Micro-through-hole structure polymer metallization method for guided wave transmission

Abstract

The invention discloses a micro-through-hole structure polymer metallization method for guided wave transmission, and belongs to the technical field of photoelectric device processing, a polymer substrate is used for replacing a traditional all-metal material, and the micro-through-hole structure polymer metallization method for guided wave transmission is achieved through the multi-stage processes of plasma activation, chemical coarsening, sensitization, chemical plating, electroplating and the like. And forming a compact and high-adhesion metal layer on the inner surface of the through hole of the polymer substrate. In the process, a microfluid pump or a peristaltic pump is adopted to drive the solution to circularly flow in the through hole and the microcavity. According to the micro-through-hole structure polymer metallization method for guided wave transmission, dynamic flowing of a chemical plating solution in a micro-through hole and an internal cavity is achieved by introducing a micro-fluid pump or a peristaltic pump, and therefore a uniform, compact and firmly-attached metal layer is obtained.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic device processing technology, and in particular to a polymer metallization method for micro-via structures used in waveguide transmission. Background Technology

[0002] With the development of 5G communication, millimeter-wave radar, terahertz imaging, and high-speed optical interconnects, the demand for electromagnetic wave transmission devices with fine microstructure features is increasing. Traditional electromagnetic wave transmission devices mainly include structures such as rectangular waveguides, resonant cavities, metal reflective cavities, filters, power dividers, and couplers. Their functions largely rely on the high conductivity of metal surfaces to achieve low-loss electromagnetic wave transmission, reflection, and confinement. Since the working mechanism of these devices is usually based on the electromagnetic field distribution and mode coupling principle under conductor boundary conditions, such devices have long been fabricated using monolithic metal structures.

[0003] Metallic materials such as copper, aluminum, and silver possess excellent electrical conductivity, thermal stability, and mechanical strength, maintaining stable electromagnetic performance under high power and wide frequency band conditions. They are the primary materials for traditional waveguides and optoelectronic packaging structures. However, with the expansion of millimeter-wave and terahertz frequency band applications, the internal structures of devices are becoming increasingly miniaturized and complex, often featuring high aspect ratio vias, complex internal cavities, periodic microstructures, and three-dimensional coupling channels. Traditional metal processing techniques (such as CNC milling, EDM, wire cutting, etching, and electroforming) suffer from significant processing difficulties and limitations in forming such complex structures.

[0004] Polymer-based materials, with their advantages of light weight, ease of processing, and low cost, are gradually becoming a novel functional substrate material in the microwave and optoelectronic fields. However, polymers themselves are insulators, requiring surface metallization to impart conductive properties. Existing metallization technologies mainly include vacuum sputtering, physical vapor deposition (PVD), chemical vapor deposition (CVD), and wet electroless plating. While vacuum sputtering and PVD can obtain dense, pure metal films, they are mainly suitable for open planes; in deep holes, closed channels, or semi-closed microcavities, they are prone to coating interruptions. CVD requires high-temperature reactions, making it unsuitable for polymer substrates with limited thermal stability. Electroless plating, with its low cost, strong adaptability, and ability to cover complex structures, exhibits unique advantages in electromagnetic waveguides, terahertz wave devices, and polymer microstructure metallization.

[0005] After the initial metal seed layer is formed by electroless plating, electroplating is required to form a dense and stable protective layer on its surface to prevent oxidation and failure of the electroless plating layer in air or humid and hot environments. Electroplating has important applications in electromagnetic wave transmission devices, optoelectronic packaging, and microwave conductor manufacturing. It can construct dense, continuous, and controllable thickness metal layers on substrate surfaces to meet the requirements of low loss, high conductivity, and high reflectivity for electromagnetic field transmission. However, in such high aspect ratio structures, traditional static electroless plating or electroplating methods are prone to uneven coating thickness distribution due to local ion concentration gradients and bubble retention. Therefore, it is particularly urgent to propose a controllable fluid-driven metallization preparation method to achieve uniform, dense, and firmly adhered coatings. Summary of the Invention

[0006] The purpose of this invention is to provide a polymer metallization method for micro-via structures used in guided wave transmission. By introducing a microfluidic pump or peristaltic pump, dynamic flow of chemical plating solution is achieved in the micro-vias and internal cavities, thereby obtaining a uniform, dense and firmly adhered metal layer.

[0007] To achieve the above objectives, the present invention provides a polymer metallization method for micro-via structures used in waveguide transmission, comprising the following steps: S1. Polymer materials are processed through polymer molding processes to obtain polymer substrates containing micro-sized through-holes or cavities. S2. The entire surface of the polymer substrate is subjected to plasma activation treatment with process gas, and cleaning agent is introduced using a peristaltic pump for cleaning. S3. After surface activation treatment and cleaning, the polymer substrate is immersed in a roughening solution for chemical roughening pretreatment, and a microfluidic pump drives the roughening solution to flow inside the polymer substrate. S4. After the chemical roughening pretreatment is completed, a peristaltic pump is used to introduce sensitizing solution to sensitize the inner surface of the polymer substrate. S5. After sensitization, a peristaltic pump is used to introduce a chemical plating solution to perform wet chemical silver plating on the inner surface of the polymer substrate. S6. After wet chemical silver plating is completed, the product is cleaned, dried, polished, and then electroplated with metal to obtain a polymer with metallized inner surface.

[0008] Preferably, in S1, the polymer material includes photosensitive resin, polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyimide, polyetheretherketone, polymethyl methacrylate, or polycarbonate, and the polymer molding process includes photopolymerization 3D printing, fused deposition modeling 3D printing, injection molding, or extrusion molding.

[0009] Preferably, in S2, the process gas includes one or two of oxygen, hydrogen, and nitrogen, the processing time is 10-30 min, the flow rate of the peristaltic pump is 0.1-5 mL / min, the circulation pressure of the peristaltic pump is 10-100 kPa, and the cleaning agent includes isopropanol and water, with the cleaning time for isopropanol and water each being 1-3 min independently.

[0010] Preferably, in step S3, the soaking time is 30-50 min, the roughening solution includes chromium oxide solution, phosphoric acid solution and sulfuric acid solution, the concentration of chromium oxide solution is 20-30 g / L, the concentration of phosphoric acid solution is 5-8 g / L, the concentration of sulfuric acid solution is 25-30 g / L, the flow rate of the microfluidic pump is 0.1-5 mL / min, and the circulation pressure of the microfluidic pump is 10-100 kPa.

[0011] Preferably, in S4, the flow rate of the peristaltic pump is 0.1-5 mL / min, the circulation pressure of the peristaltic pump is 10-100 kPa, the sensitization solution includes stannous chloride solution, and the sensitization time is 3-8 min.

[0012] Preferably, in S5, the flow rate of the peristaltic pump is 0.1-5 mL / min, the circulation pressure of the peristaltic pump is 10-100 kPa, the electroless plating solution includes glucose solution and silver ammonia solution, and the wet electroless silver plating time is 10-40 min.

[0013] Furthermore, the concentration of the glucose solution is 2-20 mmol / L, and the concentration of the silver ammonia solution is 10-30 mmol / L.

[0014] Preferably, in S6, the cathode for electroplating is the polymer substrate after wet chemical silver plating, the electrolyte for electroplating is a solution containing electroplating metal ions, including gold ions or palladium ions, and an external DC electric field is used to drive the metal ions to migrate to the cathode during the electroplating process.

[0015] The present invention also provides a metallized polymer, obtained by the above-described method for metallizing a micro-via structure polymer for waveguide transmission.

[0016] The present invention also provides an application of a metallized polymer, wherein the aforementioned metallized polymer is used in waveguide devices, resonant cavities, antenna arrays, filters, and microwave system packaging in the millimeter-wave, terahertz-wave, infrared, and visible light bands.

[0017] Therefore, the present invention employs the above-mentioned polymer metallization method for micro-via structures used in waveguide transmission, which has the following beneficial effects: (1) The present invention uses microfluidic pumps and peristaltic pumps to drive the solution to continuously circulate inside the microstructure through holes, avoiding the air barrier effect, so that the metal is evenly distributed on the entire surface, significantly improving the continuity and thickness uniformity of the metal layer, and is especially suitable for metallization of through holes with a depth-to-diameter ratio greater than 10, complex cavities and other structures.

[0018] (2) The present invention uses a polymer substrate to replace the traditional all-metal material to achieve the same electromagnetic waveguide or optical structure, significantly reducing the weight of the system; at the same time, relying on a variety of manufacturing processes, it can flexibly form complex geometry and large aspect ratio micro-hole structures, breaking through the shape constraints and cost bottlenecks of metal CNC machining, and has high structural designability and easy processing.

[0019] (3) The present invention significantly enhances the surface energy and chemical activity of polymer through multi-step surface pretreatment such as plasma activation, chemical roughening and sensitization. The micro-nano pits formed by roughening provide mechanical interlocking interfaces, and the metal ion nucleation centers formed by sensitization make the large-area metal layer formed by chemical plating tightly bonded to the polymer substrate. Even under extreme temperature cycling conditions, it can still maintain the stability of structural size and transport performance.

[0020] (4) This invention is applicable to a variety of polymers, such as photosensitive resin, polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), polyimide (PI), polyether ether ketone (PEEK), polymethyl methacrylate (PMMA) or polycarbonate (PC), etc. High-adhesion metal layer can be obtained by this method. The entire processing is carried out under normal temperature and pressure, avoiding polymer structure deformation, and has strong applicability.

[0021] (5) The present invention adopts a modular fluid control system and a standardized reaction liquid formula, which can realize multi-channel parallel operation and is suitable for mass production.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the external dimensions of the horn antenna prepared according to Embodiment 1 of the present invention; Figure 2 This is a flowchart of a polymer metallization method for a micro-via structure used in waveguide transmission according to the present invention; Figure 3 This is a physical image of the horn antenna prepared according to Embodiment 1 of the present invention; Figure 4 The test result shows the dimensional deviation of the rear end face of the horn antenna prepared in Embodiment 1 of this invention. Figure 5 These are partial cross-sectional views and surface roughness test images of the horn antenna prepared in Embodiment 1 of the present invention.

[0024] Figure 6 This is the 140GHz gain pattern of the horn antenna prepared in Embodiment 1 of the present invention and the device prepared by metal cutting. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0027] In this invention, the photosensitive resin was purchased from Shenzhen Creality 3D Technology Co., Ltd., and other experimental materials and instruments are all conventional experimental materials in the field and can be purchased through commercial channels.

[0028] Example 1 Taking a horn antenna as an example, its shape is as follows: Figure 1 As shown, it includes a rectangular waveguide with a length of 3 mm, a transition section from rectangle to circle with a length of 3.3 mm, a circular waveguide with a radius of 2 mm, and a tapered horn section with an axial length of 35 mm and an aperture diameter of 12.7 mm. The main mode of this horn antenna operates at frequencies of 110 Hz to 170 GHz.

[0029] The inner surface metallization process of the horn antenna is as follows: Figure 2 As shown, it includes the following steps: S1. Using photopolymerization 3D printing technology, photosensitive resin is cured layer by layer, and after cleaning and removal of support, the resin substrate of the horn antenna is obtained. S2. The entire surface of the resin substrate of the horn antenna is subjected to plasma activation treatment with nitrogen and hydrogen for 20 min. Isopropanol and deionized water are then sequentially introduced through a peristaltic pump for cleaning, with cleaning time of 2 min for each. The flow rate of the peristaltic pump is 2 mL / min and the circulation pressure of the peristaltic pump is 50 kPa. S3. After the surface activation treatment is completed, the resin substrate of the horn antenna is immersed in a roughening solution composed of 25 g / L chromium oxide solution, 6 g / L phosphoric acid solution and 28 g / L sulfuric acid solution for chemical roughening pretreatment for 40 min. The roughening solution is driven by a microfluidic pump to flow inside the polymer substrate. The flow rate of the microfluidic pump is 2.5 mL / min and the circulation pressure of the microfluidic pump is 50 kPa. S4. After the chemical roughening pretreatment is completed, the inner surface of the resin substrate of the horn antenna is sensitized for 5 min by passing stannous chloride solution through a peristaltic pump. The flow rate of the peristaltic pump is 2.5 mL / min and the circulation pressure of the peristaltic pump is 40 kPa. Then, it is rinsed with deionized water for 10 min. S5. After sensitization, under light-protected conditions, a peristaltic pump was used to pass 10 mmol / L glucose solution and 20 mmol / L silver ammonia solution to perform wet chemical silver plating on the inner surface of the resin substrate of the horn antenna. The chemical silver plating time was 25 min, during which the flow rate of the peristaltic pump was 0.5 mL / min and the circulation pressure of the peristaltic pump was 60 kPa. S6. After wet chemical silver plating is completed, deionized water is circulated into the resin substrate of the horn antenna using a peristaltic pump for cleaning for 10 minutes. Then, dry air is blown into the resin substrate of the horn antenna for drying for 12 hours. The silver plating layer is then polished and placed in an electrolyte containing gold ions for electroplating. An external DC electric field drives the gold ions in the electrolyte to migrate to the cathode and undergo an electrochemical reduction reaction on its surface, depositing layer by layer to form a uniform and continuous protective layer, thus obtaining a horn antenna with a metallized inner surface of the resin substrate.

[0030] The actual horn antenna with metallized inner surface of resin substrate prepared in Example 1 is shown below. Figure 3 As shown.

[0031] To accurately evaluate the temperature tolerance of the resin-substrate metallized inner surface horn antenna prepared in Example 1, a temperature cycling test was conducted: extreme environments of -50°C (LT) and 150°C (HT) were set, with each temperature cycle lasting 12 hours. Key dimensions of the horn antenna end face were precisely measured before and after the temperature cycling test. The results are as follows: Figure 4 As shown, the surface roughness of the horn antenna was tested using an atomic force microscope based on its cross-sectional view, and the results are as follows. Figure 5 As shown.

[0032] from Figure 4 As can be seen, the dimensional deviation of the end face caused by thermal expansion is strictly controlled within 0.05 mm; from Figure 5 As can be seen, the antenna metal coating uniformly covers the inner surface of the resin substrate, without any localized excessive thickness, gaps, or peeling. The coating thickness deviation is controlled within 5% of the design value, fully demonstrating the coating uniformity and dimensional accuracy. Meanwhile, surface roughness tests show that the arithmetic mean deviation (Ra) of the metallized surface profile is less than 0.1 μm, exhibiting extremely low surface roughness. This indicates that the fabricated device not only possesses excellent temperature adaptability but also maintains structural dimensional stability, excellent coating uniformity, precise dimensional control, and a low-roughness surface under extreme temperature cycling conditions.

[0033] To evaluate the radiation performance of the resin-based metallized inner surface horn antenna prepared in Example 1, radiation pattern tests were performed. In a microwave anechoic chamber, the far-field radiation patterns of both the physical metal substrate (Meas Metal) and the resin-based metallized inner surface horn antenna prepared in Example 1 (Meas Resin) were measured. The radiation characteristics were recorded within an angle range of 0°–90°, using normalized amplitude (dB) as the indicator. The results are as follows: Figure 6 As shown. From Figure 6 It can be seen that the measured radiation pattern of the device prepared by this method is highly consistent with the simulation results (Sim) and the actual metal substrate, indicating that its radiation performance is consistent with the theoretical expectation. At the same time, the experimental test verifies that the device has excellent radio frequency performance: the insertion loss is less than 0.6dB, the return loss is greater than 30dB, and the overall performance meets the design target.

[0034] Therefore, the present invention employs the above-mentioned polymer metallization method for micro-hole structure used for waveguide transmission, and by introducing a microfluidic pump or peristaltic pump, realizes the dynamic flow of chemical plating solution in the micro-hole and internal cavity, thereby obtaining a uniform, dense and firmly adhered metal layer.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for polymer metallization of micro-via structures for waveguide transmission, characterized in that: Includes the following steps: S1. Polymer materials are processed through polymer molding processes to obtain polymer substrates containing micro-sized through-holes or cavities. S2. The entire surface of the polymer substrate is subjected to plasma activation treatment with process gas, and cleaning agent is introduced using a peristaltic pump for cleaning. S3. After surface activation treatment and cleaning, the polymer substrate is immersed in a roughening solution for chemical roughening pretreatment, and a microfluidic pump drives the roughening solution to flow inside the polymer substrate. S4. After the chemical roughening pretreatment is completed, a peristaltic pump is used to introduce sensitizing solution to sensitize the inner surface of the polymer substrate. S5. After sensitization, a peristaltic pump is used to introduce a chemical plating solution to perform wet chemical silver plating on the inner surface of the polymer substrate. S6. After wet chemical silver plating is completed, the product is cleaned, dried, polished, and then electroplated with metal to obtain a polymer with metallized inner surface.

2. The polymer metallization method for micro-via structures used for waveguide transmission according to claim 1, characterized in that: In S1, the polymer materials include photosensitive resin, polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyimide, polyetheretherketone, polymethyl methacrylate or polycarbonate, and the polymer molding process includes photopolymerization 3D printing, fused deposition modeling 3D printing, injection molding or extrusion molding.

3. The polymer metallization method for micro-via structures used for waveguide transmission according to claim 1, characterized in that: In S2, the process gas includes one or two of oxygen, hydrogen, and nitrogen. The processing time is 10-30 min. The flow rate of the peristaltic pump is 0.1-5 mL / min. The circulation pressure of the peristaltic pump is 10-100 kPa. The cleaning agents include isopropanol and water. The cleaning time with isopropanol and water is 1-3 min each.

4. The polymer metallization method for micro-via structures used for waveguide transmission according to claim 1, characterized in that: In S3, the soaking time is 30-50 min. The roughening solution includes chromium oxide solution, phosphoric acid solution and sulfuric acid solution. The concentration of chromium oxide solution is 20-30 g / L, the concentration of phosphoric acid solution is 5-8 g / L, the concentration of sulfuric acid solution is 25-30 g / L, the flow rate of microfluidic pump is 0.1-5 mL / min, and the circulation pressure of microfluidic pump is 10-100 kPa.

5. The polymer metallization method for micro-via structures used in waveguide transmission according to claim 1, characterized in that: In S4, the flow rate of the peristaltic pump is 0.1-5 mL / min, the circulation pressure of the peristaltic pump is 10-100 kPa, the sensitization solution includes stannous chloride solution, and the sensitization time is 3-8 min.

6. The polymer metallization method for micro-via structures used in waveguide transmission according to claim 1, characterized in that: In S5, the flow rate of the peristaltic pump is 0.1-5 mL / min, the circulation pressure of the peristaltic pump is 10-100 kPa, the electroless plating solution includes glucose solution and silver ammonia solution, and the wet electroless silver plating time is 10-40 min.

7. The polymer metallization method for micro-via structures used for waveguide transmission according to claim 6, characterized in that: The concentration of glucose solution is 2-20 mmol / L, and the concentration of silver ammonia solution is 10-30 mmol / L.

8. The polymer metallization method for micro-via structures used in waveguide transmission according to claim 1, characterized in that: In S6, the cathode for electroplating is the polymer substrate after wet chemical silver plating, and the electrolyte for electroplating is a solution containing electroplating metal ions, including gold ions or palladium ions. During the electroplating process, an external DC electric field is used to drive the metal ions to migrate to the cathode.

9. A metallized polymer, characterized in that: It is obtained by polymer metallization method for micro-via structure used for waveguide transmission as described in any one of claims 1-8.

10. The metallized polymer of claim 9 or the metallized polymer obtained by the metallization method of the micro-via structure polymer for waveguide transmission according to any one of claims 1-8 is used for waveguide devices, resonant cavities, antenna arrays, filters and microwave system packaging in the millimeter wave, terahertz wave, infrared and visible light bands.

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