Metamaterial honeycomb and preparation method thereof

Abstract

The invention discloses a metamaterial honeycomb and a preparation method thereof, and relates to the technical field of honeycombs, and the preparation method comprises the steps: S1, preparing a copper circuit pattern on a PI film through laser maskless photoetching; s2, node glue is applied to related positions of the copper circuit pattern; s3, combining the PI film with the glue layer coated with the node glue in a stacking hot-pressing manner; s4, curing the cellular board formed by the node glue; s5, stretching and shaping the honeycomb plate to form a honeycomb shape; and S6, carrying out gum dipping and curing on the stretched and shaped honeycomb to obtain the metamaterial honeycomb. According to the method, the idea of patterning first and then integrating the honeycomb is adopted, a traditional post-etching method is replaced, meanwhile, a laser direct writing method is used for replacing a traditional conductive ink spraying mode, the technical problems that honeycomb hole grid wall micropatterns are unstable, combination is poor and the like can be effectively solved, and the method has the advantages of being convenient to implement and high in conductive reliability; and the hole walls of the honeycomb grids have the advantage of stable microstructure patterns.

Description

Technical Field

[0001] This invention relates to the field of cellular technology, and more specifically, to a metamaterial cellular structure and its preparation method. Background Technology

[0002] Honeycomb sandwich materials, due to their unique hexagonal pore structure, exhibit significant advantages in electromagnetic functional design: when electromagnetic waves are incident, the multiple reflections and scattering formed within the pores effectively extend the propagation path (increasing the path length by 3-5 times). Combined with gradient-filled absorbing agents (such as carbon black / carbon nanotubes), broadband absorption (absorption rate >90%) can be achieved in the 2-18 GHz frequency band. By adjusting parameters such as the honeycomb wall thickness (δ=0.1-0.5 mm) and pore side length (L=2-8 mm), the equivalent dielectric constant (εeff≈1.5-3.2) can be optimized, improving impedance matching performance.

[0003] Currently, besides optimizing structural parameters such as pore size, thickness, and side length, methods to modify the electromagnetic properties of honeycomb cells include impregnating them with absorbing agents to improve absorption performance. However, uneven distribution of the absorbing agent within the honeycomb pores leads to fluctuations in the dielectric constant, easily causing resonant point shifts. Filling the honeycomb pores with absorbing foam negates the advantages of lightweight and high strength inherent in air-cavity honeycombs. Therefore, fabricating metamaterial patterns on the honeycomb pore walls to modulate electromagnetic properties while maintaining the advantages of the air-cavity honeycomb structure has become the most promising approach. However, currently, limitations in pore size and thickness make it difficult to fabricate complete patterns on the pore walls, resulting in significant engineering challenges and unstable conductivity. If inkjet printing is used to fabricate conductive patterns, the pattern accuracy will be limited by ink diffusion (accuracy ≥ 50 μm), and the conductive adhesive / ink affects the bonding strength of the nodes, leading to insufficient reliability.

[0004] Therefore, how to solve the technical problems of unstable micro-patterns and poor bonding in honeycomb cell walls has always been a goal that the industry urgently needs to improve. Summary of the Invention

[0005] The main objective of this invention is to provide a metamaterial honeycomb and its preparation method to solve the technical problems of unstable micropatterns and poor bonding in the existing honeycomb pore wall.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a method for preparing a metamaterial honeycomb is provided, comprising the following steps: S1, copper circuit patterns are prepared on the PI film using laser maskless photolithography; S2, apply node adhesive to the relevant positions of the copper circuit pattern; S3, the bonding between the PI film and the adhesive layer of the applied node adhesive is achieved by stacking and hot pressing; S4, Curing the honeycomb panel formed by the node adhesive; S5, the honeycomb panel is stretched and shaped to form a honeycomb shape; S6, the stretched and shaped honeycomb is impregnated and cured with resin to obtain the metamaterial honeycomb.

[0007] Furthermore, in step S1, the laser wavelength used in the laser maskless lithography is 266–1550 nm, the laser direct writing accuracy is 5–200 μm, the laser power is 5–30 W, the line width of the copper circuit pattern is 10–200 μm, and the thickness is 5–20 μm.

[0008] Furthermore, in step S2, the node adhesive is applied to the gaps in the copper circuit pattern using a screen printing machine. The squeegee angle of the screen printing machine is 45-60°, the pressure is 0.3-0.5MPa, and the speed is 10-100mm / s.

[0009] Furthermore, in step S2, after the application of the joint adhesive is completed, the joint is dried in a tunnel oven at a temperature of 80-150°C.

[0010] Furthermore, in step S2, the distance between the node adhesive and the copper circuit pattern is ≥1mm.

[0011] Furthermore, in step S3, the stacking hot pressing method includes alternating layers of node adhesive on the sample obtained in step S2, and then placing it in a hot press for hot pressing.

[0012] Furthermore, in step S3, the hot pressing temperature of the hot press is 100–200℃, the pressure is 0.5–2MPa, and the pressing time is 1–3h.

[0013] Further, in step S4, the sample obtained in step S3 is cooled at room temperature for 1-6 hours to allow the node adhesive to cure and form the honeycomb panel.

[0014] Furthermore, in step S5, a servo-controlled stretching machine is used to stretch and shape the honeycomb panel formed in step S4. The stretching rate is 5-10 mm / min, the side length of the stretched holes is 1-8 mm, and the holding time is 6-8 h.

[0015] According to a second aspect of the present invention, a metamaterial honeycomb is provided, which is prepared by the above-described preparation method.

[0016] The preparation method disclosed in this invention adopts the idea of ​​patterning first and then integrating the honeycomb, replacing the traditional post-etching method. At the same time, the laser direct writing method is used instead of the traditional spraying conductive ink method. This can effectively solve the technical problems such as unstable micro-patterns and poor bonding of honeycomb cell walls. It has the advantages of being easy to implement and having high conductivity reliability. In addition, the honeycomb cell walls have the advantage of stable micro-structure patterns. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the steps involved in the preparation of metamaterial honeycomb in an embodiment of the present invention.

[0018] Figure 2 This is a flowchart illustrating the fabrication process of metamaterial honeycomb in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the electromagnetic test results of the metamaterial honeycomb sidewall resonant ring in an embodiment of the present invention.

[0020] Figure 4 As described in the embodiments of the present invention Figure 1 A schematic diagram of the electromagnetic test results of the sample obtained in step S1.

[0021] Figure 5 As described in the embodiments of the present invention Figure 1 The sample obtained in step S1 is a physical test image of the tape test.

[0022] Figure 6 In another embodiment of the present invention, the invention utilizes... Figure 1 Schematic diagrams of different honeycomb cell wall patterns prepared by the method steps.

[0023] Figure 7 In another embodiment of the present invention, the invention utilizes... Figure 1 Schematic diagrams of different honeycomb cell wall patterns prepared by the method steps. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0026] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0027] As described in the background section of this invention, existing technologies suffer from unstable micropatterns and poor bonding in honeycomb lattice walls. To address these issues, in a typical embodiment of this invention, a method for preparing metamaterial honeycombs is provided, the steps of which are illustrated in the schematic diagram below. Figure 1 As shown, it includes the following steps: S1, copper circuit patterns are prepared on the PI film using laser maskless photolithography; S2, apply node adhesive to the relevant positions of the copper circuit pattern; S3, the bonding between the PI film and the adhesive layer of the applied node adhesive is achieved by stacking and hot pressing; S4, Curing the honeycomb panel formed by the node adhesive; S5, the honeycomb panel is stretched and shaped to form a honeycomb shape; S6, the stretched and shaped honeycomb is impregnated and cured with resin to obtain the metamaterial honeycomb.

[0028] The method described in this invention allows for the direct fabrication of patterns on a PI film before honeycomb formation. By employing the approach of patterning before integrating the honeycomb, the traditional post-etching method is replaced. Furthermore, the laser direct writing method replaces the traditional spraying of conductive ink. This effectively solves technical problems such as unstable micro-patterns and poor bonding in the honeycomb cell walls. It has the advantages of being easy to implement and having high conductivity reliability. In addition, the honeycomb cell walls have the advantage of stable micro-structure patterns.

[0029] In step S1, the laser wavelength used in laser maskless lithography is 266–1550nm, more preferably ultraviolet light 266 / 355nm, the laser direct writing accuracy is 5–200μm, more preferably 10–50μm, the laser power is 5–30W, the line width in the copper circuit pattern is 10–200μm, and the thickness is 5–20μm. The advantage of using laser maskless lithography in step S1 is that it solves the ink diffusion problem of ≥50μm in traditional inkjet printing, achieves more precise pattern processing, and controls the electromagnetic range.

[0030] In this embodiment, the polyimide (PI) film possesses irreplaceable electromagnetic properties, including: a stable dielectric constant (εr=3.2-3.5, fluctuation <5%) in the 1-40GHz high-frequency range, extremely low loss tangent (tanδ=0.002-0.008), which can avoid resonant frequency drift, and excellent temperature resistance (Tg>360℃) and coefficient of thermal expansion (CTE=3-5ppm / ℃) that match the metal pattern material, ensuring dimensional stability during the hot pressing process (150-200℃). Using it as a honeycomb substrate can not only make full use of its excellent electromagnetic properties, but also provide an ideal substrate for micron-scale patterns with its ultra-smooth surface (roughness Ra<0.1μm).

[0031] In this embodiment, step S1 is a laser direct writing (i.e., laser maskless lithography) technology, which has ultra-high precision processing capabilities, more flexible design freedom, higher material compatibility and functional expansion. The metamaterial honeycomb fabrication method of this invention uses laser maskless lithography, which uses a computer-controlled focused laser beam to directly achieve high-precision patterning on the substrate surface, eliminating the mask fabrication and alignment steps of traditional lithography. This provides reliable technical support for the fabrication of highly conductive and stable micron-level patterns on the honeycomb lattice walls. The laser direct writing technology used in step S1 successfully fabricates highly conductive copper microstructure patterns on polyimide (PI) films, solving the technical problems of low conductivity, insufficient pattern accuracy, and insufficient adhesion to the substrate caused by traditional sprayed conductive inks. By modifying the structure of the laser-written copper circuit pattern (e.g., shape, thickness), the electromagnetic performance of the honeycomb at different frequencies can be controlled.

[0032] In this embodiment, a layer of photoresist (negative resist) is first imprinted on a PI copper-clad laminate using a rolling mill. The sample is then selectively exposed using an ultraviolet laser direct writing system with a laser power of 5-30W, a spot diameter of 10-100μm, and a scanning speed of 100-1000mm / s. After development and etching, a copper circuit pattern with a line width of 10-200μm is obtained on the PI film.

[0033] In step S2, a screen printing machine is used to apply a node adhesive to the gaps in the copper circuit pattern. The squeegee angle of the screen printing machine is 45-60°, the pressure is 0.3-0.5MPa, and the speed is 10-100mm / s. In this embodiment, the screen printing machine is a high-precision screen printing machine with a screen aperture of 100-2000μm. The node adhesive used is XJ-453 epoxy adhesive with a viscosity of 5000cP. This invention uses a high-precision screen printing machine to accurately apply node adhesive to the relevant positions of the copper circuit pattern (i.e., the gaps in the copper circuit pattern), with an adhesive layer thickness of 0.1–0.5mm.

[0034] In this embodiment, in step S2, after the nodal adhesive is applied, the material is dried in a tunnel oven at a temperature of 80-150°C. The gap between the nodal adhesive and the edge of the copper circuit pattern is ≥1mm; this spacing design avoids interference between the conductive layer and the adhesive layer. This invention uses screen printing of the nodal adhesive to precisely position the copper circuit pattern, and the nodal adhesive is brushed into the gaps between the copper circuit patterns, resulting in metamaterials with stable and reliable electromagnetic properties.

[0035] In step S3, the hot-pressing method includes alternating layers of adhesive for the sample obtained in step S2, followed by hot pressing in a hot press to cure the adhesive. The hot pressing temperature of the hot press is 100–200℃ (optimal hot pressing temperature is 150–180℃), the pressure is 0.5–2MPa (optimal pressure is 1–1.5MPa), and the pressing time is 1–3h. By designing the specific range of these hot-pressing integrated parameter values, a high-strength bond between the PI film and the adhesive layer can be achieved.

[0036] In step S4, the sample obtained in step S3 is cooled to room temperature for 1-6 hours to allow the node adhesive to cure and form a honeycomb panel.

[0037] In step S5, a servo-controlled stretching machine is used to stretch and shape the honeycomb board formed in step S4. The stretching rate is 5-10 mm / min, the side length of the stretched cells is 1-8 mm, and the holding time is 6-8 h. By designing the specific range of these stretching parameter values ​​of the servo-controlled stretching machine, uniform stretching can be achieved, ensuring that the copper circuit pattern on the honeycomb cell wall remains intact and undamaged, thus forming a complete honeycomb shape.

[0038] In step S6, the stretched and shaped honeycomb is impregnated and cured with epoxy resin to obtain a metamaterial honeycomb. In this embodiment, while maintaining the honeycomb in its shaped state, epoxy resin is impregnated. After the resin stops dripping and sliding down, it is cured at 150-200°C for 3 hours to obtain the metamaterial honeycomb.

[0039] In this embodiment, a phased curing process is implemented. The first phase involves the curing of the node adhesive. The sample obtained in step S2 is subjected to alternating layers of node adhesive and then placed in a hot press for hot pressing. The hot pressing temperature is 100–200℃ (optimal hot pressing temperature is 150–180℃), the pressure is 0.5–2MPa (optimal pressure is 1–1.5MPa), and the pressing time is 1–3h, thereby achieving node adhesive curing. The second phase involves impregnation curing. In step S6, the honeycomb after stretching and shaping is impregnated with epoxy resin. After the resin stops dripping and sliding down, it is cured at 150–200℃ for 3h. By implementing phased curing, the node adhesive curing and impregnation curing are separated, which can prevent the copper circuit pattern on the honeycomb cell wall from breaking or deforming due to stretching deformation.

[0040] Please see Figure 2 This is a flowchart illustrating the fabrication process of metamaterial honeycomb in an embodiment of the present invention.

[0041] like Figure 2 As shown, 1 is the PI substrate, 2 is the copper circuit pattern after development and etching, and 3 is the screen-printed node adhesive. (Combined) Figure 1 The fabrication method shown, and the detailed implementation process of the technical solution of this invention, includes: coating photoresist on a PI copper-clad laminate (copper thickness 6-18 μm), selectively exposing the PI film using laser (i.e., ultraviolet light) direct writing technology, and obtaining a periodic open-loop resonant ring (i.e., a linewidth of 50-100 μm) through development and etching. Figure 2 As shown in 2), it serves as a copper circuit pattern; screen printing is used on the copper circuit pattern (i.e. Figure 2 As shown in step 2), XJ-453 honeycomb node adhesive is applied to the middle section. After the XJ-453 honeycomb node adhesive is applied, it is dried in a tunnel oven (80-150℃). The prepared PI film is then laminated with staggered node adhesive layers. High-strength bonding between the PI film and the adhesive layer is achieved by hot pressing at a temperature of 100-200℃, a pressure of 0.5-2MPa (optimal 1-1.5MPa), and a pressing time of 1-3h. The cured honeycomb laminate is stretched to the required shape and size and impregnated with epoxy resin while in a stretched state. After the resin stops dripping and sliding down, it is cured at 150-200℃ for 3h to obtain the metamaterial honeycomb.

[0042] Please see Figure 3 This is a schematic diagram of the electromagnetic test results of the metamaterial honeycomb sidewall resonant ring in an embodiment of the present invention.

[0043] like Figure 3 As shown, the above-mentioned Figure 1 The metamaterial honeycomb prepared by this method has a honeycomb aperture of 1.83 mm, an open resonant ring linewidth of 100 μm, and a period of 1 mm. For comparison with low-conductivity ink, the ink pattern linewidth was set to 150 μm (assuming diffusion ±25 μm). The copper circuit pattern conductivity was set to 5e7 (S / m), while the conductivity of the conductive ink was 5e5 (S / m). However, conductive ink typically has a conductivity lower than 5e5 (S / m), resulting in poorer electromagnetic properties. Figure 3 shows the results at 100 μm high conductivity, exhibiting one main peak and multiple resonant peaks. As the linewidth increases, the resonant peaks shift and their intensity weakens. At the same linewidth, a decrease in conductivity leads to an overall decrease in the intensity of S21.

[0044] Please see Figure 4 This is an embodiment of the present invention. Figure 1 A schematic diagram of the electromagnetic test results of the sample obtained in step S1.

[0045] like Figure 4 As shown, Figure 1 The copper circuit pattern in the sample obtained in step S1 is Figure 2 The periodic open-circuit resonator shown is illustrated using only [specific technology / method] to better highlight the manufacturing process effects of this invention. Figure 1 The sample results obtained in step S1 were subjected to simulation testing. Specifically, a single PI film with a copper circuit pattern (i.e., a periodic open resonant ring 2) was subjected to electromagnetic simulation testing. The test results are shown in Figure 4. It can be seen that, under the condition of equal conductivity, increasing the linewidth will cause the resonant point to shift to the right. Under the condition of constant linewidth, decreasing conductivity will lead to a decrease in resonance intensity. It can be seen that the preparation method of the present invention can prepare stable and high-conductivity copper circuit patterns. However, the traditional inkjet printing method cannot prepare precise and accurate patterns due to poor conductivity and ink diffusion, which leads to a decrease in electromagnetic performance.

[0046] According to the current national standard test standard GB / T40262—2021 "Determination of Metallic Layer Adhesion of Metal-Coated Fabrics - Tape Method", the material prepared in this invention... Figure 2 The copper circuit pattern shown (i.e., a periodic open-circuit resonator) achieves a bonding strength with the substrate that meets the highest level, Level 5 standard. Figure 5 The image shown is a physical test result demonstrating the effectiveness of the tape test.

[0047] Please see Figure 6 In another embodiment of the present invention, the following is utilized: Figure 1 Schematic diagrams of different honeycomb cell wall patterns prepared by the method and steps described. Specific implementation methods and... Figure 1 The methods and steps are roughly the same, the only difference is that... Figure 1 The copper circuit pattern in the sample obtained by method step S1 is Figure 2 The periodic open resonant ring shown is a Jerusalem cross in the sample obtained in step S1 of this embodiment. That is, the honeycomb grid wall pattern structure of this embodiment is a Jerusalem cross. In this embodiment, node adhesive is applied between the rows of Jerusalem cross, and the distance between the node adhesive and the edge of the Jerusalem cross pattern is ≥1mm, as shown in Figure 6.

[0048] Please see Figure 7 In another embodiment of the present invention, the following is utilized: Figure 1 Schematic diagrams of different honeycomb cell wall patterns prepared by the method and steps described. Specific implementation methods and... Figure 1 The methods and steps are roughly the same, the only difference is that... Figure 1 The copper circuit pattern in the sample obtained by method step S1 is Figure 2The periodic open resonant ring shown is used in this embodiment. The copper circuit pattern in the sample obtained in step S1 is a double-ring structure (i.e., two nested square ring structures). That is, the honeycomb lattice wall pattern structure in this embodiment is a double-ring structure. In this embodiment, node adhesive is applied between the rows of the double-ring structure, and the distance between the node adhesive and the edge of the double-ring structure pattern is ≥1mm, as shown in Figure 7.

[0049] The embodiments of this invention adopt the approach of patterning first and then integrating the honeycomb, replacing the traditional post-etching method. At the same time, the laser direct writing method is used instead of the traditional spraying conductive ink method, which can effectively solve the technical problems such as unstable micro-patterns and poor bonding of honeycomb cell walls. It has the advantages of being easy to implement and having high conductivity reliability, and the honeycomb cell walls have the advantage of stable micro-structure patterns.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing metamaterial honeycomb, characterized in that, Includes the following steps: S1, copper circuit patterns are prepared on the PI film using laser maskless photolithography; S2, apply node adhesive to the relevant positions of the copper circuit pattern; S3, the bonding between the PI film and the adhesive layer of the applied node adhesive is achieved by stacking and hot pressing; S4, Curing the honeycomb panel formed by the node adhesive; S5, the honeycomb panel is stretched and shaped to form a honeycomb shape; S6, the stretched and shaped honeycomb is impregnated and cured with resin to obtain the metamaterial honeycomb.

2. The preparation method according to claim 1, characterized in that, In step S1, the laser wavelength used in the laser maskless lithography is 266–1550nm, the laser direct writing accuracy is 5–200μm, the laser power is 5–30W, the line width of the copper circuit pattern is 10–200μm, and the thickness is 5–20μm.

3. The preparation method according to claim 1, characterized in that, In step S2, the node adhesive is applied to the gaps in the copper circuit pattern using a screen printing machine. The squeegee angle of the screen printing machine is 45-60°, the pressure is 0.3-0.5MPa, and the speed is 10-100mm / s.

4. The preparation method according to claim 3, characterized in that, In step S2, after the application of the joint adhesive is completed, the joint is dried in a tunnel oven at a temperature of 80-150°C.

5. The preparation method according to claim 3, characterized in that, In step S2, the distance between the node adhesive and the copper circuit pattern is ≥1mm.

6. The preparation method according to claim 1, characterized in that, In step S3, the stacking hot pressing method includes alternating layers of node adhesive on the sample obtained in step S2, and then placing it in a hot press for hot pressing.

7. The preparation method according to claim 6, characterized in that, In step S3, the hot pressing temperature of the hot press is 100–200℃, the pressure is 0.5–2MPa, and the pressing time is 1–3h.

8. The preparation method according to claim 1, characterized in that, In step S4, the sample obtained in step S3 is cooled to room temperature for 1-6 hours to allow the node adhesive to cure and form the honeycomb panel.

9. The preparation method according to claim 1, characterized in that, In step S5, a servo-controlled stretching machine is used to stretch and shape the honeycomb panel formed in step S4. The stretching rate is 5-10 mm / min, the side length of the stretching holes is 1-8 mm, and the holding time is 6-8 h.

10. A metamaterial honeycomb, characterized in that, Prepared by the preparation method according to any one of claims 1 to 9.

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