A method for leveling a magnetron sputtering tray

Abstract

The present invention relates to a method for leveling a magnetron sputtering tray, the method comprising: assembling a deformed magnetron sputtering tray with a protective pad, and then sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment, and cooling; the first hot pressing treatment is a constant temperature and constant pressure process; the second hot pressing treatment is a variable temperature and constant pressure process, and the heating rate is 2‑5°C / min; the third hot pressing treatment is a constant temperature and variable pressure process, and the pressure reduction rate is 10‑20N / min. The leveling method provided by the present invention realizes efficient leveling of the magnetron sputtering tray by designing the leveling process, and the flatness after leveling can reach the original level, and the service life is further improved compared with the original magnetron sputtering tray.

Description

Technical Field

[0001] The invention relates to the field of material processing, and in particular to a method for leveling a magnetron sputtering tray. Background Art

[0002] At present, the working principle of magnetron sputtering is that electrons collide with argon atoms in the process of flying to the substrate under the action of the electric field E, ionizing them to produce Ar positive ions and new electrons; the new electrons fly to the substrate, and the Ar ions are accelerated to fly to the cathode target under the action of the electric field, and bombard the target surface with high energy, causing the target material to sputter. Among the sputtered particles, neutral target atoms or molecules are deposited on the substrate to form a thin film, and the secondary electrons generated will be affected by the electric field and magnetic field, resulting in a drift in the direction indicated by E (electric field) × B (magnetic field), referred to as E × B drift, and its motion trajectory is similar to a cycloid. If it is a circular magnetic field, the electrons will move in a circular motion on the target surface in an approximate cycloid form. Their motion path is not only very long, but also bound in the plasma region close to the target surface, and a large amount of Ar is ionized in this region to bombard the target material, thereby achieving a high deposition rate. As the number of collisions increases, the energy of the secondary electrons is exhausted, gradually moving away from the target surface, and finally deposited on the substrate under the action of the electric field E.

[0003] For example, CN114250439A discloses a magnetron sputtering method, which is applied to a magnetron sputtering process using a magnetron sputtering device, wherein the magnetron sputtering device includes a magnet group located above or below a target material, wherein the magnet group includes a first magnet and a second magnet, and the method includes: in the first stage of the life cycle of the target material, the distance between the first magnet and the second magnet is a first distance for magnetron sputtering process; in the second stage of the life cycle of the target material, the distance between the first magnet and the second magnet is a second distance for magnetron sputtering process, wherein the first distance and the second distance are the distances between the first magnet and the second magnet in the lateral direction, and the first distance and the second distance are different. This scheme widens the area of ​​the deepest etching region of the target material by adjusting the relative positions between the magnets in stages during the life cycle of the target material, improves the utilization rate of the target material under the premise of keeping the safety margin unchanged, and thus reduces the production cost.

[0004] CN114774871A discloses a magnetron sputtering device and a magnetron sputtering film forming method, including a first cathode assembly and a second cathode assembly arranged oppositely. When the magnetron sputtering device provided in the embodiment of the present application is used to form a cathode, the direction of the magnetic field can be adjusted to control the area where plasma is formed, and the plasma is limited to be formed between the first rotating target and the second rotating target. Then, the area where the rotating target is bombarded with process gas Ar is limited to the relative position of the rotating target. Therefore, the small particles of high-energy Ag and IZO bombarded out will not be deposited on the device, and only the small particles of low-energy Ag and IZO close to the vertical direction will be deposited on the device to form a cathode, thereby reducing the damage to the organic functional layer during the cathode formation process and improving the yield of the organic light-emitting diode display device.

[0005] In magnetron sputtering, a substrate tray is usually used to carry the substrate to be sputtered and adsorb metal atoms other than those deposited on the substrate. Due to its use environment and requirements, the magnetron sputtering tray used for sputtering needs to adsorb excess metal particles, so the tray needs to be sandblasted. Due to the high surface roughness requirements, sandblasting needs to be performed with a high pressure, and the tray is thin and the strength of the aluminum alloy is not high, which will cause the tray to be significantly deformed after repeated use. In the prior art, it is usually leveled only by a single flattening method, and the leveling effect is poor, and it is difficult to meet the flatness requirements for use. Moreover, after leveling by only a single flattening method, the service life is significantly lower than that of the original tray, and the frequency of leveling is significantly increased, resulting in a significant increase in production costs and a significant decrease in efficiency. Summary of the invention

[0006] In view of the problems existing in the prior art, an object of the present invention is to provide a method for leveling a magnetron sputtering tray, so as to solve the problems existing in the prior art in leveling the magnetron sputtering tray, namely, poor leveling effect and shortened service life after leveling.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for leveling a magnetron sputtering tray, the method comprising: assembling a deformed magnetron sputtering tray with a protective pad, and then sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment, and cooling;

[0009] The first hot pressing treatment is a constant temperature and constant pressure process;

[0010] The second hot pressing treatment is a variable temperature constant pressure process, and the heating rate is 2-5°C / min;

[0011] The third hot pressing treatment is a constant temperature and pressure changing process, and the pressure reduction rate is 10-20N / min.

[0012] The leveling method provided by the present invention realizes efficient leveling of the magnetron sputtering tray by designing the leveling process. The flatness after leveling can reach the original level, and the service life is further improved compared with the original magnetron sputtering tray.

[0013] In the present invention, the magnetron sputtering tray is a platform for carrying the sample to be sputtered in magnetron sputtering. The material can be aluminum alloy or other metal materials or non-metal materials commonly used in the field. The deformation is the deformation caused by the tray being used after roughening sandblasting. The material can be aluminum alloy, etc., which is a conventional item used in the field of magnetron sputtering. It meets the reasons for the deformation problem in the present invention and can adopt the leveling method of the present invention.

[0014] In the present invention, the protective pad can be a commonly used protective material in the art such as a silicone pad to avoid damage to the magnetron sputtering tray during the leveling process and ensure uniform distribution of pressure during the leveling process.

[0015] In the present invention, the second hot pressing treatment is a variable temperature and constant pressure process, and the heating rate is 2-5°C / min, for example, it can be 2°C / min, 2.2°C / min, 2.4°C / min, 2.6°C / min, 2.8°C / min, 3°C / min, 3.2°C / min, 3.4°C / min, 3.6°C / min, 3.8°C / min, 4°C / min, 4.2°C / min, 4.4°C / min, 4.6°C / min, 4.8°C / min or 5°C / min, etc., but is not limited to the listed values, and other values ​​not listed in this range are also applicable.

[0016] In the present invention, the third hot pressing treatment is a constant temperature and pressure change process, and the pressure reduction rate is 10-20N / min, for example, it can be 10N / min, 10.5N / min, 11N / min, 11.5N / min, 12N / min, 12.5N / min, 13N / min, 13.5N / min, 14N / min, 14.5N / min, 15N / min, 15.5N / min, 16N / min, 16.5N / min, 17N / min, 17.5N / min, 18N / min, 18.5N / min, 19N / min, 19.5N / min or 20N / min, but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0017] As a preferred technical solution of the present invention, the pressurization method in the leveling method is mechanical pressurization or gas pressurization.

[0018] As a preferred technical solution of the present invention, the temperature of the first hot pressing treatment is 100-150°C, for example, it can be 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, 118°C, 120°C, 124°C, 126°C, 128°C, 130°C, 132°C, 134°C, 136°C, 138°C, 140°C, 142°C, 144°C, 146°C, 148°C or 150°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0019] Preferably, the pressure of the first hot pressing treatment is 300-400N, for example, it can be 300N, 305N, 310N, 315N, 320N, 325N, 330N, 335N, 340N, 345N, 350N, 355N, 360N, 365N, 370N, 375N, 380N, 385N, 390N, 395N or 400N, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0020] As a preferred technical solution of the present invention, the time for the first hot pressing treatment is 30-60min, for example, it can be 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min, 40min, 41min, 42min, 43min, 44min, 45min, 46min, 47min, 48min, 49min, 50min, 51min, 52min, 53min, 54min, 55min, 56min, 57min, 58min, 59min or 60min, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0021] As a preferred technical solution of the present invention, the starting temperature of the second heat treatment is 180-200°C, for example, it can be 180°C, 181°C, 182°C, 183°C, 184°C, 185°C, 186°C, 187°C, 188°C, 189°C, 190°C, 191°C, 192°C, 193°C, 194°C, 195°C, 196°C, 197°C, 198°C, 199°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0022] In the present invention, the temperature can be directly increased after reaching the starting temperature of the second heat treatment on the basis of the first heat treatment. The specific heating rate has no effect on the effect of the present invention, but it should be ensured that the starting temperature of the second heat treatment in the present invention is reached, and then the variable temperature and constant pressure process of the second hot pressing treatment is carried out for a certain time at a limited heating rate of 2-5°C / min.

[0023] Preferably, the pressure of the second heat treatment is 100-200N, for example, it can be 100N, 105N, 110N, 115N, 120N, 125N, 130N, 135N, 140N, 145N, 150N, 155N, 160N, 165N, 170N, 175N, 180N, 185N, 190N, 195N or 200N, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0024] As a preferred technical solution of the present invention, the time for the second heat treatment is 10-15min, for example, it can be 10min, 10.2min, 10.4min, 10.6min, 10.8min, 11min, 11.2min, 11.4min, 11.6min, 11.8min, 12min, 12.2min, 12.4min, 12.6min, 12.8min, 13min, 13.2min, 13.4min, 13.6min, 13.8min, 14min, 14.2min, 14.4min, 14.6min, 14.8min or 15min, but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0025] As a preferred technical solution of the present invention, the temperature of the third heat treatment is 200-250°C, for example, it can be 200°C, 202°C, 204°C, 206°C, 208°C, 210°C, 212°C, 214°C, 216°C, 218°C, 220°C, 222°C, 224°C, 226°C, 228°C, 230°C, 232°C, 234°C, 236°C, 238°C, 240°C, 242°C, 244°C, 246°C, 248°C or 250°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0026] Preferably, the starting pressure of the third heat treatment is 800-900N, for example, it can be 800N, 805N, 810N, 815N, 820N, 825N, 830N, 835N, 840N, 845N, 850N, 855N, 860N, 865N, 870N, 875N, 880N, 885N, 890N, 895N or 900N, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0027] In the present invention, the initial pressure of the third heat treatment can be directly pressurized on the basis of the second heat treatment. The specific pressurization rate has no effect on the effect of the present invention, but it should be ensured that the initial pressure of the third heat treatment in the present invention is reached, and then the constant temperature pressure change process of the third heat treatment is carried out within a certain time range at a limited pressure reduction rate of 10-20N / min.

[0028] As a preferred technical solution of the present invention, the time for the third treatment is 10-20min, for example, it can be 10min, 10.5min, 11min, 11.5min, 12min, 12.5min, 13min, 13.5min, 14min, 14.5min, 15min, 15.5min, 16min, 16.5min, 17min, 17.5min, 18min, 18.5min, 19min, 19.5min or 20min, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0029] As a preferred technical solution of the present invention, the cooling method is air cooling.

[0030] Preferably, the endpoint temperature of the air cooling is 20-30°C, for example, it can be 20°C, 20.5°C, 21°C, 21.5°C, 22°C, 22.5°C, 23°C, 23.5°C, 24°C, 24.5°C, 25°C, 25.5°C, 26°C, 26.5°C, 27°C, 27.5°C, 28°C, 28.5°C, 29°C, 29.5°C or 30°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] As a preferred technical solution of the present invention, the leveling method comprises: assembling the deformed magnetron sputtering tray and the protection pad, and then sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment and cooling;

[0032] The pressurization method in the leveling method is mechanical pressurization or gas pressurization;

[0033] The first hot pressing treatment is a constant temperature and constant pressure process; the temperature of the first hot pressing treatment is 100-150°C; the pressure of the first hot pressing treatment is 300-400N; the time of the first hot pressing treatment is 30-60min;

[0034] The second heat pressing treatment is a variable temperature constant pressure process, and the heating rate is 2-5°C / min; the starting temperature of the second heat treatment is 180-200°C; the pressure of the second heat treatment is 100-200N; the time of the second heat treatment is 10-15min;

[0035] The third heat pressing treatment is a constant temperature and pressure changing process, and the pressure reduction rate is 10-20N / min; the temperature of the third heat treatment is 200-250°C; the starting pressure of the third heat treatment is 800-900N; the time of the third treatment is 10-20min;

[0036] The cooling method is air cooling; the terminal temperature of the air cooling is 20-30°C.

[0037] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0038] The leveling method provided by the present invention adopts a specific heat treatment process, combines external pressure and heating means, adopts a specific three-stage treatment, and adopts a combination of constant pressure, constant temperature, variable pressure and variable temperature in a specific stage to achieve efficient leveling of the magnetron sputtering tray. The service life of the leveled magnetron sputtering tray is 1-1.5 times that of the original magnetron sputtering tray, which significantly reduces the frequency of leveling and is conducive to improving production efficiency. DETAILED DESCRIPTION

[0039] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0040] Example 1

[0041] This embodiment provides a method for leveling a magnetron sputtering tray, the method comprising: assembling a deformed magnetron sputtering tray with a protective pad, and then sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment, and cooling;

[0042] The pressurization method in the leveling method is mechanical pressurization, using a certain weight of a pressing block to apply pressure, such as a pressing block with a weight of 10 kg, and using a rigid plate to ensure uniform pressure application, such as a thin steel plate;

[0043] The first hot pressing treatment is a constant temperature and constant pressure process; the temperature of the first hot pressing treatment is 125°C; the pressure of the first hot pressing treatment is 350N; the time of the first hot pressing treatment is 45min;

[0044] The second heat pressing treatment is a variable temperature constant pressure process, and the heating rate is 3°C / min; the starting temperature of the second heat treatment is 190°C; the pressure of the second heat treatment is 150N; the time of the second heat treatment is 12min;

[0045] The third heat pressing treatment is a constant temperature and pressure change process, and the pressure reduction rate is 15N / min; the temperature of the third heat treatment is 220°C; the starting pressure of the third heat treatment is 850N; and the time of the third treatment is 15min;

[0046] The cooling method is air cooling; the end temperature of the air cooling is 25°C.

[0047] The flatness and secondary service life of the pallet after leveling are detailed in Table 1.

[0048] Example 2

[0049] This embodiment provides a method for leveling a magnetron sputtering tray, the method comprising: assembling a deformed magnetron sputtering tray with a protective pad, and then sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment, and cooling;

[0050] The pressurization method in the leveling method is gas pressurization, that is, it can be carried out in a hot isostatic pressing device;

[0051] The first hot pressing treatment is a constant temperature and constant pressure process; the temperature of the first hot pressing treatment is 100° C.; the pressure of the first hot pressing treatment is 400N; and the time of the first hot pressing treatment is 60 minutes;

[0052] The second heat pressing treatment is a variable temperature constant pressure process, and the heating rate is 5°C / min; the starting temperature of the second heat treatment is 200°C; the pressure of the second heat treatment is 100N; the time of the second heat treatment is 10min;

[0053] The third heat pressing treatment is a constant temperature and pressure changing process, and the pressure reduction rate is 10N / min; the temperature of the third heat treatment is 250°C; the starting pressure of the third heat treatment is 800N; and the time of the third treatment is 20min;

[0054] The cooling method is air cooling; the end temperature of the air cooling is 20°C.

[0055] The flatness and secondary service life of the pallet after leveling are detailed in Table 1.

[0056] Example 3

[0057] This embodiment provides a method for leveling a magnetron sputtering tray, the method comprising: assembling a deformed magnetron sputtering tray with a protective pad, and then sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment, and cooling;

[0058] The pressurization method in the leveling method is mechanical pressurization, using a certain weight of a pressing block to apply pressure, such as a pressing block with a weight of 10 kg, and using a rigid plate to ensure uniform pressure application, such as a thin steel plate;

[0059] The first hot pressing treatment is a constant temperature and constant pressure process; the temperature of the first hot pressing treatment is 150°C; the pressure of the first hot pressing treatment is 300N; the time of the first hot pressing treatment is 30min;

[0060] The second heat pressing treatment is a variable temperature and constant pressure process, and the heating rate is 2°C / min; the starting temperature of the second heat treatment is 180°C; the pressure of the second heat treatment is 200N; the time of the second heat treatment is 15min;

[0061] The third heat pressing treatment is a constant temperature and pressure change process, and the pressure reduction rate is 20N / min; the temperature of the third heat treatment is 200°C; the starting pressure of the third heat treatment is 900N; and the time of the third treatment is 10min;

[0062] The cooling method is air cooling; the end temperature of the air cooling is 30°C.

[0063] The flatness and secondary service life of the pallet after leveling are detailed in Table 1.

[0064] Example 4

[0065] This embodiment provides a method for leveling a magnetron sputtering tray, the method comprising: assembling a deformed magnetron sputtering tray with a protective pad, and then sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment, and cooling;

[0066] The pressurization method in the leveling method is mechanical pressurization, using a certain weight of a pressing block to apply pressure, such as a pressing block with a weight of 10 kg, and using a rigid plate to ensure uniform pressure application, such as a thin steel plate;

[0067] The first hot pressing treatment is a constant temperature and constant pressure process; the temperature of the first hot pressing treatment is 130°C; the pressure of the first hot pressing treatment is 330N; the time of the first hot pressing treatment is 50min;

[0068] The second heat pressing treatment is a variable temperature and constant pressure process, and the heating rate is 4°C / min; the starting temperature of the second heat treatment is 185°C; the pressure of the second heat treatment is 175N; the time of the second heat treatment is 13min;

[0069] The third heat pressing treatment is a constant temperature and pressure change process, and the pressure reduction rate is 17N / min; the temperature of the third heat treatment is 240°C; the starting pressure of the third heat treatment is 820N; the time of the third treatment is 18min;

[0070] The cooling method is air cooling; the end temperature of the air cooling is 25°C.

[0071] The flatness and secondary service life of the pallet after leveling are detailed in Table 1.

[0072] Comparative Example 1

[0073] The only difference from Example 1 is that the first hot pressing treatment is not performed. The flatness and secondary service life of the tray after completion are shown in Table 1.

[0074] Comparative Example 2

[0075] The only difference from Example 1 is that the second hot pressing treatment is not performed. The flatness and secondary service life of the tray after completion are shown in Table 1.

[0076] Comparative Example 3

[0077] The only difference from Example 1 is that the third hot pressing treatment is not performed. The flatness and secondary service life of the tray after completion are shown in Table 1.

[0078] Comparative Example 4

[0079] The only difference from Example 1 is that the second heat treatment is performed at a constant temperature of 199° C. The flatness and secondary service life of the tray after the treatment are shown in Table 1.

[0080] Comparative Example 5

[0081] The only difference from Example 1 is that the second heat treatment is carried out at a variable temperature with a cooling rate of 3°C / min. The flatness and secondary service life of the tray after completion are shown in Table 1.

[0082] Comparative Example 6

[0083] The only difference from Example 1 is that the third heat treatment is performed under a constant pressure of 800 N. The flatness and secondary service life of the tray after completion are shown in Table 1.

[0084] The material used for the magnetron sputtering tray in the above embodiments and comparative examples is aluminum alloy (AA6061). This is only for illustrative purposes to illustrate the effect of the present invention, and is not limited to the aluminum alloy grades cited above. Other materials used for the magnetron sputtering tray may also be used.

[0085] Table 1

[0086] Flatness / mm Second life Example 1 1mm Same service life as the original pallet Example 2 1.5mm 1.1 times the service life of the original pallet Example 3 1.2mm 1.2 times the service life of the original pallet Example 4 1.3mm 1.1 times the service life of the original pallet Comparative Example 1 2mm 0.8 times the service life of the original pallet Comparative Example 2 1.9mm 0.6 times the service life of the original pallet Comparative Example 3 1.8mm 0.7 times the service life of the original pallet Comparative Example 4 2.1mm 0.5 times the service life of the original pallet Comparative Example 5 1.7mm 0.6 times the service life of the original pallet Comparative Example 6 1.6mm 0.4 times the service life of the original pallet

[0087] It can be seen from the results of the above embodiments and comparative examples that the leveling method provided by the present invention, through the design of the leveling process, realizes efficient leveling of the magnetron sputtering tray. The flatness after leveling can reach the original level, and the service life is further improved compared with the original magnetron sputtering tray.

[0088] It is stated that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above 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.

[0089] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0091] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for leveling a magnetron sputtering tray, characterized in that: The leveling method comprises: assembling the deformed magnetron sputtering tray and the protection pad and sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment and cooling; The first hot pressing treatment is a constant temperature and constant pressure process; the temperature of the first hot pressing treatment is 100-150°C; the pressure of the first hot pressing treatment is 300-400N; the time of the first hot pressing treatment is 30-60min; The second heat pressing treatment is a variable temperature constant pressure process, and the heating rate is 2-5°C / min; the starting temperature of the second heat treatment is 180-200°C; the pressure of the second heat treatment is 100-200N; the time of the second heat treatment is 10-15min; The third hot pressing treatment is a constant temperature pressure change process, and the pressure reduction rate is 10-20N / min; the temperature of the third heat treatment is 200-250°C; the starting pressure of the third heat treatment is 800-900N; and the time of the third treatment is 10-20min.

2. The leveling method according to claim 1, characterized in that: The pressurization method in the leveling method is mechanical pressurization or gas pressurization.

3. The leveling method according to claim 1, characterized in that: The cooling method is air cooling.

4. The leveling method according to claim 3, characterized in that: The end point temperature of the air cooling is 20-30°C.

5. The leveling method according to claim 1, characterized in that: The leveling method comprises: assembling the deformed magnetron sputtering tray and the protection pad and sequentially performing a first hot pressing treatment, a second hot pressing treatment, a third hot pressing treatment and cooling; The pressurization method in the leveling method is mechanical pressurization or gas pressurization; The first hot pressing treatment is a constant temperature and constant pressure process; the temperature of the first hot pressing treatment is 100-150°C; the pressure of the first hot pressing treatment is 300-400N; the time of the first hot pressing treatment is 30-60min; The second heat pressing treatment is a variable temperature constant pressure process, and the heating rate is 2-5°C / min; the starting temperature of the second heat treatment is 180-200°C; the pressure of the second heat treatment is 100-200N; the time of the second heat treatment is 10-15min; The third heat pressing treatment is a constant temperature and pressure changing process, and the pressure reduction rate is 10-20N / min; the temperature of the third heat treatment is 200-250°C; the starting pressure of the third heat treatment is 800-900N; the time of the third treatment is 10-20min; The cooling method is air cooling; the terminal temperature of the air cooling is 20-30°C.