A process method for improving the bonding performance of a thermal evaporation tin oxide electrothermal film

Abstract

The present invention discloses a process method for improving the bonding performance of a thermally evaporated tin oxide electrothermal film, belonging to the technical field of thin film preparation. The feature of this method is to add an auxiliary tube with the same diameter as the tube to be evaporated at both the upper and lower ends of the tube to be evaporated, and the length of the auxiliary tube is in a certain proportion to the length of the tube to be evaporated; and the tin oxide thin film is evaporated in a way of high temperature first and then low temperature. The present invention uses the method of parallel operation of the auxiliary tube process and the high-low temperature evaporation process, significantly improving the bonding performance of the thermally evaporated tin oxide electrothermal film and ensuring the power stability of the tin oxide electrothermal film during use.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film preparation, and particularly relates to a process method for improving the bonding performance of a thermally evaporated tin oxide electrothermal film. Background Art

[0002] Doped tin oxide (SnO2) is an important semiconductor material. Due to its transparent and conductive properties, nano-tin oxide thin films have been widely used in fields such as sensors, solar cells, and electric heating tubes. The existing preparation processes for nano-tin oxide electrothermal films mainly include spray pyrolysis, thermal evaporation, and magnetron sputtering. Among them, the thermal evaporation method is a low-cost and high-efficiency production method. However, there are two deficiencies in depositing thin films on the inner wall of pipe fittings by the thermal evaporation method. First, there are significant differences in the film resistance at different parts of the pipe fitting, which easily generates thermal stress during operation and affects the bonding performance of the electrothermal film. Second, the obtained tin oxide crystal grains have large sizes and large inter-grain pores at the current evaporation temperature of the tin oxide electrothermal film, resulting in poor bonding performance and being prone to peeling off under the action of thermal stress. Under the combined influence of these two factors, the heating power of the electrothermal film declines to a certain extent with the extension of the service time. To solve this problem, the present invention provides a process method for improving the bonding performance of a thermally evaporated tin oxide electrothermal film. Summary of the Invention

[0003] Object of the Invention: In order to ensure the resistance uniformity in the length direction of the tubular tin oxide electrothermal film and avoid the generation of thermal stress, and at the same time to prevent the tin oxide electrothermal film from peeling off due to poor inter-grain bonding performance, the present invention provides a process method in which an auxiliary tube process and a high-low temperature evaporation process are carried out in parallel, in order to improve the bonding performance of the thermally evaporated tin oxide electrothermal film and ensure the power stability of the tin oxide electrothermal film during use.

[0004] To achieve the above object of the invention, the present invention adopts the following technical solutions:

[0005] A process method for improving the bonding performance of a thermally evaporated tin oxide electrothermal film, comprising the following steps:

[0006] (1) Add a section of auxiliary tube with the same diameter as the tube to be evaporated at both the upper and lower ends of the tube to be evaporated;

[0007] (2) Evaporate a layer of tin oxide when the temperature in the coating area is relatively high;

[0008] (3) Evaporate another layer of tin oxide when the temperature in the coating area is relatively low.

[0009] The lower end of the lower auxiliary tube described in step 1 is 1-3 cm away from the outlet of the evaporation source, the length of the lower auxiliary tube accounts for 1 / 10-1 / 5 of the length of the tube to be evaporated, and the length of the upper auxiliary tube accounts for 1 / 4-1 / 3 of the length of the tube to be evaporated.

[0010] The temperature of the coating area described in Step 2 is 490°C to 550°C.

[0011] The temperature of the coating area described in Step 3 is 450 - 480°C.

[0012] Invention mechanism: After depositing an indium tin oxide thin film on the inner wall of the pipe fitting by thermal evaporation, usually the film resistance uniformity in the middle section is good, while the film resistance difference at both ends of the pipe fitting is large. To ensure the uniformity of the film resistance at each part of the pipe fitting to be coated at different distances from the evaporation source, by setting upper and lower auxiliary pipes, the two ends with large film resistance differences are located in the auxiliary pipe area, and the uniform section of the film resistance of the pipe fitting is exactly located in the area of the pipe fitting to be coated. Since the evaporation method mainly uses the way of steam running from bottom to top and the kinetic energy of the steam is limited, if the auxiliary pipe is too long, it is difficult to evenly distribute the steam volume to the uppermost area. Therefore, the auxiliary pipe also needs to be set to an appropriate length. Through a large number of experiments, the proportional relationship between the length of the auxiliary pipe and the length of the pipe fitting to be coated is obtained, so as to ensure the uniformity of the film resistance in the area of the pipe fitting to be coated and greatly reduce the thermal stress inside the film. On the other hand, according to a large number of previous experiments, it is found that the bonding performance of the nano-film is also affected by the grain size. The higher the coating temperature, the larger the grain size, the larger the pores between the grains, and the bonding performance between the grains is greatly weakened. Under the action of thermal stress or external force, the grains are likely to fall off, resulting in an increase in film resistance and a decrease in power. However, a thin film with a low coating temperature, small grain size and tight bonding has problems of high resistance and low power. Therefore, the present invention first deposits a nano-indium tin oxide thin film with a large grain size and pore size at a higher temperature, and then deposits a thin film of indium tin oxide with smaller grains at a lower temperature. The smaller indium tin oxide grains are filled between the large grains, thereby improving the bonding performance between the grains.

[0013] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows in three aspects. First, to improve the resistance uniformity of the pipe fitting in the length direction, the prior art needs to turn the pipe fitting 180° during the coating process, that is, two-way evaporation; the present invention does not need to turn the pipe fitting and only needs one-way evaporation, which simplifies the operation and improves the production efficiency. Second, for pipe fittings with a large length, the resistance uniformity in the length direction of the prior art is still low, while the present invention can significantly improve the resistance uniformity of longer pipe fittings. Third, the thermal evaporation indium tin oxide electrothermal film obtained by the present invention has good bonding performance, which is significantly better than the bonding performance of the film under the prior art. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of evaporation;

[0015] Figure 2 It is a scanning electron microscope morphology diagram of the indium tin oxide thin film at an evaporation temperature of 460°C before and after being wiped with a cotton ball;

[0016] Figure 3 Scanning electron microscope morphology diagrams of the tin oxide film at a vapor deposition temperature of 510 °C before and after being wiped with a cotton ball;

[0017] Figure 4 Scanning electron microscope morphology diagrams of the tin oxide films with vapor deposition temperatures of 510 °C and 460 °C respectively before and after being wiped with a cotton ball. Specific implementation manners

[0018] The present invention will be further described below in conjunction with the accompanying drawings, specific comparative examples and examples.

[0019] A process method for improving the bonding performance of a thermally vapor-deposited tin oxide electrothermal film, comprising the following steps:

[0020] (1) Add a section of auxiliary tube with the same diameter as the tube to be vapor-deposited at both the upper and lower ends of the tube to be vapor-deposited;

[0021] (2) Vapor-deposit a layer of tin oxide when the temperature in the coating area is relatively high;

[0022] (3) Vapor-deposit another layer of tin oxide when the temperature in the coating area is relatively low.

[0023] The lower end of the lower auxiliary tube described in step 1 is 1-3 cm away from the outlet of the evaporation source, the length of the lower auxiliary tube accounts for 1 / 10-1 / 5 of the length of the tube to be vapor-deposited, and the length of the upper auxiliary tube accounts for 1 / 4-1 / 3 of the length of the tube to be vapor-deposited.

[0024] The temperature in the coating area described in step 2 is 490 °C - 550 °C.

[0025] The temperature in the coating area described in step 3 is 450 - 480 °C.

[0026] The tin oxide electrothermal film plated by using the process method of the present invention has significantly higher resistance uniformity and bonding performance in the length direction than the conventional process method, and the production efficiency is also improved.

[0027] Comparative example 1

[0028] The diameter of the quartz tube is 3.5 cm and the length is 40 cm. After plating a tin oxide film by using a conventional vapor deposition process, the sheet resistance at four points 0, (1 / 3)l, (2 / 3)l, and l (l is the length of the pipe fitting) from the lower end of the quartz tube is measured, and the four test points are on the same straight line. And the uniformity (the difference between the maximum and minimum resistances / the average value of the maximum and minimum resistances) is calculated, and the uniformity value is 23.3%, as shown in Table 1.

[0029] Example 1

[0030] The diameter of the quartz tube is 3.5 cm and the length is 40 cm. The tin oxide film is deposited by using the process method described in the present invention. The lower end of the lower auxiliary tube is 2 cm away from the outlet of the evaporation source, the length of the lower auxiliary tube is 4 cm, and the length of the upper auxiliary tube is 10 cm. The sheet resistance of four points at 0, (1 / 3)l, (2 / 3)l, and l from the lower end of the quartz tube is measured, and the uniformity is calculated to be 16.1%, as shown in Table 1. It can be seen that compared with Comparative Example 1 of the conventional evaporation coating process, the resistance uniformity of the tin oxide film pipe fittings deposited by the present invention is significantly improved.

[0031] Table 1 Sheet resistance values and uniformity at equally spaced test points of the electrothermal film (l is the length of the pipe fitting)

[0032]

[0033] Comparative Example 2

[0034] The diameter of the quartz tube is 3.5 cm and the length is 50 cm. After depositing the tin oxide film by using the conventional evaporation coating process, the sheet resistance of four points at 0, (1 / 3)l, (2 / 3)l, and l from the lower end of the quartz tube is measured, and the uniformity is calculated to be 40.0%, as shown in Table 1. Compared with Comparative Example 1, it can be seen that the longer the length of the pipe fitting, the worse the resistance uniformity.

[0035] Example 2

[0036] The diameter of the quartz tube is 3.5 cm and the length is 50 cm. The tin oxide film is deposited by using the process method described in the present invention. The lower end of the lower auxiliary tube is 1 cm away from the outlet of the evaporation source, the length of the lower auxiliary tube is 7 cm, and the length of the upper auxiliary tube is 13 cm. The sheet resistance of four points at 0, (1 / 3)l, (2 / 3)l, and l from the lower end of the quartz tube is measured, and the uniformity is calculated to be 15.1%, as shown in Table 1. It can be seen that compared with Comparative Example 2 of the conventional evaporation coating process, the resistance uniformity of the tin oxide film pipe fittings deposited by the present invention, especially for longer pipe fittings, has a particularly significant improvement effect.

[0037] Example 3

[0038] Adopt the auxiliary tube process in the process method of the present invention, and set the temperature of the coating area to 460 °C and 510 °C respectively for depositing the tin oxide film. After the obtained electrothermal film is subjected to crystallization heat treatment, a cotton ball with a diameter of 1 cm is used to wipe the film 10 times in the same direction under a pressure of 40 g, and the surface morphology is observed by using a scanning electron microscope, as Figure 2 、 Figure 3 shown. Among them, (a) and (c) are the low-magnification surface morphologies before and after wiping, and (b) and (d) are the high-magnification surface morphologies before and after wiping. The black dots in the scanning electron microscope images are the small pits left after the grains fall off. Comparing Figure 2 and Figure 3 it is found that Figure 2The grain shedding in Figure 3 is slight, while the grain shedding in Figure 3 is severe and the size of the shedding pits is large. It can be seen from this that the lower the evaporation temperature, the better the bonding performance of the prepared thin film. However, the grains of the thin film prepared at a lower temperature are small and the resistance is large. In order to maintain a low resistance while improving the bonding performance of the thin film, the auxiliary tube process and the high-low temperature evaporation process of the present invention are adopted, that is, the first layer of tin oxide thin film is deposited at 510 °C first, and then the second layer of tin oxide thin film is deposited at 460 °C. The same cotton ball wiping test is carried out under the same conditions, and the surface morphology measured by scanning electron microscopy is as shown in Figure 4 . (a) and (c) are the low-magnification surface morphologies before and after wiping, and (b) and (d) are the high-magnification surface morphologies before and after wiping. Comparing with the surface morphology in Figure 3 , it can be seen that the shedding situation has been greatly alleviated. Therefore, the bonding performance of the tin oxide thin film deposited by the high-low temperature evaporation process is significantly improved.

[0039] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. The present invention is not limited to the above examples either. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle scope of the present invention shall fall within the scope of the claims of the present invention.

Claims

1. A process method for improving the bonding performance of a thermal evaporation tin oxide electrothermal film, characterized in that, The process method includes the following steps: (1) Add a section of auxiliary tube with the same diameter as the tube to be vapor-deposited at both the upper and lower ends of the tube to be vapor-deposited; the lower end of the lower auxiliary tube is 1-3 cm away from the evaporation source outlet, the length of the lower auxiliary tube accounts for 1 / 10-1 / 5 of the length of the tube to be vapor-deposited, and the length of the upper auxiliary tube accounts for 1 / 4-1 / 3 of the length of the tube to be vapor-deposited; (2) Vapor-deposit a layer of tin oxide at a temperature of 490-550 °C in the coating area; (3) Vapor-deposit another layer of tin oxide at a temperature of 450-480 °C in the coating area.

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