A manufacturing method of an aluminum alloy Vivaldi antenna array

Abstract

The present invention discloses a manufacturing method for an aluminum alloy Vivaldi antenna array, comprising the following steps: Step 1: Divide the parts of the aluminum alloy Vivaldi antenna array into upper layer array unit parts and lower layer array unit parts, and adopt interference fit for the fit tolerance of each part; Step 2: Machine each part and perform full annealing heat treatment; Step 3: Cut the welding foil; Step 4: Clean before welding; Remove the surface oxide scale; Step 5: Place the upper layer parts in an oven and heat to 200 °C, place the lower layer parts in a refrigerator and cool to 0 °C, and assemble the parts and the welding foil in place; Step 6: Place the assembled workpiece in a welding fixture and place the whole in an aluminum alloy vacuum aluminum brazing furnace; Step 7: When welding, use welding parameters of segmented heat preservation and multi-zone temperature rise with multi-gradient heat preservation for welding: After welding, when the workpiece cools in the furnace to below 80 °C, open the furnace door to take out the workpiece.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of manufacturing methods for all-metal antenna arrays, and particularly to a manufacturing method for an aluminum alloy Vivaldi antenna array. Background Art

[0002] Vilaldi antennas have characteristics such as high operating bandwidth, good directivity, and excellent gain. Antenna arrays composed of Vilaldi antenna elements have unique advantages in terms of bandwidth and wide-angle scanning impedance matching characteristics, and have currently become the first choice for many ultra-wideband phased array antenna surfaces.

[0003] Traditional Vilaldi antenna elements are generally manufactured using printed circuit board technology. There are metal patches in the shape of antennas on both sides of the printed circuit board. Each individual antenna element is connected to a metal substrate by soldering or screws to form an antenna array. However, printed circuit board antennas have disadvantages such as low structural strength, poor dimensional accuracy, and low operating power. While maintaining the ultra-wideband and wide-angle scanning characteristics, all-metal Vilaldi antennas also have advantages such as high structural strength, good dimensional accuracy, and strong environmental adaptability, and have gradually been applied in high-frequency and high-power working scenarios. For example, Patent CN201911379397.9 discloses a 6-18 GHz 45° polarized metal vivaldi antenna array, which solves the problems of low physical strength, complex feeding structure, high cost, small power capacity, and dispersion phenomenon when operating in the high-frequency band (above 6 GHz) of printed vivaldi antennas.

[0004] Aluminum alloy has advantages such as high specific strength, low density, and strong environmental adaptability. The Vivaldi antenna array made of aluminum alloy is very suitable for the national defense and mobile communication fields with strict requirements for strength, weight, and environmental adaptability. The currently commonly used manufacturing method for metal Vivaldi antenna arrays is to first separately process the antenna elements and then fix them on the metal substrate by welding or screwing. For example, the antenna array disclosed in Patent CN201911379397.9 fixes the elements on the metal substrate by silver brazing. This manufacturing method for antenna arrays has simple part processing, but there are the following problems: 1) Due to the relatively large number of installation and fitting gaps, the position accuracy and spatial pointing consistency of the elements are poor, affecting the performance of the antenna array; 2) Each individual metal element needs to be connected to a base for positioning and fixing. Otherwise, it is difficult to ensure dimensional accuracy, geometric tolerances, and connection strength. This requires sufficient operating space to be reserved between the elements during the design of the antenna array, which is not conducive to the miniaturization design of the antenna array; 3) The fastener connection method will form gaps inside the antenna array, which is prone to corrosion and has poor environmental adaptability.

[0005] With the development of radar product miniaturization and integration technologies, significant challenges have been posed to the size, integration level, and high reliability of Vivaldi antenna arrays. The size of individual elements is small, and the precision requirements are extremely high. Traditional processing technologies cannot meet the manufacturing requirements of antenna elements, and new high-precision processing technologies, precision part welding deformation control technologies, etc. must be developed to meet the design requirements of aluminum alloy Vivaldi antennas. Summary of the Invention

[0006] To solve the above problems, the present invention provides a manufacturing method for an aluminum alloy Vivaldi antenna array. This method uses special part processing, assembly, and hard soldering process methods to achieve precise forming of the antenna array through grouped element processing, interference nesting installation, and micro-miniature part welding deformation control technology. It solves the problems of reduced dimensional accuracy and poor environmental adaptability caused by installation gaps during the manufacturing process of existing antenna arrays, and can also avoid the base space required when connecting individual metal elements to the substrate, improving the forming accuracy and integration level of the aluminum alloy Vivaldi antenna array.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0008] A manufacturing method for an aluminum alloy Vivaldi antenna array includes the following steps:

[0009] Step 1: Divide the parts of the aluminum alloy Vivaldi antenna array into upper array unit parts and lower array unit parts, and use interference fit for the fit tolerances of each part.

[0010] Step 2: Process each part and perform full annealing heat treatment.

[0011] Step 3: Cut the welding foil.

[0012] Step 4: Clean before welding to remove the surface oxide scale.

[0013] Step 5: Put the upper parts into an oven and heat to 200°C, put the lower parts into a refrigerator and cool to 0°C, and assemble the parts and the welding foil in place.

[0014] Step 6: Put the assembled workpiece into a welding fixture and then put the whole into an aluminum alloy vacuum aluminum brazing furnace.

[0015] Step 7: During welding, use welding parameters of segmented heat preservation and multi-zone temperature rise with multi-gradient heat preservation for welding. After welding, when the workpiece cools with the furnace to below 80°C, open the furnace door to take out the workpiece.

[0016] Using the multi-gradient heat preservation technology with multi-zone temperature rise can reduce the deformation of the workpiece. When the workpiece cools with the furnace to below 80°C, open the furnace door to take out the workpiece.

[0017] Step 8: Remove the process margin around the substrate to ensure the final size of the substrate.

[0018] Furthermore, the solder foil is arranged between two layers of substrates, and the solder foil is made of AlSiCu solder with a thickness of 0.05 mm.

[0019] Furthermore, the welding tool includes a temperature-isolating hood and a welding base plate.

[0020] Furthermore, the temperature-averaging cover is made of the same aluminum alloy material as the Vivaldi antenna array unit.

[0021] Furthermore, an avoidance groove is arranged inside the temperature-uniform cover, and an air vent is arranged on the side, and the air vent is connected to the avoidance groove.

[0022] Furthermore, the avoidance groove and the shape of the antenna vibrator retain a single-side spacing of 0.5 mm.

[0023] Furthermore, the welding base plate is made of stainless steel and has a lightening groove arranged inside.

[0024] Furthermore, the segmented insulation in step seven is as follows: heating to 300°C, keeping warm for 60 minutes; heating to 400°C, keeping warm for 20 minutes; heating to 500°C, keeping warm for 25 minutes; heating to 570°C, keeping warm for 20 minutes; cooling to 400°C, keeping warm for 20 minutes; cooling to 80°C and the workpiece is taken out of the furnace.

[0025] Furthermore, the aluminum alloy Vivaldi antenna array includes two layers of antenna array units, each of which includes a substrate and a group of antenna elements. The two layers of antenna units are arranged up and down, and the antenna elements of the lower layer are stacked and assembled through the through holes on the upper substrate, and the antenna elements of the lower layer are installed 90 degrees apart from the antenna elements of the upper layer.

[0026] Furthermore, the aluminum alloy Vivaldi antenna array is made of 3A21 aluminum alloy.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] A manufacturing method of an aluminum alloy Vivaldi antenna array proposed by the present invention. In this manufacturing method, the vibrators are processed in groups and are an integral part of the metal substrate, with high connection strength. Geometric tolerances such as perpendicularity and position tolerance are ensured through precision machining, and the dimensional consistency and spatial directivity of the vibrators themselves are better; the pre-welding assembly of the antenna parts uses interference fit to eliminate the assembly gap, with good position tolerance of the antenna vibrators and high forming accuracy of the entire antenna array; this manufacturing method has no special requirements for the spacing between the antenna vibrators, and the antenna vibrators can be closely arranged, with higher integration, which is conducive to the miniaturization design of the antenna array; the solder foil uses high-temperature brazing material to completely fill the internal gap of the antenna array, without the risk of corrosion, and has stronger environmental adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FIG. is a schematic structural diagram of an aluminum alloy Vivaldi antenna array unit;

[0030] Figure 2 FIG. is a schematic diagram of the openings on the substrate of the upper-layer antenna array unit;

[0031] Figure 3 FIG. is a side view of the upper-layer antenna array unit;

[0032] Figure 4 FIG. is a schematic diagram of the openings on the substrate of the lower-layer antenna array unit;

[0033] Figure 5 FIG. is a side view of the upper-layer antenna array unit;

[0034] Figure 6 FIG. is a schematic diagram of the solder foil arranged between the upper-layer and lower-layer antenna array units;

[0035] Figure 7 FIG. is a schematic diagram of the cooperation between the antenna array and the welding fixture (the isothermal cover and the welding bottom plate are in partial cross-section);

[0036] Figure 8 FIG. is the temperature curve in Step VII;

[0037] Wherein: 1. Substrate; 2. Antenna vibrator; 3. Solder foil; 4. Isothermal cover; 4-1. Avoidance groove; 4-2. Vent hole; 5. Welding bottom plate; 5-1. Relief groove. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following further describes the preferred mechanisms and methods for realizing the movement of the present invention in conjunction with the drawings and specific embodiments.

[0039] As Figure 1As shown, it is an aluminum alloy Vivaldi antenna array unit, including a substrate 1 and a group of antenna oscillators 2. A complete aluminum alloy Vivaldi antenna array includes two layers of antenna array units. The lower antenna oscillators 2 are stacked and assembled through the through holes on the upper substrate 1, and the lower antenna oscillators 2 are installed at a 90-degree stagger from the upper antenna oscillators 2.

[0040] The aluminum alloy Vivaldi antenna array is manufactured using 3A21 aluminum alloy material with good weldability. Each group of antenna oscillators 2 is directly connected to the substrate 1 and integrated into one part.

[0041] The manufacturing method for manufacturing the above aluminum alloy Vivaldi antenna array includes the following steps:

[0042] Step 1: Classify the parts of the aluminum alloy Vivaldi antenna array into two categories according to size, position, and spatial orientation, namely the upper layer array unit parts and the lower layer array unit parts. The interference fit is used for the fit tolerance of each part.

[0043] The specific interference amount of the parts is determined according to the basic size of the mating surface. Since the aluminum alloy material is prone to stress release and deformation when heated at high temperatures, the heating temperature during subsequent assembly does not exceed 200°C. The tolerance values of the mating surfaces of each part are designed according to the temperature change range of the parts and the linear expansion coefficient of the aluminum alloy material to ensure the interference amount of the fit of each part.

[0044] For example: The temperature change range of the two parts during subsequent assembly is 80°C. According to the average linear expansion coefficient of 23.38 / °C of the aluminum alloy material at 100°C, it can be calculated that the fit tolerance zones are 0.012 mm and 0.006 mm respectively.

[0045] Step 2: Process each part by precision CNC milling and cooperate with high-precision slow wire electrical discharge machining. During the part processing, full annealing heat treatment is carried out to remove the processing stress.

[0046] Step 3: Cut the welding foil 3 according to the welding surfaces of each layer of parts by a laser cutting machine. The welding foil 3 is arranged between the two layers of substrates 1. The welding foil 3 uses AlSiCu filler metal with a thickness of 0.05 mm, which can reduce the welding temperature and reduce the welding heat input without reducing the weld strength.

[0047] Step 4: Clean each part and the welding foil 3 before welding to remove the surface oxide scale.

[0048] Step 5: Put the upper layer parts into an oven and heat to 200°C, put the lower layer parts into a refrigerator and cool to 0°C. After reaching the specified temperature, take out the two parts and quickly Figure 4 assemble the parts and the welding foil 3 in place according to the shown assembly sequence.

[0049] Here, the assembled parts are heated or frozen respectively. The purpose is to change the interference fit between the parts to clearance fit according to the principle of thermal expansion and contraction, so that the parts can be smoothly assembled together and the fit clearance between the parts is eliminated. When heating the parts, the temperature shall not exceed 200 °C to prevent stress release of the parts.

[0050] Step 6: Place the assembled workpiece into the welding fixture and then place the whole into the aluminum alloy vacuum brazing furnace.

[0051] The welding fixture includes a temperature equalizing cover 4 and a welding base plate 5. The temperature equalizing cover 4 is made of the same aluminum alloy material as the Vivaldi antenna array unit, which can ensure that the temperature change curves of the temperature equalizing cover 4 and the antenna array are basically the same. The internal shape of the temperature equalizing cover 4 is machined with an avoidance groove 4-1 according to the shape of the antenna element 2. To minimize the heat radiation distance and ensure the fit clearance at the same time, a unilateral distance of 0.5 mm is reserved between the avoidance groove 4-1 and the shape of the antenna element 2. Due to the reduction of the workpiece size, the radius space of the milling cutter also needs to be reserved to prevent workpiece interference. The avoidance groove 4-1 adopts two structural forms: a long waist groove and a rectangular groove + avoidance hole. At the same time, to prevent the formation of a closed space, ventilation holes 4-2 are machined on the side of the temperature equalizing cover. The ventilation holes 4-2 are connected to the avoidance groove 4-1, which can dissipate heat better. The temperature equalizing cover 4 is set because when using vacuum brazing as the radiation heating method, uneven heating may occur in different regions. In order to reduce the problem of uneven heating, ensure the consistency of part temperature rise, and reduce welding deformation during the heating process, and this temperature equalizing cover 4 has universality and can be used in other welded parts with high deformation requirements.

[0052] The welding base plate 5 is made of stainless steel, which not only ensures the high-temperature rigidity of the fixture but also reduces the heat capacity difference from the parts, avoiding welding deformation caused by the large heat capacity of the welding fixture. A relief groove 5-1 is arranged on the inner side of the welding base plate 5, which can reduce the volume, reduce the heat capacity, match the heat capacity of the workpiece, and prevent the heat capacity difference from being too large.

[0053] Place the assembled aluminum alloy Vivaldi antenna array unit of the upper and lower layers on the welding base plate 5, put on the temperature equalizing cover 4, and then place it into the aluminum alloy vacuum brazing furnace.

[0054] Step 7: During welding, segmented heat preservation is adopted, and the welding parameters are set according to the Figure 8 shown temperature curve, that is, the welding parameter setting of multi-gradient heat preservation with segmented heat preservation and multi-zone heating: heat up to 300 °C and keep warm for 60 min; heat up to 400 °C and keep warm for 20 min; heat up to 500 °C and keep warm for 25 min; heat up to 570 °C and keep warm for 20 min; cool down to 400 °C and keep warm for 20 min; cool down to 80 °C and take out the furnace. After welding, the workpiece is cooled in the furnace. When the temperature is below 80 °C, open the furnace door to take out the workpiece.

[0055] The multi-gradient heat preservation technology with multi-zone heating can reduce the deformation of the workpiece. When the workpiece cools in the furnace to below 80°C, the furnace door is opened to take out the workpiece.

[0056] Step 8: Use numerical control milling or wire cutting to remove the peripheral process allowance of the substrate 1 to ensure that the final outer dimension of the substrate 1 meets the requirements of the antenna array.

[0057] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A manufacturing method of an aluminum alloy Vivaldi antenna array, characterized in that, The aluminum alloy Vivaldi antenna array includes two layers of antenna array units. Each aluminum alloy Vivaldi antenna array unit includes a substrate (1) and a group of antenna elements (2). The two layers of antenna array units are arranged one above the other. The antenna elements (2) of the lower layer are stacked and assembled through the through holes on the substrate (1) of the upper layer, and the antenna elements (2) of the lower layer are installed at a 90-degree stagger from the antenna elements (2) of the upper layer. It includes the following steps: Divide the parts of the aluminum alloy Vivaldi antenna array into upper layer array unit parts and lower layer array unit parts, and the fit tolerance of each part adopts interference fit. Machine each part and perform full annealing heat treatment. Put the upper layer parts into an oven and heat them to 200°C. Put the lower layer parts into a refrigerator and cool them to 0°C, and assemble the parts and the solder foil (3) in place. Put the assembled workpiece into a welding fixture and then put the whole into an aluminum alloy vacuum brazing furnace. During welding, use welding parameters of segmented heat preservation and multi-zone temperature rise with multi-gradient heat preservation for welding. After welding, when the workpiece cools in the furnace to below 80°C, open the furnace door to take out the workpiece. Remove the process margin around the substrate (1) to ensure the final outer dimension of the substrate (1). The solder foil (3) is arranged between the two substrates (1), and the solder foil (3) uses an AlSiCu filler metal with a thickness of 0.05 mm. The welding fixture includes a temperature equalizing cover (4) and a welding bottom plate (5). An avoidance groove (4-1) is arranged inside the temperature equalizing cover (4), and air vents (4-2) are arranged on the side. The air vents (4-2) are communicated with the avoidance groove (4-1). A spacing of 0.5 mm is reserved between the avoidance groove (4-1) and the outer shape of the antenna element (2). The welding bottom plate (5) is made of stainless steel and a relief groove (5-1) is arranged inside.

2. The manufacturing method of an aluminum alloy Vivaldi antenna array according to claim 1, characterized in that The temperature equalizing cover (4) uses the same aluminum alloy material as the Vivaldi antenna array unit.

3. The manufacturing method of an aluminum alloy Vivaldi antenna array according to claim 1, characterized in that, The segmented heat preservation in step seven is as follows: heat up to 300°C and keep warm for 60 min; heat up to 400°C and keep warm for 20 min; heat up to 500°C and keep warm for 25 min; heat up to 570°C and keep warm for 20 min; cool down to 400°C and keep warm for 20 min; when the workpiece cools down to 80°C, take the workpiece out of the furnace.

4. The manufacturing method of an aluminum alloy Vivaldi antenna array according to claim 1, characterized in that, The aluminum alloy Vivaldi antenna array is made of 3A21 aluminum alloy.

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