Pretreatment method of cobalt target blank for diffusion welding

Abstract

The invention provides a pretreatment method of a cobalt target blank for diffusion welding, which comprises the following steps of: (1) carrying out hot pressing on the cobalt target blank, milling threads on the welding surface of the cobalt target blank, and then cleaning; and (2) the welding face of the cobalt target blank cleaned in the step (1) is subjected to film coating treatment, then ultrasonic cleaning is conducted, and the cobalt target blank subjected to pretreatment is obtained. The cobalt target blank is firstly subjected to hot pressing, and then the welding surface of the cobalt target blank is sequentially subjected to thread milling and coating treatment, so that the combination difficulty of the cobalt target blank and the back plate can be reduced, the welding strength between the cobalt target blank and the back plate is improved, and the welding quality and efficiency of a product are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of target blank pretreatment, and relates to a pretreatment method of a cobalt target blank for diffusion welding. Background Art

[0002] Sputtering targets are an extremely important key material for manufacturing semiconductor chips. The principle of using them to make devices is to use physical vapor deposition technology to bombard the target with high-voltage accelerated gaseous ions, so that the atoms of the target are sputtered out and deposited on the silicon wafer in the form of a thin film, eventually forming a complex wiring structure in the semiconductor chip. Sputtering targets have many advantages such as uniformity and controllability of metal coatings, and are widely used in the semiconductor field.

[0003] Since the strength of sputtering targets varies, in actual applications, it is necessary to combine a sputtering target blank that meets the performance requirements with a backing plate with a certain strength to form a target assembly, which is then installed on the sputtering machine to effectively control sputtering under the action of magnetic and electric fields. The sputtering target and the backing plate need to be processed and welded to ensure the success of subsequent sputtering. If the welding bond between the metal sputtering target and the backing plate is poor, the metal sputtering target will deform, crack, or even fall off the backing plate under heat conditions, which will not only fail to achieve a uniform sputtering effect, but may also cause damage to the sputtering base.

[0004] At present, common welding methods include brazing and diffusion welding. Brazing refers to a welding method in which the solder and the weldment are heated to the melting temperature of the solder at the same time, and the gap between the solid workpieces is filled with liquid solder to connect the metals. Diffusion welding is a welding method that fits the weldments tightly together and keeps them at a certain temperature and pressure for a period of time, so that the atoms between the contact surfaces diffuse with each other to form a connection. For cobalt targets used in high-power sputtering processes, diffusion welding is generally used. However, diffusion welding between the cobalt target and the back plate is difficult, so the welding surface needs to be pre-treated to meet the welding requirements.

[0005] At present, there are two pre-treatment methods for diffusion welding of cobalt target materials: the welding surface of the target blank is ground and cleaned, and then a titanium metal layer is plated after cleaning, and then the target blank is welded with a copper back plate, and finally diffusion welded by hot isostatic pressing equipment; or the welding surface of the target blank is sandblasted, cleaned, and then a titanium metal layer is plated, and then the target blank is welded with a copper back plate, and finally diffusion welded by hot isostatic pressing equipment. Although both methods can be used for welding, their welding strength is not high, which affects the welding quality of the product.

[0006] In summary, for the welding process of cobalt targets, it is also necessary to provide a suitable pre-treatment process according to the characteristics of the target material to simplify the operation, reduce costs and improve welding strength. Summary of the invention

[0007] The object of the present invention is to provide a pretreatment method for a cobalt target blank for diffusion welding, which reduces the difficulty of combining the cobalt target blank with a back plate by first hot pressing the cobalt target blank and then sequentially performing thread milling and coating treatment on the welding surface of the cobalt target blank, thereby improving the welding strength between the two and improving the welding quality and efficiency of the product.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a pretreatment method for a cobalt target blank for diffusion welding, the pretreatment method comprising the following steps:

[0010] (1) After hot pressing the cobalt target blank, milling threads are performed on the welding surface of the cobalt target blank, and then cleaning is performed;

[0011] (2) The welding surface of the cobalt target blank after the cleaning treatment in step (1) is subjected to coating treatment, and then ultrasonic cleaning is performed to obtain a cobalt target blank after pretreatment.

[0012] In the present invention, due to the material characteristics of the cobalt target, diffusion welding between the target and the back plate (with low hardness) is difficult, so the cobalt target blank needs to be pre-treated. The cobalt target blank in step (1) is a cobalt target blank after truncated cone grinding, and the cobalt target blank after truncated cone grinding has a deformation of about 0.5-3 mm, and it is difficult to directly perform milling on its surface.

[0013] The pretreatment method provided by the present invention first hot presses the cobalt target blank, and then sequentially performs milling processing of threads and coating treatment on the welding surface of the cobalt target blank, which can reduce the difficulty of combining the cobalt target blank with the back plate, thereby improving the welding strength between the two, and improving the welding quality and efficiency of the product.

[0014] It is worth mentioning that by hot pressing the cobalt target blank first, it not only helps to improve the flatness of the target blank, which is conducive to the smooth milling of the thread, and improves the uniformity of the coating on the welding surface of the cobalt target blank, but also helps to release the stress inside the cobalt target blank and reduce the risk of cracking due to stress concentration; subsequently, the thread is processed by milling on the welding surface of the cobalt target blank, which not only increases the area of ​​the coating on the welding surface, but also enables the thread to be embedded in the back plate during the subsequent diffusion welding process, thereby effectively enhancing the welding strength between the cobalt target blank and the back plate; and then coating is performed to effectively reduce the difficulty of combining the cobalt target blank and the back plate, thereby improving the welding strength between the two and improving the welding quality and efficiency of the product.

[0015] As a preferred technical solution of the present invention, the hot pressing method described in step (1) includes: placing the cobalt target blank with the convex surface facing upward on a heating platform, then placing a stainless steel sheet and a pad on the convex surface of the cobalt target blank in sequence, and then placing pressing blocks at the four corners of the pad, followed by heating.

[0016] As a preferred technical solution of the present invention, the diameters of the cobalt target blank, the stainless steel sheet and the spacer block are the same.

[0017] Preferably, the weight of the briquette is 15-25kg, for example, it can be 16kg, 17kg, 18kg, 19kg, 20kg, 21kg, 22kg, 23kg or 24kg, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0018] In the present invention, by controlling the weight range of the pressed block, the target blank flatness requirement can be achieved at a relatively low temperature, and it is also helpful to maintain the shape and size of the target blank and reduce deformation during hot pressing.

[0019] As a preferred technical solution of the present invention, the heating temperature is 400-600°C, for example, it can be 420°C, 450°C, 480°C, 500°C, 520°C, 550°C or 580°C, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0020] In the present invention, controlling the heating temperature range helps to remove stress inside the cobalt target blank and prevent cracking during subsequent processing.

[0021] Preferably, the heating insulation time is 2-4h, for example, it can be 2.2h, 2.5h, 2.6h, 2.8h, 3h, 3.2h, 3.5h, 3.6h or 3.8h, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0022] Preferably, the heating is followed by cooling to room temperature.

[0023] As a preferred technical solution of the present invention, after hot pressing in step (1), the flatness of the cobalt target blank is less than 0.1 mm, for example, it can be 0.09 mm, 0.08 mm, 0.07 mm, 0.06 mm, 0.05 mm, 0.04 mm or 0.02 mm, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0024] As a preferred technical solution of the present invention, the feed rate of the milling thread in step (1) is 0.04-0.06mm, for example, it can be 0.042mm, 0.045mm, 0.048mm, 0.05mm, 0.052mm, 0.055mm or 0.058mm, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0025] Preferably, the rotation speed of the milling thread in step (1) is 450-550 r / min, for example, it can be 460 r / min, 470 r / min, 480 r / min, 490 r / min, 500 r / min, 510 r / min, 520 r / min, 530 r / min or 540 r / min, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0026] It is worth noting that controlling the feed rate and speed of the milling thread can help improve the machining accuracy and the surface quality of the target blank welding surface and avoid deformation of the cobalt target blank.

[0027] As a preferred technical solution of the present invention, the thread pitch of the welding surface of the cobalt target blank after the thread is milled in step (1) is 0.6-0.8mm, for example, it can be 0.62mm, 0.65mm, 0.68mm, 0.7mm, 0.72mm, 0.75mm or 0.78mm, etc., and the thread depth is 0.25-0.35mm, for example, it can be 0.26mm, 0.27mm, 0.28mm, 0.29mm, 0.3mm, 0.31mm, 0.32mm, 0.33mm or 0.34mm, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0028] In the present invention, by controlling the thread pitch and depth range, not only can the area of ​​the welding surface coating be increased, but also the threads can be easily embedded in the back plate during the subsequent diffusion welding process, thereby effectively enhancing the welding strength between the cobalt target blank and the back plate.

[0029] As a preferred technical solution of the present invention, the cleaning process in step (1) includes a first ultrasonic cleaning, a detergent scrubbing, a pure water rinse and a second ultrasonic cleaning performed in sequence.

[0030] In the present invention, by performing a specific cleaning treatment on the cobalt target blank, the cleanliness requirement of the welding surface of the cobalt target blank can be effectively controlled, and the uniformity of the coating on the welding surface of the cobalt target blank can also be ensured.

[0031] Preferably, the medium used for the first ultrasonic cleaning includes degreasing liquid.

[0032] In the present invention, the components of the degreasing liquid are not specifically limited, as long as the degreasing liquid can remove oil stains such as chip liquid in the process of thread milling, and commercially available products can be used.

[0033] Preferably, the first ultrasonic cleaning time is 3-10 min, for example, 4 min, 5 min, 6 min, 7 min, 8 min or 9 min, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0034] Preferably, the medium used for the second ultrasonic cleaning includes IPA liquid.

[0035] In the present invention, the welding surface of the cobalt target blank is placed downward during the first ultrasonic cleaning and the second ultrasonic cleaning.

[0036] Preferably, the second ultrasonic cleaning time is 3-10 min, for example, 4 min, 5 min, 6 min, 7 min, 8 min or 9 min, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0037] Preferably, drying is performed after the second ultrasonic cleaning.

[0038] As a preferred technical solution of the present invention, the material of the coating in step (2) includes titanium.

[0039] Preferably, the thickness of the film layer formed after the coating treatment in step (2) is 1-6 μm, for example, it can be 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or 5.5 μm, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0040] Preferably, the medium used for ultrasonic cleaning in step (2) includes IPA liquid.

[0041] Preferably, the ultrasonic cleaning time in step (2) is 3-10 min, for example, 4 min, 5 min, 6 min, 7 min, 8 min or 9 min, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0042] Preferably, the ultrasonic cleaning in step (2) is followed by drying.

[0043] As a preferred technical solution of the present invention, the pre-treatment method comprises the following steps:

[0044] (1) placing a cobalt target blank with its convex surface facing upward on a heating platform, placing a stainless steel sheet and a pad on the convex surface of the cobalt target blank in sequence, and then placing a 15-25 kg pressed block at the four corners of the pad, and then heating at a temperature of 400-600°C and keeping it warm for 2-4 hours, and then cooling to room temperature, the flatness of the obtained cobalt target blank is less than 0.1 mm, and then milling the thread on the welding surface of the cobalt target blank at a feed rate of 0.04-0.06 mm and a rotation speed of 450-550 r / min, the thread pitch is 0.6-0.8 mm, the thread depth is 0.25-0.35 mm, and finally cleaning is performed;

[0045] The diameters of the cobalt target blank, the stainless steel sheet and the spacer block are the same;

[0046] The cleaning process includes a first ultrasonic cleaning, a detergent scrubbing, a pure water rinse, and a second ultrasonic cleaning performed in sequence; the medium used in the first ultrasonic cleaning includes a degreasing liquid; the time of the first ultrasonic cleaning is 3-10 minutes; the medium used in the second ultrasonic cleaning includes an IPA liquid; the time of the second ultrasonic cleaning is 3-10 minutes; and drying is also performed after the second ultrasonic cleaning;

[0047] (2) The welding surface of the cobalt target blank after the cleaning treatment in step (1) is subjected to a coating treatment, wherein the coating material includes titanium, and the thickness of the film layer is 1-6 μm, and then ultrasonic cleaning is performed for 3-10 minutes and drying is performed in sequence, wherein the medium used for ultrasonic cleaning includes IPA liquid, to obtain a cobalt target blank after pretreatment.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The pretreatment method provided by the present invention, by first hot pressing the cobalt target blank, not only helps to release the stress inside the cobalt target blank and reduce the risk of cracking caused by stress concentration, but also helps to improve the flatness of the target blank, thereby facilitating the smooth milling of the thread and improving the uniformity of the coating on the welding surface of the cobalt target blank; then the thread is processed on the welding surface of the cobalt target blank by milling, which not only increases the area of ​​the coating on the welding surface, but also enables the thread to be embedded in the back plate during the subsequent diffusion welding process, thereby effectively enhancing the welding strength between the cobalt target blank and the back plate; then the coating is performed, which effectively reduces the difficulty of combining the cobalt target blank and the back plate, thereby improving the welding strength between the two, and improving the welding quality and efficiency of the product;

[0050] (2) The pretreatment method provided by the present invention can ensure that the obtained cobalt target blank is used for subsequent diffusion welding, which can not only ensure that the welding bonding rate between the target blank and the back plate is ≥99%, greatly improving the yield rate, but also ensure that the welding strength between the target blank and the back plate is ≥100MPa, and the welding will not deform. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] In the following embodiments and comparative examples, there is no limitation on the specific product selected for the degreasing liquid, as long as the degreasing liquid can achieve the effect of removing oil stains.

[0053] Example 1

[0054] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding, the pretreatment method comprising the following steps:

[0055] (1) The cobalt target blank is placed on a heating platform with the convex surface facing upward, a stainless steel sheet and an aluminum pad are placed on the convex surface of the cobalt target blank in sequence, and then a 20 kg pressing block is placed at the four corners of the aluminum pad, and then heated at a temperature of 500 ° C and kept warm for 3 hours, and then cooled to room temperature, and then the thread is milled on the welding surface of the cobalt target blank at a feed rate of 0.05 mm and a rotation speed of 500 r / min, and finally cleaned;

[0056] The diameters of the cobalt target blank, the stainless steel sheet and the aluminum spacer are the same;

[0057] The cleaning process includes a first ultrasonic cleaning for 6 minutes, a detergent scrub, a pure water rinse, and a second ultrasonic cleaning for 6 minutes in sequence; the medium used in the first ultrasonic cleaning is a degreasing liquid; the medium used in the second ultrasonic cleaning is an IPA liquid; and the second ultrasonic cleaning is followed by drying for 60 minutes;

[0058] (2) The welding surface of the cobalt target blank after the cleaning treatment in step (1) is subjected to titanium coating treatment to form a titanium film layer with a thickness of 3 μm, and then ultrasonic cleaning is performed for 6 minutes and dried for 60 minutes in sequence, wherein the medium used for ultrasonic cleaning is IPA liquid, to obtain a cobalt target blank after pretreatment.

[0059] Example 2

[0060] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding, the pretreatment method comprising the following steps:

[0061] (1) The cobalt target blank is placed on a heating platform with the convex surface facing upward, a stainless steel sheet and an aluminum pad are placed on the convex surface of the cobalt target blank in sequence, and then a 25 kg pressing block is placed at the four corners of the aluminum pad, and then heated at a temperature of 400 ° C and kept warm for 4 hours, and then cooled to room temperature, and then the thread is milled on the welding surface of the cobalt target blank at a feed rate of 0.06 mm and a rotation speed of 450 r / min, and finally cleaned;

[0062] The diameters of the cobalt target blank, the stainless steel sheet and the aluminum spacer are the same;

[0063] The cleaning process includes a first ultrasonic cleaning for 6 minutes, a detergent scrub, a pure water rinse, and a second ultrasonic cleaning for 6 minutes in sequence; the medium used in the first ultrasonic cleaning is a degreasing liquid; the medium used in the second ultrasonic cleaning is an IPA liquid; and the second ultrasonic cleaning is followed by drying for 60 minutes;

[0064] (2) The welding surface of the cobalt target blank after the cleaning treatment in step (1) is subjected to titanium coating treatment to form a titanium film layer with a thickness of 2 μm, and then ultrasonic cleaning is performed for 6 minutes and dried for 60 minutes in sequence, wherein the medium used for ultrasonic cleaning is IPA liquid, to obtain a cobalt target blank after pretreatment.

[0065] Example 3

[0066] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the weight of the compact in step (1) is 10 kg, other conditions are the same as those in Example 1.

[0067] Example 4

[0068] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the weight of the compact in step (1) is 35 kg, other conditions are the same as those in Example 1.

[0069] Example 5

[0070] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the heating temperature in step (1) is 300° C., other conditions are the same as those in Example 1.

[0071] Example 6

[0072] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the heating temperature in step (1) is 700° C., other conditions are the same as those in Example 1.

[0073] Example 7

[0074] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the feed rate of the milling thread in step (1) is 0.03 mm, other conditions are the same as those in Example 1.

[0075] Example 8

[0076] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the feed rate of the milling thread in step (1) is 0.08 mm, other conditions are the same as those in Example 1.

[0077] Example 9

[0078] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the thread pitch in step (1) is 0.5 mm, other conditions are the same as those in Example 1.

[0079] Example 10

[0080] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the thread pitch in step (1) is 1 mm, other conditions are the same as those in Example 1.

[0081] Embodiment 11

[0082] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the thread depth in step (1) is 0.1 mm, other conditions are the same as those in Example 1.

[0083] Example 12

[0084] This embodiment provides a pretreatment method for a cobalt target blank for diffusion welding. Except that the thread depth in step (1) is 0.5 mm, other conditions are the same as those in Example 1.

[0085] Comparative Example 1

[0086] This comparative example provides a method for pre-treating a cobalt target blank for diffusion welding. Except that hot pressing is not performed in step (1), other conditions are the same as those in Example 1.

[0087] Comparative Example 2

[0088] This comparative example provides a method for pre-treating a cobalt target blank for diffusion welding. Except that in step (1), no thread is milled on the welding surface of the cobalt target blank, other conditions are the same as those in Example 1.

[0089] The flatness of the cobalt target blank before milling the thread in step (1) of the above embodiment and comparative example was detected by a ruler; the cobalt target blank obtained in step (2) of the above embodiment and comparative example was diffusion welded to the copper backing plate, and then the welding strength of the welding interface between the cobalt target blank and the copper backing plate obtained in the above embodiment and comparative example was detected by an ultrasonic flaw detector; the results are shown in Table 1.

[0090] The method for diffusion welding the cobalt target blank and the copper back plate is as follows: assemble the cobalt target blank and the copper back plate obtained in step (2) and put them into a sheath, and degas the sheath at a temperature of 300°C for 3 hours, vacuumize the sheath during degassing, and seal the sheath after the degassing is completed; then perform hot isostatic pressing welding at a temperature of 400°C and a pressure of 110MPa for 3 hours.

[0091] Table 1

[0092]

[0093]

[0094] From Table 1, we can see that:

[0095] (1) The pretreatment method provided in Examples 1-2 of the present invention is to first hot-press the cobalt target blank to improve the flatness of the target blank and the uniformity of the coating on the welding surface of the target blank. The flatness of the cobalt target blank is less than 0.1 mm. Then, the thread is milled and the coating is performed on the welding surface of the cobalt target blank in sequence to ensure a good contact area between the cobalt target blank and the back plate, thereby reducing the difficulty of combining the cobalt target blank and the back plate and improving the welding strength between the two. The welding bonding rate of the obtained cobalt target assembly is ≥99% and the welding strength is ≥100 MPa.

[0096] (2) By comparing Example 1 with Example 3, it can be seen that when the weight of the pressing block set during the hot pressing process is too low, the pressure of the hot pressing does not meet the requirements, resulting in a large deformation of the target blank, affecting the thread processing, thereby reducing the welding strength;

[0097] (3) By comparing Example 1 with Examples 5-6, it can be seen that when the heating temperature during the hot pressing process is too low, the stress cannot be released, resulting in a large deformation of the target blank, making it difficult to process the thread, thereby reducing the welding strength; when the heating temperature during the hot pressing process is too high, although it does not affect the welding of the target blank and the backing plate, it increases energy consumption;

[0098] (4) By comparing Example 1 with Examples 7-8, it can be seen that when the feed rate is too low during the thread milling process, the processing efficiency is affected; when the feed rate is too high during the thread milling process, the thread milling process is affected, and the target blank will be severely deformed during the thread milling process;

[0099] (5) From the comparison between Example 1 and Examples 9-10, it can be seen that when the thread pitch obtained by processing is too small, the processing efficiency is affected; when the thread pitch obtained by processing is too large, the welding strength between the cobalt target blank and the back plate is reduced; from the comparison between Example 1 and Examples 11-12, it can be seen that when the thread depth obtained by processing is too shallow, the interlocking depth is insufficient, and the welding strength is improved, but it cannot meet the use requirements; when the thread depth obtained by processing is too deep, although it does not affect the welding between the target blank and the back plate, it affects the processing efficiency, and the processing will be more difficult, affecting the service life of the processing tooling, and the target blank thickness will also be affected;

[0100] (6) From the comparison between Example 1 and Comparative Examples 1-2, it can be seen that when the cobalt target blank is not hot pressed, it is difficult to directly mill the thread on its surface due to the large deformation of the cobalt target blank after the frustum grinding, and it is not conducive to the uniformity of the titanium coating on the welding surface of the cobalt target blank, resulting in a decrease in the welding strength between the cobalt target blank and the back plate; when the thread is not milled on the welding surface of the cobalt target blank and the titanium coating is directly performed, the area of ​​the titanium coating on the welding surface is small, which is not conducive to reducing the difficulty of combining the cobalt target blank and the back plate, resulting in a decrease in the welding strength between the cobalt target blank and the back plate.

[0101] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for pre-treating a cobalt target blank for diffusion welding, characterized in that: The pre-treatment method comprises the following steps: (1) After hot pressing the cobalt target blank, milling threads are performed on the welding surface of the cobalt target blank, and then cleaning is performed; (2) The welding surface of the cobalt target blank after the cleaning treatment in step (1) is subjected to coating treatment, and then ultrasonic cleaning is performed to obtain a cobalt target blank after pretreatment.

2. The pre-treatment method according to claim 1, characterized in that: The hot pressing method in step (1) comprises: placing the cobalt target blank with the convex surface facing upward on a heating platform, then placing a stainless steel sheet and a pad on the convex surface of the cobalt target blank in sequence, and then placing pressing blocks at the four corners of the pad, followed by heating.

3. The pre-treatment method according to claim 2, characterized in that: The diameters of the cobalt target blank, the stainless steel sheet and the spacer block are the same; Preferably, the weight of the briquette is 15-25 kg.

4. The pre-treatment method according to claim 2 or 3, characterized in that: The heating temperature is 400-600°C; Preferably, the heating holding time is 2-4h; Preferably, the heating is followed by cooling to room temperature.

5. The pre-treatment method according to any one of claims 1 to 4, characterized in that: After the hot pressing in step (1), the flatness of the cobalt target blank is less than 0.1 mm.

6. The pre-treatment method according to any one of claims 1 to 5, characterized in that: The feed rate of the milling thread in step (1) is 0.04-0.06mm; Preferably, the rotation speed of the thread milling in step (1) is 450-550 r / min.

7. The pre-treatment method according to any one of claims 1 to 6, characterized in that: After the thread is milled in step (1), the thread pitch of the welding surface of the cobalt target blank is 0.6-0.8 mm, and the thread depth is 0.25-0.35 mm.

8. The pre-treatment method according to any one of claims 1 to 7, characterized in that: The cleaning process in step (1) includes a first ultrasonic cleaning, a detergent scrubbing, a pure water rinse, and a second ultrasonic cleaning performed in sequence; Preferably, the medium used in the first ultrasonic cleaning comprises a degreasing liquid; Preferably, the first ultrasonic cleaning time is 3-10 min; Preferably, the medium used for the second ultrasonic cleaning comprises IPA liquid; Preferably, the second ultrasonic cleaning time is 3-10 min; Preferably, drying is performed after the second ultrasonic cleaning.

9. The pre-treatment method according to any one of claims 1 to 8, characterized in that: The material of the coating in step (2) includes titanium; Preferably, the thickness of the film layer formed after the coating treatment in step (2) is 1-6 μm; Preferably, the medium used for ultrasonic cleaning in step (2) comprises IPA liquid; Preferably, the ultrasonic cleaning time in step (2) is 3-10 min; Preferably, the ultrasonic cleaning in step (2) is followed by drying.

10. The pre-treatment method according to any one of claims 1 to 9, characterized in that: The pre-treatment method comprises the following steps: (1) placing a cobalt target blank with its convex surface facing upward on a heating platform, placing a stainless steel sheet and a pad on the convex surface of the cobalt target blank in sequence, and then placing a 15-25 kg pressed block at the four corners of the pad, and then heating at a temperature of 400-600°C and keeping it warm for 2-4 hours, and then cooling to room temperature, the flatness of the obtained cobalt target blank is less than 0.1 mm, and then milling the thread on the welding surface of the cobalt target blank at a feed rate of 0.04-0.06 mm and a rotation speed of 450-550 r / min, the thread pitch is 0.6-0.8 mm, the thread depth is 0.25-0.35 mm, and finally cleaning is performed; The diameters of the cobalt target blank, the stainless steel sheet and the spacer block are the same; The cleaning process includes a first ultrasonic cleaning, a detergent scrubbing, a pure water rinse, and a second ultrasonic cleaning performed in sequence; the medium used in the first ultrasonic cleaning includes a degreasing liquid; the time of the first ultrasonic cleaning is 3-10 minutes; the medium used in the second ultrasonic cleaning includes an IPA liquid; the time of the second ultrasonic cleaning is 3-10 minutes; and drying is also performed after the second ultrasonic cleaning; (2) The welding surface of the cobalt target blank after the cleaning treatment in step (1) is subjected to a coating treatment, wherein the coating material includes titanium, and the thickness of the film layer is 1-6 μm, and then ultrasonic cleaning is performed for 3-10 minutes and drying is performed in sequence, wherein the medium used for ultrasonic cleaning includes IPA liquid, to obtain a cobalt target blank after pretreatment.

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