Multilayer substrate

Abstract

The present invention reduces AC resistance. In a multilayer substrate (100), a ground electrode (4) overlaps an AC signal line (2) in a thickness direction (D1) of a laminated substrate (1). The AC signal line (2) has a plurality of signal lines (21-23) that are separated from each other in the thickness direction (D1) of the laminated substrate (1), and the plurality of signal lines (21-23) are electrically connected by a plurality of connection conductors that penetrate one of a plurality of insulating layers (11-13) in the thickness direction (D1) of the laminated substrate (1). The plurality of signal lines (21-23) include a first signal line (21) adjacent to the ground electrode (4) in the thickness direction (D1) of the laminated substrate (1), and a second signal line (22) adjacent to the first signal line (21) in the thickness direction (D1) of the laminated substrate (1). In the thickness direction (D1) of the laminated substrate (1), a thickness (T21) of the first signal line (21) is greater than a thickness (T22) of the second signal line (22).

Description

multilayer board

[0001] The present invention relates generally to multilayer substrates, and more particularly to multilayer substrates having AC signal lines.

[0002] Patent Document 1 discloses a multilayer board including a laminate (laminated board) and three signal conductors (signal lines).

[0003] The laminate has a structure in which multiple resin layers (insulating layers) are stacked in the stacking direction. Three signal conductors (signal lines) are positioned at different positions in the stacking direction. The three signal conductors are electrically connected. In the multilayer board disclosed in Patent Document 1, high-frequency signals are transmitted to the three signal conductors.

[0004] International Publication No. 2023 / 037852

[0005] The multilayer substrate disclosed in Patent Document 1 may have high AC resistance.

[0006] An object of the present invention is to provide a multilayer substrate capable of reducing AC resistance.

[0007] A multilayer substrate according to one aspect of the present invention includes a laminated substrate, an AC signal line, and a ground electrode. The laminated substrate includes a plurality of insulating layers stacked one on top of the other. The AC signal line is formed on the laminated substrate. The ground electrode is formed on the laminated substrate. The ground electrode overlaps the AC signal line in the thickness direction of the laminated substrate. The AC signal line has a plurality of signal lines spaced apart from one another in the thickness direction of the laminated substrate. In the AC signal line, the signal lines are electrically connected by a plurality of connecting conductors that penetrate one of the insulating layers in the thickness direction of the laminated substrate. The signal lines include a first signal line adjacent to the ground electrode in the thickness direction of the laminated substrate and a second signal line adjacent to the first signal line in the thickness direction of the laminated substrate. In the thickness direction of the laminated substrate, the thickness of the first signal line is greater than the thickness of the second signal line.

[0008] The multilayer substrate according to the above aspect of the present invention can reduce AC resistance.

[0009] FIG. 1 is a plan view of a portion of a multilayer substrate according to a first embodiment. FIG. 2 is a cross-sectional view of the multilayer substrate taken along line II-II in FIG. 1 . FIG. 3 is a cross-sectional view of the multilayer substrate taken along line III-III in FIG. 1 . FIG. 4 is a cross-sectional view of a multilayer substrate according to a second embodiment. FIG. 5 is a cross-sectional view of a multilayer substrate according to a third embodiment. FIG. 6 is a cross-sectional view of a multilayer substrate according to a fourth embodiment. FIG. 7 is a plan view of a portion of a multilayer substrate according to a fifth embodiment. FIG. 8 is a see-through plan view of a portion of the multilayer substrate taken along line IX-IX in FIG. 7 . FIG. 10 is a cross-sectional view of a multilayer substrate according to a sixth embodiment. FIG. 11 is a cross-sectional view of a multilayer substrate according to a seventh embodiment. FIG. 12 is a cross-sectional view of a multilayer substrate according to an eighth embodiment. FIG. 13 is a cross-sectional view of a multilayer substrate according to a ninth embodiment. FIG. 14 is a cross-sectional view of a multilayer substrate according to a tenth embodiment. FIG. 15 is a cross-sectional view of a multilayer substrate according to an eleventh embodiment. FIG. 16 is a cross-sectional view of a multilayer substrate according to a twelfth embodiment. FIG. 17 is a cross-sectional view of a portion of a multilayer substrate according to a thirteenth embodiment.

[0010] Hereinafter, embodiments 1 to 13 will be described with reference to the drawings. The drawings referred to in the following embodiments 1 to 13 are schematic diagrams, and the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensions, and the size ratios and thickness ratios between the components do not necessarily reflect the actual dimensional ratios.

[0011] First Embodiment A multilayer substrate 100 according to a first embodiment will be described with reference to FIGS.

[0012] (1) Configuration of Multilayer Substrate As shown in FIGS. 1 to 3, the multilayer substrate 100 according to the first embodiment includes a multilayer substrate 1, an AC signal line 2, and a ground electrode 4.

[0013] 1 to 3, a Cartesian coordinate system is defined having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis, which is the axis along the thickness direction D1 of the multilayer substrate 1 (see FIG. 2), is indicated as the Z-axis. The X-axis, the Y-axis, and the Z-axis are all imaginary axes, and the arrows indicating "X," "Y," and "Z" in the drawings are merely indicated for the purpose of explanation and do not have any physical substance. The multilayer substrate 100 is, for example, a flexible substrate. In the example of FIG. 1, the thickness direction D1 of the multilayer substrate 100 is the direction along the Z-axis, but if the multilayer substrate 100 is bent, this direction may differ depending on the position on the multilayer substrate 100.

[0014] The multilayer substrate 100 is housed in, for example, the housing of an electronic device. The electronic device is, for example, a communication device. The communication device is, for example, a mobile phone (e.g., a smartphone), but is not limited to a mobile phone and may be, for example, a notebook personal computer, a wearable device (e.g., a smart watch), etc.

[0015] (1.1) Laminated Substrate As shown in Figures 2 and 3, the laminated substrate 1 has a plurality of insulating layers 11, 12, and 13 (three in the example of Figures 2 and 3), and the plurality of insulating layers 11, 12, and 13 are stacked. The thickness direction D1 of the laminated substrate 1 is the stacking direction of the plurality of insulating layers 11, 12, and 13. Hereinafter, for convenience of explanation, the insulating layer 11, the insulating layer 12, and the insulating layer 13 may also be referred to as the first insulating layer 11, the second insulating layer 12, and the third insulating layer 13, respectively.

[0016] In the laminated substrate 1, a first insulating layer 11, a second insulating layer 12, and a third insulating layer 13 are laminated in this order.

[0017] The material of each of the multiple insulating layers 11, 12, and 13 includes, for example, a thermoplastic resin. The thermoplastic resin is, for example, a liquid crystal polymer. The thermoplastic resin is not limited to a liquid crystal polymer, and may be, for example, PTFE (polytetrafluoroethylene). In this embodiment, the first insulating layer 11 and the second insulating layer 12 are self-adhered, and no adhesive layer is interposed between the first insulating layer 11 and the second insulating layer 12. Also, in this embodiment, the second insulating layer 12 and the third insulating layer 13 are self-adhered, and no adhesive layer is interposed between the second insulating layer 12 and the third insulating layer 13.

[0018] The thickness of each of the insulating layers 11, 12, and 13 is, for example, not less than 10 μm and not more than 120 μm.

[0019] In this embodiment, the laminated substrate 1 has an elongated shape in which the length along the Y axis is longer than the length along the X axis when viewed from above in the thickness direction D1 of the laminated substrate 1. When viewed from above in the thickness direction D1 of the laminated substrate 1, the laminated substrate 1 may have a shape other than an elongated shape.

[0020] (1.2) AC Signal Line As shown in FIG. 1 , the AC signal line 2 is formed on the laminate substrate 1. The AC signal line 2 is a line through which a signal is transmitted. In the present disclosure, the AC signal line 2 is a line through which a signal whose magnitude changes over time is transmitted. The AC signal line 2 is, for example, an NFC (near field communication) signal line. In this embodiment, the signal transmitted through the AC signal line 2 is, for example, an AC signal having a frequency of 13.56 MHz.

[0021] 2 and 3 , the AC signal line 2 has a plurality of signal lines (signal electrodes) 21, 22, and 23 that are spaced apart from one another in the thickness direction D1 of the laminated substrate 1. In a plan view of the laminated substrate 1 in the thickness direction D1, the signal lines 21, 22, and 23 overlap one another.

[0022] Each of the signal lines 21 to 23 has electrical conductivity and is made of a material that includes, for example, copper.

[0023] The signal line 21 is laminated on the first insulating layer 11. The signal line 22 is laminated on the second insulating layer 12. The signal line 23 is laminated on the third insulating layer 13. In the multilayer substrate 100, the ground electrode 4, the first insulating layer 11, the signal line 21, the second insulating layer 12, the signal line 22, the third insulating layer 13, and the signal line 23 are laminated in the following order: ground electrode 4, first insulating layer 11, the signal line 21, the second insulating layer 12, the signal line 22, the third insulating layer 13, and the signal line 23. Hereinafter, for convenience of explanation, the signal line 21 and the signal line 22 may also be referred to as the first signal line 21 and the second signal line 22, respectively. The multiple signal lines 21 to 23 include the first signal line 21 adjacent to the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 and the second signal line 22 adjacent to the first signal line 21 in the thickness direction D1 of the laminated substrate 1.

[0024] Each of the multiple signal lines 21 to 23 is formed in a predetermined pattern. In this embodiment, each of the multiple signal lines 21 to 23 is linear when viewed from above in the thickness direction D1 of the laminated substrate 1. When viewed from above in the thickness direction D1 of the laminated substrate 1, each of the multiple signal lines 21 to 23 may have a shape other than linear. The first signal line 21 is formed, for example, by patterning a copper foil (hereinafter also referred to as a first copper foil) attached to the first insulating layer 11. The second signal line 22 is formed, for example, by patterning a copper foil (hereinafter also referred to as a second copper foil) attached to the second insulating layer 12. The signal line 23 is formed, for example, by patterning a copper foil (hereinafter also referred to as a third copper foil) attached to the third insulating layer 13. The ground electrode 4 is formed, for example, by patterning a copper foil (hereinafter also referred to as a fourth copper foil) attached to a second main surface opposite to the first main surface, which is the main surface to which the first copper foil is attached, of the first insulating layer 11. The laminate including the ground electrode 4, the first insulating layer 11, and the first signal line 21 may be formed by laminating two single-sided copper-clad films.

[0025] The signal lines 21, 22, and 23 have line widths W21, W22, and W23, respectively. In this embodiment, the line width W21 of the first signal line 21, the line width W22 of the second signal line 22, and the line width W23 of the signal line 23 are the same. In the multilayer substrate 100, from the viewpoint of increasing the cross-sectional area of ​​the AC signal line 2, it is preferable that the line widths W21 to W23 are the same, and that the line width is wider, but the line widths W21 to W23 may be different from one another. The "cross-sectional area of ​​the AC signal line 2" refers to the total cross-sectional area of ​​the multiple signal lines 21 to 23 in any one cross section perpendicular to the longitudinal direction of the AC signal line 2.

[0026] The thickness of each of the signal lines 21 to 23 is thinner than the thickness of each of the insulating layers 11 to 13. The thicknesses T21, T22, and T23 of the signal lines 21, 22, and 23 will be described in the section "(2) Thickness of each of the signal lines and the thickness of the ground electrode."

[0027] The AC signal line 2 also has a plurality of connecting conductors that electrically connect the plurality of signal lines 21 to 23. Each of the plurality of connecting conductors is an interlayer connecting conductor that connects signal lines formed in two different insulating layers among the plurality of insulating layers 11 to 13. Each of the plurality of connecting conductors is conductive. In the AC signal line 2, the plurality of signal lines 21 to 23 are electrically connected by a plurality of connecting conductors that penetrate one of the plurality of insulating layers 11 to 13 in the thickness direction D1 of the laminated substrate 1. The plurality of connecting conductors include a plurality of first connecting conductors 32 that penetrate the second insulating layer 12 and a plurality of second connecting conductors 33 that penetrate the third insulating layer 13.

[0028] In this embodiment, the multiple first connecting conductors 32 and the multiple second connecting conductors 33 correspond one-to-one to each other, and corresponding first connecting conductors 32 and second connecting conductors 33 overlap in the thickness direction D1 of the laminated substrate 1. In the AC signal line 2, the first connecting conductors 32 and the second connecting conductors 33 may be arranged with a shift in the signal transmission direction (the Y-axis direction in the examples of FIGS. 2 and 3 ).

[0029] In this embodiment, the multiple first connecting conductors 32 are interposed between the first signal line 21 and the second signal line 22 in the thickness direction D1 of the laminated substrate 1. The multiple first connecting conductors 32 are arranged in two rows, and the first connecting conductors 32 in each row are arranged at a distance from each other in the longitudinal direction of the second signal line 22. The longitudinal direction of the second signal line 22 is a direction along the second signal line 22, a direction perpendicular to the width direction (line width direction) of the second signal line 22, and is the direction in which a signal is transmitted in the second signal line 22.

[0030] Furthermore, the plurality of second connection conductors 33 are interposed between the second signal line 22 and the signal line 23 in the thickness direction D1 of the laminated substrate 1. The plurality of second connection conductors 33 are arranged in two rows, and the second connection conductors 33 in each row are arranged at a distance in the longitudinal direction of the signal line 23. The longitudinal direction of the signal line 23 is a direction along the signal line 23, a direction perpendicular to the width direction (line width direction) of the signal line 23, and is the direction in which a signal is transmitted in the signal line 23. In this embodiment, the first signal line 21 and the second signal line 22 are electrically connected by the plurality of first connection conductors 32, and the second signal line 22 and the signal line 23 are electrically connected by the plurality of second connection conductors 33.

[0031] Each of the plurality of first connecting conductors 32 and the plurality of second connecting conductors 33 is electrically conductive. Each of the plurality of first connecting conductors 32 and the plurality of second connecting conductors 33 includes, for example, copper, a copper-tin alloy, and a resin. The plurality of first connecting conductors 32 are formed, for example, by filling a plurality of via holes formed in the second insulating layer 12 with a conductive paste including copper, a low-melting-point metal (for example, tin), and a resin, and heating the via holes, with each via hole being blocked by a portion of the second copper foil. The plurality of second connecting conductors 33 are formed, for example, by filling a plurality of via holes formed in the third insulating layer 13 with a conductive paste including copper, a low-melting-point metal (for example, tin), and a resin, and heating the via holes, with each via hole being blocked by a portion of the third copper foil.

[0032] 2 and 3, the ground electrode 4 is formed on the laminated substrate 1. The ground electrode 4 overlaps the multiple signal lines 21 to 23 in a plan view in the thickness direction D1 of the laminated substrate 1.

[0033] The ground electrode 4 is adjacent to the first signal line 21 of the multiple signal lines 21 to 23 in the thickness direction D1 of the laminated substrate 1. "The ground electrode 4 is adjacent to the first signal line 21 of the multiple signal lines 21 to 23 in the thickness direction D1 of the laminated substrate 1" means that the ground electrode 4 and the first signal line 21 are arranged apart from each other in the thickness direction of the laminated substrate 1, with no other signal lines 22, 23 being arranged between them.

[0034] The ground electrode 4 is laminated on the surface of the first insulating layer 11 opposite to the surface on which the first signal line 21 is laminated. The ground electrode 4 is located on a main surface 101 (hereinafter also referred to as the first main surface 101) of the laminated substrate 1. The first main surface 101 of the laminated substrate 1 is the main surface opposite to a second main surface 102 of the laminated substrate 1 on which the signal line 23 is laminated.

[0035] The ground electrode 4 is electrically conductive and is made of a material that includes, for example, copper.

[0036] The ground electrode 4 is formed in a predetermined pattern. In this embodiment, the ground electrode 4 is linear when viewed from above in the thickness direction D1 of the laminated substrate 1. However, the ground electrode 4 may have a shape other than linear when viewed from above in the thickness direction D1 of the laminated substrate 1.

[0037] In this embodiment, the ground electrode 4 is formed, for example, by patterning a fourth copper foil attached to the first insulating layer 11. In the width direction of the first signal line 21, the width W4 of the ground electrode 4 is the same as the line width W21 of the first signal line 21.

[0038] (2) Thickness of Each of the Multiple Signal Wires and Thickness of the Ground Electrode The thickness of each of the multiple signal wires 21 to 23 is, for example, 3 μm or more and 40 μm or less. In this embodiment, from the viewpoint of reducing bias in current density in the width direction of the AC signal line 2 due to the proximity effect and thereby reducing AC resistance, the thickness T21 of the first signal wire 21 is preferably more than 1 time and not more than 5 times the thickness T22 of the second signal wire 22. More preferably, the thickness T21 of the first signal wire 21 is more than 1 time and not more than 2 times the thickness T22 of the second signal wire 22.

[0039] In this embodiment, as an example, the thickness T21 of the first signal line 21, the thickness T22 of the second signal line 22, and the thickness T23 of the signal line 23 are 18 μm, 12 μm, and 12 μm, respectively. In this embodiment, the thickness T23 of the signal line 23 is the same as the thickness T22 of the second signal line 22, but may be different from the thickness T22 of the second signal line 22.

[0040] In this embodiment, the thickness T4 of the ground electrode 4 is thinner than the thickness T21 of the first signal line 21. In this embodiment, the thickness T4 of the ground electrode 4 is, for example, the same as the thickness T22 of the second signal line 22, but may be different from the thickness T22 of the second signal line 22.

[0041] (3) Characteristics of the Multilayer Substrate The multilayer substrate 100 of the present embodiment can reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100, compared to a multilayer substrate including an AC signal line having multiple signal lines with the same thickness.

[0042] In the multilayer substrate 100 of this embodiment, for example, when the thickness T21 of the first signal line 21, the thickness T22 of the second signal line 22, and the thickness T23 of the signal line 23 are 18 μm, 12 μm, and 12 μm, respectively, the AC resistance can be reduced compared to a multilayer substrate having an AC signal line including multiple signal lines each having a thickness of 14 μm.

[0043] (4) Manufacturing Method of Multilayer Board In the manufacturing method of the multilayer board 100 of this embodiment, for example, a single-sided copper-clad film on which the ground electrode 4 is formed, a single-sided copper-clad film on which the first signal line 21 is formed, a single-sided copper-clad film in which a conductive paste is filled in each of a plurality of via holes blocked by the second signal line 22 patterned on one surface of the second insulating layer 12, and a single-sided copper-clad film in which a conductive paste is filled in each of a plurality of via holes blocked by the signal line 23 patterned on one surface of the third insulating layer 13 are placed on a metal plate (not shown), and pressed from above while being heated, to form the multilayer board 100.

[0044] (5) Effects In the multilayer substrate 100 according to the first embodiment, the ground electrode 4 overlaps the AC signal line 2 in the thickness direction D1 of the laminated substrate 1. The AC signal line 2 has multiple signal lines 21 to 23 that are spaced apart from one another in the thickness direction D1 of the laminated substrate 1, and the multiple signal lines 21 to 23 are electrically connected by multiple connection conductors that penetrate one of the multiple insulating layers 11 to 13 in the thickness direction D1 of the laminated substrate 1. The multiple signal lines 21 to 23 include a first signal line 21 adjacent to the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 and a second signal line 22 adjacent to the first signal line 21 in the thickness direction D1 of the laminated substrate 1. In the thickness direction D1 of the laminated substrate 1, the thickness T21 of the first signal line 21 is greater than the thickness T22 of the second signal line 22.

[0045] The above configuration makes it possible to reduce the AC resistance of the multilayer substrate 100. More specifically, the multilayer substrate 100 according to the first embodiment can reduce bias in the widthwise current distribution of the first signal line 21, which is adjacent to the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 among the multiple signal lines 21 to 23 spaced apart in the thickness direction D1 of the laminated substrate 1, thereby improving the current distribution of the first signal line 21 (making the current distribution of the first signal line 21 more uniform). Thus, the above configuration makes it possible to more efficiently pass current by thickening the first signal line 21, which can improve the current distribution, thereby reducing the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100.

[0046] Furthermore, in the multilayer substrate 100 according to the first embodiment, the ground electrode 4 overlaps the entire widthwise area of ​​the first signal line 21 in the thickness direction D1 of the multilayer substrate 1 .

[0047] According to the above configuration, it is possible to improve noise resistance.

[0048] (Embodiment 2) A multilayer substrate 100A according to embodiment 2 will be described with reference to Fig. 4. With regard to the multilayer substrate 100A according to embodiment 2, components that are the same as those in the multilayer substrate 100 according to embodiment 1 (see Figs. 1 to 3) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 4, as in Figs. 1 to 3, Cartesian coordinates having three mutually orthogonal axes, namely, an X-axis, a Y-axis, and a Z-axis, are defined and expressed.

[0049] (1) Configuration The multilayer substrate 100A according to the second embodiment differs from the multilayer substrate 100 according to the first embodiment in that it further includes an insulating layer 14 (hereinafter also referred to as a fourth insulating layer 14). In this embodiment, the fourth insulating layer 14 is located between the third insulating layer 13 and the first insulating layer 11 in the thickness direction D1 of the laminated substrate 1. The material of the fourth insulating layer 14 is the same as the material of the first insulating layer 11, the second insulating layer 12, and the third insulating layer 13. In the multilayer substrate 100A according to the second embodiment, the AC signal line 2 further includes two signal lines 24 (hereinafter also referred to as third signal lines 24) adjacent to the ground electrode 4 in the width direction of the first signal line 21. In the thickness direction D1 of the laminated substrate 1, the two third signal lines 24 overlap the first signal line 21 and are separated from the first signal line 21. The two third signal lines 24 are formed on the main surface of the fourth insulating layer 14 facing the first insulating layer 11. The material of the two third signal lines 24 is the same as the material of the ground electrode 4. In the multilayer substrate 100A according to the second embodiment, as shown in Fig. 4 , in the thickness direction D1 of the multilayer substrate 1, the signal line 23, the third insulating layer 13, the fourth insulating layer 14, the ground electrode 4, the first insulating layer 11, the first signal line 21, the second insulating layer 12, and the second signal line 22 are arranged in this order: the signal line 23, the third insulating layer 13, the fourth insulating layer 14, the ground electrode 4, the first insulating layer 11, the first signal line 21, the second insulating layer 12, and the second signal line 22. Furthermore, in the multilayer substrate 100A, in the thickness direction D1 of the laminated substrate 1, the signal line 23, the third insulating layer 13, the fourth insulating layer 14, the third signal line 24, the first insulating layer 11, the first signal line 21, the second insulating layer 12, and the second signal line 22 are arranged in the following order: signal line 23, the third insulating layer 13, the fourth insulating layer 14, the third signal line 24, the first insulating layer 11, the first signal line 21, the second insulating layer 12, and the second signal line 22.

[0050] In the second embodiment, the plurality of connecting conductors electrically connecting the plurality of signal lines 21 to 24 in the AC signal line 2 include a plurality of first connecting conductors 32 penetrating the second insulating layer 12, a plurality of second connecting conductors 33 penetrating the third insulating layer 13, a plurality of third connecting conductors 31 penetrating the first insulating layer 11, and a plurality of fourth connecting conductors 34 penetrating the fourth insulating layer 14.

[0051] In this embodiment, the multiple second connecting conductors 33 and the multiple fourth connecting conductors 34 correspond one-to-one, and corresponding second connecting conductors 33 and fourth connecting conductors 34 overlap in the thickness direction D1 of the laminated substrate 1. Furthermore, in this embodiment, the first connecting conductor 32, the third connecting conductor 31, and the second connecting conductor 33 overlap in the thickness direction D1 of the laminated substrate 1, but the first connecting conductor 32, the third connecting conductor 31, and the second connecting conductor 33 may be arranged with a shift in the signal transmission direction (the Y-axis direction in the example of FIG. 4 ).

[0052] In this embodiment, the multiple first connecting conductors 32 are interposed between the first signal line 21 and the second signal line 22 in the thickness direction D1 of the laminated substrate 1. The multiple first connecting conductors 32 are arranged in two rows, and the first connecting conductors 32 in each row are arranged at a distance from each other in the longitudinal direction of the second signal line 22. The longitudinal direction of the second signal line 22 is a direction along the second signal line 22, a direction perpendicular to the width direction (line width direction) of the second signal line 22, and is the direction in which a signal is transmitted in the second signal line 22.

[0053] In the multilayer substrate 100A, a plurality of third connecting conductors 31 are interposed between the first signal line 21 and two signal lines 24 in the thickness direction D1 of the laminated substrate 1. The plurality of third connecting conductors 31 are arranged in two rows, and the third connecting conductors 31 in each row are spaced apart in the longitudinal direction of the first signal line 21. The longitudinal direction of the first signal line 21 is a direction along the first signal line 21, a direction perpendicular to the width direction (line width direction) of the first signal line 21, and is the direction in which a signal is transmitted in the first signal line 21. In the multilayer substrate 100A, a plurality of fourth connecting conductors 34 connected to the signal line 24 and a plurality of second connecting conductors 33 corresponding one-to-one to the plurality of fourth connecting conductors 34 are interposed between the signal line 24 and the signal line 23 in the thickness direction D1 of the laminated substrate 1. The plurality of fourth connecting conductors 34 are arranged in two rows, and the fourth connecting conductors 34 in each row are spaced apart in the longitudinal direction of the signal line 24. The length direction of the signal line 24 is a direction along the signal line 24, a direction perpendicular to the width direction (line width direction) of the signal line 24, and a direction in which a signal is transmitted in the signal line 24. The multiple second connection conductors 33 are arranged in two rows, and the second connection conductors 33 in each row are arranged spaced apart in the length direction of the signal line 24. The length direction of the signal line 23 is a direction along the signal line 23, a direction perpendicular to the width direction (line width direction) of the signal line 23, and a direction in which a signal is transmitted in the signal line 23. In this embodiment, the first signal line 21 and the second signal line 22 are electrically connected by multiple first connection conductors 32. In this embodiment, the first signal line 21 and the two signal lines 24 are electrically connected by multiple third connection conductors 31. In this embodiment, the two signal lines 24 and the signal line 23 are electrically connected by multiple fourth connection conductors 34 and multiple second connection conductors 33.

[0054] In the second embodiment, the thickness T23 of the signal line 23 is thicker than the thickness T22 of the second signal line 22 and the thickness T24 of the signal line 24 in the thickness direction D1 of the laminated substrate 1. In the second embodiment, as an example, the thickness T21 of the first signal line 21, the thickness T22 of the second signal line 22, the thickness T23 of the signal line 23, and the thickness T24 of the signal line 24 are 18 μm, 12 μm, 18 μm, and 12 μm, respectively. In the second embodiment, the thickness T23 of the signal line 23 is the same as the thickness T21 of the first signal line 21, but may be different from the thickness T21 of the first signal line 21.

[0055] (2) Effect In the multilayer substrate 100A according to the second embodiment, the thickness T21 of the first signal line 21 and the thickness T23 of the signal line 23 are each thicker than the thickness T22 of the second signal line 22 in the thickness direction D1 of the multilayer substrate 1, and therefore, it is possible to further reduce the AC resistance.

[0056] (Embodiment 3) A multilayer substrate 100B according to embodiment 3 will be described with reference to Fig. 5. With regard to the multilayer substrate 100B according to embodiment 3, components that are the same as those of the multilayer substrate 100 according to embodiment 1 (see Figs. 1 to 3) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 5, as in Figs. 1 to 3, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 is represented as the Z-axis.

[0057] (1) Configuration The multilayer substrate 100B according to the third embodiment differs from the multilayer substrate 100 according to the first embodiment in that it further includes an insulating layer 14 (hereinafter also referred to as a fourth insulating layer 14). In this embodiment, the fourth insulating layer 14 is located on the side of the first insulating layer 11 opposite the second insulating layer 12 in the thickness direction D1 of the laminated substrate 1. The material of the fourth insulating layer 14 is the same as the material of the first insulating layer 11, the second insulating layer 12, and the third insulating layer 13. In the multilayer substrate 100B according to the third embodiment, the ground electrode 4 is formed on the main surface of the fourth insulating layer 14 opposite the first insulating layer 11. In the multilayer substrate 100B according to the third embodiment, the ground electrode 4 overlaps with more than half of the width of the first signal line 21 in the thickness direction D1 of the laminated substrate 1. In the width direction of the first signal line 21, the overlapping amount between the ground electrode 4 and the first signal line 21 is equal to or greater than half the line width W21 of the first signal line 21 but is less than the line width W21 of the first signal line 21. The ground electrode 4 is arranged so as to overlap the first edge of the first and second widthwise edges of the first signal line 21 in a plan view from the thickness direction D1 of the laminated substrate 1. However, the ground electrode 4 may be arranged so as not to overlap either the first or second widthwise edges of the first signal line 21 between the first and second widthwise edges. Note that in this embodiment, the width W4 of the ground electrode 4 in the width direction of the first signal line 21 is shorter than the line width W21 of the first signal line 21.

[0058] Furthermore, in the multilayer substrate 100B, the AC signal line 2 further includes a signal line 24 (hereinafter also referred to as a third signal line 24) adjacent to the ground electrode 4 in the width direction of the first signal line 21. In the thickness direction D1 of the laminated substrate 1, the third signal line 24 overlaps with the first signal line 21 and is spaced apart from the first signal line 21. That is, in this embodiment, the AC signal line 2 includes multiple signal lines 21 to 24 that are spaced apart from one another in the thickness direction of the laminated substrate 1. In the third embodiment, the multiple connection conductors electrically connecting the multiple signal lines 21 to 24 in the AC signal line 2 include multiple first connection conductors 32 penetrating the second insulating layer 12, multiple third connection conductors 31 penetrating the first insulating layer 11, multiple fourth connection conductors 34 penetrating the fourth insulating layer 14, and multiple second connection conductors 33 penetrating the third insulating layer 13. In this embodiment, the plurality of second connecting conductors 33 and the plurality of fourth connecting conductors 34 correspond one-to-one, and corresponding second connecting conductors 33 and fourth connecting conductors 34 overlap in the thickness direction D1 of the laminated substrate 1. Furthermore, in this embodiment, the first connecting conductor 32, the third connecting conductor 31, and the fourth connecting conductor 34 overlap in the thickness direction D1 of the laminated substrate 1, but the first connecting conductor 32, the third connecting conductor 31, and the fourth connecting conductor 34 may be arranged with a shift in the signal transmission direction (the Y-axis direction in the example of FIG. 5 ).

[0059] The third signal line 24 is formed on the principal surface of the fourth insulating layer 14 opposite the first insulating layer 11. Therefore, in the present embodiment, the third signal line 24 and the ground electrode 4 are formed on the principal surface of the fourth insulating layer 14 opposite the first insulating layer 11. In the thickness direction D1 of the laminated substrate 1, the thickness T24 of the third signal line 24 is the same as the thickness T4 of the ground electrode 4. In the third embodiment, the thickness T4 of the ground electrode 4 and the thickness T24 of the third signal line 24 are each the same as the thickness T22 of the second signal line 22. In the third embodiment, as an example, the thickness T21 of the first signal line 21, the thickness T22 of the second signal line 22, the thickness T23 of the signal line 23, the thickness T4 of the ground electrode 4, and the thickness T24 of the third signal line 24 are 18 μm, 12 μm, 12 μm, 12 μm, and 12 μm, respectively.

[0060] The width W24 of the third signal line 24 adjacent to the ground electrode 4 in the width direction of the first signal line 21 is narrower than the width W4 of the ground electrode 4. From the viewpoint of reducing the AC resistance of the AC signal line 2, it is preferable that the width W24 of the third signal line 24 be wider.

[0061] (2) Effects In the multilayer substrate 100B according to the third embodiment, similar to the multilayer substrate 100 according to the first embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the multilayer substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100B.

[0062] In the multilayer substrate 100B according to the third embodiment, the AC signal line 2 further includes a third signal line 24 that is adjacent to the ground electrode 4 in the width direction of the first signal line 21 .

[0063] According to the above configuration, the cross-sectional area of ​​the AC signal line 2 can be increased, and the AC resistance of the AC signal line 2 can be further reduced.

[0064] (Embodiment 4) A multilayer substrate 100C according to embodiment 4 will be described with reference to Fig. 6. Regarding the multilayer substrate 100C according to embodiment 4, components similar to those of the multilayer substrate 100B according to embodiment 3 (see Fig. 5) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 6, as in Fig. 5, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 is represented as the Z-axis.

[0065] (1) Configuration The multilayer substrate 100C according to the fourth embodiment differs from the multilayer substrate 100B according to the third embodiment in that the thickness T4 of the ground electrode 4 and the thickness T24 of the third signal line 24 are thicker than the thickness T22 of the second signal line 22. In the fourth embodiment, as an example, the thickness T21 of the first signal line 21, the thickness T22 of the second signal line 22, the thickness T23 of the signal line 23, the thickness T4 of the ground electrode 4, and the thickness T24 of the third signal line 24 are 18 μm, 12 μm, 12 μm, 18 μm, and 18 μm, respectively.

[0066] In the fourth embodiment, the thickness T4 of the ground electrode 4 and the thickness T24 of the third signal line 24 are each the same as the thickness T21 of the first signal line 21, but may be different from the thickness T21 of the first signal line 21.

[0067] (2) Effect In the multilayer substrate 100C according to the fourth embodiment, the thickness T4 of the ground electrode 4 and the thickness T24 of the third signal line 24 are thicker than the thickness T22 of the second signal line 22 in the thickness direction D1 of the multilayer substrate 1.

[0068] According to the above configuration, the thickness T21 of the first signal line 21 adjacent to the ground electrode 4 in the thickness direction D1 of the multilayer substrate 1 and the thickness T24 of the third signal line 24 adjacent to the ground electrode 4 in the width direction of the ground electrode 4 are thicker than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100C.

[0069] Fifth Embodiment A multilayer substrate 100D according to a fifth embodiment will be described with reference to Figures 7 to 9. Regarding the multilayer substrate 100D according to the fifth embodiment, the same components as those of the multilayer substrate 100 according to the first embodiment (see Figures 1 to 3) are denoted by the same reference numerals, and description thereof will be omitted. In each of Figures 7 to 9, as in Figures 1 to 3, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis, is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 (see Figure 9) is indicated as the Z-axis.

[0070] 9 , the multilayer substrate 100D according to the fifth embodiment differs from the multilayer substrate 100 according to the first embodiment in that it further includes an RF signal line 6, a second ground electrode 40, and a third ground electrode 43. Note that the width of the multilayer substrate 100D in the width direction of the first signal line 21 is wider than the width of the multilayer substrate 100.

[0071] In the present embodiment, the RF signal line 6 is linear as shown in FIG. 8 when viewed from above in the thickness direction D1 of the laminated substrate 1. The RF signal line 6 is formed on the laminated substrate 1. The second ground electrode 40 is formed on the laminated substrate 1 as shown in FIG. 9. The second ground electrode 40 faces the RF signal line 6 in the thickness direction D1 of the laminated substrate 1 via one insulating layer 11 among the insulating layers 11 to 13, and is different from the first ground electrode 4, which is the ground electrode 4. The third ground electrode 43 is formed on the laminated substrate 1. The third ground electrode 43 faces the RF signal line 6 in the thickness direction D1 of the laminated substrate 1 via insulating layers 12 and 13, which are different from the insulating layer 11, among the insulating layers 11 to 13. In the present embodiment, the third ground electrode 43 is linear as shown in FIG. 7 when viewed from above in the thickness direction D1 of the laminated substrate 1. When viewed from above in the thickness direction D1 of the laminated substrate 1, the RF signal line 6 and the third ground electrode 43 may each have a shape other than a linear shape.

[0072] 9 , the multilayer substrate 100D further includes a fourth ground electrode 41 and a fifth ground electrode 42. In the multilayer substrate 100D, the second ground electrode 40, the fourth ground electrode 41, the fifth ground electrode 42, and the third ground electrode 43 are arranged in the following order in the thickness direction D1 of the multilayer substrate 1. In the thickness direction D1 of the multilayer substrate 1, the second ground electrode 40, the fourth ground electrode 41, the fifth ground electrode 42, and the third ground electrode 43 are spaced apart from one another. In the multilayer substrate 100D, the fourth ground electrode 41 is divided into two split ground electrodes 411 and 412 in the width direction of the first signal line 21. In the multilayer substrate 100D, the fifth ground electrode 42 is divided into two split ground electrodes 421 and 422 in the width direction of the second signal line 22.

[0073] In the present embodiment, the first signal line 21 and the RF signal line 6 are aligned in the width direction of the first signal line 21. More specifically, in the present embodiment, the first signal line 21, the split ground electrode 411, the RF signal line 6, and the split ground electrode 412 are aligned in the width direction of the first signal line 21 in the following order: first signal line 21, split ground electrode 411, RF signal line 6, and split ground electrode 412. In the width direction of the first signal line 21, the first signal line 21, the split ground electrode 411, the RF signal line 6, and the split ground electrode 412 are spaced apart from one another. In the present embodiment, the first signal line 21, the split ground electrode 411, the RF signal line 6, and the split ground electrode 412 are formed, for example, by patterning a first copper foil attached to the first insulating layer 11.

[0074] In the present embodiment, the second signal line 22, the split ground electrode 421, and the split ground electrode 422 are arranged in this order in the width direction of the second signal line 22. The second signal line 22, the split ground electrode 421, and the split ground electrode 422 are spaced apart in the width direction of the second signal line 22. The distance between the split ground electrode 421 and the split ground electrode 422 in the width direction of the second signal line 22 is longer than the width W6 of the RF signal line 6. In the thickness direction D1 of the laminated substrate 1, the split ground electrode 421 and the split ground electrode 422 do not overlap with the RF signal line 6. In the present embodiment, the second signal line 22, the split ground electrode 421, and the split ground electrode 422 are formed, for example, by patterning a second copper foil attached to the second insulating layer 12.

[0075] In this embodiment, the signal line 23 and the third ground electrode 43 are formed, for example, by patterning a third copper foil attached to the third insulating layer 13 .

[0076] The first ground electrode 4 and the second ground electrode 40 are located on the main surface 101 of the laminated substrate 1. The second ground electrode 40 is connected to the first ground electrode 4. In this embodiment, the second ground electrode 40 and the first ground electrode 4 are integrated and seamlessly connected to each other. In this embodiment, the first ground electrode 4 and the second ground electrode 40 are formed by, for example, patterning a fourth copper foil attached to a second main surface of the first insulating layer 11, the second main surface being the opposite main surface to which the first copper foil is attached.

[0077] The RF signal line 6 is designed so that the impedance of the RF signal line 6 is, for example, 50 Ω. As shown in Fig. 9 , the RF signal line 6 is located between the second ground electrode 40 and the third ground electrode 43 in the thickness direction D1 of the laminated substrate 1. Therefore, in the multilayer substrate 100D, the laminated substrate 1, the RF signal line 6, the second ground electrode 40, and the third ground electrode 43 form a strip line.

[0078] (2) Effects In the multilayer substrate 100D according to the fifth embodiment, similar to the multilayer substrate 100 according to the first embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the multilayer substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100D.

[0079] Furthermore, the multilayer substrate 100D according to the fifth embodiment includes a strip line including the laminated substrate 1, the RF signal line 6, the second ground electrode 40, and the third ground electrode 43. Therefore, in addition to transmitting signals via the AC signal line 2, the multilayer substrate 100D can also be used to transmit high-frequency signals via the RF signal line 6.

[0080] In the multilayer substrate 100D according to the fifth embodiment, the first signal line 21 and the RF signal line 6 are arranged side by side in the width direction of the first signal line 21. In the thickness direction D1 of the multilayer substrate 1, the thickness T6 of the RF signal line 6 is the same as the thickness T21 of the first signal line 21.

[0081] According to the above configuration, the resistance value of the RF signal line 6 can be reduced, and the transmission loss of the high-frequency signal in the RF signal line 6 can be reduced.

[0082] In the multilayer substrate 100D according to the fifth embodiment, the first ground electrode 4 and the second ground electrode 40 are located on the main surface 101 of the multilayer substrate 1. The second ground electrode 40 is connected to the first ground electrode 4.

[0083] According to the above configuration, it is possible to improve noise resistance.

[0084] Sixth Embodiment A multilayer substrate 100E according to a sixth embodiment will be described with reference to Fig. 10. Regarding the multilayer substrate 100E according to the sixth embodiment, components similar to those of the multilayer substrate 100D according to the fifth embodiment (see Figs. 7 to 9) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 10, as in Figs. 7 to 9, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis, is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 (see Fig. 10) is indicated as the Z-axis.

[0085] (1) Configuration The multilayer substrate 100E according to the sixth embodiment differs from the multilayer substrate 100D according to the fifth embodiment in that it includes a plurality of signal conductor lines 71 to 73 (three in FIG. 10).

[0086] The signal conductor lines 71 to 73 are formed on the laminated substrate 1. In this embodiment, each of the signal conductor lines 71 to 73 is, for example, linear when viewed from above in the thickness direction D1 of the laminated substrate 1. When viewed from above in the thickness direction D1 of the laminated substrate 1, each of the signal conductor lines 71 to 73 may have a shape other than linear.

[0087] In this embodiment, the first signal line 21 and two signal conductor lines 71 and 72 are aligned in the width direction of the first signal line 21. More specifically, in this embodiment, the first signal line 21, the split ground electrode 411, the signal conductor line 71, the split ground electrode 412, and the signal conductor line 72 are aligned in the width direction of the first signal line 21 in the following order: first signal line 21, split ground electrode 411, signal conductor line 71, split ground electrode 412, and signal conductor line 72. In the width direction of the first signal line 21, the first signal line 21, the split ground electrode 411, the signal conductor line 71, the split ground electrode 412, and the signal conductor line 72 are spaced apart from one another. In this embodiment, the first signal line 21, the split ground electrode 411, the signal conductor line 71, the split ground electrode 412, and the signal conductor line 72 are formed, for example, by patterning a first copper foil attached to the first insulating layer 11.

[0088] In this embodiment, the second signal line 22 and one signal conductor line 73 are aligned in the width direction of the second signal line 22. More specifically, in this embodiment, the second signal line 22, the split ground electrode 421, the split ground electrode 422, and the signal conductor line 73 are aligned in the width direction of the second signal line 22 in the following order: second signal line 22, split ground electrode 421, split ground electrode 422, and signal conductor line 73. In the width direction of the second signal line 22, the second signal line 22, the split ground electrode 421, the split ground electrode 422, and the signal conductor line 73 are spaced apart from one another. In the thickness direction D1 of the laminated substrate 1, the split ground electrode 421 and the split ground electrode 422 do not overlap with the signal conductor line 71. In this embodiment, the second signal line 22, the split ground electrode 421, the split ground electrode 422, and the signal conductor line 73 are formed, for example, by patterning a second copper foil attached to the second insulating layer 12.

[0089] In this embodiment, the signal line 23 and the third ground electrode 43 are formed, for example, by patterning a third copper foil attached to the third insulating layer 13 .

[0090] In this embodiment, the first ground electrode 4 and the second ground electrode 40 are formed, for example, by patterning a fourth copper foil attached to a second main surface of the first insulating layer 11 opposite to the first main surface, which is the main surface to which the first copper foil is attached.

[0091] As can be seen from the above explanation, of the plurality of signal conductor lines 71 to 73, the number of signal conductor lines aligned with the first signal line 21 in the width direction of the first signal line 21 is the largest.

[0092] (2) Effects In the multilayer substrate 100E according to the sixth embodiment, similar to the multilayer substrate 100D according to the fifth embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100E.

[0093] Furthermore, the multilayer substrate 100E according to the sixth embodiment further includes a plurality of signal conductor lines 71 to 73, and therefore can be used to transmit a plurality of other signals via the signal conductor lines 71 to 73, respectively, in addition to transmitting a signal via the AC signal line 2.

[0094] Furthermore, in the multilayer substrate 100E of embodiment 6, the number of signal conductor lines that are aligned with the first signal line 21 in the width direction of the first signal line 21 is the largest among the multiple signal conductor lines 71 to 73, and therefore it is possible to reduce the resistance values ​​of more of the multiple signal conductor lines 71 to 73.

[0095] Seventh Embodiment A multilayer substrate 100F according to a seventh embodiment will be described with reference to Fig. 11. Regarding the multilayer substrate 100F according to the seventh embodiment, components similar to those of the multilayer substrate 100E according to the sixth embodiment (see Fig. 10) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 11, as in Fig. 10, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis, is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 (see Fig. 11) is indicated as the Z-axis.

[0096] (1) Configuration The multilayer substrate 100F of the seventh embodiment differs from the multilayer substrate 100E of the sixth embodiment in that it includes multiple (three in FIG. 11) signal conductor lines 71 to 73 arranged as shown in FIG. 11.

[0097] The multiple signal conductor lines 71 to 73 are formed on the laminated substrate 1. In this embodiment, when viewed in a plan view from the thickness direction D1 of the laminated substrate 1, each of the multiple signal conductor lines 71 to 73 is, for example, linear. The multiple signal conductor lines 71 to 73 are signal conductor lines through which different signals (for example, digital signals) are transmitted. When viewed in a plan view from the thickness direction D1 of the laminated substrate 1, each of the multiple signal conductor lines 71 to 73 may have a shape other than linear.

[0098] In this embodiment, the first signal line 21 and one signal conductor line 71 are aligned in the width direction of the first signal line 21. More specifically, in this embodiment, the first signal line 21, the split ground electrode 411, the signal conductor line 71, and the split ground electrode 412 are aligned in the width direction of the first signal line 21 in the following order: first signal line 21, split ground electrode 411, signal conductor line 71, and split ground electrode 412. In the width direction of the first signal line 21, the first signal line 21, the split ground electrode 411, the signal conductor line 71, and the split ground electrode 412 are spaced apart from one another. In this embodiment, the first signal line 21, the split ground electrode 411, the signal conductor line 71, and the split ground electrode 412 are formed, for example, by patterning a first copper foil attached to the first insulating layer 11.

[0099] In this embodiment, the second signal line 22 and the two signal conductor lines 73, 72 are arranged side by side in the width direction of the second signal line 22. More specifically, in this embodiment, the second signal line 22, the split ground electrode 421, the signal conductor line 73, the split ground electrode 422, and the signal conductor line 72 are arranged in the following order in the width direction of the second signal line 22: the second signal line 22, the split ground electrode 421, the signal conductor line 73, the split ground electrode 422, and the signal conductor line 72. In the width direction of the second signal line 22, the second signal line 22, the split ground electrode 421, the signal conductor line 73, the split ground electrode 422, and the signal conductor line 72 are spaced apart from one another. In this embodiment, the second signal line 22, the split ground electrode 421, the signal conductor line 73, the split ground electrode 422, and the signal conductor line 72 are formed, for example, by patterning a second copper foil attached to the second insulating layer 12.

[0100] In this embodiment, the signal line 23 and the third ground electrode 43 are formed, for example, by patterning a third copper foil attached to the third insulating layer 13 .

[0101] In this embodiment, the first ground electrode 4 and the second ground electrode 40 are formed, for example, by patterning a fourth copper foil attached to a second main surface of the first insulating layer 11 opposite to the first main surface, which is the main surface to which the first copper foil is attached.

[0102] The width W71 of the signal conductor line 71 is wider than the width W72 of the signal conductor line 72 and the width W73 of the signal conductor line 73. Therefore, in the multilayer substrate 100F, the signal conductor line 71, which has the widest width among the multiple signal conductor lines 71 to 73, is aligned with the first signal line 21 in the width direction of the first signal line 21.

[0103] (2) Effects In the multilayer substrate 100F according to the seventh embodiment, similar to the multilayer substrate 100E according to the sixth embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100F.

[0104] Furthermore, the multilayer substrate 100F according to the seventh embodiment further includes a plurality of signal conductor lines 71 to 73, and therefore can be used to transmit a plurality of other signals via the signal conductor lines 71 to 73, respectively, in addition to transmitting a signal via the AC signal line 2.

[0105] Furthermore, in the multilayer substrate 100F according to the seventh embodiment, the signal conductor line 71, which is the widest of the multiple signal conductor lines 71 to 73, is aligned with the first signal line 21 in the width direction of the first signal line 21.

[0106] According to the above configuration, it is possible to reduce the resistance value of the signal conductor line 71, which is the widest of the plurality of signal conductor lines 71 to 73.

[0107] Eighth Embodiment A multilayer substrate 100G according to an eighth embodiment will be described with reference to Fig. 12. Regarding the multilayer substrate 100G according to the eighth embodiment, components similar to those of the multilayer substrate 100E according to the sixth embodiment (see Fig. 10) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 12, as in Fig. 10, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 (see Fig. 12) is indicated as the Z-axis.

[0108] (1) Configuration The multilayer substrate 100G of the eighth embodiment differs from the multilayer substrate 100E of the sixth embodiment in that the thickness TA2 of the second region A2, in which the plurality of signal conductor lines 71 to 73 (three in FIG. 12 ) are formed in the laminated substrate 1, is thinner than the thickness TA1 of the first region A1, in which the plurality of signal lines 21 to 23 and the ground electrode 4 are formed in the laminated substrate 1.

[0109] In this embodiment, the first signal line 21 and three signal conductor lines 71 to 73 are arranged side by side in the width direction of the first signal line 21. More specifically, in this embodiment, the first signal line 21, the split ground electrode 411, the signal conductor line 71, the signal conductor line 72, the signal conductor line 73, and the split ground electrode 412 are arranged in the following order in the width direction of the first signal line 21: the first signal line 21, the split ground electrode 411, the signal conductor line 71, the signal conductor line 72, the signal conductor line 73, and the split ground electrode 412. In this embodiment, the first signal line 21, the split ground electrode 411, the signal conductor line 71, the signal conductor line 72, the signal conductor line 73, and the split ground electrode 412 are formed, for example, by patterning a first copper foil attached to the first insulating layer 11.

[0110] In the present embodiment, the second signal line 22 and the fifth ground electrode 42 are arranged in the width direction of the second signal line 22 in the order of the second signal line 22 and the fifth ground electrode 42. The second signal line 22 and the fifth ground electrode 42 are spaced apart from each other in the width direction of the second signal line 22. In the present embodiment, the second signal line 22 and the fifth ground electrode 42 are formed by, for example, patterning a second copper foil attached to the second insulating layer 12.

[0111] In this embodiment, the signal line 23 is formed by, for example, patterning a third copper foil attached to the third insulating layer 13 .

[0112] In this embodiment, the first ground electrode 4 and the second ground electrode 40 are formed, for example, by patterning a fourth copper foil attached to a second main surface of the first insulating layer 11 opposite to the first main surface, which is the main surface to which the first copper foil is attached.

[0113] (2) Effects In the multilayer substrate 100G according to the eighth embodiment, similar to the multilayer substrate 100E according to the sixth embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100G.

[0114] Ninth Embodiment A multilayer substrate 100H according to a ninth embodiment will be described with reference to Fig. 13. Regarding the multilayer substrate 100H according to the ninth embodiment, components similar to those of the multilayer substrate 100G according to the eighth embodiment (see Fig. 12) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 13, as in Fig. 12, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 (see Fig. 13) is indicated as the Z-axis.

[0115] (1) Configuration The multilayer substrate 100H according to the ninth embodiment differs from the multilayer substrate 100G according to the eighth embodiment in that the thickness TA2 of the second region A2 in which the multiple (three in FIG. 12 ) signal conductor lines 71 to 73 are formed in the multilayer substrate 1 is the same as the thickness of the insulating layer 11.

[0116] (2) Effects In the multilayer substrate 100H according to the ninth embodiment, similar to the multilayer substrate 100G according to the eighth embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100H.

[0117] Tenth Embodiment A multilayer substrate 100I according to a tenth embodiment will be described with reference to Fig. 14. Regarding the multilayer substrate 100I according to the tenth embodiment, components similar to those of the multilayer substrate 100G according to the eighth embodiment (see Fig. 12) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 14, as in Fig. 12, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis is defined, and the axis along the thickness direction D1 of the multilayer substrate 1 (see Fig. 14) is indicated as the Z-axis.

[0118] (1) Configuration The multilayer substrate 100I according to the tenth embodiment differs from the multilayer substrate 100G according to the eighth embodiment in that it includes a plurality of land electrodes 8. The plurality of land electrodes 8 are formed on the multilayer substrate 1.

[0119] In this embodiment, the third ground electrode 43 is divided into two split ground electrodes 431 and 432. The land electrodes 8 are arranged side by side in the width direction of the signal line 23. More specifically, in this embodiment, the signal line 23, split ground electrode 431, land electrode 8, land electrode 8, and split ground electrode 432 are arranged in the following order: signal line 23, split ground electrode 431, land electrode 8, land electrode 8, and split ground electrode 432.

[0120] In this embodiment, the thickness of the multiple land electrodes 8 is thinner than the thickness T21 of the first signal line 21. Each of the multiple land electrodes 8 includes a conductor portion 81 having the same thickness as the thickness T23 of the signal line 23 and a plated portion 82 laminated on the conductor portion 81. The multilayer substrate 100I further includes a first protective film 110 disposed on the first main surface 101 of the multilayer substrate 1 and a second protective film 120 disposed on the second main surface 102 of the multilayer substrate 1. Each of the first protective film 110 and the second protective film 120 includes, for example, a polyimide film and an adhesive layer. The material of the adhesive layer includes, for example, an acrylic resin, a silicone resin, an epoxy resin, or a urethane resin. If the multilayer substrate 100I does not have a bent portion, each of the first protective film 110 and the second protective film 120 is not limited to a configuration including a polyimide film and an adhesive layer, and may be a protective film formed using, for example, spin coating technology and photolithography technology.

[0121] The signal line 23, the split ground electrode 431, the conductor portion 81 of the land electrode 8, the conductor portion 81 of the land electrode 8 and the split ground electrode 432 are formed, for example, by patterning a third copper foil attached to the third insulating layer 13.

[0122] In addition, the multilayer substrate 100I of embodiment 10 further includes a plurality of solder portions 9 joined one-to-one to a plurality of land electrodes 8, and an electronic component E1 joined to the plurality of solder portions 9.

[0123] The electronic component E1 is, for example, a connector. The electronic component E1 is not limited to a connector, but may be another electronic component such as an IC chip or a surface-mount electronic component (for example, a chip inductor or a chip capacitor).

[0124] Although the multilayer substrate 100I includes a plurality of solder parts 9 and electronic components E1, it may not necessarily include a plurality of solder parts 9 and electronic components E1.

[0125] (2) Effects In the multilayer substrate 100I according to the tenth embodiment, similar to the multilayer substrate 100G according to the eighth embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the multilayer substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100I.

[0126] Moreover, the multilayer substrate 100I according to the tenth embodiment further includes a plurality of land electrodes 8 formed on the multilayer substrate 1. The thickness of the plurality of land electrodes 8 may be the same as the thickness T23 of one signal line 23, which is different from the first signal line 21, among the plurality of signal lines 21 to 23. The thickness T23 of the signal line 23 is the same as the thickness T22 of the second signal line 22, but may be different from the thickness T22 of the second signal line 22.

[0127] According to the above configuration, the thickness of the plurality of land electrodes 8 can be made thinner than the thickness T21 of the first signal line 21, which reduces the heat capacity of each of the plurality of land electrodes 8 and improves the mounting efficiency of the electronic component E1 mounted on the plurality of land electrodes 8.

[0128] In addition, the multilayer substrate 100I of embodiment 10 further includes a plurality of solder portions 9 joined one-to-one to a plurality of land electrodes 8, and an electronic component E1 joined to the plurality of solder portions 9.

[0129] According to the above configuration, it is possible to provide a multilayer substrate 100I including an electronic component E1.

[0130] Eleventh Embodiment A multilayer substrate 100J according to an eleventh embodiment will be described with reference to Fig. 15. Regarding the multilayer substrate 100J according to the eleventh embodiment, components similar to those of the multilayer substrate 100B according to the third embodiment (see Fig. 5) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 15, as in Fig. 5, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis, is defined, and the axis along the thickness direction D1 (see Fig. 15) of the multilayer substrate 1 is indicated as the Z-axis.

[0131] (1) Configuration The multilayer substrate 100J according to the eleventh embodiment differs from the multilayer substrate 100B according to the third embodiment in that the thickness T23 of the signal line 23 is greater than the thickness T22 of the second signal line 22. In the eleventh embodiment, the thickness T23 of the signal line 23 is the same as the thickness T21 of the first signal line 21, but may be different from the thickness T21 of the first signal line 21.

[0132] (2) Effects In the multilayer substrate 100J according to the eleventh embodiment, similar to the multilayer substrate 100B according to the third embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100J.

[0133] In the multilayer substrate 100J according to the eleventh embodiment, the thickness T23 of the signal line 23 is greater than the thickness T22 of the second signal line 22.

[0134] According to the above configuration, the AC resistance of the AC signal line 2 can be further reduced.

[0135] (Embodiment 12) A multilayer substrate 100K according to embodiment 12 will be described with reference to Fig. 16. Regarding the multilayer substrate 100K according to embodiment 12, components similar to those of the multilayer substrate 100E according to embodiment 6 (see Fig. 10) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 16, as in Fig. 10, an orthogonal coordinate system having three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis, is defined, and the axis along the thickness direction D1 (see Fig. 16) of the multilayer substrate 1 is indicated as the Z-axis.

[0136] (1) Configuration The multilayer substrate 100K according to the twelfth embodiment differs from the multilayer substrate 100E according to the sixth embodiment in that the thickness T23 of the signal line 23 and the thickness T43 of the third ground electrode 43 are thicker than the thickness T22 of the second signal line 22. In the twelfth embodiment, the thickness T23 of the signal line 23 and the thickness T43 of the third ground electrode 43 are the same as the thickness T21 of the first signal line 21, but may be different from the thickness T21 of the first signal line 21.

[0137] (2) Effects In the multilayer substrate 100K according to the twelfth embodiment, similar to the multilayer substrate 100E according to the sixth embodiment, the thickness T21 of the first signal line 21 overlapping the ground electrode 4 in the thickness direction D1 of the laminated substrate 1 is greater than the thickness T22 of the second signal line 22. This makes it possible to reduce the AC resistance of the AC signal line 2 while suppressing an increase in the overall thickness of the multilayer substrate 100K.

[0138] In the multilayer substrate 100K according to the twelfth embodiment, the thickness T23 of the signal line 23 is greater than the thickness T22 of the second signal line 22.

[0139] According to the above configuration, the AC resistance of the AC signal line 2 can be further reduced.

[0140] (Embodiment 13) A multilayer substrate 100L according to embodiment 13 will be described with reference to Fig. 17. With regard to the multilayer substrate 100L according to embodiment 13, components that are the same as those in the multilayer substrate 100 according to embodiment 1 (see Figs. 1 to 3) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 17, as in Figs. 1 to 3, Cartesian coordinates having three mutually orthogonal axes, namely, an X-axis, a Y-axis, and a Z-axis, are defined and expressed.

[0141] (1) Configuration As shown in FIG. 17, a multilayer substrate 100L according to the thirteenth embodiment differs from the multilayer substrate 100 according to the first embodiment in that it is curved.

[0142] The multilayer substrate 100L is bent by plastically deforming the thermoplastic resin of the multilayer substrate 1, and the multilayer substrate 100L itself maintains its shape.

[0143] (2) Effects Similar to the multilayer substrate 100 according to the first embodiment, the multilayer substrate 100L according to the thirteenth embodiment can reduce AC resistance.

[0144] Furthermore, the multilayer substrate 100L according to the thirteenth embodiment can be easily arranged in the housing of an electronic device, for example, when the housing of the electronic device has a curved space for accommodating the multilayer substrate 100L.

[0145] (Modifications) The above-described embodiments 1 to 13 are merely examples of various embodiments of the present invention. The above-described embodiments 1 to 13 can be modified in various ways depending on the design and the like, and may be combined as appropriate, as long as the object of the present invention can be achieved.

[0146] For example, the material of each of the multiple insulating layers 11-13 may be, for example, polyimide (PI) or modified polyimide (modified-PI). In this case, each of the multiple first connecting conductors 32 and the multiple second connecting conductors 33 may be formed by through-hole plating. Furthermore, the first connecting conductor 32 and the third connecting conductor 31, which are connected to each other, may be formed by a single through-hole plating. The material of the through-hole plating may be, for example, copper. Furthermore, the laminated substrate 1 may include an adhesive layer interposed between two of the multiple insulating layers 11-13 that are adjacent to each other in the thickness direction D1 of the laminated substrate 1.

[0147] Furthermore, the multilayer substrates 100A to 100K of the second to twelfth embodiments may be curved in the same manner as the multilayer substrate 100L of the thirteenth embodiment.

[0148] Furthermore, the multilayer substrates 100, 100A-100H, and 100J-100L may further include at least one of a first protective film disposed on the first main surface 101 of the laminate substrate 1 and a second protective film disposed on the second main surface 102 of the laminate substrate 1. Each of the first protective film and the second protective film includes, for example, a polyimide film and an adhesive layer. The adhesive layer may be made of, for example, an acrylic resin, a silicone resin, an epoxy resin, or a urethane resin. As long as the multilayer substrates 100, 100A-100H, and 100J-100K do not have any bent portions, each of the first protective film and the second protective film is not limited to a configuration including a polyimide film and an adhesive layer, and may be a protective film formed using, for example, spin coating technology and photolithography technology.

[0149] (Aspects) The present specification discloses the following aspects.

[0150] A multilayer substrate (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G; 100H; 100I; 100J; 100K; 100L) according to a first aspect includes a laminated substrate (1), an AC signal line (2), and a ground electrode (4). The laminated substrate (1) includes a plurality of insulating layers (11-13; 11-14) stacked one on the other. The AC signal line (2) is formed on the laminated substrate (1). The ground electrode (4) is formed on the laminated substrate (1). The ground electrode (4) overlaps the AC signal line (2) in a thickness direction (D1) of the laminated substrate (1). The AC signal line (2) has a plurality of signal lines (21-23; 21-24) spaced apart from one another in the thickness direction (D1) of the laminated substrate (1). In the AC signal line (2), a plurality of signal lines (21-23; 21-24) are electrically connected by a plurality of connecting conductors that penetrate one of the plurality of insulating layers (11-13; 11-14) in the thickness direction (D1) of the laminated substrate (1). The plurality of signal lines (21-23; 21-24) include a first signal line (21) adjacent to the ground electrode (4) in the thickness direction (D1) of the laminated substrate (1) and a second signal line (22) adjacent to the first signal line (21) in the thickness direction (D1) of the laminated substrate (1). In the thickness direction (D1) of the laminated substrate (1), the thickness (T21) of the first signal line (21) is greater than the thickness (T22) of the second signal line (22).

[0151] According to this aspect, it is possible to reduce AC resistance.

[0152] In the multilayer substrate (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G; 100H; 100I; 100J; 100K; 100L) according to the second aspect, in the first aspect, the ground electrode (4) overlaps with more than half of the area of ​​the first signal line (21) in the thickness direction (D1) of the multilayer substrate (1) in the width direction.

[0153] According to this aspect, the bias in current density in the width direction of the first signal line (21) can be further reduced, and the AC resistance can be further reduced, compared to when an area of ​​less than half of the width direction of the first signal line (21) in the thickness direction (D1) of the laminated substrate (1) overlaps with the ground electrode (4).

[0154] A multilayer substrate (100B; 100C; 100J) according to a third aspect is based on the second aspect. The plurality of signal lines (21 to 24) further includes a third signal line (24) adjacent to the ground electrode (4) in the width direction of the first signal line (21).

[0155] According to this aspect, it is possible to further reduce the AC resistance.

[0156] A multilayer substrate (100C; 100J) according to a fourth aspect is based on the third aspect, and in the thickness direction (D1) of the multilayer substrate (1), a thickness (T4) of the ground electrode (4) and a thickness (T24) of the third signal line (24) are greater than a thickness (T22) of the second signal line (22).

[0157] According to this aspect, the thickness (T4) of the ground electrode (4) is greater than the thickness (T22) of the second signal line (22), which makes it possible to further stabilize the potential of the ground electrode (4). Furthermore, the thickness (T24) of the third signal line (24) is greater than the thickness (T22) of the second signal line (22), which makes it possible to further reduce AC resistance.

[0158] A multilayer substrate (100D) according to a fifth aspect is the first or second aspect, further comprising an RF signal line (6), a second ground electrode (40), and a third ground electrode (43). The RF signal line (6) is formed on the laminate substrate (1). The second ground electrode (40) is formed on the laminate substrate (1). The second ground electrode (40) faces the RF signal line (6) through at least one insulating layer (11) of the plurality of insulating layers (11-13) in the thickness direction (D1) of the laminate substrate (1), and is different from the first ground electrode (4), which is the ground electrode (4). The third ground electrode (43) is formed on the laminate substrate (1). The third ground electrode (43) faces the RF signal line (6) through an insulating layer (12, 13) different from the one insulating layer of the plurality of insulating layers (11-13) in the thickness direction (D1) of the laminate substrate (1).

[0159] According to this aspect, the laminated substrate (1), the RF signal line (6), the strip line including the second ground electrode (40), and the third ground electrode (43) are provided, and therefore, in addition to transmitting signals via the AC signal line (2), the RF signal line (6) can also be used to transmit high-frequency signals.

[0160] A multilayer substrate (100D) according to a sixth aspect is based on the fifth aspect. The first signal line (21) and the RF signal line (6) are arranged side by side in the width direction of the first signal line (21). In the thickness direction (D1) of the multilayer substrate (1), the thickness (T6) of the RF signal line (6) is the same as the thickness (T21) of the first signal line (21).

[0161] According to this aspect, the resistance value of the RF signal line (6) can be reduced, and the transmission loss of the high frequency signal in the RF signal line (6) can be reduced.

[0162] A multilayer substrate (100D) according to a seventh aspect is the fifth or sixth aspect, further comprising an RF signal line (6), a second ground electrode (40), and a third ground electrode (43). The RF signal line (6) is formed on the laminate substrate (1). The second ground electrode (40) is formed on the laminate substrate (1). The second ground electrode (40) faces the RF signal line (6) in the thickness direction (D1) of the laminate substrate (1) via at least one insulating layer (11) among the plurality of insulating layers (11 to 13), and is different from the first ground electrode (4), which is the ground electrode (4). The third ground electrode (43) is formed on the laminate substrate (1). The third ground electrode (43) faces the RF signal line (6) in the thickness direction (D1) of the laminate substrate (1) via an insulating layer (12, 13) among the plurality of insulating layers (11 to 13) that is different from the one insulating layer among the plurality of insulating layers (11 to 13). The first ground electrode (4) and the second ground electrode (40) are located on the main surface (101) of the laminated substrate (1). The second ground electrode (40) is connected to the first ground electrode (4).

[0163] According to this aspect, since the strip line includes the laminated substrate (1), the RF signal line (6), the second ground electrode (40), and the third ground electrode (43), it can be used to transmit high-frequency signals via the RF signal line (6) in addition to transmitting signals via the AC signal line (2). Also, according to this aspect, since the first ground electrode (4) and the second ground electrode (40) are located on the main surface (101) of the laminated substrate (1) and the second ground electrode (40) is connected to the first ground electrode (4), it is possible to improve noise resistance.

[0164] A multilayer substrate (100E; 100G; 100H; 100K) according to an eighth aspect is any one of the first to fourth aspects, further comprising a plurality of signal conductor lines (71-73) formed on the laminated substrate (1). Of the plurality of signal conductor lines (71-73), the number of signal conductor lines aligned with the first signal line (21) in the width direction of the first signal line (21) is the largest.

[0165] According to this aspect, since the multiple signal conductor lines (71-73) are further provided, the multiple signal conductor lines (71-73) can be used to transmit multiple other signals, respectively, in addition to the signal transmission via the AC signal line (2). Furthermore, according to this aspect, among the multiple signal conductor lines (71-73), the number of signal conductor lines aligned with the first signal line (21) in the width direction of the first signal line (21) is the largest, so it is possible to reduce the resistance value of more of the multiple signal conductor lines (71-73).

[0166] A multilayer substrate (100F) according to a ninth aspect is any one of the first to fourth aspects, further comprising a plurality of signal conductor lines (71-73) formed on the laminated substrate (1). In the multilayer substrate (100F), the widest signal conductor line (71) among the plurality of signal conductor lines (71-73) is aligned with the first signal line (21) in the width direction of the first signal line (21).

[0167] According to this aspect, since the multiple signal conductor lines (71-73) are further provided, the multiple signal conductor lines (71-73) can be used to transmit multiple other signals, respectively, in addition to the signal transmission via the AC signal line (2). Also, according to this aspect, since the widest signal conductor line (71) of the multiple signal conductor lines (71-73) is aligned with the first signal line (21) in the width direction of the first signal line (21), it is possible to reduce the resistance value of the widest signal conductor line (71) of the multiple signal conductor lines (71-73).

[0168] A multilayer substrate (100I) according to a tenth aspect is any one of the first to ninth aspects, further comprising a plurality of land electrodes (8) formed on the multilayer substrate (1). The thickness of the plurality of land electrodes (8) is thinner than the thickness (T21) of the first signal line (21).

[0169] According to this aspect, the thickness of the plurality of land electrodes (8) can be made thinner than the thickness (T21) of the first signal line (21), which reduces the heat capacity of each of the plurality of land electrodes (8) and improves the mounting efficiency of the electronic components (E1) mounted on the plurality of land electrodes (8).

[0170] The multilayer substrate (100I) according to the eleventh aspect is the same as that of the tenth aspect, and further comprises a plurality of solder portions (9) joined one-to-one to a plurality of land electrodes (8), and electronic components (E1) joined to the plurality of solder portions (9).

[0171] According to this aspect, it is possible to provide a multilayer substrate (100I) equipped with an electronic component (E1).

[0172] In the multilayer substrate (100J; 100K) according to the twelfth aspect, in any one of the first to fourth aspects, the thickness (T23) of the signal line (23) that is farthest from the ground electrode (4) in the thickness direction (D1) of the laminated substrate (1) among the plurality of signal lines (21 to 23; 21 to 24) is thicker than the thickness (T22) of the second signal line (22).

[0173] According to this aspect, it is possible to further reduce the AC resistance of the AC signal line (2).

[0174] A multilayer substrate (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G; 100H; 100I; 100J; 100K; 100L) according to a thirteenth aspect is any one of the first to twelfth aspects, in which the material of each of the plurality of insulating layers (11 to 13) includes a thermoplastic resin.

[0175] According to this aspect, it is possible to improve the bendability of the multilayer substrate (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G; 100H; 100I; 100J; 100K; 100L).

[0176] REFERENCE SIGNS LIST 1 laminated substrate 101 principal surface 11, 12, 13, 14 insulating layer 2 AC signal line 21 signal line (first signal line) 22 signal line (second signal line) 23 signal line 24 signal line (third signal line) 31 third connecting conductor 32 first connecting conductor 33 second connecting conductor 34 fourth connecting conductor 4 ground electrode (first ground electrode) 40 second ground electrode 43 third ground electrode 6 RF signal line 71, 72, 73 signal conductor line 8 land electrode 9 solder part 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H, 100I, 100J, 100K, 100L multilayer substrate D1 thickness direction E1 electronic component T4 thickness T21 Thickness T22 Thickness T23 Thickness W21, W22, W23 Line width

Claims

1. A multilayer board comprising: a laminated board having a plurality of insulating layers stacked on top of each other; an AC signal line formed on the laminated board; and a ground electrode formed on the laminated board and overlapping the AC signal line in a thickness direction of the laminated board, wherein the AC signal line has a plurality of signal lines spaced apart from each other in the thickness direction of the laminated board, the plurality of signal lines being electrically connected by a plurality of connecting conductors that penetrate one of the plurality of insulating layers in the thickness direction of the laminated board, the plurality of signal lines including: a first signal line adjacent to the ground electrode in the thickness direction of the laminated board; and a second signal line adjacent to the first signal line in the thickness direction of the laminated board, wherein the thickness of the first signal line is greater than the thickness of the second signal line in the thickness direction of the laminated board.

2. The multilayer board according to claim 1, wherein the ground electrode overlaps with at least half of the area of ​​the first signal line in the width direction in the thickness direction of the multilayer board.

3. The multilayer board according to claim 2, wherein the plurality of signal lines further include a third signal line adjacent to the ground electrode in the width direction of the first signal line.

4. The multilayer board according to claim 3, wherein the thickness of the ground electrode and the thickness of the third signal line are greater than the thickness of the second signal line in the thickness direction of the multilayer board.

5. The multilayer board according to claim 1 or 2, further comprising: an RF signal line formed on the laminated board; a second ground electrode formed on the laminated board, facing the RF signal line in the thickness direction of the laminated board via at least one of the plurality of insulating layers, the second ground electrode being different from the first ground electrode which is the ground electrode; and a third ground electrode formed on the laminated board, facing the RF signal line in the thickness direction of the laminated board via an insulating layer different from the one of the plurality of insulating layers.

6. The multilayer board according to claim 5, wherein the first signal line and the RF signal line are arranged side by side in a width direction of the first signal line, and the thickness of the RF signal line is the same as the thickness of the first signal line in the thickness direction of the multilayer board.

7. The multilayer board according to claim 5 or 6, wherein the first ground electrode and the second ground electrode are located on a main surface of the multilayer board, and the second ground electrode is connected to the first ground electrode.

8. The multilayer board according to any one of claims 1 to 4, further comprising a plurality of signal conductor lines formed on the laminated board, wherein among the plurality of signal conductor lines, the number of signal conductor lines aligned with the first signal line in a width direction of the first signal line is the largest.

9. The multilayer board according to any one of claims 1 to 4, further comprising a plurality of signal conductor lines formed on the laminated board, the widest of the plurality of signal conductor lines being aligned with the first signal line in the width direction of the first signal line.

10. The multilayer board according to any one of claims 1 to 9, further comprising a plurality of land electrodes formed on the multilayer board, the thickness of the plurality of land electrodes being thinner than the thickness of the first signal line.

11. The multilayer board according to claim 10, further comprising: a plurality of solder parts joined to the plurality of land electrodes in a one-to-one relationship; and electronic components joined to the plurality of solder parts.

12. A multilayer board according to any one of claims 1 to 4, wherein the thickness of the signal line among the plurality of signal lines that is farthest from the ground electrode in the thickness direction of the laminated board is thicker than the thickness of the second signal line.

13. The multilayer board according to any one of claims 1 to 12, wherein the material of each of the plurality of insulating layers includes a thermoplastic resin.