Composite brazing film and preparation method and application thereof

Abstract

The invention relates to the technical field of welding, and discloses a composite brazing film and a preparation method and application thereof, and the method comprises the steps (1), (2-A) and (3); alternatively, the method comprises the steps (1), (2-B) and (3). The method comprises the following steps: (1) providing a solder net, wherein the solder net is a copper net of which the surface layer is electroplated with metal solder; or the preparation method of the solder mesh comprises the following steps: sequentially coating the adhesive and the tin powder on the surface of the copper mesh to obtain the solder mesh; (2-A) preparing a composite body: sequentially paving and stacking a solder net, tin powder, self-propagating powder, a solder net and tin powder to obtain the composite body; (2-B) preparing a composite body: dividing the self-propagating powder into two parts, and then sequentially tiling and stacking the first part of self-propagating powder, the solder net, the tin powder and the second part of self-propagating powder to obtain the composite body; (3) pre-pressing and rolling the composite body in sequence; wherein the rolling temperature is 80-180 DEG C. The composite brazing film prepared through the method is small in bending radius and high in production efficiency.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to a composite brazing film, its preparation method, and its application. Background Technology

[0002] The existing intelligent brazing film is a multilayer thin-film brazing material used for brazing. It not only releases energy to complete brazing under different environmental conditions, but also possesses the following characteristics: 1) The thickness of each layer of the multilayer thin-film material is 2-2500 nm, with 1000-7000 layers and a total thickness not exceeding 600 μm; 2) Parameters of each layer: width greater than 0.5 cm, length greater than 1 cm; 3) Energy release parameters: the initial temperature of the reaction energy release process is 400℃, the maximum energy release is 1100-4000 J / g (depending on composition), and the power of local reaction energy release is not less than 106 J / g*s; 4) The linear velocity of the combustion wave propagation is 0.05-14.0 m / s; 5) The operating temperature range does not exceed 3100 K. Because it incorporates self-heating components into the welding material, an electrochemical reaction occurs under DC 9V, generating heat to melt the solder, heat the welding surface, and form wetting, capillary action, and welding. Through high-temperature self-propagating technology, the entire brazing process is completed over a large area within milliseconds. The intelligent brazing film does not require expensive equipment or complex processes, and its welding strength can reach over 60MPa, meeting the brazing needs between various materials such as metals, non-metals, semiconductors, crystals, piezoelectric ceramics, glass, and polymer layers.

[0003] The aforementioned multilayer materials include metal-metal multilayer materials and metal-nonmetal multilayer materials. One existing preparation method involves layer-by-layer magnetron sputtering of target material (negative electrode) onto the surface of a cooled substrate using vacuum deposition. For example, the preparation method disclosed in CN1817539A involves magnetron sputtering of cathode material onto the substrate surface, followed by layer-by-layer vacuum ion deposition of relevant components onto the substrate. However, due to the low production efficiency of these methods and the high cost of the equipment and accessories used in the preparation process, the manufacturing cost is high, limiting the application range of the products and hindering their widespread expansion. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low production efficiency, high cost, and unsuitability for curved surface welding of existing composite brazing films. This invention provides a composite brazing film, its preparation method, and its application. This method has the advantages of high production efficiency, low manufacturing cost, and wide application range.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a composite brazing film, the method comprising steps (1), (2-A) and (3); or, the method comprising steps (1), (2-B) and (3);

[0006] (1) Provide solder mesh: The solder mesh is a copper mesh with a surface electroplated with metal solder;

[0007] Alternatively, the solder mesh can be prepared by coating the surface of a copper mesh with an adhesive and then with solder powder in sequence.

[0008] (2-A) Preparation of composite: Solder mesh, tin powder, self-propagating powder, solder mesh, and tin powder are sequentially laid out and stacked to obtain a composite;

[0009] (2-B) Preparation of composite: Divide the self-propagating powder into two parts, and then lay the first part of self-propagating powder, solder mesh, tin powder and the second part of self-propagating powder in sequence to obtain the composite;

[0010] (3) The composite is pre-pressed and rolled in sequence; wherein the rolling temperature is 80-180℃.

[0011] A second aspect of the present invention provides a composite brazing film prepared by the method described above.

[0012] A third aspect of the present invention provides a composite brazing film comprising a self-propagating layer and solder layers formed by pre-pressing and rolling solder mesh and tin powder on both sides of the self-propagating layer;

[0013] Alternatively, the composite solder film may include a solder layer formed by pre-pressing and rolling solder mesh and tin powder, and self-propagating layers located on both sides of the solder layer.

[0014] The fourth aspect of the present invention provides the application of the composite brazing film described above in welding planar and / or curved surface weldments.

[0015] Through the above technical solution, the present invention achieves the following beneficial effects:

[0016] (1) The method of the present invention can improve production efficiency and reduce manufacturing cost.

[0017] (2) The method of the present invention has high production efficiency in preparing composite brazing films. The film products have the characteristics of small bending radius, not easy to break, low welding difficulty, high tensile and shear strength and high brazing rate. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of composite pre-pressing (forging). Figure 1 The mold is not shown in the image.

[0019] Figure 2 This is a schematic diagram of the composite rolling process.

[0020] Explanation of reference numerals in the attached figures

[0021] 1. Copper mesh; 2. Adhesive; 3. Tin powder; 4. Self-propagating powder. Detailed Implementation

[0022] 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.

[0023] The first aspect of the present invention provides a method for preparing a composite brazing film, the method comprising steps (1), (2-A) and (3); or, the method comprising steps (1), (2-B) and (3);

[0024] (1) Provide solder mesh: The solder mesh is a copper mesh with a surface electroplated with metal solder;

[0025] Alternatively, the solder mesh can be prepared by coating the surface of a copper mesh with an adhesive and then with solder powder in sequence.

[0026] (2-A) Preparation of composite: Solder mesh, tin powder, self-propagating powder, and solder mesh tin powder are sequentially laid out and stacked to obtain composite;

[0027] (2-B) Preparation of composite: Divide the self-propagating powder into two parts, and then lay the first part of self-propagating powder, solder mesh, tin powder and the second part of self-propagating powder in sequence to obtain the composite;

[0028] (3) The composite is pre-pressed and rolled in sequence; the rolling temperature is 80-180℃.

[0029] In this invention, adhesive and tin powder can be coated on one or both surfaces of the copper mesh.

[0030] In this invention, when the amount of tin powder is small, it is necessary to ensure that the tin powder can fill the mesh of the copper mesh; when the amount of tin powder is large, in addition to ensuring that the tin powder can fill the mesh of the copper mesh, a thin layer of tin powder can also be formed on the surface of the copper mesh.

[0031] According to the present invention, in order to reduce the bending radius, make the composite brazing film suitable for curved surface welding, avoid the composite brazing film from breaking when welding curved surfaces, thereby increasing the difficulty of welding; and improve tensile shear strength and brazing rate, preferably, the pre-pressing pressure makes the density of the self-propagating powder layer obtained after pre-pressing 55-65% of the theoretical density of the self-propagating powder.

[0032] In this invention, the theoretical density of the self-propagating powder (denoted as ρ0) is calculated as follows: a certain mass (denoted as m) of self-propagating powder is weighed and placed into a container marked with a volume. The volume of the self-propagating powder (denoted as V0) is read, and the theoretical density of the self-propagating powder is calculated according to ρ0 = m / V0.

[0033] In this invention, the density (denoted as ρ1) of the self-propagating powder layer obtained after pre-compression is calculated as follows: the length, width and thickness of the self-propagating powder layer obtained after pre-compression are measured, the volume (denoted as V1) of the self-propagating powder layer obtained after pre-compression is calculated, and the density of the self-propagating powder layer obtained after pre-compression is calculated according to ρ1=m / V1.

[0034] In this invention, the pre-pressing temperature is not particularly limited; for example, the pre-pressing temperature is 15-40°C. Pre-pressing is usually performed at room temperature. The equipment used for pre-pressing can be any equipment commonly used in the art capable of applying pressure, such as a hydraulic press, a pneumatic press, a spring press, etc. Preferably, the equipment used for pre-pressing is a hydraulic press; more preferably, the pre-pressing method is longitudinal compression with a hydraulic press and / or forging. In this invention, it is understood that "longitudinal compression with a hydraulic press" refers to the press head pressing the powder downwards along the longitudinal direction to make it dense.

[0035] According to the present invention, in order to reduce the bending radius, make the composite brazing film suitable for curved surface welding, avoid the composite brazing film from breaking when welding curved surfaces, thereby increasing the difficulty of welding; and improve tensile shear strength and brazing rate, preferably, the rolling pressure makes the density of the self-propagating powder layer obtained after rolling 75-85% of the theoretical density of the self-propagating powder.

[0036] In this invention, the density (denoted as ρ2) of the self-propagating powder layer obtained after rolling is calculated as follows: the length, width and thickness of the self-propagating powder layer obtained after rolling are measured, the volume (denoted as V2) of the self-propagating powder layer obtained after rolling is calculated, and the density of the self-propagating powder layer obtained after rolling is calculated according to ρ2=m / V2.

[0037] According to the present invention, in order to further reduce the bending radius and improve the brazing rate, preferably, (ρ2-ρ1)÷ρ0×100%=10-30%, that is, the difference between the density of the self-propagating powder layer obtained after rolling and the density of the self-propagating powder layer obtained after pre-pressing accounts for 10-30% of the theoretical density of the self-propagating powder.

[0038] According to the present invention, preferably, the rolling method is cold rolling with oil lubrication. Herein, cold rolling refers to rolling at a recrystallization temperature (e.g., 80-180°C).

[0039] According to the present invention, preferably, the metal solder includes at least one of tin, gold and silver.

[0040] According to the present invention, preferably, the copper mesh with the surface plated with metal solder is at least one of tin-plated copper mesh, gold-plated copper mesh, and silver-plated copper mesh.

[0041] According to the present invention, preferably, the size of the aperture of the copper mesh is 100-200 mesh.

[0042] In this invention, the size of the copper mesh is not particularly limited, but preferably, the wire diameter is 0.001-0.2 mm, more preferably 0.01-0.02 mm, the mesh thickness is 0.001-0.2 mm, more preferably 0.01-0.02 mm, the length is 100-500 mm, and the width is 50-110 mm. After pre-pressing and rolling, the thickness of the copper mesh usually decreases; therefore, sometimes the thickness of the solder layer is less than the thickness of the copper mesh.

[0043] According to the present invention, the type of adhesive is not particularly limited and can be any adhesive commonly used in the art. Preferably, the adhesive includes polyvinyl butyral and / or soldering adhesive. The amount of adhesive used can be a conventional amount used in the art, as long as it is sufficient to allow the solder powder to adhere to the copper mesh.

[0044] According to the present invention, preferably, the amount of tin powder is such that the thickness of the solder layer in the composite brazing film is 7-20 μm; wherein the solder layer is obtained by pre-pressing and rolling a copper mesh coated with tin powder and tin powder.

[0045] According to the present invention, preferably, the average particle size of the tin powder is 50-80 nm. When the particle size of the tin powder is limited to the above range, the bending radius, tensile shear strength, and soldering rate can be further improved.

[0046] According to the present invention, preferably, the amount of self-propagating powder is such that the thickness of the self-propagating layer in the composite brazing film is 40-100 μm; wherein the self-propagating layer is obtained by pre-pressing and rolling the self-propagating powder.

[0047] According to the present invention, preferably, the average particle size of the self-propagating powder is 40-80 nm. When the particle size of the self-propagating powder is limited to the above range, the bending radius, tensile shear strength, and brazing rate can be further improved.

[0048] According to the present invention, preferably, the self-propagating powder comprises at least one element from Groups IIB, IVB, VB, VIB, IIA, IIIA, IVA, VIA, and VIII. More preferably, the self-propagating powder comprises at least one element from Groups IVB, IIIA, IVA, and VIII.

[0049] According to the present invention, preferably, the self-propagating powder comprises a first self-propagating powder and a second self-propagating powder, wherein the first self-propagating powder comprises at least one element from Groups IVA and VIII, and the second self-propagating powder comprises at least one element from Groups IIIA and IVA. More preferably, the first self-propagating powder comprises Ni and / or C. More preferably, the second self-propagating powder comprises Ti and / or Al.

[0050] According to the present invention, in order to further improve the bending radius, tensile shear strength and brazing rate, preferably, the atomic molar ratio of the first self-propagating powder and the second self-propagating powder is 0.5-1.5:1.

[0051] According to the present invention, preferably, the mixing method of the first self-propagating powder and the second self-propagating powder is as follows: the mixture of the first self-propagating powder and the second self-propagating powder with the solvent is mixed evenly in a degassing mixer, and then the solvent is removed in a vacuum chamber; wherein, the operating conditions of the degassing mixer include: revolution speed of 1500-3000 rpm, revolution-to-rotation ratio of 1:0.7-0.9, single stirring time of 10-20 seconds, total number of stirrings of 8-12 times, stirring interval of 2-10 minutes, and stirring temperature of 15-40°C; the operating conditions of the vacuum chamber include: vacuum degree of 0.1-0.2 kPa. Using the above mixing method, the self-propagating powder can be mixed more evenly, thereby improving the bonding strength between the self-propagating layer and the solder layer after pre-pressing and rolling.

[0052] According to the present invention, preferably, the solvent is ethyl acetate and / or ethanol.

[0053] According to the present invention, preferably, the content of the first self-propagating powder and the second self-propagating powder in the mixture is 35-45 wt%. Apart from the first and second self-propagating powders, the remaining components in the mixture are solvents.

[0054] A second aspect of the present invention provides a composite brazing film prepared by the method described above.

[0055] A third aspect of the present invention provides a composite brazing film comprising a self-propagating layer and solder layers formed by pre-pressing and rolling solder mesh and tin powder on both sides of the self-propagating layer;

[0056] Alternatively, the composite solder film may include a solder layer formed by pre-pressing and rolling solder mesh and tin powder, and self-propagating layers located on both sides of the solder layer.

[0057] According to the present invention, preferably, the thickness of the solder layer is 7-20 μm; the thickness of the self-propagating layer is 40-100 μm.

[0058] According to the present invention, preferably, the density of the self-propagating powder layer in the composite brazing film is 75-85% of the theoretical density of the self-propagating powder.

[0059] In this invention, the size of the copper mesh, the average particle size of the tin powder, the type of self-propagating powder, the molar ratio, and the average particle size in the composite brazing film are as described in the first aspect, and will not be repeated here.

[0060] A fourth aspect of the present invention provides the application of the aforementioned composite brazing film in welding planar and / or curved surface weldments. Particularly preferred is the application of the composite brazing film in welding curved surface weldments.

[0061] According to a particularly preferred embodiment of the present invention, a method for preparing a composite brazing film includes the following steps:

[0062] (1) Preparation of solder mesh: Lay out the copper mesh, brush adhesive on its surface, and then coat it with a layer of tin powder to obtain the solder mesh. The copper mesh has a mesh size of 120-125 mesh, the adhesive is PVB glue (polyvinyl butyral), and the average particle size of the tin powder is 50-55 nm.

[0063] (2) Mixing method of self-propagating powder: The mixture of nickel powder, titanium powder and solvent is mixed in a true degassing mixer, and then the solvent is removed in a vacuum chamber to obtain self-propagating powder. The atomic molar ratio of nickel powder to titanium powder is 0.9:1, and the average particle size of nickel powder and titanium powder is 40-42 nm. The content of nickel powder and titanium powder in the mixture is 40-42% by weight, and the solvent is ethyl acetate. The operating conditions of the degassing mixer include: revolution speed of 2000-2100 rpm, revolution-to-rotation ratio of 1:0.8-0.85, stirring time of 15-17s per stirring, a total of 9-10 stirrings, stirring interval of 5-6 minutes, and stirring temperature of 20-22℃. The operating conditions of the vacuum chamber include: vacuum degree of 0.1-0.15 kPa.

[0064] Preparation of the composite: A layer of solder mesh and tin powder is laid in a mold; then self-propagating powder is laid on the tin powder; then another layer of solder mesh and tin powder is laid on the self-propagating powder to prepare a composite with a sandwich structure.

[0065] (3) The composite with the mold is placed in a hydraulic press and pre-pressed. Then the mold is removed, and the pre-pressed composite is fed into a rolling mill and rolled at 175-180℃ to obtain a composite brazing film with a solder layer / self-propagating layer / solder layer structure. The pre-pressing pressure makes the density of the self-propagating powder layer after pre-pressing 60-62% of the theoretical density of the self-propagating powder; the rolling pressure makes the density of the self-propagating powder layer after rolling 80-82% of the theoretical density of the self-propagating powder; the amount of tin powder and self-propagating powder makes the total thickness of the composite brazing film after rolling 79-81μm; the thickness of the solder layers on both sides is 7-7.5μm, and the thickness of the self-propagating layer is 65-66μm.

[0066] The present invention will be described in detail below through embodiments.

[0067] The copper mesh has a wire diameter of 0.01-0.02mm, a thickness of 0.01-0.02mm, a length of 500mm, and a width of 110mm.

[0068] Pre-compression is carried out at room temperature (approximately 25°C).

[0069] Example 1

[0070] (1) Preparation of solder mesh: The copper mesh is laid flat, and an adhesive is brushed onto its surface. Then a layer of tin powder is applied to obtain the solder mesh. The mesh openings of the solder mesh are filled with tin powder. The copper mesh has an opening size of 120 mesh, the adhesive is PVB glue (polyvinyl butyral), and the average particle size of the tin powder is 55 nm.

[0071] (2) Mixing method of self-propagating powder: The mixture of nickel powder, titanium powder and solvent is mixed in a true degassing mixer, and then the solvent is removed in a vacuum chamber to obtain self-propagating powder. The atomic molar ratio of nickel powder and titanium powder is 1:1, and the average particle size of nickel powder and titanium powder is 40 nm. The content of nickel powder and titanium powder in the mixture is 40% by weight, and the solvent is ethyl acetate. The operating conditions of the degassing mixer include: revolution speed of 2000 rpm, revolution-to-rotation ratio of 1:0.8, stirring time of 15 s per stirring, a total of 10 stirrings, stirring interval of 5 minutes, and stirring temperature of 20℃. The operating conditions of the vacuum chamber include: vacuum degree of 0.1 kPa.

[0072] Preparation of the composite: A layer of solder mesh and tin powder is laid in a mold; then self-propagating powder is laid on the tin powder; then another layer of solder mesh and tin powder is laid on the self-propagating powder to prepare a composite with a sandwich structure.

[0073] (3) The composite with the mold is placed in a hydraulic press and pre-pressed (forging). A schematic diagram of the pre-pressing process is shown below. Figure 1 As shown, Figure 1After the mold is removed, the pre-pressed composite is fed into the rolling mill and rolled at 180°C (a schematic diagram of the rolling process is shown in the figure). Figure 2 As shown, a composite brazing film with a solder layer / self-propagating layer / solder layer structure was obtained. The pre-pressing pressure ensured that the density of the self-propagating powder layer after pre-pressing was 60% of the theoretical density of the self-propagating powder; the rolling pressure ensured that the density of the self-propagating powder layer after rolling was 80% of the theoretical density of the self-propagating powder; the amounts of tin powder and self-propagating powder ensured that the total thickness of the composite brazing film after rolling was 80 μm; the thickness of the solder layers on both sides was 7 μm, and the thickness of the self-propagating layer was 66 μm.

[0074] Example 2

[0075] (1) Preparation of solder mesh: Lay out the copper mesh, brush the adhesive on the surface of the copper mesh, and then apply a layer of tin powder to obtain the solder mesh. The mesh of the solder mesh is filled with tin powder. The size of the copper mesh is 150 mesh, the adhesive is PVB glue (polyvinyl butyral), and the average particle size of the tin powder is 60 nm.

[0076] (2) Mixing method of self-propagating powder: The mixture of aluminum powder, nickel powder and solvent is mixed in a true degassing mixer, and then the solvent is removed in a vacuum chamber to obtain self-propagating powder. The atomic molar ratio of aluminum powder to nickel powder is 1.2:1, and the average particle size of aluminum powder and nickel powder is 50nm. The content of aluminum powder and nickel powder in the mixture is 35% by weight, and the solvent is ethyl acetate. The operating conditions of the degassing mixer include: revolution speed of 2500rpm, revolution-to-rotation ratio of 1:0.8, stirring time of 15s per stirring, a total of 10 stirrings, stirring interval of 5 minutes, and stirring temperature of 15℃. The operating conditions of the vacuum chamber include: vacuum degree of 0.1KPa.

[0077] Preparation of the composite: A layer of solder mesh and tin powder is laid in a mold; then self-propagating powder is laid on the tin powder; then another layer of solder mesh and tin powder is laid on the self-propagating powder to prepare a composite with a sandwich structure.

[0078] (3) The composite with the mold is placed in a hydraulic press and pre-pressed (forging). A schematic diagram of the pre-pressing process is shown below. Figure 1 As shown, Figure 1 After the mold is removed, the pre-pressed composite is fed into a rolling mill and rolled at 150°C (a schematic diagram of the rolling process is shown in the figure). Figure 2As shown, a composite brazing film with a solder layer / self-propagating layer / solder layer structure was obtained. The pre-pressing pressure ensured that the density of the self-propagating powder layer after pre-pressing was 55% of the theoretical density of the self-propagating powder; the rolling pressure ensured that the density of the self-propagating powder layer after rolling was 75% of the theoretical density of the self-propagating powder; the amounts of tin powder and self-propagating powder ensured that the total thickness of the composite brazing film after rolling was 70 μm; the thickness of the solder layers on both sides was 10 μm, and the thickness of the middle self-propagating layer was 50 μm.

[0079] Example 3

[0080] (1) Preparation of solder mesh: The copper mesh is laid flat, adhesive is brushed on the surface of the copper mesh, and then a layer of tin powder is applied to obtain the solder mesh. The mesh of the solder mesh is filled with tin powder. The size of the copper mesh is 180 mesh, the adhesive is PVB glue (polyvinyl butyral), and the average particle size of the tin powder is 65nm.

[0081] (2) Mixing method of self-propagating powder: The mixture of nickel powder, titanium powder and solvent is mixed in a true degassing mixer, and then the solvent is removed in a vacuum chamber to obtain self-propagating powder. The atomic molar ratio of nickel powder and titanium powder is 1:1, and the average particle size of nickel powder and titanium powder is 45 nm. The content of nickel powder and titanium powder in the mixture is 45% by weight, and the solvent is ethyl acetate. The operating conditions of the degassing mixer include: revolution speed of 2800 rpm, revolution-to-rotation ratio of 1:0.8, stirring time of 15 s each time, stirring once every 10 minutes, stirring once in total, stirring temperature of 25℃. The operating conditions of the vacuum chamber include: vacuum degree of 0.2 kPa.

[0082] Preparation of the composite: A layer of solder mesh and tin powder is laid in a mold; then self-propagating powder is laid on the tin powder; then another layer of solder mesh and tin powder is laid on the self-propagating powder to prepare a composite with a sandwich structure.

[0083] (3) The composite with the mold is placed in a hydraulic press and pre-pressed (forging). A schematic diagram of the pre-pressing process is shown below. Figure 1 As shown, Figure 1 After the mold is removed, the pre-pressed composite is fed into the rolling mill and rolled at 160°C (a schematic diagram of the rolling process is shown in the figure). Figure 2 As shown, a composite brazing film with a solder layer / self-propagating layer / solder layer structure was obtained. The pre-pressing pressure ensured that the density of the self-propagating powder layer after pre-pressing was 65% of the theoretical density of the self-propagating powder; the rolling pressure ensured that the density of the self-propagating powder layer after rolling was 85% of the theoretical density of the self-propagating powder; the amounts of tin powder and self-propagating powder ensured that the total thickness of the composite brazing film after rolling was 80 μm; the thickness of the solder layers on both sides was 10 μm, and the thickness of the self-propagating layer was 60 μm.

[0084] Example 4

[0085] The method of Example 1 is followed, except that the preparation process of the composite in step (2) includes: dividing the self-propagating powder into two equal parts, and laying them flat in the mold in the order of the first part of self-propagating powder, solder mesh and tin powder, and the second part of self-propagating powder to obtain the composite.

[0086] The pre-pressing pressure ensures that the density of the self-propagating powder layer obtained after pre-pressing is 50% of the theoretical density of the self-propagating powder; the rolling pressure ensures that the density of the self-propagating powder layer obtained after rolling is 75% of the theoretical density of the self-propagating powder; the amount of tin powder and self-propagating powder used ensures that the total thickness of the composite brazing film obtained after rolling is 120 μm; the thickness of the middle solder layer is 20 μm, and the thickness of the self-propagating layers on both sides is 50 μm.

[0087] Example 5

[0088] The method of Example 1 was followed, except that the pre-pressing and rolling pressures were changed, but the amounts of tin powder and self-propagating powder were the same as in Example 1. The pre-pressing pressure was such that the density of the self-propagating powder layer obtained after pre-pressing was 40% of the theoretical density of the self-propagating powder. The rolling pressure was such that the density of the self-propagating powder layer obtained after rolling was 90% of the theoretical density of the self-propagating powder.

[0089] Example 6

[0090] The method was carried out according to Example 1, except that the average particle size of the tin powder was 90 nm, and the average particle size of the nickel powder and titanium powder was 100 nm.

[0091] Example 7

[0092] The method was carried out according to Example 1, except that the atomic ratio of nickel powder to titanium powder was 0.4:1.

[0093] Example 8

[0094] The method was carried out according to Example 1, except that the solder mesh was replaced with a perforated tin film with a thickness of 10 micrometers and a hole diameter of 0.1 millimeters.

[0095] Comparative Example 1

[0096] The method is carried out according to Example 1, except that the pre-pressing step is not included, that is, the composite is directly fed into the rolling mill for rolling and forming.

[0097] Because the composite is not pre-pressed, rolling is difficult and the uniformity of the rolled composite brazed film is poor.

[0098] Test Example 1

[0099] (1) The bending radius and tensile shear strength of the composite brazing films prepared in the above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0100] The bending radius test method is as follows: A two-point bending method is used to induce bending deformation at both ends of the composite 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 composite brazed film. Specifically, the critical radius of curvature refers to the minimum radius of curvature corresponding to the complete bending trajectory of the composite brazed film under two-point bending deformation until failure. A smaller bending radius indicates better flexibility of the composite brazed film.

[0101] The test method for tensile shear strength is as follows: according to standard ASTM D1002-10.

[0102] (2) The composite brazing films prepared in the above embodiments and comparative examples were tested to braze planar and curved parts (the parts are made of steel with tin plating on the steel surface). The welding conditions included: welding temperature 20°C and welding pressure 0.5 MPa. Then the brazing rate (i.e., effective welding area) of the welded parts was tested, and the test results are shown in Table 1.

[0103] Test method for effective weld 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 weld area = S0 ÷ S1 × 100%. The higher the effective weld area, the better the welding performance of the composite brazing film.

[0104] Table 1

[0105]

[0106] As can be seen from Table 1, compared with Comparative Example 1, Examples 1-8 of the present invention have a lower bending radius; particularly preferably, Examples 1-3 have a lower bending radius, while Examples 1-3 have higher tensile shear strength and brazing rate.

[0107] 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 method for preparing a composite brazing thin film, characterized in that, The method includes steps (1), (2-A) and (3); or, the method includes steps (1), (2-B) and (3); (1) Provide solder mesh: The solder mesh is a copper mesh with a surface electroplated with metal solder; Alternatively, the solder mesh can be prepared by coating the surface of a copper mesh with an adhesive and then with solder powder in sequence. (2-A) Preparation of composite: Solder mesh, tin powder, self-propagating powder, solder mesh, and tin powder are sequentially laid out and stacked to obtain a composite; (2-B) Preparation of composite: Divide the self-propagating powder into two parts, and then lay the first part of self-propagating powder, solder mesh, tin powder and the second part of self-propagating powder in sequence to obtain the composite; (3) The composite is pre-pressed and rolled in sequence; the rolling temperature is 80-180℃.

2. The method according to claim 1, wherein, The pre-compression pressure ensures that the density of the self-propagating powder layer obtained after pre-compression is 55-65% of the theoretical density of the self-propagating powder. And / or, the rolling pressure causes the density of the self-propagating powder layer obtained after rolling to be 75-85% of the theoretical density of the self-propagating powder.

3. The method according to claim 1, wherein, The metal solder includes at least one of tin, gold, and silver; Preferably, the aperture size of the copper mesh is 100-200 mesh.

4. The method according to claim 1, wherein, The adhesive includes polyvinyl butyral and / or welding adhesive.

5. The method according to claim 1, wherein, The amount of tin powder used results in a solder layer thickness of 7-20 μm in the composite brazing film; wherein the solder layer is obtained by pre-pressing and rolling solder mesh and tin powder; And / or, the average particle size of the tin powder is 50-80 nm; And / or, the amount of the self-propagating powder used is such that the thickness of the self-propagating layer in the composite brazing film is 40-100 μm; wherein the self-propagating layer is obtained by pre-pressing and rolling the self-propagating powder; And / or, the average particle size of the self-propagating powder is 40-80 nm.

6. The method according to claim 1, wherein, The self-propagating powder includes at least one element from Groups IIB, IVB, VB, VIB, IIA, IIIA, IVA, VIA and VIII; Preferably, the self-propagating powder comprises at least one element from Groups IVB, IIIA, IVA, and VIII; More preferably, the self-propagating powder includes a first self-propagating powder and a second self-propagating powder, wherein the first self-propagating powder includes at least one element from Group IVA and Group VIII, and the second self-propagating powder includes at least one element from Group IIIA and Group IVA; More preferably, the first self-propagating powder comprises Ni and / or C; More preferably, the second self-propagating powder comprises Ti and / or Al; More preferably, the atomic molar ratio of the first self-propagating powder to the second self-propagating powder is 0.5-1.5:

1.

7. The method according to claim 6, wherein, The mixing method for the first and second self-propagating powders is as follows: the mixture of the first and second self-propagating powders with the solvent is mixed evenly in a degassing mixer, and then the solvent is removed in a vacuum chamber. The operating conditions of the degassing mixer include: revolution speed of 1500-3000 rpm, revolution-to-rotation ratio of 1:0.7-0.9, single stirring time of 10-20 seconds, total number of stirrings of 8-12, stirring interval of 2-10 minutes, and stirring temperature of 15-40℃. The operating conditions of the vacuum chamber include: vacuum degree of 0.1-0.2 kPa. Preferably, the solvent is ethyl acetate and / or ethanol; Preferably, the content of the first self-propagating powder and the second self-propagating powder in the mixture is 35-45 wt%.

8. The composite brazing film prepared by the method according to any one of claims 1-7.

9. A composite brazing film, characterized in that, The composite brazing film includes a self-propagating layer and solder layers on both sides of the self-propagating layer, which are formed by pre-pressing and rolling solder mesh and tin powder. Alternatively, the composite brazing film may include a solder layer formed by pre-pressing and rolling solder mesh and tin powder, and self-propagating layers located on both sides of the solder layer; Preferably, the thickness of the solder layer is 7-20 μm; the thickness of the self-propagating layer is 40-100 μm.

10. The application of the composite brazing film according to claim 8 or 9 in welding planar and / or curved surface weldments.

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