Dewar cold finger of ceramic metal composite structure and preparation method
By adopting a ceramic-metal composite structure of Dewar cold finger, combined with zirconia ceramic material and metal cold finger blank base, a split brazed cold finger structure is formed, which solves the problem of large solid heat transfer of Dewar cold fingers, and achieves the effect of reducing conduction heat leakage and improving mechanical reliability.
Patent Information
- Application Number
- CN202411584354.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-07
- Publication Date
- 2025-03-07
AI Technical Summary
The solid heat transfer of the existing Dewar cold finger accounts for half of the Dewar's static thermal load, resulting in large heat consumption and affecting the cost and performance of infrared detector components.
The Dewar cold finger, which adopts a ceramic metal composite structure, combines zirconia ceramic material with a metal cold finger blank base to form a split brazed cold finger structure to reduce the conduction and heat leakage of the cold finger.
It effectively reduces the conduction heat leakage of the Dewar cold finger, reduces the quality and cost of infrared detector components, and improves the mechanical reliability of the structure.
Smart Images
Figure CN119573318A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of infrared detectors, and in particular to a Dewar cold finger of a ceramic-metal composite structure and a preparation method thereof. Background Art
[0002] The infrared detector assembly is composed of a dewar and a refrigerator. The infrared detector is encapsulated on the dewar cold head and works in a low temperature and ultra-high vacuum of 77K. The ambient temperature outside the dewar is normal temperature and pressure.
[0003] Heat consumption is an important performance indicator of the Dewar. When designing the structure of the infrared detector assembly, it affects the selection of the refrigerator, the cooling capacity demand of the refrigerator, the stable power of the refrigerator and the working life of the refrigerator. These have a significant impact on the cost and performance of the infrared detector assembly.
[0004] The heat consumption of the Dewar is composed of radiation heat transfer, solid heat transfer, convection heat transfer and the endogenous Joule heat of the chip. The Joule heat of the chip is controlled by the design of the detector. The interior of the Dewar is an ultra-high vacuum, and the convection heat transfer can be ignored. Radiation heat transfer is due to the radiation of heat from the room temperature outer wall of the Dewar to the low temperature cold head inside the Dewar. Solid heat transfer is the heat conduction from the room temperature cold finger base of the Dewar or other cold head support structure to the low temperature cold head inside the Dewar. The heat consumption of the Dewar mainly includes the Joule heat of the chip, radiation heat transfer and solid heat transfer. The heat consumption composed of radiation heat transfer and solid heat transfer also constitutes the static heat load of the Dewar, which is used to indicate the minimum cooling required for the Dewar to reach the temperature when the detector is not working.
[0005] The solid heat transfer of the cold finger accounts for almost half of the static heat load of the Dewar. When the length of the cold finger is the same, the thermal conductivity and wall thickness of the cold finger material directly affect the solid heat transfer of the cold finger. The cold finger is a thin-walled structural part, which is difficult to process. In addition, the cold finger serves as the main mechanical support structure to ensure the mechanical reliability of the Dewar cold head under large-scale vibration. In engineering, titanium alloys, iron-nickel alloys, high-temperature alloys and other metals with both processability and mechanical strength are often used as thin-walled materials for cold fingers. Taking a high-temperature alloy cold finger with an inner diameter of 9mm, a wall thickness of 0.15mm, and a thin-wall length of 38.7mm as an example, the thermal conductivity of the high-temperature alloy is 6W / m·K, the cold end temperature is 77K, and the hot end temperature is 296K. The heat leakage of the cold finger conduction is about 230mW. Summary of the invention
[0006] The embodiments of the present application provide a Dewar cold finger of a ceramic-metal composite structure and a preparation method thereof, which effectively reduce the mass of the cold finger, reduce the mass of the infrared detector assembly, and increase the mechanical reliability of the structure.
[0007] The present application provides a Dewar cold finger of a ceramic-metal composite structure, comprising:
[0008] Metal cold finger blank base;
[0009] A cold finger blank tube made of ceramic material is welded on the cold finger blank base.
[0010] Optionally, the cold finger blank base is made of metal material, and one end of the cold finger blank base is provided with a circular groove for welding or bonding with the cold finger blank tube.
[0011] Optionally, the cold finger blank tube is prepared by 3D printing, hot die casting, or dry pressing, and the outer diameter of the cold finger blank tube is adapted to the circular groove.
[0012] Optionally, the cold finger blank tube is made of zirconium oxide material or zirconium oxide-aluminum oxide composite ceramic material.
[0013] Optionally, a metallized nickel layer with a thickness of 5 μm to 25 μm is plated at the brazing position between the cold finger blank tube and the cold finger blank base.
[0014] The present application also provides a method for preparing a Dewar cold finger of the aforementioned ceramic-metal composite structure, comprising the following steps:
[0015] A cold finger blank tube is prepared, and nickel-plated at the connection position with the cold finger blank base;
[0016] The sealant is placed in the circular groove of the cold finger blank seat, and is baked and cured at room temperature or low temperature to form a Dewar cold finger blank with a ceramic-metal composite structure;
[0017] The inner wall of the cold finger blank in the blank is used as a positioning reference, and the cold finger blank seat is machined so that the inner wall of the cold finger meets the accuracy requirement.
[0018] The embodiment of the present application further provides an infrared detector assembly, including a Dewar cold finger processed by the Dewar cold finger of the ceramic-metal composite structure as described above.
[0019] The embodiment of the present application adopts a split brazed cold finger structure, and the cold finger base material can be consistent with the outer shell of the Dewar, which can simplify the Dewar outer shell structure and process, effectively reduce the mass of the cold finger, reduce the mass of the infrared detector assembly, and increase the mechanical reliability of the structure.
[0020] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:
[0022] Figure 1 Schematic diagram of the structure of the Dewar cold finger of the ceramic-metal composite structure according to an embodiment of the present application. DETAILED DESCRIPTION
[0023] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.
[0024] The present application embodiment provides a Dewar cold finger of a ceramic-metal composite structure, such as Figure 1 As shown, including:
[0025] Metal cold finger blank base 1;
[0026] The ceramic cold finger blank tube 2 is welded on the cold finger blank base. The present application adopts a split brazing cold finger structure, and the cold finger base material can be consistent with the shell of the dewar, which can simplify the dewar shell structure and process.
[0027] In some embodiments, the cold finger blank base is made of titanium alloy TC4, and one end thereof is provided with a circular groove for welding with the cold finger blank tube. In some specific examples, the diameter of the circular groove is 10.4 mm and the depth is 16 mm.
[0028] In some embodiments, the cold finger blank tube is prepared by 3D printing, hot die casting, or dry pressing, and the outer diameter of the cold finger blank tube is adapted to the circular groove. In some specific examples, the welding connection between the cold finger blank tube 1 and the cold finger blank tube 2 has an outer diameter of 10.4 mm and a height of 17 mm.
[0029] In some embodiments, the cold finger blank tube is made of zirconium oxide material.
[0030] In some embodiments, the brazing position between the cold finger blank tube and the cold finger blank base is plated with a nickel layer of 5 μm-25 μm, and the outer diameter of the remaining area is 9.6 mm.
[0031] In some specific examples, the cold finger blank tube can be prepared by hot die casting, dry pressing, isostatic pressing or 3D printing, and the connection position between the cold finger blank tube and the cold finger blank base is metallized. Solder is added to the groove of the cold finger blank base, and the cold finger blank tube is placed and brazed with the metal cold finger blank base such as iron-nickel alloy and titanium alloy to form a Dewar cold finger with a ceramic-metal composite structure.
[0032] In some specific examples, the cold finger blank tube can be prepared by hot die casting, dry pressing, isostatic pressing or 3D printing, and the connection position between the cold finger blank tube and the cold finger blank base is metallized. A sealant is applied to the circular groove of the cold finger blank base, and the cold finger blank tube is placed on it. After the sealant is cured, a Dewar cold finger of a ceramic-metal composite structure is formed.
[0033] This application uses low thermal conductivity ceramics as the thin-walled part of the cold finger to form a composite cold finger structure with the metal part. Zirconia is used as the inner wall material of the cold finger, with a thermal conductivity of 2.7W / m·K, a wall thickness of 0.3mm, a cold end temperature of 77K, and a hot end temperature of 296K. The cold finger conduction heat leakage is about 134mW. Compared with the commonly used high-temperature alloy cold finger structure, when the structure of this embodiment is used, the Dewar cold finger conduction heat leakage is reduced by 96mW, about 41.7%. Due to the large temperature difference between the cold and hot ends of the cold finger thin-walled tube and the difference in the molding process of the zirconia thin-walled tube, when zirconia is used as the inner wall material of the cold finger, the thermal conductivity ranges from 1.3W / m·K to 3.2W / m·K, and the empirical equivalent thermal conductivity is about 2.7W / m·K.
[0034] The embodiment of the present application adopts a split brazed cold finger structure, and the cold finger base material can be consistent with the outer shell of the Dewar, which can simplify the Dewar outer shell structure and process, effectively reduce the mass of the cold finger, reduce the mass of the infrared detector assembly, and increase the mechanical reliability of the structure.
[0035] The present application also provides a method for preparing a Dewar cold finger of the ceramic-metal composite structure as described above, characterized in that it comprises the following steps:
[0036] Prepare a cold finger blank tube and perform nickel plating on the brazing position with the cold finger blank base;
[0037] The sealant is placed in the circular groove of the cold finger blank seat, and is baked and cured at room temperature or a relatively low temperature to form a Dewar cold finger blank with a ceramic-metal composite structure.
[0038] The inner wall of the cold finger blank in the blank is used as a positioning reference, and the cold finger blank seat is machined so that the inner wall of the cold finger meets the accuracy requirement.
[0039] In some embodiments, the nickel plating thickness at the brazing position with the cold finger blank base is 5 μm-25 μm. In a specific example, the material of the metal cold finger blank base is titanium alloy TC4, with a round top, a diameter of 10.4 mm, and a depth of 16 mm.
[0040] The zirconia cold finger blank tube prepared by 3D printing has an inner diameter of 9mm, an outer diameter of 10.4mm at the welding connection, and a height of 17mm. The connection between the cold finger blank tube and the cold finger blank base is nickel-plated with a nickel layer thickness of 5-25μm, and the outer diameter of the remaining area is 9.6mm.
[0041] The solder sheet is placed in the cold finger blank seat groove, the cold finger blank tube is placed in the cold finger blank seat, and the whole is placed in a brazing furnace. The blank tube is brazed with a metal cold finger blank base such as iron-nickel alloy and titanium alloy to form a Dewar cold finger blank with a ceramic-metal composite structure.
[0042] After brazing, the cold finger blank seat part is machined according to the final drawing to form the Dewar cold finger required by the composite structure.
[0043] The embodiment of the present application realizes the preparation of Dewar cold finger with low conduction heat leakage, effectively reducing the static heat load of Dewar. The present application adopts low-density, high-strength zirconia ceramic as the cold finger blank tube, which can effectively reduce the mass of the cold finger, reduce the mass of the infrared detector assembly, and increase the mechanical reliability of the structure.
[0044] Compared with the traditional machining method of metal cold finger thin walls, the processing method of zirconia ceramics in this application diversifies the structural forms of cold finger thin walls under the premise of reducing conductive heat leakage and increasing structural strength. The wall thickness is gradually changed in the direction of the cold finger temperature gradient to ensure that the equivalent wall thickness is within a safe range. The thick bottom and thin top structure ensures mechanical strength, which allows the cold end temperature of the cold finger to drop rapidly and reduce the conductive heat leakage of the cold finger. In the direction of the cold finger temperature gradient, a structure of metal thin wall layers and zirconia thin wall layers are arranged at intervals. The number of material connection layers inside the cold finger thin wall increases, the contact thermal resistance becomes larger, and the conductive heat leakage of the cold finger is reduced.
[0045] The embodiment of the present application further provides an infrared detector assembly, including a Dewar cold finger processed by the Dewar cold finger of the ceramic-metal composite structure as described above.
[0046] It should be noted that in the various embodiments of the present application, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.
[0047] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.
[0048] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.
Claims
1. A Dewar cold finger of a ceramic-metal composite structure, characterized in that: include: Metal cold finger blank base; A cold finger blank tube made of ceramic material is welded on the cold finger blank base.
2. The Dewar cold finger of the ceramic-metal composite structure according to claim 1, characterized in that: The cold finger blank base is made of metal material, and one end of the base is provided with a circular groove for welding or bonding with the cold finger blank tube.
3. The Dewar cold finger of the ceramic-metal composite structure as claimed in claim 2, characterized in that: The cold finger blank tube is prepared by 3D printing, hot die casting, and dry pressing, and the outer diameter of the cold finger blank tube is adapted to the circular groove.
4. The Dewar cold finger of the ceramic-metal composite structure as claimed in claim 3, characterized in that: The cold finger blank tube is made of zirconium oxide material or zirconium oxide alumina composite ceramic material.
5. The Dewar cold finger of the ceramic-metal composite structure as claimed in claim 3, characterized in that: The brazing position between the cold finger blank tube and the cold finger blank base is plated with a metallized nickel layer with a thickness of 5 μm to 25 μm.
6. A method for preparing a Dewar cold finger of a ceramic-metal composite structure as claimed in any one of claims 1 to 5, characterized in that: The steps include: A cold finger blank tube is prepared, and nickel-plated at the connection position with the cold finger blank base; The sealant is placed in the circular groove of the cold finger blank seat, and is baked and cured at room temperature or low temperature to form a Dewar cold finger blank with a ceramic-metal composite structure; The inner wall of the cold finger blank in the blank is used as a positioning reference, and the cold finger blank seat is machined so that the inner wall of the cold finger meets the accuracy requirement.
7. An infrared detector assembly, characterized in that: The invention comprises a Dewar cold finger processed by the Dewar cold finger of the ceramic-metal composite structure according to any one of claims 1 to 5.