Interconnection structure of micro coaxial line and microstrip line

Abstract

The invention provides a micro-coaxial and microstrip line interconnection structure, and belongs to the technical field of microwave and radio frequency circuits, the micro-coaxial and microstrip line interconnection structure comprises an outer conductor, an inner conductor, a supporting sheet, a substrate and a microstrip line, the outer conductor is provided with an accommodating cavity, and the accommodating cavity is communicated with the outside along a first path to form a micro-coaxial interface; the inner conductor is inserted into the accommodating cavity along the first path, and the inner conductor is in clearance fit with the accommodating cavity to form a suspended state; the supporting sheet is connected with the outer conductor and the inner conductor and used for fixing the inner conductor. The substrate is arranged in the accommodating cavity, is located at the bottom of the inner conductor, provides supporting force for the inner conductor, and is conductively connected to the inner conductor and the outer conductor; the microstrip line is located outside the accommodating cavity and is conductively connected with the outer conductor and the inner conductor. The invention provides an interconnection structure of a micro-coaxial line and a microstrip line, and aims to solve the problems of low lead bonding strength and low reliability caused by the fact that an existing supporting structure is insufficient in strength and cannot bear pressure during bonding connection of the micro-coaxial line and the microstrip line.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave and radio frequency circuits, and more specifically, relates to an interconnection structure of micro-coaxial and microstrip lines. Background Art

[0002] Microcoaxial and microstrip interconnects offer advantages such as low transmission loss, high anti-interference capabilities, and miniaturization. They are primarily used in base station antennas, satellite communications, radar systems, microwave components, and other fields. In the microwave and RF circuit field, chips and microstrip transmission structures typically utilize a planar transition structure with a coplanar waveguide near the port, which facilitates interconnection operations such as wire bonding. Traditional microcoaxial 3D structures, when interconnected with chips or microstrip transmission structures, also require conversion of the 3D coaxial structure into a similar planar transition structure, which is then connected to the chip or microstrip transmission structure through wire bonding. In existing micro-coaxial transition structures, the inner conductor support structure is usually composed of a photosensitive organic polymer (such as SU8 material) to achieve a suspended state of the inner conductor, and the support structure is patterned through a standard photolithography process. However, the limited yield strength of SU8 material makes it difficult to withstand the forces and vibrations applied during gold wire bonding, posing a risk of breakage. This makes achieving high-performance, high-reliability gold wire interconnects a technical challenge in engineering applications. Due to the insufficient support capacity of SU8 material, the inner conductor of the micro-coaxial conductor is in a quasi-suspended state. While it can support its own weight, the support structure is susceptible to bending and deformation when subjected to greater external forces. During the gold wire bonding process, the bonding blade acting on the inner conductor surface not only generates temperatures of 150-200°C, but also applies hundreds of milliwatts of ultrasonic energy and tens of Newtons of pressure. The combined effects of the blade's heat, pressure, and ultrasonic vibrations cause the inner conductor to vibrate, dissipating the pressure and ultrasonic energy applied by the bonding blade. This ultimately significantly reduces the bond strength at the interface between the bond wire and the workpiece. After bonding, the wire bond strength is low and reliability is compromised, posing a significant safety hazard in practical engineering applications. Summary of the Invention

[0003] The purpose of the present invention is to provide an interconnection structure between micro-coaxial and microstrip lines, aiming to solve the problem that the existing support structure is insufficient in strength and cannot withstand the pressure during the bonding connection between the micro-coaxial and microstrip lines, resulting in low wire bonding strength and low reliability.

[0004] To achieve the above object, the technical solution adopted by the present invention is: In a first aspect, a micro-coaxial and microstrip line interconnection structure is provided, comprising: The outer conductor is provided with a receiving cavity, wherein the receiving cavity is connected to the outside along a first path to form a micro-coaxial interface; an inner conductor, inserted into the accommodating cavity along the first path, the inner conductor and the accommodating cavity being in a suspended state; a supporting sheet, connected to the outer conductor and the inner conductor respectively, and used to fix the inner conductor; a substrate, disposed in the accommodating cavity and located at the bottom of the inner conductor, the substrate providing support for the inner conductor and being conductively connected to the inner conductor and the outer conductor; and The microstrip line is located outside the accommodating cavity and is conductively connected to the outer conductor and the inner conductor.

[0005] In combination with the first aspect, in a possible implementation, the inner conductor is provided with a fixing hole along a second path, the second path is perpendicular to the first path, the outer conductor is provided with a fixing groove corresponding to the fixing hole, and the support sheet is inserted into the fixing hole and the fixing groove.

[0006] In combination with the first aspect, in a possible implementation manner, the outer conductor is provided with a patch hole, and the substrate is arranged in the patch hole.

[0007] In combination with the first aspect, in a possible implementation, the width of the patch hole in the second path is greater than that of the accommodating cavity, so that the substrate is conductively connected to the outer conductor along the up and down directions.

[0008] In combination with the first aspect, in a possible implementation, the outer conductor is further provided with a mounting groove, the microstrip line is embedded in the mounting groove, and is conductively connected to the outer conductor via bonding wires.

[0009] In combination with the first aspect, in a possible implementation, the outer conductor is further provided with an avoidance hole corresponding to the inner conductor, and the microstrip line is conductively connected to the inner conductor via a bonding wire.

[0010] In combination with the first aspect, in a possible implementation, the interconnection structure between the micro-coaxial and microstrip lines further includes a grounding connection column disposed in the mounting groove, the microstrip line is provided with a conductive hole adapted for the grounding connection column, and the grounding connection column is inserted into the conductive hole.

[0011] In combination with the first aspect, in a possible implementation, the outer conductor is provided with a filling port connected to the accommodating cavity.

[0012] In combination with the first aspect, in a possible implementation, the outer conductor includes a plurality of conductive layers distributed sequentially from bottom to top, the accommodating cavity is opened in the top two adjacent conductive layers, the mounting groove is opened at the bottom of the topmost conductive layer, and the bottom of the mounting groove is connected to the second topmost conductive layer.

[0013] The beneficial effect of the micro-coaxial and microstrip interconnect structure provided by the present invention is that, compared with existing technologies, the support stability of the inner conductor is significantly enhanced by the synergistic effect of the support plate and substrate. The support plate connects the outer and inner conductors, while the substrate provides reliable support for the inner conductor from the bottom. This overcomes the drawback of the insufficient yield strength of existing support structures, can easily withstand the multiple challenges of gold wire bonding pressure and high temperatures of 150-200°C, and avoids problems such as fracture and bending deformation of the support structure. During the bonding process, the inner conductor remains stable and free of vibration, allowing the pressure and ultrasonic energy applied by the bonding tool to be precisely applied to the bonding interface, significantly reducing energy dissipation and significantly improving the bond strength between the bonding wire and the workpiece. This effectively addresses the challenges of low wire bonding strength and poor reliability in existing technologies, mitigating safety risks in practical engineering applications. Furthermore, this rationally designed structure provides stable support while maintaining the inherent advantages of micro-coaxial and microstrip interconnects, such as low transmission loss, high anti-interference capabilities, and miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 A top view of the interconnection structure of micro-coaxial and microstrip lines provided by an embodiment of the present invention; Figure 2 for Figure 1 Sectional view along line AA; Figure 3 A partial schematic diagram of the interconnection structure of micro-coaxial and microstrip lines provided by an embodiment of the present invention; Figure 4 Another partial schematic diagram of the interconnection structure of micro-coaxial and microstrip lines provided by an embodiment of the present invention; Figure 5 This is a diagram of the internal structure of the interconnection structure of micro-coaxial and microstrip lines provided by an embodiment of the present invention.

[0016] In the figure: 1. Outer conductor; 101. Accommodating cavity; 102. Injection port; 103. Avoidance hole; 104. Patch hole; 2. Inner conductor; 3. Microstrip line; 4. Ground connection column; 5. Substrate; 6. Bonding lead; 7. Support sheet. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] In the claims, specification and the above-mentioned drawings of the present invention, unless otherwise expressly limited, the terms "first", "second" or "third" are used to distinguish different objects, rather than to describe a specific order. Unless otherwise specified, other directional words, such as "vertical", "clockwise", "counterclockwise" and the like, indicating directions or positional relationships are based on the directions and positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the specific scope of protection of the present invention. In the claims, specification and the above-mentioned drawings of the present invention, unless otherwise expressly limited, the terms "fixed connection" or "fixed connection" should be understood in a broad sense, that is, any connection method without a displacement relationship or relative rotation relationship between the two, that is, including non-detachable fixed connection, detachable fixed connection, integrated connection and fixed connection through other devices or elements. In the claims, specification and the above-mentioned drawings of the present invention, the terms "including", "having" and their variations are intended to mean "including but not limited to".

[0019] It should be noted that rectangular micro-coaxial structures are typically composed of two parallel, insulated conductors with a dielectric support material between them. The outer layer is a rectangular metal conductor, and the inner layer contains a central conductor. The central conductor needs to be suspended in the center of a closed metal cavity, so auxiliary mechanical support structures such as flexible and chemically stable polyimide are required. A microstrip line structure consists of a conductive strip located on the surface of a dielectric substrate with a ground plane below it. The dielectric substrate separates the conductive strip from the ground plane.

[0020] Please also refer to Figures 1 to 5The interconnection structure between the micro-coaxial cable and the microstrip line 3 provided by the present invention is now described. The interconnection structure between the micro-coaxial cable and the microstrip line 3 includes an outer conductor 1, an inner conductor 2, a support plate 7, a substrate 5, and a microstrip line 3. The outer conductor 1 is provided with a housing cavity 101, which is connected to the outside along a first path to form a micro-coaxial interface. The inner conductor 2 is inserted into the housing cavity 101 along the first path, and the inner conductor 2 and the housing cavity 101 are loosely matched to form a suspended state. The support plate 7 is respectively connected to the outer conductor 1 and the inner conductor 2 to fix the inner conductor 2. The substrate 5 is provided in the housing cavity 101 and is located at the bottom of the inner conductor 2. The substrate 5 provides support for the inner conductor 2 and is conductively connected to the inner conductor 2 and the outer conductor 1. The microstrip line 3 is located outside the housing cavity 101 and is conductively connected to the outer conductor 1 and the inner conductor 2.

[0021] Compared to existing technologies, the interconnection structure of micro-coaxial and microstrip lines 3 provided by the present invention significantly enhances the support stability of the inner conductor 2 by providing a support plate 7 that works in synergy with the substrate 5. The support plate 7 connects the outer conductor 1 and the inner conductor 2, while the substrate 5 provides reliable support for the inner conductor 2 from the bottom. This overcomes the drawback of the existing support structure's insufficient yield strength and can easily withstand the multiple challenges of gold wire bonding, such as pressure and high temperatures of 150-200°C, while preventing problems such as fracture and bending deformation of the support structure.

[0022] During the bonding process, the inner conductor 2 is stably supported and prevents vibration. This allows the pressure and ultrasonic energy applied by the bonding tool to be precisely applied to the bonding interface, significantly reducing energy dissipation and significantly improving the bond strength between the bonding wire 6 and the workpiece. This effectively addresses the challenges of low wire bonding strength and poor reliability in existing technologies, mitigating safety risks in practical engineering applications. Furthermore, this rationally designed structure provides stable support while maintaining the inherent advantages of the micro-coaxial and microstrip interconnect structures of low transmission loss, high anti-interference capabilities, and miniaturization.

[0023] Optionally, the substrate 5 is made of quartz.

[0024] Optionally, the substrate 5 is welded to the inner conductor 2 and the outer conductor 1 .

[0025] In some embodiments, see Figure 2 and Figure 5 The inner conductor 2 is provided with a fixing hole along the second path, the second path is perpendicular to the first path, the outer conductor 1 is provided with a fixing groove corresponding to the fixing hole, and the support sheet 7 is inserted into the fixing hole and the fixing groove.

[0026] In this embodiment, a plug-in method is adopted to connect the support plate 7 to the inner conductor 2 and the outer conductor 1. There is no need to use external connection components, which simplifies the connection steps. Moreover, compared with the conventional connection method, the plug-in connection method is not affected by temperature, humidity and surrounding components, and the connection is more stable, avoiding the loosening of the connection between the inner conductor 2, the outer conductor 1 and the support plate 7 due to excessive local force. During the bonding process, the stable connection can better maintain the stable position of the inner conductor 2, reduce the displacement or shaking caused by external force, and further ensure that the pressure and ultrasonic energy applied by the bonding knife are efficiently transmitted to the bonding interface, thereby improving the bonding strength. At the same time, this structural design enhances the vibration and impact resistance of the overall structure, and can ensure the stability of the relative position of the inner conductor 2 and the outer conductor 1 even in complex working environments, thereby maintaining the low transmission loss and strong anti-interference performance of the interconnection structure of the micro-coaxial and microstrip line 3. In some embodiments, see Figure 4 The outer conductor 1 is provided with a patch hole 104 , and the substrate 5 is arranged in the patch hole 104 .

[0027] The solution in this embodiment can directly connect the substrate 5 to the inner conductor 2 and the outer conductor 1 through the patch hole 104 after the inner conductor 2, the support plate 7 and the outer conductor 1 are assembled. The operation is simple and convenient, and there is no need to change the original micro-coaxial structure and assembly method. It can seamlessly connect the production line, avoid the debugging costs and production cycle extension caused by process changes, and effectively ensure production efficiency and product delivery progress.

[0028] In some embodiments, see Figure 2 The width of the patch hole 104 in the second path is greater than the accommodating cavity 101, so that the substrate 5 is conductively connected to the outer conductor 1 along the up and down directions. The patch hole 104 of a relatively large width provides ample installation space for the substrate 5, allowing the substrate 5 to be firmly in close contact with the outer conductor 1 in the vertical direction, forming a large-area conductive connection area, greatly enhancing the stability and reliability of the conductive connection, effectively reducing contact resistance, reducing signal transmission loss, and ensuring the transmission performance of the interconnection structure of the micro-coaxial and microstrip lines 3. After the substrate 5 enters the patch hole 104, the top surface directly fits with the inner conductor and the outer conductor 1 to achieve a conductive connection, making the installation tolerance of the substrate 5 higher. Even if there is a certain position deviation during the assembly process, it can ensure a good conductive connection between the substrate 5 and the outer conductor 1, reducing the assembly precision requirements and further improving the assembly efficiency. In addition, this structural design does not require complex shape modification of the substrate 5 or the outer conductor 1, and can achieve efficient conductive connection while maintaining the simplicity of the original structure.

[0029] In some embodiments, see Figure 3The outer conductor 1 is also provided with a mounting groove, the microstrip line 3 is embedded in the mounting groove, and is conductively connected to the outer conductor 1 through a bonding wire 6. The mounting groove not only provides a space for the microstrip line 3 to be embedded, but also enables precise positioning of the microstrip line 3, making the installation process of the microstrip line 3 simpler and more efficient, without the need for complex positioning and calibration operations, greatly shortening the assembly time and improving production efficiency. At the same time, the tight fit between the microstrip line 3 and the mounting groove, combined with the conductive connection method of the bonding wire 6, enhances the reliability of the connection between the microstrip line 3 and the outer conductor 1, effectively avoiding loosening or displacement caused by external forces, and ensuring the stability of the signal transmission path. In terms of signal transmission, this structural design reduces signal loss and interference caused by unstable connection, ensuring the performance advantages of low transmission loss and high anti-interference capability of the interconnection structure between the micro-coaxial and microstrip line 3.

[0030] In some embodiments, see Figure 3 The outer conductor 1 is further provided with an avoidance hole 103 corresponding to the inner conductor 2 , and the microstrip line 3 is conductively connected to the inner conductor 2 via a bonding wire 6 . The avoidance hole 103 provides a spatial guide for the bonding operation between the microstrip line 3 and the inner conductor 2, preventing the outer conductor 1 from interfering with the bonding process, effectively improving the accuracy and reliability of the connection between the bonding lead 6 and the inner conductor 2, and ensuring the stability and smoothness of the current conduction path. At the same time, this design simplifies the assembly process. The assembler can quickly complete the connection operation between the microstrip line 3, the bonding lead 6 and the inner conductor 2 without the need for additional complex alignment and debugging, which greatly shortens the assembly time and improves production efficiency. At the signal transmission level, the precise connection method effectively reduces the loss and interference during the signal transmission process, further ensuring the performance advantages of low transmission loss and high anti-interference of the interconnection structure between the micro-coaxial and microstrip line 3. In addition, the setting of the avoidance hole 103 optimizes the internal space layout of the outer conductor 1, while achieving efficient conductive connection, making full use of the structural space, which helps to maintain the miniaturization characteristics of the interconnection structure.

[0031] In some embodiments, see Figure 3 The interconnection structure between the micro-coaxial and microstrip lines 3 further includes a ground connection column 4 provided in the mounting groove. The microstrip line 3 is provided with a conductive hole adapted to the ground connection column 4, and the ground connection column 4 is inserted into the conductive hole. The ground connection column 4 is inserted into the conductive hole, forming a stable and low-impedance ground path, which greatly improves the grounding reliability of the interconnection structure, effectively dissipates static electricity and stray currents, and avoids signal interference and equipment failure caused by charge accumulation. During signal transmission, a reliable ground connection can suppress electromagnetic interference and enhance signal stability, further ensuring the low transmission loss and high anti-interference performance advantages of the micro-coaxial and microstrip line 3 interconnection structure, and ensuring the accuracy and integrity of signal transmission. At the same time, this structural design makes the ground connection operation more convenient and efficient. The precise adaptation of the ground connection column 4 to the conductive hole reduces the time and difficulty of debugging the ground connection during assembly, improving assembly efficiency.

[0032] In some embodiments, see Figure 3 The outer conductor 1 is provided with a filling port 102 connected to the accommodating cavity 101 . After the micro-coaxial structure is fabricated, a dissolving liquid is poured into the cavity 101 of the outer conductor 1 through the filling port 102. The dissolving liquid reacts with the photoresist filled in the cavity 101 during processing, effectively decomposing the photoresist. The dissolved liquid mixture then flows smoothly out through the filling port 102, completely removing the photoresist and transforming the cavity 101 into a pure air cavity. Compared to traditional micro-coaxial structures filled with a dielectric (photoresist), the use of air as the transmission medium optimizes product size. Without considering the space occupied by the dielectric material, the overall structure can be further compacted, meeting the stringent miniaturization requirements of modern communication equipment. Furthermore, the air medium has extremely low dielectric loss, effectively reducing power loss during signal transmission and significantly improving signal transmission efficiency and stability.

[0033] In some embodiments, see Figure 2 The outer conductor 1 includes multiple conductive layers distributed sequentially from bottom to top, the accommodating cavity 101 is opened in the two adjacent conductive layers at the top, the mounting groove is opened at the bottom of the topmost conductive layer, and the bottom of the mounting groove is connected to the second topmost conductive layer.

[0034] After introducing the substrate 5 structure, by creating mounting slots to adjust the ground line width of the topmost conductive layer, the parasitic capacitance generated by substrate 5 can be significantly reduced, precisely meeting impedance matching requirements. This overcomes the technical bottleneck of the traditional GSG structure, which struggles to simultaneously meet TEM impedance and probe interface line spacing. This allows for independent control of the GSG probe interface line spacing, significantly improving the signal transmission performance and adaptability of the interconnect structure. To address the issue of the topmost layer being larger than the next-top layer in actual simulations, which violates standard micro-coaxial process technology, substrate 5 is placed at the interface between the topmost and next-top layers. A sputtered metal layer on substrate 5 provides reliable support for the growth of the topmost metal layer, ensuring process feasibility and stability and avoiding product quality issues caused by process conflicts. This structural design fully leverages the advantages of substrate 5 in strengthening support for the inner conductor 2 while effectively mitigating its negative impacts. While ensuring structural performance, it meets standard micro-coaxial process requirements and reduces manufacturing difficulty and cost.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. The interconnection structure of micro-coaxial and microstrip lines is characterized by: include: The outer conductor is provided with a receiving cavity, wherein the receiving cavity is connected to the outside along a first path to form a micro-coaxial interface; an inner conductor, inserted into the accommodating cavity along the first path, the inner conductor and the accommodating cavity being in a suspended state; a supporting sheet, connected to the outer conductor and the inner conductor respectively, and used to fix the inner conductor; a substrate, disposed in the accommodating cavity and located at the bottom of the inner conductor, the substrate providing support for the inner conductor and being conductively connected to the inner conductor and the outer conductor; as well as The microstrip line is located outside the accommodating cavity and is conductively connected to the outer conductor and the inner conductor.

2. The interconnection structure of micro-coaxial and microstrip lines according to claim 1, characterized in that: The inner conductor is provided with a fixing hole along a second path, the second path is perpendicular to the first path, the outer conductor is provided with a fixing groove corresponding to the fixing hole, and the support sheet is inserted into the fixing hole and the fixing groove.

3. The interconnection structure of micro-coaxial and microstrip lines according to claim 1, wherein: The outer conductor is provided with a patch hole, and the substrate is arranged in the patch hole.

4. The interconnection structure of micro-coaxial and microstrip lines according to claim 3, characterized in that: The width of the patch hole in the second path is greater than that of the accommodating cavity, so that the substrate is conductively connected to the outer conductor along the up and down directions.

5. The interconnection structure of micro-coaxial and microstrip lines according to claim 1, wherein: The outer conductor is further provided with a mounting groove, the microstrip line is embedded in the mounting groove, and is electrically connected to the outer conductor via bonding wires.

6. The interconnection structure of micro-coaxial and microstrip lines according to claim 1, wherein: The outer conductor is further provided with an escape hole corresponding to the inner conductor, and the microstrip line is conductively connected to the inner conductor via a bonding wire.

7. The interconnection structure of micro-coaxial and microstrip lines according to claim 5, characterized in that: The interconnection structure of the micro-coaxial and microstrip lines further includes a ground connection column arranged in the mounting groove. The microstrip line is provided with a conductive hole adapted for the ground connection column, and the ground connection column is inserted into the conductive hole.

8. The interconnection structure of micro-coaxial and microstrip lines according to claim 1, wherein: The outer conductor is provided with a filling port connected to the accommodating cavity.

9. The interconnection structure of micro-coaxial and microstrip lines according to claim 5, characterized in that: The outer conductor includes multiple conductive layers distributed sequentially from bottom to top, the accommodating cavity is opened in the two adjacent conductive layers at the top, the mounting groove is opened at the bottom of the topmost conductive layer, and the bottom of the mounting groove is connected to the second topmost conductive layer.

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