High-temperature-resistant welding joint and welding process

Abstract

The invention provides a high-temperature-resistant welding joint and a welding process, the high-temperature-resistant welding joint comprises a first connecting part, a middle connecting part and a second connecting part, the middle connecting part is located between the first connecting part and the second connecting part and is used for connecting the first connecting part and the second connecting part, the first connecting part is made of pure copper, and the second connecting part is made of pure copper. The middle connecting part is made of metal zinc, the third connecting part is made of pure copper, the middle connecting part is connected with the first connecting part and the second connecting part respectively to form a first interface and a second interface, at least one continuous intermetallic compound layer is formed on each of the first interface and the second interface, and the intermetallic compound layers are arranged between the first interface and the second interface. And the component of the intermetallic compound layer comprises Cu5Zn8.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a high-temperature-resistant welding joint and a welding process. BACKGROUND

[0002] At present, electronic products are developing towards miniaturization and integration, which gradually increases the density of micro-welding points on chips, and the miniaturization and reliability of the welding points are increasingly required.

[0003] Most of the existing micro-welding points contain tin, for example, the patent application (CN108615689A) of Harbin University of Science and Technology discloses a preparation method of a full Cu3Sn compound joint for power device packaging, and the patent application (CN107058956A) of Xiamen University discloses a rapid manufacturing method of a copper six tin five (Cu6Sn5) full IMC micro-bump. In the above-mentioned solutions, due to the low melting point of tin (the melting point of tin is 232℃), the excess reaction of tin leads to insufficient heat resistance of the welding point, and the use of flux in the welding process will cause welding porosity and flux residue, and the steps of the above-mentioned preparation process are complicated and the cost is high. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a high-temperature-resistant welding joint and a welding process. The low-temperature preparation of the copper-copper high-temperature welding structure is realized by the hot pressing process, the welding time is short, the welding temperature is low, the welding strength is high, the preparation process is simple, the material cost is low, and the welding process using the welding joint is simple to operate, without the need for complex welding equipment, and greatly improves the production efficiency.

[0005] The first aspect of the present application provides a high-temperature-resistant welding joint, comprising a first connecting part, an intermediate connecting part and a second connecting part, the intermediate connecting part is located between the first connecting part and the second connecting part for connecting the first connecting part and the second connecting part, wherein the material of the first connecting part is pure copper, the material of the intermediate connecting part is metal zinc, and the material of the third connecting part is pure copper, the intermediate connecting part and the first connecting part are connected to form a first interface, the intermediate connecting part and the second connecting part are connected to form a second interface, at least one continuous intermetallic compound layer is formed on the first interface and the second interface, the composition of the intermetallic compound layer includes Cu5Zn8, and the thickness of the intermetallic compound layer is 4.22μm-20.64μm.

[0006] In any embodiment of the present application, the intermediate connecting part and the first interface are formed by spraying the molten metal Zn onto the first connecting part, and the second interface is formed by welding the intermediate connecting part and the second connecting part together by ultrasonic auxiliary technology and hot pressing process, and the thickness of the intermediate connecting part is 10μm-100μm.

[0007] In any embodiment of the present application, the first interface layer and the second interface layer are welded together by the combined action of the ultrasonic auxiliary technology and the hot pressing process, wherein the second connecting part is used to directly receive the pressure applied by the ultrasonic auxiliary equipment.

[0008] In any embodiment of the present application, on the first interface, the thickness of the Cu5Zn8 layer is 9.75 μm to 11.13 μm, and the thickness of the CuZn4 layer is 3.33 μm to 4.05 μm; on the second interface, the thickness of the Cu5Zn8 layer is 10.74 μm to 11.65 μm, and the thickness of the CuZn4 layer is 3.84 μm to 4.05 μm.

[0009] In any embodiment of the present application, the intermetallic compound layer is one layer, and the composition of the intermetallic compound layer is Cu5Zn8.

[0010] Optionally, the thickness of the Cu5Zn8 layer is 5 μm to 10 μm.

[0011] In any embodiment of the present application, the intermetallic compound layer is two layers, and the intermetallic compound layer is two layers, wherein the intermetallic compound layer on the side close to the intermediate connecting part on the interface is a CuZn4 layer, and the intermetallic compound layer on the side close to the first connecting part and the second connecting part is a Cu5Zn8 layer.

[0012] In any embodiment of the present application, the thickness of the Cu5Zn8 layer is 2.75 μm to 15.22 μm, and the thickness of the CuZn4 layer is 1.47 μm to 5.42 μm.

[0013] Optionally, the thickness of the Cu5Zn8 layer is 6.41 μm to 11.65 μm, and the thickness of the CuZn4 layer is 2.19 μm to 4.59 μm.

[0014] The second aspect of the present application provides a welding process for preparing the high-temperature-resistant welded joint described above, comprising the following steps:

[0015] (1) selecting pure copper as the first connecting part, and sandblasting the pure copper;

[0016] (2) using a hot zinc spraying device to heat zinc wire to a high temperature, and spraying the molten zinc liquid to the surface of the first connecting part through compressed air;

[0017] (3) after the spraying is completed, storing the zinc coating at a constant temperature, the storage temperature is 80°C to 100°C, and the duration is 30 min to 60 min, so as to ensure that the zinc coating uniformly cools and solidifies on the surface of the first connecting part to form an intermediate connecting part and a first interface, and the intermediate connecting part is a zinc coating layer with a thickness of 10 to 100 μm;

[0018] (4) Put the sprayed first connecting part into the clamp, and then put the second connecting part with the welding surface facing the galvanized layer into the clamp, fix the clamp on the workbench, start the joining device during the welding process, start the ultrasonic device when the specified temperature is reached, and perform ultrasonic-assisted welding, stop the ultrasonic device after the welding time required by the process is reached, and continue to apply pressure to the base material until the welding is completed.

[0019] The third aspect of the present application provides a welding process for preparing the high-temperature-resistant welded joint described above, comprising the following steps:

[0020] (1) Select a first connecting part and a second connecting part, polish the surfaces to be welded of the first connecting part and the second connecting part, clean them with ultrasonic waves, and then dry them;

[0021] (2) Put the first connecting part into the clamp, fill in the intermediate connecting part, then put the second connecting part on the intermediate connecting part, and finally place the clamp on the heating table;

[0022] (3) Adjust the position of the ultrasonic generator, press the ultrasonic transducer of the ultrasonic generator on the second connecting part, and apply a certain pressure, start the ultrasonic generator after the heating table reaches a welding temperature of 225℃ to 325℃, perform ultrasonic-assisted welding, stop the ultrasonic generator after the welding time is reached, continue to apply pressure to the second connecting part for a certain period of time, and obtain a high-temperature-resistant welded joint.

[0023] In any embodiment of the present application, in step (3), the welding temperature is 265℃ to 285℃, the ultrasonic generator is a longitudinal ultrasonic generator, the frequency of the ultrasonic wave is set to 20kHz, the ultrasonic power is 300w to 600w, the ultrasonic-assisted welding time is 5s to 10s, and the pressure is 6MPa to 10MPa; the total welding time is 3min to 5min.

[0024] Beneficial technical effects:

[0025] 1. The welded joint prepared by the present application has good high-temperature resistance and high shear strength, and can meet the welding requirements of most electronic micro devices.

[0026] 2. By directly spraying a Zn layer on the surface of the Cu substrate, the Zn layer not only serves as a protective coating, but also acts as a filler metal during welding, reducing the dependence on external filler metal and simplifying the welding process. When welding, no flux is needed, which not only saves cost and reduces defects such as slag inclusion caused by the residue of the flux at the welding point, but also is environmentally friendly.

[0027] 3. The combination of ultrasonic and pressure technology used in the present application has a simple device structure, and the oscillation of the ultrasonic generator can break the oxide film of the base material to achieve low-temperature interconnection, the welding temperature can be lower than that of ordinary reflow soldering, and the heating energy can be saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the working principle of the ultrasonic welding equipment for this application;

[0029] Figure 2 The overall morphology of the Cu / Zn / Cu joint welds of Examples 1 to 6 of the present application is shown;

[0030] Figure 3 The Cu substrate prepared in Examples 6 and 7 of the present application;

[0031] Figures 4(a) to 4(b) This is the EDS image of the weld of the weld joint of Example 6 of the present application;

[0032] Figures 5(a) to 5(b) This is the EDS image of the weld of the weld joint in Example 7 of this application.

[0033] In the attached figure:

[0034] 1. Ultrasonic vibrator; 2. Second connecting part; 3. Intermediate connecting part; 4. First connecting part; 5. Clamp; 6. Heating platform. DETAILED DESCRIPTION

[0035] The following describes in detail, with appropriate reference to the accompanying drawings, embodiments of the present application's welded joint and welding process for preparing high-temperature-resistant solder joints. However, unnecessary detailed descriptions may be omitted, such as detailed descriptions of well-known matters or repeated descriptions of substantially identical structures, to avoid unnecessary tedium and facilitate understanding by those skilled in the art.

[0036] In one embodiment of the present application, the present application proposes a method for preparing a high-temperature resistant welding joint, comprising a first connecting part, an intermediate connecting part and a second connecting part, wherein the intermediate connecting part is located between the first connecting part and the second connecting part for connecting the first connecting part and the second connecting part, wherein the first connecting part is made of pure copper, the intermediate connecting part is made of metallic zinc, and the third connecting part is made of pure copper, the intermediate connecting part is connected to the first connecting part to form a first interface, and the intermediate connecting part is connected to the second connecting part to form a second interface, and at least one continuous intermetallic compound layer is formed on both the first interface and the second interface, and the components of the intermetallic compound layer include Cu5Zn8.

[0037] The weld morphology of the Cu / Zn / Cu joint using this composition is good, and the overall weld consistency is good. Continuous intermetallic compounds are formed on the first interface and the second interface, and no obvious defects or cracks are observed at the interface.

[0038] In some embodiments, the intermediate connection part and the first interface are formed by spraying metal Zn onto the first connection part after melting, and the second interface is formed by welding the intermediate connection part and the second connection part together through ultrasonic assisted technology and hot pressing process, and the thickness of the intermediate connection part is 10μm to 100μm.

[0039] Specifically, the first connecting part is a Cu substrate. Sandblasting gives the Cu substrate a high surface roughness, allowing the Zn coating to adhere evenly to the Cu substrate, improving the bonding strength between the Zn layer and the copper. Ultrasonic-assisted technology is introduced to allow the Zn layer to diffuse more evenly during welding and fill the weld gap, effectively improving the uniformity and strength of the weld. This solution combines thermal zinc spraying with ultrasonic and pressurized technology to produce welded joints with fewer defects and high quality.

[0040] In some embodiments, the first interface layer and the second interface layer are welded together by ultrasonic-assisted technology and hot pressing process, wherein the second connection portion is used to directly bear the pressure applied by the ultrasonic-assisted equipment.

[0041] The welding method that combines ultrasonic assisted technology and pressurized technology enables the Zn layer to diffuse more evenly and fill the welding gap during the welding process, effectively improving the uniformity and strength of the weld.

[0042] In some embodiments, the thickness of the intermetallic compound layer is 4.22 μm to 20.64 μm.

[0043] Preferably, the thickness of the intermetallic compound layer is 4.22 μm to 19.57 μm, or 5.36 μm to 20.64 μm.

[0044] By regulating the temperature and controlling the size of intermetallic compounds within this range, the performance of the welded joint can be significantly improved.

[0045] In some embodiments, the intermetallic compound layer is a single layer, and the composition of the intermetallic compound layer is Cu5Zn8. Preferably, the thickness of the Cu5Zn8 layer is 5 μm to 10 μm.

[0046] The performance of the intermetallic compound layer formed entirely of Cu5Zn8 by controlling the process is better than that of the welding interface composed of two layers of Cu5Zn8 and CuZn4. Since the hardness of the Cu5Zn8 phase is as high as 6.81GPa and the Young's modulus is 186.76GPa, it exhibits excellent mechanical properties.

[0047] In some embodiments, the intermetallic compound layer is two layers, wherein the intermetallic compound layer on the side close to the intermediate connecting part on the interface is a CuZn4 layer, and the intermetallic compound layer on the side close to the first connecting part and the second connecting part is a Cu5Zn8 layer.

[0048] In some embodiments, the thickness of the Cu5Zn8 layer is 2.75 μm to 15.22 μm, and the thickness of the CuZn4 layer is 1.47 μm to 5.42 μm.

[0049] Preferably, on the first interface, the thickness of the Cu5Zn8 layer is 9.75 μm to 11.13 μm, and the thickness of the CuZn4 layer is 3.33 μm to 4.05 μm; on the second interface, the thickness of the Cu5Zn8 layer is 10.74 μm to 11.65 μm, and the thickness of the CuZn4 layer is 3.84 μm to 4.05 μm.

[0050] By reasonably controlling the parameters, the thickness between the two layers is controlled, which is beneficial to improve the strength of the welding interface.

[0051] Table 1 Size of Cu5Zn8 layer and CuZn4 layer on the first interface

[0052]

[0053] Table 2 Size of Cu5Zn8 layer and CuZn4 layer on the second interface

[0054]

[0055] In another embodiment of the present application, the present application provides a welding process of a high-temperature-resistant welded joint, comprising the following steps:

[0056] (1) selecting pure copper as the first connecting part, and sandblasting the pure copper;

[0057] (2) using a hot zinc spraying device to heat zinc wire to high temperature, and spraying the molten zinc liquid to the surface of the first connecting part through compressed air;

[0058] (3) after the spraying is completed, storing the zinc coating at constant temperature, the storage temperature is 80℃ to 100℃, and the duration is 30 min to 60 min, so as to ensure that the zinc coating uniformly cools and solidifies on the surface of the first connecting part to form an intermediate connecting part and a first interface, and the intermediate connecting part is a zinc coating layer with a thickness of 10 to 100 μm;

[0059] (4) Put the sprayed first connecting part into the clamp, and put the second connecting part with the welding surface facing the galvanized layer into the clamp. Fix the clamp on the workbench. During the welding process, start the joining device. When the specified temperature is reached, start the ultrasonic device to perform ultrasonic-assisted welding. After the welding time required by the process is reached, stop the ultrasonic device, and continue to apply pressure to the base material until the welding is completed.

[0060] In some embodiments, the spraying parameters are set as: current 30 A, spraying speed 50 m / min, and spraying ratio 80%. It is ensured that the Zn coating is uniformly distributed on the surface of the Cu substrate, and there is no gap or uneven coating area.

[0061] In another embodiment of the present application, the present application provides a welding process of a high-temperature-resistant welded joint, comprising the following steps:

[0062] (1) Select a first connecting part and a second connecting part. After polishing the surfaces to be welded of the first connecting part and the second connecting part, clean them with ultrasonic waves and dry them;

[0063] (2) Put the first connecting part into the clamp, fill in the intermediate connecting part, and then put the second connecting part on the intermediate connecting part. Finally, place the clamp on the heating table;

[0064] (3) Adjust the position of the ultrasonic generator, press the ultrasonic transducer of the ultrasonic generator on the second connecting part, and apply a certain pressure. After the heating table reaches a welding temperature of 225°C to 325°C, start the ultrasonic generator to perform ultrasonic-assisted welding. After the welding time is reached, stop the ultrasonic generator, continue to apply pressure to the second connecting part for a certain period of time, and obtain a high-temperature-resistant welded joint.

[0065] In some embodiments, in step (3), the welding temperature is 265°C to 285°C, the ultrasonic generator is a longitudinal ultrasonic generator, the frequency of the ultrasonic wave is set to 20 kHz, the ultrasonic power is 300w to 600w, the ultrasonic-assisted welding time is 5s to 10s, and the pressure is 6MPa to 10MPa; the total welding time is 3min to 5min.

[0066] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used.

[0067] Example 1

[0068] T2 red copper with a diameter of 5 mm and a height of 3 mm was selected as the copper substrate, and the red copper to be welded was polished smooth with 400 mesh sandpaper, then ultrasonic cleaned and dried for use; the red copper substrate was placed in the welding fixture as shown in Figure 1 , with the to-be-welded area facing upwards, a Zn disc with a diameter of 5 mm and a height of 1 mm polished with 400 mesh sandpaper was filled, a copper substrate with the same size was placed on top to form a Cu / Zn / Cu structure, and then moved to the heating table. When the temperature of the heating table reached 225°C, 8 MPa pressure was applied to the copper substrate using an ultrasonic vibrator, and the timing started. The welding was completed after hot pressing for 300 s.

[0069] The microstructure of the interface was analyzed and observed by optical metallographic microscopy (OM) and scanning electron microscopy (SEM), and the thickness of the intermetallic compound (IMC) layer was calculated by ImageJ software. The shear strength of the solder joint was measured by a CMT universal tensile testing machine and a shear clamp.

[0070] Example 2

[0071] When the temperature of the heating table reached 245°C, 8 MPa pressure was applied to the copper substrate using an ultrasonic vibrator, and the other conditions were the same as in Example 1.

[0072] Example 3

[0073] When the temperature of the heating table reached 265°C, 8 MPa pressure was applied to the copper substrate using an ultrasonic vibrator, and the other conditions were the same as in Example 1.

[0074] Example 4

[0075] When the temperature of the heating table reached 285°C, 8 MPa pressure was applied to the copper substrate using an ultrasonic vibrator, and the other conditions were the same as in Example 1.

[0076] Example 5

[0077] When the temperature of the heating table reached 305°C, 8 MPa pressure was applied to the copper substrate using an ultrasonic vibrator, and the other conditions were the same as in Example 1.

[0078] Example 6

[0079] When the temperature of the heating table reached 325°C, 8 MPa pressure was applied to the copper substrate using an ultrasonic vibrator, and the other conditions were the same as in Example 1.

[0080] From Figure 2 (a) to Figure 2 (f), the overall morphology of the Cu / Zn / Cu joint weld at different welding temperatures is described, and the corresponding welding temperatures are 225°C, 245°C, 265°C, 285°C, 305°C, and 325°C, respectively. The first interface and the second interface have fewer welding defects.

[0081] Example 7

[0082] A Cu column with a diameter of 5 mm and a height of 3 mm was selected as the Cu substrate. Before sandblasting, the surface of the Cu substrate was first cleaned with a detergent to remove grease and other impurities. After cleaning, the substrate was rinsed with deionized water and thoroughly dried to ensure that there was no residual liquid on the surface.

[0083] Cu substrate surface oxide layer removal. To further improve the adhesion of the Zn coating, the surface oxide layer of the Cu substrate was removed using a chemical solution. The Cu substrate was immersed in dilute hydrochloric acid with a concentration of about 5% for 5 minutes to remove the surface oxide layer. Then the substrate was rinsed with deionized water and dried quickly with dry air.

[0084] Cu substrate sandblasting. The Cu substrate with the removed oxide layer was placed in a sandblasting device and sandblasted with river sand with a particle size of 1 mm. The treatment time was controlled at 40 seconds and the surface roughness reached 50 μm to ensure uniform adhesion of the Zn coating. After sandblasting, the substrate surface was cleaned with compressed air and the surface roughness was checked again to ensure that it met the requirements.

[0085] Zn coating spraying. A Zn wire with a diameter of 5 mm was heated to a molten state using a hot zinc spraying device, and the Zn was sprayed onto the treated Cu substrate surface using compressed air. The thickness of the Zn coating was controlled at 10 μm and the purity of the Zn wire was 99.7%.

[0086] The spraying parameters were set as follows: current 30 A, spraying speed 50 m / min, and spraying ratio 80%. These parameters ensured that the Zn coating was uniformly distributed on the Cu substrate surface without gaps or uneven coating areas.

[0087] If the Cu substrate is left in the air for a long time, the area to be welded on the Cu substrate should be polished with 1500 mesh sandpaper before welding to remove the surface oxidation.

[0088] The polished Cu substrate was placed in a clamp, with the area to be welded on the substrate facing upwards. Another identical substrate with the area to be welded facing downwards was aligned with the lower base material and loaded into the clamp. After loading the parts to be welded into the clamp, the clamp was tightened and fixed with bolts on both sides.

[0089] After the heating platform was heated to 260°C, the clamp was placed on the heating platform with tweezers to achieve welding by heating and ultrasonic vibrator pressure. The pressure applied by the ultrasonic vibrator was 6 MPa. Although the Zn layer does not completely melt at this temperature, it can combine with the Cu substrate through diffusion to form a firm welded joint.

[0090] The welding time is controlled at 280s, and when the welding time is 170s, 600w of ultrasonic is applied by the ultrasonic vibrator for 5 seconds to enhance the diffusion effect of the Zn layer and improve the strength and uniformity of the solder joint, and reduce the welding defects.

[0091] After the welding process is completed, the solder joint is cooled by natural air cooling. After the solder joint is completely cooled, a shear test is performed to evaluate its mechanical properties.

[0092] The test results show that the solder joint has excellent tensile and shear strength, which are 23.1MPa, 25.7MPa and 26.2MPa respectively. The strength performance meets the application requirements of high-temperature electronic device packaging, ensuring its reliability and stability in high-temperature working environment.

[0093] Case 8

[0094] A Cu column with a diameter of 5mm and a height of 3mm is selected as the Cu substrate. The substrate is placed in deionized water for cleaning, and after cleaning, it is soaked in dilute hydrochloric acid (concentration of 5%) for 5 minutes to remove the surface oxide layer, and then rinsed with deionized water to ensure that the surface is free of residual oxides.

[0095] River sand with a particle size of 1mm is used to sandblast the surface of the substrate for 40 seconds, and the surface roughness is controlled at 50μm. Subsequently, compressed air is used to remove the residual sand particles on the surface to ensure uniform adhesion of the coating.

[0096] A Zn wire with a diameter of 8mm is melted using a thermal spray Zn device, and the Zn coating thickness is controlled at 20μm. The spraying current is set to 30A, and the spraying speed is 50m / min to ensure that the Zn coating covers the entire substrate surface and has uniform thickness.

[0097] If the Cu substrate is placed in air for a long time, the area to be welded on the Cu substrate should be polished with 1500 mesh sandpaper before welding to remove the surface oxidation.

[0098] The polished Cu substrate is placed in the clamp, with the area to be welded on the substrate facing upwards. Another substrate with the same parameters is placed in the clamp with the area to be welded facing downwards. After the parts to be welded are placed in the clamp, the clamp is tightened and fixed with bolts.

[0099] After the heating platform is heated to 280℃, the clamp is placed on the heating platform to achieve welding through heating and ultrasonic vibrator pressure. The pressure applied by the ultrasonic vibrator is 8MPa.

[0100] The welding time is controlled at 300s, and when the welding time is 2min30s, 800w of ultrasonic is applied by the ultrasonic vibrator for 8 seconds to ensure that the Zn coating is uniformly diffused during the welding process, and the solder joint is uniform and has high strength.

[0101] After the welding is completed, the solder joints are cooled using air cooling. After the solder joints are completely cooled, shear tests are performed to evaluate their mechanical properties. The test results show that the solder joints have excellent tensile and shear strengths of 27.5 MPa, 26.5 MPa, and 29.7 MPa, respectively. From the strengths, it can be seen that the welded joints maintain excellent performance and reliability in high-temperature environments. At the same time, this welding process effectively improves the mechanical properties of the solder joints, ensuring their long-term stability and reliability under various harsh conditions.

[0102] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the technical solutions. Although the applicant has made a detailed description of the present application with reference to the preferred embodiments, those of ordinary skill in the art should understand that those who modify or equivalently replace the technical solutions of the present application without departing from the purpose and scope of the present technical solutions should be covered in the scope of the claims of the present application.

Claims

1. A high temperature resistant welded joint, characterized in that: The invention comprises a first connecting part, an intermediate connecting part and a second connecting part, wherein the intermediate connecting part is located between the first connecting part and the second connecting part for connecting the first connecting part and the second connecting part, wherein the material of the first connecting part is pure copper, the material of the intermediate connecting part is metallic zinc, and the material of the third connecting part is pure copper. The intermediate connecting part is connected to the first connecting part to form a first interface, and the intermediate connecting part is connected to the second connecting part to form a second interface. At least one continuous intermetallic compound layer is formed on the first interface and the second interface, and the composition of the intermetallic compound layer includes Cu5Zn8, and the thickness of the intermetallic compound layer is 4.22μm to 20.64μm.

2. The weld joint according to claim 1, wherein: The intermediate connection part and the first interface are formed by spraying metal Zn onto the first connection part after melting, and the second interface is formed by welding the intermediate connection part and the second connection part together through ultrasonic assisted technology and hot pressing process. The thickness of the intermediate connection part is 10μm to 100μm.

3. The weld joint according to claim 1, wherein: The first interface layer and the second interface layer are welded together by using an ultrasonic-assisted technology and a hot-pressing process, wherein the second connection portion is used to directly bear the pressure applied by the ultrasonic-assisted equipment.

4. The weld joint according to claim 2 or 3, characterized in that: On the first interface, the thickness of the Cu5Zn8 layer is 9.75μm~11.13μm, and the thickness of the CuZn4 layer is 3.33μm~4.05μm; on the second interface, the thickness of the Cu5Zn8 layer is 10.74μm~11.65μm, and the thickness of the CuZn4 layer is 3.84μm~4.05μm.

5. The weld joint according to claim 1, wherein: The intermetallic compound layer is a single layer, and the composition of the intermetallic compound layer is Cu5Zn8; Preferably, the thickness of the Cu5Zn8 layer is 5 μm to 10 μm.

6. The weld joint according to claim 1, wherein: The intermetallic compound layer is composed of two layers, wherein the intermetallic compound layer on the interface close to the middle connecting portion is a CuZn4 layer, and the intermetallic compound layer on the interface close to the first connecting portion and the second connecting portion is a Cu5Zn8 layer.

7. The weld joint according to claim 6, wherein: The thickness of the Cu5Zn8 layer is 2.75μm to 15.22μm, and the thickness of the CuZn4 layer is 1.47μm to 5.42μm. Preferably, the thickness of the Cu5Zn8 layer is 6.41 μm to 11.65 μm, and the thickness of the CuZn4 layer is 2.19 μm to 4.59 μm.

8. A welding process for preparing a high temperature resistant welded joint according to any one of claims 1 to 2 and 4 to 7, characterized in that: The following steps are involved: (1) Selecting pure copper as the first connecting portion and performing sandblasting on the pure copper; (2) using a hot zinc spraying device to heat the zinc wire to a high temperature, and spraying molten zinc liquid onto the surface of the first connecting portion by compressed air; (3) After spraying, the zinc coating is subjected to a constant temperature storage treatment at a temperature of 80° C. to 100° C. for a duration of 30 to 60 minutes to ensure that the zinc coating is uniformly cooled and solidified on the surface of the first connecting portion to form the intermediate connecting portion and the first interface, wherein the intermediate connecting portion is a zinc coating with a thickness of 10 to 100 μm; (4) Place the sprayed first connecting part into the fixture, and then place the second connecting part into the fixture with the welding surface facing the galvanized layer, and fix the fixture on the workbench. During the welding process, start the joining device. When the specified temperature is reached, start the ultrasonic equipment to perform ultrasonic assisted welding. After the welding time required by the process is reached, stop the ultrasonic equipment and continue to apply pressure to the base material until the welding is completed.

9. A welding process for preparing a high temperature resistant welded joint according to any one of claims 1, 3 to 7, characterized in that: The following steps are involved: (1) Selecting the first connecting portion and the second connecting portion, polishing the surface areas to be welded of the first connecting portion and the second connecting portion until smooth, then ultrasonically cleaning and drying them; (2) Place the first connecting part into a fixture, fill in the middle connecting part, then place the second connecting part onto the middle connecting part, and finally place the fixture on a heating table; (3) Adjust the position of the ultrasonic generator, press the ultrasonic vibrator of the ultrasonic generator on the second connecting part, and apply a certain pressure. After the heating table reaches a welding temperature of 225°C to 325°C, start the ultrasonic generator for ultrasonic assisted welding. After the welding time is reached, stop the ultrasonic generator and continue to apply pressure to the second connecting part for a certain period of time to obtain a high-temperature resistant welded joint.

10. The welding process according to claim 9, characterized in that: In step (3), the welding temperature is 265°C to 285°C, the ultrasonic generator is a longitudinal ultrasonic generator, the ultrasonic frequency is set to 20kHz, the ultrasonic power is 300w to 600w, the ultrasonic assisted welding time is 5s to 10s, and the pressure is 6MPa to 10MPa; the total welding time is 3min to 5min.

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