A method for processing a radio frequency micro coaxial device based on a 3D printing and MEMS hybrid process

Abstract

The application discloses a kind of processing methods of radio frequency micro coaxial device based on 3D printing and MEMS hybrid process, belong to the technical field of micro-nano machining.The method comprises: the mixed processing flow of the metal radio frequency transmission line at the micro coaxial axis, the integrated processing flow of the radio frequency micro coaxial device organic skeleton, the flow of the radio frequency micro coaxial device organic skeleton and metal radio frequency transmission line joint assembly;The application can greatly reduce the cost by reasonably selecting 3D printing process and MEMS process, in addition, the integrated forming advantage of 3D printing can reduce the error caused by lamination, and improve the performance of radio frequency device.

Description

Technical Field

[0001] This invention relates to the field of radio frequency device manufacturing, and in particular to a manufacturing technology for micro-coaxial structure radio frequency devices applied in the high-frequency W-band and terahertz band. Specifically, it discloses a method for processing radio frequency micro-coaxial devices based on a hybrid process of 3D printing and MEMS, which belongs to the technical field of micro-nano processing. Background Technology

[0002] Three-dimensional metallic microcoaxial structures are the most promising structures for realizing terahertz band devices. These structures not only have extremely low electromagnetic losses, but the metallic casing also reduces stray signal interference. However, the fabrication of these three-dimensional metallic microcoaxial structures is very expensive. Because of their three-dimensional configuration, traditional MEMS processes require disassembling them into multiple planar structures for fabrication, and then stacking them layer by layer to achieve the overall three-dimensional structure. This not only results in enormous fabrication costs, but also means that alignment and error perturbations between layers can significantly affect the final electromagnetic performance of the device. On the other hand, metal transmission lines are typically manufactured using traditional MEMS electroplating processes. These processes utilize photolithography to create an electroplating mold, which is then filled with electroplating material. Finally, the mold is removed—the sacrificial layer—to achieve the metal transmission line fabrication, resulting in material waste. Traditional MEMS processes can no longer meet the manufacturing requirements of three-dimensional metallic microcoaxial structures.

[0003] 3D printing has the capability to create complex 3D structures in a single, integrated manner, significantly reducing processing costs. However, 3D printing also has limitations, namely the limitations of the printing materials and the processing precision. Current 3D printing technology can only print non-conductive materials; furthermore, while it can create single transmission lines without positioning requirements, it cannot meet the alignment requirements in the manufacturing process of cross-coupled radio frequency transmission lines. Therefore, it is impossible to manufacture conductive structures with three-dimensional metallic micro-coaxial structures using 3D printing technology.

[0004] In order to overcome the inherent defects of traditional MEMS processes and break through the material limitations and low precision bottlenecks of 3D printing, this invention aims to propose a process for processing radio frequency micro coaxial devices based on a hybrid 3D printing and MEMS process. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the aforementioned background technology by providing a low-cost, simple, and easy-to-implement method for fabricating radio frequency micro-coaxial devices. This method aims to fabricate three-dimensional metal micro-coaxial structure devices with excellent radio frequency performance, thereby solving the technical problems of high cost and material consumption in traditional MEMS processes for manufacturing three-dimensional metal micro-coaxial structure devices, as well as the inability of 3D printing technology to directly print three-dimensional metal micro-coaxial structure devices.

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution: A method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process includes the following steps: Step 1, Hybrid processing flow of metal RF transmission line at the micro-coaxial axis: 3D printing technology is used to integrally form the organic skeleton of the RF micro-coaxial device, which includes a metal ground shell and an organic support structure. Metal layers are electroplated on the inner and outer surfaces of the metal ground shell. The organic support structure is fixed on the inner side of the metal ground shell. The organic support structure is used to support the metal RF transmission line located at the micro-coaxial axis. Step 2, Integrated fabrication process of organic framework for radio frequency micro coaxial device: Use 3D printing technology to print metal radio frequency transmission line organic framework, electroplat a metal layer on the surface of metal radio frequency transmission line organic framework to prepare metal radio frequency transmission line; Step 3, the process of joining and assembling the organic framework of the RF micro-coaxial device with the metal RF transmission line: joining and assembling the organic framework of the RF micro-coaxial device and the metal RF transmission line.

[0007] As a further optimization of the RF micro-coaxial device fabrication method based on 3D printing and MEMS hybrid process, step 1 utilizes 3D printing technology to integrally form the RF micro-coaxial device organic skeleton, which includes two symmetrically arranged first semi-enclosed structures and second semi-enclosed structures along the axis. The first semi-enclosed structure includes a first part of a metal ground shell and a first part of an organic support structure fixed inside the first part of the metal ground shell. The second semi-enclosed structure includes a second part of a metal ground shell and a second part of an organic support structure fixed inside the second part of the metal ground shell.

[0008] As a further optimization of the RF micro-coaxial device processing method based on 3D printing and MEMS hybrid technology, the specific method of electroplating metal layers on the inner and outer surfaces of the metal grounding shell in step 1 is as follows: First, the first part and the second part of the organic support structure are covered, and a seed layer is applied to the surface of the first semi-closed structure and the second semi-closed structure. Adhesive layers are grown only on the inner and outer surfaces of the first part and the second part of the metal grounding shell; then, electroplating is performed on the surface of the first part and the second part of the metal grounding shell where the adhesive layers are grown.

[0009] As a further optimization of the RF micro-coaxial device fabrication method based on 3D printing and MEMS hybrid technology, the specific method of step 3 for joining and assembling the RF micro-coaxial device with the organic skeleton and the metal RF transmission line is as follows: First, the metal RF transmission line is bonded to the support structure by heating and pressurizing; then, the first semi-enclosed structure and the second semi-enclosed structure are bonded by heating and pressurizing.

[0010] As a further optimization of the RF micro-coaxial device fabrication method based on 3D printing and MEMS hybrid technology, in step 1, when using 3D printing technology to integrally form the organic skeleton of the RF micro-coaxial device, including a metal grounding shell and an organic support structure, a hole is left on the metal grounding shell along the axial direction, with a hole width W. 孔洞 Width W of micro coaxial metal grounding housing 外导体 Satisfy: W 孔洞 <0.1×W 外导体 W 外导体 The value range is 15μm ~ 25μm, W 孔洞 The value range is 1.5μm ~ 2.5μm.

[0011] As a further optimization of the RF micro-coaxial device processing method based on 3D printing and MEMS hybrid technology, in step 1, the organic skeleton of the RF micro-coaxial device integrally formed by 3D printing technology has the same height B1_H and width B1_W for the metal ground shell, and B1_W=B1_H=15 mm ~25μm. The length B1_L of the metal ground shell is in the range of B1_L=11 mm ~12 mm.

[0012] As a further optimization of the RF micro-coaxial device fabrication method based on 3D printing and MEMS hybrid technology, the specific method of electroplating a metal layer on the surface of the metal RF transmission line organic framework in step 2 is as follows: a seed layer is coated on the surface of the metal RF transmission line organic framework, and an adhesion layer is grown on the surface of the metal RF transmission line organic framework.

[0013] As a further optimization of the RF micro-coaxial device processing method based on 3D printing and MEMS hybrid technology, step 1 uses organic materials to 3D print the organic skeleton of the RF micro-coaxial device, and step 2 uses organic materials to 3D print the organic skeleton of the metal RF transmission line. The organic materials include, but are not limited to, ABS, titanium alloy, chromium alloy, stainless steel, and aluminum.

[0014] As a further optimization of the RF micro-coaxial device fabrication method based on 3D printing and MEMS hybrid technology, both the first part and the second part of the organic support structure include: an organic insulating support structure that provides support in the vertical direction and an organic insulating support structure that provides support in the horizontal direction. The height Z1 of the organic insulating support structure that provides support in the vertical direction is 0.5×B1_H, and the height Z2 of the organic insulating support structure that provides support in the horizontal direction is 0.35×B1_H.

[0015] The radio frequency coaxial device manufactured according to the above processing method includes: a metal ground housing, an organic support structure, and a metal radio frequency transmission line located at the axis of the micro-coaxial structure. The organic support structure is fixed inside the metal ground housing, the metal radio frequency transmission line is bonded to the organic support structure, and the metal radio frequency transmission line is suspended in the resonant air cavity covered by the metal ground housing.

[0016] The present invention, by adopting the above technical solution, has the following beneficial effects: (1) The processing method proposed in this invention combines the high precision advantage of MEMS processing with the low cost and integrated advantages of 3D printing. First, the organic skeleton of the radio frequency micro coaxial device, including the support structure and the metal ground shell, is integrally formed by organic material 3D technology. The 3D printed metal ground shell is used as a mold for chemical treatment and MEMS electroplating to achieve local metallization of the organic skeleton of the radio frequency micro coaxial device made of insulating material, avoiding the material consumption of traditional MEMS electroplating process and reducing the error introduced by the stacking of traditional MEMS process. Then, a non-metallic metal radio frequency transmission line organic skeleton is printed by 3D technology. Chemical treatment and MEMS electroplating are carried out on the basis of the metal radio frequency transmission line organic skeleton to achieve full metallization of the metal radio frequency transmission line organic skeleton made of insulating material. Finally, the organic skeleton of the radio frequency micro coaxial device is joined with the metal radio frequency transmission line, which can meet the alignment requirements of at least two rows of cross-arranged mutually coupled radio frequency transmission lines near the axis, avoiding the complex process of multi-layer stacking in traditional MEMS process.

[0017] (2) The processing method proposed in this invention involves splitting the organic skeleton of the radio frequency micro coaxial device along the longitudinal direction, disassembling the entire organic skeleton for electroplating, and then splicing the entire organic skeleton through simple bonding processes such as bonding, thereby reducing the processing difficulty and cost, and improving the success rate of device fabrication.

[0018] (3) The radio frequency micro coaxial device made by the processing method proposed in this invention has greatly reduced radio frequency loss and reduced electromagnetic loss of metal radio frequency transmission lines by forming a metal grounding shell and support structure in one piece through 3D process, thereby improving the performance of radio frequency devices. Attached Figure Description

[0019] To better describe and illustrate embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the currently described embodiments and / or examples, or the best mode of these inventions as currently understood.

[0020] Figure 1 This is a schematic diagram of the fabrication process for micro-coaxial devices based on traditional MEMS technology.

[0021] Figure 2This is a schematic diagram of the fabrication process of radio frequency micro-coaxial devices based on the 3D printing-MEMS hybrid process of this invention.

[0022] Figure 3 This is a three-dimensional perspective view of a radio frequency microcoaxial device fabricated using the processing method of this invention.

[0023] Figure 4(a) is a key dimension annotation diagram of the radio frequency micro coaxial device fabricated using the processing method of the present invention, and Figure 4(b) is a cross-sectional view of the radio frequency micro coaxial device fabricated using the processing method of the present invention.

[0024] Figure 5(a) shows the specific process flow of the organic framework fabrication technology of the radio frequency micro coaxial device proposed in this invention, and Figure 5(b) is a schematic diagram of dividing the organic framework into two semi-closed structures along the axial direction of the micro coaxial device.

[0025] Figure 6 This is a flowchart illustrating the specific fabrication process of the metal radio frequency transmission line structure for the radio frequency micro coaxial device proposed in this invention.

[0026] Figure 7 This is a flowchart illustrating the specific process of joining and assembling the radio frequency micro coaxial device structure proposed in this invention.

[0027] Figure 8 This diagram illustrates a comparison between the fabrication methods of micro-coaxial devices based on 3D printing-MEMS hybrid technology and those based on traditional MEMS technology in terms of cost and fabrication complexity.

[0028] The following are the labels in the diagram: 1. Organic support structure; 1-1. First part of organic support structure; 1-2. Second part of organic support structure; 2. Hole; 3. Metal grounding shell; 3-1. First part of metal grounding shell; 3-2. Second part of metal grounding shell; 4. Metal radio frequency transmission line; 5. Organic framework of radio frequency micro-coaxial device; 6. Organic framework of radio frequency micro-coaxial device with grown adhesive layer material; 7. Organic framework of radio frequency micro-coaxial device with localized metallization; 8. Organic framework of metal radio frequency transmission line; 9. Organic framework of metal radio frequency transmission line with grown adhesive layer material; 10. Organic framework of metal radio frequency transmission line with metallization; 11. Metal thin layer; 12. Radio frequency micro-coaxial device. Implementation

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0030] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by those skilled in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] It should be understood that when a component or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other components or layers, it may be directly on, adjacent to, connected to, or coupled to other components or layers, or there may be intervening components or layers. Conversely, when a component is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other components or layers, there are no intervening components or layers. The term "connection" in this specification, if referring to the transmission of electrical signals or data between connected circuits, modules, units, etc., should be understood as "electrical connection," "communication connection," etc. It should be understood that although terms such as first, second, third, etc., may be used to describe various components, parts, areas, layers, and / or portions, these components, parts, areas, layers, and / or portions should not be limited by these terms; these terms are merely used to distinguish one component, part, area, layer, or portion from another component, part, area, layer, or portion. Therefore, without departing from the teachings of this invention, the first element, component, region, layer or portion discussed below may be represented as a second element, component, region, layer or portion.

[0032] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then when described as “below” or “under” or “below” other elements, the element or feature will be oriented “above” other elements or features. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may also be oriented, for example, rotated 90 degrees, and the spatial descriptive terms used herein are accordingly interpreted as representing the spatial orientation.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will be understood that “at least one” means one or more, and “a plurality” means two or more. “At least a portion of an element” means part or all of an element. It should also be understood that when the terms “comprise” and / or “comprising” are used in this specification, the presence of the stated features, integers, steps, operations, elements, and / or components is confirmed, but the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups is not excluded. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0034] Embodiments of the invention are described herein with reference to cross-sectional views, which are schematic diagrams of preferred embodiments of the invention. Thus, variations in the illustrated shape can be expected due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the invention should not be limited to the specific shapes of the areas shown herein, but include shape deviations due to, for example, manufacturing processes. For example, an electroplated metal layer shown as a rectangular thin layer would not actually form a smooth, flat metal layer; rather, it would have a certain roughness and would exhibit bumps and depressions due to uneven current intensity and electrolyte composition during electroplating. Therefore, the areas shown in the figures are substantially schematic, and their shapes are not intended to show the actual shapes of the areas of the device and are not intended to limit the scope of the invention.

[0035] Figure 1 The fabrication method shown is based on traditional MEMS technology for micro-coaxial devices. It involves layering the three-dimensional coaxial structure into many planar structures, which are then stacked to form a final 3D radio frequency (RF) structure. The most significant drawback of this traditional method is its high cost. Each layer requires expensive processing, and a single device requires at least ten repeated processing steps. For more complex three-dimensional coaxial structures, the number of layers increases, further escalating the cost. Furthermore, the alignment and stacking precision between layers significantly reduce the performance of the RF device. A problem in one layer can cause the entire structure to fail. This method is also resource-intensive and costly. The processing difficulty of this traditional MEMS method increases with complexity. In contrast, 3D printing always produces a single, integrated structure, and the cost remains roughly the same regardless of whether the structure is simple or complex.

[0036] This invention proposes a method for fabricating radio frequency microcoaxial devices based on a 3D printing-MEMS hybrid process. Leveraging the advantages of 3D printing's integrated molding, the basic framework of a metal microcoaxial device is integrally printed using organic materials such as ABS, titanium alloy, chromium alloy, stainless steel, and aluminum powders. Then, surface treatments using MEMS processes, such as chemical processing, electroplating, and vacuum plating, are performed to impart conductivity to the organic insulating framework. Although the structure formed by metal powder printing is already metallic, its conductivity is far lower than that of conventional metals. Therefore, it is necessary to add a coating process to metallize the framework and improve conductivity. This fabrication method avoids complex multi-layered structures while combining the high precision advantages of MEMS fabrication with the low cost and integrated advantages of 3D printing. Compared to… Figure 1 The micro-coaxial device fabrication method shown is based on traditional MEMS technology. The fabrication method of the present invention is easier to implement and has extremely low cost. It can reduce the error caused by stacking, improve the yield of wafer fabrication, and enhance the performance of RF devices.

[0037] Figure 2The diagram illustrates the 3D printing-MEMS hybrid process for fabricating radio frequency (RF) microcoaxial devices according to the present invention. It includes: a hybrid fabrication process for the metal RF transmission line at the microcoaxial axis; an integrated fabrication process for the RF microcoaxial device's organic framework; and a process for assembling the RF microcoaxial device's organic framework and the metal RF transmission line. The integrated fabrication process for the RF microcoaxial device's organic framework is shown in Figure 5(a). This requires the simultaneous fabrication of both the metal grounding shell structure and the support structure, including the fabrication of the RF microcoaxial device's organic framework and its metallization. The fabrication of the RF microcoaxial device's organic framework 5 involves 3D printing using a high-precision SLA process. Simultaneously, the organic support structure 1, fixed to the inner wall of the metal grounding shell, is also integrally printed. Both components are organic materials and are non-conductive. Unlike the complete electroplating of the metal transmission line at the core of a micro-coaxial device, the metallization process of the organic framework of an RF micro-coaxial device is partial metallization. This involves electroplating only the portion of the structure excluding the organic support structure, because the support structure of the coaxial transmission line must be an insulating material; otherwise, the current would be short-circuited by the support structure. This partial metallization is achieved through a combination of chemical treatment and selective electroplating. Chemical treatment of the surface of the organic framework of the RF micro-coaxial device improves surface smoothness, reduces surface roughness, and increases the adhesion layer to enhance the adhesion of subsequent electroplating processes. Specifically, after covering the organic support structure 1, a seed layer is applied to the surface of the RF organic framework 5. This prevents the growth of the adhesion layer material on the surface of the organic support structure 1, allowing the adhesion layer to grow only on the inner and outer sides of the metal grounding shell. The organic support structure 1 retains the non-conductive properties of organic matter, resulting in the RF micro-coaxial device organic framework 6 with the grown adhesion layer material, thus preventing metallization in subsequent electroplating processes. Selective electroplating processes the organic framework 6 of the RF micro-coaxial device, which grows the adhesive layer material, to achieve metallization of the metal grounding shell. A 6μm thick copper metal layer is applied to the surface of the metal grounding shell, while the visible support structure retains its non-metallized characteristics, resulting in a locally metallized RF micro-coaxial device organic framework 7. In the case of high-frequency electromagnetic wave transmission, this 6μm thick copper metal layer is sufficient for electromagnetic wave transmission. Simultaneously, the metal layer formed by selective electroplating also has an adhesive effect. During subsequent assembly, heating and pressurization can increase the fluidity of the metal, facilitating better assembly and splicing.

[0038] To facilitate selective electroplating of the organic framework, as shown in Figures 5(a) and 5(b), the present invention longitudinally cuts the organic framework along its central symmetry plane, dividing it into two semi-enclosed structures: a first organic framework part and a second organic framework part. The first organic framework part includes a first metal ground shell part 3-1 and a first organic support structure part 1-1 supporting one RF transmission line. The second organic framework part includes a second metal ground shell part 3-2 and a second organic support structure part 1-2 supporting another RF transmission line. This not only reduces the difficulty of the electroplating process but also does not affect the electromagnetic characteristics of the RF microcoaxial device.

[0039] like Figure 6 As shown, the hybrid processing flow of the metal RF transmission line at the core of the micro-coaxial cable includes the following operations: A metal RF transmission line organic framework 8 is printed using 3D printing technology. Since this structure is not metal, it cannot transmit current, so a further metallization process is required. Before the metallization process, the surface of the metal RF transmission line organic framework needs to be treated (8) to reduce surface roughness and improve metal ion adhesion. Specifically, a seed layer is coated on the surface of the metal RF transmission line organic framework 8 through a chemical treatment process to obtain a metal RF transmission line organic framework 9 with a growth adhesive layer material. Electroplating is then performed on the surface of the metal RF transmission line organic framework 9 with the growth adhesive layer material to obtain a metallized metal RF transmission line organic framework 10. It can be seen that all surfaces of the metal RF transmission line organic framework are covered with a thin layer of metal.

[0040] While this invention also employs electroplating to process the metal radio frequency transmission line at the core of a micro-coaxial cable, it differs from traditional MEMS electroplating processes in that it uses an electroplating mold. Traditional MEMS electroplating processes utilize photolithography to create the mold, then fill the mold with electroplating, and finally remove the mold (sacrificial layer) using a developing solution to achieve the metal transmission line processing. This wastes materials and generates waste liquid that pollutes the environment. This invention eliminates the need for photolithography, directly using 3D printing to integrally print the transmission line, reducing material consumption. However, 3D printing can only print non-conductive materials. Therefore, in this invention, the 3D-printed organic structure is placed in an electroplating stage, and the electroplating process is performed using the organic structure as a framework. This results in the printed metal radio frequency transmission line having an organic skeleton encased in a layer of metal, thus achieving the processing of the metal radio frequency transmission line. Although this metal radio frequency transmission line is only encased in a thin metal layer, under high-frequency conditions, due to the skin effect of current, this thin metal layer is sufficient to perform current transmission.

[0041] After the inner micro-coaxial core metal RF transmission line, outer metal grounding shell, and organic support structure are all printed and metallized, the bonding and assembly process begins. For example... Figure 7As shown, the assembly process of the RF microcoaxial device with its organic framework and metal RF transmission lines includes two assembly steps. The first assembly step involves assembling the metal RF transmission line 4 at the microcoaxial axis with the insulated organic support structure 1. The metal RF transmission line 4 is heated to make its surface metal fluid. Then, the metal RF transmission line 4 is placed on the organic support structure 1 and pressure is applied for bonding. After cooling, the bonding is achieved, and the two can be bonded together on a bonding machine. The second assembly step involves joining two semi-closed structures longitudinally cut along the axially symmetric plane. Due to the presence of a thin metal layer 11 at the joint contact point, the bonding is also achieved through hot pressing followed by cooling, resulting in the RF microcoaxial device 12 formed after hot pressing and cooling. This method inevitably generates heat, causing some metal loss. Furthermore, it requires selecting organic materials with extremely high melting points and low thermoplasticity to create an organic framework that is thermoplastic and can withstand extremely high temperatures, ensuring that the 3D-printed structure does not deform during the bonding process.

[0042] The final three-dimensional perspective view of the fabricated RF microcoaxial device is as follows: Figure 3 As shown, the RF microcoaxial device includes: a metal RF transmission line 4 located at the center of the microcoaxial axis, an organic support structure 1, a metal grounding shell 3, holes 2 for facilitating the electroplating of the inner surface, and a resonant air cavity. The resonant air cavity is the portion enclosed by the metal grounding shell, and both the metal RF transmission line and the organic support structure are located within this cavity. The organic support structure is made of insulating organic material, and its function is to support the metal RF transmission line, allowing it to be suspended within the resonant air cavity enclosed by the metal grounding shell. The metal RF transmission line is responsible for transmitting RF signals. This structure, suspended within the resonant air cavity and supported by a support structure made of organic non-conductive material, prevents the metal RF transmission line from contacting other materials, significantly reducing RF loss. Therefore, the metal RF transmission line suspended within the resonant air cavity exhibits low electromagnetic loss, and the shielding effect of the metal grounding shell also reduces interference from external electromagnetic signals to the internal RF transmission line.

[0043] In an embodiment of the present invention, the 3D-printed micro-coaxial device metal outer conductor, i.e. the grounding shell covering the radio frequency transmission line, has a height B1_H and a width B1_W that are equal, with B1_W=B1_H=15~25μm, and a metal outer conductor length B1_L=11~12mm.

[0044] In an embodiment of the present invention, a series of holes 2 need to be made on the metal grounding shell 3 along the radio frequency signal transmission direction, i.e., the axial direction, so that metal can be electroplated on the surface of the inner skeleton. These holes can be pre-reserved while 3D printing the organic skeleton of the radio frequency micro-coaxial device. In this invention, to ensure that the holes do not affect the electromagnetic field propagation characteristics, their size must be small enough, with a hole width W.孔洞 and W 外导体 The width ratio of the micro-coaxial metal grounding enclosure must satisfy the following relationship: W 孔洞 <0.1×W 外导体 In this invention, the metal grounded outer casing W 外导体 The width range is 15~25μm, so the width W of the hole is... 孔洞 The range is 1.5~2.5μm. The hole is pre-drilled during the 3D printing process, so there is no need to etch the hole after printing.

[0045] In an embodiment of the present invention, the specific dimensions of the radio frequency microcoaxial device fabricated by the present invention are marked as shown in Figure 4(a). Based on the simulation results of the dimensions and performance of the microcoaxial device in previous work, the length of the metal radio frequency transmission line is determined. l i The distance between the two transmission lines d ij The length of the overlapping coupling section of the two transmission lines p i These are all parameters that affect the performance of micro-coaxial RF devices. To ensure the performance of RF coaxial devices, these parameters must meet the ranges shown in Table 1: B1_L 11~12mm <![CDATA[ l 6 ]]> 1.96~2.04 <![CDATA[ p 1 ]]> 0.375~0.425 <![CDATA[ l 1 ]]> 1.96~2.04 <![CDATA[ d 15 ]]> 0.03~0.05 <![CDATA[ p 2 ]]> 0.375~0.425 <![CDATA[ l 2 ]]> 1.96~2.04 <![CDATA[ d 26 ]]> 0.09~0.11 <![CDATA[ p 3 ]]> 0.375~0.425 <![CDATA[ l 5 ]]> 1.96~2.04 <![CDATA[ d 37 ]]> 0.07~0.09 In an embodiment of the present invention, as shown in Figure 4(b), the support structure is divided into a longitudinal support structure and a transverse support structure. The height Z1 of the organic insulating support structure supporting in the vertical direction is 0.5×B1_H=7.5~12.5μm; the height Z2 of the organic insulating support structure supporting in the horizontal direction is 0.35×B1_H=5.25~8.75μm.

[0046] Figure 8 The diagram illustrates a comparison between traditional MEMS fabrication of micro-coaxial devices and the fabrication method of this invention. In the embodiments of this application, a comparison of fabrication complexity shows that the complexity of the 3D printing-MEMS fabrication process is far lower than that of traditional MEMS processes, and most importantly, it results in a significant reduction in fabrication costs. The cost of fabricating this structure using traditional MEMS processes is approximately 15 to 20 times that of this invention.

[0047] It should be understood that although the steps in the flowchart of this application are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowchart of this application may include multiple steps or multiple stages, which are not necessarily completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0048] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process, characterized in that, Includes the following steps: Step 1: Using 3D printing technology, an organic skeleton for the radio frequency micro-coaxial device, including a metal grounding shell and an organic support structure, is integrally formed. Metal layers are electroplated on the inner and outer surfaces of the metal grounding shell using MEMS technology. The organic support structure is fixed to the inner side of the metal grounding shell and is used to support the metal radio frequency transmission line located at the axis of the micro-coaxial device. Step 2: Print the metal radio frequency transmission line organic framework using 3D printing technology, and electroplate a metal layer on the surface of the metal radio frequency transmission line organic framework using MEMS process to prepare the metal radio frequency transmission line. Step 3: Assemble the organic framework of the radio frequency micro coaxial device and the metal radio frequency transmission line.

2. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 1, characterized in that, The RF micro coaxial device organic skeleton integrally formed by step 1 using 3D printing technology includes two symmetrical semi-enclosed structures along the axis: a first semi-enclosed structure and a second semi-enclosed structure. The first semi-enclosed structure includes a first part of a metal ground shell and a first part of an organic support structure fixed inside the first part of the metal ground shell. The second semi-enclosed structure includes a second part of a metal ground shell and a second part of an organic support structure fixed inside the second part of the metal ground shell.

3. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 2, characterized in that, The specific method for electroplating a metal layer on the inner and outer surfaces of the metal grounding shell in step 1 using MEMS technology is as follows: First, the first part and the second part of the organic support structure are covered, and a seed layer is applied to the surface of the first semi-closed structure and the second semi-closed structure. An adhesive layer is grown only on the inner and outer surfaces of the first part and the second part of the metal grounding shell. Then, electroplating is performed on the surface of the first part and the second part of the metal grounding shell where the adhesive layer is grown.

4. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 3, characterized in that, The specific method for joining and assembling the organic skeleton of the radio frequency micro coaxial device and the metal radio frequency transmission line in step 3 is as follows: First, the metal radio frequency transmission line is bonded to the support structure by heating and pressurizing; then, the first semi-enclosed structure and the second semi-enclosed structure are bonded by heating and pressurizing.

5. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 1, characterized in that, In step 1, when using 3D printing technology to integrally mold the organic skeleton of the radio frequency micro-coaxial device, which includes a metal grounding shell and an organic support structure, a hole is left on the metal grounding shell along the axial direction, with a hole width W. 孔洞 Width W of micro coaxial metal grounding housing 外导体 Satisfy: W 孔洞 <0.1×W 外导体 W 外导体 The value range is 15μm ~ 25μm, W 孔洞 The value range is 1.5μm ~ 2.5μm.

6. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 2, characterized in that, In step 1, the organic skeleton of the radio frequency micro coaxial device integrally formed by 3D printing technology has a metal grounding shell with equal height B1_H and width B1_W, where B1_W = B1_H = 15 mm ~ 25 μm, and the length B1_L of the metal grounding shell ranges from B1_L = 11 mm ~ 12 mm.

7. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 1, characterized in that, The specific method for electroplating a metal layer on the surface of the metal radio frequency transmission line organic framework in step 2 using MEMS technology is as follows: a seed layer is coated on the surface of the metal radio frequency transmission line organic framework, and an adhesion layer is grown on the surface of the metal radio frequency transmission line organic framework.

8. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 1, characterized in that, Step 1 uses organic materials to 3D print the organic framework of the radio frequency micro coaxial device, and step 2 uses organic materials to 3D print the organic framework of the metal radio frequency transmission line. The organic materials include ABS.

9. The method for fabricating radio frequency micro-coaxial devices based on a hybrid 3D printing and MEMS process according to claim 6, characterized in that, Both the first and second parts of the organic support structure include: an organic insulating support structure that provides support in the vertical direction and an organic insulating support structure that provides support in the horizontal direction. The height Z1 of the organic insulating support structure that provides support in the vertical direction is 0.5 × B1_H, and the height Z2 of the organic insulating support structure that provides support in the horizontal direction is 0.35 × B1_H.

10. The radio frequency microcoaxial device manufactured according to the processing method of claim 1, characterized in that, include: The device comprises a metal grounded housing, an organic support structure, and a metal radio frequency transmission line located at the center of a micro-coaxial axis. The organic support structure is fixed inside the metal grounded housing, and the metal radio frequency transmission line is bonded to the organic support structure. The metal radio frequency transmission line is suspended within a resonant air cavity enclosed by the metal grounded housing.

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