High-frequency connection line

Abstract

A high-frequency connection line according to one embodiment includes: a first main line including a first signal line and a first ground line of a first high-frequency line; and a second main line including a second signal line and a second ground line of a second high-frequency line. The first signal line and the second signal line are connected via the bonding of the first signal pad and the third signal pad, the first ground line and the second ground line are connected via the bonding of the first ground line pad and the third ground line pad, and the gap between the third signal pad and the ground line layer is configured to be smaller than 1 / 4 of the wavelength in the tube. The interval between the second signal pad and the second ground pad is configured to be narrower than the interval between the second signal line and the second ground.

Description

Technical Field

[0001] This disclosure relates to a high-frequency connection line, and more specifically, to a high-frequency connection line that connects high-frequency lines with different end configurations in a connection region, thereby matching not only the characteristic impedance of the connection region at the end of the high-frequency lines with the desired characteristic impedance, but also the overall characteristic impedance of the portion outside the connection region with the desired characteristic impedance. Background Technology

[0002] In high-frequency lines with specified characteristic impedances, reducing reflection loss in the connection area is usually considered an important issue when the line terminals of each high-frequency line are electrically connected to each other relative to ground.

[0003] Especially in optical modules frequently used in optical communication systems, such as TOSA (Transmit Optical Sub-Assembly), ROSA (Receiver Optical Sub-Assembly), BOSA (Bi-directional Optical Sub-Assembly), CDM (Coherent Driver Modulators), and ICR (Intradyne Coherent Receiver), heterogeneous substrate bonding is typically used, which joins high-frequency lines on a rigid substrate with high-frequency lines on a flexible substrate. In high-speed broadband optical communication systems with even higher baud rates (200GBd), suppressing the reflection loss of high-frequency signals transmitted in the region of heterogeneous substrate bonding is an urgent issue that needs to be addressed.

[0004] For example, the metal pads at the ends of the high-frequency lines constituting the rigid substrate are located on the surface of the rigid substrate. On the other hand, the metal pads leading to the flexible substrate for bonding with these metal pads are located on the lower surface of the flexible substrate. However, typically the high-frequency signal lines are located on the upper surface of the flexible substrate. Therefore, in the region where dissimilar substrates are bonded, there is a need for high-frequency signal lines to be routed from the metal pads on the lower surface of the flexible substrate to the upper surface. With such high-frequency connection lines, it is relatively difficult to achieve characteristic impedance matching aimed at reducing reflection loss. Nevertheless, in conventional optical modules, high-frequency connection lines that reduce the change in characteristic impedance after bonding by optimizing the shape of the high-frequency lines on both the rigid and flexible substrates are widely used.

[0005] The high-frequency circuits formed on the flexible substrates used in conventional optical modules typically employ a microstrip circuit structure with signal lines on the upper surface and ground conductors on the lower surface (see, for example, Patent Document 1 and Patent Document 2). Microstrip circuits are among the simplest types of high-frequency circuits, and the main reason for their adoption is that they can be manufactured with high precision at a relatively low cost (see Patent Document 2).

[0006] Reference Figure 1 The structure of the connection region when the ends of the high-frequency lines on the rigid substrate (100) and the ends of the high-frequency lines on the flexible substrate (200) are joined in a mutually opposing manner will be described. Figure 1 (a) is a top view of the connected region. Figure 1 (b) is the Ib-Ib cross-sectional view of the connecting region. Figure 1 (c) is a bottom view of the flexible substrate (200).

[0007] In the rigid substrate (100), a differential microstrip line consisting of two signal lines (101) patterned using the first wiring layer (111) of the rigid substrate is provided on its upper surface. At this time, the ground line defining the ground potential of the differential microstrip line of the rigid substrate (100) is the second wiring layer (112) and the third wiring layer (113) located on the lower layer of the rigid substrate (100). The ground potentials of the first wiring layer (111), the second wiring layer (112), and the third wiring layer (113) are common through ground vias (VIA) (not shown) penetrating the rigid substrate (100). A first insulating layer (114) and a second insulating layer (115) are formed between each wiring layer.

[0008] On the other hand, the flexible substrate (200) has a differential microstrip line on its upper surface, consisting of two signal lines (201) patterned using the first wiring layer (221) of the flexible substrate (200). In the second wiring layer (222) located on the back side of the flexible substrate (200), signal pads (202) and ground pads (211) for bonding with the rigid substrate (100) are patterned and positioned accordingly. The ends of the first wiring layer (221) of the flexible substrate (200) and the signal pads (212) and ground pads (211) of the newly formed second wiring layer (222) are independently formed on the upper and lower surfaces of the first insulating layer (223) of the flexible substrate (200), respectively, and are therefore not electrically connected to each other in this state. Therefore, signal vias (202) and ground vias (204) for penetrating and conducting through the first insulating layer (223) of the flexible substrate (200) are provided at designated positions. At this time, in order to suppress the significant decrease in characteristic impedance at the junction, a ground wire opening (126) is selectively introduced into the second wiring layer 112 constituting the rigid substrate (100).

[0009] Figure 2 This is to facilitate separation by each function. Figure 1 The diagram shown illustrates the discussion of the construction of previous connection regions. Figure 2 (a) is a top view of the connection area of ​​a conventional high-frequency connection line. Figure 2 (b) is a hypothetical diagram on paper, divided according to each function. Figure 2 (b) has a first high-frequency circuit formed on the upper surface of the rigid substrate (100) on its left side. Figure 2 (b) has a second high-frequency line formed on the upper surface of the flexible substrate (200) on the right side. It can be seen that their respective structural features differ. For example, the line width and the line spacing are significantly different. Thus, generally speaking, when using substrates with different materials and thicknesses constituting the insulating layer, even if the characteristic impedance is the same, the shape and arrangement of the resulting metal pattern that forms the high-frequency line may not be consistent. Therefore, when joining one end and the other end of two high-frequency lines in a mutually opposing manner, a high-frequency connection line with a special structure is required. Located in Figure 2 (b) The central structure is equivalent to a high-frequency connection line.

[0010] exist Figure 2In the flexible substrate (200) of the high-frequency connection line in the center of (b), a signal line tapered portion (203) is introduced into the first wiring layer (221) on the upper surface, and a ground line tapered portion (213) is introduced into the second wiring layer (222) on the lower surface. On the other hand, in the rigid substrate (100) of the high-frequency connection line, a signal line spacing transformation portion (102) is introduced into the first wiring layer 111 on the upper surface. Moreover, directly below the area where the high-frequency connection lines of the flexible substrate (200) and the high-frequency connection lines of the rigid substrate (100) are joined to each other by solder (300) or the like, a ground line opening (126) is selectively introduced into the second wiring layer 112 of the rigid substrate (100).

[0011] However, unlike previous optical communications that were the targets of Patent Documents 1 and 2, the design of the high-frequency connection lines installed inside the optical modules used in high-baud-rate 200GBd optical communications has undergone a significant shift from lumped constant processing to distributed constant processing in the optical module design. Especially... Figure 1 In this context, the area requiring such processing is called the signal line tapered portion (203). For the signal line tapered portion (203) to function as a high-frequency signal line, a ground wire, serving as a reference, is needed directly beneath the first insulating layer (223) of the flexible substrate (200) in the second wiring layer (222). However, as from... Figure 1 As can be understood from the bottom view of the flexible substrate (200) shown in (c), in order to prevent short circuits with the signal pads (212) provided by the second wiring layer (222), a specified gap is provided between the ground layer (210) that provides the reference potential and the signal pads (212).

[0012] If the size (length in the X-axis direction) of the gap between the ground layer (210) and the signal pad (212) is sufficiently small compared to (1 / 16) to (1 / 4) of the wavelength of the high-frequency signal propagating in the signal line taper (203) of the second wiring layer (221) (the wavelength along the signal line (201)), then if this gap can be treated as a lumped constant and electrically corrected in the flexible substrate (200), the reflection of the high-frequency signal in the signal line taper (203) will be relatively rare. However, in optical communication with a high baud rate of 200 GBd, the frequency of the high-frequency signal used exceeds 100 GHz. As a result, the length of (1 / 16) to (1 / 4) of the wavelength exceeding 100 GHz becomes smaller than the size of this gap, making it difficult to treat this gap portion as a lumped constant electrically. In this gap, i.e., in the signal line taper (203), strong inductance will occur. Figure 3 The S-parameters and characteristic impedance of a conventional high-frequency connection line with a gap size of 200 μm are shown. Figure 3(a) represents the curve trajectory of the reflection loss of the S-parameter. Figure 3 (b) represents the curve trajectory of the S-parameter through loss. Figure 3 (c) represents the simulated waveform of the characteristic impedance curve obtained by TDR (time-domain reflectometry). It clearly shows the high impedance characteristic caused by inductive behavior. Therefore, for high-frequency signals used in 200GBd optical communication, it is difficult to apply methods such as... Figure 1 and Figure 2 The high-frequency connection line shown is based on existing technology.

[0013] Prior art literature

[0014] Patent documents

[0015] Patent Document 1: Japanese Patent Application Publication No. 2007-123741

[0016] Patent Document 2: Japanese Patent Application Publication No. 2010-200234 Summary of the Invention

[0017] As mentioned above, in high-frequency connection lines, the characteristic impedance increases due to the inductive behavior, resulting in a characteristic impedance mismatch and thus degrading the signal quality of high-frequency signals.

[0018] This disclosure was made in view of the above-mentioned problems, and provides a high-frequency connection line in which the characteristic impedance is matched when the ends of high-frequency lines formed on different substrates are connected to each other in a manner that abuts against each other at the ends of the respective substrates.

[0019] One embodiment of the present invention is a high-frequency connection circuit that electrically connects a first high-frequency line formed on a first insulating substrate and a second high-frequency line formed on a second insulating substrate different from the first substrate.

[0020] A first high-frequency circuit in a high-frequency connection circuit according to one embodiment includes: a first main circuit formed on the upper surface of a first substrate and having conductivity, the first main circuit having a first signal line; a first signal pad formed on the upper surface of the first substrate and electrically connected to the end of the first signal line; and a first ground pad formed on the upper surface of the first substrate.

[0021] A second high-frequency circuit in one embodiment of a high-frequency connection circuit includes: a second main circuit formed on the upper surface of a second substrate and having conductivity, the second main circuit having two signal lines and a second ground line formed on the upper surface of the second substrate; a second signal pad formed on the upper surface of the second substrate and electrically connected to the end of the second signal line; a second ground pad formed on the upper surface of the second substrate and electrically connected to the end of the second ground line; a third signal pad formed on the lower surface of the second substrate directly below the second signal pad; and a ground layer formed on the lower surface of the second substrate to surround the third signal pad, including the third ground pad formed on the lower surface of the second substrate directly below the second ground pad.

[0022] The first signal pad and the third signal pad are opposite each other and connected, and the first ground pad and the third ground pad are opposite each other and connected.

[0023] In one embodiment of the high-frequency connection line, the gap between the third signal pad and the ground plane in the long dimension direction of the second high-frequency line is smaller than 1 / 4 of the wavelength inside the tube, the width of the second signal pad in the direction perpendicular to the long dimension direction of the second high-frequency line is wider than the width of the second signal line in the direction perpendicular to the long dimension direction of the second high-frequency line, and the spacing between the second signal pad and the second ground pad is configured to be narrower than the spacing between the second signal line and the second ground plane.

[0024] According to the embodiments of the present invention, a high-frequency connection line with matched characteristic impedance can be provided. Attached Figure Description

[0025] Figure 1 The diagram illustrates the structure of the connection area of ​​a conventional high-frequency connection line. (a) is a top view of the connection area, (b) is a cross-sectional view at the Ib-Ib line of (a), and (c) is a bottom view of the flexible substrate (200).

[0026] Figure 2 In the diagram, (a) is a top view of the connection area of ​​the conventional high-frequency connection line, and (b) is a diagram divided according to each function.

[0027] Figure 3 These are graphs representing the S-parameters and characteristic impedance of conventional high-frequency connection lines. (a) is the curve trajectory of reflection loss, (b) is the curve trajectory of through loss, and (c) is the curve trajectory of characteristic impedance obtained through TDR.

[0028] Figure 4 In the diagram, (a) is a top view of the high-frequency connection line (1) of the first embodiment of the present disclosure, and (b) is a cross-sectional view of the IVb-IVb line in (a).

[0029] Figure 5 In the middle, (a) is with Figure 4 (a) is a top view of the high-frequency connection line (1) corresponding to the first embodiment, (b) is a top view of the end of the first differential high-frequency line (2), and (c) is a top view of the end of the second differential high-frequency line (3).

[0030] Figure 6 In the middle, (a) is with Figure 4 (a) is a top view of the high-frequency connection line (1) corresponding to the first embodiment, and (b) is a view of the high-frequency connection line (1) corresponding to the first embodiment. Figure 5 (c) is the top view of the second differential high-frequency line (3), and (c) is the bottom view of the second differential high-frequency line (3).

[0031] Figure 7 In the middle, (a) is with Figure 4 (a) is a top view of the high-frequency connection line (1) of the first embodiment, and (b) is a diagram of the high-frequency connection line (1) divided into regions according to each function (1-1, 1-2, 1-3).

[0032] Figure 8 The graphs represent the S-parameters and characteristic impedance of the high-frequency connection line in the first embodiment. (a) is the curve trajectory of reflection loss, (b) is the curve trajectory of loss, and (c) is the curve trajectory of characteristic impedance obtained by TDR.

[0033] Figure 9 The diagram shows the location and shape (3-10-1, 3-10-2, 3-10-3, 3-10-4) of the semi-through holes formed on the second substrate in the first embodiment where the second high-frequency circuit (3) is formed.

[0034] Figure 10 In the diagram, (a) is a top view of the high-frequency connection line (7) of the second embodiment of the present disclosure, and (b) is a cross-sectional view of the IXb-IXb line in (a).

[0035] Figure 11 In the middle, (a) is with Figure 10 (a) is a top view of the high-frequency connection line (7) corresponding to the second embodiment, (b) is a top view of the end of the first differential high-frequency line (2), and (c) is a top view of the end of the second differential high-frequency line (8).

[0036] Figure 12 In the middle, (a) is with Figure 10 (a) is a top view of the high-frequency connection line (1) corresponding to the second embodiment, and (b) is a view of the high-frequency connection line (1) corresponding to the second embodiment. Figure 11 (c) is the top view of the corresponding second differential high-frequency line (8), and (c) is the bottom view of the second differential high-frequency line (8).

[0037] Figure 13 In the middle, (a) is with Figure 10 (a) is a top view of the high-frequency connection line (7) of the corresponding second embodiment, and (b) is a diagram of the high-frequency connection line (7) after dividing it into regions according to each function (7-1, 7-2, 7-3).

[0038] Figure 14 The graphs represent the S-parameters and characteristic impedance of the high-frequency connection line in the second embodiment. (a) is the curve trajectory of reflection loss, (b) is the curve trajectory of loss, and (c) is the curve trajectory of characteristic impedance obtained by TDR.

[0039] Figure 15 In the diagram, (a) is a top view of the high-frequency connection line (9) of the third embodiment of the present disclosure, (b) is a cross-sectional view of the XVb-XVb line in (a), and (c) is a cross-sectional view of the XVc-XVc line in (a). Detailed Implementation

[0040] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The same or similar reference numerals in the following description denote the same or similar elements, and repeated descriptions may be omitted. The values ​​and materials in the following description are illustrative, and other values ​​and materials may be used to implement the present disclosure without departing from its spirit.

[0041] In this embodiment, the material of the first substrate on which the first differential high-frequency circuit (2) is formed is polyimide (relative permittivity 3.5), and the material of the second substrate on which the second differential high-frequency circuit (3) is formed is a low-loss resin material (relative permittivity 3.46). However, it is not limited to this. Of course, the materials of the first substrate and the second substrate can be quartz glass (relative permittivity 3.8), silicon nitride film (relative permittivity 7), alumina ceramic (relative permittivity 9.8), compound semiconductor InP (relative permittivity 12.4), etc., respectively. Other materials with insulating properties can also be used. Moreover, in this embodiment, the conductor film is copper foil, but it is by no means limited to this. Of course, aluminum foil film, gold foil film, nickel film or palladium film, or composite metal film of one or more of them can also be used. Furthermore, in the following embodiments, a set of differential high-frequency circuits (2, 3) is bonded as a differential high-frequency circuit (1), but it can be extended to a configuration of bonding multiple sets of differential high-frequency circuits. Furthermore, as a replacement for a set of differential high-frequency lines, it can be changed to a configuration that combines a set of single-phase high-frequency lines, and it can also be extended to a configuration that combines multiple sets of single-phase high-frequency lines.

[0042] Furthermore, the first substrate having the first differential high-frequency line (2) has six conductor layers, but the total number of conductor layers is not limited to this; fewer or more than six layers can also be used. In addition, multiple through holes (3-4) are formed at the ends of the differential high-frequency line of the second substrate having the second differential high-frequency line, but conductor-embedded through holes can also be used.

[0043] (First Embodiment)

[0044] Reference Figures 4 to 9 The high-frequency connection line (1) of the first embodiment of this disclosure will be described. The high-frequency connection line (1) is formed by joining the end of a first differential high-frequency line (2) formed on a first substrate with the end of a second differential high-frequency line (3) formed on a second substrate. The high-frequency connection line (1) is configured as follows ( Figure 7 (b) : Functionally, a first high-frequency line (1-1) formed on the upper surface of the first substrate is arranged on the left side, a second high-frequency line (1-3) formed on the upper surface of the second substrate is arranged on the right side, and a high-frequency connection line (1-2) is arranged in the center. This configuration is consistent with... Figure 2 The configuration of the conventional high-frequency connection line shown in (b) is the same.

[0045] The first differential high-frequency circuit (2) has a group of positive lines (2-1-1) and negative lines (2-1-2) on the upper surface of the first substrate (also referred to as a group of positive signal lines and negative signal lines or simply a group of lines), and ground lines (2-1-3, 2-1-4) with ground potential are provided on both sides of the group of lines. A ground layer (2-2) is provided on the conductor layer directly below the group of lines, and a bottom ground layer (2-3) is provided on the lowest surface of the first substrate. Ground vias (2-1-5, 2-1-6) are provided to set the potential of all ground layers (2-2) and bottom ground layer (2-3) to ground potential. Insulating layers (2-4, 2-5) are introduced between all conductor layers. A portion of the ground wire (2-1-3, 2-1-4) of the first differential high-frequency line (2) located below the grounding layer (3-1-3, 3-1-4) in the second differential high-frequency line (3) described later constitutes a ground pad. This ground pad provides a bonding area with the ground pad formed by a portion of the grounding layer (3-6) in the second differential high-frequency line (3) on the lower surface of the second substrate.

[0046] On the other hand, the second differential high-frequency circuit (3) has a group of positive lines (3-1-1) and negative lines (3-1-2) (a group of positive signal lines and negative signal lines, or simply a group of lines) on the upper surface of the second substrate, as well as positive signal pads and negative signal pads formed at the ends of the group of lines. The positive signal pads and negative signal pads have circular pads (3-3), through holes (3-4) penetrating the center of the circular pads, and waist lines (3-5) connecting the circular pads. In addition, ground lines (3-1-3, 3-1-4) with ground potential are provided on both sides of the positive lines (3-1-1) and negative lines (3-1-2). Moreover, the second differential high-frequency circuit (3) has a positive pad (3-7-1), a negative pad (3-7-2), and a ground layer (3-6) formed on the same surface surrounding the positive pads and negative pads on the bottom surface of the second substrate. A portion of the grounding layer (3-6) in the second differential high-frequency line (3), located opposite to the grounding pad formed by a portion of the grounding wires (2-1-3, 2-1-4) in the aforementioned first differential high-frequency line (2), constitutes a grounding pad. Furthermore, a portion of the grounding pad located above the portion of the grounding layer (3-6) in the grounding wires (3-1-3, 3-1-4) also constitutes a grounding pad. A portion of the grounding layer (3-6) is connected to a portion of the grounding layer (3-1-3, 3-1-4) via grounding vias (3-1-5, 3-1-6). Additionally, an insulating layer (3-8) is introduced between the conductor layer on the upper surface and the conductor layer on the lower surface.

[0047] The width of the waist line (3-5) constituting the second differential high-frequency line (3) is sufficiently narrow compared to the width of the positive pad (3-7-1) and negative pad (3-7-2) on the bottom side. For example, considering the high speed of the transmitted high-frequency signal, it is important that the width of the pads on the bottom side, excluding the connection pad portion forming the via (the portion indicated by the dashed rectangle), suppresses the capacitive behavior in the connection portion as much as possible. Ideally, to accommodate 200GBd, the width (length in the Y-axis direction) should be at least 200μm or less, and the length (length in the X-axis direction) should be at least 1mm or less. Figure 6 (c) Since the line width on the lower surface of the second substrate limits the connection strength, setting it to less than 100 μm is inappropriate. On the other hand, the width (length in the Y-axis direction) of the waist section of the line on the upper surface has almost no impact on the connection strength, so it is better to be as small as possible to avoid affecting capacitance, but considering the risk of line breakage, it is better to set it to around 50 μm to 100 μm. Figure 6 (b)

[0048] It should be noted that when the vias (3-4) for electrical connections on the upper and lower surfaces of the second substrate are formed as buried vias, the waist-shaped traces are not necessarily required (for example, they can be straight traces), and only the via pads can be formed. By setting them as buried vias, in principle, the solder used for connection will not wet and rise to the upper surface of the pattern, and the wettation will not spread, thus suppressing capacitive behavior, and as a result, suppressing low impedance.

[0049] The connecting portion occupies a very small size within the overall substrate. Therefore, the alignment accuracy between the patterns on the first substrate and the patterns on the second substrate is naturally very important. Therefore, in this embodiment, as... Figure 9 As shown, semi-through holes (3-10-3, 3-10-4) are provided on both sides of the second substrate (in the direction perpendicular to the signal propagation direction) for use with locating pins. Considering the diameter size that ensures sufficient strength and accuracy as a locating pin, and the influence of the semi-through hole on the pattern of the positive line (3-1-1) and negative line (3-1-2) on the second substrate such as a flexible substrate, the radius of curvature of the semi-through hole is preferably set to about 0.3 mm to 0.5 mm. This is because, for example, if the size of the semi-through hole (3-10-3, 3-10-4) becomes too large, it is necessary to cut the ground line (3-1-3, 3-1-4) and the ground plane layer (3-6) of the second substrate, or further, the routing of the positive line (3-1-1) and negative line (3-1-2) pattern will become difficult. By providing locating pins on the first substrate, high-precision alignment can be achieved. Furthermore, for example, semi-through holes (3-10-3, 3-10-4) can also be used for mechanically picking up a second substrate using a device, or for positioning it, thus providing greater versatility. However, when considering connections using solder with a hot bar, conductive adhesive, etc., if the positioning pins are arranged in the same row as the connection part, it will reduce workability, making it impossible to drop the hot bar tool. In this case, it is necessary to be at least 500 μm away from the connection part in the signal propagation direction. Moreover, after connection, the semi-through holes (3-10-3, 3-10-4) can also be connected to the first substrate using solder, conductive adhesive, etc. to strengthen the connection strength. When soldering the semi-through holes (3-10-3, 3-10-4), the areas with a radius of curvature of +100 μm or more on the side surface, upper surface, and lower surface of the semi-through holes (3-10-3, 3-10-4) need to be metallized. Furthermore, when metallization is performed in this area, it is preferable to separate the metallization of the area on the upper and lower surfaces of the semi-through hole from the metallization of the ground line (3-1-3, 3-1-4) and the grounding layer (3-6) of the second substrate as much as possible, from the perspective of the influence on the second differential high-frequency line (3) of the second substrate and the ease of soldering.

[0050] Similarly, from the viewpoint of improving connection strength, by configuring at least one or more semi-through holes (3-10-1, 3-10-2) with a radius of curvature of 0.1 mm or more (the larger the semi-through hole, the more effective it is in improving connection strength) on the edge side (both sides of the second substrate) of the second substrate parallel to the connection portion, and connecting and fixing them to the first substrate, the connection strength can be improved.

[0051] The first differential high-frequency line (2) formed on the first substrate and the second differential high-frequency line (3) formed on the second substrate are permanently electrically connected. Solder is used in this embodiment. The positive pad (2-7-1) formed at the end of the positive line (2-1-1) of the first differential high-frequency line (2) formed on the first substrate and the negative pad (2-7-2) formed at the end of the negative line (2-1-2) are connected to the positive pad (3-7-1) formed at the end of the positive line (3-1-1) of the second differential high-frequency line (3) formed on the second substrate and the negative pad (3-7-2) formed at the end of the negative line (3-1-2) through a bottom solder layer (3-9-3). Figure 4 (b) It should be noted that during the heating of the solder during connection, due to the fluidity of the solder, the solder wets and diffuses into the through-holes (3-4) formed on the second substrate and onto the upper surface of the ends of the second differential high-frequency circuit (3) formed on the second substrate, thus completing the connection with solder (3-9-1) formed in the through-holes and solder (3-9-2) formed on the upper surface respectively. Figure 4 (b)

[0052] In this embodiment, the grounding layer (2-2), which is a conductor layer in the first substrate, located directly below the area where the solder is applied, has a region (2-6) where the conductor layer has been selectively removed. This is a basic configuration introduced to suppress the situation where, when the ends of the first differential high-frequency line (2) formed on the first substrate and the ends of the second differential high-frequency line (3) formed on the second substrate are joined by solder, the size of the conductor in the joining region is larger than before joining, thereby increasing the capacitance and resulting in lower impedance.

[0053] On the other hand, at the ends of the positive line (3-1-1) and negative line (3-1-2) of the second differential high-frequency line (3) formed on the second substrate, the bottom-side conductor layer (positive pad (3-7-1) and negative pad (3-7-2)) is electrically bonded through a through-hole. Furthermore, the second differential high-frequency line (3) has a ground plane layer (3-6) on the bottom-side conductor layer. As described above, to prevent short circuits between the ground plane layer (3-6) and the positive pad (3-7-1) and negative pad (3-7-2), the ground plane layer (3-6) is formed at the board end in a manner that surrounds the positive pad (3-7-1) and negative pad (3-7-2). Thus, between the ground plane layer (3-6) and the positive pad (3-7-1) and negative pad (3-7-2), and... Figure 1 Similarly, existing examples form a prescribed gap ( Figure 6 (c)). At this time, when the positive line (3-1-1) and negative line (3-1-2) constituting the second differential high-frequency line (3) formed on the second substrate approach the end of the board as an extension direction (X-axis direction), they lose their capacitance with the ground plane layer (3-6) in the region of the gap, and the characteristic impedance increases significantly, becoming a high-impedance line. As a result, the high-frequency signal will suffer greater reflection loss, resulting in a deterioration of the frequency band characteristics. In this embodiment, the gap is set to be less than 100 μm, which is sufficiently small compared to 1 / 4 of the length of the tube wavelength equivalent to 100 GHz in the second substrate. Moreover, when the positive line (3-1-1) and negative line (3-1-2) constituting the second differential high-frequency line (3) formed on the second substrate approach the end of the board, their line width is set to a shape (3-2-1) that is wider than the positive line (3-1-1) and negative line (3-1-2), thereby imparting capacitance ( Figure 6 (c)). This can counteract the inductive properties that are the root cause of high impedance characteristics in the gap region below 100 μm. Although a differential high-frequency line is used as an example in this embodiment, a differential high-frequency line generates capacitive coupling between the positive and negative lines in the differential signal, generating electric field lines between the lines. To maintain the distribution shape of the electric field lines between these lines, maintain the coupling mode of the electromagnetic field, and reduce reflections caused by changes in the electromagnetic field mode, the gap between the positive line (3-1-1) and the negative line (3-1-2) is also set to the same feature in the line (3-2-1) which has a shape that widens the width of the aforementioned line.

[0054] Figure 8 The S-parameters and characteristic impedance of the high-frequency connection line of the first embodiment are shown together with the characteristics of the high-frequency connection line of the conventional example. Figure 8 (a) represents the curve trajectory of the reflection loss of the S-parameter. Figure 8 (b) represents the curve trajectory of the S-parameter through loss. Figure 8(c) represents the simulated waveform of the characteristic impedance curve obtained through TDR (time-domain reflectometry). Figure 8 In the diagram, the dashed curve trajectories (4-1, 5-1, 6-1) represent characteristics relevant to the existing examples, while the solid curve trajectories (4-2, 5-2, 6-2) represent characteristics relevant to this embodiment. The simulation model was designed to match a differential impedance of 100Ω. Regarding the reflection loss and transmission loss at the junction of the first differential high-frequency line (2) and the second high-frequency signal line (3), it is clear that this embodiment is superior when the target level values ​​are set to -10dB (10% power reflection) and 1dB (0.2 times power loss), respectively. In fact, the peak characteristic impedance generated in the aforementioned gap region in the existing examples is also improved in the characteristic impedance curve trajectories obtained through TDR.

[0055] (Second Embodiment)

[0056] Reference Figures 10 to 13 The high-frequency connection line (7) of the second embodiment of this disclosure will now be described. The high-frequency connection line (7) is formed by joining the ends of a first differential high-frequency line (2) formed on a first substrate and the ends of a second differential high-frequency line (8) formed on a second substrate. The high-frequency connection line (7) is configured as follows: functionally, a first high-frequency line (7-1) formed on the upper surface of the first substrate is arranged on the left side, a second high-frequency line (7-3) formed on the upper surface of the second substrate is arranged on the right side, and a high-frequency connection line (7-2) is arranged in the center. Figure 13 (b)). This composition is related to Figure 2 The configuration of the conventional high-frequency connection line shown in (b) is the same.

[0057] The first differential high-frequency circuit (2) formed on the first substrate has a group (i.e., a group of circuits) of positive circuit (2-1-1) and negative circuit (2-1-2) on the upper surface of the first substrate, and ground wires (2-1-3, 2-1-4) with ground potential are provided on both sides of the group of circuits. A ground layer (2-2) is provided on the conductor layer directly below the group of circuits, and a bottom ground layer (2-3) is provided on the lowest surface of the first substrate. Ground vias (2-1-5, 2-1-6) are provided to set the potential of all ground layers (2-2) and bottom ground layers (2-3) to ground potential. Insulating layers (2-4, 2-5) are introduced between all conductor layers.

[0058] On the other hand, the second differential high-frequency circuit (8) has a group of positive lines (8-1-1) and negative lines (8-1-2) (a group of positive signal lines and negative signal lines, or simply a group of lines) on the upper surface of the second substrate, as well as positive signal pads and negative signal pads formed at the ends of the group of lines. The positive signal pads and negative signal pads have circular pads (8-3) formed at the ends of the group of lines, through holes (8-4) penetrating the center of the circular pads (8-3), and waist lines (8-5) connecting the circular pads. In addition, ground lines (8-1-3, 8-1-4) with ground potential are provided on both sides of the positive lines (8-1-1) and negative lines (8-1-2). Moreover, the second differential high-frequency circuit (8) has a positive pad (8-7-1), a negative pad (8-7-2), and a ground layer (8-6) formed on the same surface surrounding the positive pads and negative pads on the bottom surface of the second substrate. A portion of the grounding layer (8-6) in the second differential high-frequency line (8), located opposite to the grounding pad formed by a portion of the grounding wires (2-1-3, 2-1-4) in the first differential high-frequency line (2), constitutes a grounding pad. Furthermore, a portion of the upper part of the grounding pad formed by a portion of the grounding layer (8-6) in the grounding wires (8-1-3, 8-1-4) also constitutes a grounding pad. The grounding layer (8-6) is connected to the grounding layers (8-1-3, 8-1-4) via grounding vias (8-1-5, 8-1-6). In addition, an insulating layer (8-8) is introduced between the conductor layer on the upper surface and the conductor layer on the lower surface. The width of the waist line (8-5) is sufficiently narrow compared to the width of the positive pad (8-7-1) and negative pad (8-7-2) on the bottom surface.

[0059] The first differential high-frequency line (2) formed on the first substrate and the second differential high-frequency line (8) formed on the second substrate are permanently electrically connected. Solder is used in this embodiment. The positive pad (2-7-1) formed at the end of the positive line (8-1-1) of the first differential high-frequency line (2) formed on the first substrate and the negative pad (2-7-2) formed at the end of the negative line (2-1-2) are connected to the positive pad (8-7-1) formed at the end of the positive line (8-1-1) of the second differential high-frequency line (8) formed on the second substrate and the negative pad (8-7-2) formed at the end of the negative line (8-1-2) through a bottom solder layer (8-9-3). Figure 10 (b) It should be noted that when the solder is heated during connection, due to the fluidity of the solder, the solder wets and diffuses into the through-holes (8-4) formed on the second substrate and onto the upper surface of the ends of the lines of the second differential high-frequency circuit (8) formed on the second substrate. The connection is completed in a state where solder (8-9-1) is formed in the through-holes and solder (8-9-2) is formed on the upper surface, respectively. Figure 10 (b)

[0060] In this embodiment, the grounding layer (2-2), which is a conductor layer in the first substrate, located directly below the area where the solder is applied, has a region (2-6) where the conductor layer has been selectively removed. This is a basic configuration introduced to suppress the situation where, when the ends of the first differential high-frequency line (2) formed on the first substrate and the ends of the second differential high-frequency line (8) formed on the second substrate are joined by solder, the size of the conductor in the joining region is larger than before joining, thereby increasing the capacitance.

[0061] On the other hand, at the ends of the positive line (8-1-1) and negative line (8-1-2) of the second high-frequency line (3) provided on the second substrate, the conductor layers (positive pad (8-7-1) and negative pad (8-7-2) on the bottom and top surfaces are electrically bonded through through-holes. Furthermore, the second differential high-frequency line (8) has a ground plane layer (8-6) on the bottom surface conductor layer. As described above, to prevent short circuits between the ground plane layer (8-6) and the positive pad (8-7-1) and negative pad (8-7-2), the ground plane layer (8-6) is formed at the board end in a manner that surrounds the positive pad (8-7-1) and negative pad (8-7-2). Thus, a predetermined gap is formed between the ground plane layer (8-6) and the positive pad (8-7-1) and negative pad (8-7-2). Figure 12 (c)). At this time, when the positive line (8-1-1) and negative line (8-1-2) constituting the second differential high-frequency line (8) formed on the second substrate approach the end of the board in the extension direction (X-axis direction), they lose their capacitance with the ground wire in the gap area, and the characteristic impedance increases significantly, becoming a high-impedance line. As a result, the high-frequency signal will suffer greater reflection loss, resulting in a deterioration of the frequency band characteristics. In this embodiment, the gap is set to 100 μm or less, and the line shape (8-2) is as follows: when the positive line (8-1-1) and negative line (8-1-2) constituting the second differential high-frequency line (8) formed on the second substrate approach the end of the board in the extension direction (X-axis direction), its line width is wider than the width of the positive line (8-1-1) and negative line (8-1-2), and larger (wider) than the diameter of the circular pad (8-3) provided on the second substrate. Since this embodiment uses a differential circuit, it features an enhanced capacitance between the positive line (8-1-1) and the negative line (8-1-2) through the circuit shape (8-2) described above. It should be noted that the circuit shape (8-2) described above is designed to have multiple vertices, but is by no means limited to this. The shape can also be curved. By employing the circuit shape (8-2) of this embodiment, the inductance that is the source of high impedance characteristics in the gap region below 100 μm can be further eliminated.

[0062] In the first embodiment, the portion surrounding the positive pad (8-7-1) and negative pad (8-7-2) is a rectangle with two sides parallel to the longitudinal direction of the second high-frequency line and two sides perpendicular to the longitudinal direction of the second high-frequency line. In this embodiment, it is a hexagon. The hexagon has two sides parallel to the longitudinal direction of the second high-frequency line, two sides perpendicular to the longitudinal direction of the second high-frequency line, and two sides connecting the positive line (8-1-1) and negative line (8-1-2) sides of the two sides perpendicular to the longitudinal direction of the second high-frequency line, and the two sides parallel to the longitudinal direction of the second high-frequency line. The interior angles of the positive line (8-1-1) and negative line (8-1-2) sides of the hexagon are obtuse angles. Regarding the shape of the portion surrounding the positive pad (8-7-1) and the negative pad (8-7-2), the two sides of the hexagon in this embodiment that connect the positive line (8-1-1) and the negative line (8-1-2) side of the two sides perpendicular to the long dimension direction of the second high-frequency line and the two sides parallel to the long dimension direction of the second high-frequency line can be set as curves.

[0063] Figure 14 The S-parameters and characteristic impedance of the high-frequency connection line of the second embodiment are presented together with the characteristics of the high-frequency connection line of the conventional embodiment and the characteristics of the high-frequency connection line of the first embodiment. Figure 14 (a) represents the curve trajectory of the reflection loss of the S-parameter. Figure 14 (b) represents the curve trajectory of the S-parameter through loss. Figure 14 (c) represents the simulated waveform of the characteristic impedance curve obtained through TDR (time-domain reflectometry). Figure 14 In the diagram, the dashed curve trajectories (4-1, 5-1, 6-1) represent characteristics related to the existing example, the single-point dashed curve trajectories (4-2, 5-2, 6-2) represent characteristics related to the first embodiment, and the solid curve trajectories (4-3, 5-3, 6-3) represent characteristics related to this embodiment. During simulation, the design was performed to match a differential impedance of 100Ω. In the high-frequency connection line (7) of this embodiment, regarding the reflection loss and transmission loss at the junction of the first high-frequency line (2) and the second high-frequency line (8), with target level values ​​set to -10dB (10% of the power is reflected) and 1dB (0.2 times the power loss), respectively, it can be seen that the reflection loss characteristics are further improved in this embodiment compared to the first embodiment. In fact, in the characteristic impedance curve trajectories obtained by TDR, it can also be seen that the peak characteristic impedance generated by the rigid substrate in the aforementioned gap region in the existing example is further improved.

[0064] (Third Embodiment)

[0065] Reference Figure 15 The high-frequency connection line (9) of the third embodiment of this disclosure will be described. The high-frequency connection line (9) is formed by joining the ends of the first differential high-frequency lines (13-1-1, 13-1-2, 13-2-1, 13-2-2) formed on the first substrate and the ends of the second differential high-frequency lines (14-0-1, 14-0-2) formed on the second substrate. The first differential high-frequency lines (13-1-1, 13-1-2, 13-2-1, 13-2-2) are formed in the first differential high-frequency circuit (10) on the first substrate (e.g., the substrate of IC or LSI). In addition, the second differential high-frequency lines (14-0-1, 14-0-2) are formed on the circuit substrate (11) which is the second substrate.

[0066] The differential high-frequency circuit (10) formed on the first substrate has multiple DC power pads and DC grounding pads (13-3) on the right side of the insulating layer (15) on the upper surface of the first substrate, and differential signal pads (13-2-3 and 13-2-4) and high-frequency grounding pads (13-2-5 and 13-2-6) on the left side of the board end.

[0067] Furthermore, the differential high-frequency circuit (10) has a differential gain circuit (12) and a first differential high-frequency line (13-1-1, 13-1-2, 13-2-1, 13-2-2) electrically connected to the differential gain circuit (12) for high-frequency signal input and output on the insulating layer (15) on the upper surface side of the first substrate. A positive pad (13-1-3) and a negative pad (13-1-4) are formed at the ends of the first differential high-frequency line.

[0068] The circuit board (11), serving as the second substrate, includes a second differential signal pad, a second differential high-frequency line (14-0-1, 14-0-2), and multiple pads (14-2) with through-holes. The multiple pads (14-2) are electrically connected to a DC power supply line and a DC ground line (14-1). The second differential signal pad has the same configuration as in Embodiment 2, and at the ends of the second differential high-frequency lines (14-0-1, 14-0-2), on the upper surface side of the second substrate, it includes a circular pad (8-3), a waist line (8-5) connecting the circular pads, and a line shape (8-2) with a width larger than the diameter of the circular pad (8-3). The circular pad (8-3) is connected via a through-hole (not shown) and a pad (not shown) on the lower surface side to a positive pad (13-1-3) and a negative pad (13-1-4) formed at the ends of the first differential high-frequency line. In addition, ground plane layers (8-1-3, 8-1-4) are provided on both sides of the second differential signal pad. The ground plane layers (8-1-3, 8-1-4) are connected to the ground plane of the first substrate (13-1-5, 13-1-6) via through-holes (not shown) and pads (not shown) on the lower surface side.

[0069] The conductor cross-sectional shape of high-frequency lines on IC / LSI substrates is typically only a few micrometers square. Furthermore, the insulating layer is also known to be formed with a thickness of a few micrometers. For high-frequency lines with such dimensions and shapes, the higher the frequency of the high-frequency signal, the greater the propagation loss, which particularly limits the length of the transmission line in applications requiring 200Gbd. In this embodiment, the high-frequency signal pads and high-frequency ground pads, which handle such high frequencies, are not provided at the board end away from the high-frequency gain circuit (12), but are instead located inside the substrate. Furthermore, a structure is provided that connects to a second differential high-frequency line on a circuit substrate (11), which serves as a second substrate with lower propagation loss. Therefore, the signal level of the high-frequency signal is not degraded, and ICs / LSIs for 200Gbd applications can be implemented more easily.

[0070] Industrial availability

[0071] A high-frequency connection circuit is provided in which the characteristic impedance is matched when the ends of high-frequency lines formed on different substrates are connected to each other in a manner that they abut against each other at the ends of each substrate.

[0072] Explanation of reference numerals in the attached figures:

[0073] 1: High-frequency connection line; 2: Differential high-frequency line; 2-1-1: Positive line (conductor layer); 2-1-2: Negative line (conductor layer); 2-1-3, 2-1-4: Ground (conductor layer); 2-1-5, 2-1-6: Ground via; 2-2: Grounding layer (conductor layer); 2-3: Bottom grounding layer (conductor layer); 2-4, 2-5: Insulating layer; 2-6: Area with conductor layer removed; 2-7-1: Positive pad; 2-7-2: Negative pad; 3: Differential high-frequency line; 3-1-1: Positive line (conductor layer); 3-1-2: Negative line (conductor layer); 3-1-3, 3-1-4: Grounding (conductor layer); 3-1-5, 3-1-6: Ground via; 3-2-1: Wide The shape of the band; 3-3: Circular pad; 3-4: Through hole; 3-5: Waist line; 3-6: Grounding layer (conductor layer); 3-7-1: Positive pad; 3-7-2: Negative pad; 3-8: Insulating layer; 3-9-1: Solder inside the through hole; 3-9-2: Top surface solder; 3-9-3: Bottom surface solder layer; 3-10-1, 3-10-2, 3-10-3, 3-10-4: Semi-through hole; 7: High-frequency connection line; 8: Differential high-frequency line; 8-1-1: Positive line; 8-1-2: Negative line; 8-1-3, 8-1-4: Grounding (conductor layer); 8-1-5, 8-1-6: Grounding via; 8-2: Wide line shape; 8-3: Circular pad; 8-4: Through hole; 8-5 8-6: Grounding layer (conductor layer); 8-7-1: Positive pad; 8-7-2: Negative pad; 8-8: Insulating layer; 8-9-1: Through-hole solder; 8-9-2: Top surface solder; 8-9-3: Bottom surface solder layer; 9: High-frequency connection line; 10: Differential high-frequency circuit; 11: Circuit board; 14-2: Pad; 13-1-1, 13-1-2: Differential high-frequency line; 13-1-3: Positive pad; 13-1-4: Negative pad; 13-1-5, 13-1-6: Ground (conductor layer); 13-2-1, 13-2-2: Differential high-frequency line; 13-2-3, 13-2-4: Differential signal pad; 13-2-5, 13-2-6: High-frequency grounding Ground pad; 13-3: DC power pad, DC ground pad; 14-0-1, 14-0-2: Differential high-frequency circuit; 14-1: DC power line, DC ground line; 14-2: Pad; 15: Insulating layer; 100: Rigid substrate; 101: Signal line; 102: Signal line spacing conversion section; 111: First wiring layer; 112: Second wiring layer; 113: Third wiring layer; 114: First insulating layer; 115: Second insulating layer; 126: Ground opening; 200: Flexible substrate; 201: Signal line; 202: Signal via; 203: Signal line tapered section; 204: Ground via; 210: Ground layer; 211: Ground pad; 212: Signal pad;213: Ground layer tapered section; 221: First wiring layer; 222: Second wiring layer; 223: First insulating layer; 300: Solder.

Claims

1. A high-frequency connection circuit electrically connects a first high-frequency circuit formed on a first insulating substrate and a second high-frequency circuit formed on a second insulating substrate different from the first substrate, wherein, The first high-frequency line has: A first main circuit is formed on the upper surface of the first substrate and has conductivity. The first main circuit has a first signal circuit. A first signal pad is formed on the upper surface of the first substrate and is electrically connected to the end of the first signal line; and The first ground pad is formed on the upper surface of the first substrate. The second high-frequency line has the following features: The second main circuit is formed on the upper surface of the second substrate and is conductive. The second main circuit includes a second signal line and a second ground line formed on the upper surface of the second substrate. The second signal pad is formed on the upper surface of the second substrate and is electrically connected to the end of the second signal line; The second ground pad is formed on the upper surface of the second substrate and is electrically connected to the end of the second ground wire. The third signal pad is formed on the lower surface of the second substrate, directly below the second signal pad. as well as A ground plane is formed on the lower surface of the second substrate in a manner that surrounds the third signal pad, including a third ground pad located directly below the second ground pad on the lower surface of the second substrate. The first signal pad and the third signal pad are opposite each other and bonded. The first ground pad and the third ground pad are opposite each other and bonded together. The gap between the third signal pad and the ground plane in the long dimension of the second high-frequency line is smaller than 1 / 4 of the wavelength inside the tube. The width of the second signal pad in the direction perpendicular to the longitudinal direction of the second high-frequency line is wider than the width of the second signal line in the direction perpendicular to the longitudinal direction of the second high-frequency line, and the spacing between the second signal pad and the second ground pad is narrower than the spacing between the second signal line and the second ground wire.

2. The high-frequency connection line according to claim 1, wherein, The ground plane layer surrounding the third signal pad has any of the following shapes: It includes a rectangle with two sides parallel to the long dimension direction of the second high-frequency line and two sides perpendicular to the long dimension direction of the second high-frequency line. Includes the two parallel sides, the two perpendicular sides, and a hexagonal shape with two sides connecting the second signal line side of the two perpendicular sides to the two parallel sides; or It includes the shape of the two parallel sides, the two perpendicular sides, and the two curves that connect the second signal line side of the two perpendicular sides to the two parallel sides.

3. The high-frequency connection line according to claim 2, wherein, The high-frequency connection line includes at least one signal via made of a conductor that passes through the second substrate for electrically connecting the second signal pad and the third signal pad, the signal via being a conductor-embedded via.

4. The high-frequency connection line according to claim 1, wherein, The high-frequency connection line includes at least one signal via made of conductor that passes through the second substrate for electrically connecting the second signal pad and the third signal pad. The lines connecting the regions of the second signal pad connected to the signal vias have a narrower line shape than the lines connecting the regions of the third signal pad connected to the signal vias.

5. The high-frequency connection line according to claim 4, wherein, The first high-frequency line has a first ground wire formed on the upper surface of the first substrate. The first signal line is a differential signal line in which a first positive signal line and a first negative signal line, which transmit differential signals consisting of pairs of positive and negative signals, are arranged adjacent to each other at a predetermined first interval. A first ground wire is arranged on both sides of the first signal line. The second signal line is a differential signal line in which a second positive signal line and a second negative signal line, which transmit a differential signal consisting of a pair of positive and negative signals, are arranged adjacent to each other at a predetermined second interval different from the first interval. A second ground wire is arranged on both sides of the second signal line. The first positive signal line, the first negative signal line, the second positive signal line, and the second negative signal line are respectively configured to be connected via the second signal pad, the signal via, and the third signal pad.

6. The high-frequency connection line according to claim 4, wherein, The first high-frequency line has a first ground wire formed on the upper surface of the first substrate. The first signal line is a differential signal line in which a first positive signal line and a first negative signal line, which transmit differential signals consisting of pairs of positive and negative signals, are arranged adjacent to each other at a predetermined first interval. A first ground wire is arranged on both sides of the first signal line. The second signal line is a differential signal line in which a second positive signal line and a second negative signal line, which transmit a differential signal consisting of a pair of positive and negative signals, are arranged adjacent to each other at a predetermined second interval different from the first interval. A second ground wire is arranged on both sides of the second signal line. The first positive signal line, the first negative signal line, the second positive signal line, and the second negative signal line are respectively configured to be connected via the second signal pad, the signal via, and the third signal pad. The line in the second signal pad that connects to the second positive signal line has a line shape that is wider than the width of the second signal pad, the width of the third signal pad, and the width of the second main line.

7. The high-frequency connection line according to claim 5 or 6, wherein, The first substrate includes: The first lower surface grounding wire (2-3) is formed on the lower surface of the first substrate at a position directly below the first signal line and the first grounding wire; A grounding wire layer, which is conductive, is formed between the upper surface where the first main line is formed and the grounding wire on the first lower surface. An insulating layer is formed on the upper and lower layers of the grounding wire layer; as well as A ground via is used to electrically connect the ground wire on the first lower surface to the ground wire layer, and to penetrate the first substrate. The grounding layer is not formed in the area directly below the first signal pad.

8. The high-frequency connection line according to claim 5 or 6, wherein, The width of the third signal pad is 100μm to 200μm, the width of the second signal pad is 50μm to 100μm, and the length of the second high-frequency line of the third signal pad corresponding to and bonded to the first signal pad is less than 1mm in the longitudinal direction. The high-frequency connection line also features: A semi-through hole with a radius of curvature of 0.3 mm to 0.5 mm for positioning is formed at a position more than 500 μm away from the third signal pad along the longitudinal direction of the second high-frequency line; and At least one semi-through hole with a radius of curvature of 0.1 mm or more for improving connection strength is formed at a position on the third signal pad that is orthogonal to the longitudinal direction of the second high-frequency line.

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