A method for manufacturing a large-area flexible stretchable conformal antenna

Abstract

The application aims to provide a preparation method of a large-area flexible stretchable conformal antenna, and belongs to the technical field of flexible antenna preparation. The method innovatively prepares a substrate based on a metal foil / polyimide / silicone rubber, performs ablation on the surface of the metal foil / polyimide by laser to realize patterning, and thus realizes the preparation of a large-area conformal antenna. The preparation method has processability for most metal foil materials, and the tensile property of the metal foil material is improved under the enhancement of the polyimide, and the preparation method can be used for large-area preparation.

Description

Technical Field

[0001] This invention belongs to the field of flexible antenna fabrication technology, specifically relating to a method for fabricating a large-area flexible stretchable conformal antenna. Background Technology

[0002] With the widespread application of radar antennas in the aerospace field, traditional rigid antennas, limited by their size and rigidity, have significant limitations in their placement on spacecraft surfaces, easily leading to blind spots. Conformal antennas can effectively solve these problems. Conformal antennas place the antenna elements on the surface of the aircraft, such as the fuselage or wings. This arrangement expands the effective placement area of ​​the antenna and greatly reduces blind spots.

[0003] Currently, there are two main methods for fabricating conformal antennas: One is the transfer printing method, which involves laser processing of metal materials to form antenna patterns, transferring these patterns onto a flexible, stretchable substrate, and then attaching the integrated antenna to the aircraft surface (An Improved Fabrication Technique for the 3-D Frequency Selective Surface based on Water Transfer Printing Technology). However, this method is limited by the stamp area, making it difficult to fabricate large-area conformal antennas. Only small-area antenna splicing can be used to achieve large-area antenna fabrication. This splicing method limits antenna performance and makes antenna installation more difficult. The second method involves directly etching metal antenna patterns onto substrates such as polyimide or rigid circuit boards. However, antennas fabricated using this method lack stretchability due to the substrate material limitations, making conformal antenna applications difficult. Furthermore, if metal is attached to a stretchable substrate such as silicone rubber, it is impossible to use laser processing to create antenna patterns, thus failing to obtain a conformal antenna (Compact and Directional Printed Dipole Antenna Pair Conformed on a Conical Surface).

[0004] Therefore, how to fabricate large-area conformal antennas based on flexible and stretchable substrates has become a difficult problem that urgently needs to be overcome in engineering applications. Summary of the Invention

[0005] To address the problems existing in the background technology, the present invention aims to provide a method for fabricating a large-area flexible stretchable conformal antenna. This method innovatively first prepares a substrate based on metal foil / polyimide / silicone rubber, and then uses a laser to ablate the surface of the metal foil / polyimide to achieve patterning, thereby realizing the fabrication of a large-area conformal antenna.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for fabricating a large-area flexible stretchable conformal antenna includes the following steps:

[0008] Step 1: Clean the metal foil with alcohol and deionized water in sequence using ultrasonic cleaning, then dry it. Then, apply a layer of hot melt adhesive film to the surface of the cleaned metal foil using a hot roll pressing method. Place the polyimide film on the surface of the hot melt adhesive film and then perform hot roll pressing to bond them together.

[0009] Step 2: Apply an alkaline treatment to the polyimide surface after bonding in Step 1. The alkali will destroy the polyimide molecular chain structure, causing carboxyl groups to be generated on its surface, which will then react with the amino groups in the next step. That is, apply an alkaline solution with a concentration of 1-3 mol / L to the polyimide surface and let it stand for 10-20 minutes.

[0010] Step 3: Immerse the sample treated with alkali in Step 2 in a solution of silane coupling agent with amino active groups, wherein the concentration of the silane coupling agent solution with amino active groups is 0.1-0.5 mol / L, the immersion time is 5-20 min, after immersion, take it out and blow dry the sample surface with nitrogen gas.

[0011] Step 4: Coat the release film surface with liquid silicone rubber and heat to cure, forming a silicone rubber layer;

[0012] Step 5: The silicone rubber surface obtained in Step 4 and the polyimide surface obtained in Step 3 are subjected to oxygen plasma treatment. After the treatment, the silicone rubber is attached to the polyimide surface, the release film is removed, and then baked at a temperature of 60-80℃ for 1-3 hours to obtain a single-sided composite substrate consisting of metal foil, polyimide and silicone rubber from top to bottom.

[0013] Step 6: The antenna pattern is prepared on the single-sided composite substrate obtained in Step 5 using a laser processing method, so that the metal foil layer and the polyimide layer in the composite substrate have the same pattern structure, and the desired conformal antenna can be prepared.

[0014] Furthermore, in step 1, the material of the metal foil is copper foil, aluminum foil, alloy foil, or other foil materials.

[0015] Furthermore, the parameters for the two hot rolling processes in step 1 are the same: the hot rolling temperature is 80-120℃ and the pressure is 5-14MPa.

[0016] Furthermore, the alkaline solution in step 2 is a strongly alkaline solution such as sodium hydroxide or potassium hydroxide.

[0017] Furthermore, in step 3, the silane coupling agent for the amino active group can be γ-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane.

[0018] Furthermore, the coating process in step 4 can employ screen printing, blade coating, or slot coating techniques.

[0019] Furthermore, the laser used in step 6 can be a picosecond laser or a nanosecond laser in the ultraviolet band.

[0020] This invention also provides a method for fabricating a double-layer flexible stretchable conformal antenna, comprising the following steps:

[0021] Step 1: Overlap the silicone rubber layers of the two single-sided composite substrates obtained by the preparation method according to the above claims, and then apply pressure to cure them to obtain a double-sided composite substrate;

[0022] Step 2: The double-sided composite substrate obtained in Step 1 is processed by laser processing to prepare antenna patterns on the upper and lower surfaces in sequence, so that the metal foil layer and polyimide layer in the composite substrate have the same pattern structure, and the desired conformal antenna can be prepared.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] 1. This invention prepares a composite substrate of metal foil / polyimide / silicone rubber, with polyimide serving as an reinforcing layer between the metal foil layer and the silicone rubber layer. This allows the substrate to be directly patterned using laser technology. Simultaneously, the polyimide layer and the metal foil layer have the same pattern, enhancing the fracture resistance of the metal foil layer. The tensile strength at break of pure copper foil is less than 5%, while that of PI-reinforced copper foil is less than 8%, meaning that the mechanical properties of pure copper foil are significantly lower than those reinforced with PI.

[0025] 2. This invention enhances the adhesion between the polyimide layer and the silicone rubber layer by introducing a silane coupling agent. Specifically, the polyimide surface generates carboxyl groups through an alkaline solution, which react chemically with the amino groups of the silane coupling agent. Then, oxygen plasma treatment causes hydroxyl active groups to be generated on the surfaces of the polyimide and silicone rubber grafted with the silane coupling agent. After bonding, a dehydration condensation reaction occurs to form chemical bonds, resulting in stronger adhesion than a simple metal foil layer and silicone rubber layer or a polyimide layer and silicone rubber layer. This makes it more suitable for the application environment of conformal antennas.

[0026] 3. In the fabrication of a double-layer stretchable antenna with interlayer electrical interconnection requirements, this invention uses a laser drilling-black hole process-electroplating process to achieve electrical interconnection between heterogeneous circuits, thereby realizing the fabrication of a double-sided flexible stretchable conformal antenna.

[0027] The above three points enable the preparation method of the present invention to be processable for most metal foils, and the tensile properties of the metal foils are improved by the reinforcement of polyimide. At the same time, the preparation method can be used for large-area preparation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the double-layer flexible stretchable conformal antenna of Embodiment 2 of the present invention.

[0029] In the diagram, 1 is the top antenna pattern layer, 2 is the top polyimide layer, 3 is the silicone rubber layer, 4 is the bottom polyimide layer, and 5 is the bottom antenna pattern layer. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0031] Example 1

[0032] A single-layer, large-area, flexible, stretchable conformal antenna includes the following steps:

[0033] Step 1: Clean the metal foil sequentially with alcohol and deionized water using ultrasonic cleaning for 5 minutes, then dry it to remove dirt and impurities from the surface of the metal foil; then apply a layer of hot melt adhesive film to the surface of the cleaned metal foil using a hot roll pressing method at a rolling temperature of 120℃ and a pressure of 10MPa; finally, place a polyimide film on the surface of the hot melt adhesive film and perform hot roll pressing to bond them together at a rolling temperature of 120℃ and a pressure of 10MPa.

[0034] Step 2: Treat the polyimide surface after bonding in Step 1 with an alkali, i.e., apply a 3 mol / L potassium hydroxide solution to the polyimide surface and let it stand for 1 minute.

[0035] Step 3: Immerse the sample treated with alkali in Step 2 in a solution of silane coupling agent with a concentration of 0.3 mol / L amino active groups for 5 minutes. After immersion, remove the sample, remove excess silane coupling agent with alcohol, and dry the surface with nitrogen.

[0036] Step 4: Apply liquid silicone rubber to the surface of the PET release film using a doctor blade coating technique, and cure at 60°C for 3 hours to obtain a silicone rubber layer;

[0037] Step 5: The silicone rubber surface obtained in Step 4 and the polyimide surface obtained in Step 3 are subjected to oxygen plasma treatment. The oxygen plasma treatment power is 180W, the gas source is oxygen, and the treatment time is 120s. After the treatment, the silicone rubber is attached to the polyimide surface, the release film is removed, and then it is baked at 60℃ for 3 hours to improve the stability of the interface, thus obtaining a composite substrate consisting of metal foil, polyimide and silicone rubber from top to bottom.

[0038] Step 6: The composite substrate obtained in Step 5 is processed using a nanosecond laser to prepare an antenna pattern, so that the metal foil layer and the polyimide layer in the composite substrate have the same pattern structure, thus obtaining the desired conformal antenna.

[0039] Example 2

[0040] A schematic diagram of a double-layer, large-area, flexible, stretchable conformal antenna is shown below. Figure 1 As shown, from top to bottom, they are: top antenna pattern layer 1, top polyimide layer 2, silicone rubber layer 3, bottom polyimide layer 4, and bottom antenna pattern layer 5.

[0041] The fabrication method of a double-layer large-area flexible stretchable conformal antenna includes the following steps:

[0042] Step 1. Overlap the silicone rubber layers of two single-sided composite substrates prepared according to the method in Example 1, and then apply pressure to cure them at a pressure of 10 MPa to obtain a double-sided composite substrate;

[0043] Step 2: The copper / polyimide layers on the upper and lower surfaces of the double-sided composite substrate from Step 1 are processed with nanosecond lasers to prepare antenna patterns, so that the metal foil layer and the polyimide layer in the composite substrate have the same pattern structure, thus obtaining the desired double-layer conformal antenna.

[0044] Example 3

[0045] A single-sided copper-clad laminate dielectric substrate was prepared according to the steps of Example 1, except that the concentration of the aminosilane coupling agent solution in step 3 was adjusted to 0.3 mol / L, while the other steps remained unchanged. A 90-degree peel test was performed on the prepared substrate, and the peel strength obtained was 0.5 N / mm.

[0046] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for fabricating a large-area flexible stretchable conformal antenna, characterized in that, Includes the following steps: Step 1: Clean the metal foil with alcohol and deionized water in sequence using ultrasonic cleaning, then dry it. Then, apply a layer of hot melt adhesive film to the surface of the cleaned metal foil using a hot roll pressing method. Place the polyimide film on the surface of the hot melt adhesive film and then perform hot roll pressing to bond them together. Step 2: Perform alkali treatment on the polyimide surface after bonding in Step 1. The specific process is as follows: apply an alkaline solution with a concentration of 1-3 mol / L to the polyimide surface and let it stand for 10-20 minutes. Step 3: Immerse the sample treated with alkali in Step 2 in a solution of silane coupling agent with amino active groups, wherein the concentration of the silane coupling agent with amino active groups is 0.1-0.5 mol / L, the immersion time is 5-20 min, after immersion, take it out and blow dry the sample surface with nitrogen gas. Step 4: Coat the release film surface with liquid silicone rubber and heat to cure, forming a silicone rubber layer; Step 5: Perform oxygen plasma treatment on the silicone rubber surface obtained in Step 4 and the polyimide surface obtained in Step 3. After the treatment, attach the silicone rubber to the polyimide surface, remove the release film, and then bake it at a temperature of 60-80℃ for 1-3 hours. This will give you a single-sided composite substrate consisting of metal foil, polyimide, and silicone rubber from top to bottom. Step 6: The antenna pattern is prepared on the single-sided composite substrate obtained in Step 5 using a laser processing method, so that the metal foil layer and the polyimide layer in the composite substrate have the same pattern structure, and the desired conformal antenna can be prepared.

2. The method for fabricating a large-area flexible stretchable conformal antenna as described in claim 1, characterized in that, The material of the metal foil in step 1 is copper foil, aluminum foil, or alloy foil.

3. The method for fabricating a large-area flexible stretchable conformal antenna as described in claim 1, characterized in that, The parameters for the two hot rolling processes in step 1 are the same: the hot rolling temperature is 80-120℃ and the pressure is 5-14MPa.

4. The method for fabricating a large-area flexible stretchable conformal antenna as described in claim 1, characterized in that, The alkaline solution in step 2 is a sodium hydroxide or potassium hydroxide solution.

5. The method for fabricating a large-area flexible stretchable conformal antenna as described in claim 1, characterized in that, In step 3, the silane coupling agent for the amino active group is selected from γ-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane.

6. The method for fabricating a large-area flexible stretchable conformal antenna as described in claim 1, characterized in that, The coating process in step 4 uses screen printing, blade coating, or slot coating techniques.

7. The method for fabricating a large-area flexible stretchable conformal antenna as described in claim 1, characterized in that, The laser used in step 6 is a picosecond laser or a nanosecond laser in the ultraviolet band.

8. A method for fabricating a large-area flexible stretchable double-layer conformal antenna, characterized in that, Includes the following steps: Step 1. Overlap the silicone rubber layers of two single-sided composite substrates obtained by the preparation method according to any one of claims 1-7, and then apply pressure to cure them to obtain a double-sided composite substrate; Step 2. The double-sided composite substrate obtained in Step 1 is processed using a laser processing method to prepare an antenna pattern, so that the metal foil layer and the polyimide layer in the composite substrate have the same pattern structure, thus obtaining the desired double-layer conformal antenna.

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