Method and structure for ultra-tight sealing of a single crystal diamond to oxygen-free copper

Abstract

This application relates to the fields of precision packaging and vacuum welding technology, and in particular to a method and structure for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity. The method includes: cleaning and activating the surfaces of the single-crystal diamond and the oxygen-free copper framework respectively; placing Ag-Cu-Sn-Ti brazing filler metal into a parameterized stepped drill groove; placing the diamond and applying uniform pre-pressure; and obtaining the sealed component after high-vacuum segmented heating and holding and extremely slow cooling. This solves the problems of traditional sealing technology, such as the need for pre-metallization treatment of diamond, difficulty in simultaneously achieving hermeticity and thermal conductivity, large residual stress at the interface that easily leads to diamond cracking, and high-temperature brazing that easily causes diamond graphitization.

Description

Technical Field

[0001] This application relates to the fields of precision packaging and vacuum welding technology, and in particular to a method and structure for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity. Background Technology

[0002] Single-crystal diamond (SCD) is currently the solid material with the highest known thermal conductivity at room temperature, ranging from 900 to 2200 W / (m·K). It also possesses an extremely low coefficient of thermal expansion, approximately 1.0–1.5 × 10⁻⁶ W / (m·K) from room temperature to 200°C. -6 With a wide bandgap of 5.5 eV, ultra-high hardness (Vickers hardness not less than 70 GPa), and full-spectrum optical transmittance from ultraviolet to far-infrared, it is an ideal material for heat dissipation in high-power electronic devices and vacuum optical windows. Oxygen-free copper TU1 has an oxygen content of no more than 0.001 wt% and a thermal conductivity of approximately 394 W / (m·K). Due to its excellent machinability and brazing adaptability, it is widely used in core components such as high-power heat dissipation module housings, vacuum-sealed packaging frames, and X-ray device housings. With the continuous increase in the power density of electronic devices, achieving a reliable seal with extremely high hermeticity and high thermal conductivity between single-crystal diamond and oxygen-free copper TU1 has become a key technological bottleneck restricting the performance breakthrough of related high-end equipment.

[0003] However, the heterogeneous sealing of single-crystal diamond and oxygen-free copper faces four fundamental technical challenges: First, the diamond surface is composed of sp... 3 Composed of hybrid carbon atoms, with a surface energy of only 30-50 mJ / m 2 First, it is chemically inert; conventional silver-based brazing filler metals have a contact angle exceeding 120° on its surface, making effective wetting impossible and direct brazing difficult to achieve metallurgical bonding. Second, the thermal expansion coefficients of the two are severely mismatched; the thermal expansion coefficient of single-crystal diamond is approximately 1.0 × 10⁻⁶. -6 / K, oxygen-free copper TU1 approximately 16.5 × 10 -6 / K, mismatch as high as 15.5×10 -6 / K, during the brazing cooling process, significant residual thermal stress is generated at the interface, which can easily lead to diamond cracking or brazing seam detachment; third, in a vacuum high-temperature environment, single-crystal diamond is prone to graphitization transformation on the surface when the temperature exceeds 700℃. The thermal conductivity of the graphitized layer is only 1-5 W / (m·K), which will seriously damage the core thermal conductivity of diamond; fourth, most existing diamond-to-metal brazing technologies are developed for polycrystalline diamond or diamond films, and generally lack a complete sealing solution for specific crystal orientations of single-crystal diamond, including {100} or {111} crystal planes, integrated transition structures, and precise step drill-holding geometry. Moreover, there is no publicly available systematic process that can simultaneously meet the requirement that the airtight leakage rate does not exceed 1×10 -10 Pa·m3 / s The thermal resistance of the contact joint does not exceed 3×10 -6 m 2 · Stringent K / W requirements.

[0004] In summary, developing a single-crystal diamond-oxygen-free copper sealing technology that requires no pre-metallization treatment and possesses extremely high hermeticity, high thermal conductivity, and excellent mechanical reliability is of great engineering significance for promoting technological development in fields such as high-power semiconductors, laser optics, and X-ray detection. Summary of the Invention

[0005] This application provides a method and structure for sealing single-crystal diamond and oxygen-free copper with extremely high airtightness, in order to solve the problems of traditional sealing technology, such as the need for pre-metallization treatment of diamond, difficulty in achieving airtightness and thermal conductivity at the same time, large residual stress at the interface that easily leads to diamond cracking, and high-temperature brazing that easily causes diamond graphitization.

[0006] This application provides a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into the oxygen-free copper TU1 packaging frame. The preformed foil has a depth h of 0.10-0.25mm, a width w that overlaps with the diamond L to satisfy L / w=0.6-0.8, and rounded corners with a radius r=0.05-0.10mm. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.6-0.85 and apply a uniform pre-pressure of 0.02-0.05MPa to obtain the component to be brazed. Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10⁻⁶ throughout the process. -3 Pa is heated to the brazing peak temperature of 790-815℃ using a segmented heating program and held for 4-7 minutes. Then, it is slowly cooled from the peak temperature to 500℃ at a cooling rate of ≤1.0℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a gas-sealed joint between single crystal diamond and oxygen-free copper.

[0007] Optionally, in step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and flatness≤1μm, and in step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil side.

[0008] Optionally, in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 65-75℃ for 8-12 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 4-6 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0009] Optionally, in step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0010] Optionally, in step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0011] Optionally, in step two, a uniform pre-pressure is applied by an alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single-crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0012] Optionally, in step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0013] Optionally, the segmented heating procedure in step three is as follows: heating from room temperature to 300℃ at a heating rate of 5℃ / min, and holding at 300℃ for 10min; then heating from 300℃ to 500℃ at a heating rate of 5℃ / min, and holding at 500℃ for 5min; subsequently heating from 500℃ to the brazing peak temperature at a heating rate of 2-3℃ / min.

[0014] Optionally, after step three, a welding quality inspection step is also included, specifically: visual inspection is performed using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; laser Raman spectroscopy is used to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0015] This application also proposes a highly hermetic sealing structure for single-crystal diamond and oxygen-free copper, comprising: The system comprises a single-crystal diamond substrate, an active solder layer, and an oxygen-free copper TU1 encapsulation frame. The oxygen-free copper TU1 encapsulation frame features a stepped drill-bearing structure with a step depth of 0.10-0.25 mm. The ratio of the step width to the overlap around the single-crystal diamond substrate is 0.6-0.8, and the inner corners of the steps have rounded corners with a radius of 0.05-0.10 mm. The active solder layer is formed by brazing Ag-Cu-Sn-Ti preformed foil, and its thickness is less than the step depth. The airtightness of the ultra-high hermeticity sealing structure is ≤1×10⁻⁶. -10 Pa·m 3 / s, thermal resistance at the diamond-copper interface ≤3×10 -6 m 2 ·K / W.

[0016] Therefore, this application has at least the following beneficial effects: (1) The method for sealing single crystal diamond and oxygen-free copper provided in this application adopts a parametrically designed stepped drill bearing structure, which clearly defines the quantitative relationship between the step depth and step width of the oxygen-free copper frame and the overlap amount around the diamond, as well as the size range of the inner rounded corner of the step. This structural design eliminates the dead corner of the brazing filler from a geometric perspective, avoids microcracks caused by the solidification and shrinkage of the brazing filler at right angles, and ensures the continuity and uniformity of the brazing seam. The reasonable overlap amount and step width ratio balance the effective sealing area of ​​the brazing seam and the capillary filling effect, providing a core guarantee for achieving extremely high air tightness from a structural perspective, and solving the problem of poor air tightness and easy generation of pores in traditional planar overlap structures. (2) In this embodiment, by optimizing the active solder composition and establishing a quantitative matching relationship between the thickness t of the active solder preformed foil and the step depth h during assembly, t / h is kept between 0.6 and 0.85, achieving precise control of the solder filling amount. The Ag-Cu-Sn-Ti solder used has a suitable liquidus temperature of 775 to 790 degrees Celsius and good fluidity. The active titanium element provides a chemical basis for the wetting of the diamond surface. The core design intention of this ratio is to ensure that the amount of solid solder is "intentionally underfilled", so that the molten solder can completely fill the gap between the solder joints to avoid underfilling, and will not overflow and contaminate the diamond optical surface due to excessive overflow. At the same time, it ensures that the thickness of the solder joint is uniform, laying the foundation for reducing the interface contact thermal resistance. (3) The embodiments of this application achieve direct gas-tight bonding without pre-metallization, eliminating the need for complex pre-metallization treatments such as magnetron sputtering and electroplating on the diamond surface. Under high vacuum and temperature conditions of 790 to 815 degrees Celsius, active titanium atoms existing in solid solution form in the liquid solder diffuse from the liquid phase to the surface of the single-crystal diamond {100}, and react with the sp atoms on the diamond surface. 3 Hybrid carbon atoms undergo in-situ chemical reactions to generate a TiC interface reaction layer with a NaCl-type crystal structure. The formation of the TiC interface reaction layer changes the diamond surface from a hydrophobic state to a wettable state, reducing the contact angle from greater than 120 degrees to less than 30 degrees. Liquid solder can fully spread on the composite surface of TiC and diamond and fill the gap between the brazing seams, establishing a strong metallurgical bond. After cooling and solidification, the brazing seam forms a gradient microstructure from the diamond side to the oxygen-free copper side, consisting of a TiC reaction layer, an AgCuSn eutectic layer, and a Cu(Ag,Sn) diffusion layer. This significantly simplifies the process, reduces production costs, and avoids impurities and additional interfacial thermal resistance introduced by the pre-metallization layer, further improving the thermal conductivity of the joint. (4) The embodiments of this application establish a collaborative control system and quantitative quality criteria for diamond graphitization. By strictly limiting the upper limit of the brazing peak temperature to 815 degrees Celsius and controlling the holding time to 4 to 7 minutes, the energy input of the brazing process is insufficient to destroy the sp of diamond. 3 The hybrid covalent bond structure effectively suppresses the graphitization transformation on the diamond surface from the source. For the first time, the intensity ratio of the D peak to the G peak in the Raman spectrum is used as a quantitative criterion for the degree of graphitization and incorporated into the process quality control system to achieve accurate and repeatable detection of the degree of damage to diamond performance. This system ensures that the thermal conductivity and optical properties of diamond are basically unaffected after brazing, meeting the requirements of high-end devices. (5) The embodiments of this application alleviate the residual thermal stress at the interface through multi-dimensional means, which significantly improves the mechanical reliability of the sealing joint. The AgCuSn eutectic layer formed in the brazing seam has a high elongation of 15% to 25%, which can absorb the huge residual thermal stress caused by the severe mismatch of thermal expansion coefficients between diamond and oxygen-free copper through its own elastic-plastic deformation. Combined with the extremely slow cooling process with a peak temperature of no more than 1.0 degree Celsius per minute up to 500 degrees Celsius, the temperature gradient and stress concentration during the cooling process are further reduced. After 50 cycles of high and low temperature from -55 degrees Celsius to +150 degrees Celsius, the airtightness and thermal conductivity of the joint do not deteriorate significantly, and the diamond has no cracks or chipping, exhibiting excellent long-term service stability. (6) The embodiments of this application achieve synergistic optimization of airtightness and thermal conductivity, establish a standardized comprehensive quality inspection process, and ensure extremely high airtightness through a continuous, dense, and defect-free brazing seam structure. The thin and uniform TiC interface reaction layer and the highly thermally conductive AgCuSn eutectic layer together ensure low interfacial contact thermal resistance. The prepared sealing joint simultaneously meets the requirement that the airtight leakage rate does not exceed 1×10 -10 Pa·m 3 / s and interfacial contact thermal resistance not exceeding 3×10 -6 m 2 The product meets stringent K / W requirements. A combined inspection method, employing visual inspection, Raman spectroscopy, helium mass spectrometry leak detection, and steady-state heat flow testing, allows for a comprehensive and accurate assessment of product quality. This technology can be widely applied in fields with extremely high requirements for airtightness and thermal conductivity, such as high-power semiconductor heat dissipation modules, high-power laser optical windows, and X-ray device windows, and has significant engineering application value.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart illustrating a method for sealing single-crystal diamond with oxygen-free copper with extremely high hermeticity according to an embodiment of this application. Figure 2 The flowcharts for quality inspection of diamond sealing process provided in Examples 1-5 and Comparative Examples 1-3 of this application are as follows; Figure 3 This is a schematic diagram of the hermetic sealing of single-crystal diamond and oxygen-free copper according to Embodiments 1-5 of this application; Figure 4 This is a temperature-time program curve of a diamond high-vacuum active brazing furnace according to Embodiment 3 of this application; Figure 5 This is an enlarged cross-sectional view of the stepped area of ​​the diamond sealing structure provided in Embodiment 3 of this application.

[0019] Figure reference numerals: 1. 0.3mm single-crystal diamond substrate; 2. Single-crystal diamond {100} crystal plane; 3. Ceramic block; 4. Active solder sheet; 5. Oxygen-free copper frame; 6. TiC reaction layer; 7. AgCuSn eutectic layer; 8. Cu(Ag,Sn) diffusion layer. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] In the embodiments of this application, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0022] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0023] Example 1 This application provides a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Understandably, the multi-step, graded surface cleaning and activation treatment of single-crystal diamond and oxygen-free copper framework in this embodiment aims to thoroughly remove surface organic contaminants, oxide films, and metal ion impurities, exposing an atomically clean, fresh surface. Strict control of temperature and time in each cleaning step ensures complete decomposition of contaminants without damaging the substrate surface morphology; ultimately reducing the water contact angle on the diamond surface to below 10°, creating the necessary conditions for subsequent wetting and interfacial reaction of the active solder. This is a prerequisite for obtaining a defect-free, high-strength metallurgical bond, directly determining the airtightness and long-term reliability of the sealing joint.

[0024] Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into a stepped drill groove in the oxygen-free copper TU1 packaging frame. The groove has a depth h of 0.10 mm, a width w and a diamond overlap L satisfying L / w=0.6, and an inner corner with a radius r=0.05 mm rounded transition. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.6, and apply a uniform pre-pressure of 0.02 MPa to obtain the component to be brazed. It is understood that the parametrically designed stepped drill-bearing structure and quantitative pre-pressure assembly process employed in this application embodiment aim to ensure accurate positioning and uniform filling of the brazing filler metal. Precise control of the brazing filler metal thickness to the step depth ensures that the molten brazing filler metal completely fills the gap between the drill joints using capillary force without overflowing and contaminating the diamond surface. Uniform pre-pressure is applied using an alumina ceramic pressure block with excellent flatness, ensuring tight contact between the diamond and the brazing filler metal, and between the brazing filler metal and the copper frame. Strictly limiting the time interval between assembly and furnace entry prevents the clean surface from re-adsorbing impurities. This assembly-level approach ensures the continuity and uniformity of the drill joints, laying the foundation for achieving extremely high airtightness.

[0025] Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10 throughout the process. -3 Pa was heated to the brazing peak temperature of 790℃ using a segmented heating program and held for 4 minutes. Then, it was slowly cooled from the peak temperature to 500℃ at a cooling rate of 1.0℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a single crystal diamond and oxygen-free copper gas-sealed joint.

[0026] Understandably, the embodiments of this application employ a brazing process with coordinated high-vacuum segmented heating, holding, and extremely slow cooling to simultaneously optimize the interface reaction effect and the level of residual interface stress. The high-vacuum environment avoids the oxidation problem of metal and diamond under high-temperature conditions, while the segmented heating program ensures uniform temperature distribution within the furnace and fully removes gases adsorbed by the workpiece and furnace body. Precise control of the brazing peak temperature and holding time promotes the full reaction between active titanium atoms and carbon atoms on the diamond surface, generating a dense TiC interface layer, while strictly inhibiting the graphitization transformation of diamond. The extremely slow cooling process, with a peak temperature of 500°C, significantly reduces the temperature gradient and interface stress concentration during the cooling process. This is a core step in obtaining a direct metallurgical bonding interface without pre-metallization and improving the mechanical reliability of the sealing joint.

[0027] In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and the flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil.

[0028] It should be noted that in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 65℃ for 8 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 4 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0029] In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0030] In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0031] In step two, uniform pre-pressure is applied by the alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0032] In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0033] The segmented heating procedure in step three is as follows: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and hold at 300℃ for 10 minutes; then heat from 300℃ to 500℃ at a heating rate of 5℃ / min, and hold at 500℃ for 5 minutes; subsequently heat from 500℃ to the brazing peak temperature at a heating rate of 2℃ / min.

[0034] Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0035] This application also proposes an ultra-high hermeticity sealing structure for single-crystal diamond and oxygen-free copper, comprising: a single-crystal diamond substrate, an active solder layer, and an oxygen-free copper TU1 packaging frame; the oxygen-free copper TU1 packaging frame has a stepped drill-bearing structure with a step depth of 0.10 mm, a step width to the overlap of the single-crystal diamond substrate being 0.6, and a 0.05 mm radius rounded corner transition at the inner corner of the step; the active solder layer is formed by brazing Ag-Cu-Sn-Ti preformed foil, and its thickness is less than the step depth; the ultra-high hermeticity sealing structure has a hermeticity leakage rate ≤1×10⁻⁶. -10 Pa·m 3 / s, thermal resistance at the diamond-copper interface ≤3×10 -6 m 2 ·K / W.

[0036] Example 2 This application provides a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Understandably, the multi-step, graded surface cleaning and activation treatment of single-crystal diamond and oxygen-free copper framework in this embodiment aims to thoroughly remove surface organic contaminants, oxide films, and metal ion impurities, exposing an atomically clean, fresh surface. Strict control of temperature and time in each cleaning step ensures complete decomposition of contaminants without damaging the substrate surface morphology; ultimately reducing the water contact angle on the diamond surface to below 10°, creating the necessary conditions for subsequent wetting and interfacial reaction of the active solder. This is a prerequisite for obtaining a defect-free, high-strength metallurgical bond, directly determining the airtightness and long-term reliability of the sealing joint.

[0037] Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into a stepped drill groove in the oxygen-free copper TU1 packaging frame. The groove has a depth h of 0.13mm, a width w and a diamond overlap L satisfying L / w=0.65, and an inner corner with a radius r=0.08mm rounded transition. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.63, and apply a uniform pre-pressure of 0.03MPa to obtain the component to be brazed. It is understood that the parametrically designed stepped drill-bearing structure and quantitative pre-pressure assembly process employed in this application embodiment aim to ensure accurate positioning and uniform filling of the brazing filler metal. Precise control of the brazing filler metal thickness to the step depth ensures that the molten brazing filler metal completely fills the gap between the drill joints using capillary force without overflowing and contaminating the diamond surface. Uniform pre-pressure is applied using an alumina ceramic pressure block with excellent flatness, ensuring tight contact between the diamond and the brazing filler metal, and between the brazing filler metal and the copper frame. Strictly limiting the time interval between assembly and furnace entry prevents the clean surface from re-adsorbing impurities. This assembly-level approach ensures the continuity and uniformity of the drill joints, laying the foundation for achieving extremely high airtightness.

[0038] Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10 throughout the process. -3 Pa was heated to the brazing peak temperature of 800℃ using a segmented heating program and held for 5 minutes. Then, it was slowly cooled from the peak temperature to 500℃ at a cooling rate of 0.95℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a single crystal diamond and oxygen-free copper gas-sealed joint.

[0039] Understandably, the embodiments of this application employ a brazing process with coordinated high-vacuum segmented heating, holding, and extremely slow cooling to simultaneously optimize the interface reaction effect and the level of residual interface stress. The high-vacuum environment avoids the oxidation problem of metal and diamond under high-temperature conditions, while the segmented heating program ensures uniform temperature distribution within the furnace and fully removes gases adsorbed by the workpiece and furnace body. Precise control of the brazing peak temperature and holding time promotes the full reaction between active titanium atoms and carbon atoms on the diamond surface, generating a dense TiC interface layer, while strictly inhibiting the graphitization transformation of diamond. The extremely slow cooling process, with a peak temperature of 500°C, significantly reduces the temperature gradient and interface stress concentration during the cooling process. This is a core step in obtaining a direct metallurgical bonding interface without pre-metallization and improving the mechanical reliability of the sealing joint.

[0040] In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and the flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil.

[0041] It should be noted that in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 68℃ for 9 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 5 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0042] In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0043] In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0044] In step two, uniform pre-pressure is applied by the alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0045] In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0046] The segmented heating procedure in step three is as follows: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and hold at 300℃ for 10min; then heat from 300℃ to 500℃ at a heating rate of 5℃ / min, and hold at 500℃ for 5min; then heat from 500℃ to the peak brazing temperature at a heating rate of 2.2℃ / min.

[0047] Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0048] This application also proposes an ultra-high hermeticity sealing structure for single-crystal diamond and oxygen-free copper, comprising: a single-crystal diamond substrate, an active solder layer, and an oxygen-free copper TU1 packaging frame; the oxygen-free copper TU1 packaging frame has a stepped drill-bearing structure with a step depth of 0.13 mm, a step width to the overlap of the single-crystal diamond substrate being 0.65, and a rounded corner with a radius of 0.08 mm at the inner corner of the step; the active solder layer is formed by brazing Ag-Cu-Sn-Ti preformed foil, and its thickness is less than the step depth; the ultra-high hermeticity sealing structure has a hermeticity leakage rate ≤1×10⁻⁶. -10 Pa·m 3 / s, thermal resistance at the diamond-copper interface ≤3×10 -6 m 2 ·K / W.

[0049] Example 3 This application provides a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Understandably, the multi-step, graded surface cleaning and activation treatment of single-crystal diamond and oxygen-free copper framework in this embodiment aims to thoroughly remove surface organic contaminants, oxide films, and metal ion impurities, exposing an atomically clean, fresh surface. Strict control of temperature and time in each cleaning step ensures complete decomposition of contaminants without damaging the substrate surface morphology; ultimately reducing the water contact angle on the diamond surface to below 10°, creating the necessary conditions for subsequent wetting and interfacial reaction of the active solder. This is a prerequisite for obtaining a defect-free, high-strength metallurgical bond, directly determining the airtightness and long-term reliability of the sealing joint.

[0050] Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into a stepped drill groove in the oxygen-free copper TU1 packaging frame. The groove has a depth h of 0.16 mm, a width w and a diamond overlap L satisfying L / w=0.70, and an inner corner with a radius r=0.10 mm rounded transition. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.67, and apply a uniform pre-pressure of 0.03 MPa to obtain the component to be brazed. It is understood that the parametrically designed stepped drill-bearing structure and quantitative pre-pressure assembly process employed in this application embodiment aim to ensure accurate positioning and uniform filling of the brazing filler metal. Precise control of the brazing filler metal thickness to the step depth ensures that the molten brazing filler metal completely fills the gap between the drill joints using capillary force without overflowing and contaminating the diamond surface. Uniform pre-pressure is applied using an alumina ceramic pressure block with excellent flatness, ensuring tight contact between the diamond and the brazing filler metal, and between the brazing filler metal and the copper frame. Strictly limiting the time interval between assembly and furnace entry prevents the clean surface from re-adsorbing impurities. This assembly-level approach ensures the continuity and uniformity of the drill joints, laying the foundation for achieving extremely high airtightness.

[0051] Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10 throughout the process. -3 Pa was heated to the brazing peak temperature of 815℃ using a segmented heating program and held for 5 minutes. Then, it was slowly cooled from the peak temperature to 500℃ at a cooling rate of 0.9℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a single crystal diamond and oxygen-free copper gas-sealed joint.

[0052] Understandably, the embodiments of this application employ a brazing process with coordinated high-vacuum segmented heating, holding, and extremely slow cooling to simultaneously optimize the interface reaction effect and the level of residual interface stress. The high-vacuum environment avoids the oxidation problem of metal and diamond under high-temperature conditions, while the segmented heating program ensures uniform temperature distribution within the furnace and fully removes gases adsorbed by the workpiece and furnace body. Precise control of the brazing peak temperature and holding time promotes the full reaction between active titanium atoms and carbon atoms on the diamond surface, generating a dense TiC interface layer, while strictly inhibiting the graphitization transformation of diamond. The extremely slow cooling process, with a peak temperature of 500°C, significantly reduces the temperature gradient and interface stress concentration during the cooling process. This is a core step in obtaining a direct metallurgical bonding interface without pre-metallization and improving the mechanical reliability of the sealing joint.

[0053] In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and the flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil.

[0054] It should be noted that in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 70℃ for 10 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 5 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0055] In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0056] In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0057] In step two, uniform pre-pressure is applied by the alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0058] In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0059] The segmented heating procedure in step three is as follows: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and hold at 300℃ for 10min; then heat from 300℃ to 500℃ at a heating rate of 5℃ / min, and hold at 500℃ for 5min; then heat from 500℃ to the brazing peak temperature at a heating rate of 2.5℃ / min.

[0060] Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0061] This application also proposes an ultra-high hermeticity sealing structure for single-crystal diamond and oxygen-free copper, comprising: a single-crystal diamond substrate, an active solder layer, and an oxygen-free copper TU1 packaging frame; the oxygen-free copper TU1 packaging frame has a stepped drill-bearing structure with a step depth of 0.16 mm, a step width to the overlap of the single-crystal diamond substrate being 0.7, and a rounded corner with a radius of 0.10 mm at the inner corner of the step; the active solder layer is formed by brazing Ag-Cu-Sn-Ti preformed foil, and its thickness is less than the step depth; the ultra-high hermeticity sealing structure has a hermeticity leakage rate ≤1×10⁻⁶. -10 Pa·m 3 / s, thermal resistance at the diamond-copper interface ≤3×10 -6 m 2 ·K / W.

[0062] Example 4 This application provides a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Understandably, the multi-step, graded surface cleaning and activation treatment of single-crystal diamond and oxygen-free copper framework in this embodiment aims to thoroughly remove surface organic contaminants, oxide films, and metal ion impurities, exposing an atomically clean, fresh surface. Strict control of temperature and time in each cleaning step ensures complete decomposition of contaminants without damaging the substrate surface morphology; ultimately reducing the water contact angle on the diamond surface to below 10°, creating the necessary conditions for subsequent wetting and interfacial reaction of the active solder. This is a prerequisite for obtaining a defect-free, high-strength metallurgical bond, directly determining the airtightness and long-term reliability of the sealing joint.

[0063] Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into a stepped drill groove in the oxygen-free copper TU1 packaging frame. The groove has a depth h of 0.20 mm, a width w and a diamond overlap L satisfying L / w=0.75, and an inner corner with a radius r=0.10 mm rounded transition. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.75, and apply a uniform pre-pressure of 0.04 MPa to obtain the component to be brazed. It is understood that the parametrically designed stepped drill-bearing structure and quantitative pre-pressure assembly process employed in this application embodiment aim to ensure accurate positioning and uniform filling of the brazing filler metal. Precise control of the brazing filler metal thickness to the step depth ensures that the molten brazing filler metal completely fills the gap between the drill joints using capillary force without overflowing and contaminating the diamond surface. Uniform pre-pressure is applied using an alumina ceramic pressure block with excellent flatness, ensuring tight contact between the diamond and the brazing filler metal, and between the brazing filler metal and the copper frame. Strictly limiting the time interval between assembly and furnace entry prevents the clean surface from re-adsorbing impurities. This assembly-level approach ensures the continuity and uniformity of the drill joints, laying the foundation for achieving extremely high airtightness.

[0064] Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10 throughout the process. -3 Pa was heated to the brazing peak temperature of 810℃ using a segmented heating program and held for 6 minutes. Then, it was slowly cooled from the peak temperature to 500℃ at a cooling rate of 0.85℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a gas-sealed joint between single crystal diamond and oxygen-free copper.

[0065] Understandably, the embodiments of this application employ a brazing process with coordinated high-vacuum segmented heating, holding, and extremely slow cooling to simultaneously optimize the interface reaction effect and the level of residual interface stress. The high-vacuum environment avoids the oxidation problem of metal and diamond under high-temperature conditions, while the segmented heating program ensures uniform temperature distribution within the furnace and fully removes gases adsorbed by the workpiece and furnace body. Precise control of the brazing peak temperature and holding time promotes the full reaction between active titanium atoms and carbon atoms on the diamond surface, generating a dense TiC interface layer, while strictly inhibiting the graphitization transformation of diamond. The extremely slow cooling process, with a peak temperature of 500°C, significantly reduces the temperature gradient and interface stress concentration during the cooling process. This is a core step in obtaining a direct metallurgical bonding interface without pre-metallization and improving the mechanical reliability of the sealing joint.

[0066] In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and the flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil.

[0067] It should be noted that in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 72℃ for 11 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 5 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0068] In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0069] In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0070] In step two, uniform pre-pressure is applied by the alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0071] In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0072] The segmented heating procedure in step three is as follows: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and hold at 300℃ for 10min; then heat from 300℃ to 500℃ at a heating rate of 5℃ / min, and hold at 500℃ for 5min; subsequently heat from 500℃ to the brazing peak temperature at a heating rate of 2.7℃ / min.

[0073] Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0074] This application also proposes an ultra-high hermeticity sealing structure for single-crystal diamond and oxygen-free copper, comprising: a single-crystal diamond substrate, an active solder layer, and an oxygen-free copper TU1 packaging frame; the oxygen-free copper TU1 packaging frame has a stepped drill-bearing structure with a step depth of 0.20 mm, a step width to the overlap of the single-crystal diamond substrate being 0.75, and a rounded corner with a radius of 0.10 mm at the inner corner of the step; the active solder layer is formed by brazing Ag-Cu-Sn-Ti preformed foil, and its thickness is less than the step depth; the ultra-high hermeticity sealing structure has a hermeticity leakage rate ≤1×10⁻⁶. -10 Pa·m 3 / s, thermal resistance at the diamond-copper interface ≤3×10 -6 m 2 ·K / W.

[0075] Example 5 This application provides a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Understandably, the multi-step, graded surface cleaning and activation treatment of single-crystal diamond and oxygen-free copper framework in this embodiment aims to thoroughly remove surface organic contaminants, oxide films, and metal ion impurities, exposing an atomically clean, fresh surface. Strict control of temperature and time in each cleaning step ensures complete decomposition of contaminants without damaging the substrate surface morphology; ultimately reducing the water contact angle on the diamond surface to below 10°, creating the necessary conditions for subsequent wetting and interfacial reaction of the active solder. This is a prerequisite for obtaining a defect-free, high-strength metallurgical bond, directly determining the airtightness and long-term reliability of the sealing joint.

[0076] Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into a stepped drill groove in the oxygen-free copper TU1 packaging frame. The groove has a depth h of 0.25mm, a width w and a diamond overlap L satisfying L / w=0.80, and an inner corner with a radius r=0.10mm rounded transition. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.85, and apply a uniform pre-pressure of 0.05MPa to obtain the component to be brazed. It is understood that the parametrically designed stepped drill-bearing structure and quantitative pre-pressure assembly process employed in this application embodiment aim to ensure accurate positioning and uniform filling of the brazing filler metal. Precise control of the brazing filler metal thickness to the step depth ensures that the molten brazing filler metal completely fills the gap between the drill joints using capillary force without overflowing and contaminating the diamond surface. Uniform pre-pressure is applied using an alumina ceramic pressure block with excellent flatness, ensuring tight contact between the diamond and the brazing filler metal, and between the brazing filler metal and the copper frame. Strictly limiting the time interval between assembly and furnace entry prevents the clean surface from re-adsorbing impurities. This assembly-level approach ensures the continuity and uniformity of the drill joints, laying the foundation for achieving extremely high airtightness.

[0077] Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10 throughout the process. -3 Pa was heated to the brazing peak temperature of 815℃ using a segmented heating program and held for 7 minutes. Then, it was slowly cooled from the peak temperature to 500℃ at a cooling rate of 0.8℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a single crystal diamond and oxygen-free copper gas-sealed joint.

[0078] Understandably, the embodiments of this application employ a brazing process with coordinated high-vacuum segmented heating, holding, and extremely slow cooling to simultaneously optimize the interface reaction effect and the level of residual interface stress. The high-vacuum environment avoids the oxidation problem of metal and diamond under high-temperature conditions, while the segmented heating program ensures uniform temperature distribution within the furnace and fully removes gases adsorbed by the workpiece and furnace body. Precise control of the brazing peak temperature and holding time promotes the full reaction between active titanium atoms and carbon atoms on the diamond surface, generating a dense TiC interface layer, while strictly inhibiting the graphitization transformation of diamond. The extremely slow cooling process, with a peak temperature of 500°C, significantly reduces the temperature gradient and interface stress concentration during the cooling process. This is a core step in obtaining a direct metallurgical bonding interface without pre-metallization and improving the mechanical reliability of the sealing joint.

[0079] In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and the flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil.

[0080] It should be noted that in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 75°C for 12 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 6 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0081] In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0082] In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0083] In step two, uniform pre-pressure is applied by the alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0084] In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0085] The segmented heating procedure in step three is as follows: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and hold at 300℃ for 10 minutes; then heat from 300℃ to 500℃ at a heating rate of 5℃ / min, and hold at 500℃ for 5 minutes; subsequently heat from 500℃ to the peak brazing temperature at a heating rate of 3℃ / min.

[0086] Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0087] This application also proposes an ultra-high hermeticity sealing structure for single-crystal diamond and oxygen-free copper, comprising: a single-crystal diamond substrate, an active solder layer, and an oxygen-free copper TU1 packaging frame; the oxygen-free copper TU1 packaging frame has a stepped drill-bearing structure with a step depth of 0.25 mm, a step width to the overlap of the single-crystal diamond substrate being 0.8, and a rounded corner with a radius of 0.10 mm at the inner corner of the step; the active solder layer is formed by brazing Ag-Cu-Sn-Ti preformed foil, and its thickness is less than the step depth; the ultra-high hermeticity sealing structure has a hermeticity leakage rate ≤1×10⁻⁶. -10 Pa·m 3 / s, thermal resistance at the diamond-copper interface ≤3×10 -6 m 2 ·K / W.

[0088] Comparative Example 1 This application provides a comparative example of a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into the oxygen-free copper TU1 packaging frame. The preformed foil has a depth h of 0.16 mm, a width w that overlaps with the diamond L to satisfy L / w=0.70, and a right-angle transition at the inner corner. Then, place the single-crystal diamond substrate flat on the solder foil with a thickness t that satisfies t / h=0.67, and apply a uniform pre-pressure of 0.03 MPa to obtain the component to be brazed. Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10 throughout the process. -3 Pa was heated to the brazing peak temperature of 815℃ using a segmented heating program and held for 5 minutes. Then, it was slowly cooled from the peak temperature to 500℃ at a cooling rate of 0.9℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a single crystal diamond and oxygen-free copper gas-sealed joint.

[0089] In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and the flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil.

[0090] It should be noted that in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 70℃ for 10 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 5 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0091] In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0092] In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0093] In step two, uniform pre-pressure is applied by the alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0094] In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0095] The segmented heating procedure in step three is as follows: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and hold at 300℃ for 10min; then heat from 300℃ to 500℃ at a heating rate of 5℃ / min, and hold at 500℃ for 5min; then heat from 500℃ to the brazing peak temperature at a heating rate of 2.5℃ / min.

[0096] Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶.-10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0097] Comparative Example 2 This application provides a comparative example of a method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, including: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into a stepped drill groove in the oxygen-free copper TU1 packaging frame. The groove has a depth h of 0.16 mm, a width w and a diamond overlap L satisfying L / w=0.70, and an inner corner with a radius r=0.10 mm rounded transition. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.67, and apply a uniform pre-pressure of 0.03 MPa to obtain the component to be brazed. Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10 throughout the process. -3 Pa was heated to the brazing peak temperature of 815℃ using a segmented heating program and held for 5 minutes. After that, it was naturally cooled in the furnace to a temperature of <55℃ before being taken out of the furnace, thus producing a gas-sealed joint between single crystal diamond and oxygen-free copper.

[0098] In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and the flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil.

[0099] It should be noted that in step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 70℃ for 10 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 5 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

[0100] In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

[0101] In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

[0102] In step two, uniform pre-pressure is applied by the alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

[0103] In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

[0104] The segmented heating procedure in step three is as follows: heat from room temperature to 300℃ at a heating rate of 5℃ / min, and hold at 300℃ for 10min; then heat from 300℃ to 500℃ at a heating rate of 5℃ / min, and hold at 500℃ for 5min; then heat from 500℃ to the brazing peak temperature at a heating rate of 2.5℃ / min.

[0105] Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

[0106] Comparative Example 3 This application provides a comparative example of a method for achieving extremely high hermeticity sealing between single-crystal diamond and oxygen-free copper. First, the diamond surface undergoes pre-metallization treatment via titanium film sputtering. Then, ordinary silver-copper eutectic solder is used, and the bonding is achieved under a vacuum degree ≤ 5 × 10⁻⁶. -3 Vacuum brazing was performed under high temperature conditions above 830℃, and the brazing was then rapidly cooled to room temperature to obtain a single crystal diamond and oxygen-free copper sealing component.

[0107] Performance testing To verify the structure, performance, and technical effectiveness of the high hermeticity sealing method between single-crystal diamond and oxygen-free copper proposed in this application, Examples 1-5 were strictly conducted in accordance with... Figure 1 The samples were prepared using the method shown. For comparison, comparative examples 1-3 were prepared by adjusting specific steps in the process. All samples were systematically tested and characterized, and the results are as follows.

[0108] like Figure 2 As shown, this application establishes a standardized diamond sealing process quality inspection procedure applicable to Examples 1-5 and Comparative Examples 1-3. After completing surface treatment, solder assembly, and vacuum brazing in sequence, the core sealing performance, long-term service reliability, and micro-interface structure of the sealing component are comprehensively verified through four core steps: visual inspection, Raman spectroscopy graphitization detection, helium mass spectrometry gas tightness leak detection, and steady-state heat flow method contact thermal resistance test.

[0109] Core sealing performance test The weld appearance integrity was inspected using a 20x stereomicroscope, and the degree of graphitization in the diamond non-sealing area was detected using laser Raman spectroscopy with a sensitivity ≤1×10⁻⁶. -12 Pa·m 3 The air tightness was tested using a helium mass spectrometer with a speed of / s, and the contact thermal resistance at the diamond-copper interface was tested using the steady-state heat flow method. The core sealing performance test data of each embodiment and comparative example are shown in Table 1.

[0110] Table 1. Core Sealing Performance Test Results

[0111] As shown in Table 1, all the sealing components prepared in Examples 1-5 of this application simultaneously meet all four core technical indicators, achieving a synergistic breakthrough in extremely high airtightness and high thermal conductivity. Regarding airtightness, the leakage rate of all examples is more than one order of magnitude lower than the acceptable standard, with Examples 1-3 reaching as low as 3 × 10⁻⁶. -11 Pa·m 3 / s, which is due to the parameterized stepped sealing structure applicable to Examples 1-5, such as Figure 3As shown, 1 is a 0.3mm single-crystal diamond substrate, 2 is a single-crystal diamond {100} crystal facet, 3 is a ceramic block, 4 is an active solder sheet, and 5 is an oxygen-free copper frame. Specifically, the overlap ratio of L / w = 0.6-0.8 and the step width balance the effective sealing area of ​​the brazing seam and the capillary filling effect; the inner rounded corner transition of r = 0.05-0.10mm completely eliminates the dead corner of solder filling at right angles; the matching relationship between solder thickness and step depth of t / h = 0.6-0.85 precisely controls the filling amount of molten solder, avoiding airtightness defects caused by underfilling and preventing diamond surface contamination caused by overfilling. In stark contrast, in Comparative Example 1, due to the right-angle transition on the inner side of the step, the solder cannot be fully spread at the corner, forming micropores with a diameter of 5-10μm, causing the airtightness leakage rate to soar to 1.2×10 -9 The Pa·m³ / s is 40 times higher than that of the example, completely failing to meet the requirements of ultra-high vacuum sealing. Regarding thermal conductivity, the interfacial thermal resistance of the examples is far below the threshold, with an overall joint thermal conductivity of 320 W / (m·K). The thin and dense TiC layer generated by the in-situ reaction without pre-metallization avoids additional thermal resistance, while Comparative Example 3 suffers from a surge in thermal resistance due to the pre-metallization and graphitization layers. In terms of graphitization control, the ID / IG ratio of all examples remains stable at 0.01, almost identical to the original wafer, and the peak temperature below 815℃ suppresses sp from the source. 3 The hybridization transition resulted in an ID / IG ratio of 0.12 due to high-temperature brazing in Comparative Example 3. Regarding weld integrity, the weld in the embodiment was defect-free, while Comparative Example 2, lacking an extremely slow cooling process, developed microcracks, posing a potential service risk.

[0112] Reliability and optical performance testing The reliability of thermal cycling from -55℃ to 150℃ was tested using a high and low temperature cycling test chamber. The cycle was 30 min / cycle, with a holding time of 15 min / temperature zone, for a total of 50 cycles. The optical transmittance of diamond in the 10.6 μm band was tested using an infrared spectrometer. The test results are shown in Table 2.

[0113] Table 2 Reliability and Optical Performance Test Results

[0114] As shown in Table 2, the sealing components prepared in Examples 1-5 of this application exhibit excellent long-term service reliability and optical performance stability. Regarding thermal cycling reliability, after 50 cycles of high and low temperature cycling, the changes in airtightness and interfacial thermal resistance in all examples were less than 5%, and there were no visible defects. This is attributed to the multi-dimensional residual thermal stress mitigation system: the high-elongation AgCuSn eutectic layer absorbs 15.5 × 10⁻⁶ ppm through elastoplastic deformation. -6 / K thermal mismatch stress, fit as Figure 4The segmented heating, holding, and extremely slow cooling brazing process shown in the figure (this figure is based on the optimal embodiment 3, and the segmented temperature control principle it demonstrates is applicable to all embodiments) significantly reduces the temperature gradient and stress concentration during the cooling process by achieving an extremely slow cooling rate of ≤1.0℃ / min from a peak temperature of 500℃. In contrast, Comparative Example 2 did not employ the extremely slow cooling process, and the initial microcracks expanded after thermal cycling, leading to the detachment of the brazing seam. In Comparative Example 1, the initial pores continuously enlarged and connected, ultimately resulting in the complete loss of vacuum sealing function. Regarding optical performance, all embodiments maintained an infrared transmittance of 71.3%-71.8% at 10.6μm, with a loss of less than 1% compared to the original. Precise control of the brazing filler material and suppression of graphitization ensured the intrinsic optical performance of diamond. However, Comparative Example 3 experienced a sharp drop in transmittance to 62.1% due to surface graphitization, failing to meet the requirements for optical device use.

[0115] Microscopic interface structure testing The thickness of the interface reaction layer and diffusion layer was measured using a scanning electron microscope (SEM) combined with an energy dispersive spectroscopy (EDS). The wetting contact angle between the brazing filler metal and diamond was measured using a contact angle meter. The porosity of the brazing seam was determined using image analysis. The test results are shown in Table 3.

[0116] Table 3. Test results of microscopic interface structure

[0117] As shown in Table 3, Examples 1-5 of this application all formed an ideal interface microstructure with gradient distribution and uniform density, providing a solid foundation for excellent macroscopic performance. Regarding the interface reaction layer, the thickness of the TiC layer was stably controlled within the optimal range of 0.3-0.8 μm. This ensured both the full reaction of active Ti with diamond carbon atoms to form a continuous metallurgical bond and avoided an excessively thick, brittle layer that would increase thermal resistance and reduce mechanical properties. Its formation reduced the diamond surface contact angle from >120° to below 30°, achieving direct wetting brazing without pre-metallization. Figure 5As shown, 1 is a 0.3mm single-crystal diamond substrate, 5 is an oxygen-free copper framework, 6 is a TiC reaction layer, 7 is an AgCuSn eutectic layer, and 8 is a Cu(Ag,Sn) diffusion layer (this figure is drawn based on the optimal embodiment 3, and the specific parameters of its step depth h=0.16mm, overlap L=0.7mm, and inner corner radius r=0.1mm are marked. The gradient interface structure principle shown is applicable to all embodiments). This structure achieves both a strong metallurgical bond and effectively alleviates thermal mismatch stress. Regarding the diffusion layer, the 8-20μm thick Cu(Ag,Sn) solid solution layer effectively alleviates the abrupt change in interface composition and stress concentration, and its thickness increases linearly with brazing temperature and holding time, conforming to the laws of reaction and diffusion kinetics. Regarding the tightness of the brazing seam, the porosity of all embodiments was 0%. The high vacuum environment prevented oxidation and gas entrapment, and the parameterized structure ensured that the capillary force completely filled the gap. However, Comparative Example 1 had a porosity of 2.3% due to insufficient filling, and Comparative Example 3 had a porosity of 3.5% due to high-temperature oxidation and brazing filler volatilization. These microscopic defects are the root cause of the macroscopic performance degradation.

[0118] In summary, the single-crystal diamond and oxygen-free copper sealing components prepared in Examples 1-5 of this application can all simultaneously meet the requirement of a hermetically tight leakage rate ≤1×10⁻⁶. -10 Pa·m 3 / s, interfacial contact thermal resistance ≤3×10 -6 m 2 The core technical indicators, including K / W, non-graphitization of diamond, and no performance degradation after 50 thermal cycles from -55℃ to 150℃, demonstrate excellent and stable overall performance. Comparative tests with Comparative Examples 1-3 fully confirm that the parameterized stepped drill-bearing structure, precisely controlled active solder matching, pre-metallization-free in-situ reactive brazing, extremely slow cold stress relief, and quantitative control of diamond graphitization are key design features that effectively solve the critical technical bottlenecks in traditional sealing technologies, such as the difficulty in achieving simultaneous gas tightness and thermal conductivity, excessive residual stress at the interface leading to diamond cracking, and high-temperature brazing inducing diamond graphitization. The resulting sealing components possess ultra-high gas tightness, low interfacial thermal resistance, high mechanical reliability, and excellent optical stability, significantly simplifying the sealing process, reducing manufacturing costs, improving the heat dissipation efficiency and vacuum sealing reliability of high-power devices, extending the service life of high-end vacuum devices, and expanding the engineering application boundaries of single-crystal diamond materials in high-power electronics, laser optics, and X-ray detection.

[0119] The present application discloses a method and structure for achieving extremely high hermeticity sealing between single-crystal diamond and oxygen-free copper. This method eliminates the need for complex pre-metallization treatments such as magnetron sputtering and electroplating of the diamond, significantly simplifying the sealing process, shortening the production cycle, and reducing manufacturing costs. It also avoids impurities and additional interfacial thermal resistance introduced by the pre-metallization layer. The parametrically designed stepped drill-bearing structure clearly defines the quantitative matching relationship between step depth, overlap, and step width, as well as the inner rounded corner transition dimensions. This eliminates dead corners in the filler metal filling from a geometric perspective, ensuring the continuity and uniformity of the weld seam and achieving an ultra-high vacuum level hermetic seal. The optimized Ag-Cu-Sn-Ti active filler metal and in-situ reactive brazing process enable the active titanium atoms to directly react with the carbon atoms on the diamond surface to generate a dense and uniform TiC interfacial layer, achieving a strong metallurgical bond between the diamond and the metal, reducing the interfacial contact thermal resistance to 3×10⁻⁶. -6 m 2 Below K / W, the thermal conductivity of the sealing joint is significantly improved. A multi-dimensional residual thermal stress mitigation system and a diamond graphitization quantification control system effectively solve the problems of diamond cracking caused by thermal expansion coefficient mismatch and graphitization caused by high-temperature brazing. This ensures that the sealing component shows no significant performance degradation after 50 high and low temperature thermal cycles, greatly extending the service life of the device. These technologies can be widely applied in high-power semiconductor heat dissipation, high-power laser optical windows, X-ray detectors, and other high-end fields, providing reliable technical support for the engineering application of single-crystal diamond materials and promoting performance upgrades in high-power electronic and vacuum devices.

[0120] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

[0121] The present application and its embodiments have been described above. This description is not restrictive, and the actual application is not limited thereto. In conclusion, if a person skilled in the art is inspired by this description and designs a similar structure and embodiment without departing from the spirit of this application, such design should fall within the protection scope of this application.

Claims

1. A method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity, characterized in that, include: Step 1: Perform surface cleaning and activation treatments on the single crystal diamond substrate and the oxygen-free copper TU1 packaging frame respectively, without pre-metallizing the single crystal diamond. The water contact angle of the treated single crystal diamond surface is ≤10°. Step 2: Place the Ag-Cu-Sn-Ti active solder preformed foil into the oxygen-free copper TU1 packaging frame. The preformed foil has a depth h of 0.10-0.25mm, a width w that overlaps with the diamond L to satisfy L / w=0.6-0.8, and rounded corners with a radius r=0.05-0.10mm. Then, place the single crystal diamond substrate flat on the solder foil with a thickness t satisfying t / h=0.6-0.85 and apply a uniform pre-pressure of 0.02-0.05MPa to obtain the component to be brazed. Step 3: Place the components to be brazed in a vacuum brazing furnace, maintaining a vacuum level of ≤5×10⁻⁶ throughout the process. -3 Pa is heated to the brazing peak temperature of 790-815℃ using a segmented heating program and held for 4-7 minutes. Then, it is slowly cooled from the peak temperature to 500℃ at a cooling rate of ≤1.0℃ / min, and then naturally cooled in the furnace to a temperature of <55℃ before being removed from the furnace, thus producing a gas-sealed joint between single crystal diamond and oxygen-free copper.

2. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, In step one, the single-crystal diamond substrate is prepared by CVD or HPHT with {100} crystal plane orientation, and is finely polished on both sides until the surface roughness Ra≤0.05μm and flatness≤1μm. In step two, the {100} face of the single-crystal diamond substrate is placed facing the solder foil side.

3. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, In step one, the surface cleaning and activation treatment of the single-crystal diamond substrate includes the following steps in sequence: ultrasonic cleaning with acetone for 20 min; ultrasonic cleaning with anhydrous ethanol for 10 min; treatment with a mixture of concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 at 65-75℃ for 8-12 min; thorough rinsing with deionized water until neutral; soaking in 10wt% hydrochloric acid for 4-6 min; rinsing with deionized water; dehydration with isopropanol; and drying with high-purity nitrogen gas with a purity ≥99.999%.

4. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, In step one, the surface cleaning and activation treatment of the oxygen-free copper TU1 packaging frame includes the following steps in sequence: grinding the stepped sealing surface with 2000-grit sandpaper until the surface roughness Ra≤0.4μm; ultrasonic cleaning with acetone for 10min; soaking in 10wt% dilute sulfuric acid for 30s to remove surface copper oxide; ultrasonic cleaning with deionized water for 10min; ultrasonic cleaning with ethanol for 5min to dehydrate; drying with high-purity nitrogen; and drying in a drying oven at ≤50℃.

5. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, In step two, the composition of the active solder preformed foil, by mass fraction, is: Ag 57%-63%, Cu 22%-26%, Sn 10.5%-13.5%, with the balance being Ti; wherein the sum of the mass fractions of Ag, Cu, and Sn does not exceed 100%, the sum of the mass fractions of each component is 100%, and its liquidus temperature is 775-790℃.

6. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, In step two, a uniform pre-pressure is applied by an alumina ceramic process pressing block, and the contact surface between the alumina ceramic process pressing block and the single crystal diamond substrate is finely ground to a flatness of ≤2μm.

7. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, In step two, the time interval between the completion of the brazing assembly and its delivery into the vacuum brazing furnace shall not exceed 30 minutes.

8. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, The segmented heating program described in step three is as follows: the temperature is increased from room temperature to 300℃ at a rate of 5℃ / min, and held at 300℃ for 10min; then the temperature is increased from 300℃ to 500℃ at a rate of 5℃ / min, and held at 500℃ for 5min. The temperature is then increased from 500℃ to the peak brazing temperature at a rate of 2-3℃ / min.

9. The method for sealing single-crystal diamond and oxygen-free copper with extremely high hermeticity according to claim 1, characterized in that, Step three, after the diamond substrate exits the furnace, also includes a welding quality inspection step. Specifically, this involves: visual inspection using a 20x stereomicroscope to confirm that the diamond is free of cracks and chipping, the solder pool is free of porosity, and the weld is continuous; and using laser Raman spectroscopy to inspect the non-sealed areas of the diamond substrate, requiring a thickness of 1332 cm⁻¹. -1 The diamond characteristic peaks are clear and sharp, with the intensity ratio of the D peak to the G peak (ID / IG) ≤ 0.05; a sensitivity ≤ 1×10⁻⁶ was used. -12 Pa·m 3 A helium mass spectrometer leak detector with a speed of / s is used for airtightness testing. The pass standard is a leak rate ≤1×10⁻⁶. -10 Pa·m 3 / s; Interfacial contact thermal resistance is tested using the steady-state heat flow method, and the pass / fail standard is ≤3×10 -6 m 2 ·K / W.

10. A highly hermetic sealing structure for single-crystal diamond and oxygen-free copper, characterized in that, The method for preparing a highly hermetic seal between single-crystal diamond and oxygen-free copper according to any one of claims 1 to 9 comprises: a single-crystal diamond substrate, an active solder layer, and an oxygen-free copper TU1 encapsulation frame; the oxygen-free copper TU1 encapsulation frame has a stepped drill-bearing structure, the step depth is 0.10-0.25 mm, the ratio of the step width to the overlap of the single-crystal diamond substrate is 0.6-0.8, and the inner corner of the step has a rounded transition with a radius of 0.05-0.10 mm; the active solder layer is formed by brazing Ag-Cu-Sn-Ti preformed foil, and its thickness is less than the step depth; the hermetic leakage rate of the highly hermetic seal structure is ≤1×10⁻⁶. -10 Pa·m 3 / s, thermal resistance at the diamond-copper interface ≤3×10 -6 m 2 ·K / W.

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