An electronic packaging heat dissipation substrate and its processing technology and application

Abstract

This application discloses an electronic packaging heat dissipation substrate, its processing technology, and application. 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 and a copper layer located on the surface of the diamond copper core. The diamond copper core and the copper layer form a composite plate with a copper layer-core-copper layer sandwich structure. The copper-clad diamond copper plate, the diamond sheet, and the first copper layer are integrally connected by brazing. The electronic packaging heat dissipation substrate described in this application can reduce the risk of peeling and cracking and address the issue of low heat transfer efficiency.

Description

Technical Field

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

[0002] Advances in semiconductor technology have greatly promoted the development and application of power electronic devices. Rapid advances in chip manufacturing processes have led to the rapid miniaturization and multifunctionality of IGBT power devices, which has posed a serious heat dissipation problem. Current IGBT power devices generate significant heat during operation. If heat is not dissipated promptly and effectively, it can lead to performance degradation or even damage. Therefore, thermal management of power devices is crucial. Thermal management primarily involves heat conduction, convection, and radiation to ensure that devices operate 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 → baseboard → thermally conductive silicone → heat sink → external environment.

[0003] Currently, heat transfer, conduction, and dissipation in heat sinks primarily occur within the DBC layer (ceramic copper-clad substrate), the copper substrate, and the heat sink. DBC ceramic substrates are heated at temperatures exceeding 1000°C in an oxygen-containing nitrogen atmosphere, creating a tight eutectic bond between the copper foil and the ceramic substrate. The typical process flow is as follows: cleaning and drying the ceramic substrate and copper foil → copper foil pretreatment → high-temperature eutectic bonding between the copper foil and ceramic substrate → hot and cold step-cycle cooling → quality inspection → pattern etching as required → electroless nickel (or gold) plating → quality inspection → laser scribing and cutting → finished product quality inspection → vacuum or nitrogen-filled packaging → storage. This technology provides high bond strength, excellent thermal conductivity, and thermal stability. Commonly used ceramic substrate materials include alumina (Al2O3), aluminum nitride (AlN), and zirconia-toughened alumina (ZTA). The core bonding method of this technology is eutectic bonding, which causes the oxygen in the copper foil to react chemically with the surface of the ceramic substrate at high temperature to form a layer of Cu-O-Al or Cu-ON compound, thereby achieving a strong connection between copper and ceramic. Thanks to the high eutectic bonding strength between the copper foil and the ceramic, the copper thickness of the DBC substrate can generally be adjusted to 100~600μm. The copper substrate is a common heat dissipation structure for power semiconductor modules in the traditional field. Its main function is to transfer the heat of the module to the outside and provide mechanical support for the module. The heat sink is mainly made of W and Mo (W has a thermal conductivity of 174Wm -1 K -1 、Mo thermal conductivity is 140Wm -1 K -1) as reinforcements. Furthermore, a high-thermal-conductivity thermal interface material (TIM), such as thermally conductive epoxy or silicone, is used to fill the gaps between the copper-clad ceramic substrate and the copper heat sink, and between the copper heat sink and the heat sink. Pressure is applied to solidify the gaps to ensure good thermal contact, bonding them together to form a complete heat-conducting structure.

[0004] Modern electronic packaging materials require not only high thermal conductivity, good thermal expansion coefficient and good mechanical properties; they also require light weight, excellent dielectric constant and good chemical stability. Traditional heat dissipation materials such as copper-tungsten alloy, alumina and aluminum nitride ceramic substrates can no longer meet the needs of modern electronic technology for heat dissipation materials. It is necessary to find advanced composite materials with high thermal conductivity and good thermal expansion coefficient as a replacement. Copper-clad diamond material is a composite material in which a copper layer is evenly covered on the surface of diamond particles or on a diamond matrix by physical or chemical methods. It combines the high thermal conductivity and high hardness of diamond with the electrical conductivity and ductility of copper, and shows significant advantages in the fields of electronic packaging, heat dissipation, precision machining, etc. The copper-clad diamond substrate materials currently on the market usually need to keep the thickness of the upper and lower copper layers consistent, at around 100μm; this is because diamond (thermal expansion coefficient: 0.8×10 -6 ) and copper (thermal expansion coefficient: 18×10 -6 The thermal expansion coefficients of the two materials differ significantly. An excessively thick copper layer will increase the difference in thermal expansion coefficients between copper and diamond, resulting in greater interfacial stress and increasing the risk of delamination or cracking. The thermal conductivity of air is very low, and 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, create a relatively large contact thermal resistance. While thermal interface material (TIM) can fill this air gap, reducing contact thermal resistance and improving heat dissipation performance, the significant difference in thermal conductivity between TIM and copper and diamond reduces heat transfer efficiency. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the purpose of the present application is to provide an electronic packaging heat dissipation substrate to reduce the risk of peeling and cracking, while solving the problem of low heat transfer efficiency.

[0006] To solve the above problems, the technical solutions adopted in this application are as follows:

[0007] An embodiment of the present application provides an electronic packaging heat dissipation substrate, comprising 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 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 to each other by brazing.

[0008] As a further preferred embodiment, the copper-clad diamond copper plate described in the embodiment of the present application is a composite material formed by sintering 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 grid of the copper mesh, and the gaps between the grid and the diamond particles are filled with copper powder; the Cu atoms in the copper mesh diffuse through the coating to the diamond surface to form a mixed transition zone.

[0009] As a further preferred solution, the grid described in the embodiment of the present application is a regular hexahedral structure or a regular octahedral honeycomb structure, the wall thickness of the grid is 10~20μm, and the edge length L of the grid is 10~20μm larger than the particle size D of a single diamond particle.

[0010] As a further preferred solution, the thickness of the copper layer at the bottom of the copper foil shell described in the embodiment of the present application is greater than the thickness of the copper layer on the surface.

[0011] As a further preferred solution, the coating on the surface of the diamond particles described in the embodiment of the present application is a coating formed by one material among Ti, Cr, W, V, and Zr, or a composite coating formed by two or more materials; the thickness of the coating is 0.1~0.5μm.

[0012] As a further preferred solution, the upper and lower surfaces of the diamond sheet described in the embodiment of the present application are coated with a metal coating, the thickness of the metal coating is 50-300nm; the material of the metal coating is one of metal chromium, titanium, tungsten, molybdenum, and tantalum.

[0013] As a further preferred embodiment, the surface of the metal coating described in the embodiment of the present application is coated with a layer of copper-containing active solder, 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 solder layer is 50~300μm.

[0014] Furthermore, the present invention also provides a process for processing an electronic packaging heat dissipation substrate, which combines sintering and brazing to obtain a layered heat dissipation substrate, reducing the risk of peeling and cracking, while solving the problem of low heat transfer efficiency. The process includes the following steps:

[0015] Diamond sheet surface treatment: A metal coating is applied to the upper and lower surfaces of the surface-activated diamond sheet using magnetron sputtering; a copper-containing active brazing layer is then applied to the metal coating to obtain a surface-treated diamond sheet;

[0016] Preparation of copper-clad diamond copper plate: 1) punching and folding a copper foil into a hexahedral copper foil box with an upper cover and an opening, placing the box into a mold, and laying a copper mesh with a uniform grid inside the hexahedral copper foil box; 2) using an arranging machine to arrange diamond particles coated on the surface in each grid of the copper mesh; 3) placing the hexahedral copper foil box with arranged diamond particles and the mold on a vibration table, spraying copper powder onto the copper mesh under vibration mode until the copper powder fills the gaps in the copper mesh and reaches the same height as the copper mesh; 4) placing the copper mesh inside the hexahedral copper foil box, repeating 2) and 3) until the copper mesh is flush with the height of the hexahedral copper foil box; 5) closing the upper cover at the opening, combining the upper cover and the copper foil box to obtain a preform; 6) placing the preform in a vacuum sintering furnace for sintering to obtain a sintered copper-clad diamond copper plate;

[0017] Brazing connection: Place the copper-clad diamond copper plate, the surface-treated diamond sheet, and the copper sheet used to form the first copper layer into the fixture in sequence and tighten them, then place them in a vacuum brazing furnace for vacuum brazing to obtain an electronic packaging heat dissipation substrate.

[0018] 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:

[0019] Surface activation: Use 5wt% NaOH and 10wt% HCl solutions to alternately ultrasonically clean the diamond sheet for 8-12 minutes to remove surface impurities, then rinse with pure water and dry.

[0020] Magnetron sputtering metal coating: Place the surface activated diamond sheet in a graphite mold and magnetron sputter to form a metal coating. Ensure that the sputtering area is flat and unobstructed. The sputtering conditions are: DC sputtering power 120-180W, sputtering time 1-3h, target-substrate distance 5-10cm, argon flow rate 15-25sccm, vacuum degree <5×10 -3 Pa;

[0021] Heat treatment: After forming the metal coating, the diamond sheet is vacuum annealed at 400~600℃ for 1~2h;

[0022] Acid etching: After annealing, 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.

[0023] 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 from room temperature to 900~1100℃ at a rate of 5~20℃ / min, and after keeping warm for 20~120min, pressurization is started, the pressurization pressure is 20~50MPa, and the pressure is maintained and cooled to room temperature.

[0024] As a further preferred solution, in the brazing step, vacuum brazing is used in the processing technology described in the embodiment of the present application, and the vacuum degree is 10 -1 ~10 -5 Pa, heat to 700~900℃ at 5~10℃ / min, keep warm for 30~60min, and pressurize to 0.1~10MPa at the same time.

[0025] As a further preferred solution, the electronic packaging heat dissipation substrate described in the embodiment of the present application can be used in multiple fields. For example, in the field of high-power laser diodes, it can be used for medical lasers, industrial cutting equipment, etc.; in the field of GaN RF amplifiers, it can be used for 5G base stations, radar systems, etc.; in the field of power electronic modules, it can be used for EV motor control, solar inverters, etc.; in the field of aerospace electronic equipment, it can be used for 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, cloud computing and big data centers, as well as for the manufacture of 5G / 6G base station GaN RF chips, electric vehicle SiC inverter modules and other devices; in the field of high-energy laser systems, it can be used to manufacture fiber laser pump couplers and solid laser crystal heat sinks; in the field of nuclear energy and fusion devices, it can be used to manufacture nuclear fusion reactor divertor target plates, plasma first walls, etc.; in the field of special power and energy equipment, it can be used to manufacture electromagnetic catapult system IGBT modules, high-voltage DC circuit breaker contacts, etc.; in the field of aerospace, it can be used for the beam spot area of ​​the electron focusing system and the periphery of the metal 3D printing laser melting pool; in the field of quantum and superconductivity, it can be used to manufacture superconducting quantum bit microwave resonant cavities and room-temperature superconducting transmission line connectors.

[0026] The embodiments of the present application also provide an application of an electronic packaging heat dissipation substrate in manufacturing an electronic packaging heat sink.

[0027] The embodiment of the present application further provides an electronic packaging heat sink, which includes the electronic packaging heat dissipation substrate described in the embodiment of the present application.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The electronic packaging heat dissipation substrate described in this application 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. This effectively forms a multilayer structure of copper layer-diamond sheet-copper layer-diamond copper layer-copper layer. The diamond substrate serves as the core heat conduction channel, combining with the upper and lower copper layers to form a longitudinal gradient heat conduction network. This fully leverages the thermal conductivity advantages of diamond and copper. Heat is rapidly transferred from the electronic device to the diamond substrate, where it then rapidly diffuses through the copper layer, significantly improving heat conduction efficiency and effectively reducing the operating temperature of the electronic device. This prevents performance degradation, shortened lifespan, or even damage caused by overheating, thereby ensuring stable and reliable operation of the electronic device. From a microscopic perspective, the bonding interface between the layers in the multilayer structure is achieved through chemical bonds formed by copper atoms reacting with atoms on the diamond surface during sintering, or through physical intercalation of copper atoms into tiny pores on the diamond surface. This dual bonding significantly enhances the bond strength between the copper layer and the diamond substrate.

[0030] 2. Furthermore, 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 in the electronic packaging heat dissipation substrate described herein are connected by welding. During the welding process, the high temperature causes the solder and the surface atoms of the copper layers of the two composite plates to diffuse, forming a metallurgical bond. This bonding method has high strength and can firmly connect the two dissimilar material layers together to form a single structure. The welded connection allows each layer of the two multi-layer structure to synergistically bear stress. When subjected to external forces, the stress is evenly distributed throughout the heat dissipation substrate. For example, during the chip packaging process, if the heat dissipation substrate is compressed or stretched, the welded connection ensures that the two composite plates share the stress, avoiding cracking caused by excessive local stress.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 This is a schematic diagram of the electronic packaging heat dissipation substrate structure described in an embodiment of the present application.

[0034] The reference numerals in the drawings are: 10, copper-clad diamond copper plate; 11, diamond copper core material; 12, copper layer; 20, diamond sheet; 30, first copper layer. DETAILED DESCRIPTION

[0035] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0036] The term "comprising" and other equivalent descriptions in the description and claims of this application are intended to cover non-exclusive inclusions, including not only the contents clearly described in the description and claims, but also the steps or units that are not described in the description and claims but are inherent in the product, method or structure.

[0037] like Figure 1 As shown, an embodiment of the present application provides an electronic packaging heat dissipation substrate, comprising 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 comprises 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 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 integrally connected by brazing. The diamond sheet serves as the core thermal conductive layer, rapidly transferring heat generated by electronic devices from the first copper layer (upper surface) to the bottommost copper layer, forming an efficient heat conduction path. This structure fully utilizes the high thermal conductivity of diamond. The upper and lower copper layers serve as lateral heat diffusion layers, rapidly dissipating heat conducted by the diamond sheet to the edge of the heat sink, preventing local overheating and significantly improving the overall heat dissipation efficiency of the heat dissipation substrate. The diamond sheet, acting as a reinforcing phase, significantly improves the mechanical properties of the heat dissipation substrate. A bonding interface layer exists between the surface of the diamond sheet and the first copper layer, as well as 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 through a sintering process, achieving chemical bonding or physical intercalation between the copper atoms and the diamond surface. This interfacial bonding reduces the interfacial thermal resistance during heat conduction, ensuring that heat can be smoothly transferred between the copper layer and the diamond substrate, further improving heat dissipation performance. In some embodiments of the present application, the thickness of the copper-clad diamond copper plate ranges from 0.8-5mm, the thickness of the diamond sheet ranges from 0.2-0.6mm, and the thickness of the first copper layer ranges from 0.1-1mm.

[0038] A copper-clad diamond copper plate comprises a diamond-copper core and a copper layer on the surface of the core. Diamond has a thermal conductivity 4-5 times that of copper, acting as a superheat-conducting channel to rapidly conduct heat generated by electronic devices, effectively preventing performance degradation and reduced reliability due to overheating. Its thermal expansion coefficient closely matches that of semiconductor materials (such as silicon), reducing thermal stress and lowering the risk of deformation and cracking in packaging materials. Diamond possesses exceptional hardness and strength, providing support and protection for chips within confined spaces. Its low thermal expansion coefficient ensures inter-chip spacing and connection stability in high-density assembly environments, despite temperature fluctuations. Diamond-copper composite materials form an efficient heat conduction network through the uniform dispersion of diamond particles or fibers within a copper matrix. The mechanical properties of diamond-copper composite materials are significantly improved compared to copper-based materials, enabling the material to withstand greater mechanical stress and impact, thereby enhancing device reliability. In preferred embodiments, the core material described herein is made of diamond or diamond-copper composite materials.

[0039] In some embodiments, the copper-clad diamond copper plate is a composite material formed by sintering a hexahedral copper foil shell and at least one diamond-copper composite layer within the copper foil shell. The hexahedral copper foil shell forms a six-sided cladding structure on the surface of the diamond-copper composite layer, forming a dense shell that blocks oxygen and water vapor penetration. The copper-diamond interface has poor wettability, requiring costly coatings and resulting in high interfacial thermal resistance. The synergistic diffusion between the copper foil shell and the internal copper mesh during sintering can effectively reduce interfacial thermal resistance. Due to the significant difference in the coefficient of thermal expansion (CTE) between copper and diamond, traditional composite processing techniques are prone to thermal stress cracking. The diamond-copper composite layer described in the present embodiment comprises a copper mesh and coated diamond particles. The diamond particles are arranged within the copper mesh grid, and the spaces between the mesh and the diamond particles are filled with copper powder. This combination of a copper mesh skeleton and copper powder filling allows for adjustment of the CTE to closely match that of electronic components such as semiconductors and chips. The copper foil shell and copper powder filling lower the sintering temperature, prevent diamond graphitization, reduce energy consumption, and improve yield. In the present embodiment, during the sintering process, Cu atoms in the copper mesh diffuse through the coating to the diamond surface, forming a mixed transition zone. Conventional materials exhibit significant anisotropy in thermal conductivity, making it difficult to meet the requirements for directional heat dissipation. In the present embodiment, the copper foil shell and the inner copper mesh-copper powder form a three-dimensional interpenetrating structure, effectively improving the thermal conductivity and isotropy of the composite material.

[0040] Furthermore, 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 grid edge length L 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 X / Y / Z directions. 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 in a bending test), which is conducive to improving 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, avoiding local unmelted areas. When diamond particles are embedded in the mesh using a vibrating placement machine, a gap is required to compensate for particle size tolerances and placement mechanical errors, preventing particles from getting stuck or scratching the copper mesh surface. The gap also provides a flow channel for copper powder. During the vibration process, copper powder can penetrate the micro-gaps between the particles and the mesh wall, increasing the interfacial contact area and forming a three-phase crosslinked structure of "diamond-copper powder-copper mesh." Because the copper melt's flow is restricted, interfacial bonding is incomplete. The gap allows the copper powder to fully encapsulate the diamond particles during sintering and melting. Copper atoms diffuse along the particle surface coating to form a transition layer, maintaining interfacial integrity. The thermal expansion mismatch between diamond (CTE ≈ 2.5 ppm / K) and copper (CTE ≈ 17 ppm / K) generates stress at the interface. The gap absorbs this stress through plastic deformation of the copper powder, preventing stress concentration and microcracks. Furthermore, the copper powder and copper mesh shrink at different rates during sintering. The gap provides a deformation buffer, stabilizing the shrinkage and preventing delamination or warping. Therefore, in some embodiments of the present application, the spatial size of each grid is slightly larger than the size of the diamond particles placed therein. Specifically, through precise calculation, a grid edge length L that is 10-20 μm larger than the particle size D of a single diamond particle (L = D + 10-20 μm) effectively balances particle positioning accuracy, interface bonding strength, and process tolerance. In the present application, the grid wall thickness is 10-20 μm. In addition to the aforementioned cubic grid structure, in other embodiments, the grid is an octahedral honeycomb structure. When subjected to multi-directional loads, the stress distribution is uniform and the compressive strength is higher than that of a cubic structure. When subjected to compression, the grid absorbs energy through wall buckling, resulting in a higher energy absorption efficiency than a cubic structure. However, the octahedral honeycomb structure is more difficult to produce than a hexahedron. Therefore, the copper mesh grid in this application is preferably a hexahedron.

[0041] In addition to the above solution, in some embodiments of the present application, the copper layer at the bottom of the copper foil housing is thicker than the copper layer on the surface. In this solution, increasing the thickness of the bottom copper layer (lower surface) leverages copper's plastic deformation to absorb more thermal stress and reduce peak interfacial stress. A "flexible buffer zone" forms on the side of the thick bottom copper layer, gradually attenuating the thermal stress distribution from the diamond-copper interface toward the outer side of the copper layer, thus avoiding stress concentration. In electronic device packaging, heat is primarily transferred from the copper layer on the electronic device side to the bottom copper layer on the heat sink side. Increasing the thickness of the bottom copper layer can expand the lateral heat diffusion area, reduce heat flux density, and lower the overall thermal resistance of the substrate. A thicker bottom layer can also offset the warping tendency of the diamond-copper interface due to CTE differences and withstand higher brazing pressures, preventing local collapse of the thin copper layer during soldering. Furthermore, increasing the thickness of the bottom copper layer can be used to create a heat sink with a topological structure. Compared to existing heat sink structures, this eliminates the need for a thermal interface layer and improves heat conduction efficiency. Preferably, the thickness of the bottom copper layer is 1.2 to 2 times that of the copper layer on the surface.

[0042] In a preferred embodiment, in some embodiments, the coating on the surface of the diamond particles is a coating formed by one material selected from Ti, Cr, W, V, and 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 a target material, and a dense layer is formed on the surface of the diamond by magnetron sputtering, and a TiC phase is generated at the interface with a thickness of about 100 nm. In other embodiments, Ti and Cr targets are sputtered simultaneously to achieve an atomic-level mixed coating to improve the interface shear strength. In 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 surface of the diamond particles 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, a Ti-Zr-Cu gradient coating can be used, with a bottom layer of 0.1-0.2μm Ti, which reacts with diamond at the interface to form TiC, enhancing bonding; a middle layer of 0.1-0.2μm Zr, which utilizes its high melting point to achieve a transition in thermal expansion coefficient; and a surface layer of 0.2-0.3μm Cu, which optimizes the wettability of the diamond surface. In addition to the aforementioned implementations, Ti / V can also be deposited alternately, with each layer 20-50nm thick, for a total coating thickness of 0.5μm.

[0043] Preferably, in some embodiments, the upper and lower surfaces of the diamond sheet described in the embodiments of the present application are coated with a metal coating having a thickness of 50-300 nm; the metal coating is made of one of chromium, titanium, tungsten, molybdenum, and tantalum. The metal or metal carbide in the diamond sheet surface coating reacts with the diamond / carbon material to form covalent bonds, which can improve the wettability between the metal and diamond, enhance the interfacial bonding strength, and reduce thermal damage to the diamond sheet at high temperatures.

[0044] Preferably, in some embodiments of the present application, the surface of the metal coating is coated with a layer of copper-containing active solder. 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 50~300μm. 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 50~300μm.

[0045] The present application also provides a processing technology for an electronic packaging heat dissipation substrate, which combines sintering and brazing to obtain a layered heat dissipation substrate, reducing the risk of peeling and cracking, while solving the problem of low heat transfer efficiency. The processing technology includes the following steps:

[0046] Diamond sheet surface treatment: A metal coating is applied to the upper and lower surfaces of the surface-activated diamond sheet using magnetron sputtering; a copper-containing active brazing layer is then applied to the metal coating to obtain a surface-treated diamond sheet;

[0047] Preparation of copper-clad diamond copper plate: 1) punching and folding a copper foil into a hexahedral copper foil box with an upper cover and an opening, and placing the box into a mold; 2) laying a copper mesh with a uniform grid inside the hexahedral copper foil box, and using an arranging machine to arrange diamond particles coated on the surface in each grid of the copper mesh; 3) placing the hexahedral copper foil box with arranged diamond particles and the mold on a vibration table, spraying copper powder onto the copper mesh under vibration mode until the copper powder fills the gaps in the copper mesh and reaches the same height as the copper mesh; 4) placing a copper mesh inside the hexahedral copper foil box, and repeating 2) and 3) until the copper mesh is flush with the height of the hexahedral copper foil box; 5) closing the upper cover at the opening, and integrating the upper cover with the copper foil box to obtain a preform; 6) placing the preform in a vacuum sintering furnace for sintering to obtain a sintered copper-clad composite board;

[0048] Brazing connection: Place the copper-clad diamond copper plate, the surface-treated diamond sheet, and the copper sheet used to form the first copper layer into the fixture in sequence and tighten them, then place them in a vacuum brazing furnace for vacuum brazing to obtain an electronic packaging heat dissipation substrate.

[0049] 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:

[0050] Surface activation: Use 5wt% NaOH and 10wt% HCl solutions to alternately ultrasonically clean the diamond sheet for 8-12 minutes (to remove surface impurities and improve surface wettability), then rinse with pure water and dry.

[0051] Magnetron sputtering metal coating: The surface activated diamond sheet is placed in a graphite mold and magnetron sputtered to form a metal coating, ensuring that the sputtering area is flat and unobstructed. Preferably, in the embodiment of the present application, in the surface treatment step of the diamond sheet, a metal coating is plated 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, while 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 surface defects of the diamond and avoid the infiltration of the copper melt to form a brittle phase; at the same time, suppress the risk of interface peeling caused by the accumulation of internal stress caused by the excessively thick coating, in a specific embodiment, the sputtering conditions are: DC sputtering power 120-180W, sputtering time 1-3h, target-substrate distance 5-10cm, argon flow rate 15-25sccm, vacuum degree <5×10 -3 Pa; the thickness of the interface strengthening layer is 50~300nm.

[0052] Heat treatment: After forming the metal coating, the diamond sheet is vacuum annealed at 400~600℃ for 1~2h; the purpose of heat treatment is to promote element diffusion to form carbides and enhance the interface bonding strength.

[0053] Acid etching: After annealing, 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.

[0054] As a further preferred solution, in the processing technology described in the embodiment of the present application, during the step of preparing the copper-clad diamond copper plate, during vacuum sintering, the vacuum degree will affect the content of residual gas, and thus 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; at high vacuum, the oxygen content is low, which can inhibit the oxidation reaction, and a continuous transition layer can be formed at the Cu / C interface, thereby improving the thermal conductivity and increasing the shear strength of the bonding interface accordingly. However, high vacuum may increase the equipment requirements and the difficulty of operation; therefore, in order to ensure the purity of the material and the interface bonding, while taking into account the cost and the difficulty of operation, the vacuum degree in the vacuum sintering furnace is controlled to be 10 -1 ~10 -3 Pa. During the vacuum sintering process, the rate of heating has a significant impact on the performance of the material. Heating too quickly may cause thermal stress and cracks inside the material, while heating too slowly may affect production efficiency. Therefore, in order to heat the material evenly and avoid defects while controlling the rate of grain growth, the heating rate is controlled at 5~20℃ / min during the heating process, from room temperature to 900~1100℃. The holding time affects the diffusion of atoms and interface reactions. Too short a time may lead to incomplete sintering, while too long a time may cause excessive grain growth, affecting material properties. Therefore, in order to ensure sufficient diffusion between atoms without damaging the structure of the material, the holding time is controlled to 20~120min. During vacuum sintering, the pressure affects the density and interface bonding of the material. Insufficient pressure may result in more pores and low density. Excessive pressure may damage the diamond structure, especially brittle materials. In the embodiments of the present application, the pressurization pressure is controlled to 20~50MPa.

[0055] As a further preferred solution, in the brazing step, vacuum brazing is used in the processing technology described in the embodiment of the present application, and the vacuum degree is 10 -1 ~10 -5 Pa. During the brazing process, if the temperature is too low, the brazing filler metal is not completely melted and the temperature is insufficient, resulting in residual 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, in order to cover the liquidus line of the brazing filler metal and promote interface diffusion, meet the densification requirements, and suppress the generation of harmful phases, in the embodiment of the present application, the temperature is raised to 700~900℃ at 5~10℃ / min, kept warm for 30~60min, and pressurized to 0.1~10MPa while keeping warm. In this scheme, the heating rate is positively correlated with the holding time, and a high heating rate requires a longer holding time to eliminate closed pores.

[0056] The embodiments of the present application also provide an application of an electronic packaging heat dissipation substrate in manufacturing a chip packaging heat sink.

[0057] Example 1

[0058] like Figure 1 As shown, this embodiment provides an electronic packaging heat dissipation substrate, including 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 material 11 and a copper layer 12 located on the surface of the diamond copper core material 11; the diamond copper core material 11 and the copper layer 12 form a composite plate with a sandwich structure of copper layer-core material-copper layer; the copper-clad diamond copper plate 10, the diamond sheet 20 and the first copper layer 30 are connected to each other by brazing. The electronic packaging heat dissipation substrate processing process includes the following steps:

[0059] Diamond wafer surface treatment: 1) Surface activation: Alternate ultrasonic cleaning of diamond wafers (0.2 mm thick) with 5 wt% NaOH and 10 wt% HCl solutions for 10 min to remove surface impurities, followed by rinsing with pure water and drying; 2) Magnetron sputtering of Ti metal coating: The surface-activated diamond wafers were placed in a graphite mold and magnetron sputtered to form a 200 nm thick Ti coating. The sputtering area was ensured to be flat and unobstructed. The sputtering conditions were: DC sputtering power 150 W, sputtering time 2 h, target-substrate distance 5 cm, argon flow rate 20 sccm, and vacuum degree 1.2 × 10 -3 Pa; 3) heat treatment: the diamond sheet after forming the metal coating was vacuum annealed at 500°C for 2 hours; 4) acid etching: after the annealing, the diamond sheet was etched with 45 vol% nitric acid solution for 40 minutes to remove the unreacted layer and expose the active interface; thus, a diamond sheet with a metal coating was obtained; 5) Ag-Cu-Cr solder with a thickness of 100 μm was applied to the surface of the metal coating to obtain a surface-treated diamond sheet;

[0060] Preparation of copper-clad diamond copper plate: 1) punching out a hexahedral unfolded shape on a copper foil with a thickness of 250 μm, and leaving creases at the edges; bonding the edges of the copper foil in the unfolded shape with metal adhesive to form a copper foil box with an upper cover and an open upper surface; placing the copper foil box with an open upper surface into a graphite mold, and laying a copper mesh with a uniform grid inside the hexahedral copper foil box, wherein the grid wall thickness is 15 μm, the edge length of the regular hexahedron is 15 μm larger than the particle size of the placed diamond particles, and the plane size of the copper mesh is the same as the bottom surface of the copper foil box; 2) using an arranging machine to arrange artificial CVD diamond particles with a 0.5 μm Ti coating in each grid of the copper mesh, wherein the diamond particle size is 300 μm; 3) placing the hexahedral copper foil box with the diamond particles arranged thereon and The mold is placed on a vibration table with a vibration frequency of 10 Hz, a vibration time of 10 minutes, and an amplitude controlled at 0.2 mm. Copper powder is sprayed onto the copper mesh in the vibration mode. The copper powder is a mixed copper powder mixed with nano-Al2O3, wherein the amount of nano-Al2O3 accounts for 0.5wt% of the weight of the copper powder and the copper powder particle size is 3μm. An electrostatic spraying technology is used to apply an electric field to directionally fill the copper powder into the grid gaps on the copper mesh until the copper powder fills the gaps in the copper mesh and reaches the same height as the copper mesh; 4) a copper mesh is then placed in the hexahedral copper foil box, and steps 2) and 3) are repeated until the three layers of copper mesh are flush with the height of the hexahedral copper foil box; 5) an upper cover is placed on the opening, and the upper cover and the copper foil box are integrated to obtain a preform; 6) the preform is placed in a vacuum sintering furnace for sintering, and the vacuum degree is 10 -3 Pa, the heating process is heated from room temperature to 950 ° C at a rate of 15 ° C / min, and after keeping the temperature for 60 minutes, pressurization is started, the pressurization pressure is 30 MPa, and the pressure is maintained and cooled to room temperature; a sintered copper clad composite board is obtained;

[0061] Brazing connection: Place the copper-clad diamond copper plate, the surface-treated diamond sheet, and the copper sheet (thickness 0.3 mm) used to form the first copper layer into the fixture in sequence and tighten them. Then place them in a vacuum brazing furnace for vacuum brazing. The vacuum degree is 4×10 -3 Pa, and heated to 830 ° C at 10 ° C / min, and the brazing holding time was 30 min, while the pressure was increased to 1 MPa; the vacuum brazing furnace was cooled to room temperature to obtain an electronic packaging heat dissipation substrate.

[0062] Performance Testing

[0063] The performance of the electronic packaging heat dissipation substrate obtained in Example 1 was tested. The test items and results are shown in Table 1. The comprehensive thermal conductivity (W·m -1 ·K -1) was tested using the heat flow meter method (ASTM E1225), the coefficient of thermal expansion ( / °C) was tested according to ASTM E228-17, and the volume resistivity (25°C, Ωcm) was tested according to ASTM-D257-14. See Table 1 for test results.

[0064] Table 1: Performance test results of the electronic packaging heat dissipation substrate of Example 1

[0065]

[0066] Furthermore, in order to explore the effect of the metal coating on the surface of the diamond sheet on the performance of the heat dissipation substrate, different metal coatings and different metal coating thicknesses were set on the basis of the above-mentioned Example 1. Other conditions were consistent with Example 1. The specific parameter settings and performance test results are shown in Table 2.

[0067] Table 2: Effect of metal coating on the performance of electronic packaging heat dissipation substrate

[0068]

[0069] Furthermore, in order to explore the effect of copper-containing active solder on the performance of the electronic packaging heat dissipation substrate, on the basis of the above-mentioned Example 1, different copper-containing active solders and solder coatings of different thicknesses were used. Other conditions were consistent with Example 1. For specific parameter settings and performance test results, please refer to Table 3.

[0070] Table 3: Effect of copper-containing active solder type and thickness on the performance of electronic packaging heat dissipation substrate

[0071]

[0072] Furthermore, in order to explore the influence of soldering temperature and holding time on the performance of the electronic packaging heat dissipation substrate, different soldering temperatures and holding times were adopted on the basis of the above-mentioned Example 1. Other conditions were consistent with those in Example 1. For specific parameter settings and performance test results, see Table 4.

[0073] Table 4: Effect of brazing temperature and holding time on metal coating properties

[0074]

[0075] Comparative Example

[0076] The diamond-clad copper plate and the copper-clad diamond-clad copper plate were connected together through a thermal interface material. The materials for the comparative TIM thermal interface layer were thermally conductive gel, thermally conductive silicone grease, and thermally conductive pads, respectively. The comprehensive thermal conductivity is shown in Table 5.

[0077] Table 5: Comparative Example Electronic Packaging Heat Dissipation Substrate Performance Test Results

[0078]

[0079] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of 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: The invention 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 is a composite material sintered by a hexahedral copper foil shell and at least one diamond-copper composite layer placed in the copper foil shell; the diamond-copper composite layer comprises a copper mesh and diamond particles coated with a coating on the surface; the mesh is a regular hexahedral structure or a regular octahedral honeycomb structure, the wall thickness of the mesh is 10-20 μm, and the edge length L of the mesh is larger than the particle size of a single diamond particle. D is greater than 10-20 μm; the coating on the surface of the diamond particles is a coating formed of one material selected from 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; the diamond particles are arranged in a grid of a copper mesh, and the gaps between the grid and the diamond particles are filled with copper powder; Cu atoms in the copper mesh diffuse through the coating to the diamond surface, forming a mixed transition zone; the copper-clad diamond copper plate is integrally connected to the diamond sheet and the first copper layer by brazing.

2. The electronic packaging heat dissipation substrate according to claim 1, 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 on the surface.

3. The electronic packaging heat dissipation substrate according to any one of claims 1 or 2, characterized in that: The upper and lower surfaces of the diamond sheet are plated with a metal coating, the thickness of the metal coating is 50-300nm; the material of the metal coating is one of metal chromium, titanium, tungsten, molybdenum and tantalum.

4. The electronic packaging heat dissipation substrate according to claim 3, characterized in that The surface of the metal coating is coated with a layer of copper-containing active solder to form a brazing layer, wherein 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.

5. A processing technology for an electronic packaging heat dissipation substrate according to any one of claims 1 to 4, characterized in that: The following steps are included: Diamond sheet surface treatment: A metal coating is applied to the upper and lower surfaces of the surface-activated diamond sheet using magnetron sputtering; a copper-containing active brazing layer is then applied to the metal coating to obtain a surface-treated diamond sheet; Preparation of copper-clad diamond copper plate: 1) punching and folding a copper foil into a hexahedral copper foil box with an upper cover and an opening, placing the box into a mold, and laying a copper mesh with a uniform grid inside the hexahedral copper foil box; 2) using an arranging machine to arrange diamond particles coated on the surface in each grid of the copper mesh; 3) placing the hexahedral copper foil box with arranged diamond particles and the mold on a vibration table, spraying copper powder onto the copper mesh under vibration mode until the copper powder fills the gaps in the copper mesh and reaches the same height as the copper mesh; 4) placing the copper mesh inside the hexahedral copper foil box, repeating 2) and 3) until the copper mesh is flush with the height of the hexahedral copper foil box; 5) closing the upper cover at the opening, combining the upper cover and the copper foil box to obtain a preform; 6) placing the preform in a vacuum sintering furnace for vacuum sintering to obtain a sintered copper-clad diamond copper plate; Brazing connection: Place the copper-clad diamond copper plate, the surface-treated diamond sheet, and the copper sheet used to form the first copper layer into the fixture in sequence and tighten them, then place them in a vacuum brazing furnace for vacuum brazing to obtain an electronic packaging heat dissipation substrate.

6. The processing technology according to claim 5, characterized in that: The surface treatment steps of diamond sheets include: Surface activation: Use 5wt% NaOH and 10wt% HCl solutions to alternately ultrasonically clean the diamond sheet for 8-12 minutes to remove surface impurities, then rinse with pure water and dry. Magnetron sputtering metal coating: Place the surface activated diamond sheet in a graphite mold and magnetron sputter to form a metal coating. Ensure that the sputtering area is flat and unobstructed. The sputtering conditions are: DC sputtering power 120-180W, sputtering time 1-3h, target-substrate distance 5-10cm, argon flow rate 15-25sccm, vacuum degree <5×10 -3 Pa; Heat treatment: After forming the metal coating, the diamond sheet is vacuum annealed at 400~600℃ for 1~2h; Acid etching: After annealing, 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.

7. The processing technology according to claim 6, characterized in that: In the step of preparing copper-clad diamond copper plate, the vacuum sintering conditions are: vacuum degree is 10 -1 ~10 -3 Pa, the heating process is from room temperature to 900~1100℃ at a rate of 5~20℃ / min, and after keeping warm for 20~120min, pressurization is started, the pressurization pressure is 20~50MPa, and the pressure is maintained and cooled to room temperature.

8. The processing technology according to claim 6, characterized in that: During the brazing process, vacuum brazing is used with a vacuum degree of 10 -1 ~10 -5 Pa, heat to 700~900℃ at 5~10℃ / min, keep warm for 30~60min, and pressurize to 0.1~10MPa at the same time.

9. Use of the electronic packaging heat dissipation substrate according to any one of claims 1 to 4 in manufacturing an electronic packaging radiator.

10. An electronic packaging radiator, characterized in that: The electronic packaging heat dissipation substrate comprises the electronic packaging heat dissipation substrate according to any one of claims 1 to 4.

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