Wiring Board

Abstract

A wiring board (10) according to the present invention comprises: a dielectric substrate (11); a ground layer (14) that is located on one surface of the dielectric substrate (11); a first conductor line (12_1) and a first ground plane (13_1) that are located separately on the other surface of the dielectric substrate (11) opposed to the one surface thereof; and a second conductor line (12_2) that is located directly below the first ground plane in the dielectric substrate (11).　In this way, the present invention can provide a wiring board that can suppress crosstalk and that can be applied to various transmission systems.

Description

[Technical field]

[0001] The present invention relates to a wiring board having a high-frequency transmission line. [Background technology]

[0002] For wiring boards equipped with high-frequency transmission lines (high-frequency transmission line boards), electrical design such as characteristic impedance is important. For example, in high-frequency transmission line boards, electromagnetic and electromagnetic wave behavior such as reflection and crosstalk propagating through signal lines becomes prominent, so matching and measures against reflected noise are necessary. In particular, parallel wiring within a module is composed of many closely spaced wiring, and problems of wiring delay and crosstalk noise become apparent.

[0003] In high-frequency transmission line substrates, microstrip lines, coplanar lines, grounded coplanar lines, etc. are used as wiring structures (transmission line structures) for propagating high-speed high-frequency signals. For example, a microstrip line is configured by forming a flat conductive ground layer on one side of a dielectric substrate and a strip-shaped line on the other side to form a transmission line. The characteristic impedance of these lines is determined by the width and thickness of the signal line, the dielectric constant and thickness of the dielectric substrate, and the geometric dimensions of the gap between the signal line and the ground pattern.

[0004] In addition, in order to reduce the cost of high-frequency transmission line substrates, it is necessary to integrate parallel wiring at a high density. However, when the parallel wiring is integrated at a high density, the distance between the lines becomes short, and problems such as crosstalk between the transmission lines become prominent.

[0005] Therefore, in wiring boards connected to semiconductor high-frequency modules, a parallel wiring structure that maintains high-frequency characteristics and enables high-density signal transmission is required. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-101587 A Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, in order to transmit signals at high density, it is necessary to arrange the signal lines at high density. However, when the distance between the signal lines is reduced, crosstalk noise between the lines increases, making it difficult to transmit signals while maintaining high frequency characteristics.

[0008] In detail, crosstalk noise between wirings occurs when a signal pulse is transmitted through one signal line, displacing electrons in the other signal line. If the distance between the signal lines is reduced, the amount of displacement of electrons in the other signal line increases, and the crosstalk noise increases.

[0009] Therefore, it has been difficult to realize a parallel wiring structure that maintains high frequency characteristics and enables high density signal transmission.

[0010] Furthermore, when the distance between signal lines is reduced, the distance between the signal lines and the ground layer or ground plane is also reduced, making it difficult to set the desired characteristic impedance, particularly when the signal line width is fixed.

[0011] For example, a high-density mounting technology for suppressing crosstalk is disclosed in Patent Document 1. However, since the signals that can be transmitted with this technology are limited to differential signals, there is a problem that it cannot be applied to various transmission methods. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, a wiring board according to the present invention includes a dielectric substrate, a ground layer disposed on one surface of the dielectric substrate, a first conductor line and a first ground plane disposed at a distance from each other on the other surface of the dielectric substrate opposite to the one surface, and a wiring layer disposed within the dielectric substrate. In a plane parallel to the one surface ofa second conductor line disposed directly below the first ground plane; only It is equipped with. Effect of the Invention

[0013] According to the present invention, it is possible to provide a wiring board which suppresses crosstalk and is applicable to a variety of transmission methods. [Brief description of the drawings]

[0014] [Figure 1A] FIG. 1A is a schematic top view of a wiring board according to a first embodiment of the present invention. [Figure 1B] FIG. 1B is a schematic cross-sectional view of the wiring board taken along line IB-IB' according to the first embodiment of the present invention. [Figure 1C] FIG. 1C is a schematic cross-sectional view of the wiring board taken along line IC-IC' according to the first embodiment of the present invention. [Figure 2A] FIG. 2A is a schematic diagram of a model used for calculating the characteristics of the wiring board according to the first embodiment of the present invention. [Figure 2B] FIG. 2B is a schematic diagram of a model used for calculating the characteristics of the wiring board according to the first embodiment of the present invention. [Figure 3A] FIG. 3A is a schematic diagram of a model used to calculate the characteristics of a conventional wiring board. [Figure 3B] FIG. 3B is a schematic diagram of a model used to calculate the characteristics of a conventional wiring board. [Figure 4A] FIG. 4A is a diagram showing an effect of the wiring board according to the first embodiment of the present invention. [Figure 4B] FIG. 4B is a diagram showing an effect of the wiring board according to the first embodiment of the present invention. [Figure 5A] FIG. 5A is a schematic top view of a wiring board according to a second embodiment of the present invention. [Figure 5B] FIG. 5B is a schematic cross-sectional view of the wiring board according to the second embodiment of the present invention taken along line VB-VB'. [Figure 5C]FIG. 5C is a schematic cross-sectional view of the wiring board taken along line VC-VC' according to the second embodiment of the present invention. [Figure 6A] FIG. 6A is a schematic diagram of a model used for calculating the characteristics of a wiring board according to the second embodiment of the present invention. [Figure 6B] FIG. 6B is a schematic diagram of a model used for calculating the characteristics of the wiring board according to the second embodiment of the present invention. [Figure 7A] FIG. 7A is a schematic diagram of a model used to calculate the characteristics of a conventional wiring board. [Figure 7B] FIG. 7B is a schematic diagram of a model used to calculate the characteristics of a conventional wiring board. [Figure 8A] FIG. 8A is a diagram showing an effect of the wiring board according to the second embodiment of the present invention. [Figure 8B] FIG. 8B is a diagram showing an effect of the wiring board according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <First embodiment> A wiring board according to a first embodiment of the present invention will be described with reference to FIGS. 1A to 4B.

[0016] <Wiring board configuration> Fig. 1A shows a schematic top view of wiring board 10 according to the present embodiment. Fig. 1B and Fig. 1C show schematic cross-sectional views taken along lines IB-IB' and IC-IC' in Fig. 1A, respectively. Hereinafter, the XY plane in Fig. 1A to C is defined as the horizontal plane, the Z direction as the vertical direction, the Z(+) direction as the upward direction, and the opposite direction as the downward direction.

[0017] As shown in Figures 1A and 1B, the wiring board 10 comprises a dielectric substrate 11, a ground layer 14 on the lower surface (one surface) of the dielectric substrate 11, and a first conductor line (signal line) 12_1 made of a strip-shaped conductor on an upper surface (the other surface) opposite the lower surface of the dielectric substrate 11, a first ground plane 13_1, a first electrode 15_1, and a second electrode 15_2.

[0018] Also, on the same horizontal plane within the dielectric substrate 11, there is provided a second conductor line (signal line) 12_2 arranged directly below the first ground plane 13_1, and a second ground plane 13_2 arranged directly below the first conductor line 12_1.

[0019] Here, benzocyclobutene (BCB) or the like is used for the dielectric substrate 11. Also, the first conductor line 12_1, the second conductor line 12_2, the first ground plane 13_1, the second ground plane 13_2, the first electrode 15_1, and the second electrode 15_2 are made of conductive materials such as Au.

[0020] The first electrode 15_1 is connected to the first conductor line 12_1, and the second electrode 15_2 is connected to the second conductor line 12_2. Here, as shown in Fig. 1C, in order to make the electrode capacitance of the first conductor line 12_1 and the electrode capacitance of the second conductor line 12_2 the same and suppress the influence of the electrode capacitance in the measurement (described later), the first electrode 15_1 and the second electrode 15_2 are formed inside the dielectric substrate 11, but the first electrode 15_1 may be formed only on the surface and connected to the first conductor line 12_1.

[0021] In this manner, in wiring board 10, first conductor line 12_1, which is a strip-shaped conductor disposed on the other surface (upper surface), and first ground plane 13_1 form a coplanar line.

[0022] Furthermore, within the same plane parallel to the upper surface of the dielectric substrate 11, a strip-shaped second conductor line 12_2 arranged directly below the first ground plane 13_1 and a second ground plane 13_2 arranged directly below the first conductor line 12_1 form a coplanar line.

[0023] In this configuration, a grounded coplanar line is formed by the coplanar line on the other surface (upper surface) and the second ground plane 13_2 in the dielectric substrate 11. Similarly, a grounded coplanar line is formed by the coplanar line in the dielectric substrate 11 and the twelfth ground plane on the other surface (upper surface).

[0024] In this way, the grounded coplanar lines with the second ground plane 13_2 as the ground layer 14 and the grounded coplanar lines with the first ground plane 13_1 as the ground layer 14 are alternately arranged.

[0025] In the wiring substrate 10, by making the distance (hereinafter referred to as "line distance") h3 between the first conductor line 12_1 and the second conductor line 12_2 larger than the substantial line distance (hereinafter referred to as "substantial line distance") g2 in the (horizontal direction) as viewed from the upper surface (g2 < h3), crosstalk noise can be reduced.

[0026] Furthermore, by making the distance between the first conductor line 12_1 and the first ground plane 13_1 and the distance g1 between the second conductor line 12_2 and the second ground plane 13_2 smaller than the line distance h3 (g1 < h3), the electric fields generated between the first conductor line 12_1 and the first ground plane 13_1 and between the second conductor line 12_2 and the second ground plane 13_2 become larger.

[0027] Also, by making the distance between the first conductor line 12_1 and the second ground plane 13_2 and the distance h1 between the second conductor line 12_2 and the first ground plane 13_1 smaller than the line distance h3 (h1 < h3), the electric fields generated between the first conductor line 12_1 and the second ground plane 13_2 and between the second conductor line 12_2 and the first ground plane 13_1 become larger.

[0028] As a result, the electric field generated from one conductor line is deflected in the direction of the ground plane by the ground plane located closest to the conductor line and the ground plane located directly below or above the conductor line, so that the electric field propagating from one conductor line to the other conductor line is suppressed, thereby reducing crosstalk noise.

[0029] This makes it possible to realize a wiring board 10 having parallel wiring that can reduce the wiring area and reduce crosstalk noise between wirings.

[0030] In addition, by adjusting the distance between the conductor line and the ground plane, which is located closest to the conductor line and in the ground plane located directly below or above the conductor line, the degree of freedom in setting the characteristic impedance of the line can be increased compared to conventional coplanar lines or microstrip lines.

[0031] In addition, it can be applied to a variety of transmission methods, making it possible to put it into practical use and reduce costs.

[0032] <Effects of wiring board> The effects of wiring board 10 according to the present embodiment will be described below with reference to FIGS. 2A to 4B.

[0033] The amount of crosstalk in wiring board 10 according to the present embodiment is simulated and compared with that in a conventional wiring board 10'.

[0034] 2A and 2B show a schematic diagram of wiring board 10 according to the present embodiment used in the simulation, and a schematic cross-sectional view of the wiring structure, respectively. Also, 3A and 3B show a schematic diagram of a conventional wiring board 10′ used in the simulation, and a schematic cross-sectional view of the wiring structure, respectively.

[0035] For the simulation, the electromagnetic field simulator "Sonnet-EM" (manufactured by Sonnet Giken) is used.

[0036] In the wiring board 10 used in the simulation, Au metal is used for the strip-shaped first conductor line 12_1, the strip-shaped second conductor line 12_2, the first ground plane 13_1, the second ground plane 13_2, and the ground layer 14. A benzocyclobutene (BCB) substrate (εr=2.7) is used for the dielectric substrate 11. Parallel wiring of microstrip lines with a line length of 300 μm is used.

[0037] In order to simplify the calculation by making the characteristic impedances equal, a BCB layer is formed on the first conductor line 12_1 and the first ground plane 13_1, and the periphery is covered with BCB in the same manner as the second conductor line 12_2. The number of conductor lines and ground planes is five each.

[0038] Also, the substantial inter-line distance g2 is 12 μm, the thickness of the first conductor line 12_1 and the second conductor line 12_2 is 2 μm, the thickness of the first ground plane 13_1 and the second ground plane 13_2 is 2 μm, and the characteristic impedance is 50Ω.

[0039] As shown in Figures 2A and 2B, the configuration of wiring board 10 in this embodiment is as follows: first conductor line 12_1 has a width W1 = 6 μm, second conductor line 12_2 has a width W2 = 6 μm, distance g1 between first conductor line 12_1 and first ground plane 13_1 = 3 μm, and distance h1 between second conductor line 12_2 and first ground plane 13_1 = 8 μm.

[0040] As shown in FIGS. 3A and 3B, conventional wiring board 10' has a width W of lines 12' of 6 μm, distance G between lines of 6 μm, and distance h between lines 12' and ground layer 14' of 4 μm.

[0041] The amount of crosstalk can be directly evaluated by calculating the S-parameter results between each port shown in Figures 2B and 3B. For example, S31 is the ratio of the voltage of the signal supplied to the first port to the voltage output to the third port, and is called the backward (near-end) crosstalk. S41 is the ratio of the voltage of the signal supplied to the first port to the voltage output to the fourth port, and is called the forward (far-end) crosstalk.

[0042] 4A and B show the simulation results for S31 (backward crosstalk) and S41 (forward crosstalk), respectively, where decibels are used for easy comparison.

[0043] In S31 (backward crosstalk), the crosstalk of wiring board 10 is reduced by more than 0 dB and less than 20 dB in a wide range from more than 0 GHz to less than 100 GHz, as compared to conventional wiring board 10'.

[0044] Furthermore, in terms of S41 (forward crosstalk), the crosstalk of wiring board 10 is reduced by 25 dB to 60 dB in a wide range from higher than 0 GHz to lower than 100 GHz, compared to conventional wiring board 10'.

[0045] According to the wiring board of the present embodiment, the distance between the lines is made larger than the effective distance between the lines when viewed from above (horizontally), thereby reducing crosstalk noise. Also, the distance between the lines and the ground plane is made smaller than the distance between the lines, thereby enabling further reduction in crosstalk noise.

[0046] As described above, according to the wiring board of the present embodiment, it is possible to improve the wiring density, reduce crosstalk noise between wiring lines, and realize a wiring board having parallel wiring lines applicable to high-density mounting.

[0047] <Second embodiment> A wiring board according to a second embodiment of the present invention will be described with reference to FIGS. 5A to 5C.

[0048] <Wiring board configuration> Fig. 5A shows a schematic top view of wiring board 20 according to this embodiment. Figs. 5B and 5C show schematic cross-sectional views taken along lines VB-VB' and VC-VC' in Fig. 5A, respectively.

[0049] As shown in Figures 5A and 5B, the wiring board 20 comprises a dielectric substrate 21, a first conductor line 22_1 made of a strip-shaped conductor on the upper surface of the dielectric substrate 21, a first ground plane 23_1, a first electrode 25_1, and a second electrode 25_2, and a ground layer 24 on the lower surface (bottom surface) of the dielectric substrate 21.

[0050] Also, a second conductor line 22_2 is provided, which is disposed on the same horizontal plane within the dielectric substrate 21 and directly below the first ground plane 23_1.

[0051] Here, benzocyclobutene (BCB) or the like is used for the dielectric substrate 21. Also, the first conductor line 22_1, the second conductor line 22_2, the first ground plane 23_1, the second ground plane 23_2, the first electrode 25_1, and the second electrode 25_2 are made of conductive materials such as Au.

[0052] The first electrode 25_1 is connected to the first conductor line 22_1, and the second electrode 25_2 is connected to the second conductor line 22_2. Here, as shown in Fig. 5C, in order to make the electrode capacitance of the first conductor line 22_1 and the electrode capacitance of the second conductor line 22_2 equal to each other and suppress the influence of the electrode capacitance in the measurement (described later), the example in which the first electrode 25_1 and the second electrode 25_2 are formed to the inside of the dielectric substrate 21 has been shown, but the first electrode 25_1 may be formed only on the surface and connected to the first conductor line 22_1.

[0053] Thus, the wiring board 20 comprises a dielectric substrate 21 (dielectric constant ε1), a ground layer 14 provided on one surface (bottom surface) of the dielectric substrate 21, and a coplanar line on the other surface (top surface) consisting of a first conductor line 22_1 of a strip-shaped conductor and a first ground plane 23_1.

[0054] Furthermore, a strip-shaped second conductor line 22_2 disposed directly below the first ground plane 23_1 is provided in the same plane parallel to the upper surface in the dielectric substrate 21.

[0055] Thus, in the wiring board 20, coplanar lines and strip-shaped conductor lines (microstrip lines) are alternately arranged.

[0056] In the wiring board 20, by making the line-to-line distance h3 larger than the substantial line-to-line distance g2 (g2 < h3), crosstalk noise can be reduced.

[0057] Furthermore, by making the distance g1 between the first conductor line 22_1 and the first ground plane 23_1 smaller than the line-to-line distance h3 (g1 < h3), the electric field generated between the first conductor line 22_1 and the first ground plane 23_1 becomes larger.

[0058] Also, by making the distance h1 between the second conductor line 22_2 and the first ground plane 23_1 smaller than the line-to-line distance h3 (h1 < h3), the electric field generated between the second conductor line 22_2 and the first ground plane 23_1 becomes larger.

[0059] As a result, the electric field generated from one conductor line is deflected in the direction in which the ground plane is disposed by the ground plane disposed closest in the same plane as the conductor line and the ground plane disposed directly above the conductor line, so that the electric field transmitted from one conductor line to the other conductor line is suppressed. Therefore, crosstalk noise can be reduced.

[0060] Thereby, a wiring board 10 having a parallel wiring capable of reducing the wiring area and reducing crosstalk noise between wirings can be realized.

[0061] In addition, by adjusting the distance between the conductor line and the ground plane, which is located closest to the conductor line and in the ground plane located directly above the conductor line, the degree of freedom in setting the characteristic impedance of the line can be increased compared to conventional coplanar lines or microstrip lines.

[0062] In addition, it can be applied to a variety of transmission methods, making it possible to put it into practical use and reduce costs.

[0063] <Effects of wiring board> The effects of wiring board 20 according to the present embodiment will be described below with reference to FIGS. 6A to 8B.

[0064] As in the first embodiment, the amount of crosstalk of wiring board 20 according to this embodiment is simulated and compared with that of conventional wiring board 20'.

[0065] 6A and 6B show a schematic diagram of wiring board 20 according to the present embodiment used in the simulation, and a schematic cross-sectional view of the wiring structure, respectively. Also, 7A and 7B show a schematic diagram of a conventional wiring board 20′ used in the simulation, and a schematic cross-sectional view of the wiring structure, respectively.

[0066] As shown in Figures 6A and 6B, the configuration of wiring board 20 in this embodiment is as follows: width W1 of first conductor line 22_1 = 6 μm, width W2 of second conductor line 22_2 = 6 μm, distance g1 between first conductor line 22_1 and first ground plane 23_1 = 2.5 μm, and distance h1 between second conductor line 22_2 and first ground plane 23_1 = 3 μm.

[0067] As shown in Figures 7A and 7B, the configuration of conventional wiring board 20' is the same as that of the first embodiment, with width W of line 22' = 6 μm, distance G between lines = 6 μm, and distance h between line 22' and ground layer 24' = 4 μm.

[0068] The configuration other than that described above is the same as that of the first embodiment, and the characteristic impedance is 50Ω.

[0069] 8A and B show the simulation results for S31 (backward crosstalk) and S41 (forward crosstalk), respectively, where decibels are used for easy comparison.

[0070] In S31 (backward crosstalk), the crosstalk of wiring board 20 is reduced by more than 0 dB and not more than 8 dB in a wide range from higher than 0 GHz to not more than 100 GHz, as compared to conventional wiring board 20'.

[0071] Furthermore, in terms of S41 (forward crosstalk), the crosstalk of wiring board 20 is reduced by more than 0 dB and not more than 15 dB in a wide range from more than 0 GHz to not more than 100 GHz, as compared to conventional wiring board 20'.

[0072] According to the wiring board of the present embodiment, the distance between the lines is made larger than the effective distance between the lines when viewed from above (horizontally), thereby reducing crosstalk noise. Also, the distance between the lines and the ground plane is made smaller than the distance between the lines, thereby enabling further reduction in crosstalk noise.

[0073] In this way, according to the wiring board of this embodiment, even if the dielectric substrate does not have a ground plane and does not have a grounded coplanar line, crosstalk noise can be reduced by arranging the microstrip lines and the coplanar lines alternately.

[0074] As described above, according to the wiring board of this embodiment, it is possible to improve the wiring density by arranging microstrip lines and coplanar lines alternately at a high density, and it is possible to realize a wiring board having parallel wiring that can reduce crosstalk noise between wiring and is applicable to high-density mounting.

[0075] In the embodiment of the present invention, an example in which the number of signal lines (parallel lines) and ground planes is five has been shown, but the present invention is not limited to this, and any number of signal lines (parallel lines) and ground planes may be used.

[0076] In the embodiment of the present invention, an example has been shown in which the characteristic impedances of the first conductor line and the second conductor line are equivalent, but different characteristic impedances may be set for the first conductor line and the second conductor line.

[0077] The same effects can be obtained in the first embodiment, the embodiment and the second embodiment, and any combination of the embodiments.

[0078] In the embodiment of the present invention, the structure, dimensions, materials, etc. of each component of the wiring board are shown as examples, but the present invention is not limited to these. Anything that can exert the function and effect of the wiring board may be used. [Industrial Applicability]

[0079] The present invention can be applied to semiconductor high-frequency modules and high-frequency transmission line substrates. [Explanation of symbols]

[0080] 10 Wiring board 11 Dielectric substrate 12_1, 12_2 Conductor line 13_1, 13_2 Ground plane 14 Ground Layer

Claims

1. A dielectric substrate; a ground layer disposed on one surface of the dielectric substrate; a first conductor line and a first ground plane arranged apart from each other on the other surface of the dielectric substrate opposite to the one surface; a second conductor line disposed directly below the first ground plane in a plane parallel to the one surface of the dielectric substrate; A wiring board comprising:

2. A distance between the first conductor line and the second conductor line is greater than a substantial distance between the first conductor line and the second conductor line as viewed from above.

2. The wiring board according to claim 1.

3. A distance between the first conductor line and the first ground plane is smaller than a distance between the first conductor line and the second conductor line.

3. The wiring board according to claim 1 or 2.

4. A distance between the second conductor line and the first ground plane is smaller than a distance between the first conductor line and the second conductor line.

4. The wiring board according to claim 1, wherein the wiring board is a semiconductor device.

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