A preformed composite metal foil solder and a method of making the same

Abstract

The application discloses a preformed composite metal foil solder and a preparation method thereof, and relates to the technical field of brazing. The composite metal foil solder comprises a carrier and a plurality of composite foil layers, the plurality of composite foil layers are stacked and deposited on the surface of the carrier, the composite foil layer comprises a copper oxide foil, an aluminum foil and a nickel foil which are stacked and deposited in sequence along the direction away from the carrier, and the carrier is a magnesium foil. The magnesium foil has the advantage of low ignition point, the heat generated by igniting the magnesium foil can stimulate the aluminothermic reaction of the copper oxide foil and the aluminum foil, the high temperature of the aluminothermic reaction makes the aluminum and the nickel foil and the copper generate intermetallic compounds or solid solutions, brazing connection is achieved, the brazing temperature is relatively low and is higher than 500 DEG C, the overheating damage of the aluminum alloy connecting piece to the heat-resistant part can be avoided, the brazing temperature and the leakage rate are reduced, and the sealing effect is improved.

Description

Technical Field

[0001] This invention relates to the field of brazing, and more particularly to a pre-formed composite metal foil brazing filler metal and its preparation method. Background Technology

[0002] Brazing is a method of interconnecting components by simultaneously heating a filler metal (below the melting point of the connector) and the connector to the melting temperature of the filler metal, then filling the gaps between the connectors with the liquid filler metal. Aluminum alloys, due to their excellent thermal and electrical conductivity and corrosion resistance, are increasingly widely used in aerospace, power, electronics, automotive, and shipbuilding industries. Therefore, the joining and processing techniques of aluminum alloys play a crucial role in product manufacturing. There are various joining methods for aluminum alloys, among which brazing offers several advantages, including no melting of the base material, low operating temperature, smooth and aesthetically pleasing joints, minimal welding deformation, high dimensional accuracy of the welded parts, and the ability to join different materials.

[0003] Generally speaking, the melting point of aluminum alloys is lower than that of pure aluminum (660℃), typically ranging from 607℃ to 650℃. However, the aluminum-based brazing filler metals currently used for brazing aluminum alloys, such as the commonly used aluminum-silicon filler metal, have a melting point of 577℃. The brazing temperature usually needs to be 25℃ higher than the melting point of the filler metal, meaning the brazing temperature needs to be at least 600℃. Such a high brazing temperature, close to the melting point of aluminum alloys, means that when simultaneously heating the aluminum-based filler metal and the aluminum alloy connector to melt the filler metal and then braze the aluminum alloy connector, the excessively high brazing temperature can easily cause overheating damage to the less heat-resistant parts of the aluminum alloy connector, leading to air leakage. Moreover, the brazing process consumes a lot of energy. Summary of the Invention

[0004] This invention provides a pre-formed composite metal foil brazing filler metal and its preparation method. By activating the aluminothermic reaction, local brazing can be initiated at a lower temperature, reducing the brazing temperature and leakage rate. This solves the problem of air leakage caused by overheating damage to heat-sensitive parts when brazing aluminum alloy connectors with aluminum-based brazing filler metal.

[0005] To address the aforementioned technical problems, one objective of this invention is to provide a pre-formed composite metal foil solder, comprising a carrier and several composite foil layers, wherein the composite foil layers are stacked and deposited on the surface of the carrier, and the composite foil layers include copper oxide foil, aluminum foil, and nickel foil stacked and deposited sequentially in a direction away from the carrier, and the carrier is magnesium foil.

[0006] By adopting the above scheme, the brazing temperature of the present invention needs to be further reduced while ensuring a low leakage rate. Taking advantage of the low ignition point of magnesium (490°C), the magnesium foil is ignited at a lower temperature during brazing. The heat generated causes the copper oxide foil and aluminum foil to undergo an aluminothermic reaction. The high temperature released by the aluminothermic reaction further causes the aluminum to form an intermetallic compound or solid solution with the nickel foil and the copper generated by the aluminothermic reaction, thus achieving the purpose of brazing connection. The aluminum foil is located between the copper oxide foil and the nickel foil, which facilitates the aluminothermic reaction between the aluminum foil and the copper oxide foil. It also facilitates the aluminum to use the heat generated by the aluminothermic reaction to fuse with the adjacent nickel foil. The nickel-aluminum alloy formed by nickel and aluminum has excellent anti-aging properties, which helps to improve the strength of the weld joint, enhance the sealing effect of the weld joint, reduce the risk of leakage, and ultimately effectively reduce the brazing temperature to prevent the aluminum alloy connector from overheating and causing leakage.

[0007] As a preferred embodiment, the thickness of each layer of copper oxide foil, aluminum foil and nickel foil is independent and ranges from 150 to 700 nm.

[0008] By adopting the above-described scheme, this invention controls the thickness of copper oxide foil, aluminum foil, and nickel foil within a specific range, thereby reducing brazing temperature and leakage rate. Since magnetron sputtering equipment requires numerous preparatory steps such as vacuuming and cleaning before each operation, if the thickness of the copper oxide foil, aluminum foil, and nickel foil is too small, then composite metal foils of equivalent thickness are needed, resulting in excessively long preparation time for magnetron sputtering. Simultaneously, if the thickness of each layer of copper oxide foil, aluminum foil, and nickel foil is too large, it will affect the aluminothermic reaction during brazing and also hinder the sufficient contact between aluminum, copper, and nickel to form intermetallic compounds or solid solutions for achieving the brazing connection.

[0009] As a preferred embodiment, the thickness of each layer of copper oxide foil, aluminum foil and nickel foil is independent and ranges from 300nm to 500nm.

[0010] As a preferred embodiment, the thickness ratio of each layer of aluminum foil to copper oxide foil is ≥1 / 2.

[0011] By adopting the above scheme, the mass ratio of aluminum to copper oxide to react completely is 9:40. After density and volume conversion, the thickness ratio of aluminum foil to copper oxide foil required for the complete reaction of aluminum and copper oxide is 1:2. Moreover, the copper and nickel produced by the reaction of aluminum and copper oxide are infinitely soluble, which is beneficial to brazing. If there is excess aluminum after the reaction, it can form intermetallic compounds with nickel, which is also beneficial to brazing. Therefore, ensuring that the mass of aluminum foil participating in the reaction is sufficient can reduce the brazing temperature and leakage rate.

[0012] As a preferred embodiment, the thickness ratio of each layer of aluminum foil to copper oxide foil is ≥5 / 3.

[0013] As a preferred embodiment, the thickness of the carrier is 2-4 μm.

[0014] By adopting the above-described scheme, the present invention controls the thickness of the carrier within a specific range, thereby reducing the brazing temperature and leakage rate. If the carrier is too thin, the manufacturing cost will be too high, and the heat generated by insufficient mass will not be enough to trigger the aluminothermic reaction; if the carrier is too thick, it will be difficult to ignite, and the excessive magnesium foil will produce too much magnesium oxide slag after ignition, affecting the brazing quality.

[0015] As a preferred embodiment, the composite foil layer is located away from the carrier and its side facing away from the carrier is coated with aluminum flux.

[0016] By adopting the above method, aluminum flux can break the oxide film on the surface of aluminum alloy brazed parts, increase the activity of aluminum, and push the oxide slag generated during the brazing process to the vicinity of the weld, thus ensuring the brazing quality of the weld.

[0017] As a preferred embodiment, the aluminum flux accounts for 5-10% of the total mass of the composite metal foil solder.

[0018] As a preferred embodiment, the aluminum flux is cesium fluoroaluminate.

[0019] To address the aforementioned technical problems, a second objective of this invention is to provide a method for preparing pre-formed composite metal foil solder, comprising the following steps:

[0020] S1. Copper oxide foil, aluminum foil and nickel foil are sequentially deposited on the carrier using magnetron sputtering to form a composite foil layer. Multiple composite foil layers are deposited repeatedly, and the process ends with aluminum foil or nickel foil until the desired thickness is obtained.

[0021] S2. Apply aluminum flux to the side of the composite foil layer that is away from the carrier and faces away from the carrier to obtain the pre-formed composite metal foil solder.

[0022] As a preferred embodiment, in S1, the carrier is first ultrasonically cleaned and dried sequentially with deionized water, anhydrous ethanol, and acetone.

[0023] As a preferred option, in S1, the purity of the target material used for magnetron sputtering is above 99.95%.

[0024] As a preferred option, in S1, the sputtering gas pressure of magnetron sputtering is 0.5-1 Pa, the sputtering power is 100-250 W, and the argon flow rate is 35-50 ml / min.

[0025] As a preferred embodiment, in S2, the composite metal foil solder can be cut to the required size before or after applying the aluminum flux.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention uses magnesium foil as a carrier, which has a low ignition point of 490°C. The heat generated by igniting the magnesium foil can stimulate the aluminothermic reaction between the copper oxide foil and the aluminum foil. The aluminum foil is located between the copper oxide foil and the nickel foil. The high temperature of the aluminothermic reaction causes the aluminum and nickel foil, as well as the copper produced by the aluminothermic reaction, to form intermetallic compounds or solid solutions, achieving brazing connection. The brazing temperature is as low as slightly over 500°C. The low brazing temperature can avoid overheating damage to the heat-sensitive parts of the aluminum alloy connector and reduce the leakage rate.

[0028] 2. The aluminum foil is positioned between the copper oxide foil and the nickel foil, which facilitates the aluminothermic reaction between the aluminum foil and the copper oxide foil. It also facilitates the aluminum to use the heat generated by the aluminothermic reaction to fuse with the adjacent nickel foil. The nickel-aluminum alloy formed by nickel and aluminum has excellent anti-aging properties, which helps to improve the strength of the solder joint, enhance the sealing effect of the solder joint, reduce the risk of leakage, and ultimately effectively reduce the brazing temperature, preventing the aluminum alloy connector from overheating and causing leakage.

[0029] 3. The composite metal foil of the present invention is pre-coated with aluminum flux. Compared with the method of dipping liquid aluminum flux in the brazing process, the amount of aluminum flux can be precisely controlled, which will not cause excessive splashing of aluminum flux. The aluminum flux can break the oxide film on the surface of the aluminum alloy brazed parts, increase the activity of aluminum, and push the oxide slag generated during the brazing process to the surrounding area of ​​the weld, thus ensuring the brazing quality of the weld. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A preformed composite metal foil solder comprises a carrier and several stacked composite foil layers. The composite foil layers are deposited on the upper surface of the carrier. The composite foil layers include copper oxide foil, aluminum foil, and nickel foil stacked sequentially from bottom to top. The carrier is magnesium foil, i.e., multiple layers of copper oxide foil, aluminum foil, and nickel foil are alternately deposited on the magnesium foil. The thickness of the magnesium foil carrier is 4 μm. The thickness of each aluminum foil layer is 500 nm, the thickness of each copper oxide foil layer is 300 nm, and the thickness of each nickel foil layer is 300 nm. That is, the thickness ratio of aluminum foil to copper oxide foil is 5:3. The total thickness of the metal layers of the composite metal foil is about 50 μm. It has a circular ring structure with an inner diameter of 10 mm and an outer diameter of 16 mm. The side of the composite foil layer away from the carrier and facing away from the carrier is pre-coated with cesium fluoroaluminate aluminum flux. The mass of cesium fluoroaluminate aluminum flux accounts for 10% of the total mass of the composite metal foil.

[0033] The above-mentioned method for preparing a pre-formed composite metal foil solder includes the following steps:

[0034] S1. A magnesium foil with a thickness of 4μm was ultrasonically cleaned sequentially with deionized water, anhydrous ethanol, and acetone, and then dried to serve as a carrier for depositing metal foil.

[0035] S2. Copper oxide foil was deposited on a magnesium foil carrier using magnetron sputtering, followed by the sequential deposition of aluminum foil and nickel foil. The purity of the copper oxide target, aluminum target, and nickel target used for depositing the copper oxide foil, aluminum foil, and nickel foil was all above 99.95%. The sputtering pressure of the magnetron sputtering was 1.0 Pa, the sputtering power was 250 W, and the argon flow rate was 50 ml / min.

[0036] S3. Repeat step S2 to deposit multiple layers of copper oxide foil, aluminum foil and nickel foil alternately, ending with nickel foil, until a composite foil layer with a thickness of about 50 μm is obtained;

[0037] S4. Cut the composite metal foil into circular rings with an outer diameter of 16mm and an inner diameter of 10mm as needed;

[0038] S5. Apply cesium fluoroaluminate aluminum flux to the side of the composite foil layer that is away from the magnesium foil and opposite to the magnesium foil to obtain the pre-formed composite metal foil solder.

[0039] Example 2

[0040] A preformed composite metal foil solder differs from Example 1 in that the thickness of each aluminum foil layer is 300 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 1:1.

[0041] Example 3

[0042] A preformed composite metal foil solder differs from Example 1 in that the thickness of each aluminum foil layer is 150 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 1:2.

[0043] Example 4

[0044] A preformed composite metal foil solder differs from Example 1 in that the thickness of each aluminum foil layer is 700 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 7:3.

[0045] Example 5

[0046] A preformed composite metal foil solder differs from Example 1 in that the thickness of each layer of copper oxide foil is 500 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 1:1.

[0047] Example 6

[0048] A preformed composite metal foil solder differs from Example 1 in that the thickness of each layer of copper oxide foil is 150 nm, that is, the thickness ratio of aluminum foil to copper oxide foil is 10:3.

[0049] Example 7

[0050] A preformed composite metal foil solder differs from Example 1 in that the thickness of each layer of copper oxide foil is 700 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 5:7.

[0051] Example 8

[0052] A preformed composite metal foil solder differs from Example 1 in that the thickness of each aluminum foil layer is 150 nm and the thickness of each copper oxide foil layer is 450 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 1:3.

[0053] Example 9

[0054] A preformed composite metal foil solder differs from Example 1 in that the thickness of each aluminum foil layer is 900 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 3:1.

[0055] Example 10

[0056] A preformed composite metal foil solder differs from Example 1 in that the thickness of each layer of copper oxide foil is 1200 nm, i.e., the thickness ratio of aluminum foil to copper oxide foil is 5:12.

[0057] Example 11

[0058] A preformed composite metal foil solder differs from Example 1 in that each layer of copper oxide foil has a thickness of 900 nm, and the thickness ratio of aluminum foil to copper oxide foil is 5:9.

[0059] Example 12

[0060] A preformed composite metal foil solder differs from Example 1 in that the thickness of each nickel foil layer is 500 nm.

[0061] Example 13

[0062] A preformed composite metal foil solder differs from Example 1 in that the thickness of each nickel foil layer is 150 nm.

[0063] Example 14

[0064] A preformed composite metal foil solder differs from Example 1 in that the thickness of each nickel foil layer is 700 nm.

[0065] Example 15

[0066] A preformed composite metal foil solder differs from Example 1 in that the thickness of each nickel foil layer is 1000 nm.

[0067] Example 16

[0068] A preformed composite metal foil solder differs from Example 1 in that the thickness of the magnesium foil carrier is 2 μm.

[0069] Example 17

[0070] A preformed composite metal foil solder differs from Example 1 in that the thickness of the magnesium foil carrier is 1 μm.

[0071] Example 18

[0072] A preformed composite metal foil solder differs from Example 1 in that the thickness of the magnesium foil carrier is 8 μm.

[0073] Comparative Example 1

[0074] A preformed composite metal foil solder differs from Example 1 in that the carrier is tin foil.

[0075] Comparative Example 2

[0076] A preformed composite metal foil solder differs from Example 1 in that the composite foil layer comprises aluminum foil, copper oxide foil and nickel foil stacked sequentially from bottom to top, that is, multiple layers of aluminum foil, copper oxide foil and nickel foil are alternately deposited on magnesium foil.

[0077] Comparative Example 3

[0078] A preformed composite metal foil solder differs from Example 1 in that it uses cobalt foil of the same thickness instead of nickel foil.

[0079] Comparative Example 4

[0080] An aluminum alloy brazing filler metal is made of commercially available Al88Si12 filler metal with a total thickness of 50μm. It has a circular ring structure with an inner diameter of 10mm and an outer diameter of 16mm. The surface of the filler metal is coated with cesium fluoroaluminate aluminum flux, and the mass of cesium fluoroaluminate aluminum flux accounts for 10% of the total mass.

[0081] Performance testing

[0082] To further verify the performance of the preformed composite metal foil of the present invention, the composite metal foil brazing filler metals of Examples 1-18 and Comparative Examples 1-3 were used as the test group, and the brazing filler metal of Comparative Example 4 was used as the control group. Brazing tests were conducted on both groups. The sealing device was assembled with the brazing filler metals of the test group and the control group, respectively, and laser brazing was performed. The brazing filler metals in both the test group and the control group were circular rings with an inner diameter of 10 mm, an outer diameter of 16 mm, and a thickness of 50 μm. The following tests were performed:

[0083] 1) Record the temperature range required for brazing. The temperature range required for brazing is measured with an infrared temperature detector. The lower the temperature, the easier it is to achieve a good brazing seal effect. The test results are shown in Table 1.

[0084] 2) After brazing, a sealing leakage test is performed. The sealing leakage test is conducted using a helium mass spectrometer leak detector. The test standard is QJ3212-2005 "Helium Mass Spectrometer Back Pressure Leak Detection Method". The smaller the leakage rate, the better the sealing effect. The test results are shown in Table 1.

[0085] Table 1. Brazing performance tests of the brazing filler metals in the embodiments and comparative examples of the present invention.

[0086]

[0087]

[0088] Comparing the performance test results of Example 1 and Comparative Example 4 in Table 1, it can be seen that, due to the advantage of magnesium having a low ignition point of 490°C, the heat generated by igniting the magnesium foil at a relatively low temperature during brazing can stimulate the aluminothermic reaction between the copper oxide foil and the aluminum foil. The high temperature released by the aluminothermic reaction further causes the aluminum to form an intermetallic compound or solid solution with the nickel foil and the copper generated by the aluminothermic reaction, thus achieving the purpose of brazing connection. The present invention only needs to apply a temperature of just over 500°C to the weld to achieve the purpose of burning the brazing filler metal and connecting the aluminum alloy connector. However, the aluminum-silicon brazing filler metal used in Comparative Example 4 has a brazing temperature of over 600°C, which is close to the melting point of the aluminum alloy connector. This can easily cause the aluminum alloy connector to be damaged due to local heat intolerance. Local damage leads to a significantly higher leakage rate, and the energy consumption of brazing is high.

[0089] By comparing the performance test results of Example 1 and Comparative Example 3 in Table 1, it can be seen that Example 1 of the present invention utilizes the heat generated by the aluminothermic reaction to promote the fusion of aluminum and adjacent nickel foils. The resulting nickel-aluminum alloy has excellent anti-aging properties, which is beneficial to improving the strength of the weld joint, enhancing the sealing effect of the weld joint, and reducing the risk of leakage.

[0090] Comparing the performance test results of Example 1 and Comparative Example 2 in Table 1, it can be seen that in Comparative Example 2, since aluminum foil is first deposited on magnesium foil, the aluminum foil is easily oxidized to aluminum oxide when the magnesium foil is ignited. Due to the presence of other components, some aluminothermic reactions cannot be fully carried out, resulting in a relatively high brazing temperature and an increased leakage rate. In contrast, in this invention, copper oxide foil, aluminum foil, and nickel foil are deposited sequentially on magnesium foil. The temperature generated when the magnesium foil is ignited can trigger an aluminothermic reaction between the copper oxide foil and the aluminum foil, thereby achieving the purpose of reducing the brazing temperature and leakage rate.

[0091] A comparison of the performance test results of Examples 1 and 16-18 of the present invention in Table 1 shows that the thickness of the carrier magnesium foil affects the brazing temperature and leakage rate. If the magnesium foil is too thin, the manufacturing cost is too high, and the heat generated due to its small mass is insufficient to trigger the aluminothermic reaction. If the magnesium foil is too thick, it is not easy to ignite, and the magnesium oxide slag produced after ignition will be too large, affecting the brazing quality. The magnesium foil thickness in Examples 1 and 16 is in the range of 2-4 μm, which makes the brazing temperature and leakage rate of the brazing filler metal relatively low.

[0092] By comparing the performance test results of Example 1 and Comparative Example 1 in Table 1, it can be seen that the magnesium foil of the present invention can burn and generate heat at a low ignition point of 490°C, which can stimulate the aluminothermic reaction. However, the tin foil of Comparative Example 1 does not burn and only melts from solid to liquid at high temperature, without generating heat. It cannot provide a high temperature to stimulate the aluminothermic reaction, resulting in higher brazing temperature and leakage rate.

[0093] By comparing the performance test results of Examples 1 and 12-15 of the present invention in Table 1, it can be seen that controlling the thickness of the nickel foil in Examples 1 and 12-14 to be 150-700nm can ensure a lower brazing temperature and leakage rate. However, the thickness of the nickel foil in Example 15 is relatively large, which will affect the aluminothermic reaction during brazing, resulting in an increase in brazing temperature and leakage rate.

[0094] Comparing the performance test results of Examples 1-7 and 10 of the present invention in Table 1, it can be seen that the mass ratio of aluminum to copper oxide in the complete aluminothermic reaction is 9:40. After conversion according to density and volume, the total thickness ratio of aluminum foil and copper oxide foil required for the complete reaction of aluminum and copper oxide is 1:2. Moreover, the copper and nickel generated by the aluminothermic reaction are infinitely soluble, which is beneficial to brazing. Furthermore, if there is excess aluminum after the reaction, it can form intermetallic compounds with Ni, which is also beneficial to brazing. Therefore, it is only necessary to ensure that the mass of aluminum foil participating in the reaction is sufficient, that is, the thickness ratio of aluminum foil to copper oxide foil needs to be no less than 1:2. However, in Examples 8 and 10, the thickness ratio of aluminum foil to copper oxide foil is less than 1:2, and the aluminum foil thickness is less, which affects the occurrence of part of the aluminothermic reaction, resulting in an increased leakage rate in Example 8 and a higher brazing temperature and leakage rate in Example 10.

[0095] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A pre-formed composite metal foil solder, characterized in that, The device includes a carrier and several composite foil layers, wherein the composite foil layers are stacked and deposited on the surface of the carrier, and the composite foil layers include copper oxide foil, aluminum foil and nickel foil stacked and deposited sequentially in a direction away from the carrier, and the carrier is magnesium foil. The thickness of each layer of copper oxide foil, aluminum foil, and nickel foil is independent and ranges from 150 to 700 nm, and the thickness ratio of each layer of aluminum foil to copper oxide foil is ≥1 / 2.

2. The pre-formed composite metal foil solder as described in claim 1, characterized in that, The thickness of each layer of copper oxide foil, aluminum foil, and nickel foil is independent and ranges from 300 to 500 nm.

3. The pre-formed composite metal foil solder as described in claim 1, characterized in that, The thickness ratio of each layer of aluminum foil to copper oxide foil is ≥5:

3.

4. The pre-formed composite metal foil solder as described in claim 1, characterized in that, The thickness of the carrier is 2-4 μm.

5. The pre-formed composite metal foil solder as described in claim 1, characterized in that, The composite foil layer is coated with aluminum flux on the side away from the carrier and facing away from the carrier, and the mass of the aluminum flux accounts for 5-10% of the total mass of the composite metal foil solder.

6. The pre-formed composite metal foil solder as described in claim 5, characterized in that, The aluminum flux is cesium fluoroaluminate.

7. A method for preparing a pre-formed composite metal foil solder as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Copper oxide foil, aluminum foil and nickel foil are sequentially deposited on the carrier using magnetron sputtering to form a composite foil layer. Multiple composite foil layers are deposited repeatedly, and the process ends with aluminum foil or nickel foil until the desired thickness is obtained. S2. Apply aluminum flux to the side of the composite foil layer that is away from the carrier and faces away from the carrier to obtain the pre-formed composite metal foil solder.

8. The method for preparing a pre-formed composite metal foil solder as described in claim 7, characterized in that, In S1, the carrier is pre-cleaned and dried sequentially by ultrasonic cleaning with deionized water, anhydrous ethanol, and acetone; the purity of the target material used for magnetron sputtering is above 99.95%, the sputtering pressure of magnetron sputtering is 0.5-1 Pa, the sputtering power is 100-250 W, and the argon flow rate is 35-50 ml / min.

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