Preparation method of self-propagating reaction brazing film and auxiliary high-temperature brazing method

Abstract

The invention relates to the technical field of welding, and discloses a self-propagating reaction brazing film preparation method and an auxiliary high-temperature brazing method.The self-propagating reaction brazing film preparation method at least comprises the following steps that a first solder layer is deposited on a substrate; depositing a first transition layer on the first solder layer; alternately depositing a nano multilayer film structure on the first transition layer; depositing a second transition layer on one side, far away from the first solder layer, of the nano multilayer film structure; and a second solder layer is deposited on the side, away from the first solder layer, of the second transition layer, so that the composite brazing film is formed. According to the preparation method of the self-propagating reaction brazing thin film, integrated preparation of the solder layer, the transition layer and the multiple self-propagating thin film layers can be achieved, and the production speed of the composite brazing thin film is increased.

Description

Technical Field

[0001] This application relates to the field of welding technology, and in particular to a method for preparing a self-propagating reaction brazing film and an auxiliary high-temperature brazing method. Background Technology

[0002] Soft soldering is an important method for connecting electronic materials, typically using low-melting-point solders such as indium, tin, and tin-based solders, with melting points between 156°C and 232°C. Traditional soft soldering involves heating the two substrates to be soldered (e.g., two chips or two casings) separately to a preset temperature above the solder's melting point, applying solder to the substrate surface to wet it, and then cooling the two substrates together to room temperature. This method of heating both the solder and the substrate as a whole can cause significant deformation when soldering dissimilar materials with significantly different thermophysical properties, especially when cooling from the soldering temperature to room temperature due to their different coefficients of linear expansion. This deformation is particularly severe when soldering large, thin, dissimilar materials. Furthermore, the soldering process usually requires the addition of flux or the use of a protective atmosphere to prevent solder oxidation, which reduces solder quality.

[0003] The self-propagating exothermic reaction of nano-active thin films originates from self-propagating high-temperature synthesis technology. This technology utilizes the heat of reaction generated between reactants and its self-conduction to weld materials, and can be used to prepare some ceramics, intermetallic compounds, and composite materials. However, related self-propagating high-temperature synthesis technologies cannot achieve the integrated preparation of solder layers, transition layers, and multiple self-propagating thin film layers. The process requires manual mounting of pre-formed solder pieces on both sides of the film, which is complex. Furthermore, the manual mounting of pre-formed solder pieces is prone to interface oxidation and contamination, leading to problems such as voids and incomplete welds. Additionally, the weld width is too large after welding, the workpiece is uneven after welding, and due to the lack of a wetting transition layer, the solder cannot spread quickly, resulting in welding defects. Summary of the Invention

[0004] This application provides a method for preparing a self-propagating reactive brazing film and an auxiliary high-temperature brazing method, which can realize the integrated preparation of a solder layer, a transition layer, and multiple self-propagating film layers, thereby improving the production speed of composite brazing films.

[0005] To achieve the above objectives, the main technical solutions adopted in this application include: In a first aspect, embodiments of this application provide a method for preparing a self-propagating reactive brazing thin film, comprising at least the following steps: Deposit the first solder layer on the substrate; A first transition layer is deposited on the first solder layer; A nano-multilayer film structure is alternately deposited on the first transition layer; A second transition layer is deposited on the side of the nanomultilayer film structure away from the first solder layer; A second solder layer is deposited on the side of the second transition layer away from the first solder layer to form a composite brazing film.

[0006] The method for preparing self-propagating reactive brazing films and assisting high-temperature brazing according to this application involves the sequential deposition of a first solder layer, a first transition layer, a nano-multilayer film structure, a second transition layer, and a second solder layer. Therefore, the solder layer, transition layer, and multilayer self-propagating film layers can be prepared in an integrated manner, which is simple to operate, has better forming efficiency, and improves the production speed of composite brazing films. At the same time, since a first transition layer is set between the first solder layer and the nano-multilayer film structure, and a second transition layer is set between the second solder layer and the nano-multilayer film, the structure of the composite brazing film is more stable, ensuring the yield of composite brazing films.

[0007] Meanwhile, due to the integrated preparation of the solder layer, transition layer, and multi-layer self-propagating thin film layer, the probability of interface oxidation and contamination caused by the existing technology of "requiring manual mounting of pre-formed solder pieces on both sides of the film" can be reduced, effectively alleviating problems such as voids, incomplete welds, excessive weld width, and unevenness of the workpiece to be welded after welding.

[0008] According to one embodiment of this application, depositing the first solder layer on the substrate includes: The first solder layer is deposited on the substrate using electron beam physical vapor deposition. The thickness of the first solder layer is t1, and the thickness of the nano-multilayer film structure is d, satisfying: d / 10≤t1≤d / 2.

[0009] According to one embodiment of this application, before depositing the first solder layer on the substrate, the substrate is ground and polished to a mirror finish, and the polished substrate is ultrasonically cleaned in deionized water and alcohol for 3-5 minutes in sequence, and then dried.

[0010] According to one embodiment of this application, grinding and polishing the substrate to a mirror finish includes: The substrate was sanded layer by layer with 200-grit sandpaper, 400-grit sandpaper, 600-grit sandpaper, 800-grit sandpaper and 1000-grit sandpaper until the surface of the base material was smooth and flat, and then polished to a mirror finish with a polishing machine.

[0011] According to one embodiment of this application, the first transition layer includes at least one of AgCuIn transition layer, AgCu transition layer, Au transition layer, Ag transition layer, and nickel-gold transition layer, and the thickness of the first transition layer is t2, satisfying: 100nm≤t2≤1μm; and / or The second transition layer is an AgCuIn transition layer, and the thickness of the second transition layer is t3, which satisfies: 100nm≤t3≤1μm.

[0012] According to one embodiment of this application, the components of the first solder layer and the second solder layer include at least one of low-melting-point Sn-based solder, Al-based solder, Zn-based solder, and Ag-based solder.

[0013] In a first aspect, embodiments of this application provide an assisted high-temperature brazing method using a composite brazing film, wherein the composite brazing film is prepared by the above-described self-propagating reaction brazing film preparation method, and the assisted high-temperature brazing method includes at least the following steps: The composite brazing film is peeled off from the substrate and placed between the two workpieces to be welded; The composite brazing film is activated for welding to fix the two workpieces to be welded.

[0014] According to one embodiment of this application, the assisted high-temperature brazing method further includes: The workpiece to be welded undergoes surface pretreatment. Place the workpiece to be welded in deionized water and alcohol in sequence for ultrasonic cleaning for 3-5 minutes, and then dry it. The obtained workpiece to be welded is combined with the composite brazing film and a certain pressure is applied and held; After preheating the combination of the workpiece to be welded and the composite brazing film, the composite brazing film is activated by a specific excitation method for welding.

[0015] According to one embodiment of this application, the pressure applied to the combination of the workpiece to be welded and the composite brazing film is 1MPa-10MPa, and the preheating temperature for the combination of the workpiece to be welded and the composite brazing film is 50℃-200℃. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a method for preparing a self-propagating reactive brazing film according to an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of 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, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0020] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0021] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0022] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0023] In this application, "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0024] Soft soldering is an important method for connecting electronic materials, typically using low-melting-point solders such as indium, tin, and tin-based solders, with melting points between 156°C and 232°C. Traditional soft soldering involves heating the two substrates to be soldered (e.g., two chips or two casings) separately to a preset temperature above the solder's melting point, applying solder to the substrate surface to wet it, and then cooling the two substrates together to room temperature. This method of heating both the solder and the substrate as a whole can cause significant deformation when soldering dissimilar materials with significantly different thermophysical properties, especially when cooling from the soldering temperature to room temperature due to their different coefficients of linear expansion. This deformation is particularly severe when soldering large, thin, dissimilar materials. Furthermore, the soldering process usually requires the addition of flux or the use of a protective atmosphere to prevent solder oxidation, which reduces solder quality.

[0025] Related electronic packaging solder interconnect processes are typically implemented under overall device heating, often employing one or more interconnection methods such as wire bonding, direct bonding, diffusion bonding, anodic bonding, conductive adhesive interconnection, and eutectic solder interconnection for manufacturing and packaging. However, the overall heating methods used in these technologies can easily damage heat-sensitive, thermally mismatched components and materials inside the device. During the heating process, at the connection joints between different devices, due to the different coefficients of thermal expansion of the interconnecting materials, thermal stress concentrated at the interface will form, leading to a decrease in package reliability. At the same time, some heat-sensitive biomaterials and unstable amorphous materials cannot withstand the high temperatures reached during overall heating, and cannot be interconnected using conventional heating methods.

[0026] The self-propagating exothermic reaction of nano-active thin films originates from self-propagating high-temperature synthesis technology. This technology utilizes the heat of reaction generated between reactants and its self-conduction to weld materials, and can be used to prepare some ceramics, intermetallic compounds, and composite materials. However, related self-propagating high-temperature synthesis technologies cannot achieve the integrated preparation of solder layers, transition layers, and multiple self-propagating thin film layers. The process requires manual mounting of pre-formed solder pieces on both sides of the film, which is complex. Furthermore, the manual mounting of pre-formed solder pieces is prone to interface oxidation and contamination, leading to problems such as voids and incomplete welds. Additionally, the weld width is too large after welding, the workpiece is uneven after welding, and due to the lack of a wetting transition layer, the solder cannot spread quickly, resulting in welding defects.

[0027] Multilayer films with specific nanostructures can undergo self-propagating reactions under the induction of external energy. The exothermic reaction can instantly generate high temperatures of 1000℃ to 3000℃. On the one hand, it can melt the solder, and on the other hand, it can directly achieve the connection of materials by means of its reaction products.

[0028] Because of their thin thickness, typically ranging from a few micrometers to tens of micrometers, nanomultilayer films can achieve extremely fast cooling rates, ensuring that the original morphology of the connected materials is not destroyed. Therefore, nanomultilayer films can serve as a potential heat source for connecting micro and nano units.

[0029] The self-propagating process of nano-multilayer films requires low ignition energy, and the connection process is completed after the reaction. This saves energy and has high connection efficiency. It can achieve the connection of base materials with different coefficients of thermal expansion, effectively reduce the thermal stress generated during welding, reduce weld defects, and improve welding quality.

[0030] This application proposes a method for preparing a self-propagating reaction brazing thin film, which includes at least the following steps: Deposit the first solder layer on the substrate; A first transition layer is deposited on the first solder layer; A nano-multilayer film structure is alternately deposited on the first transition layer; A second transition layer is deposited on the side of the nanomultilayer film structure away from the first solder layer; A second solder layer is deposited on the side of the second transition layer away from the first solder layer to form a composite brazing film; The composite brazing film is peeled off from the substrate and placed between the two workpieces to be welded; The composite brazing film is activated for welding to fix the two workpieces to be welded.

[0031] It should be noted that the substrate can be a Cu substrate, but other different metal materials can also be used as the substrate; there are no restrictions here.

[0032] Because a first transition layer is provided between the first solder layer and the nano-multilayer film structure, the connection between the nano-multilayer film structure and the first solder layer can be made tighter, thereby improving the structural stability of the composite brazing film.

[0033] Similarly, a second transition layer is provided between the second solder layer and the nano-multilayer film structure, which makes the connection between the nano-multilayer film structure and the second solder layer tighter, thereby improving the structural stability of the composite brazing film.

[0034] Since the composite brazing multilayer film structure in this application is formed by the sequential deposition of a first solder layer, a first transition layer, a nano-multilayer film structure, a second transition layer, and a second solder layer, the integral preparation of the solder layer, transition layer, and multilayer self-propagating thin film layers can be achieved. This simplifies the operation, improves the forming efficiency, and increases the production speed of the composite brazing film. Furthermore, since a first transition layer is provided between the first solder layer and the nano-multilayer film structure, and a second transition layer is provided between the second solder layer and the nano-multilayer film, the structure of the composite brazing film is more stable, ensuring the yield of the composite brazing film.

[0035] Meanwhile, due to the integrated preparation of the solder layer, transition layer, and multi-layer self-propagating thin film layer, the probability of interface oxidation and contamination caused by the existing technology of "requiring manual mounting of pre-formed solder pieces on both sides of the film" can be reduced, effectively alleviating problems such as voids, incomplete welds, excessive weld width, and unevenness of the workpiece to be welded after welding.

[0036] According to the self-propagating reaction brazing film preparation method of this application, the self-propagating reaction is used as an auxiliary heating source to perform high-temperature brazing of dissimilar materials, which is conducive to the complete melting of the brazing filler layer and wetting of the base material surface, thereby improving the connection efficiency and forming a high-strength, low-porosity bonding interface.

[0037] Furthermore, the thin thickness of the intermediate nanolayer multilayer film structure, typically between a few micrometers and tens of micrometers, allows for extremely rapid cooling, ensuring that the original morphology of the joined materials remains intact. The self-propagating process of the nanolayer multilayer film structure requires low ignition energy, saving energy and offering high connection efficiency, effectively reducing thermal stress generated during welding. The weld seam after welding is smooth, and the porosity of the device is extremely low, making it suitable for large-area, large-size welding. As a high-speed welding consumable, it offers considerable production capacity.

[0038] In some embodiments of this application, a first solder layer is deposited on the substrate using electron beam physical vapor deposition. The thickness of the first solder layer is t1, and the thickness of the nano-multilayer film structure is d, satisfying: d / 10≤t1≤d / 2.

[0039] For example, t1 can be d / 10, d / 8, d / 6, d / 4, or d / 2. Since the thickness of the first solder layer meets the above range, it ensures that the solder layer is sufficient to fix the two workpieces to be soldered, while also ensuring that the thickness of the composite brazing film is not excessive. It is understood that the first solder layer can be a Sn solder layer.

[0040] According to one embodiment of this application, before depositing the first solder layer on the substrate, the substrate is ground and polished to a mirror finish. The polished substrate is then ultrasonically cleaned in deionized water and alcohol for 3-5 minutes, followed by drying. This allows the first solder layer to be deposited on the substrate more easily and ensures the uniformity of the first solder layer thickness.

[0041] In one embodiment of this application, grinding and polishing the substrate to a mirror finish includes: grinding the substrate layer by layer using 200-grit sandpaper, 400-grit sandpaper, 600-grit sandpaper, 800-grit sandpaper, and 1000-grit sandpaper until the surface of the base material is smooth and flat, and then polishing it to a mirror finish using a polishing machine. This makes the side of the substrate used for depositing the first solder layer smoother, further improving the uniformity of the thickness of the first solder layer deposited on the substrate.

[0042] In some embodiments of this application, the first transition layer includes at least one of AgCuIn transition layer, AgCu transition layer, Au transition layer, Ag transition layer and nickel-gold transition layer, the thickness of the first transition layer is t2, which satisfies: 100nm≤t2≤1μm; and / or, the second transition layer is AgCuIn transition layer, the thickness of the second transition layer is t3, which satisfies: 100nm≤t3≤1μm.

[0043] For example, t2 can be 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, or 1μm; and / or, t3 can be 100nm, 200nm, 300nm, 500nm, 700nm, 900nm, or 1μm.

[0044] This ensures the connection stability between the first solder layer and the nano-multilayer film structure while preventing the composite brazing film from becoming too thick; and / or, it ensures the connection stability between the second solder layer and the nano-multilayer film structure while preventing the composite brazing film from becoming too thick.

[0045] In some embodiments of this application, the first solder layer and the second solder layer comprise at least one of low-melting-point Sn-based solder, Al-based solder, Zn-based solder, and Ag-based solder. This improves the connection stability of the two workpieces to be soldered and the soldering quality between them.

[0046] It should be noted that the entire deposition process, including the deposition of the first solder layer, the first transition layer, the nanomultilayer film structure, the second transition layer, and the second solder layer, is carried out in a single process within an electron beam physical vapor deposition apparatus. In other words, the entire deposition process is performed in a vacuum environment with a vacuum level of 1 x 10⁻⁶. -3Pa-5x10 -2 Pa, which can effectively avoid the problem of interface oxidation in each deposition layer, and effectively alleviate problems such as voids, incomplete welds, excessive weld width and unevenness of the workpiece to be welded after welding.

[0047] This application also protects an assisted high-temperature brazing method using a composite brazing film, wherein the composite brazing film is prepared by the self-propagating reaction brazing film preparation method described in the above embodiments, and the assisted high-temperature brazing method includes at least the following steps: The composite brazing film is peeled off from the substrate and placed between the two workpieces to be welded; The composite brazing film is activated for welding to fix the two workpieces to be welded.

[0048] In some embodiments of this application, the assisted high-temperature brazing method further includes: The workpiece to be welded undergoes surface pretreatment. Place the workpiece to be welded in deionized water and alcohol in sequence for ultrasonic cleaning for 3-5 minutes, and then dry it. The obtained workpiece to be welded is combined with the composite brazing film and a certain pressure is applied and held; After preheating the combination of the workpiece to be welded and the composite brazing film, the composite brazing film is activated by a specific excitation method for welding.

[0049] This makes it easier for the two workpieces to be welded to be joined together, reducing the impact of impurities on the welding quality.

[0050] In some embodiments of this application, the pressure applied to the combination of the workpiece to be welded and the composite brazing film is 1MPa-10MPa, and the preheating temperature for the combination of the workpiece to be welded and the composite brazing film is 50℃-200℃.

[0051] For example, the pressure applied to the combination of the workpiece to be welded and the composite brazing film can be 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, or 10 MPa; the preheating temperature for the combination of the workpiece to be welded and the composite brazing film can be 50°C, 70°C, 90°C, 110°C, 130°C, 150°C, 170°C, 190°C, or 200°C.

[0052] This further improves the connection stability of the two workpieces after welding, and ensures the welding quality after the two workpieces are welded.

[0053] The embodiments of this application are described in detail below.

[0054] Example 1: 1) Sand the Cu substrate layer by layer with #200 sandpaper, #400 sandpaper, #600 sandpaper, #800 sandpaper and #1000 sandpaper until the surface of the base material is smooth and flat, and then polish it to a mirror finish with a polishing machine; 2) Place the polished Cu substrate in deionized water and alcohol in sequence for ultrasonic cleaning for 5 minutes, and then dry it with compressed air. 3) A Sn solder layer of approximately 10 μm was deposited on the substrate using plasma-assisted electron beam physical vapor deposition. 4) A 500 nm AgCuIn transition layer was deposited on the substrate using plasma-assisted electron beam physical vapor deposition. 5) On the substrate, Ni and Al nanolayered films were deposited alternately using plasma-assisted electron beam physical vapor deposition, with 800 alternating deposition cycles and a total thickness of approximately 40 μm. 6) Repeat step 4 7) Repeat step 3 8) The auxiliary ion for plasma-assisted electron beam physical vapor deposition is argon ions, the argon flow rate is 100 sccm, and the deposition gas pressure is 0.2 Pa; 9) Peel the composite brazing film obtained in steps 3-7 from the Cu substrate; 10) Clean the surface of the workpiece to be welded with 0.1 mol / L dilute hydrochloric acid to remove the oxide film; 11) Place the workpiece to be welded in deionized water and alcohol in sequence for ultrasonic cleaning for 5 minutes, and then dry it with compressed air. 12) Combine the workpiece to be welded obtained in step 11 with the composite brazing film obtained in step 9; 13) Apply a pressure of 3 MPa to the top surface of the system obtained in step 11 and maintain it; 14) Preheat the system obtained in step 12 at 100℃ for 5 minutes; 15) The brazing nanofilm was activated by electrical excitation and welded using a voltage of 7V and 1.5A. The advantages of this embodiment are: 1. The presence of the transition layer can improve the interface compatibility between the brazing filler layer and the intermediate layer of the nano-multilayer film, thereby enhancing the joint strength; 2. The self-propagating reaction of the multilayer film can provide a heat source for the welding process, reduce the heat-affected zone during the welding process, and reduce thermal stress; 3. Compared with existing brazing technologies, using NiAl multilayer film as an auxiliary heat source can improve the uneven heating of local heat sources, making it form a more uniform interface reaction, which is beneficial for large-area welding; 4. The brazing filler is heated evenly and completely melts and wets the base material, filling the gaps in the intermediate layer, which can improve the density of the welded joint.

[0055] Example 2: The difference between this embodiment and Example 1 is that step 5 involves plasma-assisted electron beam physical vapor deposition of Ni and Al nanolayers. Deposition process parameters: 1000 deposition cycles, resulting in a multilayer film thickness of approximately 50 μm. Everything else is the same as in Example 1.

[0056] Example 3: This embodiment differs from Examples 1 and 2 in that step 5 employs plasma-assisted electron beam physical vapor deposition to form a Ni and Al nanolayered film. The deposition process parameters are: 1200 deposition cycles, resulting in a multilayer film thickness of approximately 60 μm. Everything else is the same as in Example 1.

[0057] Example 4: The difference between this embodiment and Example 1 is that step 5 involves plasma-assisted electron beam physical vapor deposition to form a Ti and Al nanolayered film. Everything else is the same as in Example 1.

[0058] Example 5: The difference between this embodiment and Example 1 is that the transition layer deposited by plasma-assisted electron beam physical vapor deposition in step 4 is an AgCuInTi transition layer. Everything else is the same as in Example 1.

[0059] Example 6: The difference between this embodiment and Example 1 is that the AgSnCu solder layer described in step 3 is deposited using plasma-assisted electron beam physical vapor deposition. Everything else is the same as in Example 1.

[0060] The purpose of this invention is to provide a simple and efficient brazing method for preparing thin films and forming high-strength bonding interfaces that can be used as an auxiliary brazing agent. This invention uses a nano-multilayer film structure as the intermediate layer to prepare a composite brazing film composed of a solder layer, a transition layer, and an intermediate layer. Utilizing its self-propagating reaction and as an auxiliary heating source, it enables high-temperature brazing of dissimilar materials. This facilitates the complete melting of the solder layer and wetting of the base material surface, improving bonding efficiency and forming a high-strength, low-porosity bonding interface.

[0061] The self-propagating reactive brazing thin film and its preparation method proposed in this invention provide a high-melting-point, high-reliability, and low-cost solder for functional device applications, and are a competitive solution for high-temperature and power electronic interconnects.

[0062] Compared with existing technologies, it has the following significant advantages: (1) The thickness of the nano-multilayer film structure of the intermediate layer of the present invention is relatively thin, usually between a few micrometers and tens of micrometers. Its extremely fast cooling rate can ensure that the original shape of the connected materials is not destroyed.

[0063] (2) The nano-multilayer film structure of the intermediate layer of the present invention requires less ignition energy for the self-propagation process, saves energy and has high connection efficiency, and can effectively reduce the thermal stress generated during the welding process.

[0064] (3) The weld is smooth and the porosity of the device is extremely low, making it suitable for large-area and large-size welding.

[0065] (4) As a welding consumable that can be prepared at high speed, it has a considerable production capacity.

[0066] The specific composition of the solder layer in this invention includes, but is not limited to, low-melting-point Sn-based solder, Al-based solder, Zn-based solder, Ag-based solder, etc. The specific composition of the transition layer (first transition layer and second transition layer) in this invention includes, but is not limited to, tin-based, gold-based, silver-based, indium-based, aluminum-based or copper-based alloys; of course, it can also be a material with good wettability, such as Au, Ag, AuCu, AgCuIn, etc.

[0067] The composition of the nano-multilayer film structure in this invention includes, but is not limited to, metal-metal composition (Ni / Al, Ti / Al, Ni / Ti), metal / non-metal composition (Ni / Si, Al / CuO), etc. It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0068] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0069] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

[0070] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for preparing a self-propagating reactive brazing thin film, characterized in that, It should include at least the following steps: Deposit the first solder layer on the substrate; A first transition layer is deposited on the first solder layer; A nano-multilayer film structure is alternately deposited on the first transition layer; A second transition layer is deposited on the side of the nanomultilayer film structure away from the first solder layer; A second solder layer is deposited on the side of the second transition layer away from the first solder layer to form a composite brazing film.

2. The method for preparing a self-propagating reactive brazing thin film according to claim 1, characterized in that, The deposition of the first solder layer on the substrate includes: The first solder layer is deposited on the substrate using electron beam physical vapor deposition. The thickness of the first solder layer is t1, and the thickness of the nano-multilayer film structure is d, satisfying: d / 10≤t1≤d / 2.

3. The method for preparing a self-propagating reactive brazing thin film according to claim 1, characterized in that, Before depositing the first solder layer on the substrate, the substrate is ground and polished to a mirror finish. The polished substrate is then ultrasonically cleaned in deionized water and alcohol for 3-5 minutes, and then dried.

4. The method for preparing a self-propagating reactive brazing thin film according to claim 3, characterized in that, The step of grinding and polishing the substrate to a mirror finish includes: The substrate was sanded layer by layer with 200-grit sandpaper, 400-grit sandpaper, 600-grit sandpaper, 800-grit sandpaper and 1000-grit sandpaper until the surface of the base material was smooth and flat, and then polished to a mirror finish with a polishing machine.

5. The method for preparing a self-propagating reactive brazing thin film according to claim 1, characterized in that, The first transition layer includes at least one of AgCuIn transition layer, AgCu transition layer, Au transition layer, Ag transition layer, and nickel-gold transition layer, and the thickness of the first transition layer is t2, satisfying: 100nm≤t2≤1μm; and / or The second transition layer is an AgCuIn transition layer, and the thickness of the second transition layer is t3, which satisfies: 100nm≤t3≤1μm.

6. The method for preparing a self-propagating reactive brazing thin film according to claim 1, characterized in that, The first solder layer and the second solder layer are composed of at least one of low-melting-point Sn-based solder, Al-based solder, Zn-based solder, and Ag-based solder.

7. A high-temperature brazing method using composite brazing films, characterized in that, The composite brazing film is prepared by the self-propagating reaction brazing film preparation method according to any one of claims 1-6, wherein the assisted high-temperature brazing method includes at least the following steps: The composite brazing film is peeled off from the substrate and placed between the two workpieces to be welded; The composite brazing film is activated for welding to fix the two workpieces to be welded.

8. The auxiliary high-temperature brazing method according to claim 7, characterized in that, Also includes: The workpiece to be welded undergoes surface pretreatment. Place the workpiece to be welded in deionized water and alcohol in sequence for ultrasonic cleaning for 3-5 minutes, and then dry it. The obtained workpiece to be welded is combined with the composite brazing film and a certain pressure is applied and held; After preheating the combination of the workpiece to be welded and the composite brazing film, the composite brazing film is activated by a specific excitation method for welding.

9. The auxiliary high-temperature brazing method according to claim 8, characterized in that, The pressure applied to the combination of the workpiece to be welded and the composite brazing film is 1MPa-10MPa, and the preheating temperature of the combination of the workpiece to be welded and the composite brazing film is 50℃-200℃.

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