Electronic packaging heat dissipation substrate and processing technology and application thereof

Abstract

The invention discloses an electronic packaging heat dissipation substrate and a processing technology and application thereof. The electronic packaging heat dissipation substrate comprises a copper-clad diamond copper plate, a diamond sheet located on the copper-clad diamond copper plate and a first copper layer covering the diamond sheet. The copper-clad diamond copper plate comprises a diamond copper core material and a copper layer located on the surface of the diamond copper core material. The diamond copper core material and the copper layer form a composite board with a copper layer-core material-copper layer sandwich structure; and the copper-clad diamond copper plate, the diamond sheet and the first copper layer are connected into a whole through brazing. According to the electronic packaging heat dissipation substrate, the peeling and cracking risks can be reduced, and the problem of low heat transfer efficiency is solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly relates to an electronic packaging heat dissipation substrate, its processing technology and application. Background Art

[0002] The progress of semiconductor technology has greatly promoted the development and application of power electronic devices. With the rapid progress of chip manufacturing processes, IGBT power devices are developing rapidly towards miniaturization and multi-functionality, which has brought serious heat dissipation problems. Currently, when IGBT power devices are working, they will generate a large amount of heat. If the heat is not dissipated in a timely and effective manner, it may lead to a decline in device performance or even damage. Therefore, the thermal management of power devices is crucial. Thermal management mainly includes heat conduction, convection and radiation to ensure that the device operates within a safe temperature range. For power devices, the heat transfer path is: chip / diode → solder layer under the chip → DBC copper layer → DBC ceramic layer → DBC copper layer → substrate solder layer → substrate → thermal conductive silicone → heat sink → external environment.

[0003] Currently, heat transfer, heat conduction and heat dissipation of heat dissipation devices mainly occur on the DBC layer (ceramic copper clad substrate), copper substrate and heat sink. The DBC ceramic substrate is heat-treated in an oxygen-containing nitrogen environment at a high temperature above 1000 °C, so that the copper foil and the ceramic substrate are tightly bonded by means of eutectic bonding. Its process flow is usually: cleaning and drying of ceramic substrate and copper foil → pretreatment of copper foil → high-temperature eutectic bonding of copper foil and ceramic substrate → cold and hot step cycling cooling → quality inspection → etching pattern as required → electroless nickel plating (or gold plating) → quality inspection → laser scribing and cutting → finished product quality inspection → vacuum or nitrogen filling packaging → into the finished product warehouse. This technology has high bonding strength, excellent thermal conductivity and thermal stability. Currently, commonly used ceramic substrate materials include alumina (Al2O3), aluminum nitride (AlN) and zirconia toughened alumina (ZTA). The core bonding method of this technology lies in eutectic bonding. At high temperature, oxygen in the copper foil reacts with the surface of the ceramic substrate to form a layer of Cu-O-Al or Cu-O-N compound, realizing the firm connection between copper and ceramic. Thanks to the relatively high eutectic bonding strength between the copper foil and the ceramic, the copper thickness of the DBC substrate can generally be adjusted to 100 - 600 μm. The copper substrate is a common heat dissipation structure for power semiconductor modules in the traditional field, and its main function is to transfer the heat of the module outward and provide mechanical support for the module. The heat sink part mainly uses W, Mo (the thermal conductivity of W is 174 Wm -1 K -1 、The thermal conductivity of Mo is 140 Wm -1 K -1Copper-tungsten alloys and copper-molybdenum alloys with particles such as are used as manufacturing materials. In addition, a thermal interface material TIM with a high thermal conductivity (such as thermally conductive epoxy resin or silicone) is required to fill the gaps between the copper-clad ceramic substrate and the copper heat sink, as well as between the copper heat sink and the heat sink, and a certain pressure is applied for curing to ensure good thermal contact and bond them together to form a complete heat conduction structure.

[0004] Modern electronic packaging materials not only require high thermal conductivity, good thermal expansion coefficient and good mechanical properties; but also require light weight, excellent dielectric constant and good chemical stability. Traditional heat dissipation materials such as copper-tungsten alloys, alumina and aluminum nitride ceramic substrates can no longer meet the requirements of modern electronic technology for heat dissipation materials, and advanced composite materials with high thermal conductivity and good thermal expansion coefficient need to be found for replacement. Copper-clad diamond material is a composite material obtained by uniformly covering a copper layer on the surface of diamond particles or a diamond matrix by physical or chemical methods, combining the high thermal conductivity and high hardness of diamond with the electrical conductivity and ductility of copper, and showing significant advantages in the fields of electronic packaging, heat dissipation, precision machining, etc. Currently, for the copper-clad diamond substrate materials available on the market, the thickness of the upper and lower copper layers usually needs to be kept consistent, about 100 μm; this is because the thermal expansion coefficients of diamond (thermal expansion coefficient: 0.8×10 -6 ) and copper (thermal expansion coefficient: 18×10 -6 ) are quite different. Too thick a copper layer will increase the difference in thermal expansion coefficients between copper and diamond, generate large interfacial stress, and increase the risk of peeling or cracking. Due to the gaps between the copper-clad ceramic substrate and the copper heat sink, as well as between the copper heat sink and the heat sink in the heat conduction structure, and the thermal conductivity of air is very small, a relatively large contact thermal resistance is thus caused. Although using the thermal interface material TIM can fill this air gap, reduce the contact thermal resistance and improve the heat dissipation performance; however, the thermal conductivity gap between TIM and copper and diamond is relatively large, so the heat transfer efficiency will be reduced. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the purpose of this application is to provide an electronic packaging heat dissipation substrate, reducing the risks of peeling and cracking, and at the same time solving the problem of low heat transfer efficiency.

[0006] To solve the above problems, the technical solutions adopted in this application are as follows: This application provides an electronic packaging heat dissipation substrate, including a copper-clad diamond copper plate, a diamond sheet located on the copper-clad diamond copper plate, and a first copper layer covering the diamond sheet; the copper-clad diamond copper plate includes a diamond copper core material and a copper layer located on the surface of the diamond copper core material; the diamond copper core material and the copper layer form a composite plate with a sandwich structure of copper layer - core material - copper layer; the copper-clad diamond copper plate, the diamond sheet and the first copper layer are connected into one body by brazing.

[0007] As a further preferred solution, the copper-clad diamond copper plate described in the embodiments of the present application is a composite material sintered from a hexahedral copper foil shell and at least one diamond-copper composite layer disposed in the copper foil shell; the diamond-copper composite layer includes a copper mesh and diamond particles coated with a coating on the surface, and the diamond particles are arranged in the meshes of the copper mesh, and copper powder is filled in the gaps between the meshes and the diamond particles; Cu atoms in the copper mesh diffuse through the coating to the surface of the diamond to form a mixed transition zone.

[0008] As a further preferred solution, the mesh described in the embodiments of the present application has a regular hexahedron structure or a honeycomb structure of a regular octahedron, the wall thickness of the mesh is 10-20 μm, and the edge length L of the mesh is 10-20 μm larger than the particle size D of a single diamond particle.

[0009] As a further preferred solution, the thickness of the copper layer at the bottom of the copper foil shell described in the embodiments of the present application is greater than the thickness of the copper layer covering the surface.

[0010] As a further preferred solution, the coating on the surface of the diamond particles described in the embodiments of the present application is a coating formed of one material among Ti, Cr, W, V, and Zr or a composite coating formed of two or more materials; the thickness of the coating is 0.1-0.5 μm.

[0011] As a further preferred solution, metal coatings are plated on the upper and lower surfaces of the diamond sheet described in the embodiments of the present application, and the thickness of the metal coatings is 50-300 nm; the materials of the metal coatings are one of metal chromium, titanium, tungsten, molybdenum, and tantalum.

[0012] As a further preferred solution, a copper-containing active solder is coated on the surface of the metal coating, and the copper-containing active solder is one of Cu-Sn-Cr, Ag-Cu-Cr, Cu-Sn-Ti, and Ag-Cu-Ti, and the thickness of the brazing layer is 50-300 μm.

[0013] Furthermore, the embodiments of the present application also provide a processing technology for an electronic packaging heat dissipation substrate, which combines sintering and brazing welding to obtain a heat dissipation substrate with a layer structure, reducing the risks of peeling and cracking and simultaneously solving the problem of low heat transfer efficiency. The processing technology includes the following steps. Surface treatment of the diamond sheet: A metal coating is plated on the upper and lower surfaces of the surface-activated diamond sheet by magnetron sputtering; then a copper-containing active brazing is coated on the metal coating to obtain a surface-treated diamond sheet. Preparation of copper-clad diamond copper plate: 1) Stamp and fold a copper foil sheet into a hexahedral copper foil box with an upper cover and an opening, place it in a mold, and lay a copper mesh with a uniform grid in the hexahedral copper foil box; 2) Use an arrangement machine to arrange diamond particles coated with a coating on each grid of the copper mesh; 3) Place the hexahedral copper foil box with arranged diamond particles and the mold on a vibrating table, and spray copper powder onto the copper mesh in the vibration mode until the copper powder fills the voids of the copper mesh and reaches the same height as the copper mesh; 4) Place another copper mesh in the hexahedral copper foil box, and repeat steps 2) and 3) until the copper mesh is flush with the height of the hexahedral copper foil box; 5) Cover the upper cover at the opening, and integrate the upper cover with the copper foil box to obtain a preform; 6) Place the preform in a vacuum sintering furnace for sintering to obtain a sintered copper-clad diamond copper plate; Brazing connection: Place the copper-clad diamond copper plate, the diamond sheet after surface treatment, and the copper sheet for forming the first copper layer into a fixture in sequence, fasten them, and then place them in a vacuum brazing furnace for vacuum brazing to obtain an electronic packaging heat dissipation substrate.

[0014] As a further preferred solution, in the processing technology described in the embodiment of the present application, the surface treatment step of the diamond sheet includes: Surface activation: Alternately ultrasonically clean the diamond sheet with 5wt% NaOH and 10wt% HCl solutions for 8 - 12 min to remove surface impurities, and then rinse it with pure water and dry it; Magnetron sputtering of a metal coating: Place the diamond sheet after surface activation in a graphite mold for magnetron sputtering to form a metal coating, ensuring that the sputtering area is flat and unobstructed. The sputtering conditions are: DC sputtering power 120 - 180 W, sputtering time 1 - 3 h, target-substrate distance 5 - 10 cm, argon gas flow 15 - 25 sccm, and vacuum degree <5×10 -3 Pa; Heat treatment: After forming the metal coating, anneal the diamond sheet in vacuum at 400 - 600 °C for 1 - 2 h; Acid etching treatment: After the annealing is completed, etch the diamond sheet with 30 - 50 vol% nitric acid solution for 30 - 60 min to remove the unreacted layer and expose the active interface.

[0015] As a further preferred solution, in the processing technology described in the embodiment of the present application, when preparing the copper-clad diamond copper plate, the vacuum sintering conditions are: the vacuum degree is 10 -1 ~10 -3 Pa, the heating process is heated from room temperature to 900 - 1100 °C at a rate of 5 - 20 °C / min, start pressurizing after holding for 20 - 120 min, the pressurizing pressure is 20 - 50 MPa, and keep the pressure and cool to room temperature.

[0016] As a further preferred solution, in the brazing welding step of the processing technology described in the embodiments of the present application, vacuum brazing is adopted, and the vacuum degree is 10 -1 ~10 -5 Pa, heated to 700~900°C at a rate of 5~10°C / min, held for 30~60 min, and pressurized to 0.1~10 MPa while holding.

[0017] As a further preferred solution, the electronic packaging heat dissipation substrate described in the embodiments of the present application can be applied in multiple fields. For example, in the field of high-power laser diodes, it can be used in medical lasers, industrial cutting equipment, etc.; in the field of GaN RF amplifiers, it can be used in 5G base stations, radar systems, etc.; in the field of power electronics modules, it can be used in EV motor control, solar inverters, etc.; in the field of aerospace electronic equipment, it can be used in radar modules, satellite communications, etc.; in the field of high heat flux density electronic device processing, it can be used for liquid cooling of AI servers, GPU clusters, and cloud computing and big data centers, as well as manufacturing devices such as 5G / 6G base station GaN RF chips and electric vehicle SiC inverter modules; in the field of high-energy laser systems, it is used to manufacture fiber laser pump couplers and solid laser crystal heat sinks; in the field of nuclear energy and fusion devices, it is used to manufacture divertor targets and plasma first walls of nuclear fusion reactors; in the field of special power and energy equipment, it is used to manufacture IGBT modules for electromagnetic catapult systems and contacts for high-voltage DC circuit breakers; in the field of aerospace, it is used in the beam spot area of the electron beam focusing system and around the laser melt pool of metal 3D printing; in the field of quantum and superconductivity, it is used to manufacture microwave resonators for superconducting qubits and joints for room-temperature superconducting transmission lines.

[0018] The embodiments of the present application also provide an application of the electronic packaging heat dissipation substrate in manufacturing an electronic packaging heat sink.

[0019] The embodiments of the present application also provide an electronic packaging heat sink, which includes the electronic packaging heat dissipation substrate described in the embodiments of the present application.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The electronic packaging heat dissipation substrate described in this application includes a copper - clad diamond copper plate, a diamond sheet located on the copper - clad diamond copper plate, and a first copper layer covering the diamond sheet, actually forming a multi - layer structure of copper layer - diamond sheet - copper layer - diamond copper - copper layer. The diamond substrate serves as the core heat conduction channel, combining the upper and lower copper layers to form a longitudinal gradient heat conduction network, fully leveraging the heat conduction advantages of diamond and copper. Heat can be quickly conducted from the electronic device to the diamond substrate and then rapidly diffused through the copper layer, greatly improving the heat conduction efficiency, effectively reducing the temperature of the electronic device during operation, preventing problems such as performance degradation, shortened lifespan, or even damage due to overheating, and ensuring the stable and reliable operation of the electronic device. At the microscopic level, in the multi - layer structure, the bonding interface layer between layers forms chemical bonds through the chemical reaction of copper atoms with the atoms on the diamond surface during the sintering process, or physical embedding is achieved by copper atoms infiltrating into the tiny pores on the diamond surface. This dual bonding method greatly enhances the bonding strength between the copper layer and the diamond substrate.

[0021] 2. Further, in the electronic packaging heat dissipation substrate described in this application, the copper - clad diamond copper plate, the diamond sheet located on the copper - clad diamond copper plate, and the copper layer covering the diamond sheet are connected by welding. During the welding process, high temperature causes the atoms on the surface of the solder and the copper layers of the two composite plates to diffuse, forming a metallurgical bond; this bonding method has very high strength and can firmly connect two dissimilar material layers together to form an integral structure. Welding connection enables each layer between the two multi - layer structures to bear stress synergistically. When an external force acts, the stress can be evenly distributed throughout the heat dissipation substrate. For example, during the chip packaging process, if the heat dissipation substrate is squeezed or stretched, the welding connection can ensure that the two composite plates jointly bear the stress, avoiding cracking caused by excessive local stress.

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is a schematic structural diagram of the electronic packaging heat dissipation substrate described in the embodiments of this application.

[0025] Among them, each reference numeral is: 10, copper - clad diamond copper plate; 11, diamond copper core material; 12, copper layer; 20, diamond sheet; 30, first copper layer. Specific Embodiments

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0027] In the present application, the term "including" and other equivalent descriptive methods involved in the specification and claims are intended to cover non-exclusive inclusion, that is, it includes both the content clearly described in the specification and claims and may also include steps or units inherent in the product, method, or structure but not described in the specification and claims.

[0028] As Figure 1 shown, an electronic packaging heat dissipation substrate is provided in an embodiment of the present application, which includes a copper-clad diamond copper plate 10, a diamond sheet 20 located on the copper-clad diamond copper plate 10, and a first copper layer 30 covering the diamond sheet 20; the copper-clad diamond copper plate 10 includes a diamond copper core 11 and a copper layer 12 located on the surface of the diamond copper core 11; the diamond copper core and the copper layer form a composite plate with a sandwich structure of copper layer - core - copper layer; the copper-clad diamond copper plate 10, the diamond sheet 20, and the first copper layer 30 are connected into one body by brazing. The diamond sheet serves as the core heat conduction layer, which can quickly conduct the heat generated by the electronic device from the first copper layer (upper surface) to the bottommost copper layer, forming an efficient heat conduction path. This structure makes full use of the high thermal conductivity of diamond. The upper and lower copper layers serve as the lateral heat diffusion layers, quickly dispersing the heat conducted out by the diamond sheet to the edge of the radiator, avoiding local overheating, and significantly improving the overall heat dissipation efficiency of the heat dissipation substrate; and the diamond sheet serves as the reinforcing phase, which can significantly improve the mechanical properties of the heat dissipation substrate. There are bonding interface layers between the surface of the diamond sheet and the first copper layer and between the lower surface of the diamond sheet and the copper layer on the upper surface of the copper-clad diamond copper plate. The bonding interface layer between the diamond sheet and the copper layer is formed by a sintering process, realizing the chemical bonding or physical embedding of copper atoms on the surface of the diamond. The interface bonding reduces the interfacial thermal resistance during the heat conduction process, ensuring that heat can be smoothly transferred between the copper layer and the diamond substrate, and further improving the heat dissipation performance. In some embodiments of the present application, the thickness range of the copper-clad diamond copper plate is 0.8 - 5 mm, the thickness range of the diamond sheet is 0.2 - 0.6 mm, and the thickness of the first copper layer is 0.1 - 1 mm.

[0029] The copper-clad diamond copper plate comprises a diamond copper core material and a copper layer on the surface of the diamond copper core material. The thermal conductivity of diamond is 4-5 times that of copper. It can quickly conduct the heat generated by electronic devices like a super heat conduction channel, effectively avoiding problems such as performance degradation and reduced reliability of electronic devices due to excessive temperature. Its coefficient of thermal expansion is relatively matched with that of semiconductor materials (such as silicon), which can reduce thermal stress and the risks of deformation and cracking of packaging materials. Diamond has extremely high hardness and strength. In a limited space, it can both provide support and protection for the chip and ensure the spacing and connection stability between chips in a high-density assembly environment are not affected by temperature fluctuations due to its low coefficient of thermal expansion. The diamond copper composite material forms an efficient heat conduction network through the uniform dispersion of diamond particles or fibers in the copper matrix. The mechanical properties of the diamond copper composite material can be significantly improved compared to copper-based materials, enabling the material to withstand greater mechanical stress and impact and improving the reliability of the device. In a preferred embodiment, the core material described in this application uses diamond or diamond copper composite material.

[0030] In some embodiments, the copper-clad diamond copper plate is a composite material sintered from a hexahedral copper foil shell and at least one diamond-copper composite layer placed in the copper foil shell. Using the hexahedral copper foil shell forms a six-sided coating structure on the surface of the diamond-copper composite layer, forming a dense shell to block the penetration of oxygen and water vapor. The wettability between copper and diamond is poor, relying on high-cost coatings and having a high interfacial thermal resistance. The copper foil shell and the internal copper mesh diffuse synergistically during sintering, which can effectively reduce the interfacial thermal resistance. Due to the large difference in the coefficient of thermal expansion (CTE) between copper and diamond, the material is prone to thermal stress cracking during traditional composite processing. In the embodiments of this application, the diamond-copper composite layer includes a copper mesh and diamond particles coated with a coating. The diamond particles are arranged in the grids of the copper mesh, and the voids between the grids and the diamond particles are filled with copper powder. Through this scheme combining the copper mesh skeleton and copper powder filling, the adjustment of the coefficient of thermal expansion can be achieved, making it nearly match the coefficient of thermal expansion of electronic components such as semiconductors and chips. The copper foil shell and copper powder filling reduce the sintering temperature to avoid diamond graphitization, reduce energy consumption, and improve the yield. In the embodiments of this application, during the sintering process, Cu atoms in the copper mesh will diffuse through the coating to the surface of the diamond, forming a mixed transition zone. The thermal conductivity of traditional materials is significantly anisotropic and difficult to meet the demand for directional heat dissipation. In the embodiments of this application, the copper foil shell and the internal copper mesh-copper powder form a three-dimensional interpenetrating structure, which can effectively improve the thermal conductivity and isotropy of the composite material.

[0031] Further, the grid described in the present application is a regular hexahedral structure or a regular octahedral honeycomb structure, the wall thickness of the grid is 10-20 μm, and the edge length L of the grid is 10-20 μm larger than the particle size D of a single diamond particle. In some embodiments, the grid is a regular hexahedral structure, and the regular hexahedral grid forms a homogeneous copper skeleton in the three directions of X / Y / Z. The regular arrangement of the copper mesh wire diameter and the grid edge length can reduce the isotropic deviation of thermal conductivity; the 90° intersection structure of the regular hexahedral grid forms a four-way support when bent (such as bending resistance test), which is conducive to improving the stress dispersion efficiency; the right-angled edges of the regular hexahedral grid can also guide the molten copper powder to flow along the edge direction during sintering, and can preferentially wrap the surface of the diamond particles; in addition, the regular porosity of the regular hexahedral structure allows the copper powder to be fully densified at a lower temperature to avoid local unmelted areas. When diamond particles are embedded in the grid through a vibration arrangement machine, a gap needs to be reserved to compensate for the particle size tolerance and arrangement mechanical error, to avoid particles getting stuck or scratching the surface of the copper mesh; at the same time, the gap can also provide a flow channel for copper powder. During the vibration process, copper powder can penetrate into the micro-gap between the particles and the grid wall, increase the interface contact area, and form a "diamond-copper powder-copper mesh" three-phase cross-linked structure. Due to the limited flow of copper melt and incomplete interface bonding, the reserved gap allows the copper powder to fully wrap the diamond particles during sintering and melting, and the copper atoms diffuse along the coating on the surface of the particles to form a transition layer, providing interface integrity. The thermal expansion mismatch between diamond (CTE≈2.5 ppm / K) and copper (CTE≈17 ppm / K) will generate stress at the interface; the gap can absorb the stress generated at the interface due to the thermal expansion mismatch between diamond and copper through plastic deformation of copper powder, avoiding stress concentration and microcracks. In addition, the shrinkage rates of copper powder and copper mesh are different during sintering, and the gap provides deformation buffer space, stabilizes the shrinkage rate, and avoids delamination or warping. Therefore, in some embodiments of the present application, the spatial size of each grid is slightly larger than the particle size of the placed diamond particles. Specifically, through precise calculation, when the edge length L of the grid is 10~20μm larger than the particle size D of a single diamond particle (L=D+10~20μm), the particle positioning accuracy, interface bonding strength and process tolerance can be effectively balanced. In the present application, the wall thickness of the grid is 10~20μm. In addition to the above-mentioned cube structure, in other embodiments, the grid is a regular octahedral honeycomb structure. When subjected to multi-directional loads, the stress distribution is uniform and has a higher compressive strength than the cube structure. When under pressure, the energy is absorbed by the buckling of the wall panel, and the energy absorption efficiency is higher than that of the cube structure; however, in the process of making the grid, the regular octahedral honeycomb structure is more difficult than the regular hexahedron, so the grid of the copper mesh in the present application is preferably a regular hexahedron.

[0032] Based on the above solutions, further, in some embodiments of the present application, the copper layer thickness at the bottom of the copper foil housing is greater than the copper layer thickness of the upper surface cover. In this solution, increasing the thickness of the bottom copper layer (lower surface) utilizes the plastic deformation ability of copper to absorb more thermal stress and reduce the peak value of interface stress; a "flexible buffer zone" is formed on the side of the thick bottom copper layer, making the thermal stress distribution gradient decay from the diamond-copper interface to the outside of the copper layer, avoiding stress concentration. In the packaging of electronic devices, heat mainly transfers from the copper layer of the upper cover on the electronic device side to the bottom copper layer on the radiator side. Increasing the thickness of the bottom copper layer can expand the lateral heat diffusion area, reduce the heat flux density, and lower the overall thermal resistance of the substrate. Thickening the bottom can also offset the warping tendency caused by the CTE difference at the diamond-copper interface and can withstand higher brazing pressures, avoiding local collapse of the thin copper layer during welding. In addition, increasing the thickness of the bottom copper layer can also be used to fabricate a heat sink with a topological structure. Compared with the existing heat sink structure, the thermal interface layer can be omitted, improving the heat conduction efficiency. Preferably, the thickness of the bottom copper layer is 1.2 to 2 times that of the copper layer of the upper surface cover.

[0033] In a preferred solution, in some embodiments, the coating on the surface of the diamond particles is a coating formed by one of the materials Ti, Cr, W, V, Zr or a composite coating formed by two or more materials; the thickness of the coating is 0.1 to 0.5 μm. For example, in some embodiments, Ti is used as the target, and a dense layer is formed on the diamond surface by magnetron sputtering, and a TiC phase is generated at the interface, with a thickness of about 100 nm. In other embodiments, the Ti and Cr targets are sputtered simultaneously to achieve an atomic-level hybrid coating to improve the interface shear strength. In still other embodiments, a composite layer of multiple materials can be used. For example, a Cr layer (0.2 - 0.3 μm) is first formed on the diamond particle surface by magnetron sputtering, and then a W layer (0.1 - 0.2 μm) is formed on the surface of the Cr layer. In some embodiments, it can be set as a Ti-Zr-Cu gradient coating, that is, the bottom layer is a 0.1 - 0.2 μm Ti layer, which reacts with the diamond at the interface to generate TiC to enhance the bonding; the intermediate layer is a 0.1 - 0.2 μm Zr layer, using the high melting point of the intermediate layer to achieve the transition of the thermal expansion coefficient; the surface layer is a 0.2 - 0.3 μm Cu layer to optimize the wettability of the diamond surface. In addition to the above several implementation methods, it can also be Ti / V alternating deposition, with each layer thickness of 20 - 50 nm and the total coating thickness of 0.5 μm.

[0034] Preferably, in some embodiments of the present application, the upper and lower surfaces of the diamond wafer are coated with a metal coating, and the thickness of the metal coating is 50 - 300 nm; the material of the metal coating is one of chromium, titanium, tungsten, molybdenum, and tantalum. Metals or metal carbides in the surface coating of the diamond wafer react with the diamond / carbon material to form covalent bonds, which can improve the wettability between the metal and the diamond, enhance the interfacial bonding strength, and at the same time reduce the thermal damage of the diamond wafer at high temperatures.

[0035] Preferably, in some embodiments of the present application, a layer of copper-containing active solder is coated on the surface of the metal coating. In the present application, the copper-containing active solder is one of Cu - Sn - Cr, Ag - Cu - Cr, Cu - Sn - Ti, and Ag - Cu - Ti, and the thickness of the brazing layer is 50 - 300 μm. The copper layer forms a Cu - Sn or Cu - Ag eutectic phase to achieve metallurgical bonding and improve the shear strength of the material. Specifically, the copper-containing active solder can be selected from, but not limited to, one of Cu - Sn - Cr, Ag - Cu - Cr, Cu - Sn - Ti, and Ag - Cu - Ti, and the thickness of the brazing layer is 50 - 300 μm.

[0036] The embodiments of the present application also provide a processing technology for an electronic packaging heat dissipation substrate. By combining sintering and brazing welding, a layered heat dissipation substrate is obtained, reducing the risks of peeling and cracking, and at the same time solving the problem of low heat transfer efficiency. The processing technology includes the following steps: Surface treatment of the diamond wafer: A metal coating is deposited on the upper and lower surfaces of the surface-activated diamond wafer by magnetron sputtering; then a layer of copper-containing active brazing solder is coated on the metal coating to obtain the surface-treated diamond wafer; Preparation of copper-clad diamond copper plate: 1) Punch and fold a copper foil sheet into a hexahedral copper foil box body with an upper cover and an opening, and place it in a mold; 2) Lay a copper mesh with a uniform grid in the above-mentioned hexahedral copper foil box body, and use an arrangement machine to arrange diamond particles coated with a coating on each grid of the copper mesh; 3) Place the hexahedral copper foil box body arranged with diamond particles and the mold on a vibrating table, and spray copper powder onto the copper mesh in the vibration mode until the copper powder fills the voids of the copper mesh and reaches the same height as the copper mesh; 4) Place another copper mesh in the hexahedral copper foil box body, and repeat steps 2) and 3) until the copper mesh is flush with the height of the hexahedral copper foil box body; 5) Cover the upper cover at the opening and combine the upper cover with the copper foil box body to obtain a preform; 6) Place the preform in a vacuum sintering furnace for sintering to obtain a sintered copper-clad composite plate; Brazing connection: Place the copper-clad diamond copper plate, the surface-treated diamond wafer, and the copper sheet for forming the first copper layer into a fixture in sequence and fasten them, then place them in a vacuum brazing furnace for vacuum brazing to obtain an electronic packaging heat dissipation substrate.

[0037] As a further preferred solution, in the processing technology described in the embodiments of the present application, the surface treatment steps of the diamond sheet include: Surface activation: Alternately ultrasonic clean the diamond sheet with 5wt% NaOH and 10wt% HCl solutions for 8 - 12 min (while removing surface impurities and improving surface wettability), then rinse it with pure water and dry it.

[0038] Magnetron sputtering of a metal coating: Place the surface-activated diamond sheet in a graphite mold for magnetron sputtering to form a metal coating, ensuring that the sputtering area is flat and unobstructed. Preferably, in the embodiments of the present application, in the surface treatment steps of the diamond sheet, a metal coating is deposited on the surface of the diamond sheet by magnetron sputtering as an interface strengthening layer. The thickness of the interface strengthening layer affects the bonding strength and thermal conductivity of the interface layer. If it is too thin, it cannot effectively cover the defects on the surface of the core material, and if it is too thick, it will introduce additional stress or reduce the heat conduction efficiency. Therefore, in order to ensure that the continuous and dense coating covers the diamond surface defects and prevent the penetration of the copper melt to form a brittle phase; at the same time, to inhibit the risk of interface peeling caused by the accumulation of internal stress induced by an overly thick coating, in a specific embodiment, the sputtering conditions are: DC sputtering power 120 - 180 W, sputtering time 1 - 3 h, target-substrate distance 5 - 10 cm, argon gas flow rate 15 - 25 sccm, vacuum degree <5×10 -3 Pa; the thickness of the interface strengthening layer is 50 - 300 nm.

[0039] Heat treatment: The diamond sheet after forming the metal coating is vacuum annealed at 400 - 600 °C for 1 - 2 h; the purpose of the heat treatment is to promote element diffusion to form carbides and enhance the interface bonding strength.

[0040] Acid etching treatment: After the annealing is completed, the diamond sheet is etched with 30 - 50 vol% nitric acid solution for 30 - 60 min to remove the unreacted layer and expose the active interface.

[0041] As a further preferred solution, in the processing technology described in the embodiments of the present application, when preparing the copper-clad diamond copper plate, during vacuum sintering, the vacuum degree will affect the content of residual gases, and further affect the oxidation and impurity problems during the sintering process. For example, under low-vacuum conditions, the residual oxygen content causes copper to oxidize to form Cu2O / CuO, which will reduce the thermal conductivity of the composite plate; when the vacuum degree is high, the oxygen content is low, which can inhibit the oxidation reaction, a continuous transition layer can be formed at the Cu / C interface, the thermal conductivity is improved, and the shear strength of the bonding interface also increases accordingly, but a high vacuum degree may increase the equipment requirements and operation difficulty; therefore, in order to ensure material purity and interface bonding, while taking into account cost and operation difficulty, the vacuum degree in the vacuum sintering furnace is controlled to 10 -1 ~10 -3Pa. During the vacuum sintering process, the heating rate significantly affects the properties of the material. Too fast heating may cause thermal stress and generate cracks inside the material, while too slow heating may affect production efficiency. Therefore, to ensure uniform heating of the material, avoid defects, and control the grain growth rate, during the heating process, the heating rate is controlled at 5 - 20 °C / min, and the temperature is raised from room temperature to 900 - 1100 °C. The holding time affects the diffusion of atoms and the interfacial reaction. Too short a time may lead to incomplete sintering, and too long a time may cause excessive grain growth and affect the material properties. Therefore, to ensure sufficient diffusion between atoms without damaging the material structure, the holding time is controlled at 20 - 120 min. During vacuum sintering, the pressure affects the density and interfacial bonding of the material. Insufficient pressure may result in many pores and low density; too high pressure may damage the diamond structure, especially for brittle materials. In the embodiments of the present application, the applied pressure is controlled at 20 - 50 MPa.

[0042] As a further preferred solution, in the processing technology of the embodiments of the present application, in the brazing welding step, vacuum brazing is used, and the vacuum degree is 10 -1 ~10 -5 Pa. During the brazing process, if the temperature is too low, the filler metal is not completely melted and insufficient temperature leads to the residue of unmelted particles; but if the temperature is too high, Ti reacts with the base material at high temperature to form a brittle layer, and the bending strength decreases. Therefore, to cover the liquidus line of the filler metal and promote interfacial diffusion, meet the requirements of densification, and at the same time inhibit the formation of harmful phases, in the embodiments of the present application, the temperature is raised to 700 - 900 °C at a rate of 5 - 10 °C / min, held for 30 - 60 min, and pressurized to 0.1 - 10 MPa while holding. In this solution, the heating rate and the holding time are in a positive correlation. A high heating rate requires an extended holding time to eliminate closed pores.

[0043] The embodiments of the present application also provide an application of the electronic packaging heat dissipation substrate in manufacturing a chip packaging radiator.

[0044] Example 1

[0045] As Figure 1 shown, this embodiment provides an electronic packaging heat dissipation substrate, which includes a copper - clad diamond copper plate 10, a diamond sheet 20 located on the copper - clad diamond copper plate 10, and a first copper layer 30 covering the diamond sheet 20; the copper - clad diamond copper plate 10 includes a diamond copper core 11 and a copper layer 12 located on the surface of the diamond copper core 11; the diamond copper core 11 and the copper layer 12 form a composite plate with a copper layer - core - copper layer sandwich structure; the copper - clad diamond copper plate 10, the diamond sheet 20, and the first copper layer 30 are connected into one body by brazing. The processing technology of the electronic packaging heat dissipation substrate includes the following steps. Surface treatment of diamond wafers: 1) Surface activation: Alternately ultrasonic clean the diamond wafers (with a thickness of 0.2 mm) with 5 wt% NaOH and 10 wt% HCl solutions for 10 min to remove surface impurities, then rinse with pure water and dry; 2) Magnetron sputter a Ti metal coating: Place the surface-activated diamond wafers in a graphite mold and magnetron sputter to form a Ti coating with a thickness of 200 nm, ensuring that the sputtering area is flat and unobstructed. The sputtering conditions are: DC sputtering power of 150 W, sputtering time of 2 h, target-substrate distance of 5 cm, argon gas flow rate of 20 sccm, and vacuum degree of 1.2×10 -3 Pa; 3) Heat treatment: Anneal the diamond wafers with the metal coating in vacuum at 500 °C for 2 h; 4) Acid etching treatment: After the annealing is completed, etch the diamond wafers with a 45 vol% nitric acid solution for 40 min to remove the unreacted layer and expose the active interface; obtain diamond wafers with a metal coating on the surface; 5) Coat the surface of the metal coating with an Ag-Cu-Cr solder with a thickness of 100 μm to obtain the surface-treated diamond wafers; Preparation of copper-clad diamond copper plates: 1) Stamp out the developed shape of a hexahedron on a copper foil with a thickness of 250 μm and reserve creases at the edges; Bond the edges of the copper foil with the developed shape using a metal adhesive to form a copper foil box body with an upper cover and an open upper surface; Place the copper foil box body with the open upper surface into a graphite mold, and lay a copper mesh with a uniform grid in the above-mentioned hexahedron copper foil box body. The grid wall thickness is 15 μm, and the edge length of the regular hexahedron is 15 μm larger than the particle size of the placed diamond particles. The size of the copper mesh plane is the same as the inner bottom surface of the copper foil box body; 2) Use an arrangement machine to arrange artificial CVD diamond particles with a 0.5 μm Ti coating in each grid of the copper mesh. The particle size of the diamond particles is 300 μm; 3) Place the hexahedron copper foil box body with the arranged diamond particles and the mold on a vibrating table. The vibration frequency is 10 Hz, the vibration time is 10 min, and the amplitude is controlled at 0.2 mm. Spray copper powder on the copper mesh in the vibration mode. The copper powder is a mixed copper powder mixed with nano-Al2O3. Among them, the dosage of nano-Al2O3 accounts for 0.5 wt% of the weight of the copper powder, and the particle size of the copper powder is 3 μm. Use electrostatic spraying technology to apply an electric field to make the copper powder directionally fill the grid gaps of the copper mesh until the copper powder fills the voids of the copper mesh and reaches the same height as the copper mesh; 4) Then place a copper mesh in the hexahedron copper foil box body and repeat steps 2) and 3) until the three layers of copper mesh are flush with the height of the hexahedron copper foil box body; 5) Cover the upper cover at the opening and combine the upper cover with the copper foil box body to obtain a preform; 6) Place the preform in a vacuum sintering furnace for sintering. The vacuum degree is 10 -3 Pa. During the heating process, heat up from room temperature to 950 °C at a rate of 15 °C / min, start pressurizing after holding for 60 min, the pressurizing pressure is 30 MPa, and keep the pressure and cool to room temperature; obtain the sintered copper-clad composite plate; Brazing connection: The copper-clad diamond copper plate, the diamond sheet after surface treatment, and the copper sheet (with a thickness of 0.3 mm) used to form the first copper layer are successively placed in a fixture and fastened, and then placed in a vacuum brazing furnace for vacuum brazing. The vacuum degree is 4×10 -3 Pa, heated to 830°C at a rate of 10°C / min, the brazing holding time is 30 min, and pressure is applied to 1 MPa while holding; the vacuum brazing furnace is cooled to room temperature to obtain an electronic packaging heat dissipation substrate.

[0046] Performance testing

[0047] The performance of the electronic packaging heat dissipation substrate obtained in the above Example 1 was detected. The detection items and results are shown in Table 1. Among them, the detection method of the comprehensive thermal conductivity (W·m -1 ·K -1 −1) is the heat flow meter method (ASTM E1225), the detection method of the coefficient of thermal expansion ( / °C) is based on the method in ASTM E228-17, and the detection method of the volume resistivity (25°C, Ω·cm) refers to ASTM-D257-14. The test results are shown in Table 1.

[0048] Table 1: Performance detection results of the electronic packaging heat dissipation substrate of Example 1

[0049] Furthermore, in order to explore the influence of the metal coating on the surface of the diamond sheet on the performance of the heat dissipation substrate, on the basis of the above Example 1, different metal coatings and different metal coating thicknesses were set, and other conditions were the same as those in Example 1. The specific parameter settings and performance detection results are shown in Table 2.

[0050] Table 2: Influence of the metal coating on the performance of the electronic packaging heat dissipation substrate

[0051] Furthermore, in order to explore the influence of the copper-containing active solder on the performance of the electronic packaging heat dissipation substrate, on the basis of the above Example 1, different copper-containing active solders and different solder coating thicknesses were used, and other conditions were the same as those in Example 1. The specific parameter settings and performance detection results are shown in Table 3.

[0052] Table 3: Influence of the type and thickness of the copper-containing active solder on the performance of the electronic packaging heat dissipation substrate

[0053] Furthermore, in order to explore the influence of the brazing temperature and holding time on the performance of the electronic packaging heat dissipation substrate, on the basis of the above Example 1, different brazing temperatures and holding times were used, and other conditions were the same as those in Example 1. The specific parameter settings and performance detection results are shown in Table 4.

[0054] Table 4: Influence of Brazing Temperature and Holding Time on the Properties of Metal Coatings

[0055] Comparative Example

[0056] The diamond wafer copper clad laminate and the copper clad diamond copper plate are connected together through a thermal interface material. The materials of the TIM thermal interface layer in the comparative example are respectively selected as thermal conductive gel, thermal conductive silicone grease, and thermal conductive gasket, and the comprehensive thermal conductivity is shown in Table 5.

[0057] Table 5: Detection Results of the Performance of the Heat Dissipation Substrate for Electronic Packaging in the Comparative Example

[0058] The above embodiments are only the preferred embodiments of the present invention, and the scope of protection of the present invention cannot be limited thereby. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. An electronic packaging heat dissipation substrate, characterized in that, It includes a copper-clad diamond copper plate, a diamond sheet located on the copper-clad diamond copper plate, and a first copper layer covering the diamond sheet; the copper-clad diamond copper plate includes a diamond copper core material and a copper layer on the surface of the diamond copper core material; the diamond copper core material and the copper layer form a composite plate with a sandwich structure of copper layer-core material-copper layer; the copper-clad diamond copper plate, the diamond sheet and the first copper layer are connected into one body by brazing.

2. The electronic packaging heat dissipation substrate according to claim 1, wherein The copper-clad diamond copper plate is a composite material sintered from a hexahedral copper foil shell and at least one diamond-copper composite layer placed in the copper foil shell; the diamond-copper composite layer includes a copper mesh and diamond particles coated with a coating on the surface, the diamond particles are arranged in the meshes of the copper mesh, and copper powder is filled in the gaps between the meshes and the diamond particles; Cu atoms in the copper mesh diffuse towards the diamond surface through the coating to form a mixed transition zone.

3. The electronic packaging heat dissipation substrate according to claim 2, wherein, The mesh is a regular hexahedron structure or a honeycomb structure of a regular octahedron, the wall thickness of the mesh is 10 - 20μm, and the edge length L of the mesh is 10 - 20μm larger than the particle size D of a single diamond particle.

4. The electronic packaging heat dissipation substrate according to claim 2, characterized in that, The thickness of the copper layer at the bottom of the copper foil shell is greater than the thickness of the copper layer covering the surface.

5. The electronic packaging heat dissipation substrate according to claim 2, characterized in that The coating on the surface of the diamond particles is a coating formed by one of the materials Ti, Cr, W, V, Zr or a composite coating formed by two or more materials; the thickness of the coating is 0.1 - 0.5μm.

6. The electronic packaging heat dissipation substrate according to any one of claims 1-5, characterized in that Metal coatings are plated on the upper and lower surfaces of the diamond sheet, and the thickness of the metal coating is 50 - 300nm; the material of the metal coating is one of metal chromium, titanium, tungsten, molybdenum, tantalum.

7. The electronic packaging heat dissipation substrate according to claim 6, wherein A copper-containing active solder is coated on the surface of the metal coating to form a brazing layer, the copper-containing active solder is one of Cu - Sn - Cr, Ag - Cu - Cr, Cu - Sn - Ti, Ag - Cu - Ti, and the thickness of the brazing layer is 50 - 300μm.

8. A processing technology for an electronic packaging heat dissipation substrate as described in any one of claims 1-7, characterized in that, It includes the following steps Surface treatment of the diamond sheet: A metal coating is plated on the upper and lower surfaces of the surface-activated diamond sheet by magnetron sputtering; then a copper-containing active brazing is coated on the metal coating to obtain the surface-treated diamond sheet. Preparation of the copper-clad diamond copper plate: 1) Stamp and fold a copper foil sheet into a hexahedral copper foil box body with a lid and an opening, and place it in a mold, and lay a copper mesh with uniform meshes in the above-mentioned hexahedral copper foil box body; 2) Use an arrangement machine to arrange diamond particles coated with a coating in each mesh of the copper mesh; 3) Place the hexahedral copper foil box body arranged with diamond particles and the mold on a vibrating table, and spray copper powder onto the copper mesh in the vibration mode until the copper powder fills the gaps of the copper mesh and reaches the same height as the copper mesh; 4) Place a copper mesh in the hexahedral copper foil box body again, and repeat 2) and 3) until the copper mesh is flush with the height of the hexahedral copper foil box body; 5) Cover the lid at the opening and combine the lid with the copper foil box body to obtain a preform; 6) Place the preform in a vacuum sintering furnace for vacuum sintering to obtain the sintered copper-clad diamond copper plate. Brazing connection: After sequentially placing the copper-clad diamond copper plate, the diamond sheet after surface treatment, and the copper sheet for forming the first copper layer into a fixture and fastening them, they are placed into a vacuum brazing furnace for vacuum brazing to obtain an electronic packaging heat dissipation substrate.

9. The processing technology according to claim 8, wherein, The surface treatment steps of the diamond sheet include: Surface activation: Alternately ultrasonic clean the diamond sheet with 5wt% NaOH and 10wt% HCl solutions for 8 - 12 min to remove surface impurities, then rinse with pure water and dry. Magnetron sputtered metal coating: Place the surface-activated diamond wafer in a graphite mold and magnetron sputter to form a metal coating, ensuring that the sputtering area is flat and unobstructed. The sputtering conditions are as follows: DC sputtering power is 120 - 180 W, sputtering time is 1 - 3 h, target-substrate distance is 5 - 10 cm, argon gas flow rate is 15 - 25 sccm, and vacuum degree is <5×10 -3 Pa; Heat treatment: The diamond sheet after forming the metal coating is vacuum annealed at 400 - 600 °C for 1 - 2 h. Acid etching treatment: After the annealing is completed, the diamond sheet is etched with 30 - 50 vol% nitric acid solution for 30 - 60 min to remove the unreacted layer and expose the active interface.

10. The processing technology according to claim 8, characterized in that, In the steps of preparing copper-clad diamond copper plates, the conditions for vacuum sintering are as follows: the vacuum degree is 10 -1 ~10 -3 Pa, during the heating process, the temperature is raised from room temperature to 900~1100°C at a rate of 5~20°C / min, pressurization starts after holding for 20~120 min, the pressurization pressure is 20~50 MPa, and it is cooled to room temperature under pressure holding.

11. The processing technology according to claim 8, characterized in that, In the brazing welding process, vacuum brazing is adopted, and the vacuum degree is 10 -1 ~10 -5 Pa. It is heated to 700~900°C at a rate of 5~10°C / min, held for 30~60 min, and pressurized to 0.1~10 MPa while holding the temperature.

12. Application of an electronic packaging heat dissipation substrate according to any one of claims 1 - 7 in manufacturing an electronic packaging heat sink.

13. An electronic packaging radiator, characterized in that, An electronic packaging heat dissipation substrate according to any one of claims 1 - 7 is included.

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