Technical Field:

This invention relates particularly to a method for bonding rotating targets.

Background Technology:

Magnetron sputtering is one of the main technologies for preparing thin film materials and is widely used in electronic, optical, optoelectronic, magnetic, and superconducting thin films.

Technical Field:

With the advancement of technology, the coating industry has become a specialized industry, and the target market has further expanded. Sputtering targets are generally of two types: planar targets and rotating targets. Initially, planar targets were used, with a utilization rate of only 20% to 30%. With technological advancement, the transition to rotating targets has gradually begun. Rotating targets continuously rotate during use, resulting in uniform film formation, high stability, and a high yield rate, with a utilization rate of over 80%. Rotating targets do not form "nodules" during use. However, rotating targets cannot be used directly and must be welded to a backing tube. The bonding rate and quality of the target bonding directly affect the target's performance in sputtering. During the sputtering process, if the target tube, backing tube, and indium layer are not properly bonded after bonding, poor electrical conductivity and heat dissipation can occur during sputtering, leading to uneven localized heating, which can easily cause target deflection and even cracking. Unlike flat targets, the rotating target and backing tube are in curved contact. Tube target bonding typically involves heating the rotating target and backing tube, then injecting molten solder into the bonding gap. Rotating target bonding involves brazing multiple sections of the rotating target tube to the backing tube. The longer the target section and the thinner the wall thickness, the more difficult it is to control the uniformity and quality of the casting. Ceramic targets place even higher demands on temperature control. Current rotating target bonding technology typically uses indium as the solder. Specifically, a 0.5-2mm gap is left between the sputtered target cylinder and the stainless steel backing tube. Molten indium fills this gap. After cooling to room temperature, the cylinder and backing tube are bonded together. The indium layer provides both electrical and thermal conductivity. However, the melting point of indium itself is only 156 degrees Celsius. The target material will generate local high temperature during the sputtering process. If the water cooling effect is not timely, the target material is likely to fall off. In addition, when binding valuable metals such as gallium, silver, and gold, the indium layer will actually cause pollution to the contact layer, forming an indium alloy, causing indium pollution. When using indium as a solder for binding the target material, the binding gap will be full of indium. In the final cleaning step of the target material, it is necessary to perform indium hook cleaning. The operation is cumbersome. Once the cleaning is incomplete, indium will be brought into the film as a sputtering source during the sputtering process, causing performance deviation. In view of the shortcomings of the prior art, the present invention provides a method for binding a rotating target material without the need for solder binding. Technical implementation elements: The purpose of the present invention is to provide a method for binding a rotating target material in order to overcome the shortcomings of the prior art. In order to achieve the aforementioned purpose, the present invention adopts the following technical solution. The present invention provides a method for binding a rotating target material, which includes the following steps: heating a rotating target material to be bound, and calculating a specific heating temperature based on the expansion amount of the target material after heating and relevant theories of material mechanics; roughening the rotating target material and a backing tube respectively; heating the rotating target material to a specific temperature so that the rotating target material is in an expanded state, and then putting the rotating target material on the outside of the backing tube within a specified time to form a gap space between the rotating target material and the backing tube; and cooling the rotating target material to room temperature. As a further improvement of the present invention, the step of heating the rotating target to be bound and calculating the specific temperature required for heating based on the expansion amount of the target after heating and the relevant theory of material mechanics is as follows: heating the rotating target and recording the values of the outer diameter and inner diameter of the target after heating to different temperatures; calculating the minimum interference of the rotating target; calculating the maximum interference of the rotating target; determining the range of the inner diameter selection of the rotating target in the expanded state based on the minimum interference and maximum interference of the rotating target, as well as the inner diameter of the target at room temperature and pressure; determining the specific temperature required for heating the rotating target based on the range of the inner diameter selection of the rotating target in the expanded state and the values of the inner diameter after heating to different temperatures. As a further improvement of the present invention, the method for calculating the minimum interference of the rotating target is as follows: calculating the transmitted axial force f; calculating the minimum bonding pressure pmin required to transmit the load; calculating the minimum interference δmin. As a further improvement of the present invention, in the step of calculating the transmitted axial force f, f=mg, where m is the mass of the target and g is the acceleration of gravity. As a further improvement of the present invention, in the step of calculating the minimum bonding pressure pmin required for load transfer, pmin=((f2+(2t÷d)2)0.5)÷(πdlf), wherein t is the transferred torque, d is the nominal diameter, l is the target length, and f is the friction coefficient. As a further improvement of the present invention, in the step of calculating the minimum interference δmin, δmin=pmin×d×(c1÷e1+c2÷e2)×103, wherein c1 is the rigidity coefficient of the backing tube, c2 is the rigidity coefficient of the target material, e1 is the elastic modulus of the backing tube, and e2 is the elastic modulus of the target material. As a further improvement of the present invention, the maximum interference of the rotating target material is calculated as follows: testing the tensile strength rm; calculating the maximum bonding pressure pmax required for load transfer; and calculating the maximum interference δmax. As a further improvement of the present invention, in the step of calculating the maximum bonding pressure pmax required to transfer the load, pmax=((d22-d2)÷(d22+d2))×rm÷a, where d2 is the outer diameter of the target and a is the safety factor. As a further improvement of the present invention, in the step of calculating the maximum interference δmax, δmax=pmax×d×(c1÷e1+c2÷e2)×103. As a further improvement of the present invention, the target material is a copper gallium target. The present invention provides a method for binding a rotating target material, which does not require the use of indium as a solder for binding, can save the corresponding indium consumption, reduce production costs, and can effectively solve the technical problems of indium shedding and indium contamination caused by the use of indium as a solder for binding in the prior art, and can effectively solve the technical problems that the target material bound with indium as a solder will bring indium as a sputtering source into the film during the sputtering process, causing deviations in film performance. Specific implementation methods The technical solution will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention takes the binding of a copper gallium rotating target with a length of 2828mm, an inner diameter of 133mm, an outer diameter of 163mm, and a weight of 80kg as an example. The binding method includes the following steps: heating the rotating target to be bound, and calculating the specific temperature required for heating based on the expansion of the target after heating and the relevant theory of material mechanics. The calculation method is as follows: the copper gallium rotating target is placed on the outside of the backing tube and the backing tube is heated. The copper gallium rotating target can be heated, wherein the outer diameter of the backing tube is 125mm. When the copper gallium rotating target is heated to 25°C, its outer diameter and inner diameter values are recorded, and as the temperature rises, the values at different temperatures are continuously recorded. The outer diameter and inner diameter values of the copper gallium rotating target are obtained until it is heated to 250°C, and the recorded expansion is as follows: Temperature (°C) Outer diameter (mm) Inner diameter (mm) 2516313350163.1133.0855163.13133.1358163.15133.2765163.19133.3180163.24133.3590163.27133.4100163.3133.42250163.5133.55 According to the relevant theories of material mechanics, the transmitted axial force of the copper gallium rotating target is calculated as f=mg=80kg×9.8=784n. Calculate the minimum bonding pressure pmin required to transfer the load = ((f2+(2t÷d)2)0.5)÷(πdlf), where t is the transmission torque, the transmission torque of the target should be 0 when it rotates at a uniform speed, d is the nominal diameter, l is the target length, and f is the friction coefficient. As a further preferred embodiment of the rotating target binding method of the present invention, it is known that the length l of the copper gallium rotating target is 2828 mm, the nominal diameter d is 133 mm, and the friction coefficient f is 0.05. The minimum bonding pressure pmin required to transfer the load can be calculated by the formula = ((f2+(2t÷d)2)0.5)÷(πdlf)=0.0132766 MPa. Calculate the minimum interference δmin=pmin×d×(c1÷e1+c2÷e2)×103, where c1 is the rigidity coefficient of the backing tube and c2 is the rigidity coefficient of the copper gallium rotary target. First, calculate the rigidity coefficient c1 of the backing tube. The formula for calculating the rigidity coefficient of the backing tube is c1=((d2+d12)÷(d2-d12)-μ1), where d is the nominal diameter, d1 is the outer diameter of the backing tube, and μ1 is the poise of the backing tube. Poisson's ratio, given that the nominal diameter d is 133 mm, the outer diameter d1 of the backing tube is 125 mm, and the Poisson's ratio μ1 of the backing tube is 0.247, the stiffness coefficient of the backing tube can be calculated by the formula c1=((d2+d12)÷(d2-d12)-μ1)=15.893; then, the stiffness coefficient c2 of the copper gallium rotating target needs to be calculated. The formula for calculating the stiffness coefficient c2 of the copper gallium rotating target is c2=((d22+d2)÷(d2 2-d2)-μ1), where d is the nominal diameter, d2 is the outer diameter of the copper gallium rotating target, and μ1 is the Poisson's ratio of the copper gallium rotating target. It is known that the nominal diameter d is 133 mm, the outer diameter d2 of the copper gallium rotating target is 163 mm, and the Poisson's ratio μ1 of the copper gallium rotating target is 0.27. The rigidity coefficient of the copper gallium rotating target can be calculated by the formula c2=((d22+d2)÷(d22-d2)-μ1)=4.714; finally, The minimum interference amount is calculated by the formula δmin=pmin×d×(c1÷e1+c2÷e2)×103. It is known that the elastic modulus e1 of the backing tube is 195000 MPa and the elastic modulus e2 of the copper gallium rotary target is 82000 MPa. The minimum interference amount can be calculated by the formula δmin=pmin×d×(c1÷e1+c2÷e2)×103=0.2454314μm. Calculate the maximum bonding pressure pmax required to transfer the load = ((d22-d2)÷(d22+d2))×rm÷a, where d2 is the outer diameter of the target and a is the safety factor. It is known that the outer diameter d2 of the copper-gallium rotating target is 163 mm, the nominal diameter d is 133 mm, and the safety factor a is 3. The tensile strength rm of the copper-gallium rotating target tested by a universal tensile testing machine is 180 MPa. The maximum bonding pressure pmax can be calculated by the formula = ((d22-d2)÷(d22+d2))×rm÷a=12.0385 MPa. The maximum interference amount is calculated as δmax=pmax×d×(c1÷e1+c2÷e2)×103. It is known that the maximum bonding pressure pmax required to transfer the load is 12.0385 MPa, the rigidity coefficient c1 of the backing tube is 15.893, the rigidity coefficient c2 of the copper gallium rotary target is 4.714, the elastic modulus e1 of the backing tube is 195000 MPa, and the elastic modulus e2 of the copper gallium rotary target is 82000 MPa. Therefore, the maximum interference amount δmax=pmax×d×(c1÷e1+c2÷e2)×103=222.5446 μm can be calculated. Through theoretical calculation, the interference is between 0.00024543mm and 0.2225446mm. Since the economic processing accuracy is 0.05mm, the actual interference should be between 0.05mm and 0.222mm. For the copper gallium rotary target with an ideal inner diameter of 133mm, the actual inner diameter of the copper gallium rotary target after heating should be between 133.1 and 133.444mm. After taking the average value, it can be concluded that the actual inner diameter of the copper gallium rotary target after heating is 133.272mm. According to the recorded expansion, it can be concluded that the specific heating temperature should be 60℃. After reaching a specific temperature of 60°C, the rotating target and the backing tube are roughened separately, and then the rotating target is heated to 60°C to expand the rotating target. Then, the rotating target is placed on the outside of the backing tube within a specified time to form a gap space between the rotating target and the backing tube. Finally, the rotating target is cooled to room temperature to complete the target binding, wherein the specified time is 5 minutes. The present invention provides a rotating target binding method that does not require the use of indium as a solder for binding, which can save the corresponding indium consumption and reduce production costs. It can effectively solve the technical problems of indium shedding and indium contamination caused by the use of indium as a solder for binding in the prior art, and can effectively solve the technical problems such as the use of indium as a solder for binding and the use of indium as a sputtering source into the thin film during the sputtering process, causing deviations in the film performance. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will recognize that various improvements, additions, and substitutions are possible without departing from the scope and spirit of the invention disclosed by the appended claims.