A method for preparing a face-centered cubic solid solution layer solder joint containing multiple principal element alloys

Abstract

The present invention provides a method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer. The preparation method comprises: preparing Cu, Ni, and Ag in atomic ratios of 58-85% Cu, 7-20% Ag, and 8-22% Ni; then smelting, rolling, and cutting to produce a CuNiAg alloy plate. One end of the alloy plate is placed in AuSn20 solder, and another alloy plate is overlapped on top. The plate is then secured with polytetrafluoroethylene tape. The secured sample is brazed in a hydrogen furnace for 5 minutes, followed by a 15-minute brazing in a muffle furnace. To reduce the formation of voids during brazing, a counterweight is placed above the solder joint during brazing in the muffle furnace. The method achieves uniform weld thickness with minimal voids. A multi-principal alloy face-centered cubic solid solution layer is formed near the substrate to alleviate stress concentration, thereby improving solder joint strength. The method is simple and low-cost, making it suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of electronic welding manufacturing, in particular to a method for preparing a face-centered cubic solid solution layer solder joint containing a multi-principal element alloy. Background Art

[0002] With the rapid development of the electronics industry, electronic products are becoming increasingly digital and integrated, placing increasing demands on the performance of electronic components. Electronic packaging, as a key step in electronics manufacturing, significantly impacts the reliability and service life of electronic components. Soldering is a crucial technology within electronic packaging and is widely used in the electronics manufacturing industry, for example in microelectronic ceramic cap packaging, insulator welding between metal and ceramic caps, chip mounting, and the soldering of high-power laser semiconductor chips. Gold-tin eutectic solder, due to its excellent soldering properties, has been widely used. In recent years, with the introduction of environmental protection policies, the use of traditional lead-based solder has been declining, and demand for gold-tin solder has rapidly increased. Gold-tin eutectic alloy is currently the best solder with a melting point between 280°C and 360°C, replacing high-melting-point lead-based alloys. Although its application is significantly limited by its price and melting point, it is widely used in the electronics manufacturing industry due to its excellent creep and fatigue resistance, good electrical and thermal conductivity, and ease of soldering and brazing without the need for flux.

[0003] During the gold-tin soldering process, the liquid gold-tin solder reacts with the substrate, forming intermetallic compounds at the solder / substrate interface. However, due to the hard and brittle nature of intermetallic compounds and the fact that stress concentration is easily generated near the substrate, cracks are easily generated and propagated in the intermetallic compound layer under load. Therefore, a large number of researchers at home and abroad have used a series of methods to improve the strength of solder joints. Existing methods mainly focus on optimizing solder composition, improving welding processes, and improving welding equipment. Solder optimization mainly involves adding alloying elements to the solder. Alloying elements can inhibit the formation and growth of certain intermetallic compounds, thereby reducing the damage of intermetallic compounds to the solder joint. In terms of welding process, the welding time and temperature are changed or an external field is introduced. These methods can reduce the formation of intermetallic compounds to a certain extent, thereby improving the strength of the solder joint.

[0004] However, despite a range of methods to optimize the composition, morphology, and distribution of intermetallic compounds, solder joints still exhibit relatively low shear strength. This is because, regardless of process optimization, the hard and brittle nature of the intermetallic compounds produced at the solder interface remains unchanged. Therefore, it is difficult to significantly increase the strength of solder joints made with gold-tin solder, making it difficult to meet industrial demands and severely restricting its application in electronic packaging.

[0005] The existing method for preparing solder joints containing multi-principal alloy face-centered cubic solid solution layers is to prepare a substrate using an equiatomic ratio of copper, nickel, and silver metals through arc melting and rolling. The substrates are then soldered together using gold-tin solder at a welding temperature of 350°C, achieving a solder joint shear strength of 81 MPa. Alternatively, when a substrate with a copper-nickel atomic ratio of 4:1, prepared by arc melting, is soldered using AuSn29, a multi-principal alloy face-centered cubic solid solution layer can also be obtained, with a solder joint shear strength of approximately 93 MPa. Summary of the Invention

[0006] On the basis of the existing technology, in order to explore a product with higher solder joint shear strength, the present invention is obtained by further optimizing the substrate components and coordinating the welding process.

[0007] The present invention adds a certain amount of nickel, silver and other elements to the copper substrate. After a period of welding, the obtained solder joint contains a multi-principal alloy face-centered cubic solid solution layer, and its shear strength is improved. The method is simple and low-cost, and can improve the reliability of the solder joint.

[0008] The present invention provides a method for preparing a solder joint containing a multi-principal element alloy face-centered cubic solid solution layer, comprising the following steps:

[0009] Step 1 Ingredients

[0010] According to the atomic ratio; Cu: 58-85%, Ag: 7-20%, Ni: 8-22%, preferably Cu: 80-82%, Ag: 10-12%, Ni: 8-9%, more preferably Cu: 81%, Ag: 11%, Ni: 8%, with Cu, Ni, Ag;

[0011] Step 2: Melting and Casting

[0012] Put the prepared metal materials into a smelting furnace for smelting to obtain ingots;

[0013] Step 3: Squeeze

[0014] The ingot is extruded with a single deformation of 10-15% to form a plate with a thickness of 1 to 1.5 mm; Step 4: Cutting

[0015] Cut the plate obtained in step 3 to obtain metal strips of a set size;

[0016] Step 5: Pre-welding treatment

[0017] Grinding, polishing, and cleaning to obtain a metal strip with a clean surface free of impurities; placing AuSn20 solder of a set size on one side of the metal strip, then overlapping another metal strip on top, bundling and fixing them to obtain a sample to be welded;

[0018] Step 6: Soldering

[0019] The sample to be welded obtained in step 5 is placed in a hydrogen furnace for welding at a welding temperature of 350-360°C and a welding time of 5-8 minutes; then the sample welded in the hydrogen furnace is placed in a muffle furnace for welding for 15-20 minutes at a muffle furnace temperature of 330-350°C.

[0020] As a preferred embodiment, the present invention provides a method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer, wherein the melting furnace is an arc melting furnace.

[0021] The present invention provides a method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer.

[0022] Put the prepared metal material into a quartz tube, introduce argon into the quartz tube, and then evacuate it to a vacuum state. Repeat this process at least three times to expel the air. Then, seal the quartz tube containing the metal material. After sealing, the quartz tube contains argon.

[0023] Turn on the induction heating power supply, ensure that the cooling system operates normally, modulate the current to 180A, then place the quartz tube containing the sample in the center of the induction coil, and increase the current to 240A after the metal sample is burned red, and the metal sample can be melted; after smelting for 3 minutes, bury the sample end of the quartz tube in the sand to cool naturally, and take out the sample after cooling is completed; and obtain an ingot. Of course, its smelting process can also be used in the present invention, but different smelting processes have a certain effect on the strength of the final weld. For example, put the prepared metal material into an arc melting furnace, first turn on the mechanical pump to extract the vacuum, and then introduce argon gas. Repeat the operation at least 2 times, and then start the arc. After the arc is started, turn the current to 300A and smelt for 15 seconds. To ensure uniform smelting, use a robotic arm to turn the sample over and repeat the operation 5 times. After smelting is completed, cool it in the furnace to obtain a button ingot. During the specific operation of arc melting, vacuum is evacuated until the furnace pressure drops to less than or equal to 10000Pa, and then the argon valve is opened to flush argon gas until the pressure in the furnace is slightly negative (the reading on the meter is -0.02-0, unit MPa)

[0024] The present invention provides a method for preparing a solder joint containing a multi-principal element alloy face-centered cubic solid solution layer. In step four, the plate obtained in step three is cut into metal strips of 33 mm×5 mm.

[0025] The present invention provides a method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer. In step five, the metal strip is sanded with 800#, 1200#, 1500#, and 2000# sandpaper to remove the surface oxide film. After sanding, the strip is polished and ultrasonically cleaned to obtain a clean, impurity-free metal strip. Preferably, the clean, impurity-free metal strip has a surface roughness of Ra = 0.7 to 0.9 μm.

[0026] The present invention provides a method for preparing a weld joint containing a multi-principal alloy face-centered cubic solid solution layer. In step five, the sample to be welded is secured with polytetrafluoroethylene tape. This ensures uniform weld size, minimal voids, and minimizes slippage during welding.

[0027] The present invention discloses a method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer. During soldering in step six, a metal block is applied above the solder joint to reduce voids. When the metal strip measures 33 mm x 5 mm and the AuSn20 solder measures 3 mm x 5 mm, the mass of the applied metal block can be 70-80 g. In industrial applications, the mass of the applied metal block can be adjusted based on actual conditions.

[0028] When welding in a hydrogen furnace, introducing a certain amount of hydrogen prevents oxidation of the substrate and solder during the welding process, thereby ensuring high fluidity of the liquid solder, allowing it to wet the substrate well and guaranteeing weld quality. When subsequently welding in a muffle furnace, counterweights at the same temperature can be added to reduce voids without affecting the interface products.

[0029] The process designed by the present invention is suitable for preparing high-strength solder joints. The strength of the solder joints prepared is higher than that of similar technologies, and the cost is lower.

[0030] The present invention adds a certain amount of alloying elements such as Ni and Ag to the substrate to obtain a solder joint having a face-centered cubic solid solution layer containing a multi-principal alloy, and its shear strength is improved. The advantages of the present invention are:

[0031] 1. The composition of the cast substrate is uniform and there is no segregation.

[0032] 2. The weld thickness is uniform and there are few holes, which reduces the impact of holes on joint strength.

[0033] 3. The obtained solder joint has a multi-principal alloy face-centered cubic solid solution layer near the substrate. This solid solution layer can relieve stress concentration through plastic deformation, thereby improving the strength of the solder joint. After optimization, the shear strength of the obtained solder joint can reach 105~107MPa.

[0034] 4. The process is simple and the product has excellent performance; the production process of the present invention is simple and does not require complex welding equipment. At the same time, the performance of the product obtained by the present invention is better than that of the product obtained by the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the process of a face-centered cubic solid solution layer containing multiple principal element alloys according to the present invention.

[0036] Figure 2 This is the macroscopic morphology of the plate obtained after ingot extrusion in Example 1.

[0037] Figure 3 This is a SEM image of the substrate obtained in Example 1.

[0038] Figure 4 This is the macroscopic morphology of the welding sample obtained in Example 1.

[0039] Figure 5 This is the EBSD test result of the solder joint in Example 1.

[0040] Figure 6 The SEM test results of the solder joints in Example 1 are shown.

[0041] Figure 7 This is the XRD test result of the solder joint in Example 1.

[0042] Figure 8 The tensile test results of the welded sample in Example 1 are shown.

[0043] Figure 9 The SEM test results of the solder joints in Example 2 are shown.

[0044] Figure 10 The following are the test results of the tensile test of the welded sample in Example 2.

[0045] Figure 11 The SEM test results of the solder joints in Example 3 are shown.

[0046] Figure 12 These are the tensile test results of the welded samples in Example 3. DETAILED DESCRIPTION

[0047] Example 1

[0048] 1) Using an electronic balance, prepare the metal raw materials of Cu, Ni, and Ag according to the atomic ratio: Cu: 81%, Ag: 11%, Ni: 8%;

[0049] 2) Melting and Casting: Place the prepared metal material into a quartz tube and perform a purge operation first: introduce argon into the quartz tube, then evacuate it to a vacuum, repeat this three times to expel the air. After the final purge, introduce a certain amount of argon into the quartz tube and close the argon valve. Use a mixture of propane and oxygen to seal the quartz tube with a certain amount of argon remaining. Turn on the induction heating power supply, ensure the normal operation of the cooling system, modulate the current to 180A, and then place the quartz tube containing the sample in the center of the induction coil. After the metal sample is burned red, increase the current to 240A, and the metal sample will melt. After 3 minutes of smelting, bury the sample end of the quartz tube in sand to cool naturally. After cooling, remove the sample.

[0050] 3) Extrusion: The smelted button ingot is extruded with a single deformation of about 15% to form a plate with a thickness of about 1.25 mm.

[0051] 4) Cutting The plate obtained in step 3 is cut into metal strips of 33 mm×5 mm.

[0052] 5) Pre-welding Treatment: The metal strips obtained in step 4 were sanded with 800#, 1200#, 1500#, and 2000# sandpaper to remove the surface oxide film. After sanding, they were polished and ultrasonically cleaned to obtain a clean, impurity-free metal strip with a surface roughness of Ra = 0.8 μm. A 3 mm × 5 mm piece of AuSn20 solder was placed on one side of the metal strip, and another metal strip was placed on top. The strips were then secured with polytetrafluoroethylene tape to obtain the sample to be welded.

[0053] 6) Welding: The samples obtained in step 5 were welded in a hydrogen furnace at a temperature of 350°C for 5 minutes. The hydrogen furnace-welded samples were then welded in a muffle furnace at 350°C for 15 minutes. During welding, a 75g metal block was placed above the weld point to reduce voids.

[0054] 7) Product performance. The obtained solder joints have few holes and uniform weld size. They contain a face-centered cubic solid solution layer composed of four alloying elements: Au, Sn, Cu, and Ag near the substrate. The solder joints have a high shear strength of up to 106.6 MPa.

[0055] Example 2

[0056] 1) Using an electronic balance, prepare the metal raw materials of Cu, Ni, and Ag according to the atomic ratio: Cu: 71%, Ag: 7%, Ni: 22%;

[0057] 2) Melting: Place the prepared metal material into an arc melting furnace. First, activate the mechanical pump to draw a vacuum, then introduce argon. Repeat this operation three times. Then, activate the molecular pump and evacuate the furnace until the pressure drops to less than or equal to 10,000 Pa. Then, open the argon valve and inject argon until the furnace pressure reaches a slightly negative state (the meter reads -0.02-0, in MPa). Start the arc. After starting the arc, increase the current to 300 A and melt for 15 seconds. To ensure uniform melting, use a robotic arm to flip the sample over and repeat this operation five times. After melting, cool the sample in the furnace to obtain a button ingot.

[0058] 3) Extrusion The smelted button ingot is extruded with a single deformation of about 15% to form a plate with a thickness of 1.25 mm.

[0059] 4) Cutting The plate obtained in step 3 is cut into metal strips of 33 mm×5 mm.

[0060] 5) Pre-welding Treatment: The metal strips obtained in step 4 were sanded with 800#, 1200#, 1500#, and 2000# sandpaper to remove the surface oxide film. After sanding, they were polished and ultrasonically cleaned to obtain a clean, impurity-free metal strip with a surface roughness of Ra = 0.8 μm. A 3 mm × 5 mm piece of AuSn20 solder was placed on one side of the metal strip, and another metal strip was placed on top. The strips were then secured with polytetrafluoroethylene tape to obtain the sample to be welded.

[0061] 6) Welding: The samples obtained in step 5 were welded in a hydrogen furnace at a temperature of 350°C for 5 minutes. The hydrogen furnace-welded samples were then welded in a muffle furnace at 350°C for 15 minutes. During welding, a 75g metal block was placed above the weld point to reduce voids.

[0062] 7) The obtained welds have few holes, uniform weld size and high shear strength of about 76MPa.

[0063] Example 3

[0064] 1) Using an electronic balance, prepare the metal raw materials of Cu, Ni, and Ag according to the atomic ratio: Cu: 61%, Ag: 20%, Ni: 19%;

[0065] 2) Melting: Place the prepared metal material into an arc melting furnace. First, activate the mechanical pump to draw a vacuum, then introduce argon. Repeat this operation three times. Then, activate the molecular pump and evacuate the furnace until the pressure drops to less than or equal to 10,000 Pa. Then, open the argon valve and inject argon until the furnace pressure reaches a slightly negative state (the meter reads -0.02-0, in MPa). Start the arc. After starting the arc, increase the current to 300 A and melt for 15 seconds. To ensure uniform melting, use a robotic arm to flip the sample over and repeat this operation five times. After melting, cool the sample in the furnace to obtain a button ingot.

[0066] 3) Extrusion The smelted button ingot is extruded with a single deformation of about 15% to form a plate with a thickness of 1.25 mm.

[0067] 4) Cutting The plate obtained in step 3 is cut into metal strips of 33 mm×5 mm.

[0068] 5) Pre-welding Treatment: The metal strips obtained in step 4 were sanded with 800#, 1200#, 1500#, and 2000# sandpaper to remove the surface oxide film. After sanding, they were polished and ultrasonically cleaned to obtain a clean, impurity-free metal strip with a surface roughness of Ra = 0.8 μm. A 3 mm × 5 mm piece of AuSn20 solder was placed on one side of the metal strip, and another metal strip was placed on top. The strips were then secured with polytetrafluoroethylene tape to obtain the sample to be welded.

[0069] 6) Welding: The samples obtained in step 5 were welded in a hydrogen furnace at a temperature of 350°C for 5 minutes. The hydrogen furnace-welded samples were then welded in a muffle furnace at 350°C for 15 minutes. During welding, a 75g metal block was placed above the weld point to reduce voids.

[0070] 7) The product performance is that the welds obtained have few holes, uniform weld size, high strength, and a shear strength of about 89MPa.

[0071] Comparative Example 1

[0072] 1) Use an electronic balance to prepare Cu, Ni, and Ag according to the atomic ratio of Cu:Ni:Ag=1:1:1;

[0073] 2) Melting and Casting: Place the prepared metal materials into the arc melting furnace, first open the mechanical pump to draw vacuum, then introduce argon, repeat the operation 3 times, then open the molecular pump and draw the furnace to a vacuum degree of 10 -5 , then open the argon valve to -0.02. After arcing, increase the current to 300A and melt for 15 seconds. To ensure uniform melting, use a robotic arm to flip the sample over and repeat this operation five times. After melting, cool the furnace to obtain a button ingot.

[0074] 3) Extrusion The smelted button ingot is extruded with a single deformation of about 15% to form a plate with a thickness of 1.25 mm.

[0075] 4) Cutting The plate obtained in step 3 is cut into metal strips of 33 mm×5 mm.

[0076] 5) Pre-welding Treatment: Use 800#, 1200#, 1500#, and 2000# sandpaper to polish the metal strips obtained in step 4 to remove the surface oxide film. After polishing, perform ultrasonic cleaning to obtain a clean, impurity-free metal strip. Place 3mm×5mm AuSn20 solder on one side of the metal strip, then overlap another metal strip on top. Secure the strips with Teflon tape to obtain the sample to be welded.

[0077] 6) Welding The sample to be welded obtained in step 5 is placed in an argon furnace for welding at a welding temperature of 350° C. and a welding time of 20 min.

[0078] 7) Product performance: The obtained solder joints have few voids and uniform weld size. They contain a face-centered cubic solid solution layer composed of five alloying elements: Au, Sn, Cu, Ni, and Ag near the substrate. However, the shear strength of the solder joints is only 81 MPa.

[0079] Comparative Example 2

[0080] Preparation of face-centered cubic solid solution solder joints containing four alloying elements: Au, Sn, Cu, and Ni

[0081] 1) Use an electronic balance to mix Cu and Ni according to the atomic ratio of Cu:Ni=4:1;

[0082] 2) Melting and Casting: Place the prepared metal materials into the arc melting furnace, first open the mechanical pump to draw vacuum, then introduce argon, repeat the operation 3 times, then open the molecular pump and draw the furnace to a vacuum degree of 10 -5 , then open the argon valve to -0.02. After arcing, increase the current to 300A and melt for 15 seconds. To ensure uniform melting, use a robotic arm to flip the sample over and repeat this operation five times. After melting, cool the furnace to obtain a button ingot.

[0083] 3) Extrusion: The smelted button ingot is extruded with a single deformation of about 15% to form a plate with a thickness of 1 to 1.5 mm.

[0084] 4) Cutting The plate obtained in step 3 is cut into metal strips of 33 mm×5 mm.

[0085] 5) Pre-welding Treatment: Use 800#, 1200#, 1500#, and 2000# sandpaper to polish the metal strips obtained in step 4 to remove the surface oxide film. After polishing, perform ultrasonic cleaning to obtain a clean, impurity-free metal strip. Place 3mm×5mm AuSn29 solder on one side of the metal strip, then overlap another metal strip on top. Secure the strips with Teflon tape to obtain the sample to be welded.

[0086] 6) Welding: The sample to be welded obtained in step 5 was placed in an argon furnace for welding at a temperature of 350° C. and a welding time of 20 min. During welding, a 75 g metal block was applied above the weld point to reduce holes.

[0087] 7) Product performance: The obtained solder joints have few holes and uniform weld size. They contain a face-centered cubic solid solution layer composed of four alloying elements: Au, Sn, Cu, and Ni near the substrate. The solder joint strength is 93MPa.

[0088] Comparative Example 3

[0089] 1) Use an electronic balance to mix Cu and Ni according to the atomic ratio of Cu:Ni=2:3;

[0090] 2) Melting and Casting: Place the prepared metal material into a quartz tube and perform a purge operation first: introduce argon into the quartz tube, then evacuate it to a vacuum, repeat this three times to expel the air. After the final purge, introduce a certain amount of argon into the quartz tube and close the argon valve. Use a mixture of propane and oxygen to seal the quartz tube with a certain amount of argon remaining. Turn on the induction heating power supply, ensure the normal operation of the cooling system, modulate the current to 180A, and then place the quartz tube containing the sample in the center of the induction coil. After the metal sample is burned red, increase the current to 240A, and the metal sample will melt. After 3 minutes of smelting, bury the sample end of the quartz tube in sand to cool naturally. After cooling, remove the sample.

[0091] 3) Extrusion: The smelted button ingot is extruded with a single deformation of about 15% to form a plate with a thickness of 1 to 1.5 mm.

[0092] 4) Cutting The plate obtained in step 3 is cut into metal strips of 33 mm×5 mm.

[0093] 5) Pre-welding Treatment: Use 800#, 1200#, 1500#, and 2000# sandpaper to polish the metal strips obtained in step 4 to remove the surface oxide film. After polishing, perform ultrasonic cleaning to obtain a clean, impurity-free metal strip. Place 3mm×5mm AuSn29 solder on one side of the metal strip, then overlap another metal strip on top. Secure the strips with Teflon tape to obtain the sample to be welded.

[0094] 6) Welding The sample to be welded obtained in step 5 is placed in an argon furnace for welding at a welding temperature of 350° C. and a welding time of 10 min.

[0095] 7) Product Performance: The obtained solder joints have few holes and uniform weld size. They contain a face-centered cubic solid solution layer composed of four alloying elements: Au, Sn, Cu, and Ni near the substrate, and the solder joint strength is 62MPa.

[0096] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer, characterized in that: The steps include: Step 1 Ingredients According to the atomic ratio; Cu: 80~82%, Ag: 10~12%, Ni: 8~9%, Cu, Ni, Ag are matched; Step 2: Melting and Casting Put the prepared metal materials into a smelting furnace for smelting to obtain ingots; Step 3: Squeeze The ingot is extruded with a single deformation of 10-15% to form a plate with a thickness of 1-1.5 mm; Step 4: Cutting Cut the plate obtained in step 3 to obtain metal strips of a set size; Step 5: Pre-welding treatment Grinding, polishing, and cleaning to obtain a metal strip with a clean surface free of impurities; placing AuSn20 solder of a set size on one side of the metal strip, then overlapping another metal strip on top, bundling and fixing them to obtain a sample to be welded; Step 6: Soldering The sample to be welded obtained in step 5 is placed in a hydrogen furnace for welding at a welding temperature of 350-360°C and a welding time of 5-8 minutes; then the sample welded in the hydrogen furnace is placed in a muffle furnace for welding for 15-20 minutes at a muffle furnace temperature of 330-350°C.

2. The method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer according to claim 1, characterized in that: In step 1, Cu, Ni, and Ag are prepared according to the atomic ratio of Cu: 81%, Ag: 11%, and Ni: 8%.

3. The method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer according to claim 1, characterized in that: Place the prepared metal material into a quartz tube, introduce argon into the quartz tube, and then evacuate it to a vacuum, repeat at least 3 times to expel the air, and then seal the quartz tube containing the metal material; after sealing, the quartz tube contains argon; turn on the induction heating power supply to ensure that the cooling system operates normally, modulate the current to 180A, and then place the quartz tube containing the sample in the center of the induction coil. After the metal sample is burned red, increase the current to 240A, and the metal sample can be melted; after smelting for 3 minutes, bury the sample end of the quartz tube in sand to cool naturally, and take out the sample after cooling is completed to obtain an ingot.

4. The method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer according to claim 1, characterized in that: Put the prepared metal material into the arc melting furnace, first turn on the mechanical pump to draw vacuum, then introduce argon, repeat the operation at least 2 times, start the arc, after arcing, turn the current to 300A, and melt for 15 seconds. To ensure uniform melting, use a mechanical arm to turn the sample over and repeat the operation 5 times; after melting is completed, cool it with the furnace to obtain button ingots; when vacuuming, evacuate until the furnace pressure drops to less than or equal to 1000Pa, and when filling with argon, fill it until the pressure in the furnace is slightly negative, at this time the reading on the meter is -0.02-0, unit MPa.

5. The method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer according to claim 1, characterized in that: In step 5, the surface roughness of the clean metal strip without impurities is Ra=0.7~0.9μm.

6. The method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer according to claim 1, characterized in that: In step five, the metal strip is sanded with 800#, 1200#, 1500# and 2000# sandpaper to remove the surface oxide film. After sanding, it is polished and ultrasonically cleaned to obtain a metal strip with a clean surface and no impurities.

7. The method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer according to claim 1, characterized in that: In step five, the samples are bundled and fixed with polytetrafluoroethylene tape to obtain the samples to be welded.

8. The method for preparing a solder joint containing a multi-principal alloy face-centered cubic solid solution layer according to claim 1, characterized in that: During soldering in step six, a metal block is applied above the solder joint to reduce voids. When the size of the metal strip is 33 mm × 5 mm and the size of the AuSn20 solder is 3 mm × 5 mm, the mass of the applied metal block is 70-80 g.

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