Flexible smart brazing foil and method of making same

Abstract

The present application relates to the technical field of welding material manufacturing, and discloses a flexible intelligent brazing film and a preparation method thereof, the flexible intelligent brazing film comprising: an intermediate layer, a roll-formed brazing filler metal film and a filler layer respectively located on two sides of the intermediate layer, wherein the intermediate layer is a self-propagating multilayer film; and the preparation method comprises the following steps: (1) depositing the self-propagating multilayer film on the surface of one side of the roll-formed brazing filler metal film under vacuum conditions; and (2) depositing or bonding the filler layer on the outer surface of the self-propagating multilayer film prepared in step (1). The flexible intelligent brazing film has a small bending radius, and thus has high flexibility and can be used for welding curved surface parts.

Description

Technical Field

[0001] This invention belongs to the field of welding material manufacturing technology, specifically relating to a flexible intelligent brazing film and its preparation method. Background Technology

[0002] Intelligent brazing film is a thin-film brazing material. It incorporates a self-heating component, and under 9V AC (DC9V) power, the solder undergoes an exothermic reaction, melting and heating the welding surface to form wetting, capillary action, and welding. Through high-temperature self-propagating technology, the entire brazing process is completed over a large area within milliseconds. Using brazing film eliminates the need for expensive equipment and complex processes, allowing brazing to be performed in any environment and temperature. Welding strength can reach over 60MPa, meeting the brazing requirements of various materials such as metals, non-metals, semiconductors, crystals, piezoelectric ceramics, glass, and polymer layers. Currently available brazing film products, both domestically and internationally, suffer from poor flexibility and cannot weld curved parts. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of poor flexibility in brazing film products manufactured by existing technologies, and to provide a flexible intelligent brazing film and its preparation method.

[0004] To achieve the above objectives, the first aspect of the present invention provides a flexible smart brazing film, which includes: an intermediate layer and a rolled brazing solder film and a solder layer respectively located on both sides of the intermediate layer, wherein the intermediate layer is a self-propagating multilayer film.

[0005] A second aspect of the present invention provides a method for preparing a flexible smart brazing film, the method comprising the following steps: (1) Deposit a self-propagating multilayer film on the surface of a rolled-out brazing solder film under vacuum conditions; (2) Deposit or bond a solder layer on the outer surface of the self-propagating multilayer film prepared in step (1).

[0006] Through the above technical solution, the present invention achieves the following beneficial effects: (1) The flexible intelligent brazing film of the present invention has a small bending radius, and therefore the flexible intelligent brazing film of the present invention has high flexibility and can be used to weld curved parts.

[0007] (2) Compared with the prior art of directly peeling self-propagating multilayer films from the substrate, the preparation method of the present invention greatly improves the yield of flexible smart brazing films, reduces losses, improves production efficiency, and reduces labor intensity. Attached Figure Description

[0008] Figure 1This is a schematic diagram of the cross-sectional structure of the flexible intelligent brazing film of the present invention.

[0009] Explanation of reference numerals in the attached figures 1. Rolled brazing solder film 2. Solder layer 3. Self-propagating multilayer films 4. Single-layer films in self-propagating multilayer films Detailed Implementation The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0010] The first aspect of this invention provides a flexible smart brazing film (such as...) Figure 1 As shown, the flexible smart brazing film includes: an intermediate layer and a rolled brazing solder film and a solder layer located on both sides of the intermediate layer, wherein the intermediate layer is a self-propagating multilayer film.

[0011] According to the present invention, preferably, the bending radius of the flexible smart brazing film is less than 50 mm, more preferably 0.1-20 mm, and even more preferably 5-10 mm.

[0012] The bending radius test method is as follows: A two-point bending method is used to induce bending deformation at both ends of the flexible smart brazed film. The critical radius of curvature at the moment of failure is measured, and this critical radius of curvature characterizes the flexibility of the flexible smart brazed film. Specifically, the critical radius of curvature refers to the minimum radius of curvature corresponding to the complete bending trajectory of the flexible smart brazed film under two-point bending deformation until failure. A smaller bending radius indicates better flexibility of the flexible smart brazed film.

[0013] According to the present invention, preferably, the thickness ratio of the rolled brazing solder film, the self-propagating multilayer film and the solder layer is 1:1.5-5:0.5-2.

[0014] According to the present invention, preferably, the tensile strength of the rolled brazing solder film is 10-30 MPa. Using a brazing solder film that meets the above tensile strength can further improve the flexibility of the flexible smart brazing film.

[0015] According to the present invention, preferably, the elongation (after fracture) of the rolled brazing solder film is 30-60%. Using a brazing solder film that meets the above elongation can further improve the flexibility of the flexible smart brazing film.

[0016] According to the present invention, preferably, the shrinkage rate of the rolled brazing solder film is 70-95%. Using a brazing solder film that meets the above shrinkage rate can further improve the flexibility of the flexible smart brazing film.

[0017] According to the present invention, preferably, the cloth hardness of the rolled brazing solder film is HB4-HB7. Using a brazing solder film that meets the above-mentioned cloth hardness can further improve the flexibility of the flexible smart brazing film.

[0018] The test methods for tensile strength and elongation are as follows: tensile properties are tested using a universal tensile-compression testing machine according to the national standard GB / T 228.1—2010. Shrinkage rate is tested using the suspension method. Brinell hardness is tested using a Brinell hardness tester according to GB / T 231.1—2009.

[0019] More preferably, using a brazing solder film that simultaneously satisfies the above-mentioned tensile strength, elongation, shrinkage, and cloth hardness can further improve the flexibility of the flexible smart brazing film.

[0020] In this invention, there are no special limitations on the rolling conditions of the brazing solder film, as long as the tensile strength, elongation, shrinkage and cloth hardness of the brazing solder film meet the above requirements.

[0021] According to the present invention, preferably, the material of the rolled solder film includes at least one metal from Group IB and / or IVA (e.g., Sn, Pb, Cu, Ag, Au, etc.), more preferably at least one of Sn, Ag, and Au. The solder film may also contain doping elements (e.g., Pb, Al, etc.). The type and content of the doping elements are not particularly limited, as long as the tensile strength, elongation, shrinkage, and Brinell hardness of the solder film meet the above requirements. For example, the solder film can also be tin foil, with a tin content of 50-70 wt% and the balance being lead.

[0022] According to the present invention, preferably, the thickness of the rolled brazing solder film is 15-40 μm. Limiting the thickness of the brazing solder film to the above range can further improve the flexibility of the flexible smart brazing film and enhance the welding performance of curved surfaces.

[0023] According to the present invention, preferably, the thickness of the self-propagating multilayer film is 40-970 μm, more preferably 50-100 μm.

[0024] According to the present invention, preferably, the thickness of a single layer of the self-propagating multilayer film is 1-30 nm. More preferably, the thickness ratio of two adjacent single layers in the self-propagating multilayer film is 1:1-3.

[0025] According to the present invention, preferably, the materials of adjacent layers in the self-propagating multilayer film are different; preferably, the single-layer material of the self-propagating multilayer film includes at least one of Group VIII, IIIA, IVB, and IB (e.g., Pb, Pt, Co, Fe, B, Al, Ga, In, Ti, Zr, Hf, Cu, Ag, Au, etc.), more preferably at least one of Ni, Al, Cu, and Ti. The materials of adjacent layers in the self-propagating multilayer film can also be Ni-Pb, Ni-Pt, Ni-Co, Ni-Fe, Ni-B, Ni-Ga, Ni-Ti, etc. More preferably, the materials of adjacent layers in the self-propagating multilayer film are Ni-Al and Ni-Ti.

[0026] According to the present invention, preferably, the material of the solder layer includes at least one element from Group IB and / or IVA (e.g., Sn, Pb, Cu, Ag, Au, etc.), and more preferably at least one of Sn, Ag and Au.

[0027] According to the present invention, preferably, the thickness of the solder layer is 10-30 μm.

[0028] A second aspect of the present invention provides a method for preparing a flexible smart brazing film, the method comprising the following steps: (1) Deposit a self-propagating multilayer film on the surface of a rolled-out brazing solder film under vacuum conditions; (2) Deposit or bond a solder layer on the outer surface of the self-propagating multilayer film prepared in step (1).

[0029] In this invention, it is understood that after depositing a self-propagating multilayer film on one side of the rolled-up brazing solder film, a solder layer is deposited or bonded on the other side of the self-propagating multilayer film; that is, one surface of the self-propagating multilayer film is connected to the rolled-up brazing solder film by deposition, and the other surface is connected to the solder layer by deposition or bonding.

[0030] According to the present invention, preferably, in step (1), the vacuum degree of the vacuum condition is 10⁻³ Pa, more preferably 10⁻⁶ Pa. In the present invention, the vacuum degree refers to the reading of a vacuum gauge. The vacuum condition refers to the environment in which the rolled-out brazing solder film is located.

[0031] According to the present invention, taking into account both the flexibility and welding performance of the flexible intelligent brazing film, preferably, the thickness ratio of the rolled brazing solder film, the self-propagating multilayer film, and the solder layer is 1:1.5-5:0.5-2 (e.g., 1:1.5:0.5, 1:2:0.5, 1:3:0.5, 1:1.5:1, 1:1.5:1.5, 1:1.5:2, 1:2:0.5, 1:3:1, 1:2:1, and any two of the above ranges). In the present invention, the self-propagating multilayer film is composed of alternating layers of metal layers of different materials, or alternating layers of metal layers and non-metal layers. The self-propagating multilayer film can undergo a self-propagating exothermic reaction after excitation, and the reaction product is in the liquid phase. Unless otherwise specified, the thickness of the self-propagating multilayer film refers to the total thickness of the self-propagating multilayer film, while the thickness of a single layer of the self-propagating multilayer film refers to the thickness of a single metal layer or a single non-metal layer.

[0032] According to the present invention, preferably, the tensile strength of the rolled brazing solder film is 10-30 MPa (e.g., 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, and any two of the above). Using a brazing solder film that meets the above tensile strength can further improve the flexibility of the flexible smart brazing film.

[0033] According to the present invention, preferably, the elongation (after fracture) of the rolled brazing solder film is 30-60% (30%, 35%, 40%, 45%, 50%, 60%, and any two of the above). Using a brazing solder film that meets the above elongation can further improve the flexibility of the flexible smart brazing film.

[0034] According to the present invention, preferably, the shrinkage rate of the rolled brazing solder film is 70-95% (70%, 80%, 85%, 90%, 95%, and any two of the above). Using a brazing solder film that meets the above shrinkage rate can further improve the flexibility of the flexible smart brazing film.

[0035] According to the present invention, preferably, the cloth hardness of the rolled brazing solder film is HB4-HB7 (HB4, HB5, HB6, HB7, and any two of the above). Using a brazing solder film that meets the above cloth hardness can further improve the flexibility of the flexible smart brazing film.

[0036] The test methods for tensile strength and elongation are as follows: tensile properties are tested using a universal tensile-compression testing machine according to the national standard GB / T 228.1—2010. Shrinkage rate is tested using the suspension method. Brinell hardness is tested using a Brinell hardness tester according to GB / T 231.1—2009.

[0037] More preferably, using a brazing solder film that simultaneously satisfies the above-mentioned tensile strength, elongation, shrinkage, and cloth hardness can further improve the flexibility of the flexible smart brazing film.

[0038] In this invention, there are no special limitations on the rolling conditions of the brazing solder film, as long as the tensile strength, elongation, shrinkage and cloth hardness of the brazing solder film meet the above requirements.

[0039] According to the present invention, the material of the brazing solder film can be a commonly used solder material in the art. Preferably, the material of the rolled brazing solder film includes at least one element from Group IB and / or IVA (e.g., Sn, Pb, Cu, Ag, Au, etc.), and more preferably includes at least one of Sn, Ag, and Au. Typically, to reduce costs, doping elements (e.g., Pb, Al, etc.) are added to the brazing solder film. There are no particular limitations on the type and amount of doping elements, as long as the tensile strength, elongation, shrinkage, and Brinell hardness of the brazing solder film meet the above requirements. For example, the brazing solder film can also be tin foil, with a tin content of 50-70 wt% and the balance being lead.

[0040] According to the present invention, in order to improve the flexibility of the flexible smart brazing film and improve the welding performance of curved surfaces, preferably, the thickness of the rolled brazing solder film is 15-40μm (15μm, 20μm, 25μm, 30μm, 35μm, 40μm, and any two of the above).

[0041] In this invention, the method for preparing the self-propagating multilayer film can be a method commonly used in the art. Preferably, in step (1), the deposition method includes physical deposition and / or chemical vapor deposition, more preferably including magnetron sputtering and / or vacuum electroplating; more preferably, the deposition method is vacuum magnetron sputtering. Those skilled in the art can adjust the deposition conditions according to the required thickness of the single layer of the self-propagating multilayer film.

[0042] According to the present invention, preferably, the conditions for vacuum magnetron sputtering include: a sputtering argon pressure of 1-2 Pa. Wherein, the sputtering argon pressure refers to the protective gas pressure of the target material.

[0043] According to the present invention, preferably, the thickness of the self-propagating multilayer film is 40-970 μm (40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 970 μm, and any two of the above), preferably 50-100 μm.

[0044] According to the present invention, preferably, the thickness of a single layer of the self-propagating multilayer film is 1-30 nm (1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, and any two of the above ranges). More preferably, the thickness ratio of two adjacent single layers in the self-propagating multilayer film is 1:1-3 (1:1, 1:2, 1:3, and any two of the above ranges).

[0045] According to the present invention, preferably, the materials of adjacent layers in the self-propagating multilayer film are different; more preferably, the material of a single layer of the self-propagating multilayer film includes at least one element from Group VIII, IIIA, IVB, and IB (e.g., at least one element from Pb, Pt, Co, Fe, B, Al, Ga, In, Ti, Zr, Hf, Cu, Ag, Au, etc.), and even more preferably, at least one from Ni, Al, Cu, and Ti. The materials of adjacent layers in the self-propagating multilayer film can be Ni-Pb, Ni-Pt, Ni-Co, Ni-Fe, Ni-B, Ni-Ga, C-Ti, etc. More preferably, the materials of adjacent layers in the self-propagating multilayer film are Ni-Al, Ni-Ti, and Al-Cu.

[0046] According to the present invention, preferably, the material of the solder layer includes at least one element from Group IB and / or IVA (e.g., Sn, Pb, Cu, Ag, Au, etc.), and more preferably at least one of Sn, Ag and Au.

[0047] According to the present invention, preferably, the thickness of the solder layer is 10-30 μm (10 μm, 15 μm, 20 μm, 25 μm, 30 μm, and any two of the above).

[0048] According to the present invention, the bonding method is not particularly limited. Preferably, a conductive adhesive is used to bond the solder layer to the self-propagating multilayer film. The composition of the conductive adhesive is not particularly limited, as long as it can bond the solder layer to the self-propagating multilayer film. For example, Loctite 3888 conductive adhesive can be used. Loctite 3888 is a high-performance two-component conductive adhesive containing silver and is suitable for electrical applications. Loctite 3888 conductive adhesive cures at room temperature and consists of two components. When the two components are mixed, they form a viscous, dense paste that is amber in color. The two components are (1) Component A: a transparent liquid containing epoxy resin; (2) Component B: silver.

[0049] According to the present invention, in step (2), the deposition method includes physical deposition and / or chemical vapor deposition, preferably including magnetron sputtering and / or vacuum electroplating; more preferably vacuum electroplating. The deposition conditions are not particularly limited, as long as the thickness of the solder layer meets the requirements and the deposition process is not oxidized.

[0050] According to the present invention, in order to further improve the flexibility and curved surface welding performance of the flexible smart brazing film, preferably, the method further includes: rolling the product obtained in step (2) with a rolling method for roll leveling. More preferably, the rolling conditions include: a rolling temperature of 15-50℃ (15℃, 20℃, 30℃, 40℃, 50℃, and any two of the above), and a rolling pressure of 80-200MPa (80MPa, 90MPa, 100MPa, 120MPa, 140MPa, 160MPa, 180MPa, 200MPa, and any two of the above).

[0051] The present invention will be described in detail below through embodiments.

[0052] The tin foil film contains 63 wt% tin and the remainder is lead.

[0053] The conductive adhesive is manufactured by Yantai Zebang Chemical Co., Ltd., and its brand name is Henkel Loctite 3888 Silver-filled Conductive Adhesive.

[0054] Example 1 This embodiment illustrates the preparation of flexible smart brazing films. (1) The rolled-out solder film is fixed on the moving substrate of a vacuum magnetron sputtering coating machine. A vacuum of 8 Pa is drawn, and nickel and aluminum layers are alternately sputtered onto the surface of the solder film using magnetron sputtering (sputtering argon pressure of 1.5 Pa). After 1000 cycles of magnetron sputtering deposition, a self-propagating multilayer film is formed. The rolled-out solder film is tin foil with a tensile strength of 20 MPa, elongation of 40%, shrinkage of 90%, cloth hardness of HB5, and a thickness of 20 μm. The thickness of the self-propagating multilayer film is 60 μm; the single-layer thicknesses of the nickel layer and the aluminum layer are 10 nm and 30 nm, respectively.

[0055] (2) Remove the rolled brazing solder film with self-propagating multilayer film deposited on the surface obtained in step (1) from the moving substrate of the vacuum magnetron sputtering coating machine, and plate a 20μm thick tin layer on the surface of the self-propagating multilayer film by electroplating.

[0056] (3) The product obtained in step (2) is rolled and leveled by rolling. The conditions of rolling include: rolling temperature 30℃ and rolling pressure 100MPa.

[0057] Example 2 This embodiment illustrates the preparation of flexible smart brazing films. (1) The rolled solder film is fixed on the moving substrate of a vacuum magnetron sputtering coating machine, and then a vacuum of 10 Pa is drawn. Nickel and titanium layers are alternately sputtered on the surface of the solder film using magnetron sputtering (sputtering argon pressure of 1.2 Pa). After 1000 cycles of sputtering deposition, a self-propagating multilayer film is formed. The rolled solder film is tin foil with a tensile strength of 20 MPa, an elongation of 40%, a shrinkage rate of 90%, and a cloth hardness of HB5. The thickness of the solder film is 25 μm. The thickness of the self-propagating multilayer film is 50 μm. The single-layer thickness of the nickel layer is 10 nm, and the single-layer thickness of the titanium layer is 25 nm.

[0058] (2) Remove the rolled brazing solder film with self-propagating multilayer film deposited on the surface obtained in step (1) from the moving substrate of the vacuum magnetron sputtering coating machine, and use conductive adhesive to bond a 25μm thick silver film to the surface of the self-propagating multilayer film.

[0059] (3) The product obtained in step (2) is rolled and leveled by rolling. The conditions of rolling include: temperature of 40°C and rolling pressure of 150MPa.

[0060] Example 3 This embodiment illustrates the preparation of flexible smart brazing films. (1) The rolled-formed brazing solder film was fixed on the moving substrate of a vacuum magnetron sputtering coating machine. Then, a vacuum of 10 Pa was drawn, and copper and aluminum layers were alternately sputtered onto the surface of the brazing solder film using magnetron sputtering (sputtering argon pressure of 1.2 Pa). After 1000 cycles of sputtering deposition, a self-propagating multilayer film was formed. The rolled-formed brazing solder film had a tensile strength of 30 MPa, an elongation of 50%, a shrinkage rate of 80%, and a Brinell hardness of HB6. The brazing solder film was a 30 μm thick gold film. The thickness of the self-propagating multilayer film was 60 μm. The single-layer thickness of the copper layer was 10 nm, and the single-layer thickness of the aluminum layer was 25 nm.

[0061] (2) Remove the rolled brazing solder film with self-propagating multilayer film deposited on the surface obtained in step (1) from the moving substrate of the vacuum magnetron sputtering coating machine, and use conductive adhesive to bond a 25μm thick gold film to the surface of the self-propagating multilayer film.

[0062] (3) The product obtained in step (2) is rolled and leveled by rolling. The conditions of rolling include: temperature of 25°C and rolling pressure of 90MPa.

[0063] Example 4 The procedure is carried out according to the method of Example 1, except that step (3) is not included.

[0064] Comparative Example 1 The method of Example 2 was followed, except that a nickel layer and a titanium layer were alternately sputtered onto the active substrate to obtain a self-propagating multilayer film. Then, the self-propagating multilayer film was peeled off from the substrate, and a 25 μm thick tin foil and a silver film were respectively bonded to the two sides of the self-propagating multilayer film.

[0065] Test Example 1 (1) The bending radius, tensile strength and tensile shear strength of the flexible smart brazing films prepared in the above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0066] The bending radius test method is as follows: A two-point bending method is used to induce bending deformation at both ends of the flexible smart brazed film. The critical radius of curvature at the moment of failure is measured, and this critical radius of curvature characterizes the flexibility of the flexible smart brazed film. Specifically, the critical radius of curvature refers to the minimum radius of curvature corresponding to the complete bending trajectory of the flexible smart brazed film under two-point bending deformation until failure. A smaller bending radius indicates better flexibility of the flexible smart brazed film.

[0067] The test method for tensile strength is as follows: in accordance with the national standard GB / T 228.1—2010.

[0068] The test method for tensile shear strength is as follows: according to the national standard ASTM D1002-10.

[0069] (2) The flexible smart brazing films prepared in the above embodiments and comparative examples were tested to braze planar and curved parts (the parts are made of steel and the steel surface is plated with tin). The welding conditions included: welding temperature 20°C and welding pressure 0.5 MPa. Then the effective welding area of ​​the welded parts was tested.

[0070] Test method for effective welding area: The initial area to be welded on the curved surface part is denoted as S0. After welding, an external force is used to separate the flat and curved surface parts, and then the actual welded area on the curved surface part is measured (denoted as S1). Effective welding area = S0 ÷ S1 × 100%. The higher the effective welding area, the better the welding performance of the flexible intelligent brazing film.

[0071] Table 1

[0072] As shown in Table 1, compared with Comparative Example 1, the flexible smart brazing film prepared by the method of the present invention can reduce the bending radius and improve the flexibility of the flexible smart brazing film without reducing tensile strength, tensile shear strength, and effective welding area. Meanwhile, in the method of Comparative Example 1, the breakage rate of the self-propagating multilayer film when peeling it from the substrate is typically 30%, while the method of the present invention can eliminate the step of peeling the self-propagating multilayer film from the substrate, improving the yield of the self-propagating multilayer film and reducing the production cost of the flexible smart brazing film.

[0073] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A flexible intelligent brazing film, characterized in that, The flexible smart brazing film includes: an intermediate layer and a rolled brazing solder film and a solder layer located on both sides of the intermediate layer, wherein the intermediate layer is a self-propagating multilayer film; The rolled brazing solder film has a tensile strength of 10-30 MPa, an elongation of 30-60%, a shrinkage of 70-95%, and a cloth hardness of HB4-HB7. The bending radius of the flexible smart brazing film is less than 50mm; The material of the rolled brazing solder film includes at least one element from Group IB and / or IVA; The thickness of the rolled brazing solder film is 15-40 μm; The thickness of the self-propagating multilayer film is 40-970 μm; the thickness of a single layer of the self-propagating multilayer film is 10-30 nm. The materials of adjacent layers in the self-propagating multilayer film are different; the material of a single layer of the self-propagating multilayer film includes at least one element from Group VIII, IIIA, IVB, and IB. The solder layer is made of at least one element from Group IB and / or IVA. The thickness of the solder layer is 10-30 μm.

2. The flexible intelligent brazing film according to claim 1, wherein the thickness ratio of the rolled brazing solder film, the self-propagating multilayer film and the solder layer is 1:1.5-5:0.5-2.

3. The flexible intelligent brazing film according to claim 1, wherein, The single-layer material of the self-propagating multilayer film includes Al and Cu.

4. A method for preparing a flexible smart brazing film, characterized in that, The method includes the following steps: (1) Deposit a self-propagating multilayer film on the surface of a rolled-out brazing solder film under vacuum conditions; (2) Deposit or bond a solder layer on the outer surface of the self-propagating multilayer film prepared in step (1); The rolled brazing solder film has a tensile strength of 10-30 MPa, an elongation of 30-60%, a shrinkage of 70-95%, and a cloth hardness of HB4-HB7. The material of the rolled brazing solder film includes at least one element from Group IB and / or IVA; the thickness of the rolled brazing solder film is 15-40 μm. The thickness of the self-propagating multilayer film is 40-970 μm; the thickness of a single layer of the self-propagating multilayer film is 10-30 nm. The materials of adjacent layers in the self-propagating multilayer film are different; the material of a single layer of the self-propagating multilayer film includes at least one element from Group VIII, IIIA, IVB, and IB. The solder layer is made of at least one element from Group IB and / or IVA. The thickness of the solder layer is 10-30 μm.

5. The method according to claim 4, wherein, The thickness ratio of the rolled brazing solder film, self-propagating multilayer film and solder layer is 1:1.5-5:0.5-2.

6. The method according to claim 4, wherein, The single-layer material of the self-propagating multilayer film includes Al and Cu.

7. The method according to claim 4, wherein, The deposition methods described in steps (1) and (2) each independently include physical deposition and / or chemical vapor deposition.

8. The method according to claim 4, wherein, The method further includes: using a rolling method to roll-level the product obtained in step (2).

9. The application of the flexible smart brazing film according to any one of claims 1-3 or the flexible smart brazing film prepared by the method according to any one of claims 4-8 in reducing the bending radius.

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