substrate

Abstract

A substrate is provided that can improve EMI performance while avoiding degradation of communication performance. [Solution] In a plan view of the substrate 1, a first transmission line 11 and a second transmission line 21 extend along the longitudinal direction of the substrate 1 while intersecting each other. In a plan view of the substrate 1, as the distance between a central portion 11a of the first transmission line 11 and a central portion 21a of the second transmission line 21 in the width direction of the substrate 1, which is perpendicular to the longitudinal direction of the substrate 1, increases, the widths of the first transmission line 11 and the second transmission line 21 increase.

Description

[Technical Field]

[0001] The present invention relates to a substrate. [Background technology]

[0002] 2. Description of the Related Art Conventionally, techniques for suppressing radiation noise in order to improve EMI (Electro Magnetic Interference) performance in a substrate have been known.

[0003] In the technology disclosed in Patent Document 1, a pair of transmission lines are formed in a serpentine shape on different layers within a substrate. In a plan view of the substrate, the pair of transmission lines extend in a predetermined direction while crossing each other.

[0004] With this configuration, in a plan view of the substrate, an area surrounded by one transmission line and the other transmission line is formed between two adjacent points where the pair of transmission lines intersect.

[0005] When currents flow in opposite directions through one transmission line and the other, a magnetic field is generated in each region in a direction perpendicular to the surface of the substrate. However, in adjacent regions, the direction of the magnetic field generated in one region is opposite to the direction of the magnetic field generated in the other region, so these magnetic fields cancel each other out.

[0006] This makes it possible to suppress radiation noise generated on the board. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-142293 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the substrate disclosed in Patent Document 1, the positional relationship between one transmission line and the other transmission line changes along the direction in which the pair of transmission lines extend, resulting in many locations where the impedances are not matched within the pair of transmission lines, which may result in a degradation of communication performance.

[0009] Therefore, further improvements are desired in order to improve EMI performance while avoiding degradation of communication performance in the board.

[0010] The present invention has been made in view of the problems inherent in the conventional technology, and an object of the present invention is to provide a substrate that can improve EMI performance while avoiding degradation of communication performance. [Means for solving the problem]

[0011] A substrate according to an aspect of the present invention includes a dielectric layer having a first surface and a second surface, on which a pair of transmission lines are formed, a first conductor layer laminated on the first surface of the dielectric layer and having a first transmission line formed in a meandering shape, and a second conductor layer laminated on the second surface of the dielectric layer and having a second transmission line formed in a meandering shape. In a plan view of the substrate, the first transmission line and the second transmission line extend along a first direction while intersecting each other. In a plan view of the substrate, as the distance between a center portion of the first transmission line and a center portion of the second transmission line in a second direction orthogonal to the first direction increases, the widths of the first transmission line and the second transmission line increase. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a substrate that can improve EMI performance while avoiding degradation of communication performance. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a substrate according to this embodiment. [Figure 2]FIG. 2 is a plan view of the substrate according to this embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the substrate according to this embodiment taken along line IV-IV in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the substrate according to this embodiment taken along line VV in FIG. [Figure 5A] FIG. 5A is a plan view of the first transmission line according to this embodiment. [Figure 5B] FIG. 5B is a plan view of the second transmission line according to this embodiment. [Figure 6] FIG. 6 is a block diagram showing an example of the functional configuration of the calculation device according to this embodiment. [Figure 7] FIG. 7 is a block diagram showing an example of the hardware configuration of the calculation device according to this embodiment. [Figure 8] FIG. 8 is a diagram showing an example of the operation flow of the calculation device according to this embodiment. [Figure 9] FIG. 9 is a plan view of a substrate according to a comparative example. [Figure 10] FIG. 10 is a diagram comparing the radiation characteristics of a parallel line, a paired line according to a comparative example, and a paired line according to this embodiment. [Figure 11] FIG. 11 is a diagram comparing other radiation characteristics among a parallel line, a paired line according to a comparative example, and a paired line according to this embodiment. [Figure 12] FIG. 12 is a diagram comparing the transmission characteristics of a parallel line, a paired line according to a comparative example, and a paired line according to this embodiment. [Figure 13] FIG. 13 is a diagram comparing other transmission characteristics among a parallel line, a paired line according to a comparative example, and a paired line according to this embodiment. [Figure 14] FIG. 14 is a plan view of a substrate according to a modified example of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] The substrate according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions. Furthermore, the same or similar reference numerals are used to designate the same functions or configurations, and their description will be omitted as appropriate.

[0015] [Overall board configuration] First, the overall configuration of the substrate 1 according to this embodiment will be described. Fig. 1 is a perspective view of the substrate 1. Fig. 2 is a plan view of the substrate 1. Fig. 3 is a cross-sectional view of the substrate 1 taken along line IV-IV in Fig. 2. Fig. 4 is a cross-sectional view of the substrate 1 taken along line VV in Fig. 2.

[0016] The X direction shown in Figures 1 to 4 corresponds to the longitudinal direction of the substrate 1. The Y direction shown in Figures 1 to 4 corresponds to the width direction of the substrate 1 and is perpendicular to the X direction. The Z direction shown in Figures 1 to 4 corresponds to the height direction of the substrate 1 and is perpendicular to the X and Y directions.

[0017] The X direction and the Y direction are also referred to as the first direction and the second direction, respectively. The Z direction is also referred to as the stacking direction of the substrate 1. Furthermore, the longitudinal direction and the width direction of the substrate 1 are not limited to the X direction and the Y direction, respectively, and may be directions different from the X direction and the Y direction.

[0018] 1 to 4, the substrate 1 is a two-layer substrate, and includes a dielectric layer 3, a conductor layer 5, and a conductor layer 7. The substrate 1 is not limited to a two-layer substrate, and may be a substrate with three or more layers.

[0019] The dielectric layer 3 is made of FR-4 (glass cloth epoxy resin) and has a first surface 3a and a second surface 3b. The first surface 3a and the second surface 3b face one side and the other side in the Z direction, respectively. The first surface 3a and the second surface 3b are also referred to as the front and back surfaces of the substrate 1, respectively.

[0020] The conductor layer 5 is made of tin-plated copper foil and is laminated on the first surface 3a of the dielectric layer 3. The conductor layer 5 has a first transmission line 11 formed in a meandering shape. No ground layer is disposed outside the conductor layer 5. The conductor layer 5 is also referred to as the first conductor layer.

[0021] The conductor layer 7 is made of tin-plated copper foil and is laminated on the second surface 3b of the dielectric layer 3. The conductor layer 7 has a second transmission line 21 formed in a meandering shape. No ground layer is disposed outside the conductor layer 7. The conductor layer 7 is also referred to as the second conductor layer.

[0022] 1 and 2, the second transmission line 21 is arranged on the second surface 3b (back surface) of the dielectric layer 3 and is therefore hidden by the dielectric layer 3, but the second transmission line 21 is shown by a dotted line to clarify the positional relationship between the first transmission line 11 and the second transmission line 21 on the substrate 1.

[0023] In a plan view of the substrate 1, the first transmission line 11 and the second transmission line 21 extend along the X direction while intersecting each other at a fixed interval. With this configuration, the first transmission line 11 and the second transmission line 21 form a pair line 31. Note that "plan view of the substrate 1" can also be expressed as "viewed from a direction (Z direction) perpendicular to the surface direction (XY plane) of the substrate 1." The pair line 31 is also referred to as a pair of transmission lines.

[0024] In the substrate 1, currents (differential signals) flow in opposite directions through the first transmission line 11 and the second transmission line 21. For this reason, the pair line 31 is also called a differential pair line. Note that in the substrate 1, the first transmission line 11 and the second transmission line 21 may be used as a signal line and a return path for the signal line, respectively.

[0025] In a plan view of the substrate 1, the pair line 31 has a plurality of crossing portions 32 where the first transmission line 11 and the second transmission line 21 cross each other. The crossing portions 32 are also referred to as points where the first transmission line 11 and the second transmission line 21 cross each other.

[0026] In the pair line 31, the distance P between adjacent intersections 32, 32 is a constant value. The shape of the pair line 31 changes periodically at a distance 2P. The distance 2P is also called one period or one pitch. The adjacent intersections 32, 32 are also called two adjacent points where the first transmission line 11 and the second transmission line 21 intersect with each other.

[0027] In a plan view of the substrate 1, the distance between the first transmission line 11 and the second transmission line 21 in the width direction (Y direction) of the substrate 1 varies along the longitudinal direction (X direction) of the substrate 1. Specifically, the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 in the width direction (Y direction) of the substrate 1 is smallest at each intersection portion 32. Furthermore, the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 in the width direction (Y direction) of the substrate 1 is largest at a central portion 33 between adjacent intersection portions 32, 32 (a position a distance P / 2 away from each intersection portion 32).

[0028] For example, as shown in Figures 3 and 4, the distance T1 between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 in the vicinity of the central portion 33 between adjacent intersection portions 32, 32 is greater than the distance T2 between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 in the vicinity of the intersection portion 32.

[0029] In a plan view of the substrate 1, the widths of the first transmission line 11 and the second transmission line 21 vary along the longitudinal direction (X direction) of the substrate 1. Specifically, the widths of the first transmission line 11 and the second transmission line 21 are minimum at each intersection 32. Furthermore, the widths of the first transmission line 11 and the second transmission line 21 are maximum at a central portion 33 between adjacent intersections 32, 32 (a position a distance P / 2 away from each intersection 32).

[0030] For example, as shown in FIGS. 3 and 4, the width W1 of the first transmission line 11 and the width W1 of the second transmission line 21 near the central portion 33 between adjacent intersection portions 32, 32 are larger than the width W2 of the first transmission line 11 and the width W2 of the second transmission line 21 near the intersection portion 32.

[0031] Thus, in the pair line 31, as the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 increases, the width of the first transmission line 11 and the width of the second transmission line 21 increase.

[0032] [Configuration of the first transmission line] Next, the configuration of the first transmission line 11 will be described. Fig. 5A is a plan view of the first transmission line 11. As shown in Fig. 5A, in a plan view of the substrate 1, the first transmission line 11 has a first side portion 11b and a second side portion 11c. The width of the first transmission line 11 corresponds to the distance between the first side portion 11b and the second side portion 11c in the width direction (Y direction) of the substrate 1.

[0033] The width of the first transmission line 11 varies along the longitudinal direction (X direction) of the substrate 1. Specifically, the first transmission line 11 has a minimum portion 12 where the width of the first transmission line 11 is minimum at an intersection 32 of the pair lines 31. The first transmission line 11 has a maximum portion 13 where the width of the first transmission line 11 is maximum at a central portion 33 of the pair lines 31.

[0034] In a plan view of the substrate 1, between adjacent intersection portions 32, 32 (i.e., minimum portions 12, 12) of the pair line 31, the first transmission line 11 is formed symmetrically with respect to the central portion 33 (i.e., maximum portion 13) of the pair line 31 as the center.

[0035] In the first transmission line 11, the position of the arc-shaped region R1 between adjacent crossing portions 32, 32 (i.e., minimum portions 12, 12) of the pair line 31 is reversed in the width direction (Y direction) of the substrate 1 at intervals of a distance P. Therefore, the shape of the first transmission line 11 changes periodically at intervals of a distance 2P.

[0036] [Configuration of the second transmission line] Next, the configuration of the second transmission line 21 will be described. Fig. 5B is a plan view of the second transmission line 21. As shown in Fig. 5B, in a plan view of the substrate 1, the second transmission line 21 has a first side portion 21b and a second side portion 21c. The width of the second transmission line 21 corresponds to the distance between the first side portion 21b and the second side portion 21c in the width direction (Y direction) of the substrate 1.

[0037] The width of the second transmission line 21 varies along the longitudinal direction (X direction) of the substrate 1. Specifically, the second transmission line 21 has a minimum portion 22 where the width of the second transmission line 21 is minimum at an intersection portion 32 of the paired lines 31. The second transmission line 21 has a maximum portion 23 where the width of the second transmission line 21 is maximum at a central portion 33 of the paired lines 31.

[0038] In a plan view of the substrate 1, between adjacent intersection portions 32, 32 (i.e., minimum portions 22, 22) of the pair line 31, the second transmission line 21 is formed symmetrically with respect to the central portion 33 (i.e., maximum portion 23) of the pair line 31 as the center.

[0039] In the second transmission line 21, the position of the arc-shaped region R2 between adjacent crossing portions 32, 32 (i.e., minimum portions 22, 22) of the pair line 31 is reversed in the width direction (Y direction) of the substrate 1 at intervals of a distance P. Therefore, the shape of the second transmission line 21 changes periodically at intervals of a distance 2P.

[0040] With this configuration, between adjacent intersections 32, 32 of the pair line 31, the position of the arc-shaped region R1 of the first transmission line 11 and the position of the arc-shaped region R2 of the second transmission line 21 are inverted relative to each other in the width direction (Y direction) of the substrate 1 (see Figure 2).

[0041] [Functional configuration of the calculation device] Next, the functional configuration of the calculation device 50 will be described. The calculation device 50 calculates the width of the first transmission line 11 and the width of the second transmission line 21 at a plurality of calculation target positions along the longitudinal direction (X direction) of the substrate 1 so that the impedance value of the pair line 31 is constant. The calculation device 50 is connected to a manufacturing device 120 that manufactures the substrate 1, and outputs information required to manufacture the pair line 31 to the manufacturing device 120. Note that the calculation device 50 may be incorporated into the manufacturing device 120 as a part of the manufacturing device 120.

[0042] 6 is a block diagram showing an example of the functional configuration of the calculation device 50. As shown in FIG. 6, the calculation device 50 includes a control unit 51, a storage unit 53, a display unit 55, an input unit 57, an output unit 59, and a calculation unit 61.

[0043] The control unit 51 controls the overall processing in the calculation device 50. Specifically, the control unit 51 controls the operations of the storage unit 53, the display unit 55, the input unit 57, the output unit 59, and the calculation unit 61.

[0044] The storage unit 53 stores data and a program required for the calculation unit 61 to calculate the width of the first transmission line 11 and the width of the second transmission line 21. In this embodiment, the storage unit 53 stores electromagnetic field simulation software as the program. Note that the calculation device 50 may access a server via a network and use the electromagnetic field simulation software stored in the server without storing the electromagnetic field simulation software.

[0045] The display unit 55 displays various input values ​​input to the input unit 57, the width of the first transmission line 11 and the width of the second transmission line 21 calculated by the calculation unit 61, and the like.

[0046] The input unit 57 inputs the number of positions to be calculated in the region from the intersection 32 of the paired lines 31 to the center 33 of the paired lines 31. The input unit 57 inputs the number of adjacent intersections 32, 32 in the paired lines 31.

[0047] In this embodiment, the number of positions to be calculated in the region from the intersection 32 of the paired lines 31 to the center portion 33 of the paired lines 31 is n. In this embodiment, the number of adjacent intersections 32, 32 in the paired lines 31 is m.

[0048] The input unit 57 inputs a set value for the impedance of the pair line 31. The input unit 57 inputs a set value for the height of the first transmission line 11 and a set value for the height of the second transmission line 21 at each position to be calculated along the longitudinal direction (X direction) of the substrate 1. The input unit 57 inputs a distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 at each position to be calculated along the longitudinal direction (X direction) of the substrate 1. The input unit 57 inputs a relative dielectric constant of the dielectric layer 3.

[0049] In this embodiment, the set value of the impedance is 100Ω. In this embodiment, the height of the first transmission line 11 and the height of the second transmission line 21 do not change along the longitudinal direction (X direction) of the substrate 1, and are set to predetermined set values.

[0050] As will be described later, the output unit 59 outputs information about the shape of the first transmission line 11 and the shape of the second transmission line 21 in the pair line 31, which information has been determined by the calculation unit 61, to the manufacturing device 120. The manufacturing device 120 starts manufacturing the substrate 1 based on the information about the shape of the first transmission line 11 and the shape of the second transmission line 21 in the pair line 31.

[0051] The calculation unit 61 uses electromagnetic field simulation software stored in the memory unit 53 to calculate the width of the first transmission line 11 and the width of the second transmission line 21 at each calculation target position along the longitudinal direction (X direction) of the substrate 1 based on various setting values ​​input to the input unit 57.

[0052] Here, the two lines (copper wires) have a relative dielectric constant ε rIn a configuration in which the two lines face each other with a dielectric between them, according to equation (1), the impedance Z0 tends to increase as the distance S between the centers of the two lines increases, and the impedance Z0 tends to decrease as the diameter D of each line increases.

[0053]

number

[0054] Therefore, in the paired line 31, as the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 increases, an increase in impedance can be suppressed by increasing the width of the first transmission line 11 and the width of the second transmission line 21. Similarly, in the paired line 31, as the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 decreases, a decrease in impedance can be suppressed by narrowing the width of the first transmission line 11 and the width of the second transmission line 21.

[0055] For example, the "2D Extractor Design" in the commercially available electromagnetic field simulation software "ANSYS Electronics Desktop" can calculate impedance by analyzing the cross-sectional structure of a pair line using the finite element method.

[0056] The calculation unit 61 sets n positions to be calculated in a region from the intersection 32 of the paired lines 31 to the center 33 of the paired lines 31. The calculation unit 61 calculates the width of the first transmission line 11 and the width of the second transmission line 21 at each of the first to nth calculation positions.

[0057] The calculation unit 61 determines the cross-sectional shapes of the first transmission line 11 and the second transmission line 21 at the ith (1≦i≦n) calculation target position using the calculated widths of the first transmission line 11 and the second transmission line 21 at the ith (1≦i≦n) calculation target position and the set values ​​of the heights of the first transmission line 11 and the second transmission line 21. In this embodiment, the first transmission line 11 and the second transmission line 21 have rectangular cross sections. In this embodiment, the cross sections of the first transmission line 11 and the second transmission line 21 are cross sections cut along a plane parallel to the stacking direction of the substrate 1.

[0058] After determining the cross-sectional shapes of the first transmission line 11 at the first to nth calculation target positions, the calculation unit 61 interpolates between the cross-sectional shape at the jth (1≦j≦n−1) calculation target position and the cross-sectional shape at the j+1th calculation target position on the first transmission line 11 to connect adjacent cross-sectional shapes. In this way, the calculation unit 61 determines the shape of the first transmission line 11 in a region equivalent to ¼ of the period of the pair line 31.

[0059] Similarly, after determining the cross-sectional shapes of the second transmission line 21 at the first to nth calculation target positions, the calculation unit 61 interpolates between the cross-sectional shape at the jth (1≦j≦n−1) calculation target position and the cross-sectional shape at the j+1th calculation target position on the second transmission line 21 to connect adjacent cross-sectional shapes. In this way, the calculation unit 61 determines the shape of the second transmission line 21 in a region equivalent to ¼ of the period of the pair line 31.

[0060] The calculation unit 61 moves the shapes of the first transmission line 11 and the second transmission line 21 in an area of ​​¼ period of the pair line 31 in line symmetry around the central portion 33. The calculation unit 61 connects the first transmission line 11 and the second transmission line 21 before the movement with the first transmission line 11 and the second transmission line 21 after the movement. In this way, the calculation unit 61 determines the shapes of the first transmission line 11 and the second transmission line 21 in an area of ​​½ period of the pair line 31.

[0061] The calculation unit 61 moves the shapes of the first transmission line 11 and the second transmission line 21 in a region corresponding to one half of the period of the pair line 31 in point symmetry around the intersection 32. The calculation unit 61 connects the first transmission line 11 and the second transmission line 21 before the movement with the first transmission line 11 and the second transmission line 21 after the movement. In this way, the calculation unit 61 determines the shapes of the first transmission line 11 and the second transmission line 21 in a region corresponding to one period of the pair line 31.

[0062] The calculation unit 61 repeats the above-described process for the region of ½ period of the pair line 31 m times to determine the shape of the first transmission line 11 and the shape of the second transmission line 21 in the entire pair line 31.

[0063] [Hardware configuration of the calculation device] Next, a description will be given of the hardware configuration of the calculation device 50. Fig. 7 is a block diagram showing an example of the hardware configuration of the calculation device 50. As shown in Fig. 7, the calculation device 50 is configured by a computer, and includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 105, a storage 107, an input device 109, a display device 111, and a manufacturing equipment interface 113.

[0064] The CPU 101 executes a program stored in the ROM 103. The CPU 101 performs arithmetic processing on data loaded into the RAM 105 in accordance with the program, and comprehensively controls each part of the calculation device 50. The CPU is also called a processor.

[0065] The ROM 103 stores programs and the like to be executed by the CPU 101. In this embodiment, the ROM 103 stores at least a program for controlling the operation flow of the calculation device 50, which will be described later. The RAM 105 temporarily holds calculation data when the CPU 101 executes the programs stored in the ROM 103. The ROM 103 and the RAM 105 are also referred to as a non-volatile memory and a volatile memory, respectively.

[0066] The storage 107 stores control parameters necessary for the operation of the calculation device 50, various information necessary for the operation flow of the calculation device 50, etc. The CPU 101 controls reading and writing of data from and to the storage 107 in accordance with a program stored in the ROM 103. The storage 107 is, for example, a hard disk drive (HDD) or a solid state drive (SSD), and the storage 107 may be a combination of an HDD and an SSD. The storage 107 may also be provided outside the calculation device 50 as a database.

[0067] The input device 109 accepts input from a user. The display device 111 displays various input values ​​input to the input device 109 and various calculated values ​​calculated by the calculation device 50.

[0068] The manufacturing device interface 113 is connected to the manufacturing device 120. The CPU 101 transmits and receives data to and from the manufacturing device 120 via the manufacturing device interface 113. The manufacturing device 120 manufactures the substrate 1 based on the information output from the calculation device 50 regarding the shape of the first transmission line 11 and the shape of the second transmission line 21 in the pair line 31.

[0069] [Operation flow of the calculation device] Next, a description will be given of the operation flow of the calculation device 50. Fig. 8 is a diagram showing an example of the operation flow of the calculation device 50. As shown in Fig. 8, the calculation device 50 determines the positions of n calculation targets in the region from the intersection 32 of the paired lines 31 to the center part 33 of the paired lines 31 (step S11).

[0070] The calculation device 50 sets the counter i to the value "1" (step S13). The calculation device 50 determines the cross-sectional shape of the pair line 31 at the i-th calculation target position (step S15).

[0071] Specifically, the calculation device 50 calculates the width of the first transmission line 11 and the width of the second transmission line 21 at the i-th calculation target position. The calculation device 50 determines the cross-sectional shapes of the first transmission line 11 and the second transmission line 21 using the calculated width of the first transmission line 11 and the width of the second transmission line 21 at the i-th calculation target position and the set values ​​of the height of the first transmission line 11 and the set values ​​of the height of the second transmission line 21.

[0072] The calculation device 50 determines whether the cross-sectional shape of the paired lines 31 at the n-th calculation target position has been determined (step S17). If the calculation device 50 determines that the cross-sectional shape of the paired lines 31 at the n-th calculation target position has not been determined, the calculation device 50 adds "1" to the value of the counter i (step S19) and performs the process of step S15.

[0073] When the calculation device 50 determines that the cross-sectional shape of the pair line 31 at the nth calculation target position has been determined, it determines the shape of the pair line 31 in the region from the intersection 32 of the pair line 31 to the central portion 33 of the pair line 31 (step S21).

[0074] Specifically, the calculation device 50 interpolates between the cross-sectional shape at the jth (1≦j≦n−1) calculation target position and the cross-sectional shape at the j+1th calculation target position in each of the first transmission line 11 and the second transmission line 21, thereby connecting the adjacent cross-sectional shapes. In this way, the calculation unit 61 determines the shapes of the first transmission line 11 and the second transmission line 21 in a region of ¼ period of the pair line 31.

[0075] The calculation device 50 determines the overall shape of the paired lines 31 based on the shape of the paired lines 31 in the region from the intersection 32 of the paired lines 31 to the center 33 of the paired lines 31 (step S23).

[0076] Specifically, the calculation device 50 moves the shapes of the first transmission line 11 and the second transmission line 21 in an area of ​​¼ period of the pair line 31 in line symmetry around the central portion 33. The calculation device 50 connects the first transmission line 11 and the second transmission line 21 before the movement with the first transmission line 11 and the second transmission line 21 after the movement, and determines the shapes of the first transmission line 11 and the second transmission line 21 in an area of ​​½ period of the pair line 31.

[0077] The calculation device 50 moves the shapes of the first transmission line 11 and the second transmission line 21 in a region corresponding to one half of the period of the pair line 31 in a point-symmetric manner around the intersection 32. The calculation device 50 connects the first transmission line 11 and the second transmission line 21 before the movement with the first transmission line 11 and the second transmission line 21 after the movement, and determines the shapes of the first transmission line 11 and the second transmission line 21 in a region corresponding to one period of the pair line 31.

[0078] The calculation device 50 repeats the above-described processing relating to the point-symmetric movement m times to determine the shape of the first transmission line 11 and the shape of the second transmission line 21 in the entire pair line 31.

[0079] After determining the overall shape of the pair line 31, the calculation device 50 outputs information about the shape of the first transmission line 11 and the shape of the second transmission line 21 in the pair line 31 to the manufacturing device 120 (step S25), and the process ends.

[0080] [Comparative Example] Next, a comparative example will be described. Fig. 9 is a plan view of a substrate 201 according to the comparative example. The X direction shown in Fig. 9 corresponds to the longitudinal direction of the substrate 201. The Y direction shown in Fig. 9 corresponds to the width direction of the substrate 201 and is perpendicular to the X direction. The Z direction shown in Fig. 9 corresponds to the height direction of the substrate 201 and is perpendicular to the X and Y directions.

[0081] As shown in FIG. 9, the substrate 201 is a two-layer substrate similar to the substrate 1, and includes a dielectric layer 203, a conductor layer 205, and a conductor layer 207.

[0082] Conductor layer 205 is laminated on the first surface (front surface) of dielectric layer 203 and has first transmission line 211 formed in a meandering shape. Conductor layer 207 is laminated on the second surface (back surface) of dielectric layer 203 and has second transmission line 221 formed in a meandering shape.

[0083] In FIG. 9, the second transmission line 221 is arranged on the second surface (back surface) of the dielectric layer 203 and is therefore hidden by the dielectric layer 203, but the second transmission line 221 is shown by a dotted line to clarify the positional relationship between the first transmission line 211 and the second transmission line 221 on the substrate 201.

[0084] In a plan view of the substrate 201, the first transmission line 211 and the second transmission line 221 extend along the X direction while intersecting each other at a constant interval. With this configuration, the first transmission line 211 and the second transmission line 221 form a pair line 231.

[0085] In a plan view of the substrate 201, the pair line 31 has a plurality of crossing portions 232 where the first transmission line 211 and the second transmission line 221 cross each other.

[0086] In the pair line 231, the distance P between adjacent crossing portions 232, 232 has a constant value. The shape of the pair line 231 changes periodically at intervals of a distance 2P.

[0087] In a plan view of the substrate 201, the distance between the first transmission line 211 and the second transmission line 221 in the width direction (Y direction) of the substrate 201 varies along the longitudinal direction (X direction) of the substrate 201. Specifically, the distance between the central portion 211a of the first transmission line 211 and the central portion 221a of the second transmission line 221 in the width direction (Y direction) of the substrate 201 varies along the longitudinal direction (X direction) of the substrate 201.

[0088] The width of the first transmission line 211 is constant along the longitudinal direction (X direction) of the substrate 201. The width of the second transmission line 221 is constant along the longitudinal direction (X direction) of the substrate 201. Therefore, in the pair line 231, the impedance increases as the distance between the central portion 211a of the first transmission line 211 and the central portion 221a of the second transmission line 221 increases. On the other hand, in the pair line 31, the impedance decreases as the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 decreases.

[0089] 10 to 13, the radiation characteristics and transmission characteristics of a parallel line, paired line 231, and paired line 31 will be compared below. Note that a parallel line is a paired line that does not have any crossing portions. In a parallel line, a pair of transmission lines are arranged linearly and parallel to each other.

[0090] In this embodiment, the radiation characteristics and transmission characteristics of the entire lines shown in FIGS. 10 to 13 were calculated using "Microwave Studio" in "CST STUDIO SUITE," which is commercially available electromagnetic field simulation software.

[0091] The various feature quantities set in the simulation for calculating the radiation characteristics and transmission characteristics of the pair line 31 shown in FIGS. 10 to 13 are as follows: In a plan view of the substrate 1, the distance between adjacent intersections 32, 32 (distance P in FIG. 2) is 15 mm. In a plan view of the substrate 1, the maximum and minimum values ​​of the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 are 2 mm and 0 mm, respectively. In a plan view of the substrate 1, the maximum and minimum values ​​of the widths of the first transmission line 11 and the second transmission line 21 are 1.02 mm and 0.129 mm, respectively.

[0092] The various feature quantities set in the simulation for calculating the radiation characteristics and transmission characteristics of the pair line 231 shown in Figures 10 to 13 are as follows. In a plan view of the substrate 201, the value of the distance (distance P in Figure 9) between adjacent intersection portions 232, 232 is 15 mm. In a plan view of the substrate 201, the maximum and minimum values ​​of the distance between the central portion 211a of the first transmission line 211 and the central portion 221a of the second transmission line 221 are 2 mm and 0 mm, respectively. In a plan view of the substrate 201, the width of each of the first transmission line 211 and the second transmission line 221 is 0.55 mm.

[0093] The various feature quantities set in the simulations for calculating the radiation characteristics and transmission characteristics of the parallel lines shown in Figures 10 to 13 are as follows: The distance between the centers of the two lines in a planar view of the board is 0.775 mm The width of each line in a planar view of the board is 0.275 mm

[0094] In a plan view of the substrate 1 and the substrate 201, the pair lines 31 and the pair lines 231 have multiple crossing portions 32 and multiple crossing portions 232, respectively, compared to parallel lines (see FIGS. 2 and 9). Therefore, in each of the pair lines 31 and the pair lines 231, when currents flow in opposite directions through one transmission line and the other transmission line, a magnetic field is generated in a direction perpendicular to the surface of the substrate in the region surrounded by the one transmission line and the other transmission line, which is formed between the adjacent crossing portions. However, in the adjacent regions, the direction of the magnetic field generated in one region is opposite to the direction of the magnetic field generated in the other region, and so these magnetic fields cancel each other out.

[0095] In contrast to this, parallel lines have no intersecting portions and therefore cannot cancel out magnetic fields generated in a direction perpendicular to the surface direction of the substrate.

[0096] 10 is a diagram comparing the radiation characteristics (electric field strength) of a parallel line, pair line 231, and pair line 31. As shown in Fig. 10, the electric field strength radiated to the outside in pair line 31 and pair line 231 is lower than the electric field strength radiated to the outside in a wide frequency range in pair line 31 and pair line 231. Therefore, pair line 31 and pair line 231 can suppress radiation noise generated in the board and improve EMI performance compared to parallel lines.

[0097] 11 is a diagram comparing the radiation characteristics (magnetic field strength) of a parallel line, paired lines 231, and paired lines 31. As shown in Fig. 11, the magnetic field strength radiated to the outside in paired lines 31 and 231 is lower than the magnetic field strength radiated to the outside in a wide frequency range. Therefore, paired lines 31 and 231 can suppress radiation noise generated on the board and improve EMI performance compared to parallel lines.

[0098] Compared to the pair line 231, the pair line 31 and the parallel line have smaller changes in the positional relationship between one transmission line and the other transmission line along the extension direction of the pair of transmission lines. Therefore, there are almost no points in the pair line 31 and the parallel line where the impedance is not matched. In contrast, the pair line 231 has larger changes in the positional relationship between one transmission line and the other transmission line along the extension direction of the pair of transmission lines. Therefore, there are many points in the pair line 231 where the impedance is not matched.

[0099] 12 is a diagram comparing the transmission characteristics (pass characteristics) of a parallel line, paired lines 231, and paired lines 31. As shown in FIG. 12, the pass characteristics of paired lines 31 and parallel lines are higher than the pass characteristics of paired lines 231 over a wide frequency range. Therefore, paired lines 31 and parallel lines can avoid a decrease in communication performance compared to paired lines 231.

[0100] 13 is a diagram comparing the transmission characteristics (impedance change) of the parallel line, the pair line 231, and the pair line 31. Note that the impedance was calculated using TDR (Time Domain Reflectometry), where a step pulse signal was input to each of the parallel line, the pair line 231, and the pair line 31, and the reflected wave was received to calculate the impedance of each line. In this embodiment, a step pulse with a rise time of 58 ps was input to each of the parallel line, the pair line 231, and the pair line 31.

[0101] 13, the impedance change in the pair line 31 and the parallel line is smaller than the impedance change in the pair line 231. Therefore, the pair line 31 and the parallel line can suppress the impedance change compared to the pair line 231, and can avoid a decrease in communication performance.

[0102] [Actions and Effects] According to this embodiment, a pair of transmission lines is formed on the substrate 1. The substrate 1 includes a dielectric layer 3, a conductor layer 5, and a conductor layer 7. The dielectric layer 3 has a first surface 3a and a second surface 3b. The conductor layer 5 is laminated on the first surface 3a of the dielectric layer 3 and has a first transmission line 11 formed in a meandering shape. The conductor layer 7 is laminated on the second surface 3b of the dielectric layer 3 and has a second transmission line 21 formed in a meandering shape.

[0103] In a plan view of the substrate 1, the first transmission line 11 and the second transmission line 21 extend along the longitudinal direction (X direction) of the substrate 1 while intersecting each other. In a plan view of the substrate 1, as the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 in the width direction (Y direction) of the substrate 1 that is perpendicular to the longitudinal direction (X direction) of the substrate 1 increases, the widths of the first transmission line 11 and the second transmission line 21 increase.

[0104] As described above, when a pair of transmission lines has multiple crossing points in a plan view of the substrate, if currents flow in opposite directions through one transmission line and the other transmission line, a magnetic field is generated in a direction perpendicular to the surface of the substrate in the region surrounded by the one transmission line and the other transmission line, which is formed between the adjacent crossing points. However, in the adjacent regions, the direction of the magnetic field generated in one region is opposite to the direction of the magnetic field generated in the other region, and so these magnetic fields cancel each other out.

[0105] Therefore, with the above-described configuration, in a plan view of the substrate 1, the first transmission line 11 and the second transmission line 21 extend along the longitudinal direction of the substrate 1 while intersecting each other, thereby suppressing radiation noise generated in the substrate 1 and improving EMI performance.

[0106] Furthermore, as described above, in a pair of transmission lines, as the distance between the transmission lines increases, the impedance of the pair of transmission lines increases, and as the width of the transmission lines increases, the impedance of the pair of transmission lines decreases.

[0107] Therefore, with the above-described configuration, when the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 is large, the width of the first transmission line 11 and the width of the second transmission line 21 are increased, thereby making it possible to prevent the impedance from increasing below the set value. Furthermore, with the above-described configuration, when the distance between the central portion 11a of the first transmission line 11 and the central portion 21a of the second transmission line 21 is small, the width of the first transmission line 11 and the width of the second transmission line 21 are decreased, thereby making it possible to prevent the impedance from decreasing below the set value.

[0108] Therefore, in the substrate 1, it is possible to improve EMI performance while avoiding a decrease in communication performance.

[0109] According to this embodiment, the cross-sectional shapes of the first transmission line 11 and the second transmission line 21, cut along a plane parallel to the stacking direction of the substrate 1, are set so that the impedance between the first transmission line 11 and the second transmission line 21 is a constant value.

[0110] The above-described configuration makes it possible to match impedances within the first transmission line 11 and the second transmission line 21. This makes it possible to effectively avoid a decrease in communication performance.

[0111] According to this embodiment, no ground layer is disposed outside the conductor layers 5 and 7.

[0112] With the above-described configuration, there is no need to arrange a ground layer on the substrate 1, and therefore, with a simple configuration, it is possible to improve EMI performance while avoiding a decrease in communication performance.

[0113] According to this embodiment, in a plan view of the substrate 1, between adjacent intersections 32, 32 where the first transmission line 11 and the second transmission line 21 intersect with each other, the first transmission line 11 is formed line-symmetrically with respect to the central portion 33 between the intersections 32, 32, and the second transmission line 21 is formed line-symmetrically with respect to the central portion 33 between the intersections 32, 32.

[0114] With the above-described configuration, it is possible to easily manufacture the substrate 1 that can improve EMI performance while avoiding degradation of communication performance.

[0115] [Variations] In the above-described embodiment, only pair lines 31 are provided on the substrate 1, but this is not limiting and multiple pair lines may be provided. Fig. 14 is a plan view of a substrate 1A according to this modification. As shown in Fig. 14, in this modification, two pair lines 31A and 31B are provided on the substrate 1A.

[0116] The X direction shown in Fig. 14 corresponds to the longitudinal direction of the substrate 1A. The Y direction shown in Fig. 14 corresponds to the width direction of the substrate 1A and is perpendicular to the X direction. The Z direction shown in Fig. 14 corresponds to the height direction of the substrate 1A and is perpendicular to the X and Y directions.

[0117] The substrate 1A includes a dielectric layer 3, a conductor layer 5A, and a conductor layer 7A. The conductor layer 5A is laminated on a first surface 3a of the dielectric layer 3, and has a first transmission line 11A and a third transmission line 11B formed in a meandering shape. The third transmission line 11B is disposed alongside the first transmission line 11A.

[0118] The conductor layer 7A is laminated on the second surface 3b of the dielectric layer 3, and has a second transmission line 21A and a fourth transmission line 21B formed in a meandering shape. The fourth transmission line 21B is disposed alongside the second transmission line 21A.

[0119] In FIG. 14, the second transmission line 21A and the fourth transmission line 21B are arranged on the second surface 3b (rear surface) of the dielectric layer 3 and are therefore hidden by the dielectric layer 3. However, to clarify the positional relationship between the first transmission line 11A, the second transmission line 21A, the third transmission line 11B, and the fourth transmission line 21B on the substrate 1, the second transmission line 21A and the fourth transmission line 21B are shown by dotted lines.

[0120] In a plan view of the substrate 1A, the first transmission line 11A and the second transmission line 21A extend along the longitudinal direction (X direction) of the substrate 1A while intersecting each other. The first transmission line 11A and the second transmission line 21A form a pair line 31A. In a plan view of the substrate 1A, the third transmission line 11B and the fourth transmission line 21B extend along the longitudinal direction (X direction) of the substrate 1A while intersecting each other. The third transmission line 11B and the fourth transmission line 21B form a pair line 31B.

[0121] In a plan view of the substrate 1A, as the distance between the central portion 11Aa of the first transmission line 11A and the central portion 21Aa of the second transmission line 21A in the width direction (Y direction) of the substrate 1A, which is perpendicular to the longitudinal direction (X direction) of the substrate 1A, increases, the width of the first transmission line 11A and the width of the second transmission line 21A increase.

[0122] In a plan view of the substrate 1A, as the distance between the central portion 11Ba of the third transmission line 11B and the central portion 21Ba of the fourth transmission line 21B increases in the width direction (Y direction) of the substrate 1A, which is perpendicular to the longitudinal direction (X direction) of the substrate 1A, the width of the third transmission line 11B and the width of the fourth transmission line 21B increase.

[0123] In a plan view of the substrate 1A, the first transmission line 11A and the second transmission line 21A have a first section and a second section. The first section has a plurality of intersections 34 where the first transmission line 11A and the second transmission line 21A intersect with each other, and the distance between adjacent intersections 34, 34 has a value of distance P. The second section has a plurality of intersections 35 where the first transmission line 11A and the second transmission line 21A intersect with each other, and the distance between adjacent intersections 35, 35 has a value of distance P / 2. The values ​​of distance P and distance P / 2 are also referred to as a first value and a second value, respectively.

[0124] In a plan view of the substrate 1A, the third transmission line 11B and the fourth transmission line 21B have a third section and a fourth section. The third section has a plurality of intersections 34 where the third transmission line 11B and the fourth transmission line 21B intersect with each other, and the distance between adjacent intersections 34, 34 has a value of distance P. The fourth section has a plurality of intersections 35 where the third transmission line 11B and the fourth transmission line 21B intersect with each other, and the distance between adjacent intersections 35, 35 has a value of distance P / 2.

[0125] In the width direction (Y direction) of the substrate 1A, the first section of the first transmission line 11A and the second transmission line 21A is adjacent to the fourth section of the third transmission line 11B and the fourth transmission line 21B, and the second section of the first transmission line 11A and the second transmission line 21A is adjacent to the third section of the third transmission line 11B and the fourth transmission line 21B. In this way, the pair lines 31A and 31B are arranged side by side with a pitch shift. The line length of the pair line 31A and the line length of the pair line 31B are the same.

[0126] With the above-described configuration, the pair lines 31A and 31B are provided on the board 1A, thereby improving the data transfer speed. The pair lines 31A and 31B are arranged side by side with a shifted pitch, thereby preventing crosstalk from occurring on the board 1A. The line lengths of the pair lines 31A and 31B are the same, preventing inter-pair skew from occurring on the board 1A.

[0127] [Other variations] In the above-described embodiments, the substrate 1 may be a printed circuit board (PCB) or a flexible printed circuit board (FPC).

[0128] In the above-described embodiment, the first transmission line 11 and the second transmission line 21 are formed on the conductor layers 5 and 7, respectively, which are arranged parallel to each other with the dielectric layer 3 interposed therebetween in the substrate 1, but this is not limiting. The first transmission line 11 and the second transmission line 21 only need to be formed on layers which are arranged parallel to each other, and are not limited to the configuration of the substrate 1.

[0129] In the above-described embodiment, the first transmission line 11 and the second transmission line 21 on the substrate 1 meander within the surface direction (XY plane) of the substrate 1, but this is not limiting. The first transmission line 11 and the second transmission line 21 may meander up and down along the stacking direction (Z direction) of the substrate 1 via contact holes formed in the dielectric layer 3 while meandering within the surface direction (XY plane) of the substrate 1.

[0130] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0131] 1 board 3 Dielectric Layer 3a 1st page 3b 2nd side 5 Conductor layer 7 Conductor Layer 11 First transmission line 11a Central part 21 Second transmission line 21a Central part 32 Intersection

Claims

1. A substrate on which a pair of transmission lines is formed, a dielectric layer having a first surface and a second surface; a first conductor layer laminated on the first surface of the dielectric layer and having a first transmission line formed in a meandering shape; a second conductor layer laminated on the second surface of the dielectric layer and having a second transmission line formed in a meandering shape; Equipped with In a plan view of the substrate, the first transmission line and the second transmission line extend along a first direction while intersecting each other, a substrate, wherein, in a plan view of the substrate, as a distance between a central portion of the first transmission line and a central portion of the second transmission line increases in a second direction perpendicular to the first direction, a width of the first transmission line and a width of the second transmission line increase.

2. 2. The substrate according to claim 1, wherein a cross-sectional shape of the first transmission line and a cross-sectional shape of the second transmission line taken along a plane parallel to a stacking direction of the substrate are set so that impedance between the first transmission line and the second transmission line is a constant value.

3. The substrate according to claim 1 , wherein no ground layer is disposed outside the first conductor layer and the second conductor layer.

4. 2. The substrate according to claim 1, wherein, in a plan view of the substrate, between two adjacent points where the first transmission line and the second transmission line intersect with each other, the first transmission line is formed in line symmetry with respect to a center between the two points, and the second transmission line is formed in line symmetry with respect to the center between the two points.

5. the first conductor layer has a third transmission line arranged alongside the first transmission line and formed in a meandering shape; the second conductor layer has a fourth transmission line arranged alongside the second transmission line and formed in a meandering shape, In a plan view of the substrate, the third transmission line and the fourth transmission line extend along the first direction while intersecting each other, a width of the third transmission line and a width of the fourth transmission line increase as a distance between a center portion of the third transmission line and a center portion of the fourth transmission line increases in the second direction in a plan view of the substrate, In a plan view of the substrate, the first transmission line and the second transmission line are formed with a first section in which a distance between two adjacent points where the first transmission line and the second transmission line intersect with each other has a first value, and a second section in which a distance between two adjacent points where the first transmission line and the second transmission line intersect with each other has a second value smaller than the first value, In a plan view of the substrate, the third transmission line and the fourth transmission line are formed with a third section in which a distance between two points where the third transmission line and the fourth transmission line intersect with each other has the first value, and a fourth section in which a distance between two points where the third transmission line and the fourth transmission line intersect with each other has the second value, In the second direction, the first section is adjacent to the fourth section, The substrate of claim 1 , wherein the second section is adjacent to the third section in the second direction.

Images