Multilayered substrate

Abstract

The objective of the present invention is to reduce AC resistance. In a multilayer substrate (100), a plurality of ground electrodes (41-44) are spaced apart from each other in the thickness direction (D1) of a laminated substrate (1) and adjacent to a plurality of signal lines (21-24) in the width direction of the plurality of signal lines (21-24). In a first transmission line region in which the maximum line width of the plurality of signal lines (21-24) is smallest, the plurality of signal lines (21-24) do not overlap any of the plurality of ground electrodes (41-44) in the thickness direction (D1) of the laminated substrate (1). In a second transmission line region (102) in which the maximum line width of the plurality of signal lines (21-24) is greatest, one ground electrode (41) among the plurality of ground electrodes (41-44) overlaps the signal lines (22-24) other than the signal line (21) adjacent to the one ground electrode (41) among the plurality of signal lines (21-24).

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 substrate including a laminate (laminated substrate), three signal conductors (signal lines), and six ground conductors.

[0003] The laminate has a structure in which multiple resin layers (insulating layers) are stacked in the stacking direction. The three signal conductors 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, ground conductors are located on both sides of each of the three signal conductors in the width direction when viewed in a plan view from the stacking direction. High-frequency signals are transmitted through the three signal conductors.

[0004] International Publication No. 2023 / 037852

[0005] In the multilayer board disclosed in Patent Document 1, ground conductors are located on both sides of each of the three signal conductors in the width direction, and therefore, due to the proximity effect, current concentrates at both ends of each of the three signal conductors in the width direction, resulting in 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 multiple ground electrodes. The laminated substrate includes multiple insulating layers stacked one on top of the other. The AC signal line is formed on the laminated substrate. The AC signal line has multiple signal lines spaced apart in a thickness direction of the laminated substrate, and the multiple signal lines are electrically connected by multiple connection conductors that penetrate one of the insulating layers in the thickness direction. The multiple ground electrodes are formed on the laminated substrate. The multiple ground electrodes are spaced apart in the thickness direction and adjacent to the multiple signal lines in a width direction of the multiple signal lines. In a first transmission line region where the maximum line widths of the multiple signal lines are smallest, the multiple signal lines do not overlap any of the multiple ground electrodes in the thickness direction. In a second transmission line region where the maximum line widths of the multiple signal lines are large, one of the multiple ground electrodes overlaps with one of the multiple signal lines other than the signal line adjacent to the one ground electrode.

[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 plan view illustrating both a transmission line region and a mounting region in the multilayer substrate. FIG. 5 is a graph showing the relationship between AC resistance and signal line width in the multilayer substrate. FIG. 6 is a plan view of a portion of a multilayer substrate according to a second embodiment. FIG. 7 is a cross-sectional view of the multilayer substrate taken along line VII-VII in FIG. 6 . FIG. 8 is a cross-sectional view of the multilayer substrate taken along line VIII-VIII in FIG. 6 . FIG. 9 is a plan view of a portion of a multilayer substrate according to a third embodiment. FIG. 10 is a cross-sectional view of the multilayer substrate taken along line X-X in FIG. 9 . FIG. 11 is a cross-sectional view of the multilayer substrate taken along line XI-XI in FIG. 9 . FIG. 12 is a plan view of a portion of a multilayer substrate according to a fourth embodiment. FIG. 13 is a cross-sectional view of the multilayer substrate taken along line XIII-XIII in FIG. 12 . FIG. 14 is a cross-sectional view of the multilayer board taken along line XIV-XIV in FIG. 12 , showing the same multilayer board. FIG. 15 is a plan view of a portion of the multilayer board according to embodiment 5. FIG. 16 is a cross-sectional view of the same multilayer board taken along line XVI-XVI in FIG. 15 , showing the same multilayer board. FIG. 17 is a cross-sectional view of the same multilayer board taken along line XVII-XVII in FIG. 15 , showing the same multilayer board. FIG. 18 is a plan view of a portion of the multilayer board according to embodiment 6. FIG. 19 is a see-through plan view of the same multilayer board, showing the second signal line, the second ground electrode, and the RF signal line. FIG. 20 is a cross-sectional view of the same multilayer board taken along line XX-XX in FIG. 18 , showing the same multilayer board. FIG. 21 is a cross-sectional view of the same multilayer board taken along line XXI-XXI in FIG. 18 , showing the same multilayer board. FIG. 22 is a plan view of a portion of the multilayer board according to embodiment 7. FIG. 23 is a see-through plan view of the same multilayer board, showing the second signal line, the second ground electrode, and the RF signal line. FIG. 24 is a cross-sectional view of the same multilayer board taken along line XXIV-XXIV in FIG. 22 , showing the same multilayer board. Fig. 25 is a cross-sectional view of the multilayer substrate taken along line XXV-XXV in Fig. 22 , showing the same. Fig. 26 is a cross-sectional view of a multilayer substrate according to an eighth embodiment. Fig. 27 is a plan view of a portion of a multilayer substrate according to a ninth embodiment. Fig. 28 is a plan view of the same multilayer substrate, showing a second signal line, a second ground electrode, and an RF signal line in a see-through manner. Fig. 29 is a cross-sectional view of the same multilayer substrate taken along line XXIX-XXIX in Fig. 27 .FIG. 30 is a cross-sectional view of the multilayer board taken along line XXX-XXX in FIG. 27 , showing the same multilayer board as above. FIG. 31 is a plan view of a portion of the multilayer board according to embodiment 10. FIG. 32 is a cross-sectional view of the multilayer board taken along line XXXII-XXXII in FIG. 31 , showing the same multilayer board as above. FIG. 33 is a cross-sectional view of the multilayer board taken along line XXXIII-XXXIII in FIG. 31 , showing the same multilayer board as above. FIG. 34 is a perspective plan view of a main portion of the same multilayer board, explaining the position of a connecting conductor near the boundary region between the first transmission line region and the second transmission line region. FIG. 35 is a plan view of a portion of the multilayer board according to embodiment 11. FIG. 36 is a cross-sectional view of the multilayer board taken along line XXXVI-XXXVI in FIG. 35 , showing the same multilayer board as above. FIG. 37 is a cross-sectional view of the multilayer board taken along line XXXVII-XXXVII in FIG. 35 , showing the same multilayer board as above.

[0010] Hereinafter, embodiments 1 to 11 will be described with reference to the drawings. The drawings referred to in the following embodiments 1 to 11 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 Figures 1 to 3, the multilayer substrate 100 according to the first embodiment includes a laminated substrate 1, an AC signal line 2, and a plurality of (four in the example of Figure 2) ground electrodes 41 to 44. As shown in Figure 4, for example, the multilayer substrate 100 has a first transmission line region 101, a second transmission line region 102, a first mounting region 111, and a second mounting region 112. However, Figure 1 does not illustrate a portion of the multilayer substrate 100 that includes the first mounting region 111 and a portion that includes the second mounting region 112. In Figures 1 and 4, a boundary BL1 between the first transmission line region 101 and the second transmission line region 102 is shown by a dashed line, but this boundary BL1 is a virtual boundary shown for the purpose of explanation. The first mounting area 111 is an area where a first electronic component (e.g., a connector) is disposed, to which a first end of the AC signal line 2 and each of the plurality of ground electrodes 41 to 44 are connected. Disposing the first electronic component in the first mounting area 111 means that the first electronic component is mechanically connected to the multilayer substrate 100 and that the first electronic component is electrically connected to the AC signal line 2. The second mounting area 112 is an area where a second electronic component (e.g., a connector) is disposed, to which a second end of the AC signal line 2 and each of the plurality of ground electrodes 41 to 44 are connected. Disposing the second electronic component means that the second electronic component is mechanically connected to the multilayer substrate 100 and that the second electronic component is electrically connected to the AC signal line 2.

[0013] 1 to 4, 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, 13, and 14 (four in the example of Figures 2 and 3), and the plurality of insulating layers 11, 12, 13, and 14 are stacked. The thickness direction D1 of the laminated substrate 1 is the stacking direction of the plurality of insulating layers 11, 12, 13, and 14. Hereinafter, for convenience of explanation, the insulating layer 11, the insulating layer 12, the insulating layer 13, and the insulating layer 14 may be referred to as the first insulating layer 11, the second insulating layer 12, the third insulating layer 13, and the fourth insulating layer 14, respectively.

[0016] In the laminated substrate 1, a first insulating layer 11, a second insulating layer 12, a third insulating layer 13, and a fourth insulating layer 14 are stacked in the order of the first insulating layer 11, the second insulating layer 12, the third insulating layer 13, and the insulating layer 14.

[0017] The material of each of the multiple insulating layers 11, 12, 13, and 14 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. Also, in this embodiment, the third insulating layer 13 and the fourth insulating layer 14 are self-adhered, and no adhesive layer is interposed between the third insulating layer 13 and the fourth insulating layer 14.

[0018] The thickness of each of the insulating layers 11, 12, 13, and 14 is, for example, not less than 10 μm and not more than 120 μm.

[0019] In this embodiment, the laminated substrate 1 is, for example, L-shaped in a plan view from the thickness direction D1 of the laminated substrate 1. In the example of Fig. 1, the laminated substrate 1 has a rectangular first portion 10a whose length along the X-axis is longer than its length along the Y-axis, and an elongated second portion 10b whose length along the Y-axis is longer than its length along the X-axis.

[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 an AC signal with a frequency of 13.56 MHz. The AC signal line 2 is not limited to an NFC signal line, and may be a digital signal line or a differential line.

[0021] 2 and 3 , the AC signal line 2 has a plurality of signal lines (signal electrodes) 21, 22, 23, and 24 that are spaced apart from one another in the thickness direction D1 of the laminated substrate 1. In a plan view from the thickness direction D1 of the laminated substrate 1, the plurality of signal lines 21, 22, 23, and 24 overlap one another. For ease of explanation, the signal lines 21, 22, 23, and 24 may hereinafter be referred to as the first signal line 21, the second signal line 22, the third signal line 23, and the fourth signal line 24, respectively.

[0022] The signal lines 21, 22, 23, and 24 have line widths W21, W22, W23, and W24, respectively.

[0023] Each of the signal lines 21 to 24 is electrically conductive and may be made of, for example, copper.

[0024] The thickness of each of the signal lines 21 to 24 is, for example, 3 μm to 40 μm, and is thinner than the thickness of each of the insulating layers 11 to 14.

[0025] The first signal line 21 is laminated on the first insulating layer 11. The second signal line 22 is laminated on the second insulating layer 12. The third signal line 23 is laminated on the third insulating layer 13. The fourth signal line 24 is laminated on the fourth insulating layer 14. In the multilayer substrate 100, the first signal line 21, the first insulating layer 11, the second insulating layer 12, the second signal line 22, the third insulating layer 13, the third signal line 23, the fourth insulating layer 14, and the fourth signal line 24 are laminated in this order: first signal line 21, first insulating layer 11, second insulating layer 12, second signal line 22, third insulating layer 13, third signal line 23, fourth insulating layer 14, and fourth signal line 24.

[0026] Each of the multiple signal lines 21 to 24 is formed in a predetermined pattern. In this embodiment, each of the multiple signal lines 21 to 24 is L-shaped when viewed in a plan view from the thickness direction D1 of the laminated substrate 1. The first signal line 21 is formed, for example, by patterning copper foil (hereinafter also referred to as the first copper foil) attached to the first insulating layer 11. The second signal line 22 is formed, for example, by patterning copper foil (hereinafter also referred to as the second copper foil) attached to the second insulating layer 12. The third signal line 23 is formed, for example, by patterning copper foil (hereinafter also referred to as the third copper foil) attached to the third insulating layer 13. The fourth signal line 24 is formed, for example, by patterning copper foil (hereinafter also referred to as the fourth copper foil) attached to the fourth insulating layer 14.

[0027] The AC signal line 2 also has a plurality of connecting conductors that electrically connect the plurality of signal lines 21 to 24. 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 14. Each of the plurality of connecting conductors is conductive. In the AC signal line 2, the plurality of signal lines 21 to 24 are electrically connected by a plurality of connecting conductors that penetrate one of the plurality of insulating layers 11 to 14 in the thickness direction D1 of the laminated substrate 1. The plurality of connecting conductors include a plurality of first connecting conductors 31 that penetrate the first insulating layer 11, a plurality of second connecting conductors 32 that penetrate the second insulating layer 12, a plurality of third connecting conductors 33 that penetrate the third insulating layer 13, and a plurality of fourth connecting conductors 34 that penetrate the fourth insulating layer 14. In this embodiment, a plurality of first connecting conductors 31 and a plurality of second connecting conductors 32 correspond one-to-one, and corresponding first connecting conductors 31 and second connecting conductors 32 overlap and are electrically connected in the thickness direction D1 of the laminated substrate 1.

[0028] In this embodiment, the multiple first connecting conductors 31 overlap the first signal line 21 in the thickness direction D1 of the laminated substrate 1. The multiple first connecting conductors 31 are arranged spaced apart in the length direction of the first signal line 21. The length 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. Furthermore, the multiple second connecting conductors 32 overlap the second signal line 22 in the thickness direction D1 of the laminated substrate 1. The multiple second connecting conductors 32 are arranged spaced apart in the length direction of the second signal line 22. The length 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. In this embodiment, the first signal line 21 and the second signal line 22 are electrically connected by a plurality of first connecting conductors 31 and a plurality of second connecting conductors 32 .

[0029] Furthermore, the plurality of third connecting conductors 33 overlap the third signal line 23 in the thickness direction D1 of the laminated substrate 1. The plurality of third connecting conductors 33 are arranged at intervals in the length direction of the third signal line 23. The length direction of the third signal line 23 is a direction along the third signal line 23, a direction perpendicular to the width direction (line width direction) of the third signal line 23, and is the direction in which a signal is transmitted in the third signal line 23. In this embodiment, the second signal line 22 and the third signal line 23 are electrically connected by the plurality of third connecting conductors 33.

[0030] Furthermore, the plurality of fourth connecting conductors 34 overlap the fourth signal line 24 in the thickness direction D1 of the laminated substrate 1. The plurality of fourth connecting conductors 34 are arranged at intervals in the length direction of the fourth signal line 24. The length direction of the fourth signal line 24 is a direction along the fourth signal line 24, a direction perpendicular to the width direction (line width direction) of the fourth signal line 24, and is the direction in which a signal is transmitted in the fourth signal line 24. In this embodiment, the third signal line 23 and the fourth signal line 24 are electrically connected by the plurality of fourth connecting conductors 34.

[0031] Each of the plurality of first connecting conductors 31, the plurality of second connecting conductors 32, the plurality of third connecting conductors 33, and the plurality of fourth connecting conductors 34 is electrically conductive. Each of the plurality of first connecting conductors 31, the plurality of second connecting conductors 32, the plurality of third connecting conductors 33, and the plurality of fourth connecting conductors 34 contains, for example, copper, a copper-tin alloy, and a resin. The plurality of first connecting conductors 31 are formed, for example, by filling a plurality of via holes formed in the first insulating layer 11 with a conductive paste containing copper, a low-melting-point metal (e.g., tin), and a resin, and heating the plurality of via holes, each of which is blocked by a portion of the first copper foil. The plurality of second 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 containing copper, a low-melting-point metal (e.g., tin), and a resin, and heating the plurality of via holes, each of which is blocked by a portion of the second copper foil. The plurality of third 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 containing copper, a low-melting-point metal (e.g., tin), and a resin, and heating the paste, with each via hole being blocked by a portion of the third copper foil. The plurality of fourth connecting conductors 34 are formed, for example, by filling a plurality of via holes formed in the fourth insulating layer 14 with a conductive paste containing copper, a low-melting-point metal (e.g., tin), and a resin, and heating the paste, with each via hole being blocked by a portion of the fourth copper foil.

[0032] (1.3) Ground Electrodes A plurality of ground electrodes 41 to 44 are formed on the laminated substrate 1. As shown in FIGS. 2 and 3 , the plurality of ground electrodes 41 to 44 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 plurality of ground electrodes 41 to 44 overlap one another. The plurality of ground electrodes 41 to 44 are adjacent to the plurality of signal lines 21 to 24 in the width direction of the plurality of signal lines 21 to 24. "The plurality of ground electrodes 41 to 44 are adjacent to the plurality of signal lines 21 to 24 in the width direction of the plurality of signal lines 21 to 24" means that the signal lines 21 to 24 and the ground electrodes 41 to 44 are spaced apart from one another in the width direction of the signal lines 21 to 24, with no other conductors being disposed between the signal lines 21 to 24 and the ground electrodes 41 to 44. Hereinafter, for ease of explanation, the ground electrodes 41, 42, 43, and 44 may be referred to as the first ground electrode 41, the second ground electrode 42, the third ground electrode 43, and the fourth ground electrode 44, respectively.

[0033] In this embodiment, the first ground electrode 41, the second ground electrode 42, the third ground electrode 43, and the fourth ground electrode 44 are adjacent to the first signal line 21, the second signal line 22, the third signal line 23, and the fourth signal line 24, respectively, in the width direction of the first signal line 21, the second signal line 22, the third signal line 23, and the fourth signal line 24.

[0034] Each of the ground electrodes 41 to 44 has electrical conductivity and is made of a material that includes, for example, copper.

[0035] The thickness of each of the ground electrodes 41 to 44 is, for example, not less than 3 μm and not more than 40 μm.

[0036] The first ground electrode 41 is layered on the first insulating layer 11. The second ground electrode 42 is layered on the second insulating layer 12. The third ground electrode 43 is layered on the third insulating layer 13. The fourth ground electrode 44 is layered on the fourth insulating layer 14. In the multilayer substrate 100, the first ground electrode 41, the first insulating layer 11, the second insulating layer 12, the second ground electrode 42, the third insulating layer 13, the third ground electrode 43, the fourth insulating layer 14, and the fourth ground electrode 44 are layered in this order.

[0037] Each of the ground electrodes 41 to 44 is formed in a predetermined pattern. In this embodiment, each of the ground electrodes 41 to 44 is L-shaped when viewed in a plan view from the thickness direction D1 of the laminated substrate 1. The first ground electrode 41 is formed, for example, by patterning a first copper foil attached to the first insulating layer 11. The second ground electrode 42 is formed, for example, by patterning a second copper foil attached to the second insulating layer 12. The third ground electrode 43 is formed, for example, by patterning a third copper foil attached to the third insulating layer 13. The fourth ground electrode 44 is formed, for example, by patterning a fourth copper foil attached to the fourth insulating layer 14.

[0038] In this embodiment, the multiple ground electrodes 41 to 44 are electrically connected by multiple connection conductors that penetrate one of the multiple insulating layers 11 to 14 in the thickness direction D1 of the laminated substrate 1. The multiple connection conductors include multiple fifth connection conductors 51 that penetrate the first insulating layer 11, multiple sixth connection conductors 52 that penetrate the second insulating layer 12, multiple seventh connection conductors 53 that penetrate the third insulating layer 13, and multiple eighth connection conductors 54 that penetrate the fourth insulating layer 14. In this embodiment, the multiple fifth connection conductors 51 and the multiple sixth connection conductors 52 correspond to each other one-to-one, and corresponding fifth connection conductors 51 and sixth connection conductors 52 overlap and are electrically connected in the thickness direction D1 of the laminated substrate 1.

[0039] In the present embodiment, the plurality of fifth connecting conductors 51 overlap the first ground electrode 41 in the thickness direction D1 of the laminated substrate 1. The plurality of fifth connecting conductors 51 are arranged spaced apart in the longitudinal direction of the first ground electrode 41. The longitudinal direction of the first ground electrode 41 is the same as the longitudinal direction of the first signal line 21. Furthermore, the plurality of sixth connecting conductors 52 overlap the second ground electrode 42 in the thickness direction D1 of the laminated substrate 1. The plurality of sixth connecting conductors 52 are arranged spaced apart in the longitudinal direction of the second ground electrode 42. The longitudinal direction of the second ground electrode 42 is the same as the longitudinal direction of the second signal line 22. In the present embodiment, the first ground electrode 41 and the second ground electrode 42 are electrically connected by the plurality of fifth connecting conductors 51 and the plurality of sixth connecting conductors 52.

[0040] The multiple seventh connecting conductors 53 overlap the third ground electrode 43 in the thickness direction D1 of the laminated substrate 1. The multiple seventh connecting conductors 53 are arranged to be spaced apart in the longitudinal direction of the third ground electrode 43. The longitudinal direction of the third ground electrode 43 is the same as the longitudinal direction of the third signal line 23. In this embodiment, the second ground electrode 42 and the third ground electrode 43 are electrically connected by the multiple seventh connecting conductors 53.

[0041] Furthermore, the multiple eighth connecting conductors 54 overlap the fourth ground electrode 44 in the thickness direction D1 of the laminated substrate 1. The multiple eighth connecting conductors 54 are arranged to be spaced apart in the length direction of the fourth ground electrode 44. The length direction of the fourth ground electrode 44 is the direction along the fourth signal line 24. In this embodiment, the third ground electrode 43 and the fourth ground electrode 44 are electrically connected by the multiple eighth connecting conductors 54.

[0042] Each of the plurality of fifth connecting conductors 51, the plurality of sixth connecting conductors 52, the plurality of seventh connecting conductors 53, and the plurality of eighth connecting conductors 54 is conductive. Each of the plurality of fifth connecting conductors 51, the plurality of sixth connecting conductors 52, the plurality of seventh connecting conductors 53, and the plurality of eighth connecting conductors 54 contains, for example, copper, a copper-tin alloy, and a resin. The plurality of fifth connecting conductors 51 are formed, for example, by filling a plurality of via holes formed in the first insulating layer 11 with a conductive paste containing copper, a low-melting-point metal (e.g., tin), and a resin, and heating the plurality of via holes, each of which is blocked by a portion of the first copper foil. The plurality of sixth connecting conductors 52 are formed, for example, by filling a plurality of via holes formed in the second insulating layer 12 with a conductive paste containing copper, a low-melting-point metal (e.g., tin), and a resin, and heating the plurality of via holes, each of which is blocked by a portion of the second copper foil. The seventh connecting conductors 53 are formed, for example, by filling a conductive paste containing copper, a low-melting-point metal (e.g., tin), and a resin into a plurality of via holes formed in the third insulating layer 13, each of which is blocked by a portion of the third copper foil, and then heating the filled via holes. The eighth connecting conductors 54 are formed, for example, by filling a conductive paste containing copper, a low-melting-point metal (e.g., tin), and a resin into a plurality of via holes formed in the fourth insulating layer 14, each of which is blocked by a portion of the fourth copper foil, and then heating the filled via holes.

[0043] (2) Layout The transmission line region of the multilayer substrate 100 includes a first transmission line region 101 and a second transmission line region 102. The first transmission line region 101 is the region where the maximum line width of the multiple signal lines 21 to 24 is smallest when viewed in a plan view from the thickness direction D1 of the laminated substrate 1, and the second transmission line region 102 is the region where the maximum line width of the multiple signal lines 21 to 24 is largest when viewed in a plan view from the thickness direction D1 of the laminated substrate 1. The maximum line width of the multiple signal lines 21 to 24 is the maximum value among the line width W21 of the first signal line 21, the line width W22 of the second signal line 22, the line width W23 of the third signal line 23, and the line width W24 of the fourth signal line 24. In the multilayer substrate 100 of this embodiment, the outer width W1 (see FIG. 1) in the width direction of the multiple signal lines 21 to 24 in the first transmission line region 101 is different from the outer width W2 (see FIG. 1) in the width direction of the multiple signal lines 21 to 24 in the second transmission line region 102. More specifically, the outer width W2 is wider than the outer width W1.

[0044] In the first transmission line region 101 of this embodiment, as shown in FIG. 2 , the line width W21 of the first signal line 21, the line width W22 of the second signal line 22, the line width W23 of the third signal line 23, and the line width W24 of the fourth signal line 24 are all the same. Therefore, in the second transmission line region 102, the maximum line width of the multiple signal lines 21 to 24 can be defined as any of the line widths W21 to W24. In the first transmission line region 101, from the viewpoint of increasing the cross-sectional area of ​​the AC signal line 2, it is preferable that the line widths W21 to W24 are the same and wider, but the line widths W21 to W24 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 24 in any cross section perpendicular to the longitudinal direction of the AC signal line 2.

[0045] In the first transmission line region 101 of this embodiment, as shown in FIG. 2, the electrode widths W41 to W44 of the ground electrodes 41 to 44 are the same, but may be different from one another.

[0046] 3 , in the second transmission line region 102 of this embodiment, the line width W22 of the second signal line 22, the line width W23 of the third signal line 23, and the line width W24 of the fourth signal line 24 are the same, and the line width W21 of the first signal line 21 is the smallest. Therefore, in the second transmission line region 102, the maximum line width of the multiple signal lines 21 to 24 can be defined as any of the line widths W22 to W24. In the second transmission line region 102, from the viewpoint of increasing the cross-sectional area of ​​the AC signal line 2, it is preferable that the line widths W22 to W24 are the same, and that the wider the line width, the greater the line width. However, the line widths W22 to W24 may be different from one another.

[0047] 3, in the second transmission line region 102 of the present embodiment, the electrode width W41 of one ground electrode 41 of the four ground electrodes 41 to 44 is wider than the electrode widths W42 to W44 of the remaining three ground electrodes 42 to 44. In the second transmission line region 102 of the present embodiment, the electrode widths W42 to W44 of three of the four ground electrodes 41 to 44 are the same, but the electrode widths W42 to W44 of the three ground electrodes 42 to 44 may be different from one another.

[0048] 2, in the first transmission line region 101 of this embodiment, the multiple signal lines 21 to 24 do not overlap any of the multiple ground electrodes 41 to 44 in the thickness direction D1 of the laminated substrate 1. In the second transmission line region 102 of this embodiment, as shown in FIG. 3, one ground electrode 41 (first ground electrode 41) of the multiple ground electrodes 41 to 44 overlaps in the thickness direction D1 with the signal lines 22 to 24 other than the signal line 21 that is adjacent to the ground electrode 41 in the width direction among the multiple signal lines 21 to 24.

[0049] In the second transmission line region 102 of this embodiment, as shown in FIG. 3 , the signal line 22, among the multiple signal lines 21 to 24, adjacent to the ground electrode 41 in the thickness direction D1 of the laminated substrate 1 has more than half of its widthwise area overlapping with the ground electrode 41 in the thickness direction D1. The ground electrode 41 and the signal line 22 being adjacent to each other in the thickness direction D1 of the laminated substrate 1 means that the ground electrode 41 and the signal line 22 are spaced apart from each other in the thickness direction D1 of the laminated substrate 1, and no other conductors exist between the ground electrode 41 and the signal line 22 in the thickness direction D1. The width H1 of the signal line 22 adjacent to the ground electrode 41 in the thickness direction D1 of the laminated substrate 1, in the overlapping area with the ground electrode 41, is, for example, half the line width W22. While the width H1 may be less than half the line width W22, it is preferably at least half the line width W22 from the viewpoint of improving the current distribution in the width direction of each of the signal lines 22 to 24.

[0050] (3) Characteristics of the Multilayer Substrate The multilayer substrate 100 of this embodiment can reduce the AC resistance of the AC signal line 2 compared to when the ground electrode is not overlapped with the signal line in the second transmission line region. The mechanism by which the AC resistance can be reduced will be described below.

[0051] In a transmission line having a layout similar to that of the first transmission line region 101, when the signal line width is changed with the maximum line width of the four signal lines 21 to 24 as the signal line width, the AC resistance decreases as the signal line width increases, as shown by characteristic A1 in Fig. 5. Furthermore, in a transmission line having a layout similar to that of the second transmission line region 102, when the ground electrode 41 overlaps the three signal lines 22 to 24 and the signal line width is changed with the maximum line width of the signal lines 22 to 24 as the signal line width, the AC resistance decreases as the signal line width increases, as shown by characteristic B1 in Fig. 5.

[0052] 5 shows that for both characteristics A1 and B1, the AC resistance decreases as the signal line width increases, but there is a point where characteristics A1 and B1 intersect. Furthermore, FIG. 5 shows that, at signal line widths narrower than the signal line width at the intersection of characteristics A1 and B1, characteristic A1 has a lower AC resistance. Furthermore, FIG. 5 shows that, at signal line widths wider than the signal line width at the intersection, characteristic B1 has a lower AC resistance.

[0053] Considering the characteristics A1 and B1 in Figure 5, when the signal line width is narrow, AC resistance can be further reduced by adopting a layout similar to the first transmission line region 101 and increasing the cross-sectional area of ​​the AC signal line 2. However, when the signal line width is wide, if a layout similar to the first transmission line region 101 is adopted, the current density in the center of each of the signal lines 21 to 24 is smaller than the current density at both ends in the width direction, thereby reducing the AC resistance reduction effect. In contrast, when the signal line width is wide, the cross-sectional area of ​​the AC signal line 2 can be secured even if the ground electrode 41 is arranged to overlap the signal lines 22 to 24 in the thickness direction D1 of the laminated substrate 1. Therefore, by overlapping the ground electrode 41 with the signal lines 22 to 24 in the thickness direction D1 of the laminated substrate 1, the difference between the current density at both ends in the width direction of each of the signal lines 22 to 24 and the current density at the center can be reduced, thereby further reducing AC resistance.

[0054] (4) Manufacturing Method of Multilayer Substrate In the manufacturing method of the multilayer substrate 100 of this embodiment, for example, the first insulating layer 11 on which the first signal line 21 and the first ground electrode 41 are formed, the second insulating layer 12 on which the second signal line 22 and the second ground electrode 42 are formed, the third insulating layer 13 on which the third signal line 23 and the third ground electrode 43 are formed, and the fourth insulating layer 14 on which the fourth signal line 24 and the fourth ground electrode 44 are formed are stacked on a metal plate (not shown), and pressed from above while being heated, thereby forming the multilayer substrate 100.

[0055] (5) Effects In the multilayer substrate 100 according to the first embodiment, the ground electrodes 41 to 44 are spaced apart from one another in the thickness direction D1 of the laminated substrate 1 and are adjacent to the signal lines 21 to 24 in the width direction of the signal lines 21 to 24. In the first transmission line region 101, in which the maximum line widths of the signal lines 21 to 24 are smallest, the signal lines 21 to 24 do not overlap with any of the ground electrodes 41 to 44 in the thickness direction D1 of the laminated substrate 1. In the second transmission line region 102, in which the maximum line widths of the signal lines 21 to 24 are large, one ground electrode 41 of the ground electrodes 41 to 44 overlaps with one of the signal lines 22 to 24, other than the signal line 21 adjacent to the one ground electrode 41.

[0056] The above configuration makes it possible to reduce the AC resistance of the multilayer substrate 100. More specifically, in the multilayer substrate 100 according to the first embodiment, in the first transmission line region 101 where the maximum line widths of the multiple signal lines 21 to 24 are smallest, the multiple signal lines 21 to 24 do not overlap any of the multiple ground electrodes 41 to 44 in the thickness direction D1 of the laminated substrate 1, thereby making it possible to increase the cross-sectional area of ​​the AC signal line 2 and reduce the AC resistance. Also, in the multilayer substrate 100 according to the first embodiment, in the second transmission line region 102 where the maximum line widths of the multiple signal lines 21 to 24 are large, one ground electrode 41 of the multiple ground electrodes 41 to 44 overlaps with one of the multiple signal lines 22 to 24 other than the signal line 21 adjacent to the one ground electrode 41. This reduces bias in the current density in the width direction of the multiple signal lines 21 to 24 and further reduces the AC resistance.

[0057] Furthermore, in the second transmission line region 102 of the multilayer substrate 100 according to the first embodiment, among the multiple signal lines 21 to 24, the signal line 22 adjacent to one ground electrode 41 in the thickness direction D1 of the laminated substrate 1 has more than half of its width overlapping with one ground electrode 41 in the thickness direction D1.

[0058] According to the above configuration, compared to the case where less than half of the width of the signal line 22 in the thickness direction D1 of the laminated substrate 1 overlaps with one ground electrode 41, the current distribution in the width direction of the signal lines 22 to 24 can be improved, and the bias in current density can be further reduced, thereby further reducing the AC resistance.

[0059] Furthermore, in the multilayer substrate 100 according to the first embodiment, the outer width W2 in the width direction of the multiple signal lines 21 to 24 in the second transmission line region 102 is wider than the outer width W1 in the width direction of the multiple signal lines 21 to 24 in the first transmission line region 101.

[0060] According to the above configuration, it is possible to further reduce the AC resistance in each of the first transmission line region 101 and the second transmission line region 102 of the AC signal line 2 .

[0061] (Embodiment 2) A multilayer substrate 100A according to embodiment 2 will be described with reference to Figures 6 to 8. Regarding 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 Figures 1 to 4) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 6 to 8, as in Figures 1 to 4, 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 7) is indicated as the Z-axis.

[0062] (1) Configuration The multilayer substrate 100A according to the second embodiment differs from the multilayer substrate 100 according to the first embodiment in that, as shown in FIG. 8 , of the four ground electrodes 41 to 44, the second ground electrode 42, rather than the first ground electrode 41, overlaps with the signal lines 21, 23, and 24 in the thickness direction D1 of the multilayer substrate 1.

[0063] 8 , in the second transmission line region 102 of this embodiment, the line width W21 of the first signal line 21, the line width W23 of the third signal line 23, and the line width W24 of the fourth signal line 24 are the same, and the line width W22 of the second signal line 22 is the smallest. Therefore, in the second transmission line region 102, the maximum line width of the multiple signal lines 21 to 24 can be defined as any of the line widths W21, W23, and W24. In the second transmission line region 102, from the viewpoint of increasing the cross-sectional area of ​​the AC signal line 2, it is preferable that the line widths W21, W23, and W24 are the same, and that the wider the line width, the greater the line width. However, the line widths W21, W23, and W24 may be different from one another.

[0064] 8, in the second transmission line region 102 of this embodiment, the electrode width W42 of one ground electrode 42 of the four ground electrodes 41 to 44 is wider than the electrode widths W41, W43, and W44 of the remaining three ground electrodes 41, 43, and 44. In the second transmission line region 102 of this embodiment, the electrode widths W41, W43, and W44 of three of the four ground electrodes 41 to 44 are the same, but the electrode widths W41, W43, and W44 of the three ground electrodes 41, 43, and 44 may be different from one another.

[0065] 7, in the first transmission line region 101 of this embodiment, the multiple signal lines 21 to 24 do not overlap any of the multiple ground electrodes 41 to 44 in the thickness direction D1 of the laminated substrate 1. In the second transmission line region 102 of this embodiment, as shown in FIG. 8, one ground electrode 42 (second ground electrode 42) of the multiple ground electrodes 41 to 44 overlaps in the thickness direction D1 with the signal lines 21, 23, and 24 of the multiple signal lines 21 to 24, except for the signal line 22 that is adjacent to the ground electrode 42 in the width direction.

[0066] In the second transmission line region 102 of this embodiment, the signal line 21, among the multiple signal lines 21 to 24, adjacent to the ground electrode 42 in the thickness direction D1, overlaps with the ground electrode 42 over more than half of its width in the thickness direction D1. The width H1 of the signal line 23 in the width direction in the region overlapping with the ground electrode 42 adjacent to the ground electrode 42 in the thickness direction D1 is, for example, half the line width W23. While the width H1 may be less than half the line width W23, it is preferable that the width H1 be equal to or greater than half the line width W23 from the viewpoint of improving the current distribution in the width direction of each of the signal lines 21, 23, and 24. The width H2 of the signal line 21 in the width direction in the region overlapping with the ground electrode 42 adjacent to the ground electrode 42 in the thickness direction D1 is, for example, half the line width W21. The width H2 may be less than half the line width W21, but from the viewpoint of improving the current distribution in the width direction of each of the signal lines 21, 23, and 24, it is preferable that the width H2 be equal to or greater than half the line width W21.

[0067] (2) Effects The multilayer substrate 100A according to the second embodiment, like the multilayer substrate 100 according to the first embodiment, is capable of reducing the AC resistance of the multilayer substrate 100. More specifically, in the multilayer substrate 100A according to the second embodiment, in the first transmission line region 101, the multiple signal lines 21 to 24 do not overlap any of the multiple ground electrodes 41 to 44 in the thickness direction D1 of the laminated substrate 1. This allows the cross-sectional area of ​​the AC signal line 2 to be increased, thereby reducing the AC resistance. Furthermore, in the multilayer substrate 100A according to the second embodiment, in the second transmission line region 102, one ground electrode 42 of the multiple ground electrodes 41 to 44 overlaps with the signal lines 21, 23, and 24 other than the signal line 22 adjacent to the one ground electrode 42 of the multiple signal lines 21 to 24. This reduces bias in the current density in the width direction of the multiple signal lines 21 to 24, thereby further reducing the AC resistance.

[0068] (Embodiment 3) A multilayer substrate 100B according to embodiment 3 will be described with reference to Figures 9 to 11. Regarding the multilayer substrate 100B according to embodiment 3, components similar to those of the multilayer substrate 100 according to embodiment 1 (see Figures 1 to 4) are denoted by the same reference numerals, and description thereof will be omitted. In Figures 9 to 11, as in Figures 1 to 4, 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 10) is indicated as the Z-axis.

[0069] 11 , in the second transmission line region 102 of the multilayer substrate 100B according to the third embodiment, the entire area of ​​the signal line 22 adjacent to the ground electrode 41 in the thickness direction D1 of the multilayer substrate 1 overlaps with the ground electrode 41 in the thickness direction D1. The electrode width W41 of the ground electrode 41 in the width direction of the signal line 22 is the total length of the line width W22 of the signal line 22, the electrode width W42 of the ground electrode 42, and the distance L2 between the signal line 22 and the ground electrode 42. The ground electrode 41 may be shorter than the total length as long as it overlaps with the entire area of ​​the signal line 22 and the fifth connecting conductor 51.

[0070] (2) Effects As with the multilayer substrate 100 according to the first embodiment, the multilayer substrate 100B according to the third embodiment can reduce the AC resistance of the multilayer substrate 100.

[0071] Furthermore, in the second transmission line region 102 of the multilayer substrate 100B according to the third embodiment, the signal line 22, among the multiple signal lines 21 to 24, that is adjacent to one ground electrode 41 in the thickness direction D1 has its entire widthwise region overlapping with one ground electrode 41 in the thickness direction D1.

[0072] According to the above configuration, it is possible to improve noise resistance.

[0073] (Embodiment 4) A multilayer substrate 100C according to embodiment 4 will be described with reference to Figures 12 to 14. Regarding the multilayer substrate 100C according to embodiment 4, components that are the same as those in the multilayer substrate 100 according to embodiment 1 (see Figures 1 to 4) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 12 to 14, as in Figures 1 to 4, 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 13) is indicated as the Z-axis.

[0074] (1) Configuration In the multilayer substrate 100C according to the fourth embodiment, as shown in FIG. 12 , when viewed in a plan view from the thickness direction D1 of the multilayer substrate 1, the multilayer substrate 1 has an elongated shape in which the length along the Y-axis is longer than the length along the X-axis.

[0075] In the multilayer substrate 100C, the outer width W1 in the width direction of the multiple signal lines 21 to 24 (see FIG. 13) in the first transmission line region 101 is the same as the outer width W2 in the width direction of the multiple signal lines 21 to 24 (see FIG. 14) in the second transmission line region 102.

[0076] In this embodiment, the transmission line region of the multilayer substrate 100C includes a first transmission line region 101, a second transmission line region 102, and a third transmission line region 103 located on the side of the second transmission line region 102 opposite the first transmission line region 101. The transmission line region of the multilayer substrate 100C also includes a fourth transmission line region 104 located between the first transmission line region 101 and the second transmission line region 102. Therefore, in the multilayer substrate 100C, the first transmission line region 101, the fourth transmission line region 104, the second transmission line region 102, and the third transmission line region 103 are arranged in this order: first transmission line region 101, fourth transmission line region 104, second transmission line region 102, and third transmission line region 103. In the multilayer substrate 100C, the outer width W1 of the first transmission line region 101, the outer width W4 of the fourth transmission line region 104, the outer width W2 of the second transmission line region 102, and the outer width W3 of the third transmission line region 103 are all the same.

[0077] 12, a boundary BL14 between the first transmission line region 101 and the fourth transmission line region 104 is shown by a dashed-dotted line. Also, in Fig. 12, a boundary BL24 between the fourth transmission line region 104 and the second transmission line region 102 is shown by a dashed-dotted line. Also, in Fig. 12, a boundary BL23 between the second transmission line region 102 and the third transmission line region 103 is shown by a dashed-dotted line. Each of the boundaries BL14, BL23, and BL24 is an imaginary boundary shown for the purpose of explanation.

[0078] 12, the maximum line width in the first transmission line region 101 (in the example of FIG. 13, line widths W21 to W24 of signal lines 21 to 24) is illustrated as X1. Also, in FIG. 12, the maximum line width in the second transmission line region 102 (in the example of FIG. 14, line widths W22 to W24 of signal lines 22 to 24) is illustrated as X2. Also, in FIG. 12, the maximum line width in the third transmission line region 103 is illustrated as X3. In the multilayer substrate 100C, X1 in the first transmission line region 101 is constant along the length of the first transmission line region 101, X2 in the second transmission line region 102 is constant along the length of the second transmission line region 102, and X3 in the third transmission line region 103 is constant along the length of the third transmission line region 103. Also, in the multilayer substrate 100C, X1<X3<X2. Furthermore, in the multilayer substrate 100C, the maximum line width in the fourth transmission line region 104 increases with increasing distance from the first transmission line region 101 and increasing distance from the second transmission line region 102.

[0079] In this embodiment, the electrode width W44 of the ground electrode 44 in the first transmission line region 101 is wider than the electrode width W44 of the ground electrode 44 in the third transmission line region 103, and the electrode width W44 of the ground electrode 44 in the third transmission line region 103 is wider than the electrode width W44 of the ground electrode 44 in the second transmission line region 102.

[0080] The third transmission line region 103 of this embodiment satisfies the condition X3≦(X1+X2) / 2, and similarly to the first transmission line region 101 (see FIG. 13 ), the multiple signal lines 21 to 24 do not overlap with any of the multiple ground electrodes 41 to 44 in the thickness direction D1 of the laminated substrate 1.

[0081] In the third transmission line region 103, when the condition X3>(X1+X2) / 2 is satisfied, one ground electrode 41 of the plurality of ground electrodes 41-44 overlaps with one of the plurality of signal lines 21-24 other than the signal line 21 adjacent to the one ground electrode 41, as in the second transmission line region 102.

[0082] In this embodiment, the maximum line width in the fourth transmission line region 104 is wider than (X1+X2) / 2, and similarly to the second transmission line region 102, one ground electrode 41 of the plurality of ground electrodes 41 to 44 overlaps with one of the plurality of signal lines 21 to 24 other than the signal line 21 adjacent to the one ground electrode 41.

[0083] (2) Effects As with the multilayer substrate 100 according to the first embodiment, the multilayer substrate 100C according to the fourth embodiment can reduce AC resistance.

[0084] Furthermore, in the multilayer substrate 100C according to the fourth embodiment, when the maximum line width in the first transmission line region 101 is X1 and the maximum line width in the second transmission line region 102 is X2, in the third transmission line region 103, among the plurality of signal lines 21 to 24, the maximum line width is greater than X1 and is not greater than (X1 + X2) / 2, the plurality of signal lines 21 to 24 do not overlap with any of the plurality of ground electrodes 41 to 44 in the thickness direction D1.

[0085] According to the above configuration, when the AC signal line 2 is formed across the first transmission line region 101, the second transmission line region 102, and the third transmission line region 103, it is possible to reduce the AC resistance.

[0086] Fifth Embodiment A multilayer substrate 100D according to a fifth embodiment will be described with reference to Figures 15 to 17. Regarding the multilayer substrate 100D according to the fifth embodiment, components that are the same as those of the multilayer substrate 100C according to the fourth embodiment (see Figures 12 to 14) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 15 to 17, as in Figures 12 to 14, 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 16) is indicated as the Z-axis.

[0087] (1) Configuration In the multilayer substrate 100D according to the fifth embodiment, as shown in FIG. 15 , the outer width W2 of the second transmission line region 102 is wider than the outer width W3 of the third transmission line region 103, and the outer width W3 of the third transmission line region 103 is wider than the outer width W1 of the first transmission line region 101.

[0088] In this embodiment, the electrode width W44 of the ground electrode 44 in the first transmission line region 101 is the same as the electrode width W44 of the ground electrode 44 in the third transmission line region 103, the electrode width W44 of the ground electrode 44 in the third transmission line region 103, and the electrode width W44 of the ground electrode 44 in the second transmission line region 102.

[0089] (2) Effects As with the multilayer substrate 100C according to the fourth embodiment, the multilayer substrate 100D according to the fifth embodiment can reduce AC resistance.

[0090] Furthermore, in the multilayer substrate 100D of embodiment 5, the area of ​​the multiple ground electrodes 41 to 44 can be made larger than that of the multilayer substrate 100C of embodiment 4, making it possible to more stabilize the potential of the multiple ground electrodes 41 to 44.

[0091] Sixth Embodiment A multilayer substrate 100E according to a sixth embodiment will be described with reference to Figures 18 to 21. Regarding the multilayer substrate 100E according to the sixth embodiment, components that are the same as those in the multilayer substrate 100C according to the fourth embodiment (see Figures 12 to 14) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 18 to 21, as in Figures 12 to 14, 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 20) is indicated as the Z-axis.

[0092] (1) Configuration In the multilayer substrate 100E according to the sixth embodiment, as shown in FIG. 18 , the outer width W1 of the first transmission line region 101, the outer width W2 of the second transmission line region 102, the outer width W3 of the third transmission line region 103E, and the outer width W4 of the fourth transmission line region 104 are all the same.

[0093] In the multilayer substrate 100E according to the sixth embodiment, the electrode width W44 (see FIG. 20 ) of the ground electrode 44 in the first transmission line region 101 is the same as the electrode width W44 (see FIG. 21 ) of the ground electrode 44 in the second transmission line region 102. In addition, in the multilayer substrate 100E, the width W101 of the ground electrodes 41-44 in the first transmission line region 101, which is located on the opposite side to the signal lines 21-24, is wider than the width W102 of the ground electrodes 41-44 in the second transmission line region 102, which is located on the opposite side to the signal lines 21-24.

[0094] 19 to 21 , the multilayer substrate 100E according to the sixth embodiment further includes an RF signal line 6. The RF signal line 6 is formed on the laminate substrate 1. The RF signal line 6 is disposed across the first transmission line region 101, the second transmission line region 102, and the third transmission line region 103E. The frequency of the high-frequency signal transmitted through the RF signal line 6 is higher (e.g., 2.45 GHz) than the frequency of the signal transmitted through the AC signal line 2 (e.g., 13.56 MHz). The RF signal line 6 is designed, for example, so that the impedance of the RF signal line 6 is 50Ω. As shown in FIGS. 20 and 21 , the RF signal line 6 is located between the first ground electrode 41 and the fourth ground electrode 44 in the thickness direction D1 of the laminate substrate 1. Therefore, in the multilayer substrate 100E, the laminate substrate 1, the RF signal line 6, the first ground electrode 41, and the fourth ground electrode 44 form a strip line. In this embodiment, the second ground electrode 42 is divided into two split ground electrodes 421 and 422 in the width direction of the signal line 22, and the third ground electrode 43 is divided into two split ground electrodes 431 and 432 in the width direction of the signal line 23. In this embodiment, the RF signal line 6 is disposed between the two split ground electrodes 421 and 422.

[0095] In the multilayer substrate 100E, the length directions of the first transmission line region 101 and the second transmission line region 102 are aligned along the Y axis, and the length direction of the third transmission line region 103E is aligned along the X axis. Therefore, in the multilayer substrate 100E, the length directions of the second transmission line region 102 and the third transmission line region 103E are perpendicular to each other.

[0096] The multiple signal lines 21-24 are formed across the first transmission line region 101, the second transmission line region 102, and the third transmission line region 103E. The width direction of the multiple signal lines 21-24 in the first transmission line region 101 is perpendicular to the width direction of the multiple signal lines 21-24 in the third transmission line region 103E. The RF signal line 6 includes a first portion 61 formed in the first transmission line region 101, a second portion 62 formed in the second transmission line region 102, and a third portion 63 formed in the third transmission line region 103E.

[0097] In the multilayer substrate 100E, in a plan view from the thickness direction D1 of the laminated substrate 1, a recess 120 is formed in the outer edge 107 of the laminated substrate 1 at an end of the first transmission line region 101 on the third transmission line region 103E side in the width direction (direction along the X-axis) of the first transmission line region 101. The recess 120 is formed to make it easier to bend the multilayer substrate 100E at the first transmission line region 101. When viewed from the thickness direction D1 of the laminated substrate 1, as shown in FIG. 19 , a first shortest distance L61 between the first portion 61 of the RF signal line 6 and the outer edge 107 of the laminated substrate 1 is longer than a second shortest distance L62 between the second portion 62 of the RF signal line 6 and the outer edge 107 of the laminated substrate 1, and is longer than a third shortest distance L63 between the third portion 63 of the RF signal line 6 and the outer edge 107 of the laminated substrate 1. The first shortest distance L61 is set to a value greater than the depth of the recess 120 so that the first portion 61 of the RF signal line 6 does not overlap with the recess 120 in the direction in which the first transmission line region 101 and the second transmission line region 102 are aligned (the direction parallel to the Y-axis). When viewed in the thickness direction D1 of the laminated substrate 1, the coupling portion 613 between the first portion 61 and the third portion 63 of the RF signal line 6 has a shape that is more gently curved than the outer edge 107 of the laminated substrate 1. In other words, the coupling portion 613 of the RF signal line 6 is curved more gently than if it were bent 180 degrees to go around the recess 120.

[0098] (2) Effects The multilayer substrate 100E according to the sixth embodiment can reduce AC resistance, similar to the multilayer substrate 100C according to the fourth embodiment.

[0099] Moreover, the multilayer substrate 100E according to the sixth embodiment further includes an RF signal line 6.

[0100] According to the above configuration, 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.

[0101] Furthermore, in the multilayer substrate 100E according to the sixth embodiment, when viewed in the thickness direction D1 of the laminated substrate 1, a connecting portion 613 between the first portion 61 of the RF signal line 6 formed in the first transmission line region 101 and the third portion 63 formed in the third transmission line region 103E has a shape that is more gently curved than the outer edge 107 of the laminated substrate 1.

[0102] According to the above configuration, it is possible to suppress the impedance deviation of the RF signal line 6 .

[0103] Seventh Embodiment A multilayer substrate 100F according to a seventh embodiment will be described with reference to Figures 22 to 25. Regarding the multilayer substrate 100F according to the seventh embodiment, components that are the same as those of the multilayer substrate 100E according to the sixth embodiment (see Figures 18 to 21) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 22 to 25, as in Figures 18 to 21, 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 Figure 24) of the multilayer substrate 1 is represented as the Z-axis.

[0104] (1) Configuration The multilayer substrate 100F according to the seventh embodiment differs from the multilayer substrate 100E according to the sixth embodiment in that the multilayer substrate 100F does not include the third transmission line region 103E of the multilayer substrate 100E.

[0105] In the multilayer substrate 100F, the width of the laminated substrate 1 is constant in the width direction of the multiple signal lines 21 to 24. In the multilayer substrate 100F, the area of ​​the conductor in the cross section of the first transmission line region 101 perpendicular to the direction in which the first transmission line region 101 and the second transmission line region 102 are arranged is smaller than the area of ​​the conductor in the cross section of the second transmission line region 102 perpendicular to the direction in which the first transmission line region 101 and the second transmission line region 102 are arranged.

[0106] (2) Effects As with the multilayer substrate 100E according to the sixth embodiment, the multilayer substrate 100F according to the seventh embodiment can reduce AC resistance.

[0107] Furthermore, in the multilayer substrate 100F according to the seventh embodiment, the total cross-sectional area of ​​the signal lines 21 to 24 and the ground electrodes 41 to 44 in the cross section of the first transmission line region 101 perpendicular to the longitudinal direction of the signal lines 21 to 24 is smaller than the total cross-sectional area of ​​the signal lines 21 to 24 and the ground electrodes 41 to 44 in the cross section of the second transmission line region 102 perpendicular to the longitudinal direction of the signal lines 21 to 24.

[0108] According to the above configuration, the multilayer substrate 100F is easier to bend in the first transmission line region 101 than in the second transmission line region 102.

[0109] Eighth Embodiment A multilayer substrate 100G according to an eighth embodiment will be described with reference to Fig. 26. With respect to the multilayer substrate 100G according to the eighth embodiment, components that are the same as those of the multilayer substrate 100F according to the seventh embodiment (see Figs. 22 to 25) are denoted by the same reference numerals, and description thereof will be omitted. In Fig. 26, as in Figs. 22 to 25, Cartesian coordinates having three mutually orthogonal axes, i.e., an X-axis, a Y-axis, and a Z-axis, are defined and expressed.

[0110] (1) Configuration As shown in FIG. 26, the multilayer substrate 100G according to the eighth embodiment differs from the multilayer substrate 100F according to the seventh embodiment in that the first transmission line region 101 is bent.

[0111] The multilayer substrate 100G is bent by plastically deforming the thermoplastic resin in the first transmission line region 101, and the multilayer substrate 100G maintains its shape by itself.

[0112] (2) Effects Similar to the multilayer substrate 100F according to the seventh embodiment, the multilayer substrate 100G according to the eighth embodiment can reduce AC resistance.

[0113] Furthermore, since the multilayer substrate 100G according to the eighth embodiment is curved in the first transmission line region 101, it becomes easier to place the multilayer substrate 100G inside the housing of the electronic device, for example, when the storage space for the multilayer substrate 100G in the housing of the electronic device is a curved space.

[0114] Ninth Embodiment A multilayer substrate 100H according to a ninth embodiment will be described with reference to Figures 27 to 30. Regarding the multilayer substrate 100H according to the ninth embodiment, components that are the same as those of the multilayer substrate 100F according to the seventh embodiment (see Figures 22 to 25) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 27 to 30, as in Figures 22 to 25, 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 29) is indicated as the Z-axis.

[0115] (1) Configuration The multilayer substrate 100H according to the ninth embodiment differs from the multilayer substrate 100F according to the seventh embodiment in that the multilayer substrate 100H further includes a signal line 7 disposed in the first transmission line region 101, as shown in FIGS. 28 and 29 .

[0116] The signal line 7 is located on the opposite side of the second ground electrode 42 from the side of the AC signal line 2. Furthermore, the signal line 7 is located on the opposite side of the split ground electrode 421 of the second ground electrode 42 from the side of the RF signal line 6 in the width direction of the second signal line 22. Therefore, in the multilayer substrate 100H, the second signal line 22, the split ground electrode 421, the RF signal line 6, the split ground electrode 422, and the signal line 7 are arranged in the order of the second signal line 22, the split ground electrode 421, the RF signal line 6, the split ground electrode 422, and the signal line 7 in the direction parallel to the X-axis.

[0117] The signal line 7 transmits a signal different from the signal transmitted through the AC signal line 2. The signal line 7 is, for example, a digital signal line that transmits a digital signal.

[0118] (2) Effects The multilayer substrate 100H according to the ninth embodiment can reduce AC resistance, similar to the multilayer substrate 100F according to the seventh embodiment.

[0119] Furthermore, the multilayer substrate 100H according to the ninth embodiment includes the signal line 7 in addition to the AC signal line 2, and therefore can be used for transmitting signals via the signal line 7 in addition to transmitting signals via the AC signal line 2.

[0120] Tenth Embodiment A multilayer substrate 100I according to a tenth embodiment will be described with reference to Figures 31 to 34. Regarding the multilayer substrate 100I according to the tenth embodiment, components that are the same as those in the multilayer substrate 100B according to the third embodiment (see Figures 9 to 11) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 31 to 34, as in Figures 9 to 11, 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 Figure 32) of the multilayer substrate 1 is indicated as the Z-axis.

[0121] (1) Configuration In the multilayer substrate 100I, the first connecting conductor 31 among the multiple connecting conductors is disposed at an end of the signal line 21 adjacent to one ground electrode 41 at the boundary BL1 between the first transmission line region 101 and the second transmission line region 102. When viewed in the thickness direction D1 of the multilayer substrate 1, as shown in FIG. 34 , the center C1 of the first connecting conductor 31 is within a range from the edge 211 of the signal line 21 to the maximum length LM1 of the first connecting conductor 31. The center C1 of the first connecting conductor 31 is located on a perpendicular line PL1 that is erected on the edge 211 of the signal line 21 and passes through a first point 311 on the first connecting conductor 31 that is closest to the edge 211 of the signal line 21. The distance between the center C1 and a second point 312 on the first connecting conductor 31 that is farthest from the edge 211 of the signal line 21 on the perpendicular line PL1 is the same as the distance between the first point 311 and the center C1. The maximum length LM1 is the length between the first point 311 and the second point 312.

[0122] (2) Effects Similar to the multilayer substrate 100B according to the third embodiment, the multilayer substrate 100I according to the tenth embodiment can reduce AC resistance.

[0123] Furthermore, in the multilayer substrate 100I according to the tenth embodiment, the first connecting conductor 31 among the multiple connecting conductors is disposed at an end of the signal line 21 adjacent to one ground electrode 41 at the boundary BL1 between the first transmission line region 101 and the second transmission line region 102. When viewed in the thickness direction D1 of the multilayer substrate 1, the center C1 of the first connecting conductor 31 is within a range from the edge 211 of the signal line 21 to the maximum length LM1 of the first connecting conductor 31.

[0124] According to the above configuration, the AC signal line 2 can be more effectively utilized in the first transmission line region 101, and the AC resistance can be further reduced.

[0125] Eleventh Embodiment A multilayer substrate 100J according to an eleventh embodiment will be described with reference to Figures 35 to 37. Regarding the multilayer substrate 100J according to the eleventh embodiment, components that are the same as those in the multilayer substrate 100 according to the first embodiment (see Figures 1 to 4) are denoted by the same reference numerals, and descriptions thereof will be omitted. In each of Figures 35 to 37, as in Figures 1 to 4, 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 36) is indicated as the Z-axis.

[0126] (1) Configuration A multilayer substrate 100J according to the eleventh embodiment differs from the multilayer substrate 100 according to the first embodiment in that the thickness T1 (see FIG. 36 ) of the first transmission line region 101 in the thickness direction D1 of the laminated substrate 1 is different from the thickness T2 (see FIG. 37 ) of the second transmission line region 102 in the thickness direction D1 of the laminated substrate 1. In this embodiment, the thickness T1 (see FIG. 36 ) of the first transmission line region 101 in the thickness direction D1 of the laminated substrate 1 is smaller than the thickness T2 (see FIG. 37 ) of the second transmission line region 102 in the thickness direction D1 of the laminated substrate 1.

[0127] In the multilayer substrate 100J, the thickness of the laminated substrate 1 is different between the first transmission line region 101 and the second transmission line region 102. In the first transmission line region 101, the laminated substrate 1 has a layered structure of four insulating layers 11 to 14, whereas in the second transmission line region 102, the laminated substrate 1 has a layered structure of five insulating layers 11 to 15. Insulating layer 15 is laminated on insulating layer 14. The material of insulating layer 15 is the same as the material of insulating layers 11 to 14. The second transmission line region 102 of the multilayer substrate 100I also includes a signal line 25 and a ground electrode 45 disposed on insulating layer 15. The second transmission line region 102 also includes a connecting conductor 35 connecting the signal line 25 and the signal line 24, and a connecting conductor 55 connecting the ground electrode 45 and the ground electrode 44. The material of the signal line 25 is, for example, the same as the material of the other signal lines 21 to 24. In a plan view from the thickness direction D1 of the laminated substrate 1, the multiple signal lines 21, 22, 23, 24, and 25 overlap one another. The signal line 25 has a line width W25. The material of the connecting conductor 35 is, for example, the same as the material of the first connecting conductor 31 to the fourth connecting conductor 34. The material of the ground electrode 45 is, for example, the same as the material of the other ground electrodes 41 to 44. In a plan view from the thickness direction D1 of the laminated substrate 1, the multiple ground electrodes 41, 42, 43, 44, and 45 overlap one another. The ground electrode 45 has an electrode width W45. The material of the connecting conductor 55 is, for example, the same as the material of the fifth connecting conductor 51 to the eighth connecting conductor 54.

[0128] (2) Effects As with the multilayer substrate 100 according to the first embodiment, the multilayer substrate 100J according to the eleventh embodiment can reduce AC resistance.

[0129] In the multilayer substrate 100J according to the eleventh embodiment, the thickness T1 of the first transmission line region 101 in the thickness direction D1 of the laminated substrate 1 is smaller than the thickness T2 of the second transmission line region 102 in the thickness direction D1 of the laminated substrate 1.

[0130] According to the above configuration, the multilayer substrate 100J can be easily bent at the first transmission line region 101.

[0131] The above-described first to eleventh embodiments are merely examples of various embodiments of the present invention. The above-described first to eleventh embodiments 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.

[0132] For example, the material of each of the multiple insulating layers 11 to 14 may be polyimide. In this case, each of the multiple first connecting conductors 31, the multiple second connecting conductors 32, the multiple third connecting conductors 33, the multiple fourth connecting conductors 34, the multiple fifth connecting conductors 51, the multiple sixth connecting conductors 52, the multiple seventh connecting conductors 53, and the multiple eighth connecting conductors 54 may be formed by through-hole plating. Furthermore, the first connecting conductor 31 and the second connecting conductor 32, which are connected to each other, may be formed by a single through-hole plating, and the fifth connecting conductor 51 and the sixth connecting conductor 52, 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 laminate substrate 1 may include an adhesive layer interposed between two adjacent insulating layers of the multiple insulating layers 11 to 14 in the thickness direction D1 of the laminate substrate 1.

[0133] Similarly to multilayer substrate 100G, multilayer substrates 100, 100A to 100F, and 100H to 100J may be curved in first transmission line region 101. Multilayer substrates 100, 100A to 100J may be curved in second transmission line region 102.

[0134] Furthermore, in the multilayer substrates 100 and 100A to 100I, similar to the multilayer substrate 100J, the thickness of the first transmission line region 101 in the thickness direction D1 of the laminated substrate 1 may be thinner than the thickness of the second transmission line region 102 in the thickness direction D1 of the laminated substrate 1. Furthermore, in the multilayer substrates 100 and 100A to 100I, the thickness of the second transmission line region 102 may be thinner than the thickness of the first transmission line region 101.

[0135] Furthermore, the multilayer substrate 100, 100A to 100J may be curved in the second transmission line region .

[0136] Furthermore, the multilayer substrates 100, 100A-100J may further include at least one of a first cover layer disposed on one main surface of the laminate substrate 1 and a second cover layer disposed on the other main surface of the laminate substrate 1. Each of the first cover layer and the second cover layer 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-100J do not have any bent portions, each of the first cover layer and the second cover layer is not limited to a configuration including a polyimide film and an adhesive layer, and may be, for example, a resist layer. The resist layer can be formed using, for example, spin coating and photolithography.

[0137] (Aspects) The present specification discloses the following aspects.

[0138] A multilayer substrate (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G; 100H; 100I; 100J) according to a first aspect includes a laminated substrate (1), an AC signal line (2), and a plurality of ground electrodes (41-44). The laminated substrate (1) has a plurality of insulating layers (11-14) stacked one on top of the other. The AC signal line (2) is formed on the laminated substrate (1). The AC signal line (2) has a plurality of signal lines (21-24) spaced apart from one another in a thickness direction (D1) of the laminated substrate (1), and the plurality of signal lines (21-24) are electrically connected by a plurality of connecting conductors that penetrate at least one of the insulating layers (11-14) in the thickness direction (D1). The plurality of ground electrodes (41-44) are formed on the laminated substrate (1). The ground electrodes (41 to 44) are spaced apart from one another in the thickness direction (D1) and adjacent to the signal lines (21 to 24) in the width direction of the signal lines (21 to 24). In a first transmission line region (101) in which the maximum line widths of the signal lines (21 to 24) are smallest, the signal lines (21 to 24) do not overlap with any of the ground electrodes (41 to 44) in the thickness direction (D1). In a second transmission line region (102) in which the maximum line widths of the signal lines (21 to 24) are large, one ground electrode (41) of the ground electrodes (41 to 44) overlaps with a signal line (22 to 24) other than the signal line (21) adjacent to the one ground electrode (41) of the signal lines (21 to 24).

[0139] According to this aspect, it is possible to reduce AC resistance.

[0140] A multilayer substrate (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G; 100H; 100I; 100J) according to a second aspect is based on the first aspect. In the second transmission line region (102), a signal line (22) among the plurality of signal lines (21-24) that is adjacent to one ground electrode (41) in the thickness direction (D1) has an area of ​​more than half of its width overlapping with the one ground electrode (41) in the thickness direction (D1).

[0141] According to this aspect, the bias in current density in the width direction of the signal lines (22 to 24) can be further reduced, and the AC resistance can be further reduced, compared to when less than half of the area in the width direction of the signal line (22) in the thickness direction (D1) of the laminated substrate (1) overlaps with one ground electrode (41).

[0142] A multilayer substrate (100B) according to a third aspect is based on the first aspect. In the second transmission line region (102), a signal line (22) among a plurality of signal lines (21 to 24) adjacent to one ground electrode (41) in the thickness direction (D1) overlaps the ground electrode (41) over its entire region in the thickness direction (D1).

[0143] According to this aspect, it is possible to improve noise resistance.

[0144] In a multilayer substrate (100C; 100D) according to a fourth aspect, in any one of the first to third aspects, when the maximum line width in the first transmission line region (101) is X1 and the maximum line width in the second transmission line region (102) is X2, in a third transmission line region (103) in which the maximum line width of the plurality of signal lines (21 to 24) is greater than X1 and not greater than (X1 + X2) / 2, the plurality of signal lines (21 to 24) do not overlap with any of the plurality of ground electrodes (41 to 44) in the thickness direction (D1).

[0145] According to this aspect, when the AC signal line (2) is formed across the first transmission line region (101), the second transmission line region (102), and the third transmission line region (103), it is possible to reduce the AC resistance.

[0146] In a multilayer substrate (100C) according to a fifth aspect, in any one of the first to fourth aspects, the outer width (W1) in the width direction of the plurality of signal lines (21 to 24) in the first transmission line region (101) is the same as the outer width (W2) in the width direction of the plurality of signal lines (21 to 24) in the second transmission line region (102).

[0147] In a multilayer substrate (100; 100A; 100B; 100D; 100E; 100F; 100G; 10H; 100I; 100J) according to a sixth aspect, in any one of the first to fourth aspects, the outer width (W2) in the width direction of the plurality of signal lines (21 to 24) in the second transmission line region (102) is wider than the outer width (W1) in the width direction of the plurality of signal lines (21 to 24) in the first transmission line region (101).

[0148] According to this aspect, it is possible to further reduce the AC resistance in each of the first transmission line region (101) and the second transmission line region (102) of the AC signal line (2).

[0149] A multilayer substrate (100) according to a seventh aspect is any one of the first to fourth aspects, in which the total cross-sectional area of ​​the plurality of signal lines (21 to 24) and the plurality of ground electrodes (41 to 44) in a cross section of the first transmission line region (101) perpendicular to the longitudinal direction of the plurality of signal lines (21 to 24) is smaller than the total cross-sectional area of ​​the plurality of signal lines (21 to 24) and the plurality of ground electrodes (41 to 44) in a cross section of the second transmission line region (102) perpendicular to the longitudinal direction of the plurality of signal lines (21 to 24).

[0150] According to this aspect, the multilayer substrate (100) is easier to bend in the first transmission line region (101) than in the second transmission line region (102).

[0151] The multilayer substrate (100G) according to the eighth aspect is the same as any one of the first to seventh aspects, except that the first transmission line region (101) is curved.

[0152] In a multilayer substrate (100; 100A; 100B; 100C; 100D) according to a ninth aspect, in any one of the first to eighth aspects, the material of each of the plurality of insulating layers (11 to 14) includes a thermoplastic resin.

[0153] According to this aspect, it is possible to improve the bendability of the multilayer substrate (100; 100A; 100B; 100C; 100D).

[0154] A multilayer substrate (100E; 100F; 100G; 100H) according to a tenth aspect is any one of the first to ninth aspects, further comprising an RF signal line (6). The RF signal line (6) is formed on the multilayer substrate (1). The RF signal line (6) is arranged across the first transmission line region (101) and the second transmission line region (102).

[0155] According to this embodiment, it is possible to use the RF signal line (6) for transmitting high frequency signals in addition to transmitting signals via the AC signal line (2).

[0156] A multilayer substrate (100E) according to an eleventh aspect is any one of the first to third aspects, further comprising a third transmission line region (103E) located on the opposite side of the first transmission line region (101) from the second transmission line region (102), and an RF signal line (6) formed on the laminated substrate (1). The multiple signal lines (21-24) are formed across the first transmission line region (101), the second transmission line region (102), and the third transmission line region (103E). The width direction of the multiple signal lines (21-24) in the first transmission line region (101) is orthogonal to the width direction of the multiple signal lines (21-24) in the third transmission line region (103E). The RF signal line (6) includes a first portion (61) formed in the first transmission line region (101), a second portion (62) formed in the second transmission line region (102), and a third portion (63) formed in the third transmission line region (103E). When viewed in the thickness direction (D1) of the laminated substrate (1), a connecting portion (613) between the first portion (61) and the third portion (63) in the RF signal line (6) has a shape that is more gently curved than the outer edge of the laminated substrate (1).

[0157] According to this aspect, it is possible to suppress deviation in impedance of the RF signal line (6).

[0158] A multilayer substrate (100H) according to a twelfth aspect is any one of the first to eleventh aspects, further comprising a signal line (7). The signal line (7) is arranged only in the first transmission line region (101) of the first transmission line region (101) and the second transmission line region (102).

[0159] According to this embodiment, it is possible to use the signal line (7) for transmitting a different signal in addition to transmitting a signal through the AC signal line (2).

[0160] In a multilayer substrate (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G; 100H; 100I; 100J) according to a thirteenth aspect, in any one of the first to twelfth aspects, among the plurality of connecting conductors, a connecting conductor (first connecting conductor 31) arranged on a signal line (21) adjacent to one ground electrode (41) across a boundary (BL1) between a first transmission line region (101) and a second transmission line region (102) is arranged at an end of the signal line (21) adjacent to one ground electrode (41). When viewed from the thickness direction (D1) of the laminated substrate (1), the center (C1) of the connecting conductor (first connecting conductor 31) arranged on the signal line (21) adjacent to one ground electrode (41) is within a range from the edge (211) of the signal line (21) adjacent to one ground electrode (41) to the maximum length (LM1) of the connecting conductor (first connecting conductor 31).

[0161] According to this aspect, the AC signal line (2) can be more effectively utilized in the first transmission line region (101), and the AC resistance can be further reduced.

[0162] In the multilayer substrate (100J) according to the fourteenth aspect, in any one of the first to thirteenth aspects, the thickness (T1) of the first transmission line region (101) in the thickness direction (D1) of the laminated substrate (1) is different from the thickness (T2) of the second transmission line region (102) in the thickness direction (D1) of the laminated substrate (1).

[0163] According to this aspect, it is possible to improve the bendability of the thinner of the first transmission line region (101) and the second transmission line region (102) in the multilayer substrate (100J).

[0164] REFERENCE SIGNS LIST 1 laminated substrate 11, 12, 13, 14, 15 insulating layer 2 AC signal line 21, 22, 23, 24, 25 signal line 31 first connecting conductor 32 second connecting conductor 33 third connecting conductor 34 fourth connecting conductor 41, 42, 43, 44, 45 ground electrode 51 fifth connecting conductor 52 sixth connecting conductor 53 seventh connecting conductor 54 eighth connecting conductor 6 RF signal line 61 first portion 62 second portion 63 third portion 613 coupling portion 7 signal line 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H, 100I, 100J multilayer substrate 101 first transmission line region 102 second transmission line region 103 third transmission line region 103E Third transmission line region C1 Center D1 Thickness direction LM1 Maximum length W1 Outer width W2 Outer width W21, W22, W23, W24, W25 Line width

Claims

1. A multilayer substrate comprising: a laminated substrate having a plurality of insulating layers stacked on top of one another; an AC signal line formed on the laminated substrate, the AC signal line having a plurality of signal lines spaced apart from one another in a thickness direction of the laminated substrate, the signal lines being electrically connected by a plurality of connecting conductors that penetrate one of the insulating layers in the thickness direction; and a plurality of ground electrodes formed on the laminated substrate, the AC signal line having a plurality of signal lines spaced apart from one another in the thickness direction and adjacent to the signal lines in a width direction of the signal lines, the plurality of signal lines not overlapping any of the plurality of ground electrodes in the thickness direction in a first transmission line region in which the maximum line width of the plurality of signal lines is smallest; and in a second transmission line region in which the maximum line width of the plurality of signal lines is large, one of the plurality of ground electrodes overlapping with a signal line of the plurality of signal lines other than the signal line adjacent to the one ground electrode.

2. The multilayer board according to claim 1, wherein in the second transmission line region, of the plurality of signal lines, a signal line adjacent to the one ground electrode in the thickness direction has an area of ​​more than half of its width overlapping with the one ground electrode in the thickness direction.

3. The multilayer board according to claim 1, wherein in the second transmission line region, of the plurality of signal lines, a signal line adjacent to the one ground electrode in the thickness direction has an entire region overlapping with the one ground electrode in the thickness direction.

4. The multilayer board according to any one of claims 1 to 3, wherein, when the maximum line width in the first transmission line region is X1 and the maximum line width in the second transmission line region is X2, in a third transmission line region where the maximum line width of the multiple signal lines is greater than X1 and not greater than (X1 + X2) / 2, the multiple signal lines do not overlap any of the multiple ground electrodes in the thickness direction.

5. A multilayer board according to any one of claims 1 to 4, wherein an outer width in the width direction of the plurality of signal lines in the first transmission line region is the same as an outer width in the width direction of the plurality of signal lines in the second transmission line region.

6. A multilayer board according to any one of claims 1 to 4, wherein an outer width in the width direction of the plurality of signal lines in the second transmission line region is wider than an outer width in the width direction of the plurality of signal lines in the first transmission line region.

7. The multilayer board according to any one of claims 1 to 4, wherein a total cross-sectional area of ​​the signal lines and the ground electrodes in a cross section of the first transmission line region perpendicular to the longitudinal direction of the signal lines is smaller than a total cross-sectional area of ​​the signal lines and the ground electrodes in a cross section of the second transmission line region perpendicular to the longitudinal direction of the signal lines.

8. The multilayer board according to any one of claims 1 to 7, wherein the first transmission line region is bent.

9. The multilayer board according to any one of claims 1 to 8, wherein the material of each of the plurality of insulating layers includes a thermoplastic resin.

10. The multilayer board according to any one of claims 1 to 9, further comprising an RF signal line formed on the laminated board, the RF signal line being disposed across the first transmission line region and the second transmission line region.

11. The multilayer board according to any one of claims 1 to 3, further comprising: a third transmission line region located on the opposite side of the first transmission line region to the second transmission line region; and an RF signal line formed on the laminated board, wherein the multiple signal lines are formed across the first transmission line region, the second transmission line region, and the third transmission line region, the width direction of the multiple signal lines in the first transmission line region and the width direction of the multiple signal lines in the third transmission line region are perpendicular to each other, the RF signal line includes a first portion formed in the first transmission line region, a second portion formed in the second transmission line region, and a third portion formed in the third transmission line region, and when viewed in the thickness direction of the laminated board, a connecting portion of the first portion and the third portion of the RF signal line has a shape that is more gently curved than an outer edge of the laminated board.

12. The multilayer board according to any one of claims 1 to 11, further comprising a signal line arranged only in the first transmission line region out of the first transmission line region and the second transmission line region.

13. A multilayer board as claimed in any one of claims 1 to 12, wherein among the multiple connection conductors, a connection conductor arranged on the signal line adjacent to the one ground electrode across the boundary between the first transmission line region and the second transmission line region is arranged at an end of the signal line adjacent to the one ground electrode, and when viewed in the thickness direction of the laminated board, a center of the connection conductor arranged on the signal line adjacent to the one ground electrode is within a range from an edge of the signal line adjacent to the one ground electrode to a maximum length of the connection conductor.

14. The multilayer board according to any one of claims 1 to 13, wherein a thickness of the first transmission line region in the thickness direction of the laminated board is different from a thickness of the second transmission line region in the thickness direction of the laminated board.

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