A structure for improving the output power of microwave energy transmission window and a composite film metallization method

Abstract

The present invention belongs to the field of vacuum electronics, and discloses a structure for improving the output power of a microwave energy transmission window and a composite thin film metallization method. The method is to coat a composite film of a certain thickness on the microwave energy transmission window in two steps by magnetron sputtering coating. First, a mask is used to cover the middle area of ​​the dielectric window, and the edge is coated with composite film layers of different thicknesses by magnetron sputtering or electron beam evaporation. The composite film layer can realize vacuum welding of the window; then a mask is used to cover the edge, and a certain thickness of titanium nitride or silver oxide is plated in the central area of ​​the dielectric window by magnetron sputtering or electron beam evaporation. The titanium nitride or silver oxide in the central area can significantly reduce the plasma breakdown caused by high microwave power. The present invention is applicable to the field of vacuum electronics technology, and the method can improve the pressure resistance of the energy transmission window and significantly improve the power capacity of the energy transmission window.

Description

Technical Field

[0001] The invention belongs to the field of vacuum electronics and relates to a structure for improving the output power of a microwave energy transmission window and a composite film metallization method. Background Art

[0002] Vacuum tubes in the field of vacuum electronics can generate high-power microwaves, such as gyrotrons, klystrons, traveling wave tubes, etc. This high-power microwave device can output microwave power of tens of kilowatts to tens of megawatts, and can be used in nuclear fusion auxiliary heating, space exploration, high-efficiency steelmaking, etc. The high-power microwaves generated by the vacuum tube need to be output through the energy transmission window. The dielectric window is a key part of the energy transmission window. It has two functions. One is to make the vacuum tube airtight by welding with other parts of the output window; the other is to transmit high-power microwaves to the outside of the vacuum tube. There are two difficulties in the development of the energy transmission window. One is the sealing of the dielectric window and the metal parts, and the other is that high-power microwaves are prone to plasma breakdown near the dielectric window, causing the dielectric window to be damaged. For the sealing problem of the dielectric window, the current common solution is to form a molybdenum manganese oxide transition layer on the dielectric window, and then use brazing to achieve welding. The "High-temperature Metallization Process for Yttrium Oxide Ceramics" with publication number CN105948826A uses the activated molybdenum-manganese method to perform high-temperature metallization on yttrium oxide ceramics, with a temperature of more than 1300°, which is not suitable for the metallization of diamond materials; and it needs to be sintered in a high-temperature hydrogen furnace many times, which is costly, has a long cycle, and cannot be reused once it fails. The sputtering coating method in the patent can be completed at a temperature of no more than 300°, and there is no need to use a high-temperature hydrogen furnace to perform high-temperature metallization on the material, which has advantages in both cost and cycle.

[0003] To this end, the present invention proposes a new dielectric window capable of improving the output power of microwave energy transmission and a preparation method for realizing the new structure. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a structure for improving the output power of a microwave energy transmission window and a composite thin film metallization method. First, metal films of different thicknesses are sequentially plated on the edge of the dielectric window, and stress is removed by high-temperature baking. At the same time, the active metal and the dielectric form a firm compound layer to improve the bonding strength. The whole process has low cost and short cycle. At the same time, if the quality of the film layer is not high, the plated film layer can be stripped and re-plated. After the edge portion is plated, a film of a material that suppresses secondary electron emission of a certain thickness is plated on the middle portion. The film layer can reduce the secondary electron emission density, increase the power threshold of plasma breakdown, and reduce the probability of damage to the output window caused by sparking under high-power conditions.

[0005] The technical solution of the present invention:

[0006] A structure for improving the output power of a microwave energy transmission window includes a dielectric window for sealing a vacuum system. An active metal film, a transition metal film and a solder-wetting metal film are first plated in sequence on other areas except the middle area of ​​the dielectric window by a plasma sputtering method; and then a secondary electron emission suppression material film is plated on the middle area of ​​the dielectric window by a plasma sputtering method.

[0007] Furthermore, the shape of the dielectric window may be cylindrical or elliptical; its material properties may be diamond material, aluminum oxide material, beryllium oxide material, sapphire material and other dielectric materials used for microwave transmission.

[0008] Furthermore, the active metal film can be titanium or chromium, and its outer edge coincides with the edge of the dielectric window (10). The width of the active metal film is between 1 mm and 3 mm, and the film thickness is between 10 and 100 nm depending on the material of the dielectric window. The transition metal film is made of copper and has a thickness of 500 nm. The solder-wetting metal film is made of nickel and has a nickel layer thickness of 1000 to 3000 nm depending on the material of the welded parts. The secondary electron emission suppression material film can be made of titanium nitride or silver oxide and is sputtered using a plasma sputtering method. The thickness is between 5 nm and 50 nm depending on the requirements of different microwave frequencies.

[0009] Furthermore, the central upper mask plate and the central lower mask plate are used to partially shield the middle area, and the active metal film, the transition metal film and the solder-wetting metal film that are in contact are sequentially plated on the dielectric window plate by plasma sputtering. After the coating is completed, the central upper mask plate and the central lower mask plate are removed.

[0010] Furthermore, the active metal film, transition metal film and solder wetted metal film are shielded by using the edge upper mask plate and the edge lower mask plate. The secondary electron emission suppression material film is plated to the central area by plasma sputtering, and then the edge upper mask plate and the edge lower mask plate are removed.

[0011] The present invention also provides a microwave energy transmission window composite film metallization method, comprising the following steps:

[0012] Step 1: Clean the dielectric window. The specific method is: use alcohol or ethanol with a purity of more than 98% to ultrasonically clean it for 30 minutes, and then place it in a drying oven to dry for 30 minutes;

[0013] Step 2: Use the center upper mask and the center lower mask to cover the middle part of the dielectric window, and then place it in the plasma sputtering equipment to coat the active metal film in sequence. Depending on the material of the dielectric window, the film thickness can be selected between 10-100nm, 500nm for transition metal film, and 1000-3000nm for solder wetting metal film according to the material characteristics of the welding parts.

[0014] Step 3: Take out the dielectric window after edge coating, use the upper edge mask and the lower edge mask (32) to shield the active metal film, transition metal film and solder-wetting metal film, and use plasma sputtering to plate the secondary electron emission suppression material film to the central area. The film thickness is selected between 5nm and 50nm according to different operating frequencies.

[0015] Step 4: After the coating is completed, remove the upper edge mask and the lower edge mask, and store the coated dielectric window in a vacuum chamber with a vacuum degree better than 10-1Pa.

[0016] Beneficial effects of the present invention: The present invention designs a structure for improving the output power of the microwave energy transmission window. The structure can be divided into two coatings. First, a metal composite film of titanium copper nickel or chromium copper nickel is plated on the edge of the dielectric window, and then a secondary electron emission suppression material film of titanium nitride or silver oxide is plated on the central area. The active metal film close to the dielectric window can react with the medium at high temperature to produce compounds and improve the bonding strength; the outermost nickel layer can form infiltration with the solder to facilitate brazing. The activated molybdenum manganese method is used for high-temperature metallization of yttrium oxide ceramics, and the temperature is as high as 1300° or more, which is not suitable for the metallization of diamond materials; and it needs to be sintered in a high-temperature hydrogen furnace many times, which is costly and has a long cycle. Once it fails, it cannot be reused. Using the method in this patent, the process temperature can be completed at no more than 300°, and there is no need to use a high-temperature hydrogen furnace to metallize the material at high temperature, which has advantages in cost and cycle. After the coating failure is processed, the dielectric window can be reused after removing the metal film layer, which is particularly suitable for expensive materials such as boron nitride and diamond; the secondary electron emission suppression material film coating in the central area can reduce the secondary electron emission rate of the dielectric window, increase the power capacity of the energy transmission window, and reduce the probability of ignition. The present invention proposes a composite thin film metallization method, through which a composite metal film layer and a secondary electron emission suppression material film can be plated on a dielectric window using a plasma sputtering device, with high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the microwave energy transmission window for improving the output power of the present invention, wherein (a) is a top view of the dielectric window, (b) is a cross-sectional view of the dielectric window, and (c) is an enlarged view of the edge of the cross-sectional view of the dielectric window;

[0018] Figure 2 This is a schematic diagram of the dielectric window edge coating structure;

[0019] Figure 3 Schematic diagram of the coating structure in the central area of ​​the dielectric window.

[0020] In the figure: 1-structure of output power of energy transmission window, 10-dielectric window, 11-active metal film, 12-transition metal film, 13-solder wetting metal film, 14-secondary electron emission suppression material film; 2-dielectric window edge coating structure, 20-center upper mask plate, 21-center lower mask plate; 3-dielectric window center area coating structure, 31-edge upper mask plate, 32-edge lower mask plate. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0022] The present invention provides a structure for improving the output power of a microwave energy transmission window and a composite thin film metallization method, which utilizes magnetron sputtering coating to coat a film of a certain thickness on a microwave energy transmission window in two steps. First, a mask is used to cover the middle area of ​​the energy transmission window, and a composite film layer of different thicknesses is coated on the edge portion by magnetron sputtering or electron beam evaporation; then, for example, a mask is used to cover the edge portion, and a certain thickness of titanium nitride or silver oxide is coated on the center area of ​​the window by magnetron sputtering or electron beam evaporation.

[0023] The following combination Figure 1-Figure 3 The present invention is described in further detail.

[0024] like Figure 1 As shown, the structure 1 for improving the output power of the microwave energy transmission window of the present invention includes a dielectric window 10 for sealing the vacuum system and an active metal film 11, a transition metal film 12 and a solder-wetted metal film 13 in contact therewith, and the middle area is a secondary electron emission suppression material film 14.

[0025] The structure 1 for improving the output power of the microwave energy transmission window is cylindrical or elliptical in shape; the dielectric window 10 used for sealing the vacuum system can be made of diamond material, aluminum oxide material, beryllium oxide material, or sapphire material.

[0026] The composite metal film layers contacted by the dielectric window 10 are, in order, an active metal film 11, a transition metal film 12 and a solder wetted metal film 13. The active metal film 11 can be titanium or chromium. Its outer edge coincides with the edge of the dielectric window 10. The width of the active metal film 11 is between 1 mm and 3 mm. Depending on the material of the dielectric window, the film thickness is between 10 nm and 100 nm.

[0027] The transition metal film 12 is made of copper and has a thickness of about 500 nm. The solder wetted metal film 13 can be made of nickel and has a thickness of between 1000 nm and 3000 nm.

[0028] The secondary electron emission suppression material film 14 may be made of titanium nitride or silver oxide, and is formed by plasma sputtering with a thickness of 5 nm to 50 nm.

[0029] like Figure 2 As shown, the central upper mask plate 20 and the central lower mask plate 21 are used to shield the middle part, and the active metal film 11, the transition metal film 12 and the solder-wetting metal film 13 that are in contact are sequentially plated on the dielectric window 10 by plasma sputtering. After the coating is completed, the upper mask plate 20 and the lower mask plate 21 are removed.

[0030] like Figure 3 As shown, the active metal film 11, transition metal film 12 and solder wetting metal film 13 are shielded by edge upper mask plate 31 and edge lower mask plate 32. The secondary electron emission suppression material film 14 is plated to the central area by plasma sputtering, and then the edge upper mask plate 31 and edge lower mask plate 32 are removed.

[0031] The microwave energy transmission window composite film metallization method of the present invention comprises the following steps:

[0032] Step 1: Clean the dielectric window 10 by ultrasonic cleaning with alcohol or ethanol with a purity of 98% or more for 30 minutes, and then place it in a drying oven for drying for 30 minutes;

[0033] Step 2: Use the central upper mask plate 20 and the central lower mask plate 21 to cover the middle part of the dielectric window, and then place it in a plasma sputtering device to sequentially plate an active metal film of 10nm-100nm, a transition metal film of 100nm-500nm, and a solder wetting metal film of 1000nm-3000nm.

[0034] Step three: take out the dielectric window 10 after edge coating, use the upper edge mask 31 and the lower edge mask 32 to block the active metal film 11, the transition metal film 12 and the solder-wetting metal film 13, and use plasma sputtering to plate the secondary electron emission suppression material film 14 to the central area, with a film thickness of 5nm-50nm.

[0035] Step 4: After the coating is completed, the upper edge mask plate 31 and the lower edge mask plate 32 are removed, and the coated dielectric window 10 is placed in a vacuum chamber for storage, and the vacuum degree of the vacuum chamber is better than 10-1Pa.

[0036] Example 1

[0037] This embodiment provides a 170 GHz gyrotron output window thin film metallization method, comprising the following steps:

[0038] Step 1: Clean the diamond medium window 10 with a diameter of 100 mm. The specific method is: use alcohol or ethanol with a purity of more than 98% to ultrasonically clean it for 30 minutes, and then place it in a drying oven for drying for 30 minutes;

[0039] Step 2: Use the central upper mask plate 20 and the central lower mask plate 21 to cover the 98mm portion between the dielectric window, and then place it in a plasma sputtering device to sequentially plate a titanium active metal film of 100nm, a copper transition metal film of 500nm, and a nickel solder infiltration metal film of 3000nm.

[0040] Step three: take out the diamond dielectric window 10 after edge coating, use the upper edge mask 31 and the lower edge mask 32 to block the titanium active metal film 11, the copper transition metal film 12 and the nickel solder infiltration metal film 13, and use plasma sputtering to plate the titanium oxynitride secondary electron emission suppression material film 14 to the central area with a film thickness of 5nm.

[0041] Step 4: After the coating is completed, the upper edge mask plate 31 and the lower edge mask plate 32 are removed, and the coated diamond dielectric window 10 is placed in a vacuum chamber for storage, and the vacuum degree of the vacuum chamber is better than 10-1Pa.

[0042] Example 2

[0043] This embodiment provides a 170 GHz gyrotron radiation window thin film metallization method, comprising the following steps:

[0044] Step 1: Clean the sapphire medium window 10 with a diameter of 80 mm. The specific method is: use alcohol or ethanol with a purity of more than 98% to ultrasonically clean it for 30 minutes, and then place it in a drying oven for drying for 30 minutes;

[0045] Step 2: Use the central upper mask plate 20 and the central lower mask plate 21 to cover the 76mm diameter portion of the sapphire dielectric window, and then place it in a plasma sputtering device to sequentially plate a 50nm chromium active metal film, a 500nm copper transition metal film, and a 3000nm nickel solder wetting metal film.

[0046] Step 3: Take out the sapphire dielectric window 10 after edge coating, use the upper edge mask 31 and the lower edge mask 32 to block the chromium active metal film 11, the copper transition metal film 12 and the nickel solder infiltration metal film 13, and use plasma sputtering to plate the titanium nitride secondary electron emission suppression material film 14 to the central area with a film thickness of 5nm.

[0047] Step 4: After the coating is completed, the upper edge mask plate 31 and the lower edge mask plate 32 are removed, and the coated sapphire dielectric window 10 is placed in a vacuum chamber for storage, and the vacuum degree of the vacuum chamber is better than 10-1Pa.

[0048] Example 3

[0049] This embodiment provides a method for metallizing an output window thin film of an X-band high-power klystron tube, comprising the following steps:

[0050] Step 1: Clean the boron nitride dielectric window 10 with a diameter of 50 mm. The specific method is: use alcohol or ethanol with a purity of more than 98% to ultrasonically clean it for 30 minutes, and then place it in a drying oven for drying for 30 minutes;

[0051] Step 2: Use the central upper mask plate 20 and the central lower mask plate 21 to cover the part with a diameter of 46 mm in the middle of the boron nitride dielectric window, and then place it in a plasma sputtering device to sequentially plate a titanium active metal film of 100 nm, a copper transition metal film of 500 nm, and a nickel solder infiltration metal film of 2000 nm.

[0052] Step 3: Take out the boron nitride dielectric window 10 after edge coating, use the upper edge mask 31 and the lower edge mask 32 to block the titanium active metal film 11, the copper transition metal film 12 and the nickel solder infiltration metal film 13, and use plasma sputtering to plate the titanium nitride secondary electron emission suppression material film 14 to the central area with a film thickness of 30nm.

[0053] Step 4: After the coating is completed, the upper edge mask plate 31 and the lower edge mask plate 32 are removed, and the coated boron nitride dielectric window 10 is placed in a vacuum chamber for storage, and the vacuum degree of the vacuum chamber is better than 10-1Pa.

[0054] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application.

[0055] Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be included in the protection scope of this application.

Claims

1. A structure for improving the output power of a microwave energy transmission window, characterized in that: The structure for improving the output power of the microwave energy transmission window includes a dielectric window for sealing a vacuum system. An active metal film, a transition metal film and a solder-wetting metal film are first plated in sequence on other areas except the middle area of ​​the dielectric window by a plasma sputtering method; and then a secondary electron emission suppression material film is plated on the middle area of ​​the dielectric window by a plasma sputtering method.

2. The structure for improving the output power of the microwave energy transmission window according to claim 1, characterized in that: The dielectric window is cylindrical or elliptical in shape, and is made of diamond, aluminum oxide, beryllium oxide, or sapphire.

3. The structure for improving the output power of the microwave energy transmission window according to claim 1, characterized in that: The active metal film is titanium or chromium, and its outer edge coincides with the edge of the dielectric window (10). The width of the active metal film is between 1 mm and 3 mm, and its thickness is between 10 and 100 nm depending on the material of the dielectric window.

4. The structure for improving the output power of a microwave energy transmission window according to claim 1, characterized in that: The transition metal film is made of copper material and has a thickness of 500nm.

5. The structure for improving the output power of a microwave energy transmission window according to claim 1, characterized in that: The solder-wetting metal film is made of nickel material. The thickness of the solder-wetting metal film is 1000-3000nm depending on the material of the welding parts.

6. The structure for improving the output power of a microwave energy transmission window according to claim 1, characterized in that: The secondary electron emission suppression material film is made of titanium nitride or silver oxide and is sputtered by plasma. The thickness is between 5nm and 50nm according to the requirements of different microwave frequencies.

7. The structure for improving the output power of a microwave energy transmission window according to claim 1, characterized in that: The central upper mask plate and the central lower mask plate are used to partially block the middle area, and the contacting active metal film, transition metal film and solder-wetting metal film are sequentially plated on the dielectric window plate by plasma sputtering. After the coating is completed, the central upper mask plate and the central lower mask plate are removed.

8. The structure for improving the output power of a microwave energy transmission window according to claim 1, characterized in that: The active metal film, transition metal film and solder-wetting metal film are shielded by using the edge upper mask plate and the edge lower mask plate; the secondary electron emission suppression material film is plated to the central area by plasma sputtering, and then the edge upper mask plate and the edge lower mask plate are removed.

9. A method for metallizing a composite film of a microwave energy transmission window, comprising the following steps: Step 1: Clean the dielectric window. The specific method is: use alcohol or ethanol with a purity of more than 98% to ultrasonically clean it for 30 minutes, and then place it in a drying oven to dry for 30 minutes; Step 2: Use the central upper mask plate and the central lower mask plate to cover the middle part of the dielectric window, and then place it in the plasma sputtering equipment to plate active metal films in sequence. According to the different materials of the dielectric window, the film thickness is selected between 10-100nm, the transition metal film is 500nm, and according to the material characteristics of the welding parts, the solder infiltration metal film is selected between 1000-3000nm; Step 3, take out the dielectric window after edge coating, use the upper edge mask plate and the lower edge mask plate (32) to shield the active metal film, the transition metal film and the solder-wetting metal film, and use plasma sputtering to plate the secondary electron emission suppression material film to the central area, and the film thickness is selected between 5nm and 50nm according to different operating frequencies; Step 4: After the coating is completed, remove the upper edge mask and the lower edge mask, and store the coated dielectric window in a vacuum chamber with a vacuum degree better than 10-1Pa.

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