Diamond / copper composite material, and preparation method and application thereof

Abstract

The present application relates to the technical field of heat management materials, and particularly relates to a diamond / copper composite material and a preparation method and application thereof. The preparation method comprises the following steps: filling gaps between arranged diamond single crystal particles with copper alloy powder to sinter a preform; removing part of the copper alloy connecting layer to form a filling gap; depositing a composite heat conduction layer formed by co-deposition of copper atoms and diamond micro powder in the filling gap, so that the upper surface of the composite heat conduction layer is lower than the upper surface of the diamond single crystal particles to form a groove structure. The present application reduces the interfacial thermal resistance by constructing a composite heat conduction layer, and relieves the thermal expansion mismatch through the groove structure.

Description

Technical Field

[0001] This invention relates to the field of thermal management materials technology, specifically to a diamond / copper composite material, its preparation method, and its application. Background Technology

[0002] Diamond / copper composites are thermal management materials that use diamond as a high thermal conductivity reinforcing phase and copper as the matrix. Diamond has high thermal conductivity (its single-crystal thermal conductivity can reach 1000-2200 W / m·K), while copper has good thermal conductivity (approximately 400 W / m·K), electrical conductivity, and processability. By combining diamond and copper, the high thermal conductivity of diamond can be fully utilized, and the copper-based material connects and supports the diamond, thus obtaining a composite material with high thermal conductivity. Therefore, diamond / copper composites are beginning to be used in high-power electronic devices, chip packaging, and heat sinks.

[0003] With the development of artificial intelligence computing power, 5G communication, new energy vehicles, and third-generation semiconductors, the power density of electronic devices is constantly increasing, placing higher demands on the thermal conductivity and heat transfer efficiency of heat dissipation materials. Compared with traditional heat dissipation materials such as copper and aluminum, diamond / copper composites have higher thermal conductivity potential. However, in the actual preparation process, the interfacial bonding between diamond and copper, as well as the spatial arrangement of diamond particles, have a significant impact on the overall thermal conductivity of the composite material.

[0004] On the one hand, the interfacial bonding performance between diamond and copper is poor. Due to the significant differences in crystal structure and interfacial properties between diamond and copper, the wettability between them is poor. Without interfacial treatment, it is difficult for copper materials to form a good bonding interface on the diamond surface. When diamond particles are directly composited with a copper matrix, a large interfacial thermal resistance is easily formed between diamond and copper, making it difficult for heat to be efficiently transferred from diamond to the adjacent copper phase or diamond particles, thus limiting the high thermal conductivity of diamond.

[0005] To address the aforementioned issues, existing technologies typically employ methods such as diamond surface modification or copper matrix alloying to improve the interfacial bonding between diamond and copper. For example, a coating containing elements such as Ti, Cr, and W can be formed on the diamond surface to improve the interfacial bonding between diamond and copper by forming transition phases such as carbides; alternatively, active elements such as Cr, Ti, and Zr can be added to the copper matrix to improve the wettability of copper to diamond. However, when using copper matrix alloying, the introduction of alloying elements may increase carrier scattering, thereby reducing the thermal conductivity of the copper matrix; while diamond surface coating can improve interfacial bonding, an additional interfacial layer still exists between diamond and copper, which may still generate significant interfacial thermal resistance during heat transfer.

[0006] On the other hand, in composite materials using diamond particles as a high thermal conductivity phase, the spatial distribution of diamond particles within the copper matrix also affects heat transfer efficiency. In existing particle-reinforced diamond / copper composites, diamond particles are typically distributed discretely within the copper matrix or arranged in a specific pattern to form a diamond particle layer. When the diamond particles are discretely distributed, heat transfer along a predetermined direction requires repeated heat transfer between multiple diamond particles and the copper matrix, causing heat flow to pass through the diamond / copper interface multiple times. This increases interfacial thermal resistance and makes it difficult to fully utilize the high thermal conductivity of the diamond particles themselves.

[0007] To improve the alignment of diamond particles, existing technologies have attempted to arrange diamond particles according to a certain rule and then connect the arranged diamond particles using copper. For example, Chinese invention patent CN121538604A discloses a diamond-copper composite material for heat dissipation in electronic packaging and its preparation method. This method uses a vibrating screen and adhesive to arrange diamond particles regularly on a substrate, and then forms the composite material by magnetron sputtering and electroplating to thicken the copper layer. This method can improve the alignment of diamond particles on the substrate surface, but the gaps between adjacent diamond particles are mainly filled by the subsequently deposited copper layer, with copper serving as the primary heat conduction bonding medium between the diamond particles.

[0008] Furthermore, in composite structures using copper or copper alloys as the bonding material for diamond particles, the bonding region between the diamond particles is typically composed of copper or copper alloys. While pure copper has high thermal conductivity, its high melting point makes it prone to diamond graphitization during high-temperature sintering. Using copper alloys containing active elements can lower the preparation temperature, but the addition of alloying elements may reduce the thermal conductivity of the bonding layer. Therefore, ensuring reliable bonding between adjacent diamond particles while minimizing the impact of the bonding region on heat transfer and further improving the effective thermal conductivity between diamond particles are key issues that need to be addressed to improve the overall thermal conductivity of diamond / copper composites. Summary of the Invention

[0009] This invention provides a diamond / copper composite material, its preparation method, and its application, to solve the technical problems of poor interfacial wettability and high interfacial thermal resistance in existing diamond / copper composite materials.

[0010] To achieve the above objectives, this application provides the following technical solution: The first aspect of this application provides a method for preparing a diamond / copper composite material, comprising the following steps: After arranging multiple diamond single crystal particles, copper alloy powder is filled in the gaps between adjacent particles, and the copper alloy powder is solidified by sintering to form a preform of diamond-copper alloy bonding layer. Next, part of the copper alloy bonding layer in the preform is removed to create gaps between adjacent diamond particles. Finally, a deposition method is used to deposit a composite thermally conductive layer formed by the co-deposition of copper atoms and diamond micropowder in the gaps, which consolidates adjacent diamond single crystal particles into one; and the upper surface of the composite thermally conductive layer is lower than the upper surface of the diamond single crystal particles to form a groove structure.

[0011] Diamond / copper composites face the dual challenges of thermal expansion matching and post-processing in practical applications. The significant difference in the coefficient of thermal expansion between diamond (approximately 1.0 ppm / ℃) and copper (approximately 16.5 ppm / ℃) leads to thermal stress at the interface during the thermal cycling process of the chip. In severe cases, this can even cause the chip to be lifted, creating air gaps at the interface and drastically increasing the interfacial thermal resistance. Simultaneously, the large difference in hardness between diamond (Mohs hardness 10) and copper makes it difficult to remove grinding debris and causes significant heat accumulation during polishing, resulting in compromised surface quality and processing yield. Incorporating a groove structure on the upper surface of the diamond / copper composite can solve these technical problems.

[0012] In one embodiment of this application, the portion of the copper alloy bonding layer in the preform is removed by electrical discharge machining or electrochemical machining. Of course, the removal method can also be laser processing or chemical etching, etc.

[0013] In one embodiment of this application, the groove structure is formed by at least one of the following methods: (a) During the deposition process, the deposition amount is controlled so that the upper surface of the composite thermal conductive layer is lower than the upper surface of the diamond single crystal particles; (b) After the composite thermal conductive layer is deposited and the upper surface of the composite thermal conductive layer is not lower than the upper surface of the diamond single crystal particle, part of the composite thermal conductive layer is removed by grinding or polishing so that the upper surface of the composite thermal conductive layer is lower than the upper surface of the diamond single crystal particle.

[0014] In one embodiment of this application, the diamond particles are not less than 0.5 mm.

[0015] Preferably, the diamond particles are 0.5-1 mm in size. Within this particle size range, single-crystal diamond particles can balance the feasibility of a tightly packed monolayer arrangement with their own thermal conductivity. If the diamond particle size is less than 0.5 mm, during the monolayer arrangement process, due to the influence of surface energy and the effect of small size, the particles are prone to agglomeration or disordered stacking, making it difficult to form a stable monolayer ordered structure, thereby destroying the expected continuous thermal conductivity channels within the layer. If the diamond particle size is greater than 1 mm, the number of particles that can be arranged in the same planar area is limited, resulting in a decrease in the volume fraction of diamond in the composite material, reducing the effective proportion of the high thermal conductivity phase, which is not conducive to improving the overall thermal conductivity; moreover, the cost will also increase significantly.

[0016] Controlling the diamond particle size between 0.5mm and 1mm, such as selecting particles of 0.6mm, 0.7mm, 0.8mm, or 0.9mm, ensures that each particle has a sufficiently large single-particle thermal conductivity cross-section while utilizing appropriate interparticle spacing to accommodate the subsequent composite thermal conductivity layer. This particle size range facilitates the formation of a flat and dense diamond particle array through methods such as vibration-guided close-packing or template-guided alignment. This ensures efficient heat conduction between adjacent diamond single crystal particles through the filled composite thermal conductivity layer, thereby optimizing the overall thermal conductivity of the composite material.

[0017] In one embodiment of this application, the depth of the groove structure is 10 μm-50 μm. Preferably, the depth of the groove is 25 μm.

[0018] The depth of the groove structure is a key geometric parameter that determines the thermal stress relief capability and structural stability of the composite material during service. When the groove depth is too small, for example, less than 10 μm, the reserved space is insufficient to fully absorb the relative displacement between the diamond single crystal particles and the composite heat-conducting layer caused by the difference in thermal expansion coefficients. During thermal cycling, the composite heat-conducting layer may still protrude above the upper surface of the diamond single crystal particles after thermal expansion, leading to poor contact or interfacial gaps between the chip or heat sink and the composite material, thereby greatly increasing the interfacial thermal resistance.

[0019] When the groove depth is too large, such as exceeding 50 μm, although it can provide a larger deformation buffer space, it will cause the effective bonding thickness of the composite thermal conductivity layer between adjacent diamond single crystal particles to be excessively weakened. This reduction in thickness will weaken the mechanical bonding strength between diamond particles, making the composite material prone to particle detachment or bonding layer breakage when subjected to external impact or vibration.

[0020] By limiting the depth of the groove to the range of 10μm-50μm, the groove structure can effectively buffer thermal expansion, preventing the solidified phase from pushing up the diamond particles, while also maintaining a sufficiently thick sidewall of the composite heat-conducting layer to ensure the gripping force and support strength for the diamond single crystal particles. For example, for diamond / copper composite materials used in high-power laser diode heat dissipation, considering its thermal cycling requirements in the operating temperature range of room temperature to 85°C, the groove depth can be set to approximately 30μm. This value satisfies the requirements for thermal stress relief while maximizing the connection cross-sectional area of ​​the composite heat-conducting layer, thus balancing the thermal reliability and mechanical integrity of the material.

[0021] In one embodiment of this application, the copper alloy powder is at least one selected from copper-tin alloy powder, copper-titanium alloy powder, copper-chromium alloy powder, copper-tin-titanium alloy powder, or copper-zinc-titanium alloy powder, and the melting point of the copper alloy powder under vacuum conditions is 850-950°C. Preferably, the melting point of the copper alloy powder under vacuum conditions is 890-910°C.

[0022] As a binder phase in the sintering process, the composition of the copper alloy powder directly determines the quality of the interfacial bonding between diamond particles and the matrix, as well as the structural stability of the preform. This alloy powder system is constructed based on the principles of metallurgy and interfacial thermodynamics. The active elements it contains, such as tin, titanium, chromium, and zinc, can undergo interfacial reactions with carbon atoms on the diamond surface in a high-temperature liquid phase, generating metallic carbides such as titanium carbide (TiC) and chromium carbide (Cr3C2). This in-situ generated carbide layer significantly improves the wettability of liquid copper on the diamond surface, effectively solving the problem of loose interfacial bonding between pure copper and diamond due to non-wetting.

[0023] The melting point of the copper alloy powder is limited to 850-950℃ under vacuum conditions to ensure the structural integrity of the diamond single crystal particles during heat treatment. This temperature parameter is an engineering boundary value determined after comprehensively considering the thermal stability of diamond and the sintering process window. Given the risk of graphitization transformation in diamond at high temperatures, controlling the sintering temperature at 850-950℃ ensures that the heat treatment process remains within a safe range below the diamond graphitization initiation temperature. By selecting a low-melting-point alloy system, the copper alloy powder is fully melted, filling the gaps between diamond particles and forming an effective bonding layer, while maximally suppressing phase transformation or oxidative degradation of the diamond lattice, thus preserving the intrinsic high thermal conductivity and mechanical strength of the diamond single crystal particles.

[0024] By employing copper alloy powder with specific components and a limited melting point, and utilizing the in-situ reaction mechanism of active elements at the interface, a chemically bonded interface with high bonding strength can be constructed between the diamond and copper alloy bonding layers, effectively reducing interfacial thermal resistance. Simultaneously, the low melting point provides controllable thermodynamic conditions for subsequent sintering processes, allowing the preform forming process to be completed in a relatively mild temperature field. This ensures both the yield rate of material preparation and the integrity of the internal thermal conductivity channels of the final composite material.

[0025] In one optional embodiment, the diamond single crystal particles are arranged in a single layer, and the single-layer arrangement is at least one of vacuum adsorption arrangement, vibrating screen arrangement, template guided arrangement, or adhesive arrangement.

[0026] The monolayer arrangement of diamond single-crystal particles refers to the unfolding of diamond particles in a two-dimensional plane, such that the principal projection planes of each particle are parallel or nearly parallel to the same reference plane, and there is no particle stacking in the direction perpendicular to this plane. This monolayer close-packed arrangement, unlike the random discrete distribution of particles in three-dimensional space in traditional composite materials, can construct continuous in-plane thermal conductivity channels, avoiding the obstruction of heat transfer paths by non-thermally conductive or low-thermally conductive matrices, thereby improving the in-plane thermal conductivity efficiency of the composite material.

[0027] During the preform forming stage, single-layer arrangement can be achieved through at least one of the following methods: vacuum adsorption arrangement, vibrating screen arrangement, template-guided arrangement, or adhesive arrangement. Vacuum adsorption arrangement utilizes the principle of negative pressure adsorption to fix diamond single-crystal particles onto the surface of a supporting template to achieve an ordered single-layer arrangement. Vibrating screen arrangement uses mechanical vibration to automatically locate low-energy positions for the diamond single-crystal particles on a planar carrier. By adjusting the vibration frequency and amplitude, the particles overcome mutual friction and come close together to form an ordered single-layer array. Template-guided arrangement uses a mold with arrayed grooves or limiting holes on its surface to physically constrain and position the diamond single-crystal particles at specific points, precisely controlling the center distance and arrangement pattern. Adhesive arrangement involves pre-coating a layer of adhesive on a planar substrate, using adhesion to fix the placed diamond single-crystal particles, preventing displacement during subsequent copper alloy powder filling processes, and ensuring the stability of the single-layer structure. These arrangement methods effectively lock the spatial configuration of the diamond single-crystal particles, providing a precise structural basis for subsequently constructing a highly thermally conductive interconnect network within the gaps.

[0028] The synergistic effect of these technical features results in a highly ordered monolayer distribution of diamond single crystal particles on a macroscopic scale. This ordered arrangement not only eliminates the thermal insulation island effect caused by particle isolation in traditional random distribution, but also allows adjacent diamond particles to be directly connected through the subsequent filling material with high thermal conductivity. This creates a continuous heat conduction path with low thermal resistance within the plane of the composite material, meeting the structural requirements for high thermal conductivity and precise matching of thermal expansion.

[0029] In one embodiment of this application, the deposition method is at least one of chemical vapor deposition, electrochemical deposition, or electroless plating; the particle size of the diamond micropowder is 10-40 μm.

[0030] Diamond micropowder, as a high thermal conductivity reinforcing phase in composite thermal conductivity layers, has its particle size and concentration distribution in the deposition solution as key parameters affecting the thermal conductivity and filling quality of the composite layer. Nanoscale diamond micropowder possesses a high specific surface area, increasing the contact interface with the copper substrate; however, if the size is too small, severe agglomeration easily occurs, leading to dispersion difficulties. Micron-sized diamond micropowder (e.g., close to 40 μm) exhibits good dispersibility, but if the size is too large, it may cause blockage or uneven sedimentation in narrow filling voids. By limiting the particle size range to 10-40 μm, it is possible to ensure that the micropowder can smoothly enter the micron-sized filling voids with the deposition fluid while simultaneously considering its dispersion stability and thermal network construction capabilities.

[0031] Preferably, the concentration in the deposition solution is 5-50 g / L. This setting is to balance the deposition rate and the quality of the composite layer. When the concentration is below 5 g / L, the volume fraction of diamond powder in the composite thermal conductivity layer is too low, making it difficult to form an effective heat conduction pathway. When the concentration is above 50 g / L, the excessively high solid content may lead to a sharp increase in the viscosity of the deposition solution, causing powder agglomeration or an increase in the surface roughness of the deposition layer, or even the appearance of porosity defects. By controlling the concentration within the range of 5-50 g / L, diamond powder can be uniformly and dispersedly co-deposited in the copper substrate, forming a high-density, high-thermal-conductivity composite thermal conductivity layer.

[0032] In the above steps, by limiting the specific deposition method and the physical parameters of the diamond micron powder, the final composite thermal conductive layer can not only firmly connect adjacent diamond single crystal particles, but also significantly improve the overall thermal conductivity of the composite material and effectively reduce the interfacial thermal resistance between diamond particles.

[0033] In one embodiment of this application, the coefficient of thermal expansion of the composite material is controlled by adjusting the area ratio of diamond single crystal particles to the composite thermal conductive layer. The area ratio is achieved by adjusting at least one of the particle size, spacing, or arrangement density of the diamond single crystal particles.

[0034] Diamond single-crystal particles have an extremely low coefficient of thermal expansion, while the composite thermally conductive layer mainly consists of copper-based materials, which have a relatively high coefficient of thermal expansion. The area ratio of these two components directly determines the macroscopic thermal expansion performance of the composite material. By changing the proportion of diamond single-crystal particles in the material's surface area, the overall coefficient of thermal expansion of the composite material can be continuously controlled, allowing it to match the thermal expansion characteristics of different chip materials. This matching mechanism reduces thermal stress caused by thermal mismatch during thermal cycling, effectively preventing interface delamination or fracture, thereby improving the packaging reliability of electronic devices.

[0035] The adjustment method for the area ratio is determined inversely based on the target value of the coefficient of thermal expansion required for the actual application. In actual fabrication, if the target chip material is single-crystal silicon (coefficient of thermal expansion is approximately 2.6 ppm / ℃), a lower coefficient of thermal expansion is required in the composite material, thus increasing the area ratio of diamond single-crystal particles; conversely, if it is necessary to adapt to materials with a higher coefficient of thermal expansion, the area ratio of diamond single-crystal particles is appropriately reduced. Specifically, the area ratio of diamond single-crystal particles to the composite thermally conductive layer is achieved by adjusting at least one of the following: the particle size, spacing, or packing density of the diamond single-crystal particles.

[0036] When adjusting particle size, while keeping the spacing constant, using larger-sized diamond single crystal particles directly increases their coverage per unit area, thus reducing the overall coefficient of thermal expansion. Using smaller-sized particles reduces the area ratio of diamond single crystal particles, causing the coefficient of thermal expansion to shift towards the copper-based material. When adjusting spacing, with a fixed diamond single crystal particle size, reducing the spacing between particles results in a denser particle distribution, increasing the number of diamond single crystal particles per unit area and thus increasing their area ratio. Conversely, increasing the spacing increases the area ratio occupied by the composite heat-conducting layer. When adjusting the arrangement density, this can be achieved during the preform forming stage by controlling the arrangement of the diamond single crystal particles. For example, using a hexagonal close-packed arrangement yields extremely high diamond single crystal particle density and area ratio, while a loose square array arrangement significantly reduces the diamond single crystal particle density.

[0037] The aforementioned adjustment process is not a single-dimensional, independent operation. It allows for comprehensive adjustment of particle size, spacing, and arrangement density according to engineering needs, precisely obtaining the preset target area ratio, thereby achieving accurate customization of the composite material's thermal expansion coefficient. Through this physical structure-level control, diamond / copper composite materials can flexibly adapt to the thermal expansion requirements of various semiconductor materials such as single-crystal silicon chips, silicon carbide chips, and gallium nitride chips.

[0038] A second aspect of this application provides a diamond / copper composite material prepared by the above method, the composite material comprising: Multiple uniformly arranged diamond single crystal particles; A copper alloy connecting layer is used to connect adjacent diamond single crystal particles, keeping them connected. The composite heat conduction layer fills the gaps between adjacent diamond single crystal particles and, together with the copper alloy connecting layer, solidifies the adjacent diamond single crystal particles into one. The composite heat conduction layer is a co-deposited composite layer of copper and diamond micro powder. The upper surface of the composite heat-conducting layer is lower than the upper surface of the diamond single crystal particles, forming a groove structure.

[0039] The third aspect of this application provides the application of diamond / copper composite materials in chip heat dissipation, wherein the composite material is used as a thermal interface material or heat sink material for liquid cooling heat sinks, or as a thermal substrate or heat sink material for air cooling heat sinks.

[0040] The beneficial effects are: 1. This invention forms a preform by arranging multiple diamond single-crystal particles and filling the gaps with copper alloy powder, followed by sintering and solidification. The low-melting-point copper alloy locks the particle configuration within a safe temperature window. Subsequently, electrical discharge machining or electrochemical machining is used to selectively remove part of the copper alloy bonding layer to fill the voids. Then, a composite thermally conductive layer formed by the co-deposition of copper atoms and diamond micropowder is deposited in the voids using a deposition method, solidifying adjacent particles into a single unit and controlling the upper surface to be lower than the particle surface to form a groove structure. This process replaces the originally low thermal conductivity copper alloy bonding phase with a high thermal conductivity copper / diamond composite layer, constructing a continuous thermally conductive network within the layer and effectively reducing interfacial thermal resistance. Simultaneously, the formation of the groove structure, based on the height difference between the composite layer and the diamond particles, provides a buffer space for thermal expansion differences, avoiding interfacial separation caused by thermal stress concentration, and also serves as a liquid storage and chip removal mechanism in subsequent processing. This effectively solves the technical problems of poor interfacial wettability, high interfacial thermal resistance, discontinuous heat conduction channels, thermal expansion mismatch, and difficult processing in existing diamond / copper composite materials. Therefore, it avoids device failure and poor surface quality caused by poor thermal matching, and improves the reliability, thermal conductivity, and process adaptability of the material in high-end chip heat dissipation applications.

[0041] 2. In this invention, after the diamond single crystal particles are arranged in a single layer, a copper-diamond micro powder co-deposition composite connection layer is constructed between the particles through a three-step method of "firing-removal-deposition". This allows the heat generated by the chip to be directly conducted to the heat dissipation surface through the diamond single crystal particles without having to repeatedly cross the low thermal conductivity interface, thus fundamentally shortening the heat transfer path.

[0042] 3. Diamond has an intrinsic thermal conductivity of over 2000 W / m·K, while copper has a thermal conductivity of approximately 400 W / m·K. Taking diamond as an example, accounting for 50% of the heat-conducting area, its equivalent thermal conductivity contribution can reach over 1000 W / m·K. Combined with the auxiliary thermal conductivity contribution of the copper matrix, the overall equivalent thermal conductivity can theoretically reach over 1200 W / m·K. In contrast, similar products using traditional copper alloy solder as the connecting phase have thermal conductivity that is only 20%-40% of that of pure copper due to the large amount of Sn and Ti added to the solder, and the particles are randomly and discretely distributed, resulting in an equivalent thermal conductivity of typically less than 900 W / m·K. In comparison, this invention ensures that heat reaches the heat dissipation surface directly through diamond by a single-layer ordered arrangement. At the same time, the use of a copper-diamond micro-powder co-deposited composite layer as the connecting phase significantly reduces the interface thermal resistance and the thermal conductivity bottleneck of the connecting phase, making the thermal conductivity of the composite material significantly better than similar products. This meets the practical application requirements of next-generation high-power chips for heat dissipation materials with a thermal conductivity >1000 W / m·K. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a diamond / copper composite material according to the present invention; Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure.

[0044] Explanation of reference numerals in the attached figures: 1. Diamond single crystal particles; 2. Copper alloy connecting layer; 3. Composite heat conduction layer; 4. Groove structure. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0046] In the description of this application, it should be noted that, unless otherwise stated, "multiple" means two or more; the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, which are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above-mentioned orientation or positional relationship terms should not be understood or interpreted as a limitation of this application.

[0047] The number of any elements in the accompanying drawings is for illustrative purposes only and not as a limitation, and any naming is for distinction only and has no limiting meaning.

[0048] The principles and essence of the present invention will be explained in detail below with reference to several representative embodiments.

[0049] A method for preparing a diamond / copper composite material, the method comprising: Step S101: After arranging multiple diamond single crystal particles, copper alloy powder is filled into the gaps between adjacent particles. The copper alloy powder is then solidified by vacuum sintering to form a preform of a diamond-copper alloy bonding layer.

[0050] In this embodiment, diamond single-crystal particles serve as the reinforcing thermally conductive phase in the composite material, and their arrangement determines the direction of the thermal conductivity channels in the final material. The diamond single-crystal particles are arranged in a single layer, and the arrangement can be, for example, at least one of vacuum adsorption arrangement, vibrating screen arrangement, template-guided arrangement, or adhesive arrangement. Taking vibrating screen arrangement as an example, the diamond particles are placed on a vibrating device with a screen of a specific aperture. By adjusting the vibration parameters, the particles are evenly spread on the screen surface and fall into a preset support mold. Taking template-guided arrangement as an example, a graphite or metal template with an array of pits on its surface that match the size of the diamond particles is used to fill the pits to achieve high-precision positioning and arrangement. The particle size of the diamond particles is, for example, set to 0.5mm-1mm, a size range that balances particle specific surface area and operational convenience.

[0051] After the particle arrangement is completed, copper alloy powder is filled into the gaps between adjacent particles. The copper alloy powder, acting as a binder phase in low-temperature sintering, has a melting point of 850-950°C under vacuum conditions. The material includes at least one of copper-tin alloy powder, copper-titanium alloy powder, copper-chromium alloy powder, copper-tin-titanium alloy powder, or copper-zinc-titanium alloy powder. The filling process employs methods such as powder coating or gravity infiltration to ensure that the copper alloy powder fully coats the diamond particles and fills the triangular gaps between them. A sintering operation is then performed, with the sintering temperature set between 20°C and 100°C above the liquidus temperature of the copper alloy powder, and the holding time is 0.5-2 hours. Under these conditions, the copper alloy powder melts and spreads under capillary force, solidifying upon cooling to form a preform of the diamond-copper alloy bonding layer. This step aims to initially solidify the loosely arranged diamond particles into a mechanically strong whole through the sintering action of the low-melting-point copper alloy, thereby locking in the ordered arrangement of the diamond particles and providing structural support for subsequent removal and deposition processes.

[0052] Step S102: Electrochemical dissolution is used to remove part of the copper alloy bonding layer in the preform to form a filling void between adjacent diamond particles.

[0053] The prepared preform is placed in an electrolytic cell, with the preform as the anode and a stainless steel plate as the cathode. The electrolyte can be at least one of a sulfate system, a nitrate system, or a chloride system. The electrolysis parameters (such as current density, temperature, and time) are adaptively set according to the required removal depth, preferably to selectively dissolve the copper alloy bonding layer without significantly damaging the diamond particles. Since electrochemical dissolution is an existing technology, it will not be described in detail here.

[0054] Under the influence of an electric field, the copper in the copper alloy bonding layer undergoes anodic dissolution and enters the solution, while the diamond single crystal particles do not dissolve, forming voids between adjacent diamond particles.

[0055] After electrolysis, the preform that has undergone the removal process is removed, washed with deionized water, and dried.

[0056] This step removes the copper alloy phase, which has relatively low thermal conductivity, making room for the subsequent filling of a composite thermally conductive layer with high thermal conductivity. At the same time, it retains part of the copper alloy connecting layer as a skeleton support to prevent the diamond particles from shifting or collapsing during the dissolution process, thereby maintaining the integrity of the structure while achieving material optimization.

[0057] As an alternative, the preform can be placed on an electrical discharge machining (EDM) machine to remove part of the copper alloy bonding layer. EDM is a well-known specialized machining technique in the field, and its specific process parameters (such as pulse width, peak current, and discharge gap) can be adaptively adjusted by the operator according to the equipment model and removal depth requirements, ideally to selectively remove the copper alloy bonding layer without causing significant thermal damage to the diamond surface. After machining, part of the copper alloy bonding layer between the diamond single crystal grains is removed, forming interconnected, filled voids.

[0058] Step S103: Using a deposition method, a composite thermally conductive layer formed by the co-deposition of copper atoms and diamond micropowder is deposited in the gaps to solidify adjacent diamond single crystal particles into one; and the upper surface of the composite thermally conductive layer is lower than the upper surface of the diamond single crystal particles to form a groove structure.

[0059] After the voids are filled, a composite thermally conductive layer is constructed within them using a deposition method. The deposition method includes, for example, at least one of chemical vapor deposition (CVD), electrochemical deposition, or electroless plating. Taking electrochemical deposition as an example, the preform is placed as the cathode in an electroplating bath containing copper ions, while diamond micropowder with a particle size of 30 μm and a concentration of 25 g / L is added to the bath. Under the influence of an electric field, copper atoms are reduced and precipitated on the cathode surface, while the diamond micropowder adsorbed on the cathode surface is encapsulated by the grown copper layer, co-depositing to form a copper-diamond micropowder composite coating. This co-deposition process allows the composite thermally conductive layer to fill the voids, firmly connecting adjacent diamond single crystal particles into a single unit, constructing a highly efficient heat-conducting channel between the diamond particles.

[0060] During or after deposition, process parameters are controlled to ensure that the upper surface of the composite thermally conductive layer is lower than the upper surface of the diamond single crystal particle, thereby forming a groove structure. For example, during deposition, the composite thermally conductive layer is grown to a predetermined height and then stopped by controlling the deposition amount (such as deposition time or total current), at which point its upper surface is naturally lower than the top of the diamond particle; or, after deposition, a portion of the composite thermally conductive layer is removed by precision grinding or polishing, making its upper surface lower than the upper surface of the diamond single crystal particle. The depth of this groove structure is controlled, for example, between 10 μm and 50 μm (in this embodiment, the groove depth is controlled at approximately 25 μm; however, in other embodiments, the groove depth can also be 20 μm, 30 μm, or 40 μm). The groove structure not only provides a buffer space for the thermal expansion difference between diamond and the bonded material, avoiding interface cracking caused by expansion coefficient mismatch during thermal cycling, but also serves as a coolant reservoir and a chip containment cavity in the subsequent grinding and polishing process, effectively improving heat dissipation and chip removal conditions of the processed surface and improving the surface quality of the final product.

[0061] The aforementioned technical processes synergistically solve the technical problems encountered in the preparation of diamond / copper composite materials, such as high interfacial thermal resistance, discontinuous thermal conductivity channels, and processing difficulties. Through a process chain of arrangement-sintering-dissolution-deposition, a low-melting-point copper alloy is first used to achieve temporary consolidation and configuration locking of the particles. Then, the low thermal conductivity phase is removed by selective dissolution while reserving space. Finally, a high thermal conductivity composite bonding layer is constructed through the co-deposition of copper and diamond micropowder, thus forming a continuous, low thermal resistance thermal conductivity network between the diamond particles. Simultaneously, the introduction of the groove structure effectively alleviates the concentration of thermal stress within the material and facilitates subsequent processing, resulting in a final diamond / copper composite material that possesses excellent thermal conductivity, good thermal expansion matching, and easily machinable surface properties.

[0062] The above-mentioned method for forming the groove structure includes: Step S201: During the deposition process, the deposition amount is controlled so that the upper surface of the composite thermal conductive layer is lower than the upper surface of the diamond single crystal particles.

[0063] By precisely controlling the duration of the deposition process or the raw material supply rate, the thickness of the composite thermally conductive layer in the vertical growth direction is limited to a preset range, ensuring that the elevation of its upper surface after growth termination is lower than the top elevation of the diamond single crystal particle. This composite thermally conductive layer is a structured material layer formed by the co-deposition of copper atoms and diamond microparticles, and the control of its deposition amount directly determines the final depth of the groove. For example, by monitoring the thickness change during the deposition process in real time, when the deposited layer reaches a predetermined difference of 25 μm from the upper surface of the diamond single crystal particle, the deposition operation is immediately stopped, thereby forming a groove structure with a specific depth gradient. This method of forming grooves in situ during the deposition process can avoid potential damage to the material surface from subsequent machining, maintaining the original distribution state of the diamond microparticles in the copper matrix and the integrity of the bonding interface.

[0064] Step S202: After the composite thermal conductive layer is deposited and formed, and the upper surface of the composite thermal conductive layer is not lower than the upper surface of the diamond single crystal particle, part of the composite thermal conductive layer is removed by grinding or polishing, so that the upper surface of the composite thermal conductive layer is lower than the upper surface of the diamond single crystal particle.

[0065] Selective removal is achieved by leveraging the significant hardness difference between diamond single-crystal particles and the copper-based composite thermal conductive layer. First, the composite thermal conductive layer is deposited, at which point its upper surface is typically flush with or slightly higher than the upper surface of the diamond single-crystal particles. Then, the entire surface of the composite material is thinned using grinding tools or polishing equipment. Since the Mohs hardness of diamond single-crystal particles is 10, much higher than that of the copper matrix, the softer composite thermal conductive layer is preferentially removed during grinding or polishing, while the higher-hardness diamond single-crystal particles act as a stop, naturally halting or slowing the removal process at the diamond particle surface. By controlling process parameters such as grinding pressure, grinding disc rotation speed, or polishing time, the thickness of the removed composite thermal conductive layer is precisely controlled until its upper surface is lower than the upper surface of the diamond single-crystal particles, thus forming the desired groove structure. For example, using a grinding disc with diamond abrasive for planar grinding, processing is stopped when the surface of the diamond single-crystal particles is exposed and the surface of the composite thermal conductive layer reaches the target depth of 10μm-50μm. This approach eliminates the need for complex thickness endpoint control during the deposition stage. Instead, it integrates the groove formation process into the conventional surface smoothing process, offering strong process compatibility and suitability for mass production.

[0066] By employing either or a combination of the above two methods, a groove structure can be reliably formed between diamond single crystal particles. This groove structure not only provides the necessary buffer space for the thermal expansion differences of the material during thermal cycling, effectively reducing interfacial thermal stress, but also serves as a coolant reservoir and a chip removal channel during subsequent grinding and polishing processes, improving heat dissipation and chip removal conditions on the processed surface, ultimately resulting in a diamond / copper composite material with excellent surface quality and stable thermal properties.

[0067] like Figure 1 and 2 As shown, this embodiment also provides a diamond / copper composite material. The composite material includes: Multiple uniformly arranged diamond single crystal particles 1; The copper alloy connecting layer 2 connects adjacent diamond single crystal particles to maintain the connection between them. The composite heat conduction layer 3 fills the gap between adjacent diamond single crystal particles and together with the copper alloy connecting layer 2, it solidifies the adjacent diamond single crystal particles into one. The composite heat conduction layer 3 is a co-deposited composite layer of copper and diamond micro powder. The upper surface of the composite thermal conductive layer 3 is lower than the upper surface of the diamond single crystal particles, forming a groove structure 4.

[0068] The composite material was prepared by the method described above.

[0069] In this embodiment, the diamond single crystal particles 1 are 0.5 mm in size and are arranged in an orderly single layer through a vibrating screen; the copper alloy connecting layer 2 is Cu-Sn-Ti alloy powder, which is sintered in a vacuum at a temperature of 920°C for 1 hour; the thickness of the copper alloy connecting layer 2 is 0.2 mm and the groove structure 4 is 25 μm.

[0070] Part of the copper alloy bonding layer 2 is removed by electrochemical processing to form a filling void; a composite thermal conductive layer 3 is formed in the filling void by electrochemical co-deposition. The diamond micro powder in the plating solution has a particle size of 30μm and a concentration of 25g / L. The deposition thickness is controlled so that the groove depth is about 25μm.

[0071] In this embodiment, multiple diamond single-crystal particles 1 serve as the core heat-conducting carrier of the composite material, arranged in a single layer with close proximity. This ordered arrangement constructs a continuous planar heat-conducting network, effectively avoiding the problem of blocked heat conduction pathways caused by the random distribution of diamond particles in traditional composite materials. The diamond single-crystal particles 1 have extremely high thermal conductivity, enabling rapid heat conduction. Their particle size can be selected according to actual application requirements, for example, 0.5-1 mm. This size range balances the heat dissipation capacity of a single particle with the filling density between particles and cost, which is beneficial for maintaining the compactness of the structure while ensuring high thermal conductivity.

[0072] The copper alloy connecting layer 2 is mainly formed during the preparation process by filling copper alloy powder and sintering it, followed by partial electrochemical or electrical discharge machining to remove excess connecting structures. This copper alloy connecting layer 2 serves as the skeletal support of the composite material, maintaining the relative positional stability of the diamond single crystal particles 1 during the preparation process. The material of the copper alloy connecting layer 2 can be at least one of copper-tin alloy, copper-titanium alloy, copper-chromium alloy, copper-tin-titanium alloy, or copper-zinc-titanium alloy. These alloy materials have low melting points (e.g., below 950°C under vacuum conditions), enabling sintering at lower temperatures and thus preventing graphitization of the diamond at high temperatures. Although the thermal conductivity of copper alloy itself is lower than that of pure copper, in this design, it mainly serves a connecting and supporting role, while the subsequently filled high thermal conductivity composite thermal conduction layer 3 will undertake the main interfacial heat conduction task.

[0073] The composite thermal conductivity layer 3 is a key functional structure in this embodiment, formed by co-depositing highly thermally conductive copper atoms and high-hardness diamond micropowder in the interstices of diamond particles. The particle size of the diamond micropowder can be, for example, 10-40 μm, and its concentration in the deposition solution can be, for example, 5-50 g / L. The deposition method can be at least one of chemical vapor deposition, electrochemical deposition, or electroless plating, which ensures that the composite thermal conductivity layer 3 fully fills the interstices and bonds well with the surface of the diamond particles. This co-deposition structure greatly improves the thermal conductivity of the bonding layer itself and reduces the interfacial thermal resistance between diamond particles, allowing heat to be rapidly transferred along the efficient pathways formed by the diamond single crystal particles 1 and the composite thermal conductivity layer 3 between them.

[0074] The upper surface of the composite heat-conducting layer 3 is lower than the upper surface of the diamond single crystal particle 1, thus forming a groove structure 4. The depth of the groove structure 4 can be controlled, for example, between 10μm and 50μm. This groove structure 4 has multiple technical benefits: First, in terms of thermal performance, due to the difference in thermal expansion coefficients between diamond and the copper matrix material, the groove provides a buffer space for thermal expansion, avoiding warping of the composite material surface or air gaps between the composite material and the heat-dissipating device (such as a chip) caused by the mismatch in thermal expansion coefficients, thereby ensuring the stability of the interface thermal contact during long-term operation; Second, in terms of machining, the groove structure 4 can serve as a coolant storage tank and a debris receiving cavity in subsequent grinding or polishing processes, effectively improving the heat dissipation conditions of the processing area, promoting debris discharge, and improving processing efficiency and surface quality; Finally, the groove structure 4 can also release the interface concentrated stress under thermal cycling or external loads to a certain extent, improving the overall reliability of the composite material.

[0075] The diamond / copper composite material provided in this embodiment, prepared by the above method, inherits the synergistic advantages of ordered arrangement, skeletal support, and high thermal conductivity filling in the preparation process. Uniformly arranged diamond single-crystal particles 1 constitute the basic thermally conductive skeleton, the residual copper alloy connecting layer 2 ensures the mechanical integrity of the structure, and the copper-diamond micropowder co-deposited composite thermally conductive layer 3 filling the gaps constructs a low-thermal-resistance thermally conductive bridge. In particular, the groove structure 4 formed by the upper surface of the composite thermally conductive layer 3 being lower than the upper surface of the diamond single-crystal particles 1 cleverly resolves the contradiction between material thermal expansion matching and the difficulty of subsequent processing.

[0076] Through the above technical solution, this application discloses a diamond / copper composite material that combines high thermal conductivity, good thermal expansion matching, and excellent processing performance. This composite material utilizes the high thermal conductivity of diamond single crystal particles 1, and strengthens the thermal connection between particles through a copper-diamond micropowder co-deposited composite thermal conductive layer 3, reducing the overall thermal resistance. Simultaneously, the groove structure 4 effectively alleviates thermal stress problems caused by differences in thermal expansion coefficients, prevents interface delamination or air gaps, and serves as a processing aid structure to improve surface treatment quality. This composite material is particularly suitable as a heat dissipation substrate or heat sink material for high-end chips (such as CPUs, GPUs, IGBTs, etc.), and can meet the stringent requirements for heat dissipation reliability of high power density devices.

[0077] This embodiment also provides the application of diamond / copper composite materials in chip heat dissipation. Specifically, the composite material is used as a liquid-cooled heat sink or an air-cooled heat sink.

[0078] When composite materials are used in liquid-cooled heat sinks, they can serve as core heat-conducting components such as liquid cooling plates or heat sinks. In this application scenario, one side of the composite material is in close contact with the high-power chip, while the other side is in contact with the coolant channel. The liquid-cooled heat sink utilizes the circulating flow of coolant in the channel to remove heat. Thanks to the extremely high thermal conductivity of the diamond / copper composite material, it can quickly conduct the heat generated by the chip to the coolant, and achieve efficient heat dissipation by utilizing the high heat transfer coefficient of liquid cooling. Furthermore, since the coefficient of thermal expansion of this composite material can be adjusted by regulating the area ratio of diamond single crystal particles to the composite heat-conducting layer, it can match the coefficient of thermal expansion of the chip material (such as silicon, silicon carbide, etc.), thereby maintaining good interfacial contact under wide temperature range variations. This avoids increased interfacial gaps or increased contact thermal resistance due to thermal expansion mismatch, ensuring the long-term reliability of the liquid-cooled heat sink.

[0079] When composite materials are used in air-cooled heat sinks, they can serve as the substrate or heat sink material. Air-cooled heat sinks primarily dissipate heat by increasing the contact area between the heat sink fins and the air and forcing convection. In this application, the high thermal conductivity of the composite material can rapidly conduct heat from the chip to the entire heat sink substrate, and then to the heat sink fins connected to it. Compared to traditional aluminum or copper substrates, diamond / copper composite substrates have higher thermal conductivity, which can significantly reduce the thermal resistance of the heat sink base plate, reduce the temperature difference between the chip and the base of the heat sink fins, and thus improve the efficiency of air cooling. At the same time, the high thermal conductivity of this material helps to eliminate local hot spots on the substrate surface, making the temperature distribution more uniform and preventing chip damage due to localized overheating. By using this composite material to make air-cooled heat sinks, the heat dissipation requirements of high-power electronic devices can be met without increasing the size and weight of the heat sink, making it particularly suitable for space-constrained or weight-sensitive applications.

[0080] Process parameters of this invention embodiment: Diamond single crystal particles: 0.5mm in diameter, arranged in an orderly single layer on a vibrating screen; Copper alloy bonding layer: Cu-Sn-Ti alloy powder, vacuum sintering temperature 920℃, holding time 1h; Removal method: Electrochemical machining removes part of the copper alloy layer, forming a void-filling layer; Composite thermal conductive layer: electrochemical co-deposition, diamond micro powder with a particle size of 30μm and a concentration of 25g / L in the plating solution, and the deposition thickness is controlled to make the groove depth about 25μm.

[0081] Process parameters for Comparative Example 1 (traditional copper alloy brazing, no co-deposited layer): Diamond single crystal particles: 0.5 mm in diameter, arranged in an orderly single layer on a vibrating screen (same as in the example); Copper alloy bonding layer: Cu-Sn-Ti alloy powder fills all gaps and is vacuum sintered (same as in the example); No removal or co-deposition steps are performed; the final surface is ground to a smooth finish (without grooves).

[0082] Process parameters for Comparative Example 2 (randomly distributed diamonds, other parameters the same as in the Example): Diamond single crystal particles: 0.5 mm in diameter, randomly distributed after being mixed with copper alloy powder (without single-layer ordered arrangement); the remaining processes are the same as in the example (sintering → removal → co-deposition → forming grooves).

[0083] The thermal conductivity of the diamond-copper composite materials of Examples 1, 2, and 3 were tested using the flash method. The test results are shown in Table 1.

[0084] Table 1. Thermal conductivity test results of diamond / copper composite materials As shown in Table 1, the thermal conductivity of the diamond / copper composite material obtained in the examples is significantly higher than that of Comparative Examples 1 and 2. Under the same 60% diamond volume fraction, the composite thermal conductivity layer formed by the monolayer ordered arrangement of diamond single crystal particles and the co-deposition of copper / diamond micropowder achieves a significantly higher thermal conductivity than that of the traditional copper alloy connection structure.

Claims

1. A method for preparing a diamond / copper composite material, characterized in that, Includes the following steps: After arranging multiple diamond single crystal particles, copper alloy powder is filled into the gaps between adjacent particles, and the copper alloy powder is solidified by sintering to form a preform of a diamond-copper alloy bonding layer. Subsequently, a portion of the copper alloy bonding layer in the preform is removed to form a filling gap between adjacent diamond particles; Finally, a deposition method is used to deposit a composite thermally conductive layer formed by the co-deposition of copper atoms and diamond micropowder in the filling voids, which consolidates adjacent diamond single crystal particles into one; and the upper surface of the composite thermally conductive layer is lower than the upper surface of the diamond single crystal particles to form a groove structure.

2. The preparation method according to claim 1, characterized in that, The method for removing part of the copper alloy bonding layer in the preform is electrical discharge machining or electrochemical machining.

3. The preparation method according to claim 2, characterized in that, The groove structure is formed by at least one of the following methods: (a) During the deposition process, the deposition amount is controlled so that the upper surface of the composite thermal conductive layer is lower than the upper surface of the diamond single crystal particle; (b) After the composite thermal conductive layer is deposited and the upper surface of the composite thermal conductive layer is not lower than the upper surface of the diamond single crystal particle, part of the composite thermal conductive layer is removed by grinding or polishing so that the upper surface of the composite thermal conductive layer is lower than the upper surface of the diamond single crystal particle.

4. The preparation method according to claim 1, characterized in that, The diamond single crystal particles are arranged in a single layer, and the single layer arrangement is at least one of vacuum adsorption, vibrating screen arrangement, template-guided arrangement, or adhesive arrangement.

5. The preparation method according to claim 1, characterized in that, The diamond particles are not less than 0.5 mm; the depth of the groove structure is 10 μm-50 μm.

6. The preparation method according to claim 1, characterized in that, The copper alloy powder is at least one of copper-tin alloy powder, copper-titanium alloy powder, copper-chromium alloy powder, copper-tin-titanium alloy powder, or copper-zinc-titanium alloy powder, and the melting point of the copper alloy powder under vacuum conditions is 850-950℃.

7. The preparation method according to claim 1, characterized in that, The deposition method is at least one of chemical vapor deposition, electrochemical deposition, or electroless plating; the particle size of the diamond micropowder is 10μm-40μm.

8. A diamond / copper composite material, characterized in that, The composite material is prepared by the method according to any one of claims 1-7, and comprises: Multiple uniformly arranged diamond single crystal particles; A copper alloy connecting layer is used to connect adjacent diamond single crystal particles, keeping them connected. A composite thermal conductive layer is filled in the gap between adjacent diamond single crystal particles, and together with the copper alloy connecting layer, it solidifies the adjacent diamond single crystal particles into one. The composite thermal conductive layer is a co-deposited composite layer of copper and diamond micro powder. The upper surface of the composite thermal conductive layer is lower than the upper surface of the diamond single crystal particle, forming a groove structure.

9. The application of the diamond / copper composite material according to claim 8 in chip heat dissipation, characterized in that, The composite material is used as a thermal interface material or heat sink material for liquid-cooled radiators, or as a thermal substrate or heat sink material for air-cooled radiators.

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