Ag-Al-Cu-In-Sm-Ti multi-principal-element eutectic brazing filler metal and preparation method and application thereof

Abstract

The invention relates to the technical field of brazing, in particular to Ag-Al-Cu-In-Sm-Ti multi-principal-element eutectic brazing filler metal as well as a preparation method and application of the Ag-Al-Cu-In-Sm-Ti multi-principal-element eutectic brazing filler metal. The Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic brazing filler metal comprises the following components in percentage by atom: 68.5% to 72.5% of Ag, 8.5% to 12.5% of Al, 7.5% to 10.8% of Cu, 4.5% to 10% of In, 1.5% to 3.0% of Sm and 2.0% to 2.8% of Ti. According to the method, the design thought of multiple principal elements and eutectic components is combined, good matching of the brazing filler metal welding temperature and the mechanical property is achieved, the welding temperature is lowered, and the joint strength is improved; meanwhile, device performance degradation or failure caused by resistivity increase in the long-term service process can be reduced, and the durability of the connector in the high-temperature environment can be improved through the diffusion hysteresis effect of the multi-principal-element alloy. And the preparation process is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of brazing, and in particular to an Ag-Al-Cu-In-Sm-Ti multi-principal-element eutectic brazing filler metal and a preparation method and application thereof. Background Art

[0002] Brazing, as an essential component of joining technology, is widely used in electronics, aerospace, automotive, and chemical industries. The performance of the brazing filler metal alloy directly impacts the quality and reliability of the brazed joint. Ag-based brazing fillers, due to their excellent electrical and thermal conductivity and corrosion resistance, can be used to braze most ferrous and non-ferrous metals, making them widely used in electronics, aerospace, medical devices, and other fields. Low-temperature Ag-based brazing fillers, such as Ag-Cu, Ag-Sn, and Ag-Ni, are particularly well-suited for applications that require protection from high-temperature damage due to their low melting points (typically between 600°C and 900°C). The low resistivity of Ag-based brazing fillers significantly reduces the contact resistance of the solder joint, thereby reducing energy loss during current transmission. This is particularly important for high-density integrated circuits and high-power devices, improving overall energy efficiency while preventing device degradation or failure due to local overheating. However, with technological advancements, higher performance demands and complex service environments are placing even higher demands on the mechanical properties of the brazing filler metal.

[0003] Currently, traditional Ag-based solders have low microhardness and are prone to wear, which affects the life of the connector. Furthermore, over the long term, Ag-based solders often oxidize, resulting in increased resistivity and local overheating, leading to device performance degradation or failure. Furthermore, traditional solder alloys are mostly binary or ternary alloys, making it difficult to achieve specific performance optimization. Existing Ag-based binary or ternary solders have the disadvantages of high melting points and insufficient weld joint strength, making it difficult to achieve a good match between welding temperature and joint mechanical properties. Excessively high welding temperatures can cause irreversible changes in the structure and properties of the weld, and in severe cases, can even cause degradation of the weld, causing it to lose its original performance and function, thereby affecting its service life and safety. Welded joints are a key part connecting two or more components. If their strength is insufficient, the overall safety of the structure may be reduced. When subjected to external forces or loads, joints with lower strength are more likely to deform, crack, or even break, affecting the stability and reliability of the entire structure.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first objective of the present invention is to provide an Ag-Al-Cu-In-Sm-Ti multi-principal-element eutectic solder. Combining the design principles of multiple principal elements and eutectic composition, the addition of Al, Cu, In, Sm, and Ti to a silver-based solder achieves a good match between the solder's welding temperature and mechanical properties, reducing welding temperatures and improving joint strength. This also reduces device performance degradation or failure caused by increased resistivity during long-term service. The diffusion hysteresis effect of the multi-principal-element alloy further improves joint durability in high-temperature environments. This solves the technical problems of traditional silver-based solders, such as increased resistivity, high melting points, and low weld zone strength, during long-term service.

[0006] The second object of the present invention is to provide a method for preparing the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder as described above, which is simple, easy to implement, and has broad application prospects and economic benefits.

[0007] The third object of the present invention is to provide an application of the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder as described above in brazing of copper-based materials.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] An Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder comprises, by atomic percentage, 68.5%-72.5% of Ag, 8.5%-12.5% ​​of Al, 7.5%-10.8% of Cu, 4.5%-10% of In, 1.5%-3.0% of Sm, and 2.0%-2.8% of Ti.

[0010] Preferably, the atomic content ratio of the In to the Sm is 2-4.5:1.

[0011] Preferably, the liquidus temperature of the solder is 650-700°C.

[0012] Preferably, the solder is in the form of powder, and the average particle size of the powder is 35-45 μm.

[0013] A method for preparing the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder according to any one of the aforementioned embodiments comprises the following steps:

[0014] S1. Ag, Al, Cu, In, Sm and Ti are mixed according to the formula ratio;

[0015] S2. The raw materials prepared in step S1 are vacuum melted, electromagnetic stirring is used during the melting process, and the melting is repeated several times to obtain a solder alloy ingot;

[0016] S3. The solder alloy ingot is subjected to vacuum induction melting, and after the solder alloy ingot is completely melted, gas atomization powdering is performed to obtain the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder.

[0017] Preferably, in step S1, the purity of the raw materials used is not less than 99.9 wt.%.

[0018] Preferably, in step S2, the smelting is performed no less than 5 times.

[0019] Preferably, in step S3, inert gas is used as the atomizing medium, and the pressure of the atomizing gas is 3.5-4.5 MPa.

[0020] Application of the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder described in any of the aforementioned embodiments or the solder prepared by the preparation method of the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder described in any of the aforementioned embodiments in brazing of copper-based materials.

[0021] The method for brazing copper-based materials using the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder comprises the following steps:

[0022] The Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder is laid between two copper-based solders, a pressure head is installed, and vacuum brazing is performed.

[0023] Preferably, the vacuum brazing temperature is 700-750° C., and the holding time is 8-15 minutes.

[0024] Preferably, after the vacuum brazing, the shear strength of the welding area is 235-300 MPa.

[0025] Preferably, after the vacuum brazing, the resistivity of the welding area is 3.8-5.2 μΩ·cm.

[0026] Preferably, after the vacuum brazing, the welded joint is heat treated at 250-350° C. for 3-5 hours in an air atmosphere, and the resistivity of the welded area increases by no more than 15%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention is based on the design concept of multiple principal elements and eutectic point composition, and obtains Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder alloy by adding Al, Cu, In, Sm, and Ti elements. This alloy not only has a low melting point and good wettability, but also has the advantages of high strength, high toughness, good corrosion resistance and high-temperature stability. During the brazing process, the alloy can quickly fill the weld and form a good metallurgical bond with the base material, thereby improving the quality and reliability of the brazed joint. By adding In and Sm, the increase in resistivity caused by surface defects caused by environmental corrosion during long-term service can be reduced. The Ag-based multi-principal element eutectic solder of the present invention has a more uniform composition and structure than traditional Ag-based solder, melts evenly to avoid stratification, and has better fluidity and wettability to the substrate. It can be used for brazing of copper-based materials, and the shear strength of the resulting joint is as high as 296MPa. In addition, the preparation method of the alloy is simple and easy to implement, and has broad application prospects and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a scanning electron microscope photograph of the silver-based multi-principal element eutectic solder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0032] The first aspect of the present invention provides an Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder, which comprises, in atomic percentage, 68.5%-72.5% Ag, 8.5%-12.5% ​​Al, 7.5%-10.8% Cu, 4.5%-10% In, 1.5%-3.0% Sm, and 2.0%-2.8% Ti.

[0033] The present invention is based on the concept of multi-principal element and eutectic point composition design. A multi-principal element eutectic solder is formed by adding Al, Cu, In, Sm, and Ti elements to a silver-based solder. Among them, the appropriate addition of Al element can lower the melting point of the Ag-based solder and improve the wettability of the solder, which is beneficial to the spreading of the solder during the brazing process. The addition of Al element can also refine the brazing seam structure and reduce the formation of brittle phases, thereby improving the strength and toughness of the brazed joint and enhancing the mechanical properties. The Cu element can significantly improve the fluidity of the Ag-based solder, making it easier for the solder to fill the weld and enhancing the strength of the joint. The addition of Cu also helps to optimize the microstructure of the solder, reduce defects, and improve the reliability of the brazed joint. In and the rare earth element Sm form a dense composite oxide film on the alloy surface, which can reduce the additional resistivity increase caused by surface defects caused by environmental corrosion during long-term service. The appropriate addition of In element can also improve the mechanical properties of the brazed joint and enhance the bearing capacity of the joint. As a rare earth element, Sm is adsorbed at grain boundaries, reducing impurity segregation in raw materials or during welding, increasing grain boundary interface strength, and enhancing the material's shear strength. It also effectively reduces grain boundary scattering, thereby reducing resistivity. Ti is an active element that significantly increases the activity of Ag-based solder, enhancing its wettability to the base material and facilitating its spreading and penetration during brazing. The addition of Ti also enhances the mechanical properties of the brazed joint, such as tensile strength and yield strength, while also improving the joint's corrosion resistance.

[0034] Compared to traditional solder designs based on binary or ternary alloys, the presence of multiple elements in multi-principal-element alloys results in a higher degree of disorder and a more uniform atomic distribution, thereby improving the alloy's performance stability. The differences in atomic size between the different elements lead to lattice distortion, which increases the probability of electron scattering and enhances mechanical properties. Due to the diffusion hysteresis effect, multi-principal-element alloys exhibit excellent stability and durability in high-temperature service environments, making them less susceptible to grain coarsening and recrystallization.

[0035] Compared with traditional crystalline solders, eutectic solders have the following advantages: (1) Low and stable melting point: The melting point of eutectic solders is usually lower than the melting point of its constituent metals, which allows the eutectic solders to melt and spread quickly during the brazing process, reducing the damage caused by thermal expansion and is very suitable for the soldering of electronic components that are highly sensitive to temperature; (2) Good wetting properties: Eutectic solders usually have good wetting properties, which means they can more easily wet the surface of the base material and form a strong weld joint; (3) Excellent mechanical properties: Eutectic solders usually have higher mechanical properties at room temperature, making the weld joint more reliable and able to withstand greater stress and deformation; (4) Uniform composition and refined structure: The chemical composition of eutectic solders is usually relatively uniform, and the alloy structure is single and refined, which allows the eutectic solders to melt and spread more evenly during the brazing process, reducing the occurrence of segregation and delamination.

[0036] The present invention obtains a eutectic solder alloy with excellent performance by designing and optimizing the Ag-Al-Cu-In-Sm-Ti multi-principal alloy composition. This alloy not only has a low melting point and good wettability, but also has the advantages of high strength, high toughness, good corrosion resistance and high-temperature stability. During the brazing process, the alloy can quickly fill the weld and form a good metallurgical bond with the base material, thereby improving the quality and reliability of the brazed joint. The conflict between the welding temperature and joint strength of traditional Ag-based solders is greatly improved. The alloy composition of the present invention has the strength advantage brought by the multi-principal component and the low melting point advantage of the eutectic composition design, which is conducive to assembly and gap filling in the precision welding process. And the solder welding area of ​​the present invention has high strength and good toughness.

[0037] In some embodiments, typically but not limiting, for example, in the Ag-Al-Cu-In-Sm-Ti multi-principal eutectic solder, the atomic percentage of Ag can be any value among 68.5%, 68.9%, 70.5%, 72%, 72.5%, or a range consisting of any two values; the atomic percentage of Al can be any value among 8.5%, 9%, 10%, 11%, 12%, 12.5%, or a range consisting of any two values; the atomic percentage of Cu can be any value among 7.6%, 8.5%, 9.5%, 10%, 10.8%. The atomic percentage of In can be any point value among 4.5%, 4.85%, 5.2%, 6.5%, 7.5%, 8.5%, 9.7%, 10%, or a range value consisting of any two point values; the atomic percentage of Sm can be any point value among 1.5%, 2%, 2.5%, 3%, or a range value consisting of any two point values; the atomic percentage of Ti can be any point value among 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.65%, 2.8%, or a range value consisting of any two point values.

[0038] In some specific embodiments of the present invention, in the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder, the atomic content ratio of In and Sm is 2-4.5:1, for example, it can be any point value among 2:1, 2.4:1, 3:1, 3.5:1, 3.9:1, and 4.5:1, or a range value consisting of any two point values; In and Sm can synergistically reduce the additional resistivity increase caused by surface defects caused by environmental corrosion during long-term service. The ratio of the two has an important influence on the conductivity stability during service. Controlling it within the above range is beneficial to preventing the increase in conductivity during service. Too high or too low a ratio will lead to an increase in the additional conductivity increase.

[0039] In some specific embodiments of the present invention, the liquidus temperature of the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder is 650-700°C, for example, it can be any point value among 650°C, 655°C, 665°C, 675°C, 685°C, 692°C, 700°C, or a range value consisting of any two point values; the multi-principal element eutectic solder provided by the present invention has a low melting temperature, can reduce the brazing temperature, and improve the strength of the brazing area.

[0040] In some specific embodiments of the present invention, the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder is in the form of powder, and the average particle size of the powder is 35-45 μm. For example, it can be any point value among 35 μm, 36 μm, 38.7 μm, 40 μm, 43 μm, 45 μm, or a range value consisting of any two point values.

[0041] A second aspect of the present invention provides a method for preparing the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder according to any one of the aforementioned embodiments, comprising the following steps:

[0042] S1. Ag, Al, Cu, In, Sm and Ti are mixed according to the formula ratio;

[0043] S2. The raw materials prepared in step S1 are vacuum melted, electromagnetic stirring is used during the melting process, and the melting is repeated several times to obtain a solder alloy ingot;

[0044] S3. The solder alloy ingot is subjected to vacuum induction melting. After the solder alloy ingot is completely melted, gas atomization is performed to pulverize the ingot to obtain Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder powder.

[0045] The method of the present invention has a simple and easy preparation process, and the prepared solder powder has a uniform and concentrated particle size distribution, and has broad application prospects and economic benefits.

[0046] In some specific embodiments of the present invention, in step S1, the purity of the raw materials used is not less than 99.9 wt.%.

[0047] In some specific embodiments of the present invention, in step S2, the number of smelting is not less than 5 times, in order to improve the uniformity of the solder composition.

[0048] In some specific embodiments of the present invention, in step S2, vacuum melting is performed in an arc melting furnace, specifically comprising the following steps:

[0049] The raw materials prepared in step S1 are placed in a water-cooled copper crucible of an arc melting furnace. The arc furnace is evacuated and filled with high-purity argon as a protective gas, and then smelting is carried out. To ensure that the composition of the smelted solder block is uniform, electromagnetic stirring is used and the smelting is repeated for more than 5 times to obtain a solder alloy ingot after smelting.

[0050] In some specific embodiments of the present invention, in step S3, an inert gas is used as the atomizing medium, for example, high-purity argon is used as the atomizing medium; the pressure of the atomizing gas is 3.5-4.5 MPa, for example, it can be any point value among 3.5 MPa, 3.8 MPa, 4.0 MPa, 4.2 MPa, 4.5 MPa or a range value consisting of any two point values.

[0051] The third aspect of the present invention provides an application of the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder described in any of the aforementioned embodiments or the solder prepared by the preparation method of the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder described in any of the aforementioned embodiments in brazing of copper-based materials.

[0052] The method for brazing copper-based materials using Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder comprises the following steps:

[0053] The Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder is laid between two copper-based solders, and a pressure head is installed for vacuum brazing.

[0054] In some specific embodiments of the present invention, the vacuum brazing temperature is 700-750°C, and the holding time is 8-15 min; typically but not limitatively, for example, the vacuum brazing temperature can be any point value among 705°C, 715°C, 724°C, 735°C, 742°C, 750°C, or a range value consisting of any two point values; the holding time can be any point value among 8 min, 10 min, 12 min, 15 min, or a range value consisting of any two point values.

[0055] In some specific embodiments of the present invention, after vacuum brazing, the shear strength of the welded area is 235-300 MPa, the joint strength is high, and the joint has excellent mechanical properties.

[0056] In some specific embodiments of the present invention, after vacuum brazing, the resistivity of the welding area is 3.8-5.2μΩ·cm, for example, it can be any point value among 3.8μΩ·cm, 4.0μΩ·cm, 4.2μΩ·cm, 4.5μΩ·cm, 4.7μΩ·cm, 5.0μΩ·cm, and 5.2μΩ·cm, or a range value consisting of any two point values; the multi-principal element eutectic solder provided by the present invention has low resistivity, which can significantly reduce the contact resistance of the welding point and reduce the energy loss during current transmission; it can also avoid device performance degradation or failure caused by local overheating.

[0057] In some specific embodiments of the present invention, after vacuum brazing, the weld joint is heat treated at 250-350°C in an air atmosphere for 3-5 hours, and the resistivity of the weld area does not increase by more than 15%. For example, it can be any point value among 14.9%, 14%, 13%, 12%, 10.5%, 9.6%, 9%, or a range value consisting of any two point values, or other values ​​within the range; after high-temperature heat treatment, the resistivity of the weld area increases very little, showing excellent stability, which can reduce the performance degradation or failure of the device caused by local overheating due to the increase in resistivity during service.

[0058] The following describes some embodiments of the present invention in detail with reference to specific application examples. Unless otherwise specified, the raw materials used in the examples can be purchased from the market.

[0059] Example 1

[0060] A Ag-based multi-principal element eutectic solder 68.9 Al9Cu 7.6 In 9.7 Sm 2.5 Ti 2.3 (at.%), and its preparation method comprises the following steps:

[0061] S1. Ingredients: Ag (99.9wt.%), Al (99.999wt.%), Cu (99.95wt.%), In (99.9wt.%), Sm (99.9wt.%), and Ti (99.95wt.%) were prepared according to the above element ratios;

[0062] S2. Melting of master alloy: Place the raw materials according to the ratio in a water-cooled copper crucible of an arc melting furnace, and use a mechanical pump and a molecular pump to evacuate the arc furnace to a vacuum degree of 5.0×10 -3 After Pa, high-purity argon gas is filled as a protective atmosphere, and then smelting is carried out. In order to ensure that the composition of the molten solder block is uniform, electromagnetic stirring is used and the smelting is repeated 5 times to obtain a solder alloy ingot;

[0063] S3. Powder preparation: The smelted master alloy is placed in a quartz tube with a 0.4 mm micropore at the bottom and fixed in an induction coil. The furnace is then pumped to a high vacuum state (vacuum degree not less than 6.0×10 -3 Pa), and then filled with high-purity argon as a protective atmosphere. High-frequency induction heating technology was used to quickly melt the alloy. At the same time, high-purity argon was used as the atomizing medium, and gas atomization was performed at 760°C and a pressure of 3.8 MPa. After the atomization was completed, argon was slowly blown into the atomization chamber until the atmospheric pressure was restored. Subsequently, the Ag-based multi-principal element eutectic solder powder obtained after gas atomization was collected and processed.

[0064] The solder powder prepared by the above preparation method has uniform and concentrated particle size distribution, with an average particle size of about 38.7μm. Figure 1 ; Its liquidus temperature is 655℃.

[0065] Example 2

[0066] A Ag-based multi-principal element eutectic solder 70.5 Al 12 Cu 7.6 In 5.2 Sm 2.5 Ti 2.2 (at.%), and its preparation method comprises the following steps:

[0067] S1. Ingredients: Ag (99.9wt.%), Al (99.999wt.%), Cu (99.95wt.%), In (99.9wt.%), Sm (99.9wt.%), and Ti (99.95wt.%) were prepared according to the above element ratios;

[0068] S2. Melting of master alloy: Place the raw materials according to the ratio in a water-cooled copper crucible of an arc melting furnace, and use a mechanical pump and a molecular pump to evacuate the arc furnace to a vacuum degree of 5.0×10 -3 After Pa, high-purity argon gas is filled as a protective atmosphere, and then smelting is carried out. In order to ensure that the composition of the molten solder block is uniform, electromagnetic stirring is used and the smelting is repeated 5 times to obtain a solder alloy ingot;

[0069] S3. Powder preparation: The smelted master alloy is placed in a quartz tube with a 0.4 mm micropore at the bottom and fixed in an induction coil. The furnace is then pumped to a high vacuum state (vacuum degree not less than 6.0×10 -3 Pa), and then filled with high-purity argon as a protective atmosphere. High-frequency induction heating technology was used to quickly melt the alloy. At the same time, high-purity argon was used as the atomizing medium, and gas atomization was performed at 780°C and a pressure of 3.8 MPa. After the atomization was completed, argon was slowly blown into the atomization chamber until the atmospheric pressure was restored. Subsequently, the Ag-based multi-principal element eutectic solder powder obtained after gas atomization was collected and processed.

[0070] The solder powder prepared by the above preparation method has a uniform and concentrated particle size distribution, an average particle size of about 43.4 μm, and a liquidus temperature of about 674°C.

[0071] Example 3

[0072] A Ag-based multi-principal element eutectic solder 72 Al9Cu 9.5 In 4.85 Sm2Ti 2.65 (at.%), and its preparation method comprises the following steps:

[0073] S1. Ingredients: Ag (99.9wt.%), Al (99.999wt.%), Cu (99.95wt.%), In (99.9wt.%), Sm (99.9wt.%), and Ti (99.95wt.%) were prepared according to the above element ratios;

[0074] S2. Melting of master alloy: Place the raw materials according to the ratio in a water-cooled copper crucible of an arc melting furnace, and use a mechanical pump and a molecular pump to evacuate the arc furnace to a vacuum degree of 5.0×10 -3After Pa, high-purity argon gas is filled as a protective atmosphere, and then smelting is carried out. In order to ensure that the composition of the molten solder block is uniform, electromagnetic stirring is used and the smelting is repeated 5 times to obtain a solder alloy ingot;

[0075] S. Powder preparation: Place the smelted master alloy in a quartz tube with a 0.4 mm micropore at the bottom and fix it in an induction coil. Use a mechanical pump and a molecular pump to pump the furnace to a high vacuum state (vacuum degree not less than 6.0×10 - 3 Pa), and then filled with high-purity argon as a protective atmosphere. High-frequency induction heating technology was used to quickly melt the alloy. At the same time, high-purity argon was used as the atomizing medium, and gas atomization was performed at 790°C and a pressure of 3.8 MPa. After the atomization was completed, argon was slowly blown into the atomization chamber until the atmospheric pressure was restored. Subsequently, the Ag-based multi-principal element eutectic solder powder obtained after gas atomization was collected and processed.

[0076] The solder powder prepared by the above preparation method has a uniform and concentrated particle size distribution, an average particle size of about 44.7 μm, and a liquidus temperature of about 692°C.

[0077] Comparative Example 1

[0078] A Ag-based multi-principal element eutectic solder 81.1 Al9Cu 7.6 Ti 2.3 (at.%), and its preparation method comprises the following steps:

[0079] S1. Ingredients: Ag (99.9wt.%), Al (99.999wt.%), Cu (99.95wt.%), and Ti (99.95wt.%) were prepared according to the above element ratios;

[0080] S2. Melting of master alloy: Place the raw materials according to the ratio in a water-cooled copper crucible of an arc melting furnace, and use a mechanical pump and a molecular pump to evacuate the arc furnace to a vacuum degree of 5.0×10 -3 After Pa, high-purity argon gas is filled as a protective atmosphere, and then smelting is carried out. In order to ensure that the composition of the molten solder block is uniform, electromagnetic stirring is used and the smelting is repeated 5 times to obtain a solder alloy ingot;

[0081] S3. Powder preparation: The smelted master alloy is placed in a quartz tube with a 0.4 mm micropore at the bottom and fixed in an induction coil. The furnace is then pumped to a high vacuum state (vacuum degree not less than 6.0×10 -3Pa), and then filled with high-purity argon as a protective atmosphere. High-frequency induction heating technology is used to quickly melt the alloy. At the same time, high-purity argon is used as the atomizing medium, and gas atomization is performed at 890°C and a pressure of 3.8 MPa. After the atomization is completed, argon is slowly blown into the atomization chamber until the atmospheric pressure is restored. Subsequently, the Ag-based powder brazing material obtained after gas atomization is collected and processed.

[0082] The liquidus temperature of the solder powder prepared by the above preparation method is about 699°C.

[0083] Comparative Example 2

[0084] A Ag-based multi-principal element eutectic solder 68.9 Al9Cu 7.6 In 12.2 Ti 2.3 (at.%), and its preparation method comprises the following steps:

[0085] S1. Ingredients: Ag (99.9wt.%), Al (99.999wt.%), Cu (99.95wt.%), In (99.9wt.%), and Ti (99.95wt.%) were prepared according to the above element ratios;

[0086] S2. Melting of master alloy: Place the raw materials according to the ratio in a water-cooled copper crucible of an arc melting furnace, and use a mechanical pump and a molecular pump to evacuate the arc furnace to a vacuum degree of 5.0×10 -3 After Pa, high-purity argon gas is filled as a protective atmosphere, and then smelting is carried out. In order to ensure that the composition of the molten solder block is uniform, electromagnetic stirring is used and the smelting is repeated 5 times to obtain a solder alloy ingot;

[0087] S3. Powder preparation: The smelted master alloy is placed in a quartz tube with a 0.4 mm micropore at the bottom and fixed in an induction coil. The furnace is then pumped to a high vacuum state (vacuum degree not less than 6.0×10 -3 Pa), and then filled with high-purity argon as a protective atmosphere. High-frequency induction heating technology is used to quickly melt the alloy. At the same time, high-purity argon is used as the atomizing medium, and gas atomization is performed at 780°C and a pressure of 3.8 MPa. After the atomization is completed, argon is slowly blown into the atomization chamber until the atmospheric pressure is restored. Subsequently, the Ag-based powder brazing material obtained after gas atomization is collected and processed.

[0088] The liquidus temperature of the solder powder prepared by the above preparation method is about 640°C.

[0089] Comparative Example 3

[0090] A Ag-based multi-principal element eutectic solder 68.9 Al9Cu7.6 Sm 12.2 Ti 2.3 (at.%), and its preparation method comprises the following steps:

[0091] S1. Ingredients: Ag (99.9wt.%), Al (99.999wt.%), Cu (99.95wt.%), Sm (99.9wt.%), and Ti (99.95wt.%) were prepared according to the above element ratios;

[0092] S2. Melting of master alloy: Place the raw materials according to the ratio in a water-cooled copper crucible of an arc melting furnace, and use a mechanical pump and a molecular pump to evacuate the arc furnace to a vacuum degree of 5.0×10 -3 After Pa, high-purity argon gas is filled as a protective atmosphere, and then smelting is carried out. In order to ensure that the composition of the molten solder block is uniform, electromagnetic stirring is used and the smelting is repeated 5 times to obtain a solder alloy ingot;

[0093] S3. Powder preparation: The smelted master alloy is placed in a quartz tube with a 0.4 mm micropore at the bottom and fixed in an induction coil. The furnace is then pumped to a high vacuum state (vacuum degree not less than 6.0×10 -3 Pa), and then filled with high-purity argon as a protective atmosphere. High-frequency induction heating technology is used to quickly melt the alloy. At the same time, high-purity argon is used as the atomizing medium, and gas atomization is performed at 840°C and a pressure of 3.8 MPa. After the atomization is completed, argon is slowly blown into the atomization chamber until the atmospheric pressure is restored. Subsequently, the Ag-based powder brazing material obtained after gas atomization is collected and processed.

[0094] The liquidus temperature of the solder powder prepared by the above preparation method is about 726°C.

[0095] Test example

[0096] The Ag-based multi-principal element eutectic solders in the embodiments and comparative examples were respectively used to braze the copper-based materials. The brazing process was as follows:

[0097] Ag-based multi-principal eutectic solder powder was evenly spread between two Cu substrates, and then assembled with a pressure head and placed in a vacuum brazing furnace. The brazing process was as follows: keeping the temperature at the brazing temperature for 10 min and the vacuum degree was 1.0×10 -2 Pa. After brazing, cool to room temperature in the furnace.

[0098] (1) The welded joints of Examples 1-3 have uniform microstructure and high strength in the welded areas. The shear strength of each joint was tested according to the GB / T 11363-2008 brazing joint strength test method. The brazing temperature and shear strength test results are shown in Table 1.

[0099] Table 1

[0100]

[0101] (2) In order to evaluate the effect of oxidation on the resistivity of the welded joint during long-term service, the brazed joint was further heat treated at 300°C in air for 4 h. The resistivity of the welded area before and after heat treatment was tested according to GB / T 351-2019 Metal Material Resistivity Measurement Method. The test results are shown in Table 2.

[0102] Table 2

[0103]

[0104] As can be seen from the data in Table 2, after heat treatment, the resistivity increase in the weld area of ​​the welded joint obtained by brazing with the solder provided by the present invention is very small, less than 15%, which is much lower than that of the comparative example, showing excellent stability. This shows that the addition of In and Sm can reduce the additional resistivity increase during long-term service. In addition, as can be seen from the data in Example 1 and Comparative Examples 1-3, the use of In and Sm in combination has a better effect.

[0105] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. An Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder, characterized in that: Calculated by atomic percentage, it includes: Ag 68.5%-72.5%, Al 8.5%-12.5%, Cu 7.5%-10.8%, In 4.5%-10%, Sm 1.5%-3.0%, and Ti 2.0%-2.8%.

2. The Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder according to claim 1, characterized in that: The atomic content ratio of the In and Sm is 2-4.5:

1.

3. The Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder according to claim 1, characterized in that: The liquidus temperature of the solder is 650-700°C.

4. The Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder according to claim 1, characterized in that: The solder is in the form of powder, and the average particle size of the powder is 35-45 μm.

5. The method for preparing the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Ag, Al, Cu, In, Sm and Ti are mixed according to the formula ratio; S2. The raw materials prepared in step S1 are vacuum melted, electromagnetic stirring is used during the melting process, and the melting is repeated several times to obtain a solder alloy ingot; S3. The solder alloy ingot is subjected to vacuum induction melting, and after the solder alloy ingot is completely melted, gas atomization powdering is performed to obtain the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder.

6. The method for preparing the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder according to claim 5, characterized in that: Contains at least one of the following characteristics: (1) In step S1, the purity of the raw materials used is not less than 99.9 wt.%; (2) In step S2, the smelting is performed no less than 5 times; (3) In step S3, an inert gas is used as the atomizing medium, and the pressure of the atomizing gas is 3.5-4.5 MPa.

7. Use of the Ag-Al-Cu-In-Sm-Ti multi-principal-element eutectic solder according to any one of claims 1 to 4 or the solder prepared by the preparation method of the Ag-Al-Cu-In-Sm-Ti multi-principal-element eutectic solder according to claim 5 or 6 in brazing of copper-based materials.

8. The use according to claim 7, characterized in that The method for brazing copper-based materials using the Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder comprises the following steps: The Ag-Al-Cu-In-Sm-Ti multi-principal element eutectic solder is laid between two copper-based solders, a pressure head is installed, and vacuum brazing is performed.

9. The use according to claim 8, characterized in that The vacuum brazing temperature is 700-750° C., and the holding time is 8-15 minutes.

10. The use according to claim 8 or 9, characterized in that: Contains at least one of the following characteristics: (1) After vacuum brazing, the shear strength of the weld area is 235-300 MPa; (2) After the vacuum brazing, the resistivity of the welded area is 3.8-5.2 μΩ·cm; (3) After the vacuum brazing, the welded joint is heat treated at 250-350° C. for 3-5 hours in an air atmosphere, and the resistivity of the welded area does not increase by more than 15%.

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