A welding method of a large-size tungsten-silicon alloy target

Abstract

The present application relates to a kind of welding methods of large-size tungsten-silicon alloy target material, the welding method includes: back plate and tungsten-silicon target material are respectively machined, the welding surface of the back plate is sequentially arranged assembly groove and solder groove from top to bottom by concentric, the diameter of the solder groove < the diameter of target material, obtain pretreated back plate and pretreated target material;The solder groove of pretreated back plate is filled with solder, the welding surface of pretreated target material is coated with solder, then back plate and target material are heated to make solder melt, then the welding surface of back plate and target material is respectively treated with infiltration, obtain the back plate and target material after infiltration;The back plate and target material after infiltration are assembled, obtain target material assembly, the target material assembly is treated with pressure, then cooled, obtain the target material assembly after welding.The welding method provided by the present application can effectively improve the welding strength of target material and back plate, avoid target material assembly to be detached, crack, reduce the deformation caused by welding.

Description

Technical Field

[0001] This invention relates to the field of target technology, and specifically to a welding method for large-size tungsten-silicon alloy targets. Background Technology

[0002] In the semiconductor field, tungsten-silicon sputtering targets play a crucial role, being widely used in gate materials and barrier layers. During the sputtering process, the target undergoes repeated heating, thus requiring it to possess good weld strength and low weld stress to avoid defects such as desoldering and cracking, thereby ensuring the stability and reliability of semiconductor devices.

[0003] However, tungsten-silicon is a hard alloy material with relatively poor toughness, making it prone to cracking during uneven heating or deformation. This makes welding large-sized tungsten-silicon targets (diameter ≥ 420 mm, thickness ≤ 13 mm) extremely difficult. Currently, brazing, diffusion welding, and other welding methods are widely used in the manufacture of target components, but these methods still have some limitations. Taking hot isostatic pressing (HIP) welding as an example, after HIP welding, the cladding is difficult to remove and tends to adhere to the target component, thus easily damaging the target component.

[0004] For example, CN104259644A discloses a method for welding tungsten-titanium alloy targets, comprising: firstly providing a tungsten-titanium alloy target and a copper alloy backing plate; forming an aluminum or aluminum alloy layer on the welding surface of the tungsten-titanium target; and then using a diffusion welding method to connect the tungsten-titanium alloy target to the copper alloy backing plate. Although this method can obtain target components, the welding strength is difficult to further improve, and the preparation method is complex and prone to deformation of the target components.

[0005] Therefore, how to solve the problems of desoldering and cracking that occur during the welding process of large-size tungsten silicon targets, improve the welding strength of the target assembly, and reduce the deformation of the target assembly are the technical problems that need to be solved in this field. Summary of the Invention

[0006] To address the above problems, the present invention aims to provide a welding method for large-size tungsten-silicon alloy targets. Compared with the prior art, the welding method provided by the present invention can effectively improve the welding bond strength between the target and the backing plate, avoid target assembly desoldering and cracking, and reduce deformation caused by welding.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a welding method for large-size tungsten-silicon alloy targets, the welding method comprising the following steps:

[0009] (1) The back plate and the tungsten silicon target are machined separately. The welding surface of the back plate is concentrically provided with an assembly groove and a solder groove from top to bottom. The diameter of the solder groove is less than the diameter of the target, so as to obtain the pretreated back plate and the pretreated target.

[0010] (2) Fill the solder groove of the pre-treated back plate obtained in step (1) with solder, coat the welding surface of the pre-treated target with solder, then heat the back plate and the target to melt the solder, and then wet the welding surfaces of the back plate and the target respectively to obtain the wetted back plate and target.

[0011] (3) Assemble the impregnated backplate and target material obtained in step (2) to obtain a target material assembly. Apply pressure to the target material assembly and then cool it to obtain a welded target material assembly.

[0012] In the preparation method provided by the present invention, by setting an assembly groove and a solder groove, the docking of the target material and the back plate is ensured, and sufficient solder is filled in the solder groove to avoid the problem of insufficient solder. This allows for sufficient wetting treatment of the welding surface, further improving the bonding strength between the solder and the welding surface and enhancing the weld's firmness. Subsequently, the pressure treatment can effectively eliminate the micro gaps in the welding process, allowing the solder to fill the welding surface more fully and further enhancing the welding strength.

[0013] Preferably, the back plate in step (1) comprises a copper-chromium alloy back plate.

[0014] Preferably, the diameter of the tungsten-silicon target material in step (1) is ≥420mm, for example, it can be 420mm, 430mm, 440mm or 450mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the thickness of the tungsten-silicon target is ≤13mm, for example, it can be 13mm, 12mm, 11mm or 10mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, after machining in step (1), the surface roughness Ra of the back plate is 4-8 μm, for example, it can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, after machining, the surface roughness Ra of the tungsten-silicon target is 7-12 μm, for example, it can be 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm or 12 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0018] In this invention, by preferably controlling the surface roughness of the backplate and the target material within a specific range, it is possible to help the solder to fully and evenly wet the welding surface, so that the solder can spread and fill the welding area better, reduce welding defects, and improve welding strength.

[0019] Preferably, the difference between the diameter of the solder bath and the diameter of the target material in step (1) is 4-6 mm, for example, it can be 4 mm, 4.5 mm, 5 mm, 5.5 mm or 6 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] In this invention, by preferably controlling the difference between the diameter of the solder bath and the diameter of the target material within a specific range, it is possible to effectively prevent the solder from overflowing during the welding process, ensure that the solder is evenly distributed during the welding process, and at the same time ensure that the contact area between the solder and the target material and the back plate is appropriate, thereby ensuring the welding strength.

[0021] Preferably, the depth of the solder groove is 2-4mm, for example, it can be 2mm, 2.2mm, 2.4mm, 2.6mm, 2.8mm, 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm or 4mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In this invention, by optimizing the depth of the solder bath, it is possible to ensure that the solder is filled in an appropriate amount during the welding process. When the immersion treatment is performed, the solder in the solder bath is introduced into the welding surface of the back plate, which improves the welding strength and avoids the solder overflow caused by excessive filling, resulting in welding defects and affecting the welding quality. At the same time, it avoids the solder filling being too small, which would prevent the welding gap from being filled and thus avoid affecting the firmness and reliability of the welding.

[0023] Preferably, the solder in step (2) includes indium solder.

[0024] Preferably, the heating rate is ≤10℃ / min, for example, it can be 10℃ / min, 9℃ / min, 8℃ / min, 7℃ / min, 6℃ / min, 5℃ / min, 4℃ / min, 3℃ / min, 2℃ / min or 1℃ / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] Preferably, the final heating temperature is 190-230℃, for example, it can be 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, 220℃, 225℃ or 230℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0026] Preferably, the immersion treatment in step (2) is performed under ultrasonic conditions.

[0027] Preferably, the frequency of the ultrasonic wave is 15-25kHz, for example, it can be 15kHz, 16kHz, 17kHz, 18kHz, 19kHz, 20kHz, 21kHz, 22kHz, 23kHz, 24kHz or 25kHz, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0028] Preferably, the amplitude of the ultrasonic wave is 5-45μm, for example, it can be 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm or 45μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the power of the ultrasonic wave is 800-2000W, for example, it can be 800W, 900W, 1000W, 1100W, 1200W, 1300W, 1400W, 1500W, 1600W, 1700W, 1800W, 1900W or 2000W, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the immersion time of the back plate is 5-15 minutes, for example, 5 minutes, 6 minutes, 8 minutes, 10 minutes, 12 minutes, 14 minutes or 15 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the immersion time of the tungsten-silicon target is 15-25 min, for example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min or 25 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] In this invention, by optimally controlling the frequency, amplitude, power, and duration of the ultrasonic waves during the immersion process, the solder can be better spread and fill the welding gap, thereby improving the welding strength.

[0033] Preferably, the pressure of the pressurization process in step (3) is 5-10 MPa, for example, it can be 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa or 10 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the pressurization process includes placing a pressure block on the upper surface of the target assembly.

[0035] Preferably, the contact area between the pressure block and the target assembly accounts for ≥60% of the upper surface area, for example, 60%, 65%, 70%, 75%, 80%, 85%, or 90%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] In this invention, by optimally controlling the pressure of the pressurization process and the ratio of the contact area between the pressure block and the target material assembly to the upper surface area, it is possible to promote the densification of the welding, reduce welding defects, reduce stress concentration during the welding process, and avoid excessive deformation of the target material assembly.

[0037] Preferably, the cooling rate in step (3) is ≤10℃ / min, for example, it can be 10℃ / min, 9℃ / min, 8℃ / min, 7℃ / min, 6℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] As a preferred embodiment of the present invention, the preparation method includes the following steps:

[0039] (1) The copper-chromium alloy back plate and the tungsten-silicon target are machined separately. The welding surface of the back plate is concentrically provided with an assembly groove and a solder groove from top to bottom. The depth of the solder groove is 2-4 mm, the diameter of the solder groove is less than the diameter of the target and the difference is 4-6 mm. After machining, the surface roughness Ra of the back plate is 4-8 μm and the surface roughness Ra of the tungsten-silicon target is 7-12 μm, thus obtaining the pretreated back plate and the pretreated target.

[0040] (2) Fill the solder tank of the pretreated backplate obtained in step (1) with indium solder, coat the welding surface of the pretreated target with indium solder, and then heat the backplate and target at a heating rate of ≤10℃ / min to the final temperature of 190-230℃ to melt the solder. Then, the welding surfaces of the backplate and target are immersed in ultrasonic conditions. The immersion treatment is carried out under ultrasonic conditions. The frequency of the ultrasonic wave is 15-25kHz, the amplitude of the ultrasonic wave is 5-45μm, the power of the ultrasonic wave is 800-2000W, the immersion treatment time of the backplate is 5-15min, and the immersion treatment time of the tungsten silicon target is 15-25min to obtain the immersed backplate and target.

[0041] (3) Assemble the impregnated backplate and target material obtained in step (2) to obtain a target material assembly. Pressurize the target material assembly at a pressure of 5-10 MPa and then cool it at a rate of ≤10℃ / min to obtain the welded target material assembly.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] In the preparation method provided by this invention, the assembly groove and solder groove ensure the mating of the target material and the backplate, and also allow sufficient solder to be filled into the solder groove, avoiding the problem of insufficient solder. This ensures thorough wetting of the welding surface. Furthermore, the pressure treatment eliminates micro-gaps during the welding process, allowing the solder to more fully fill the welding surface, further enhancing the welding strength, and preventing excessive deformation of the target material assembly. Under preferred conditions, the preparation method provided by this invention can achieve a weld bonding strength of over 20 MPa and a deformation of less than 0.1 mm for the target material assembly. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the target assembly provided in Embodiment 1 of the present invention;

[0045] 1-Target material; 2-Backplate; 3-Assembly groove; 4-Solder groove. Detailed Implementation

[0046] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0047] Example 1

[0048] This embodiment provides a welding method for large-size tungsten-silicon alloy targets, the preparation method including the following steps:

[0049] (1) The copper-chromium alloy back plate and the tungsten-silicon target (diameter 420mm, thickness 13mm) are machined respectively. The surface roughness Ra of the back plate after machining is 6μm and the surface roughness Ra of the tungsten-silicon target is 10μm, so as to obtain the pre-treated back plate and the pre-treated target.

[0050] like Figure 1 As shown, the machining process also includes concentrically setting an assembly groove 3 and a solder groove 4 on the welding surface of the back plate 2 from top to bottom. The depth of the solder groove 4 is 3mm, and the diameter of the solder groove 4 is less than the diameter of the target material 1 with a difference of 5mm.

[0051] (2) Fill the solder tank of the pretreated backplate obtained in step (1) with indium solder, coat the welding surface of the pretreated target with indium solder, and then heat the backplate and target at a heating rate of 10℃ / min to the final temperature of 210℃ to melt the solder. Then, the welding surfaces of the backplate and target are impregnated. The impregnation treatment is carried out under ultrasonic conditions, with an ultrasonic frequency of 20kHz, an ultrasonic amplitude of 25μm, an ultrasonic power of 1400W, an impregnation treatment time of 10min for the backplate, and an impregnation treatment time of 20min for the tungsten silicon target, to obtain the impregnated backplate and target.

[0052] (3) Assemble the impregnated back plate and target material obtained in step (2) to obtain a target material assembly. Place the pressure block on the upper surface of the target material assembly for pressure treatment. The contact area between the pressure block and the target material assembly accounts for 60% of the upper surface area. The pressure of the pressure treatment is 8 MPa. Then cool at a rate of 10℃ / min to obtain the welded target material assembly.

[0053] Example 2

[0054] This embodiment provides a welding method for large-size tungsten-silicon alloy targets, the preparation method including the following steps:

[0055] (1) The copper-chromium alloy back plate and the tungsten-silicon target (diameter 420mm, thickness 13mm) are machined respectively. The welding surface of the back plate is concentrically set with assembly groove and solder groove from top to bottom. The depth of the solder groove is 2mm. The diameter of the solder groove is less than the diameter of the target and the difference is 4mm. After machining, the surface roughness Ra of the back plate is 8μm and the surface roughness Ra of the tungsten-silicon target is 7μm, thus obtaining the pretreated back plate and the pretreated target.

[0056] (2) Fill the solder tank of the pretreated backplate obtained in step (1) with indium solder, coat the welding surface of the pretreated target with indium solder, and then heat the backplate and target at a heating rate of 8℃ / min to the final temperature of 230℃ to melt the solder. Then, the welding surfaces of the backplate and target are immersed in the ultrasonic wave. The immersion treatment is carried out under ultrasonic conditions. The frequency of the ultrasonic wave is 15kHz, the amplitude of the ultrasonic wave is 45μm, the power of the ultrasonic wave is 800W, the immersion treatment time of the backplate is 15min, and the immersion treatment time of the tungsten silicon target is 15min, so as to obtain the immersed backplate and target.

[0057] (3) Assemble the impregnated back plate and target material obtained in step (2) to obtain a target material assembly. Place the pressure block on the upper surface of the target material assembly for pressure treatment. The contact area between the pressure block and the target material assembly accounts for 65% of the upper surface area. The pressure of the pressure treatment is 5 MPa. Then cool at a rate of 8℃ / min to obtain the welded target material assembly.

[0058] Example 3

[0059] This embodiment provides a welding method for large-size tungsten-silicon alloy targets, the preparation method including the following steps:

[0060] (1) The copper-chromium alloy back plate and the tungsten-silicon target (diameter 420mm, thickness 13mm) are machined respectively. The welding surface of the back plate is concentrically set with assembly groove and solder groove from top to bottom. The depth of the solder groove is 4mm. The diameter of the solder groove is less than the diameter of the target and the difference is 6mm. The surface roughness Ra of the back plate after machining is 4μm and the surface roughness Ra of the tungsten-silicon target is 12μm, thus obtaining the pretreated back plate and the pretreated target.

[0061] (2) Fill the solder tank of the pretreated backplate obtained in step (1) with indium solder, coat the welding surface of the pretreated target with indium solder, and then heat the backplate and target at a heating rate of 6℃ / min to the final temperature of 190℃ to melt the solder. Then, the welding surfaces of the backplate and target are immersed in the ultrasonic wave, which is performed under ultrasonic conditions. The ultrasonic wave frequency is 25kHz, the ultrasonic wave amplitude is 5μm, the ultrasonic wave power is 2000W, the immersion time of the backplate is 5min, and the immersion time of the tungsten silicon target is 25min, so as to obtain the immersed backplate and target.

[0062] (3) Assemble the impregnated back plate and target material obtained in step (2) to obtain a target material assembly. Place the pressure block on the upper surface of the target material assembly for pressure treatment. The contact area between the pressure block and the target material assembly accounts for 75% of the upper surface area. The pressure of the pressure treatment is 10 MPa. Then cool at a rate of 9℃ / min to obtain the welded target material assembly.

[0063] Example 4

[0064] This embodiment provides a welding method for a large-size tungsten-silicon alloy target. The only difference between the preparation method and that in Example 1 is that the surface roughness Ra of the tungsten-silicon target after machining is 3 μm.

[0065] Example 5

[0066] This embodiment provides a welding method for a large-size tungsten-silicon alloy target. The only difference between the preparation method and that in Embodiment 1 is that the surface roughness Ra of the tungsten-silicon target after machining is 20 μm.

[0067] Example 6

[0068] This embodiment provides a welding method for a large-size tungsten-silicon alloy target. The only difference between the preparation method and that in Embodiment 1 is that the difference between the diameter of the solder bath and the diameter of the target is 1 mm.

[0069] Example 7

[0070] This embodiment provides a welding method for a large-size tungsten-silicon alloy target. The only difference between the preparation method and that in Embodiment 1 is that the difference between the diameter of the solder bath and the diameter of the target is 10 mm.

[0071] Example 8

[0072] This embodiment provides a welding method for a large-size tungsten-silicon alloy target. The only difference between this preparation method and that of Embodiment 1 is that the ultrasonic power is 500W.

[0073] Example 9

[0074] This embodiment provides a welding method for a large-size tungsten-silicon alloy target. The only difference between this preparation method and that of Embodiment 1 is that the frequency of the ultrasonic wave is 10 kHz.

[0075] Example 10

[0076] This embodiment provides a welding method for large-size tungsten-silicon alloy targets. The only difference between this preparation method and that of Embodiment 1 is that the pressure of the pressure treatment is 2 MPa.

[0077] Example 11

[0078] This embodiment provides a welding method for large-size tungsten-silicon alloy targets. The only difference between this preparation method and that of Embodiment 1 is that the pressure of the pressure treatment is 15 MPa.

[0079] Example 12

[0080] This embodiment provides a welding method for a large-size tungsten-silicon alloy target. The only difference between the preparation method and that in Embodiment 1 is that the contact area between the pressure block and the target assembly accounts for 40% of the upper surface area.

[0081] Comparative Example 1

[0082] This comparative example provides a welding method for a large-size tungsten-silicon alloy target. The only difference from Example 1 is that no solder tank is provided, and the solder is only applied to the welding surface of the back plate.

[0083] The weld bond strength of the target material components in Examples 1-12 and Comparative Example 1 was tested by tensile tests, and the results are shown in Table 1.

[0084] The deformation of the target components in Examples 1-12 and Comparative Example 1 was tested using a coordinate measuring machine, and the results are shown in Table 1.

[0085] Table 1

[0086] Example 1 23 0.05 Example 2 22 0.07 Example 3 20 0.08 Example 4 18 0.05 Example 5 15 0.05 Example 6 17 0.07 Example 7 12 0.05 Example 8 11 0.05 Example 9 10 0.05 Example 10 13 0.03 Example 11 23 0.24 Example 12 20 0.18 Comparative Example 1 8 0.04

[0087] The following points can be observed from the data in Table 1:

[0088] (1) As can be seen from the data of Examples 1-12, under preferred conditions, the preparation method provided by the present invention can make the welding bonding strength of the target material assembly reach more than 20MPa and the deformation amount reach less than 0.1mm.

[0089] (2) By comparing the data of Example 1 and Examples 4-5, it can be seen that the present invention can help the solder to fully and evenly wet the welding surface and improve the welding strength by optimizing the surface roughness of the back plate and the target material.

[0090] (3) By comprehensively comparing the data of Example 1, Example 6-7 and Comparative Example 1, it can be seen that the present invention can effectively prevent the solder from overflowing during the welding process by setting a solder groove on the back plate and preferably controlling the difference between the diameter of the solder groove and the diameter of the target material. This ensures that the solder is evenly distributed during the welding process, while ensuring that the contact area between the solder and the target material and the back plate is appropriate, thus ensuring the welding strength.

[0091] (4) A comprehensive comparison of the data from Examples 1 and 8-9 shows that the present invention, by optimizing the control of the frequency and power of the ultrasonic waves, can help the solder to be fully and evenly wetted on the welding surface and improve the welding strength.

[0092] (5) By comprehensively comparing the data of Example 1 and Examples 10-12, it can be seen that the present invention can improve the welding bond strength while avoiding excessive deformation of the target material by optimizing the control of the pressure of the pressurization process and the ratio of the contact area between the pressure block and the target material assembly to the upper surface area.

[0093] In summary, the welding method provided by this invention can effectively improve the welding bond strength between the target material and the backplate, avoid target material assembly desoldering and cracking, and reduce deformation caused by welding.

[0094] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A welding method for large-size tungsten-silicon alloy targets, characterized in that, The welding method comprises the following steps: (1) The back plate and the tungsten silicon target are machined separately. The welding surface of the back plate is concentrically provided with an assembly groove and a solder groove from top to bottom. The diameter of the solder groove is less than the diameter of the target, thus obtaining a pre-treated back plate and a pre-treated target. The difference between the diameter of the solder groove and the diameter of the target is 4-6 mm. The diameter of the tungsten silicon target is ≥420 mm. The thickness of the tungsten silicon target is ≤13 mm. After machining, the surface roughness Ra of the tungsten silicon target is 7-12 μm. (2) Fill the solder groove of the pretreated backplate obtained in step (1) with solder, coat the welding surface of the pretreated target with solder, then heat the backplate and the target to melt the solder, and then perform immersion treatment on the welding surfaces of the backplate and the target respectively to obtain the immersion backplate and the target; the immersion treatment is performed under ultrasonic conditions; the frequency of the ultrasonic wave is 15-25kHz; the power of the ultrasonic wave is 800-2000W. (3) Assemble the impregnated backplate and target material obtained in step (2) to obtain a target material assembly, pressurize the target material assembly, and then cool it to obtain a welded target material assembly. The pressure for the pressurization process is 5-10 MPa; The pressurization process includes: placing a pressure block on the upper surface of the target assembly; The contact area between the pressure block and the target assembly accounts for ≥60% of the upper surface area.

2. The welding method according to claim 1, characterized in that, The backplate in step (1) includes a copper-chromium alloy backplate.

3. The welding method according to claim 1, characterized in that, After machining in step (1), the surface roughness Ra of the back plate is 4-8 μm.

4. The welding method according to claim 1, characterized in that, The depth of the solder bath in step (1) is 2-4 mm.

5. The welding method according to claim 1, characterized in that, The solder in step (2) includes indium solder.

6. The welding method according to claim 1, characterized in that, The heating rate in step (2) is ≤10℃ / min.

7. The welding method according to claim 1, characterized in that, The final heating temperature in step (2) is 190-230℃.

8. The welding method according to claim 1, characterized in that, The amplitude of the ultrasonic wave in step (2) is 5-45 μm.

9. The welding method according to claim 1, characterized in that, The soaking time for the backplate in step (2) is 5-15 minutes.

10. The welding method according to claim 1, characterized in that, The immersion time for the tungsten-silicon target in step (2) is 15-25 minutes.

11. The welding method according to claim 1, characterized in that, The cooling rate in step (3) is ≤10℃ / min.

12. The welding method according to claim 1, characterized in that, The welding method comprises the following steps: (1) The copper-chromium alloy back plate and the tungsten-silicon target are machined respectively. The welding surface of the back plate is concentrically set with an assembly groove and a solder groove from top to bottom. The depth of the solder groove is 2-4 mm, the diameter of the solder groove is less than the diameter of the target and the difference is 4-6 mm. After machining, the surface roughness Ra of the back plate is 4-8 μm and the surface roughness Ra of the tungsten-silicon target is 7-12 μm, thus obtaining the pretreated back plate and the pretreated target. (2) Fill the solder tank of the pretreated backplate obtained in step (1) with indium solder, coat the welding surface of the pretreated target with indium solder, and then heat the backplate and target at a heating rate of ≤10℃ / min to the final temperature of 190-230℃ to melt the solder. Then, the welding surfaces of the backplate and target are immersed in the ultrasonic wave. The immersion treatment is carried out under ultrasonic conditions. The frequency of the ultrasonic wave is 15-25kHz, the amplitude of the ultrasonic wave is 5-45μm, the power of the ultrasonic wave is 800-2000W, the immersion treatment time of the backplate is 5-15min, and the immersion treatment time of the tungsten silicon target is 15-25min to obtain the immersed backplate and target. (3) Assemble the impregnated back plate and target material obtained in step (2) to obtain a target material assembly. Pressurize the target material assembly at a pressure of 5-10 MPa and then cool it at a rate of ≤10℃ / min to obtain the welded target material assembly. The contact area between the pressure block and the target material assembly accounts for ≥60% of the upper surface area.

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