Sapphire-kovar alloy connector and welding method thereof

Abstract

The invention provides a sapphire-Kovar alloy connector and a welding method thereof, and relates to the technical field of material connection, and the welding method of sapphire-Kovar alloy subjected to magnetron sputtering metallization treatment comprises the following steps: placing sapphire in an argon environment, performing magnetron sputtering on the surface of the sapphire for 10-50 minutes at the power of 90-200W, and taking out the sapphire; depositing a Ti layer of 80 to 750 nm on the surface of the sapphire; carrying out magnetron sputtering on the surface of the active layer at the power of 90-200W for 10-50 minutes so as to deposit a 100-1000nm brazing filler metal compatible layer on the surface of the active layer to obtain metallized sapphire; and the surface, with the brazing filler metal compatible layer, of the sapphire subjected to metallization treatment is assembled towards the Kovar alloy, brazing filler metal is taken and placed on the interface of the sapphire and the Kovar alloy, and vacuum welding is conducted.

Description

Technical Field

[0001] This invention relates to the field of material joining technology, and more specifically, to a sapphire-Kovar alloy joint and its welding method. Background Technology

[0002] Sapphire, with its high hardness, excellent corrosion resistance, and good optical transparency, has significant application value in high-end optical windows, semiconductor devices, and high-temperature sensors. Kovar alloy, as an iron-nickel-cobalt based material, has a thermal expansion coefficient that matches sapphire well and is widely used in the fabrication of hermetically sealed structures. However, the significant differences in chemical properties between sapphire and Kovar alloy result in insufficient interfacial affinity. Traditional brazing processes are prone to causing microscopic defects such as cracks and porosity, leading to decreased joint mechanical strength and sealing performance failure. To overcome these problems, related technologies generally employ an interlayer metallization strategy for interfacial modification. One common method is powder sintering, where a metal paste is coated onto the sapphire surface using screen printing, followed by high-temperature sintering to form a metallization layer, which is then brazed to the Kovar alloy. However, this method struggles to ensure the uniformity of the metallization layer, easily leading to uneven thickness distribution and interfacial contamination, weakening interlayer bonding and affecting joint reliability. Summary of the Invention

[0003] The present invention aims to solve the problem of poor uniformity of the metallization layer of sapphire and Kovar alloy.

[0004] To address the above problems, this invention provides a sapphire-Kovar alloy joint and its welding method.

[0005] In a first aspect, the present invention provides a method for welding sapphire-Kovar alloy treated by magnetron sputtering metallization, comprising the following steps: S1: Place the sapphire in an argon atmosphere and magnetron sputter it on the sapphire surface at a power of 90 to 200W for 10 to 50 minutes to deposit an active layer of 80 to 750 nm on the sapphire surface. The active layer is a Ti layer; S2: Magnetron sputtering at a power of 90 to 200 W for 10 to 50 minutes is performed on the surface of the active layer to deposit a solder compatible layer of 100 to 1000 nm on the surface of the active layer, thereby obtaining metallized sapphire. The solder compatibility layer is a Ni layer, an Ag layer, or a Cu layer; S3: Assemble the metallized sapphire with the solder-compatible surface facing Kovar alloy, place the solder at the interface between the sapphire and Kovar alloy, and perform vacuum soldering.

[0006] Optionally, during the deposition process, the sapphire and the magnetron sputtering target rotate relative to each other at a speed of 10 rpm or higher.

[0007] Optionally, before S1, the step further includes: in an argon atmosphere, argon gas is introduced to bombard the surface of the magnetron sputtering target with a power of 30 to 50 W to remove the target oxide on the surface of the magnetron sputtering target.

[0008] Optionally, the working pressure of the argon atmosphere shall not exceed 3.0 Pa.

[0009] Optionally, the argon flow rate in the argon atmosphere is 30 sccm.

[0010] Optionally, the welding temperature for vacuum welding is 810 to 870°C, and the holding time is 8 to 20 minutes.

[0011] Optionally, the solder is Ag-Cu-Ti solder.

[0012] Optionally, between S2 and S3, there is a step of vacuum encapsulating the metallized sapphire.

[0013] Optionally, the following steps may be included before S1: The sapphire was immersed in anhydrous ethanol and cleaned at room temperature in an ultrasonic cleaner to remove organic residues; after cleaning, it was dried in an electric heating drying oven at a temperature below 80°C and then vacuum sealed.

[0014] Secondly, the present invention provides a sapphire-Kovar alloy connector, which is manufactured using the sapphire-Kovar alloy welding method described above with magnetron sputtering metallization treatment.

[0015] The beneficial effects of the sapphire-Kovar alloy joint and its welding method of the present invention are as follows: the active Ti layer retains the active transition function and achieves atomic-level diffusion, while the solder compatible layer has the dual functions of stress buffering and wettability improvement, reducing process steps, avoiding interfacial stress introduced by multilayer stacking, and reducing the risk of impurity introduction between film layers. The double film directly uses Ti as the active layer, and the Ti layer reacts with sapphire to form an oxide transition layer, which strengthens the interfacial metallurgical bond. The Ni layer, Ag layer, or Cu layer serves as the solder compatible layer. The composition of the solder compatible layer inhibits interfacial oxidation and element diffusion, avoids the formation of brittle intermetallic compounds, and forms a synergistic effect of "pre-metallization + active brazing", simplifying the process, improving strength and ensuring interfacial integrity, making the interfacial reaction more controllable, and improving the reliability of the joint. Sputtering power (90 to 200 W) directly affects plasma density and deposition rate: Too low a power results in insufficient ion energy, leading to a low deposition rate and increasing the risk of discontinuities or porosity in the film, thus increasing oxidation risk; too high a power results in excessive ion bombardment, potentially causing excessive substrate temperature rise, leading to increased internal stress or lattice defects (such as microcracks) in the film. Sputtering time is the deposition time of metal atoms on the sapphire surface. Extending the magnetron sputtering time increases the thickness of the metallization layer. Controlling the sputtering time allows for precise control of the film thickness. Too short a time fails to form a sufficiently thick dense layer, weakening the protective effect of the transition layer; too long a time results in an excessively thick film, which may peel off due to stress accumulation. By setting the sputtering power and sputtering time, the desired bilayer film parameters can be obtained. Magnetron sputtering technology can achieve nanoscale precision deposition on the sapphire surface, ensuring a dense and uniform film, thereby suppressing interfacial oxidation and diffusion. It also enables stronger bonding between sapphire and Kovar alloys, reaching up to 200 MPa. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a welding method for sapphire-Kovar alloy subjected to magnetron sputtering metallization according to an embodiment of the present invention. Figure 2 This is a SEM image of the sapphire sample surface treated with magnetron sputtering metallization in Example 1. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this invention's description is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "comprising" and its variations as used herein are open-ended inclusion, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below.

[0019] like Figure 1 As shown, an embodiment of the present invention provides a welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization, comprising the following steps: S1: Place the sapphire in an argon atmosphere and magnetron sputter it on the sapphire surface at a power of 90 to 200W for 10 to 50 minutes to deposit an active layer of 80 to 750 nm on the sapphire surface. The active layer is a Ti layer; S2: Magnetron sputtering at a power of 90 to 200 W for 10 to 50 minutes is performed on the surface of the active layer to deposit a solder compatible layer of 100 to 1000 nm on the surface of the active layer, thereby obtaining metallized sapphire. The solder compatibility layer is a Ni layer, an Ag layer, or a Cu layer; S3: Assemble the metallized sapphire with the solder-compatible surface facing Kovar alloy, place the solder at the interface between the sapphire and Kovar alloy, and perform vacuum soldering.

[0020] Specifically, magnetron sputtering is a physical vapor deposition technique that uses a magnetic field to confine plasma, causing high-energy ions to bombard the target surface, thereby sputtering and depositing target atoms onto the substrate surface to form a thin film. This technique can achieve dense, uniform films with strong adhesion. Sapphire is a single-crystal alumina material with high hardness, strength, corrosion resistance, and light transmittance, and is commonly used in optical windows, semiconductor substrates, and other fields. Kovar is an iron-nickel-cobalt alloy with a coefficient of thermal expansion close to that of ceramic materials such as sapphire, and is often used to achieve hermetically sealed ceramic-metal bonding. The active layer refers to a chemically active metal film deposited on the sapphire surface. Its main function is to react with the sapphire substrate to form a transition layer, thereby enhancing the adhesion between the metal layer and the sapphire. In this embodiment, the active layer is specifically a titanium (Ti) layer. The solder compatibility layer refers to a metal film deposited on the surface of the active layer. Its main function is to improve the wettability of the subsequent solder on the metallized surface and to act as a diffusion barrier layer to inhibit excessive diffusion of interfacial elements, thereby optimizing the bonding quality of the solder interface. In this embodiment, the solder-compatible layer is specifically a nickel (Ni) layer, a silver (Ag) layer, or a copper (Cu) layer. Vacuum welding is a welding process performed in a vacuum environment. By eliminating oxygen and nitrogen from the air, oxidation and contamination of the metal during the welding process are avoided, which is beneficial for forming a clean and dense weld joint and improving the strength and reliability of the joint. An argon environment refers to placing the sapphire in a cavity filled with argon gas during magnetron sputtering. Argon, as an inert gas, is ionized during sputtering to form argon ions that bombard the target material, while simultaneously preventing oxidation or contamination of the substrate and deposited film.

[0021] In this embodiment, the active Ti layer retains its active transition function, achieving atomic-level diffusion, while the solder compatible layer serves a dual purpose of stress buffering and wettability enhancement, reducing process steps, avoiding interfacial stress introduced by multilayer stacking, and lowering the risk of impurity introduction between film layers. The bilayer film directly uses Ti as the active layer, where it reacts with sapphire to form an oxide transition layer, strengthening the interfacial metallurgical bond. The Ni, Ag, or Cu layers serve as the solder compatible layer, suppressing interfacial oxidation and element diffusion through the composition of the solder compatible layer, preventing the formation of brittle intermetallic compounds, and forming a synergistic effect of "pre-metallization + active brazing." This simplifies the process, improves strength, ensures interfacial integrity, makes interfacial reactions more controllable, and enhances joint reliability. The sputtering power (90 to 200 W) directly affects plasma density and deposition rate: too low a power results in insufficient ion energy, leading to a low deposition rate, discontinuities or porosity in the film, and increasing the risk of oxidation; too high a power results in excessive ion bombardment, potentially causing excessively high substrate temperatures, leading to increased internal stress or lattice defects (such as microcracks) in the film. Sputtering time refers to the deposition time of metal atoms on the sapphire surface. Extending the magnetron sputtering time increases the thickness of the metallization layer. Controlling the sputtering time allows for precise control of the film thickness. Too short a time fails to form a sufficiently thick, dense layer, weakening the protective effect of the transition layer; too long a time results in an excessively thick film, which may peel off due to stress accumulation. By setting the sputtering power and sputtering time, the desired bilayer film parameters are obtained. Magnetron sputtering technology can achieve nanoscale precision deposition on the sapphire surface, ensuring a dense and uniform film, thereby suppressing interfacial oxidation and diffusion. It also enables stronger bonding between sapphire and Kovar alloys, reaching up to 200 MPa.

[0022] Specifically, magnetron sputtering technology is used to precisely deposit an active layer and a solder-compatible layer on the surface of sapphire, constructing a dense and uniform double-layer metallized structure. This solves the problem of insufficient interfacial affinity and easy defect generation caused by the difference in chemical properties between sapphire and Kovar alloy. As a result, the bonding strength and sealing performance of the sapphire-Kovar alloy joint are improved, and thermal damage to sapphire caused by traditional high-temperature processes is avoided.

[0023] In some specific embodiments, sapphire can be mounted on the sample stage of a magnetron sputtering device. After the vacuum chamber is closed, a mechanical pump is first started to roughly evacuate the pressure to below 30 Pa, and then a molecular pump is started to evacuate to a high vacuum (≤5.0 × 10⁻⁶ Pa). -4A stable argon environment is established by evacuating the sapphire substrate and then introducing high-purity argon gas (flow rate 30 sccm), maintaining a working pressure of 3.0 Pa. The magnetron sputtering equipment maintains the sputtering power between 90W and 200W by adjusting the power output. The sputtering time can be set according to the required active layer thickness, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, or 50 minutes. The active layer is deposited on the sapphire surface, with a thickness ranging from 80 nm to 750 nm. Specifically, the active layer is a titanium (Ti) layer. As an active metal, the titanium layer can chemically react with the sapphire substrate to form a transition layer with bonding strength. After the active layer deposition is completed, the target material can be changed, and magnetron sputtering can continue under the same argon environment. The sputtering power is also maintained between 90W and 200W, and the sputtering time can be set to 30 minutes, 40 minutes, or 50 minutes to control the thickness of the solder-compatible layer. A solder-compatible layer, ranging in thickness from 100 nm to 1000 nm, is deposited on the surface of the active layer. Specifically, the solder-compatible layer can be a nickel (Ni), silver (Ag), or copper (Cu) layer. These materials improve wettability and inhibit oxidation, and act as a diffusion barrier layer, optimizing interfacial reactions during subsequent brazing. Metallized sapphire is aligned with Kovar alloy, ensuring contact between the metallized surface of the sapphire and the Kovar alloy. The solder, in the form of foil, paste, or preform, is placed between the interfaces to be joined of the sapphire and Kovar alloy. The entire assembly is then placed in a vacuum furnace for soldering. The vacuum environment helps prevent oxidation of the materials during soldering, ensuring joint quality. After soldering, the sapphire-Kova alloy joint is obtained by cooling.

[0024] Optionally, during the deposition process, the sapphire and the magnetron sputtering target rotate relative to each other at a speed of 10 rpm or higher.

[0025] Specifically, it is crucial to ensure that sputtered particles are uniformly deposited on the sapphire surface during magnetron sputtering. This relative rotation can be achieved in several ways. For example, the sapphire can be fixed to a substrate stage, and the stage can be rotated around its central axis using a drive mechanism; alternatively, the magnetron sputtering target can be rotated and scanned above the sapphire; or, the sapphire and the magnetron sputtering target can be rotated simultaneously at different speeds or directions to achieve the effect of relative rotation. This dynamic relative motion helps avoid over- or under-deposition in localized areas, thereby improving the uniformity of the film.

[0026] Limiting the relative rotational speed between the sapphire and the magnetron sputtering target to a speed of 10 rpm or higher ensures that the sapphire surface can continuously and rapidly renew the areas exposed to the sputtering particle stream during deposition. This can be achieved, for example, by precisely controlling the speed of the drive motor, such as using a closed-loop controlled servo motor system, or by adjusting the output frequency of an AC motor via a frequency converter. Alternatively, a mechanical transmission system, such as a gear set or pulley, can be used to precisely convert the motor's output speed into the rotational speed of the substrate stage or target to meet the speed requirement of 10 rpm or higher. This speed range effectively promotes the density and uniformity of the film, avoiding deposition unevenness problems caused by excessively low rotational speeds.

[0027] In this optional embodiment, during the magnetron sputtering deposition of the active layer and the solder-compatible layer, the sapphire and the magnetron sputtering target rotate relative to each other at a speed maintained above 10 rpm. This relative rotation mechanism ensures that sputtered particles uniformly cover the entire surface of the sapphire, effectively avoiding the problem of uneven local deposition caused by the sapphire remaining stationary. Specifically, the dynamic relative motion ensures that each point on the sapphire surface receives sputtered particles at different times, thereby eliminating the risk of film thickness fluctuations and increased porosity. Simultaneously, the rotation speed of over 10 rpm guarantees the continuity and speed of surface renewal, maintaining the dynamic balance of the deposition process and further promoting the density and uniformity of the film. Therefore, this solution significantly improves the quality and adhesion of the metallized film, thereby enhancing the reliability and strength of the weld joint and effectively solving the technical problems caused by uneven deposition.

[0028] Optionally, before S1, the step further includes: in an argon atmosphere, argon gas is introduced to bombard the surface of the magnetron sputtering target with a power of 30 to 50 W to remove the target oxide on the surface of the magnetron sputtering target.

[0029] Specifically, it is crucial to ensure that the magnetron sputtering target is in optimal condition before the active layer deposition, thus providing a pure source material for the subsequent sputtering process. This can be achieved as a separate pretreatment stage, completed before the actual sputtering; or as part of the sputtering equipment startup procedure, automatically executed after plasma ignition and before the actual deposition. The argon atmosphere is designed to provide an inert, oxygen-free environment to prevent re-oxidation of the target surface or the introduction of other reactive gas impurities during bombardment. Specifically, this can be achieved by evacuating the sputtering chamber and then filling it with high-purity argon, ensuring extremely low residual oxygen and water vapor content within the chamber; or by continuously introducing argon at a certain flow rate to dynamically remove potential contaminants from the chamber. The introduction of argon and bombardment of the magnetron sputtering target surface with specific power utilizes argon ions to physically etch the target surface, thereby removing oxides adhering to the target surface. This can be achieved by establishing argon plasma within the sputtering chamber and adjusting the power output of the radio frequency (RF) or direct current (DC) power supply to 30 to 50 W, thereby accelerating argon ions to bombard the target surface; or by setting up an independent ion source to generate an argon ion beam and controlling its energy and bombardment angle to achieve uniform etching of the target surface. Removing target oxides from the magnetron sputtering target surface is the core objective of this pretreatment step, as oxides can hinder the stable sputtering process and may be incorporated as impurities into the deposited film. This can be achieved by physically peeling or decomposing the oxide layer on the target surface through the aforementioned argon ion bombardment; or by combining appropriate target temperature control during bombardment to promote oxide desorption, thereby exposing a clean target surface.

[0030] In this optional embodiment, pre-bombardment treatment of the magnetron sputtering target surface before deposition of the active layer effectively removes oxides and other impurities from the target surface. This ensures that the deposition of the active layer (Ti layer) in the subsequent S1 step is carried out in a highly pure environment, preventing target oxides from being sputtered onto the sapphire surface as impurities, thereby significantly improving the purity and density of the deposited film. Combined with the aforementioned technique of relative rotation between the sapphire and the magnetron sputtering target to improve deposition uniformity, the removal of target oxides further guarantees the uniformity and adhesion of the deposited film, laying a solid foundation for the subsequent deposition of solder-compatible layers (Ni layer, Ag layer, or Cu layer), and ultimately improving the overall strength and reliability of the weld joint between the metallized sapphire and Kovar alloy.

[0031] Optionally, the working pressure of the argon atmosphere shall not exceed 3.0 Pa.

[0032] Specifically, the working pressure of the argon environment refers to the pressure maintained by argon gas within the vacuum chamber during magnetron sputtering. This pressure is a key parameter affecting the efficiency of argon ion bombardment of the magnetron sputtering target and the transport of sputtered particles. Achieving a working pressure of no more than 3.0 Pa for the argon environment can be achieved through various methods. For example, a high-precision vacuum pump system, combined with a flow controller and pressure sensor, can be used to precisely adjust the argon flow rate and pumping speed within the vacuum chamber to ensure the working pressure remains stable within the target range. Alternatively, the sealing performance of the vacuum chamber can be optimized to reduce leakage, and an automatic pressure control valve can be used to monitor and adjust the argon flow rate in real time, thereby precisely controlling the working pressure to a level no higher than 3.0 Pa.

[0033] In this optional embodiment, the working pressure of the argon environment is limited to no more than 3.0 Pa, which effectively solves the problems of poor bombardment effect and impurity introduction caused by excessive working pressure during the removal of oxides from the surface of magnetron sputtering targets. Specifically, the lower working pressure helps maintain the high density and stability of the argon plasma, allowing argon ions to bombard the surface of the magnetron sputtering target with higher energy and a more concentrated direction. This significantly improves the removal efficiency and thoroughness of the target surface oxides, ensuring the cleanliness of the magnetron sputtering target surface and providing pure source materials for subsequent active layer deposition. At the same time, the lower working pressure also reduces the probability of argon ions colliding with impurity gas molecules, thereby reducing the risk of impurities being introduced into the deposited film and ensuring the purity and quality of the film. Therefore, this technical solution not only optimizes the pretreatment effect of the magnetron sputtering target but also lays the foundation for subsequent high-quality metallization film deposition, thereby improving the overall performance and reliability of the sapphire-Kovar alloy weld joint.

[0034] Optionally, the argon flow rate in the argon atmosphere is 30 sccm.

[0035] Specifically, the argon gas flow rate refers to the rate at which inert argon gas enters the vacuum chamber during magnetron sputtering. Precise control of the argon gas flow rate is crucial during the target bombardment stage, as it directly affects the gas pressure and plasma density and uniformity within the chamber. Setting the argon gas flow rate to 30 sccm ensures the formation of a stable argon plasma with appropriate density at a specific chamber volume and pumping speed. This flow rate can be precisely controlled using a high-precision mass flow controller, such as a thermal or Coriolis mass flow controller, to monitor and adjust the argon gas input in real time, ensuring it remains stable at 30 sccm. This precise control helps optimize the bombardment effect of argon ions on the target surface, thereby efficiently and uniformly removing target oxides.

[0036] In this optional embodiment, the argon gas flow rate in the argon environment is precisely limited to 30 sccm, which effectively solves the problem of unstable plasma density and poor bombardment effect caused by inaccurate argon gas flow rate control. Specifically, in the step of bombarding the magnetron sputtering target surface to remove target oxides before S1, the precise argon gas flow rate ensures a stable plasma environment, allowing high-energy argon ions to bombard the target surface uniformly and continuously, thereby thoroughly removing the oxide layer on the target surface. This not only avoids the problem of insufficient adhesion or interface contamination of subsequent deposited films due to incomplete oxide removal, but also provides a clean and activated target surface for the subsequent deposition of active layers and solder-compatible layers, significantly improving the quality of the metallized film and the bonding strength with the sapphire substrate, thereby enhancing the overall reliability of the sapphire-Kovar joint.

[0037] Optionally, the welding temperature for vacuum welding is 810 to 870°C, and the holding time is 8 to 20 minutes.

[0038] Specifically, welding temperature is a key process parameter affecting the brazing process. This temperature range is designed to ensure that the selected brazing filler metal can fully melt and activate the reaction with the metallized layer and the sapphire interface, thereby promoting metallurgical bonding. Simultaneously, controlling the welding temperature between 810 and 870°C effectively avoids thermal stress damage to the sapphire material caused by excessive temperature, thus maintaining the structural integrity and optical properties of the sapphire. This temperature control can be achieved by precisely adjusting the heating power of the vacuum brazing furnace and using a high-precision temperature sensor for real-time feedback control. For example, an advanced PID (proportional-integral-derivative) controller can be used to precisely monitor and adjust the furnace temperature, ensuring that the temperature remains stable within the target range. Alternatively, a segmented heating strategy can be adopted, i.e., first heating at a relatively fast rate to near the brazing temperature, and then precisely heating at a slower rate to the set value of 810 to 870°C, to effectively reduce temperature overshoot and improve the accuracy of temperature control. Holding time refers to the duration for which the set welding temperature is maintained after it is reached. Its main purpose is to provide sufficient time for the brazing filler metal to fully wet, spread, and diffuse, enabling it to form a stable and uniform metallurgical bond with the metallization layer and Kovar alloy on the sapphire surface. By controlling the holding time to 8 to 20 minutes, it is possible to ensure sufficient interfacial reaction and form a strong joint, while avoiding increased energy consumption, excessive grain growth, or the formation of brittle phases due to excessively long holding times, thereby optimizing the microstructure and mechanical properties of the joint. This holding time is typically set through the programmable control system of the vacuum brazing furnace. Once the furnace temperature reaches the preset welding temperature, the timer will automatically start, and after reaching the preset 8 to 20 minutes, it will automatically enter the cooling stage, ensuring the automation and precision of the process.

[0039] In this optional embodiment, the vacuum welding temperature is precisely defined as 810 to 870°C and the holding time as 8 to 20 minutes. This effectively solves the problem of potential thermal damage to sapphire during the welding process and ensures sufficient reaction and bonding strength at the welding interface. Specifically, controlling the welding temperature to 810 to 870°C allows the brazing filler metal to fully melt and activate the interfacial reaction with the active layer (Ti layer) and brazing filler metal compatible layer (Ni layer, Ag layer, or Cu layer) deposited on the sapphire surface, promoting the formation of a stable metallurgical bond. Simultaneously, this temperature range is significantly lower than traditional high-temperature brazing processes, thus avoiding thermal stress damage to the sapphire caused by excessively high temperatures and protecting its material properties. Furthermore, setting the holding time to 8 to 20 minutes ensures sufficient time for the brazing filler metal to wet, diffuse, and react at the interface, resulting in a uniform, dense, and strong interfacial layer between the metallized sapphire and the Kovar alloy, avoiding insufficient bonding strength due to incomplete reaction. This precise temperature and time control, combined with the Ti-Ni / Ag / Cu double-layer metallization structure formed by magnetron sputtering and the active solder, significantly improves the reliability and mechanical properties of the sapphire-Kovar alloy joint while achieving low-temperature welding. It effectively avoids defects such as cracks and porosity commonly found in traditional methods, thus obtaining a high-strength and highly airtight connection.

[0040] Optionally, the solder is Ag-Cu-Ti solder.

[0041] Specifically, Ag-Cu-Ti solder is an active solder whose main components are silver (Ag), copper (Cu), and titanium (Ti). Silver and copper typically form the main matrix of the solder, providing good wettability and plasticity, and forming a eutectic system to lower the melting point. Titanium, as an active element, can chemically react with ceramic materials (such as sapphire) to form stable compounds, thereby achieving a metallurgical bond between ceramic and metal. This solder can exist in various forms; for example, it can be a pre-formed solder foil for precise placement on the interface to be soldered; or it can be a solder paste, applied to the soldering area by dispensing or printing. Furthermore, the preparation of this solder typically employs processes such as vacuum melting or powder metallurgy to ensure its compositional uniformity and purity, thereby guaranteeing soldering performance.

[0042] In this optional embodiment, the use of Ag-Cu-Ti solder effectively solves the problems of insufficient interfacial reaction, low bonding strength, and excessively high welding temperature caused by improper solder selection. Specifically, the active element titanium in the Ag-Cu-Ti solder can form chemical continuity with the pre-deposited titanium layer on the sapphire surface, thereby promoting metallurgical bonding between the sapphire and the solder during welding, forming a stable oxide transition layer, stabilizing the brazing interface, and significantly enhancing the bonding strength of the interface. Simultaneously, this solder system has a low eutectic temperature, allowing the welding temperature of vacuum welding to be controlled within the range of 810 to 870°C, avoiding potential thermal damage to the sapphire at high temperatures, thus improving the reliability and repeatability of the joint. Furthermore, the synergistic effect of the Ag-Cu-Ti solder and the solder-compatible layer (such as a Ni layer, Ag layer, or Cu layer) deposited on the sapphire surface can effectively suppress the formation of brittle intermetallic compounds at the interface, further ensuring the strength and sealing performance of the joint, achieving a synergistic effect of "pre-metallization + active brazing," thereby simplifying the process, improving joint strength, and ensuring interface integrity.

[0043] Optionally, between S2 and S3, there is a step of vacuum encapsulating the metallized sapphire.

[0044] Specifically, vacuum encapsulation refers to placing metallized sapphire in a vacuum environment and sealing it to isolate it from contact with the external atmosphere (such as oxygen and water vapor), thereby protecting the metallized layer from oxidation or contamination. For example, the metallized sapphire can be placed in a pre-vacuumed rigid container, such as a stainless steel vacuum canister or a glass vacuum chamber, and then the container can be sealed and connected to a vacuum pump to continuously maintain the internal vacuum level. Alternatively, the metallized sapphire can be placed in a flexible bag made of a high-barrier polymer film, and the air inside the bag can be extracted by a vacuum pump before heat sealing or cold sealing to form a sealed vacuum package. In addition, after vacuuming, high-purity inert gas can be filled into the encapsulation container to form an inert gas protective environment to further isolate oxygen and water vapor. For example, after encapsulation, continuous vacuum storage can be used, placing the encapsulated metallized sapphire in a storage device connected to a vacuum pump, and continuously vacuuming or maintaining a high vacuum level. Alternatively, high-barrier sealed packaging can be used, which involves sealing the packaging with materials that have extremely low gas permeability (such as aluminum-plastic composite film or special glass). After the initial vacuuming, the packaging material itself provides barrier properties, and vacuum packaging is performed within 4 hours after magnetron sputtering metallization to effectively maintain the internal vacuum or low-pressure environment and prevent external gases from penetrating.

[0045] In this optional embodiment, the metallized sapphire is vacuum-encapsulated after the solder compatibility layer deposition and before vacuum soldering, effectively preventing oxidation, contamination, and degradation caused by exposure of the metallization layer to air. This vacuum environment ensures that the active layer and solder compatibility layer maintain their original cleanliness and high activity, providing ideal interface conditions for subsequent vacuum soldering. Therefore, during the subsequent vacuum soldering process, the solder can better wet the metallized surface, promoting the formation of a dense and uniform metallurgical bond, significantly improving the bonding strength and long-term reliability of the sapphire-Kovar joint, and effectively solving the problem of soldering defects caused by interface contamination or oxidation.

[0046] Optionally, the following steps may be included before S1: The sapphire was immersed in anhydrous ethanol and cleaned at room temperature in an ultrasonic cleaner to remove organic residues. After cleaning, it was dried in an electrically heated drying oven at a temperature below 80°C and then vacuum-sealed to prevent recontamination. This step provides a clean interface for subsequent metallization.

[0047] Specifically, sapphire is immersed in anhydrous ethanol to effectively remove organic contaminants such as grease, fingerprints, and dust from the sapphire surface, utilizing the strong solubility of anhydrous ethanol. Anhydrous ethanol has good volatility and is non-corrosive to the sapphire matrix. Besides anhydrous ethanol, organic solvents such as acetone and isopropanol can also be used for immersion cleaning, as these solvents can also effectively dissolve various organic residues. Subsequently, the sapphire is cleaned at room temperature in an ultrasonic cleaner. This step utilizes the high-frequency vibrations generated by the ultrasonic cleaner to create a cavitation effect in the liquid, producing numerous microbubbles that rapidly burst, thus performing microscopic mechanical scrubbing on the sapphire surface and removing contaminants. Room temperature cleaning avoids the thermal stress or damage to the sapphire material that may be introduced by excessively high temperatures. In addition to ultrasonic cleaning, high-pressure spray cleaning can also be used, utilizing the impact force of high-pressure liquid streams to remove surface contaminants; or brushing combined with cleaning fluid can be used to remove stubborn stains through physical friction. This cleaning process aims to thoroughly remove organic residues. If these residues are not completely removed, they will hinder the direct contact and bonding of metal atoms with the sapphire surface during subsequent magnetron sputtering metallization, forming interface defects, reducing the adhesion and uniformity of the metallization layer, and consequently affecting the final welding quality and joint strength. After cleaning, the sapphire is dried in an electrically heated drying oven at below 80°C for 15 minutes. This step aims to thoroughly remove any residual cleaning solution and moisture from the sapphire surface. Maintaining the temperature below 80°C is to avoid potential thermal damage or the introduction of new stress to the sapphire material, while ensuring sufficient evaporation of solvents and moisture to prevent bubble formation or interference with film deposition in the subsequent vacuum environment. In addition to drying in an electrically heated drying oven, nitrogen purging can be used to remove surface liquids using a high-purity nitrogen stream; alternatively, low-temperature vacuum drying in a vacuum oven can further reduce the drying temperature and accelerate solvent evaporation. After drying, the sapphire is vacuum-sealed to prevent recontamination. After cleaning and drying, the sapphire surface is highly clean and extremely susceptible to secondary contamination from dust, moisture, or other volatile substances in the air. Vacuum sealing effectively isolates the sapphire from the external environment, maintaining its surface cleanliness until the next metallization process. Besides vacuum sealing, it can also be sealed and stored in an inert gas environment (such as high-purity argon or nitrogen) to prevent oxidation and the adsorption of airborne contaminants. This step provides a clean interface for subsequent metallization.

[0048] In this optional embodiment, the sapphire undergoes thorough pre-cleaning and protection before magnetron sputtering metallization, effectively solving the problem of interface contamination caused by organic residues on the sapphire surface. Specifically, the dissolving effect of anhydrous ethanol combined with the mechanical cleaning effect of ultrasound can efficiently and gently remove various organic contaminants from the sapphire surface, avoiding the damage that may be introduced by traditional cleaning methods. Subsequently, low-temperature drying ensures the complete removal of cleaning agents and moisture, while vacuum sealing effectively isolates secondary contamination from the external environment, thus providing an extremely clean substrate interface for the subsequent magnetron sputtering deposition of the active layer and the solder-compatible layer. This clean interface greatly promotes the atomic-level bonding between the metallization layer and the sapphire, improving the density, uniformity, and adhesion of the film, and effectively suppressing the generation of interface defects. When combined with subsequent magnetron sputtering metallization and active brazing, it ensures that the metallization layer can stably and firmly adhere to the sapphire surface and form good wetting and metallurgical bonding with the solder, ultimately significantly improving the welding strength and sealing reliability of the sapphire-Kovar joint, avoiding welding defects and performance degradation caused by interface contamination.

[0049] Another embodiment of the present invention provides a sapphire-Kovar alloy connector, which is manufactured using the sapphire-Kovar alloy welding method described above with magnetron sputtering metallization treatment.

[0050] Specifically, a sapphire-Kova alloy joint refers to a composite structural component formed by welding sapphire and Kovar alloy together. This joint utilizes a specific manufacturing process to create a stable connection at the interface between the sapphire and Kovar alloy. The phrase "manufactured using a sapphire-Kova alloy welding method with magnetron sputtering metallization" means that the structure and performance of the joint, particularly its interface characteristics, are directly imparted by the welding method. For example, the joint has an active layer and a solder-compatible layer deposited on the sapphire surface using magnetron sputtering technology. These layers have specific thickness, uniformity, and density, ensuring good bonding between the sapphire and the metal layers, and between the metal layers and the solder. Furthermore, the joint is formed through vacuum welding, resulting in an optimized microstructure at the welding interface, effectively avoiding common defects in traditional welding methods, such as porosity, cracks, or the formation of brittle phases. Another approach is that the connector exhibits high strength and excellent sealing performance, which is due to the formation of an atomically bonded metallization layer on the sapphire surface by magnetron sputtering technology, combined with active solder for welding in a vacuum environment, thereby achieving a reliable connection at both the macroscopic and microscopic levels.

[0051] In this embodiment, the sapphire-Kovar alloy joint inherits the advantages of the aforementioned magnetron sputtering metallization treatment method for sapphire-Kovar alloys. Specifically, by depositing a nanoscale active layer and a solder-compatible layer on the sapphire surface using magnetron sputtering technology, dense and uniform film deposition can be achieved, effectively suppressing interfacial oxidation and diffusion, thus providing an ideal interfacial foundation for subsequent welding. This joint avoids the problems of uneven film layer and interfacial contamination caused by traditional powder sintering methods, significantly improving the interfacial bonding strength. Simultaneously, by precisely controlling the sputtering power and time, the continuous effect of the active element Ti is ensured, strengthening the interfacial metallurgical bond and effectively suppressing the formation of brittle phases. Furthermore, combined with vacuum welding technology, defects during the welding process, such as porosity and cracks, can be minimized, thereby solving the problems of insufficient interfacial bonding strength and sealing failure, significantly improving the reliability and mechanical properties of the sapphire-Kovar alloy joint. This joint further optimizes the quality of the metallization layer and the stability of the weld interface by controlling the relative rotation of the sapphire and magnetron sputtering target, the pre-bombardment of the target in an argon atmosphere, the working pressure and flow rate of the argon atmosphere, and the precise control of the vacuum welding temperature and holding time.

[0052] The present invention will be further described below with reference to specific embodiments.

[0053] Example 1: A welding method for sapphire-Kovar alloy treated with magnetron sputtering metallization, comprising the following steps: 1. Inspect the sapphire surface using an optical microscope in a clean bench to ensure there are no scratches or chipped edges. Then, immerse the sapphire sample in anhydrous ethanol and clean it in an ultrasonic cleaner at room temperature for 10 minutes to remove organic residues. After cleaning, dry it in an 80°C electric heating oven for 15 minutes, then vacuum seal it to prevent recontamination. This step provides a clean interface for subsequent metallization.

[0054] 2. Mount the pretreated sapphire onto the sample stage of the magnetron sputtering equipment for vacuum deposition: High vacuum: After closing the vacuum chamber, first start the mechanical pump to roughly pump the pressure down to below 30 Pa, then start the molecular pump to evacuate to 5.0 × 10⁻⁶ Pa. -4 Pa.

[0055] Pre-sputtering cleaning of target materials: Argon gas with a flow rate of 30 sccm is introduced and the working pressure is maintained at 3.0 Pa. Ti target and Ni target are pre-sputtered in sequence with sputtering power of 30 and time of 5 minutes to remove oxides from the target surface.

[0056] Depositing the Ti layer: Maintain the argon flow rate and pressure, open the Ti target baffle, set the sputtering power to 180 W and the deposition time to 50 minutes, and sputter a Ti layer of 750±20 nm on the sapphire surface. Control the sample stage rotation speed to 10 rpm to ensure film thickness uniformity.

[0057] Ni layer deposition: Under the same conditions, switch to Ni target, set sputtering power to 180 W and deposition time to 50 minutes, and form a Ni layer with a thickness of about 500±30 nm on the Ti layer as a brazing transition layer to suppress interface diffusion and oxidation.

[0058] After deposition, the gas is slowly released and samples are taken. The samples must be vacuum-sealed within 4 hours to prevent film degradation. The surface of the magnetron sputtered metallized sapphire samples was examined using a scanning electron microscope (SEM). The SEM images are shown below. Figure 2 As shown, the thickness of the Ti layer sputtered on the sapphire surface is 750±20 nm, and the thickness of the Ni layer is about 500±30 nm.

[0059] 3. Brazing connection of sapphire-Kovar alloy Metallized sapphire and Kovar alloy were assembled into a laminated structure, with Ag-Cu-Ti solder placed at the interface, and joined in a vacuum brazing furnace. The brazing parameters were: temperature 810℃, holding time 20 minutes. After cooling, the tensile strength of the sapphire-Kovar alloy joint was measured to be 129 MPa.

[0060] Example 2, a welding method for sapphire-Kovar alloy treated with magnetron sputtering metallization, comprising the following steps: 1. Inspect the sapphire surface using an optical microscope in a clean bench to ensure there are no scratches or chipped edges. Then, immerse the sapphire sample in anhydrous ethanol and clean it in an ultrasonic cleaner at room temperature for 10 minutes to remove organic residues. After cleaning, dry it in an 80°C electric heating oven for 15 minutes, then vacuum seal it to prevent recontamination. This step provides a clean interface for subsequent metallization.

[0061] 2. Mount the pretreated sapphire onto the sample stage of the magnetron sputtering equipment for vacuum deposition: High vacuum: After closing the vacuum chamber, first start the mechanical pump to roughly pump the pressure down to below 30 Pa, then start the molecular pump to evacuate to 5.0 × 10⁻⁶ Pa. -4 Pa.

[0062] Pre-sputtering cleaning of target materials: Argon gas with a flow rate of 30 sccm is introduced and the working pressure is maintained at 3.0 Pa. Ti target and Ni target are pre-sputtered in sequence with a sputtering power of 50 and a time of 3 minutes to remove oxides from the target surface.

[0063] Depositing the Ti layer: Maintain the argon flow rate and pressure, open the Ti target baffle, set the sputtering power to 180 W and the deposition time to 10 minutes, and sputter a 150 nm Ti layer on the sapphire surface. Control the sample stage rotation speed to 10 rpm to ensure film thickness uniformity.

[0064] Ni layer deposition: Under the same conditions, switch to Ni target, set sputtering power to 180 W and deposition time to 30 minutes, and form a Ni layer with a thickness of about 300 nm on the Ti layer as a brazing transition layer to suppress interface diffusion and oxidation.

[0065] After deposition, slowly release the gas and take samples. The samples must be vacuum sealed within 4 hours to avoid film degradation.

[0066] 3. Brazing connection of sapphire-Kovar alloy Metallized sapphire and Kovar alloy were assembled into a laminated structure, with Ag-Cu-Ti solder placed at the interface, and joined in a vacuum brazing furnace. The brazing parameters were: temperature 850℃, holding time 15 minutes. After cooling, the tensile strength of the sapphire-Kovar alloy joint was measured to be 200 MPa.

[0067] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A welding method for sapphire-Kovar alloy treated with magnetron sputtering metallization, characterized in that, Includes the following steps: S1: Place the sapphire in an argon atmosphere and magnetron sputter it on the sapphire surface at a power of 90 to 200W for 10 to 50 minutes to deposit an active layer of 80 to 750 nm on the sapphire surface. The active layer is a Ti layer; S2: Magnetron sputtering at a power of 90 to 200 W for 10 to 50 minutes is performed on the surface of the active layer to deposit a solder compatible layer of 100 to 1000 nm on the surface of the active layer, thereby obtaining metallized sapphire. The solder-compatible layer is a Ni layer, an Ag layer, or a Cu layer; S3: Assemble the metallized sapphire with the surface having the solder compatible layer facing Kovar alloy, place the solder at the interface between the sapphire and the Kovar alloy, and perform vacuum soldering.

2. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 1, characterized in that, During the deposition process, the sapphire rotates relative to the magnetron sputtering target at a speed of 10 rpm or higher.

3. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 2, characterized in that, Before step S1, the method further includes the following step: in an argon atmosphere, argon gas is introduced at a power of 30 to 50 W to bombard the surface of the magnetron sputtering target to remove the target oxide on the surface of the magnetron sputtering target.

4. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 3, characterized in that, The working pressure of the argon atmosphere is no higher than 3.0 Pa.

5. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 3, characterized in that, The argon gas flow rate in the argon environment is 30 sccm.

6. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 1, characterized in that, The vacuum welding temperature is 810 to 870°C, and the holding time is 8 to 20 minutes.

7. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 1, characterized in that, The solder is Ag-Cu-Ti solder.

8. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 1, characterized in that, Between S2 and S3, the step of vacuum encapsulating the metallized sapphire is included.

9. The welding method for sapphire-Kovar alloy treated by magnetron sputtering metallization according to claim 1, characterized in that, The step preceding S1 includes: The sapphire was immersed in anhydrous ethanol and cleaned at room temperature in an ultrasonic cleaner to remove organic residues; after cleaning, it was dried in an electric heating drying oven at a temperature below 80°C and then vacuum sealed.

10. A sapphire-Kovar alloy connector, characterized in that, It is manufactured using the sapphire-Kovar alloy welding method described in any one of claims 1-9, which involves magnetron sputtering metallization.

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