm, and height 0.3 mm to 5 mm.

3. The method for preparing the integrated diamond copper finned heat sink according to claim 1, characterized in that, The preparation methods of diamond copper trays, diamond copper fins, and diamond copper blanks in step one are as follows: Bimodal graded diamond is used as raw material, with a volume ratio of coarse to fine particles of 7:3, wherein the particle size of coarse particles is 120-250 μm and the particle size of fine particles is 10-20 μm; a metal layer of 30-100 nm is first deposited on the diamond surface to obtain metallized diamonds with different diamond volume fractions; then the metallized diamonds are uniformly mixed with a composite binder and dried, and then subjected to cold pressing molding and pressure melting to obtain diamond copper trays, diamond copper fins, and diamond copper blanks.

4. The method for preparing the integrated diamond copper finned heat sink according to claim 3, characterized in that, The material of the metal layer is selected from one or more of Ti, Ta, Cr, and Mo, and the deposition method is vacuum evaporation, electroplating, or physical vapor deposition.

5. The method for preparing the integrated diamond copper finned heat sink according to claim 3, characterized in that, The metallized diamond and the composite binder are mixed at a mass ratio of 100:(2-4), and anhydrous ethanol is added as a dispersant. The composite binder is composed of polyethylene glycol (PEG) and polyvinyl alcohol (PVA), wherein the molecular weight of PEG is 4000 and the degree of polymerization of PVA is 1700. Anhydrous ethanol is added as a dispersant, and the mixture is uniformly mixed so that the binder uniformly coats the metallized diamond.

6. The method for preparing the integrated diamond copper finned heat sink according to claim 3 or 5, characterized in that, The specific steps of the cooling pressing and pressure melting are as follows: the metallized diamond, which is uniformly mixed with the composite binder and dried, is placed under a pressure of 150-250 MPa and held for 3-5 minutes to remove the binder; then it is placed in a high-purity graphite crucible, and a copper ingot is placed on top of the blank for pressure melting. The process parameters are: reaction temperature 900-1200 ℃, heating rate: 5-10 ℃ / min, holding time 30-60 min, cooling rate 2 ℃ / min, cooling down to 800 ℃, and then naturally cooling to room temperature.

7. The method for preparing the integrated diamond copper finned heat sink according to claim 1, characterized in that, The foam copper mold mentioned in step two is a low-melting-point alloy foam copper with a melting point ≤950 ℃, an alloy element content of 1~5 wt%, and an alloy composition of one or more of Ag, Ti, Sn, and Zn. The porosity is 85~90%, and the pore size is 400~600 μm. The groove depth accounts for 30%~50% of the total thickness of the foam copper.

8. The method for preparing the integrated diamond copper finned heat sink according to claim 1, characterized in that, In step three, Cu-based solder, accounting for 5-10% of the volume of the foam copper mold, is injected into the pores of the foam copper mold.

9. The method for preparing the integrated diamond copper finned heat sink according to claim 1, characterized in that, The sintering described in step six is ​​carried out under a flowing reducing atmosphere, which is argon containing 1-3% hydrogen by volume and 0.1-0.5% methane by volume, with an oxygen content ≤5ppm and a flow rate of 1-2 L / min.

10. An integrated diamond copper finned heat sink prepared by the preparation method according to any one of claims 1 to 9, characterized in that, Structurally, it includes: Diamond copper tray; The diamond copper fins are arranged in an array, with multiple diamond copper fins arranged in parallel and spaced apart, and their roots are embedded in the upper surface of the diamond copper tray. The diamond copper blank is set at the bottom of the gap between adjacent diamond copper fins. The side surface is bonded to the side surface of the adjacent fins through a continuous atomic-level metallurgical copper layer, and the lower surface is bonded to the upper surface of the diamond copper tray through a continuous atomic-level metallurgical copper layer. The diamond volume fraction of the diamond copper tray is 60% to 70%, the diamond volume fraction of the fins is 45% to 60%, and the diamond volume fraction of the diamond copper blank is 70% to 85%.

Images