Electric continuous splicing method of frequency selection film metal layer

Abstract

The invention discloses an electric continuous splicing method of a frequency selection film metal layer, and belongs to the technical field of composite materials and stealth. The method comprises the following steps: firstly, paving a prepreg and a frequency selection film on a mold, and controlling a butt joint gap to be less than or equal to 0.1 mm; then manufacturing a hollow silk screen according to the metal layer pattern; accurately printing conductive slurry on the metal layer at the butt joint gap by using a silk screen through printing technology to form an electric connection bridge; and finally, conducting test, slurry curing and subsequent forming are carried out. According to the method, micron-sized accurate positioning of the conductive slurry is realized through silk-screen printing, excellent electrical continuity and size consistency at the splicing position are ensured, the problem of RCS performance deterioration caused by unreliable electrical connection at the splicing position of the large frequency selection antenna housing is effectively solved, and the stealth effect is remarkably improved. The method is good in process compatibility and high in reliability.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of composite material molding and radar stealth technology. Specifically, it relates to a method for splicing the metal layer of frequency-selective film for frequency-selective surface (FSS) radomes. It is particularly suitable for solving the technical problem of reliable splicing required in the manufacturing of large stealth aircraft radomes due to the limited size of the frequency-selective film. Background Technology

[0002] Frequency-selective stealth radomes are key components for achieving radio frequency stealth in aircraft. By embedding a frequency-selective film with a periodic metallic pattern within the dielectric radome, they achieve high transmission of electromagnetic waves in friendly communication bands and high reflection or scattering of electromagnetic waves in enemy radar detection bands, thereby significantly reducing the aircraft's radar cross-section (RCS).

[0003] Currently, the maximum width of high-performance frequency-selective films produced domestically is typically no more than 500mm. When manufacturing curved skin for large radomes, multiple frequency-selective films must be spliced ​​together. The core challenge of this splicing lies in ensuring the electrical continuity of the metallic pattern at the splice point, i.e., forming a stable conductive path. If the electrical connection at the splice point is unreliable, the frequency selectivity of the radome in that area will fail, resulting in electromagnetic leakage and severely deteriorating the overall stealth performance.

[0004] Existing splicing technologies, such as those using conductive adhesives or physical overlap, have the following drawbacks: 1. Poor positioning accuracy: It is difficult to accurately align metal wires with a width of only micrometers, easily leading to misalignment and affecting electrical performance. 2. Low connection reliability: The adhesive interface resistance is high and unstable, making it prone to failure under high and low temperature cycling or vibration environments. 3. Difficulty in controlling thickness: Local protrusions may occur at the adhesive layer or overlap, affecting the flatness of the composite material and the final aerodynamic shape. Therefore, there is an urgent need for a method that can achieve high-precision, high-reliability, and low-resistance continuous splicing. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a method for electrically continuous splicing of frequency-selective film metal layers. This method utilizes screen printing technology to precisely position and print conductive paste, achieving reliable electrical connection of the metal layers at the splicing points, thereby ensuring the overall electromagnetic performance of large frequency-selective radomes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for electrically continuous splicing of frequency-selective film metal layers includes the following steps: S1. Substrate application: Apply at least one layer of resin-based prepreg to the molding die; S2. Frequency selective film laying and butt joint: At least two layers of frequency selective film to be spliced ​​are laid on the prepreg layer. The metal layer pattern edges between adjacent frequency selective films are butt jointed, and the butt joint gap width is controlled to be ≤0.1mm. S3. Preliminary compaction: Vacuum compaction is performed on the laid frequency selective membrane and prepreg; S4. Mesh preparation: Based on the pattern design of the frequency-selective film metal layer, a matching perforated mesh is prepared. S5. Conductive paste printing: The perforated screen is precisely aligned with the metal layer pattern at the joint gap, and the conductive paste is printed on the gap area using a stencil printing method, so that the metal layers on both sides of the frequency selective film form an electrical connection bridge through the conductive paste. S6. Continuity test: Use a DC low resistance tester to test the continuity resistance of the splicing area after printing. S7. Slurry curing: Curing the conductive slurry; S8. Continue molding: Continue to lay the same resin-based prepreg as in step S1 on the cured frequency selective film and splicing area and complete the overall molding, thus completing the co-curing or secondary bonding molding of the composite material component.

[0007] Furthermore, in step S4, the preparation of the screen includes the steps of stretching the screen, coating with photosensitive emulsion, exposure, and development.

[0008] Furthermore, the conductive paste is silver paste or copper paste, and its volume resistivity is not greater than 1×10⁻ 4 Ω·cm.

[0009] Furthermore, in step S2, the width of the butt joint gap is preferably 0.05 mm to 0.1 mm.

[0010] Furthermore, in step S3, the vacuum compaction temperature is 40-60℃, the vacuum degree is ≤-0.080MPa, and the time is 10-20 minutes.

[0011] Furthermore, in step S7, the curing method is one of room temperature curing, heat curing, or ultraviolet light curing.

[0012] Furthermore, the resin-based prepreg is one of cyanate ester resin quartz fiber prepreg, epoxy resin quartz fiber prepreg, epoxy resin glass fiber prepreg, and cyanate ester resin aramid fiber prepreg.

[0013] Furthermore, in step S5, the overlap width between the printed electrical connection bridge and the frequency-selective film metal layer patterns on both sides is 0.1-0.3 mm.

[0014] Furthermore, the frequency-selective film is a dielectric thin film with a periodic metal grid or patch array. Beneficial effects

[0015] Compared with the prior art, the present invention has the following significant advantages: 1. High-precision positioning: Through customized screen printing, conductive paste can be precisely printed in micron-level gaps, ensuring perfect connection with the original metal pattern and good dimensional consistency.

[0016] 2. Excellent electrical performance: The conductive paste (such as silver paste) has extremely low resistivity, resulting in a small resistance in the connecting bridge, which ensures excellent electrical continuity and signal transmission integrity at the splice.

[0017] 3. Good process compatibility: This method can be seamlessly integrated with processes such as composite prepreg laying and vacuum bag molding, and is suitable for co-curing or secondary bonding processes without introducing additional complex procedures.

[0018] 4. High reliability: The cured conductive paste has a strong connection and can withstand the high temperature and high pressure environment of composite material molding and the environmental stress in subsequent use, with good long-term stability.

[0019] 5. Significantly improves stealth performance: It effectively solves the problem of electrical continuity at the splicing point of the frequency selective film of the large antenna radome, ensuring uniform RCS performance of the entire radome and improving the stealth effectiveness of the aircraft. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a screen printing process according to an embodiment of the present invention.

[0021] Figure 2 This is a top view schematic diagram of the frequency-selective film splicing structure of the present invention.

[0022] Figure 3 yes Figure 2 A partially enlarged structural diagram.

[0023] Figure 4 yes Figure 2 The diagram shows a cross-sectional view of the frequency-selective membrane splicing structure.

[0024] Figure 5 This is a flowchart of the frequency-selective film metal layer electro-continuous splicing method.

[0025] In the figure: 1. Frequency selective film dielectric substrate; 2. Metal layer pattern; 3. Butt joint gap; 4. Perforated screen; 5. Squeegee; 6. Conductive paste; 7. Printed electrical connection bridge; 8. Bottom prepreg; 9. Top prepreg. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Example

[0027] As shown in 1-5, this embodiment takes the manufacturing of the side wall skin of a certain type of fighter jet radar radome as an example. The metal layer of the frequency selective film dielectric substrate 1 is a square grid structure.

[0028] A method for electrically continuous splicing of frequency-selective film metal layers includes the following steps: S1. A layer of cyanate ester resin quartz fiber prepreg is laid on the surface of the male mold 10 as a base (bottom prepreg 8). S2. Take two frequency selective films (frequency selective film substrate 1) with a width of 500mm, and lay them flat on the bottom prepreg 8 with the side with the metal mesh (metal layer pattern 2) facing up. The long sides of the two frequency selective films (frequency selective film substrate 1) are adjacent. Adjust their position so that the metal mesh (metal layer pattern 2) is aligned to form a butt joint with a width of 0.08mm. S3. Cover with the isolation film and vacuum bag, evacuate to -0.085MPa, and keep at 50℃ for 15 minutes to allow the frequency selective film (frequency selective film dielectric substrate 1) to be initially attached and fixed in position; S4. Based on the period and linewidth of the metal mesh (metal layer pattern 2) of the frequency selective film (frequency selective film substrate 1), design and manufacture a matching perforated screen 4. The manufacturing process of the perforated screen 4 includes: stretching a 300-mesh stainless steel mesh onto a frame, coating it with diazo photosensitive emulsion, exposing it to ultraviolet light using film with the corresponding pattern, and finally developing it to obtain a precise perforated pattern; S5. Remove the vacuum bag and precisely position the prepared perforated mesh 4 so that the perforated pattern on the perforated mesh 4 exactly crosses the butt joint 3 and overlaps the ends of the metal mesh (metal layer pattern 2) on both sides by about 0.2mm. Use the scraper 5 to apply the conductive silver paste 6 (resistivity 5×10⁻⁻⁻⁶). 5 Ω·cm) is scraped through the perforated screen 4, and the conductive paste 6 is deposited on the metal layer at the joint gap 3 through the perforated area to form a printed electrical connection bridge 7. S6. Use the four-probe method of a DC low resistance tester to measure the resistance of the splicing area, confirm that the continuity is good, and the additional resistance at the splicing point is less than 0.1Ω; S7. Allow the silver paste to stand at room temperature (25℃) for 24 hours to fully cure. S8. Continue to lay cyanate ester resin quartz fiber prepreg (upper prepreg 9) on the cured frequency selective film (frequency selective film dielectric substrate 1), and then carry out the standard vacuum bag-autoclave co-curing process to finally form the antenna radome skin component. Example

[0029] The difference between this embodiment and Embodiment 1 is that nano-copper conductive paste is used instead of conductive silver paste 6, and a thermosetting process is adopted.

[0030] In S5, nano-copper conductive paste is used for printing.

[0031] In S7, the component obtained in S6 is placed in an electric heating blower constant temperature drying oven and cured at 70°C for 30 minutes.

[0032] The remaining steps are the same as in Example 1. Tests show that this method can also achieve reliable electrical connections, and the cost is lower than that of the silver paste solution. Example

[0033] This embodiment demonstrates an adaptive method for surface splicing.

[0034] In S2, when laying the frequency selective film (frequency selective film medium substrate 1) on the double curvature mold, a segmented splicing method is adopted, and the gap width is controlled at 0.08mm.

[0035] In S4, the perforated screen 4 designs the pattern according to the unfolded diagram of the curved surface, and uses a flexible screen to adapt to the curved surface printing.

[0036] In S5, the printing uses a UV-curable conductive paste.

[0037] In S7, a conductive paste is cured by ultraviolet light. It is initially cured by irradiating it with a UVLED light source for 10 seconds, and then the final curing is completed at room temperature.

[0038] This method is particularly suitable for manufacturing complex curved radomes. Example

[0039] The difference between this embodiment and Embodiment 1 is that the cyanate ester resin quartz fiber prepreg in steps S1 and S8 is replaced by epoxy resin quartz fiber prepreg, while the remaining steps are the same as in Embodiment 1. Example

[0040] The difference between this embodiment and Embodiment 1 is that the cyanate ester resin quartz fiber prepreg in steps S1 and S8 is replaced by epoxy resin glass fiber prepreg, while the remaining steps are the same as in Embodiment 1. Example

[0041] The difference between this embodiment and Embodiment 1 is that the cyanate ester resin quartz fiber prepreg in steps S1 and S8 is replaced by cyanate ester resin aramid fiber prepreg, while the remaining steps are the same as in Embodiment 1.

[0042] The above embodiments demonstrate that the method of the present invention is flexible and reliable, can adapt to different material, process and structural requirements, and effectively realizes the electrical continuous splicing of frequency-selective film metal layers.

Claims

1. A method for electrically continuous splicing of frequency-selective film metal layers, characterized in that, Includes the following steps: S1. Substrate application: Apply at least one layer of resin-based prepreg to the molding die; S2. Frequency selective film laying and butt joint: At least two layers of frequency selective film to be spliced ​​are laid on the prepreg layer. The metal layer pattern edges between adjacent frequency selective films are butt jointed, and the butt joint gap width is controlled to be ≤0.1mm. S3. Preliminary compaction: Vacuum compaction of the paving material; S4. Mesh preparation: Based on the pattern design of the frequency-selective film metal layer, a matching perforated mesh is prepared. S5. Conductive paste printing: Align the perforated screen with the mating seam, and use a stencil printing method to print the conductive paste on the metal layer in the seam area to form an electrical connection bridge. S6. Continuity test: Detects the continuity resistance of the splicing area; S7. Slurry curing: Curing the conductive slurry; S8. Continue molding: Continue to lay the same resin-based prepreg as in step S1 on the cured frequency selective film and complete the overall molding.

2. The method according to claim 1, characterized in that, In step S4, the preparation of the screen includes stretching, coating with photosensitive emulsion, exposure, and development.

3. The method according to claim 1, characterized in that, The conductive paste is either silver paste or copper paste.

4. The method according to claim 3, characterized in that, The volume resistivity of the conductive paste is not greater than 1×10⁻ 4 Ω·cm.

5. The method according to claim 1, characterized in that, In step S2, the width of the butt joint gap is 0.05 mm to 0.1 mm.

6. The method according to claim 1, characterized in that, In step S3, the vacuum compaction temperature is 40-60℃, the vacuum degree is ≤-0.080MPa, and the time is 10-20 minutes.

7. The method according to claim 1, characterized in that, In step S7, the curing method is one of room temperature curing, heat curing, or ultraviolet light curing.

8. The method according to claim 1, characterized in that, The resin-based prepreg is one of the following: cyanate ester resin quartz fiber prepreg, epoxy resin quartz fiber prepreg, epoxy resin glass fiber prepreg, and cyanate ester resin aramid fiber prepreg.

9. The method according to claim 1, characterized in that, In step S5, the overlap width between the printed electrical connection bridge and the frequency-selective film metal layer pattern on both sides is 0.1-0.3 mm.

10. The method according to claim 1, characterized in that, The frequency-selective film is a dielectric thin film with a periodic metal grid or patch array.

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