A Ka-band vertical transmission structure design method

Abstract

The application provides a Ka-band vertical transmission structure design method, adopts BGA balls to realize vertical interconnection of two layers of substrates, optimizes and determines the optimal BGA ball size, quantity and tear drop pad shape connected with the transmission line based on electromagnetic field simulation software, can improve radio frequency performance, and reduces signal transmission loss; a Ka-band multi-section wavelength transformer compensation circuit is designed on the CPW plane transmission band line of the lower substrate, based on the quarter wavelength transformer design technology, according to the characteristic transformation of different branches, the matching of a wider frequency range is realized; based on the electromagnetic field simulation software, the interconnection compensation circuit design is optimized, a new type of interconnection compensation circuit under multiple transmission modes is proposed, and the reflection and loss generated in the vertical interconnection process of the signal are reduced. The application not only solves the performance bottleneck of the traditional BGA ball interconnection in the application of the Ka-band, but also provides a miniaturization solution, greatly improves the transmission quality and stability of the signal in the vertical interconnection process.

Description

Technical Field

[0001] This invention relates to the field of electronic components technology, and specifically to a design method for a Ka-band vertical transmission structure. Background Technology

[0002] In multi-chip 3D-SIP (System in Package) architectures, achieving effective vertical interconnection of planar circuits between different layers is crucial for constructing a three-dimensional structure. Especially in the millimeter-wave band, the requirements for signal transmission paths are extremely high; even minor design flaws can lead to a significant degradation in signal quality. Miniaturized systems typically use BGA (Ball Grid Array) balls as supports between the 3D stacked layers of the RF substrate, while simultaneously achieving vertical connections for basic electrical signals. Currently, domestic 3D-SIP designs generally use BGA balls as a means of vertical interconnection for power or control signals, with a few used for vertical transmission of mid-to-low frequency signals below 4GHz. The discontinuity of the transmission structure does not significantly affect the signal.

[0003] The miniaturization and increased functionality of the system necessitate the integration of more chips, making the vertical transmission of signals in the millimeter-wave band above 30GHz an urgent necessity. However, the application of BGA ball interconnect technology in the millimeter-wave band still faces numerous challenges. Signal attenuation and distortion are major technical obstacles, affecting not only transmission quality but also limiting overall system performance. Furthermore, traditional compensation mechanisms are inadequate for miniaturized spatial layouts, leading to significant signal reflection and loss during vertical interconnection, severely impacting system reliability and stability.

[0004] Therefore, a vertical transmission structure and its design method applicable to the Ka band are needed. Summary of the Invention

[0005] This invention addresses the severe signal attenuation and distortion issues inherent in existing BGA ball interconnects at high frequencies, particularly in the Ka band. It provides a Ka-band vertical transmission structure design method that, through optimized interconnect compensation circuitry, precise control of the number and layout of BGA balls, and the design of matching schemes for various transmission modes, effectively improves the transmission performance of Ka-band signals, ensuring high fidelity during vertical interconnection in a confined space. This invention not only overcomes the performance bottleneck of traditional BGA ball interconnects in Ka-band applications but also provides a miniaturized solution, significantly enhancing the transmission quality and stability of signals during vertical interconnection, thus laying a solid foundation for the development of high-performance millimeter-wave RF microsystems.

[0006] This invention provides a Ka-band vertical transmission structure design method, comprising the following steps: S1. Construct a Ka-band vertical transmission structure. The Ka-band vertical transmission structure includes an upper substrate, a coplanar waveguide connected to the upper surface of the upper substrate, an inter-board coaxial cable connected inside the upper substrate and interconnected with the coplanar waveguide, a signal transmission inner conductor BGA solder ball located at the bottom of the upper substrate and interconnected with the inter-board coaxial cable, a solder ball shielding cavity located around the signal transmission inner conductor BGA solder ball, and a lower substrate connected to the bottom of the signal transmission inner conductor BGA solder ball and the solder ball shielding cavity. The solder ball shielding cavity consists of at least two grounded solder balls surrounding the outer periphery of the BGA solder ball, which is the inner conductor of the signal transmission circuit. The signal transmission inner conductor BGA solder ball is connected to the microstrip line on the upper surface of the lower substrate, receiving Ka-band signals and transmitting them vertically to the coplanar waveguide via inter-board quasi-coaxial transmission. S2. Perform a ball-planting simulation scan on the center distance R between the solder ball shielding cavity and the signal transmission inner conductor BGA solder ball and the grounding opening radius d of the upper substrate to obtain the R and d with the best transmission performance below 35GHz; S3. In the Ka-band vertical transmission structure, impedance matching design is carried out at frequencies above 35GHz, and the microstrip line of the lower substrate is set as a Ka-band multi-section wavelength converter and CPW planar transmission strip. The Ka-band multi-section wavelength converter includes a 1 / 4 wavelength line and a short-circuit branch. The 1 / 4 wavelength line is connected to the signal transmission inner conductor BGA solder ball and the CPW planar transmission strip line. The short-circuit branch is a microstrip line that is vertically and symmetrically connected to the 1 / 4 wavelength line. The width of the 1 / 4 wavelength line is the same as the width of the short-circuit branch. By simulating and scanning the 1 / 4 wavelength line length lx, width lw, and short-circuit branch length ly, the optimal dimensions for standing waves above 35 GHz were obtained, and the design results of the Ka-band vertical transmission structure were obtained.

[0007] In the Ka-band vertical transmission structure design method of the present invention, as a preferred embodiment, in step S1, the inter-board coaxial is equivalent to a coaxial transmission line, the inter-board via connecting the upper and lower layer signals is used as the transmission inner conductor, and multiple grounding vias are set on the periphery as a shielding layer.

[0008] In the preferred embodiment of the Ka-band vertical transmission structure design method of the present invention, in step S1, a ground plane is laid around the BGA solder ball of the inner conductor of signal transmission, and the BGA solder ball of the inner conductor of signal transmission and the ground solder ball are of the same size. The chip circuits of the Ka-band vertical transmission structure are all arranged on the upper surface of the upper and lower substrates, and coplanar waveguides are used for planar transmission to interconnect with the chip circuits over the shortest distance. The coplanar waveguide and the quarter-wavelength line extend in the same direction; In step S2, the capacitance effect is introduced by adjusting the solder ball size, R, and d. During simulation, the scanning range of R is 0.7mm to 0.9mm with a step of 0.1mm; the scanning range of d is 0.5mm to 0.6mm with a step of 0.1mm; and the scanning frequency range is 1 to 40GHz.

[0009] In the Ka-band vertical transmission structure design method of the present invention, as a preferred embodiment, in step S2, the diameter of the solder ball is 450μm. The optimal dimensions are obtained by simulation using HFSS software: d is 0.5mm, R is 0.7mm, the number of grounding solder balls is 5, and they avoid the microstrip lines of the lower substrate.

[0010] The Ka-band vertical transmission structure design method described in this invention, as a preferred approach, uses a 1 / 4 wavelength line to match the complex impedance load, and the short-circuit branch changes the reactance component in the load, located at the node or antinode of the voltage amplitude value.

[0011] In the Ka-band vertical transmission structure design method of the present invention, as a preferred embodiment, in step S3, the scanning range of lx is 1mm to 3mm with a step size of 0.1mm; the scanning range of lw is 0.1mm to 0.4mm with a step size of 0.05mm; and the scanning range of ly is 0.5mm to 2mm with a step size of 0.1mm.

[0012] In the Ka-band vertical transmission structure design method of the present invention, as a preferred embodiment, the width of the quarter-wavelength line and the width of the short-circuit branch are both 0.2 mm, the length of the quarter-wavelength line is 1.6 mm, the length of the short-circuit branch is 1 mm, and the distance between the left side of the short-circuit branch and the CPW plane transmission band line is 0.5 mm.

[0013] The present invention discloses a Ka-band vertical transmission structure design method, in which, as a preferred embodiment, the excitation signal is transmitted sequentially from the CPW planar transmission stripline to the Ka-band multi-section wavelength converter, the signal transmission inner conductor BGA solder ball, and the interior of the upper substrate, and then transmitted to the coplanar waveguide through inter-board coaxial transmission to complete one vertical transmission.

[0014] The present invention discloses a Ka-band vertical transmission structure design method, in which the Ka-band vertical transmission structure is used for vertical transmission of radio frequency signals in the range of 30~40GHz.

[0015] This invention provides a Ka-band vertical transmission structure design method that integrates vertical transmission coaxial cable, BGA sphere, and novel compensation structure into a unified modeling and simulation, achieving high-performance vertical transmission of BGA sphere in the millimeter-wave band. The resulting Ka-band 3D packaged low-loss vertical transmission structure can serve as an important transmission structure for millimeter-wave signals in miniaturized, highly integrated RF microsystems.

[0016] The related technologies relied upon in this invention include existing BGA ball interconnect technology and electromagnetic field simulation technology. BGA ball interconnect technology is widely used in multi-chip 3D-SIP (System in Package), but its application at high frequencies suffers from significant signal quality issues. Electromagnetic field simulation technology is an important tool in modern high-frequency circuit design; by simulating electromagnetic field distribution, circuit design can be optimized and signal transmission quality improved. However, existing BGA ball interconnect technology still faces many challenges in the Ka band, such as signal attenuation and distortion, which limits the overall system performance. Therefore, this invention aims to solve these problems by optimizing interconnect compensation circuits, precisely controlling the number and layout of BGA balls, and designing matching schemes for various transmission modes.

[0017] This invention uses BGA balls to achieve vertical interconnection between two substrates. Based on electromagnetic field simulation software optimization, the optimal size and number of BGA balls and the shape of the teardrop pads connected to the transmission lines are determined, which can improve radio frequency performance and reduce signal transmission loss. According to coaxial transmission line theory, the dimensions of a quasi-coaxial vertical conversion structure can be obtained using the characteristic impedance formula of a coaxial line. When signal transmission is achieved by connecting the upper and lower substrates with BGA solder balls, the solder ball is equivalent to a large inductor. Impedance mismatch inevitably leads to standing waves and deterioration of transmission performance. Therefore, compensation capacitors need to be introduced in the design to ensure good characteristic impedance matching along the transmission path. In this method, a ground plane is laid around the solder ball pads, and a ring of grounded solder balls of the same size is added around the solder balls. By adjusting the size of the solder balls, the distance between the grounded solder balls and the middle solder balls, and the distance between the ground plane and the middle solder ball pads, a capacitive effect can be introduced, achieving impedance matching to varying degrees.

[0018] This invention designs a Ka-band multi-section wavelength converter compensation circuit on the CPW planar transmission line of the lower substrate. Based on quarter-wavelength converter design technology, it achieves wider frequency range matching by transforming the characteristics of different branches. The interconnect compensation circuit design is optimized using electromagnetic field simulation software, and novel interconnect compensation circuits for various transmission modes are proposed to reduce signal reflection and loss during vertical interconnection.

[0019] This invention utilizes a quarter-wavelength line to match a load with complex impedance. In this case, the quarter-wavelength transmission line should be connected to a special position on the main transmission line, i.e., the input impedance should be purely resistive when viewed from that position towards the load. Obviously, this position is the node or antinode of the voltage amplitude value. However, due to size limitations, a short-circuit branch of appropriate length is connected in parallel at the load to change the reactance component in the load. Then, the characteristic impedance is determined using the quarter-wavelength line matching principle.

[0020] The present invention has the following advantages: The Ka-band vertical transmission structure design method provided by this invention effectively improves the transmission performance of Ka-band signals by optimizing interconnect compensation circuits, precisely controlling the number and layout of BGA balls, and designing matching schemes under various transmission modes, ensuring high fidelity of signals during vertical interconnection in a small space. This invention not only solves the performance bottleneck of traditional BGA ball interconnects in Ka-band applications but also provides a miniaturized solution, greatly improving the transmission quality and stability of signals during vertical interconnection, laying a solid foundation for the development of high-performance millimeter-wave RF microsystems. Attached Figure Description

[0021] Figure 1 A flowchart of a Ka-band vertical transmission structure design method; Figure 2 This is a diagram of a transmission structure using BGA balls to achieve vertical interconnection of two substrates in a Ka-band vertical transmission structure design method. Figure 3 Top perspective view of a BGA sphere layout for a Ka-band vertical transmission structure design method; Figure 4 A schematic diagram of the S-parameters of a BGA sphere vertical transmission simulation for a Ka-band vertical transmission structure design method. Figure 5 A cross-sectional view of a Ka-band multi-section wavelength converter based on a Ka-band vertical transmission structure design method; Figure 6 This is a simulation comparison diagram showing the design method of a Ka-band vertical transmission structure before and after optimization.

[0022] Figure label: 1. Upper substrate; 2. Coplanar waveguide; 3. Inter-board coaxial; 4. Signal transmission inner conductor BGA solder ball; 5. Solder ball shielding cavity; 6. Lower substrate; 7. Ka-band multi-section wavelength converter; 71. 1 / 4 wavelength line; 72. Short-circuit branch; 8. CPW planar transmission stripline. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example 1

[0024] like Figure 1 As shown, a Ka-band vertical transmission structure design method includes the following steps: S1. Construct a Ka-band vertical transmission structure. The Ka-band vertical transmission structure includes an upper substrate 1, a coplanar waveguide 2 connected to the surface of the upper substrate 1, an inter-board coaxial cable 3 connected inside the upper substrate 1 and interconnected with the coplanar waveguide 2, a signal transmission inner conductor BGA solder ball 4 located at the bottom of the upper substrate 1 and interconnected with the inter-board coaxial cable 3, a solder ball shielding cavity 5 located on the outer periphery of the signal transmission inner conductor BGA solder ball 4, and a lower substrate 6 connected to the bottom of the signal transmission inner conductor BGA solder ball 4 and the solder ball shielding cavity 5. The solder ball shielding cavity 5 consists of at least two grounded solder balls surrounding the outer periphery of the signal transmission inner conductor BGA solder ball 4, and the solder ball shielding cavity 5 is grounded; The signal transmission inner conductor BGA solder ball 4 is connected to the microstrip line of the lower substrate 6, receives Ka-band signals and transmits them vertically to the coplanar waveguide 2 through the inter-board quasi-coaxial 3; S2. Perform ball-planting simulation scanning on the center distance R between the solder ball shielding cavity 5 and the signal transmission inner conductor BGA solder ball 4 and the grounding aperture radius d on the upper surface of the lower substrate 6 to obtain the R and d with the best transmission performance below 35GHz. S3. In the Ka-band vertical transmission structure, impedance matching design is carried out at frequencies above 35GHz, and the microstrip line of the lower substrate 6 is set as a Ka-band multi-section wavelength converter 7 and a CPW planar transmission stripline 8. The Ka-band multi-section wavelength converter 7 includes a quarter-wavelength line 71 and a short-circuit branch 72. The quarter-wavelength line 71 is connected to the signal transmission inner conductor BGA solder ball 4 and the CPW planar transmission strip line 8. The short-circuit branch 72 is a microstrip line that is vertically and symmetrically connected to the quarter-wavelength line 71. The width of the quarter-wavelength line 71 is the same as the width of the short-circuit branch 72. By performing simulation scanning on the length lx and width lw of the quarter wavelength line 71 and the length ly of the short-circuit branch 72, the optimal dimensions for the standing wave above 35 GHz were obtained, and the design results of the Ka-band vertical transmission structure were obtained.

[0025] like Figure 2 The diagram shows a schematic of the vertical transmission structure designed in this invention. When using BGA spheres to achieve vertical interconnection between two substrates, the transmission path of the Ka-band RF signal is marked in the diagram. In this embodiment, the signal is transmitted from the upper surface of the lower substrate 6 towards the BGA sphere, then along the BGA sphere into the upper substrate 1, and finally transmitted to its upper surface via the coaxial vertical transmission structure inside the upper substrate 1. The chip circuits are all arranged on the upper surfaces of the upper and lower substrates. Due to the high chip density, the RF signal transmitted vertically on the upper surface adopts coplanar waveguide (CPW) planar transmission, which allows for the shortest possible interconnection with the chip circuits, avoiding secondary vertical transmission, effectively saving volume and reducing transmission loss.

[0026] As shown in the figure, the structure mainly consists of three parts: the first part is the planar transmission of the inter-board coaxial 3-to-coplanar waveguide (CPW) 2 of the upper substrate; the second part is the vertical interconnection of BGA balls; and the third part consists of the CPW planar transmission stripline 8 of the lower substrate 6 and the Ka-band multi-section wavelength converter 7.

[0027] The upper substrate (upper substrate 1) in the first part is a 4-layer M6 HDI board with a thickness of 0.58mm. It has a core-board laminated structure with a copper-clad laminate in the middle and stacked layers on both sides. The inter-board coaxial cable 2 can be equivalent to a coaxial transmission line, with the inter-board vias connecting the upper and lower layers as the transmission inner conductors and multiple grounding vias on the periphery as shielding layers.

[0028] The top perspective view of the BGA ball vertical interconnect section is shown below. Figure 2 As shown, the device includes a signal transmission inner conductor BGA solder ball 4 and a solder ball shielding cavity 5. The BGA solder ball is made of high-lead material and has a diameter of 450μm. R is the radius of the outer ring grounding solder ball shielding structure, and d is the radius of the grounding hole on the upper surface of the lower substrate. The simulation results show that the optimal dimensions are d = 0.5mm and R = 0.7mm.

[0029] Parts 1 and 2 describe the conventional routing structure design for vertical signal transmission through a BGA. In this routing method, the signal passes through different media, and the abrupt change in the transmission line port structure causes impedance mismatch. This impedance mismatch inevitably leads to standing waves and deterioration of transmission performance. Therefore, compensation capacitors need to be introduced into the design to ensure good impedance matching along the transmission path. A ground plane is laid around the solder ball pads, and a ring of grounded solder balls of the same size is added around the solder balls. By adjusting the size of the solder balls, the distance between the grounded solder balls and the central solder balls, and the distance between the ground plane and the vertical via, the capacitance effect can be introduced, achieving impedance matching to varying degrees. HFSS software was used for modeling and simulation. The top perspective view of the model is shown below. Figure 3 As shown, the solder ball size is selected as 0.45mm. d is set as the radius of the grounding hole on the upper surface of the substrate (upper substrate 1) in the first part, and R is the radius of the outer ring grounding solder ball shielding structure in the second part. The model is selected as follows. Figure 3 The two variables R and d, as indicated in the figure, are scanned. The scan range for R is 0.7mm–0.9mm with a step size of 0.1mm; the scan range for d is 0.5mm–0.6mm with a step size of 0.1mm. The scan frequency range is 1–40GHz. Impedance matching simulation is performed on the BGA solder balls to obtain the port return loss as shown below. Figure 4 and Figure 6 The lines before optimization are shown. Figure 4 As can be seen, the standing wave ratio can be optimized to 20dB below 35GHz, and the transmission performance is best when d is 0.5mm and R is 0.7mm.

[0030] For frequencies above 35GHz, achieving satisfactory matching characteristics remains challenging. To address this issue and achieve transmission characteristics above 35GHz, this application proposes a 1 / 4 wavelength converter design technique. This technique utilizes the characteristics of different branches to achieve matching over a wider frequency range. Here, we consider using a 1 / 4 wavelength line to match loads with complex impedances. The 1 / 4 wavelength transmission line should be connected to a specific location on the main transmission line, where the input impedance should appear purely resistive when viewed from the load. This location is clearly a node or antinode of the voltage amplitude. A short-circuit branch of appropriate length is connected in parallel at the load to alter the reactance component of the load. The main focus here is on designing a compensation circuit for the CPW planar transmission strip on the upper surface of the lower substrate in the third part of the transmission path. This compensation circuit is called the Ka-band multi-section wavelength converter 7.

[0031] The third part is the transmission structure on the upper surface of the lower substrate. The substrate material of the lower substrate 6 is a 4-layer M6 HDI board with a thickness of 0.58mm. It has a core-board laminated structure with a copper-clad laminate in the middle and laminated layers on both sides. The main elements include the CPW planar transmission bandline 8 and the Ka-band multi-section wavelength converter 7, such as... Figure 5 As shown. The signal transmission path is as follows: the excitation signal is transmitted from the lower substrate 6 of the third part to the BGA solder balls of the second part, and then to the upper surface of the upper substrate 1 of the first part, completing one vertical transmission.

[0032] The matching process requires the use of HFSS simulation software to model and simulate the overall transmission structure, and to adjust three parameters of the Ka-band multi-section wavelength converter 7 to obtain the best matching effect. Figure 5 The diagram also displays a top view of the Ka-band multi-section wavelength converter 7. A quarter-wavelength line 71 connects the CPW planar transmission strip line 8 and the solder ball circular pads. A short-circuit branch 72, symmetrical about its axis, is placed on the quarter-wavelength line 71. The length lx of the quarter-wavelength line 71, the width lw of the quarter-wavelength line 71, and the length ly of the short-circuit branch 72 are selected as parameters for scanning, and the optimal combination is chosen as the design dimensions. Specifically, lx has a scanning range of 1mm to 3mm with a step of 0.1mm; lw has a scanning range of 0.1mm to 0.4mm with a step of 0.05mm; and ly has a scanning range of 0.5mm to 2mm with a step of 0.1mm. Simulation results show that the transmission characteristics are best and the matching effect is optimal when lx is 1.4mm, lw is 0.2mm, and ly is 1mm.

[0033] Figure 6Simulation results for the vertical interconnect structure S11 before and after incorporating the Ka-band multi-section wavelength converter compensation circuit are presented. The results show that after incorporating the Ka-band multi-section wavelength converter compensation circuit, the S11 VSWR is better than 18 dB in the 30–40 GHz band, demonstrating significant optimization. At this point, the S21 insertion loss is less than 0.38 dB.

[0034] Through the above-described solution, this invention not only solves the performance bottleneck of traditional BGA ball interconnect in Ka-band applications, but also provides a flexible and diverse solution based on 1 / 4 wavelength converter design technology, which greatly improves the transmission quality and stability of signals in the vertical interconnect process and provides design ideas for the research and development of high-performance millimeter-wave communication systems.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A design method for a Ka-band vertical transmission structure, characterized in that: Includes the following steps: S1. Construct a Ka-band vertical transmission structure, which includes an upper substrate (1), a coplanar waveguide (2) connected to the upper surface of the upper substrate (1), an inter-board coaxial cable (3) connected to the interior of the upper substrate (1) and interconnected with the coplanar waveguide (2), a signal transmission inner conductor BGA solder ball (4) located at the bottom of the upper substrate (1) and interconnected with the inter-board coaxial cable (3), a solder ball shielding cavity (5) located on the outer periphery of the signal transmission inner conductor BGA solder ball (4), and a lower substrate (6) connected to the bottom of the signal transmission inner conductor BGA solder ball (4) and the solder ball shielding cavity (5). The solder ball shielding cavity (5) is composed of at least two grounded solder balls surrounding the outer periphery of the BGA solder ball (4) of the signal transmission inner conductor, and the solder ball shielding cavity (5) is grounded; The signal transmission inner conductor BGA solder ball (4) is connected to the microstrip line on the upper surface of the lower substrate (6), receives Ka band signals and transmits them vertically to the coplanar waveguide (2) through the inter-board coaxial (3). S2. Simulate and scan the center distance R between the solder ball shielding cavity (5) and the signal transmission inner conductor BGA solder ball (4) and the grounding opening radius d of the upper substrate (1) to obtain the R and d with the best transmission performance below 35GHz; S3. In the Ka-band vertical transmission structure, impedance matching design is carried out at frequencies above 35 GHz, and the microstrip line of the lower substrate (6) is set as a Ka-band multi-section wavelength converter (7) and a CPW planar transmission strip (8). The Ka-band multi-section wavelength converter (7) includes a 1 / 4 wavelength line (71) and a short-circuit branch (72). The 1 / 4 wavelength line (71) is connected to the signal transmission inner conductor BGA solder ball (4) and the CPW planar transmission strip line (8). The short-circuit branch (72) is a microstrip line that is vertically and symmetrically connected to the 1 / 4 wavelength line (71). The width of the 1 / 4 wavelength line (71) is the same as the width of the short-circuit branch (72). The optimal dimensions for the standing wave above 35 GHz were obtained by simulating and scanning the length lx and width lw of the 1 / 4 wavelength line (71) and the length ly of the short-circuit branch (72), and the design results of the Ka-band vertical transmission structure were obtained.

2. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: In step S1, the inter-board coaxial (3) is equivalent to a coaxial transmission line, with the inter-board through-hole connecting the upper and lower layer signals as the transmission inner conductor, and multiple grounding through-holes set on the periphery as a shielding layer.

3. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: In step S1, a grounding surface is laid around the signal transmission inner conductor BGA solder ball (4), and the signal transmission inner conductor BGA solder ball (4) and the grounding solder ball are the same size; The chip circuits of the Ka-band vertical transmission structure are arranged on the upper surface of the upper substrate (1) and the lower substrate (6), and coplanar waveguides are used for planar transmission to interconnect with the chip circuits with the shortest distance. The coplanar waveguide (2) and the 1 / 4 wavelength line (71) extend in the same direction; In step S2, the capacitance effect is introduced by adjusting the solder ball size, R, and d. During simulation, the scanning range of R is 0.7mm to 0.9mm with a step of 0.1mm; the scanning range of d is 0.5mm to 0.6mm with a step of 0.1mm; and the scanning frequency range is 1 to 40GHz.

4. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: In step S2, the diameter of the solder ball is 450μm. The optimal size is obtained by simulation using HFSS software: d is 0.5mm, R is 0.7mm, the number of grounding solder balls is 5, the included angle is 60°, and they avoid the microstrip line of the lower substrate (6).

5. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: The load with complex impedance is matched by the 1 / 4 wavelength line (71), and the short-circuit branch (72) changes the reactance component in the load, located at the node or bullion of the voltage amplitude value.

6. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: In step S3, the scanning range of lx is 1mm to 3mm with a step size of 0.1mm; the scanning range of lw is 0.1mm to 0.4mm with a step size of 0.05mm; and the scanning range of ly is 0.5mm to 2mm with a step size of 0.1mm.

7. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: The width of the 1 / 4 wavelength line (71) and the width of the short-circuit branch (72) are both 0.2 mm. The length of the 1 / 4 wavelength line (71) is 1.6 mm. The length of the short-circuit branch (72) is 1 mm. The distance between the left side of the short-circuit branch (72) and the CPW planar transmission band line (8) is 0.5 mm.

8. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: The excitation signal is transmitted sequentially from the CPW planar transmission strip (8) to the Ka-band multi-section wavelength converter (7), the signal transmission inner conductor BGA solder ball (4), and the interior of the upper substrate (1), and then transmitted to the coplanar waveguide (2) through the inter-board coaxial (3) to complete one vertical transmission.

9. The Ka-band vertical transmission structure design method according to claim 1, characterized in that: The Ka-band vertical transmission structure is used for vertical transmission of radio frequency signals in the 30-40 GHz range.

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