Method for manufacturing highly bending-resistant flexible microwave antenna / filter

Abstract

The present invention relates to the field of flexible microwave antennas / filters, and more specifically, to a method for manufacturing a highly bendable flexible microwave antenna / filter. A metallic silver conductive layer, formed by laminating and hot-pressing two polyimide films with convex and concave surfaces, is stretched face-to-face in a flat state. The two metallic silver conductive layers are closely contacted and merged to form a single conductive layer, which is located within the hot-pressed polyimide film. Therefore, regardless of how the flexible microwave antenna / filter is bent, rubbed, wrinkled, or rubbed, the metallic silver conductive layer is protected by the polyimide film and prevented from thinning or cracking due to external friction, further enhancing its mechanical properties of bending and wear resistance.

Description

Technical Field

[0001] The present invention relates to the field of flexible microwave antennas / filters, and in particular to a method for manufacturing a highly bending-resistant flexible microwave antenna / filter. Background Art

[0002] Flexible electronics, an emerging electronics technology, has gained popularity and garnered increasing attention in recent years. In today's information-based society, flexible electronic devices often need to be integrated with flexible antennas to meet wireless connectivity requirements. Flexible microwave antennas / filters are crucial components of flexible wireless communication systems, and their performance directly impacts the overall system performance.

[0003] Flexible electronic structures inevitably endure repeated deformations such as stretching and bending during use. During this process, debonding and slippage may occur at the interface between the electronic device and the substrate, and failure of this interface often precedes the destruction of the material itself (see CN102393328A). Due to the distinct multi-material and multi-structural nature of the film / substrate structure, its fundamental fracture properties differ significantly from those of the bulk material. For example, fundamental fracture parameters such as fracture strength and toughness of the film are closely related to factors such as residual stress and thickness within the film. During the film growth process, the mismatch in the material properties of the film and substrate leads to significant residual stress in the film. This residual stress can reach or even exceed the yield strength of the film itself, and can also generate significant stress concentration at the film / substrate interface. Residual stress can significantly impact key film properties, such as resistance to spalling and delamination, fatigue life, and bonding strength.

[0004] like Figure 5 As shown, when the flexible microwave antenna / filter is in a bent state, the metal layer 1 attached to the flexible substrate 2 will be subjected to stress caused by bending and stretching. After repeated bending and stretching many times, microcracks will be caused, the resistivity will increase, and even an open circuit will occur, thereby affecting the electrical performance of the flexible microwave antenna / filter and its frequency characteristics will deviate from the predetermined value.

[0005] Our authorized patent ZL202010640641.9 discloses a method for manufacturing a flexible microwave filter. The core of the technical solution is that the method for manufacturing a flexible microwave filter includes the following steps:

[0006] (1) A computer is used to simulate and design a flexible microwave filter to obtain theoretical structural size parameters of the flexible microwave filter; (2) a room temperature wet process is used to manufacture the flexible microwave filter whose structural design has been completed in step (1); (3) the flexible bandpass filter obtained in step (2) is subjected to an electrical performance test and / or a mechanical performance test. If the test results deviate from the expected values, the parameters are adjusted, and the process returns to step (1) and / or (2) to re-manufacture the flexible microwave filter; if the test results meet the expected values, the parameters in steps (1) and (2) are fixed, and the flexible microwave filter is mass-produced.

[0007] The room temperature wet process of step (2) is implemented as follows:

[0008] (2-1) Surface modification of polyimide film using potassium hydroxide solution;

[0009] (2-2) using a silver ammonia solution to perform ion exchange on the surface of the polyimide film obtained in step (1);

[0010] (2-3) inkjet printing the desired flexible microwave filter pattern on the polyimide surface obtained in step (2-2);

[0011] (2-4) reducing the surface of the polyimide obtained in step (2-3) using hydrogen peroxide;

[0012] (2-5) Cleaning the polyimide film obtained in step (2-4).

[0013] Because the metallic silver conductive layer in authorized patent ZL202010640641.9 is obtained through a wet surface reaction, the adhesion between the metallic silver conductive layer and the polyimide film is good. Testing has shown that the flexible microwave filter can withstand thousands or even tens of thousands of bends without significantly degrading electrical performance. However, for practical applications, this is still insufficient, and further improvement in bending resistance is needed. Summary of the Invention

[0014] In order to solve the above technical problems, an object of the present invention is to provide a method for manufacturing a flexible microwave antenna / filter, so as to further improve the bending resistance of the flexible microwave antenna / filter.

[0015] The flexible microwave antenna / filter in the present invention is obtained through surface modification and in-situ self-metallization process. Its technical solution is as follows:

[0016] Identical patterned metal antennas are fabricated on two polyimide films of identical size and shape. Specifically, one polyimide film is bent to form a patterned metal antenna on its convex side; the other polyimide film is bent to form a patterned metal antenna on its concave side. The patterned metal antennas on the two films are identical in size and shape. This results in flexible microwave antennas / filters with patterned silver metal on the surfaces of two identical polyimide films.

[0017] The two polyimide films with patterned metal layers are stacked face to face in the same orientation in a flat state (the surfaces with patterned silver metal layers are bonded), and then hot-pressed to obtain the final flexible microwave antenna / filter.

[0018] Preferably, the two polyimide films are bent according to the same preset curvature radius.

[0019] Preferably, the manufacturing method of the flexible microwave antenna / filter comprises the following steps:

[0020] (0) Simulate the flexible microwave antenna / filter using HFSS simulation software, and optimize the structural parameters through simulation to obtain the theoretically optimized size parameters of the flexible microwave antenna / filter;

[0021] (1) The polyimide film is surface modified in a KOH solution, followed by ion exchange in an AgNO3 solution. After the reaction is complete, the polyimide film is cleaned and dried.

[0022] (2) Using the size parameters of the flexible microwave antenna / filter obtained in step (1), a mask layer is printed on the dried modified polyimide film, and then a reduction reaction is carried out in a H2O2 solution to obtain a flexible microwave antenna / filter with a metallized pattern on the surface of the polyimide film.

[0023] The manufacturing methods (1) and (2) of the flexible microwave antenna / filter are specifically as follows:

[0024] (1) Cut and select two pieces of polyimide films of exactly the same size and shape;

[0025] Two polyimide films were bent according to a preset curvature radius, and the convex and concave sides of the two polyimide films were modified in a KOH solution. Then, the convex and concave sides of the two polyimide films were ion-exchanged in an AgNO3 solution under the same bending conditions. After the reaction was completed, the polyimide films were cleaned and dried.

[0026] (2) Printing identical mask layers in the same direction on two polyimide films modified and dried in step (1), and then subjecting them to reduction reaction in H2O2 solution to obtain two identical polyimide film surface patterned metallized flexible microwave antennas / filters, which are then cleaned and dried separately;

[0027] After step (2), the following steps are also included:

[0028] (3) Two pieces of polyimide film are stacked face to face in the same orientation (the surfaces with patterned metal are laminated) in a flat state. Metal wire terminals are led out before stacking, and then hot-pressed to obtain the final flexible microwave antenna / filter.

[0029] It is worth noting that the manufacturing method of the flexible microwave antenna / filter proposed in the present invention is applicable to any flexible microwave antenna / filter, and is not limited to a certain flexible microwave antenna or a certain flexible microwave filter.

[0030] In the present invention, because the antenna structure is chemically grown from a polyimide substrate, it has excellent adhesion to the substrate and is less prone to cracking. Furthermore, because the metallic silver conductive layers prepared from the convex and concave sides of the two polyimide films are in two different states, respectively, when they are stretched flat and laminated and hot-pressed, the two metallic silver conductive layers will closely contact and merge to form a single conductive layer. Both layers will be subjected to certain bending compression stress and bending tensile stress, respectively. These two stresses will complement each other to a certain extent. Regardless of the direction in which the final laminated and hot-pressed flexible microwave antenna / filter is bent and stressed, the metallic silver conductive layer will remain tightly conductive, eliminating stress at any level. This results in overall stronger bending resistance, a greater number of trouble-free bending cycles, and greater conductive reliability. This technology is simple to process, does not require expensive equipment or vacuum conditions, and significantly reduces manufacturing costs.

[0031] Another unexpected advantage is that because the metallic silver conductive layers prepared from the convex and concave sides of two polyimide films are stretched face to face and stacked in a flat state and hot-pressed, the two metallic silver conductive layers will be in close contact and merge to form a conductive layer. The conductive layer is located inside the hot-pressed polyimide film. Therefore, no matter how the flexible microwave antenna / filter is bent, rubbed, wrinkled, or rubbed, the metallic silver conductive layer is protected by the polyimide film and will not be thinned or cracked by external friction, further enhancing its mechanical properties of bending resistance and wear resistance.

[0032] So far, the inventor has explained the working principle, technical solution and technical effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : Schematic diagram of the chemical process involved in the room temperature wet process of the present invention;

[0034] Figure 2 : Schematic diagram of the chemical process involved in the room temperature wet process of the present invention;

[0035] Figure 3 : A flexible microwave filter obtained by a room temperature wet process in the present invention;

[0036] Figure 4 : Figure 3 Bending test of flexible microwave filters;

[0037] Figure 5 : Bending state of flexible microwave antenna / filter;

[0038] Figure 6 : Schematic diagram of hot pressing molding of flexible microwave antenna / filter.

[0039] Among them: 1—metal layer, 2—flexible substrate. DETAILED DESCRIPTION

[0040] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is combined with the attached Figure 1-5 The specific embodiments, structures, features and functions of the present invention are described in detail below. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention pertains.

[0041] As a specific embodiment, a flexible dual-notch ultra-wideband antenna is produced using surface modification and in-situ self-metallization processes. The antenna has a bandwidth below -10 dB of 2.58 to 10.7 GHz and 2.5 to 10.87 GHz, respectively, notching the WiMAX and WLAN bands. The antenna maintains omnidirectional radiation at both 3.5 GHz and 5.5 GHz. The antenna's detailed structure is not a core feature of this invention and is irrelevant.

[0042] As a preferred embodiment, the flexible dual-notch ultra-wideband antenna is a flexible dual-notch ultra-wideband antenna, which is obtained based on surface modification and in-situ self-metallization process, as follows:

[0043] Before officially manufacturing the flexible microwave antenna, we first conduct design and simulation based on the expected performance indicators. We simulate the flexible dual-notch ultra-wideband antenna using HFSS simulation software, and optimize the structural parameters through simulation to obtain the theoretically optimized dimensional parameters of the flexible dual-notch ultra-wideband antenna.

[0044] The flexible microwave antenna with completed structural design is prepared using a room temperature wet process;

[0045] Cut and select two pieces of polyimide films with exactly the same size and shape;

[0046] One of the polyimide films was bent to a predetermined radius of curvature, and the convex side of the polyimide film was modified in a KOH solution. Subsequently, the convex side of the polyimide film was ion-exchanged in an AgNO3 solution while still in the same bent state. After the reaction, the polyimide film was cleaned and dried.

[0047] Another polyimide film is bent to the same predetermined curvature radius, and the concave side of the polyimide film is surface-modified in a KOH solution. Subsequently, the concave side of the polyimide film is ion-exchanged in an AgNO3 solution while still in the same bent state. After the reaction is complete, the polyimide film is cleaned and dried.

[0048] The same mask layer is printed in the same direction on two modified and dried polyimide films, and then a reduction reaction is carried out in a H2O2 solution to obtain two flexible dual-notch ultra-wideband antennas with identical polyimide film surface patterns metallized, which are then cleaned and dried separately.

[0049] The chemical reactions and steps involved in the above process can be found in Figure 1 and Figure 2 .

[0050] See also Figure 6 Then, the two polyimide films are laid flat, in the same orientation, face to face (the surfaces with patterned metal are laminated), the metal wire terminals are led out before lamination, and then hot-pressed to obtain the final flexible dual-notch ultra-wideband antenna.

[0051] The obtained flexible bandpass antenna is subjected to electrical performance testing. If the test results deviate from the expected values, the parameters are adjusted and the previous steps are returned to re-simulate the design or adjust the room temperature wet process parameters to re-manufacture the flexible microwave antenna. If the test results meet the expected values, the parameters in the previous steps are fixed and mass production of flexible microwave antennas is carried out.

[0052] The technique involves surface modification of a polyimide film (Qianfeng, Shanghai) in a KOH solution, ion exchange in an AgNO₃ solution (Aladdin, Shanghai), and reduction in a H₂O₂ solution, ultimately metallizing the polyimide film. All experimental steps were performed at room temperature.

[0053] The flexible dual-notch ultra-wideband antenna was simulated using HFSS simulation software, which is based on the finite element method. The simulated polyimide substrate had a thickness of 50.8 μm and a dielectric constant of 3.5. Structural parameters were optimized through simulation to achieve optimal performance. The flexible microwave antenna, whose structure was designed in the previous steps, was fabricated using a room-temperature wet process. The specific process is as follows:

[0054] After cleaning the polyimide films, the two polyimide films were bent according to a preset curvature radius. The convex side and the concave side of the two polyimide films were first immersed in a 4 mol / L KOH solution for 3 hours. This step ensures that the polyimide film is chemically modified into polyamic acid through the cleavage of the imide rings on the surface. Subsequently, the convex side and the concave side of the two polyimide films were immersed in 0.02 mol / LAgNO3 (99.8%) and NH3⋅H2O for 2 hours to ensure that K + Replaced with Ag + .

[0055] After cleaning and drying, the two treated polyimide films were attached to an A4 sheet of paper. Carbon ink was then printed onto the polyimide films using a standard printer to serve as a mask layer for silver reduction. The polyimide films with the printed mask pattern were then immersed in a 30% H2O2 solution to ensure complete reduction of the silver ions to silver.

[0056] Finally, the two polyimide films are stacked face to face in the same orientation (the surface with patterned metal is laminated) in a flat state. Preferably, metal wire terminals are led out before stacking, and then hot-pressed to obtain the final flexible dual-notch ultra-wideband antenna. Figure 6 shown.

[0057] The return loss of a flexible dual-notch ultra-wideband antenna fabricated via surface modification and in-situ self-metallization techniques was measured using a vector network analyzer (VNA, Agilent E8363C). The simulated bandwidth of this microwave antenna / filter, with a sub-10 dB loss, covers 2.58–10.7 GHz, with simulated notch bandwidths between 3.13–3.74 GHz and 5.07–5.95 GHz. The measured bandwidth covers 2.5–10.87 GHz, with notch bandwidths between 3.22–3.94 GHz and 4.99–6.04 GHz. Both the simulated and measured bandwidths of this microwave antenna / filter cover the standard 3.1–10.6 GHz ultra-wideband bandwidth and achieve blocking of both the WiMAX (3.3–3.7 GHz) and WLAN (5.15–5.825 GHz) bands. Furthermore, the stepped transition structure on the ground plane effectively blocks high-frequency frequencies.

[0058] As another embodiment, a flexible microwave filter is manufactured using a similar process as described above. Figure 3 shown.

[0059] Since it is hoped that the antenna can be integrated into flexible electronic devices, a bending test was conducted on the antenna's return loss. The antenna was placed close to two foam cylinders (ε r = 1) to simulate different degrees of bending, refer to Figure 4 .

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing a highly bend-resistant flexible microwave antenna / filter, characterized by: The flexible microwave antenna / filter is obtained based on surface modification and in-situ self-metallization process, and the manufacturing method specifically includes the following steps: (1) Cut and select two pieces of polyimide films of exactly the same size and shape; One of the polyimide films is bent according to a preset curvature radius, and the convex side of the polyimide film is surface-modified in a KOH solution. The convex side is then ion-exchanged in an AgNO3 solution. After the reaction is complete, the polyimide film is cleaned and dried. Another polyimide film is bent according to the same predetermined curvature radius, and the concave side of the polyimide film is surface-modified in a KOH solution. The concave side is then ion-exchanged in an AgNO3 solution. After the reaction is complete, the polyimide film is cleaned and dried. (2) Printing identical mask layers in the same direction on two polyimide films modified and dried in step (1), and then subjecting them to a reduction reaction in a H2O2 solution to obtain two identical polyimide film surfaces with patterned silver metal flexible microwave antennas / filters; (3) Two polyimide films are stacked face to face in the same orientation and with the patterned silver metal layer in a flat state. The wire terminals are first led out before stacking, and then hot-pressed to obtain the final flexible microwave antenna / filter.

2. The method for manufacturing a flexible microwave antenna / filter according to claim 1, wherein: Before step (1), the method further includes step (0): simulating the flexible microwave antenna / filter by using simulation software, and optimizing the structural parameters by simulation to obtain the theoretically optimized size parameters of the flexible microwave antenna / filter; the obtained size parameters are used for printing the mask layer in step (2).

3. The method for manufacturing a flexible microwave antenna / filter according to claim 1, wherein: The specific operation of step (1) is as follows: after the polyimide film is cleaned, the polyimide film is first immersed in a 4 mol / L KOH solution for 3 h; this step ensures that the polyimide film is chemically modified to polyamide acid through the cleavage of the imide ring on the surface; then, the surface-modified side of the film is immersed in 0.02 mol / L AgNO3 (99.8%) and NH3⋅H2O for 2 h to ensure that K + Replaced with Ag + ; Wash and dry.

4. The method for manufacturing a flexible microwave antenna / filter according to claim 1, wherein: In step (2), a conventional printer is used to print carbon ink on the polyimide film as a mask layer for reducing metallic silver; then, the polyimide film printed with the mask pattern is immersed in a H2O2 (30%) solution to ensure that the silver ions Ag + Completely reduced to metallic silver.

5. The method for manufacturing a flexible microwave antenna / filter according to claim 1, wherein: In step (2), two identical flexible microwave antennas / filters with patterned silver metal on the surface of polyimide films are obtained, and then cleaned and dried respectively.

6. The method for manufacturing a flexible microwave antenna / filter according to claim 1, wherein: In step (3), the metal wire terminals are first led out before lamination and then hot-pressed into shape.

7. A method for manufacturing a highly bend-resistant flexible microwave antenna / filter, characterized in that: The specific steps include: Identical patterned metal antennas are fabricated on two polyimide films of identical size and shape. Specifically, one of the polyimide films is bent to fabricate a patterned metal antenna on its convex side; the other polyimide film is bent to fabricate a patterned metal antenna on its concave side; the patterned metal antennas on the two films are identical in size and shape; thereby, two identical flexible microwave antennas / filters with patterned silver metal on the surface of the polyimide films are obtained; the two polyimide films with patterned metal layers are flattened, face-to-face, and stacked in the same orientation (the surfaces with the patterned silver metal layers are bonded together), and then hot-pressed to obtain the final flexible microwave antenna / filter.

8. The method for manufacturing a flexible microwave antenna / filter according to claim 7, wherein: The two polyimide films are bent according to the same preset curvature radius.

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