Multilayer wiring board and electronic device having the same

Abstract

To effectively suppress crosstalk in a multilayer interconnection board provided in an electronic apparatus applicable to a AI learning device or an electronic device used for an electronic apparatus capable of high-speed operation.SOLUTION: The multilayer wiring board includes a first differential line provided in a first signal layer and including a first line and a second line, and a second differential line provided in the first signal layer and including a third line and a fourth line. The multilayer wiring board includes a first signal via electrically connected to the third wiring and a second signal via electrically connected to the fourth wiring. The first differential line includes a first portion, a second portion continuous with the first portion, and a third portion continuous with the second portion, in which the first line is disposed between the ground via and the first signal via or the second signal via adjacent to the ground via, the second line is disposed on a side opposite to the first line across the ground via, and the ground via is interposed between the first line and the second line.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a multilayer wiring board and an electronic device including the same. [Background technology]

[0002] Conventionally, a substrate has been known in which a pair of differential wirings, each consisting of two wires, and a differential signal via pair to which the differential wirings are electrically connected are formed (see, for example, Patent Document 1). Such a substrate is a multilayer wiring substrate having multiple signal layers, and may have multiple differential wirings formed thereon. As the number of differential wirings increases, the number of differential signal via pairs also increases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-212411 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, AI (Artificial Intelligence) technology has made remarkable progress, and electronic devices applicable to AI learning devices have been actively developed. Electronic devices capable of high-speed calculations are also being developed. These electronic devices incorporate electronic devices in which electronic components are mounted on a multilayer wiring board. As the development of these electronic devices progresses, demand for higher-density wiring in multilayer wiring boards is also increasing. A multilayer wiring board includes multiple components. The multiple components include multiple differential wirings and multiple differential signal via pairs. As the wiring density in a multilayer wiring board increases, it is expected that electromagnetic waves will affect each other in various combinations of components. The mutual influence of electromagnetic waves between adjacent components can cause the signal of one component to become noise in the signal of another component, and vice versa. In other words, as the wiring density in a multilayer wiring board increases, it is expected that crosstalk caused by the influence of electromagnetic waves between components will increase. Patent Document 1 leaves room for improvement in terms of suppressing and reducing such crosstalk.

[0005] In one aspect, the multilayer wiring board and the electronic device including the same disclosed in this specification aim to effectively suppress crosstalk. [Means for solving the problem]

[0006] In one aspect, the multilayer wiring board is a multilayer wiring board having at least a first signal layer and multiple ground layers along a stacking direction, and includes: a first differential wiring provided on the first signal layer and including a first wiring and a second wiring; other signal lines provided on the first signal layer; a signal via extending along the stacking direction and electrically connected to the other signal lines; and a ground via extending along the stacking direction and electrically connected to the ground layer, wherein the first differential wiring includes a first portion, a second portion continuous with the first portion, and a third portion continuous with the second portion, wherein the first wiring is arranged between the ground via and the signal via adjacent to the ground via, and the second wiring is arranged on the opposite side of the first wiring across the ground via, and the ground via is sandwiched between the first wiring and the second wiring.

[0007] In another aspect, an electronic device includes a multilayer wiring board having at least a first signal layer and a plurality of ground layers along a stacking direction, the multilayer wiring board including: a first differential wiring provided on the first signal layer and including a first wiring and a second wiring; another signal line provided on the first signal layer; a signal via extending along the stacking direction and electrically connected to the other signal line; and a ground via extending along the stacking direction and electrically connected to the ground layer, the first differential wiring including a first portion, a second portion continuous with the first portion, and a third portion continuous with the second portion, the first wiring being disposed between the ground via and the signal via adjacent to the ground via, the second wiring being disposed on the opposite side of the first wiring across the ground via, the first wiring and the second wiring sandwiching the ground via between them; and an electronic component mounted on the multilayer wiring board. [Effects of the Invention]

[0008] According to the multilayer wiring board and the electronic device including the same disclosed in this specification, crosstalk can be effectively suppressed. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a plan view showing an example of an electronic device in which electronic components are mounted on a multilayer wiring board according to an embodiment. [Figure 2] FIG. 2 is a plan view showing a partial region of the multilayer wiring board according to the embodiment. [Figure 3] 3 is a cross-sectional view of the multilayer wiring board of the embodiment taken along line A1-A1 in FIG. [Figure 4] 4 is an enlarged cross-sectional view showing a part of the cross-sectional view taken along the line A1-A1 shown in FIG. [Figure 5] 5 is a cross-sectional view of the multilayer wiring board of the embodiment taken along line A2-A2 in FIG. [Figure 6] Fig. 6(A) is a plan view showing a partial area of ​​the first signal layer in which the first differential wiring and the second differential wiring are provided. Fig. 6(B) is a plan view showing a partial area of ​​the second signal layer in which the third differential wiring is provided. Fig. 6(C) is a plan view showing a partial area of ​​the ground layer. Fig. 6(D) is a plan view showing a partial area of ​​the shielding ground layer. [Figure 7] FIG. 7 is an explanatory diagram showing how the first differential wiring surrounds the ground via in the multilayer wiring board of the embodiment. [Figure 8] FIG. 8 is an enlarged view of the periphery of a clearance portion provided in the multilayer wiring board of the embodiment. [Figure 9] FIG. 9 is a plan view showing a partial region of a multilayer wiring board of a comparative example. [Figure 10] FIG. 10 is a cross-sectional view of the multilayer wiring board of the comparative example taken along line A3-A3 in FIG. [Figure 11] 11A is a graph showing the results of EYE analysis of the multilayer wiring board of the embodiment, and FIG. 11B is a graph showing the results of EYE analysis of the multilayer wiring board of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, ratios, etc. of each part in the drawings may not be illustrated to be exactly the same as the actual ones. The scales of the drawings may differ. Furthermore, in some drawings, for the sake of explanation, components that actually exist may be omitted or dimensions may be exaggerated.

[0011] (Embodiment) An electronic device 100 according to an embodiment will be described with reference to FIGS. 1 to 8. Referring to FIG. 1, the electronic device 100 is formed by mounting electronic components 101 on a multilayer wiring substrate (hereinafter simply referred to as "substrate") 1. FIG. 2 is a plan view showing a partial region of the substrate 1. FIG. 3 is a cross-sectional view of the substrate 1 taken along line A1-A1 in FIG. 2, and FIG. 4 is an enlarged cross-sectional view of a portion thereof. FIG. 5 is a cross-sectional view of the substrate 1 taken along line A2-A2 in FIG. 2. FIG. 6(A) is a plan view showing a partial region of the first signal layer 10a (see FIGS. 3 and 4) on which the first differential wiring 20 and the second differential wiring 22 are provided. FIG. 6(B) is a plan view showing a partial region of the second signal layer 10b (see FIGS. 3 and 4) on which the third differential wiring 24 is provided. FIG. 6(C) is a plan view showing a partial region of the ground layer 40 (see FIGS. 3 and 4). 6(D) is a plan view showing a partial area of ​​the shielding ground layers 40a, 40b, and 40c (see FIGS. 3 and 4). Note that, to make it easier to distinguish between the first differential wiring 20, the second differential wiring 22, and the third differential wiring 24, these differential wirings are shown using different line types in FIGS. 2 and 8. Specifically, the first differential wiring 20 and the second differential wiring 22 provided on the first signal layer 10a are shown by dotted lines, and the third differential wiring 24 provided on the second signal layer 10b is shown by dashed lines.

[0012] The substrate 1 includes a first signal layer 10a, a second signal layer 10b, and a ground layer 40 stacked along the stacking direction shown in Fig. 3. The substrate 1 also includes a first signal via 30a and a second signal via 30b extending along the stacking direction. The substrate 1 also includes a plurality of ground vias 50a and the like extending along the stacking direction.

[0013] As shown in FIG. 6A, the first signal layer 10a is provided with first differential wiring 20 and second differential wiring 22. The second differential wiring 22 corresponds to another signal line provided on the first signal layer 10a. The first differential wiring 20 includes a first wiring 20a and a second wiring 20b. That is, the first differential wiring 20 is formed by a pair of the first wiring 20a and the second wiring 20b. The second differential wiring 22 includes a third wiring 22a and a fourth wiring 22b. That is, the second differential wiring 22 is formed by a pair of the third wiring 22a and the fourth wiring 22b. The first differential wiring 20 and the second differential wiring 22 can be formed by a conventionally known method, such as by etching a resin layer serving as an insulating material that forms the first signal layer 10a. The first signal layer 10a may include signal lines other than the first differential wiring 20 and the second differential wiring 22. 6(A) also illustrates differential wiring other than the first differential wiring 20 and the second differential wiring 22. Note that in the cross-sectional views shown in FIGS. 3 to 5, hatching of resin layer portions forming the first signal layer 10a, the second signal layer 10b, and the ground layer 40 is omitted.

[0014] The first signal via 30a and the second signal via 30b are paired to form a differential signal via pair 30. In the state shown in FIG. 2, the first signal via 30a and the second signal via 30b have a positional relationship that slopes downward to the right. In other words, when the second signal via 30b is used as a reference, the first signal via 30a is located to the lower right of the second signal via 30b. The differential signal via pair 30 is electrically connected to the second differential wiring 22. Specifically, the third wiring 22a is electrically connected to the first signal via 30a. The fourth wiring 22b is electrically connected to the second signal via 30b. Note that the substrate 1 has differential signal via pairs in areas other than those shown in each figure, and the first differential wiring 20 is electrically connected to a differential signal via pair not shown. Both ends of the first signal via 30a and the second signal via 30b face the surface layer of the substrate 1, and conductor portions 31 are provided on each end. The conductor portion 31 is used for soldering when the electronic component 101 is mounted.

[0015] As shown in FIG. 6B, the second signal layer 10b is provided with third differential wiring 24. The third differential wiring 24 corresponds to another signal line provided on the second signal layer 10b. The third differential wiring 24 includes a fifth wiring 24a and a sixth wiring 24b. That is, the third differential wiring 24 is formed by a pair of the fifth wiring 24a and the sixth wiring 24b. The third differential wiring 24 is electrically connected to a differential signal via pair (not shown). In this embodiment, the first signal layer 10a and the second signal layer 10b are provided, but a configuration including more signal layers may also be used. Furthermore, the second signal layer 10b may include signal lines other than the third differential wiring 24.

[0016] A plurality of ground layers 40 are provided. Of the plurality of ground layers 40, the layer provided between the first signal layer 10a and the second signal layer 10b is the first shielding ground layer 40a. The first shielding ground layer 40a is the layer directly above the first signal layer 10a and directly below the second signal layer 10b. Of the plurality of ground layers 40, the layer provided below the first signal layer 10a is the second shielding ground layer 40b. The second shielding ground layer 40b is the layer directly below the first signal layer 10a. Of the plurality of ground layers 40, the layer provided above the second signal layer 10b is the third shielding ground layer 40c. The third shielding ground layer 40c is the layer directly above the second signal layer 10b.

[0017] As a result, in this embodiment, shielding ground layers are provided above and below the first signal layer 10a, and shielding ground layers are provided above and below the second signal layer 10b.

[0018] The shielding ground layers 40a, 40b, and 40c shield electromagnetic waves associated with signal transmission on the substrate 1 and can reduce crosstalk between the second differential wiring 22 and the third differential wiring 24. As shown in FIGS. 6(C) and 6(D), the ground layer 40 includes wiring, i.e., a ground plane pattern 401. The ground layers 40 other than the shielding ground layers 40a, 40b, and 40c include a first clearance area 601 formed between the ground plane pattern 401 and the differential signal via pair 30. The shielding ground layers 40a, 40b, and 40c include a second clearance area 602 formed between the ground plane pattern 401 and the differential signal via pair 30, and also include an eave portion 61. The ground layer 40 including the first clearance area 601 and the shielding ground layers 40a, 40b, and 40c including the second clearance area 602 are stacked together to form the clearance portion 60. The clearance portion 60, the second clearance region 602, and the overhang portion 61 will be described in detail later.

[0019] The substrate 1 includes ground vias 50a to 50j in the region shown in FIG. 2. Both ends of the ground vias 50a to 50j face the surface layer of the substrate 1, and are provided with conductor portions 51. The ground vias 50a to 50j are electrically connected to the ground layer 40. The ground vias 50a to 50j, together with the first signal via 30a and the second signal via 30b, are arranged in a grid pattern when the substrate 1 is viewed in the stacking direction. In FIG. 2, the ground vias 50a, 50b, and 50c are arranged in the same row. The ground via 50d, the second signal via 30b, and the ground via 50e are arranged in the same row. The ground via 50f, the first signal via 30a, and the ground via 50g are arranged in the same row. The ground vias 50h, 50i, and 50j are arranged in the same row. Adjacent rows are shifted by half a column in the left-right direction in FIG. 2. The arrangement of the vias shown in FIG. 2 is an example and is not limited to this.

[0020] [Differential wiring route] Next, the wiring paths of the differential wiring in the first signal layer 10a will be described in detail. Here, the first differential wiring 20 will be described in particular. Referring to FIG. 7, the first differential wiring 20 includes a first portion 201, a second portion 202a, a third portion 202b, a fourth portion 202c, and a fifth portion 203. Differential wiring can have various wiring paths, but in general, the distance between two wires in a pair is generally constant even when the path is curved. In contrast, the first differential wiring 20 of this embodiment has portions where the distance between the two wires varies, as will be described below.

[0021] The first wiring 20a and the second wiring 20b in the first portion 201 are parallel to each other, and are spaced apart by a distance S1.

[0022] The second portion 202a is a portion continuous with the first portion 201. In the second portion 202a, the distance between the first wiring 20a and the second wiring 20b varies depending on the position along the wiring path of the first differential wiring 20. Specifically, the distance between the first wiring 20a and the second wiring 20b in the second portion 202a becomes larger than the distance S1 as the distance increases from the first portion 201. In the second portion 202a, the distance between the first wiring 20a and the second wiring 20b is largest at the end opposite to the end continuous with the first portion 201, and this distance is distance S2.

[0023] The third portion 202b is a portion that is continuous with the second portion 202a. The third portion 202b is continuous with the second portion 202a on the side opposite to the first portion 201. In the third portion 202b, the first wiring 20a and the second wiring 20b are parallel to each other, and the distance between them is a distance S2.

[0024] In the second portion 202a of this embodiment, the distance between the first wiring 20a and the second wiring 20b gradually increases from the first portion 201 toward the third portion 202b. However, the second portion 202a may have other configurations as long as it can connect the first portion 201 and the third portion 202b, which have different distances between the first wiring 20a and the second wiring 20b. For example, the angle at the connection between the first portion 201 and the second portion 202a may be approximately a right angle, and the angle at the connection between the second portion 202a and the third portion 202b may also be approximately a right angle. Furthermore, the second portion 202a may be curved to connect the first portion 201 and the third portion 202b.

[0025] 2, the ground via 50f and the first signal via 30a are adjacent to each other in the left-right direction. In the third portion 202b, the first wiring 20a is disposed between the ground via 50f and the first signal via 30a. The second wiring 20b is disposed on the opposite side of the first wiring 20a across the ground via 50f. As a result, in the third portion 202b, the ground via 50f is sandwiched between the first wiring 20a and the second wiring 20b.

[0026] The fourth portion 202c is a portion continuous with the third portion 202b. The fourth portion 202c is continuous with the third portion 202b on the opposite side from the second portion 202a. In the fourth portion 202c, the distance between the first wiring and the second wiring varies depending on the position along the wiring path of the first differential wiring. Specifically, the distance between the first wiring 20a and the second wiring 20b in the fourth portion 202c becomes smaller than the distance S2 as the distance increases from the third portion 202b. In the fourth portion 202c, the distance between the first wiring 20a and the second wiring 20b is smallest at the end opposite the end continuous with the third portion 202b, and this distance is the distance S3. In this embodiment, the distance S1 and the distance S3 are approximately equal. That is, the minimum distance between the first wiring 20a and the second wiring 20b in the fourth portion 202c is the same as the distance between the first wiring 20a and the second wiring 20b in the first portion 201. However, the distance S3 and the distance S1 may be different, as long as the distance S2 is greater than the distance S3.

[0027] The fifth portion 203 is a portion that is continuous with the fourth portion 202c. The fifth portion 203 is continuous with the fourth portion 202c on the side opposite to the third portion 202b. The first wiring 20a and the second wiring 20b in the fifth portion 203 are parallel to each other, and the distance between them is a distance S3. In this embodiment, the distance S3 is approximately equal to the distance S1. However, as described above, the distance S3 may be different from the distance S1. The fifth portion 203 allows the first differential wiring 20 to pass between ground vias.

[0028] In the fourth portion 202c of this embodiment, the distance between the first wiring 20a and the second wiring 20b gradually narrows from the third portion 202b toward the fifth portion 203. However, the fourth portion 202c may have other configurations as long as it can connect the third portion 202b, which has a different distance between the first wiring 20a and the second wiring 20b, to the fifth portion 203. For example, the angle at the connection between the third portion 202b and the fourth portion 202c may be approximately a right angle, and the angle at the connection between the fourth portion 202c and the fifth portion 203 may also be approximately a right angle. Furthermore, the fourth portion 202c may be curved to connect the third portion 202b and the fifth portion 203.

[0029] In this manner, the substrate 1 of this embodiment forms the surrounding portion 202 that surrounds the ground via 50f with the second portion 202a, the third portion 202b, and the fourth portion 202c.

[0030] Forming the enclosure 202 allows only the first wiring 20a to pass between the ground via 50f and the first signal via 30a. Since only one wiring needs to be provided between the ground via 50f and the first signal via 30a, the degree of freedom in arranging the differential wiring is improved in the substrate 1 having high wiring density. As a result, in the substrate 1 having high wiring density, the distance between the differential signal via pair 30 connected to the second differential wiring 22 and the first differential wiring 20 can be increased, and crosstalk caused by electromagnetic wave interference can be suppressed and reduced.

[0031] 2, the distance R1 between the first wiring 20a and the ground via 50f and the distance R2 between the first wiring 20a and the first signal via 30a will be described. Referring to FIG. 2, the distance R2 is wider than the distance R1. That is, in the third portion 202b, the first wiring 20a can be positioned closer to the ground via 50f and further away from the first signal via 30a.

[0032] The first wiring 20a belongs to the first differential wiring 20. A second differential wiring 22, which is different from the first differential wiring 20, is connected to the first signal via 30a. Therefore, there is a possibility that both signals may become noise to each other. To address this phenomenon, in the substrate 1 of this embodiment, the interval R2 is set wide and the first wiring 20a is positioned away from the first signal via 30a, thereby avoiding electromagnetic wave interference. As a result, both signals are prevented from becoming noise to each other, and crosstalk is suppressed.

[0033] The position where the enclosure 202 is formed can be appropriately determined taking into consideration the entire wiring path on the substrate 1. In the example shown in FIG. 2, the enclosure may be formed where the ground via 50d and the second signal via 30b are adjacent to each other depending on the wiring path. Alternatively, the enclosure may be formed where the ground via 50a and the second signal via 30b are adjacent to each other, or where the ground via 50i and the first signal via 30a are adjacent to each other. The enclosure can also be formed in a similar manner when a differential wiring other than the first differential wiring 20 is disposed near the differential signal via pair 30. FIG. 6A illustrates an enclosure surrounding the ground via 50g. Although the present embodiment only describes the wiring path within the region shown in FIG. 2, a wiring path similar to the enclosure 202 can also be set in a region not shown in FIG. 2.

[0034] Furthermore, although the present embodiment describes the setting of the enclosure 202 in the first signal layer 10a, enclosures can be set in a similar manner in other signal layers. Referring to FIG. 6B, an enclosure surrounding the ground via 50e is also formed in the third differential wiring 24 provided in the second signal layer 10b. Forming an enclosure in the third differential wiring 24 is also effective in separating the sixth wiring 24b from the differential signal via pair 30. Overlapping of differential wirings in the clearance portion 60 (described later) can cause crosstalk between the differential wirings. Forming an enclosure and placing a single wiring between the ground via and the first signal via 30a or the second signal via 30b makes it easier to avoid overlapping of differential wirings in the clearance portion 60.

[0035] [Shielding structure] 2 and 3, the substrate 1 has a clearance portion 60. The clearance portion 60 is formed by a first clearance area 601 provided in the ground layer 40 shown in Fig. 6(C) and a second clearance area 602 provided in the shielding ground layers 40a, 40b, and 40c shown in Fig. 6(D).

[0036] The clearance portion 60 can increase the impedance value of the differential signal via pair 30 portion. In boards with high-density wiring, the diameter of signal vias tends to be smaller, making it difficult to achieve the ideal impedance value, e.g., 50 Ω, in the differential signal via pair portion. The impedance value is inversely proportional to the square root of the via diameter and increases as the capacitance decreases. Therefore, the board 1 of this embodiment includes a clearance portion 60 having a generally oval shape in the ground layer 40 through which the differential signal via pair 30 passes. The impedance value of the via portion can be increased by increasing the dimensions along the major axis and the minor axis of the clearance portion 60 and thereby reducing the capacitance of the differential signal via pair 30 portion. Therefore, the dimensions along the major axis and the minor axis of the clearance portion 60 are set to obtain the desired impedance value.

[0037] However, there is a concern that determining the dimensions of the clearance portion 60 in this manner may increase crosstalk due to the influence of mutual electromagnetic waves between the second differential wiring 22 formed on the first signal layer 10a and the third differential wiring 24 formed on the second signal layer 10b.

[0038] Therefore, in this embodiment, first, an overhang portion 61 is provided on the first shielding ground layer 40a, which is disposed between the first signal layer 10a and the second signal layer 10b. The overhang portion 61 is provided so as to protrude inward into the second clearance area 602. Referring to FIG. 6(D), the ground plane pattern 401 is formed toward the inside of the second clearance area 602, thereby providing the overhang portion 61.

[0039] The first clearance region 601 has a shape in which, when the arrangement direction of the first signal via 30a and the second signal via 30b is the long diameter direction, the dimension in the short diameter direction of the central part in the long diameter direction is approximately equal to the diameter of the circular part located at the end in the long diameter direction.

[0040] In contrast, the second clearance region 602 has a shape in which the dimension in the minor axis direction of the central part in the major axis direction is smaller than the diameter of the circular part located at the end in the major axis direction. In other words, the provision of the overhanging part 61 gives the second clearance region 602 a gourd shape with a constriction in the central part of the oval or elliptical shape.

[0041] The overhanging portion 61 is located between the third wiring 22a included in the second differential wiring 22 and the sixth wiring 24b included in the third differential wiring 24. Specifically, the overhanging portion 61 is formed in a range that covers the overlapping portion between the second differential wiring 22 and the third differential wiring 24 when the substrate 1 is viewed from the stacking direction. In this way, by preventing the overlapping portion between the second differential wiring 22 and the third differential wiring 24 from being exposed in the clearance portion 60, crosstalk between the second differential wiring 22 and the third differential wiring 24 can be reduced.

[0042] In this embodiment, a second shielding ground layer 40b is provided, which is formed in the same manner as the first shielding ground layer 40a. This provides shielding ground layers above and below the first signal layer 10a. This prevents electromagnetic waves generated by signal transmission in the second differential wiring 22 provided on the first signal layer 10a from sneaking into the second signal layer 10b.

[0043] In addition, in this embodiment, a third shielding ground layer 40c is provided, which is formed in the same manner as the first shielding ground layer 40a. This provides shielding ground layers above and below the second signal layer 10b. This prevents electromagnetic waves generated by signal transmission through the third differential wiring 24 provided on the second signal layer 10b from sneaking into the first signal layer 10a.

[0044] As a result, in this embodiment, crosstalk between the second differential wiring 22 and the third differential wiring 24 is reduced.

[0045] Of the first, second, and third shielding ground layers 40a, 40b, and 40c, only the first shielding ground layer 40a may be provided.

[0046] Furthermore, if multiple ground layers 40 are provided between the first signal layer 10a and the second signal layer 10b, at least one of the multiple ground layers 40 can be the first shielding ground layer 40a.

[0047] If multiple ground layers 40 are provided between the first signal layer 10a and the second signal layer 10b, shielding ground layers may be provided above and below each of the first signal layer 10a and the second signal layer 10b. In this case, four shielding ground layers will be provided. By providing shielding ground layers above and below the first signal layer 10a and by providing shielding ground layers above and below the second signal layer 10b, crosstalk can be reduced more effectively.

[0048] In the substrate 1, the clearance portion 60 maintains a predetermined dimension to obtain a desired impedance value. The overhang portion 61 covers the overlapping portion between the second differential wiring 22 and the third differential wiring 24 while maintaining the dimension of the clearance portion 60 that allows the desired impedance value to be obtained. In other words, the substrate 1 can obtain a desired impedance value and reduce crosstalk between the second differential wiring 22 and the third differential wiring 24.

[0049] The shape of the overhanging portion 61, in other words, the shape of the second clearance region 602, is not limited to a so-called gourd shape. In this embodiment, the overhanging portion 61 has a shape that is symmetrical with respect to an axis extending in the major axis direction. However, the overhanging portion 61 may have a shape that protrudes inward from the second clearance region 602 only in one of the regions on the left and right of the axis.

[0050] In short, the overhanging portion 61 may have any shape as long as it is formed in a range that covers the overlapping portion between the second differential wiring 22 and the third differential wiring 24 when the substrate 1 is viewed from the stacking direction.

[0051] The first signal layer 10a is provided with first differential wiring 20, which is connected to a differential signal via pair arranged in an area not shown. A clearance portion is also provided around the differential signal via pair. In this case, if there is a location where the first differential wiring 20 faces wiring provided on another signal layer in the stacking direction, a canopy portion can be provided as necessary.

[0052] In this embodiment, the shielding ground layers 40a, 40b, and 40c on which the eaves portion 61 is provided are set in relation to the second differential wiring 22 and the third differential wiring 24, but the shielding ground layers can be set appropriately based on the relationship of other differential wirings.

[0053] [Crosstalk reduction effect] Here, the crosstalk reduction effect of this embodiment will be described in comparison with a comparative example, with reference to Figs. 9 to 11(B). Fig. 9 is a plan view showing a partial region of substrate 5 of the comparative example. Fig. 10 is a cross-sectional view of the substrate of the comparative example taken along line A3-A3 in Fig. 9. Fig. 11(A) is a graph showing the results of EYE analysis of substrate 1 of this embodiment. Fig. 11(B) is a graph showing the results of EYE analysis of substrate 5 of the comparative example.

[0054] First, the substrate 5 of the comparative example will be described in comparison with the substrate 1 of the embodiment. The substrate 5 includes a fourth differential wiring 120, a fifth differential wiring 122, and a sixth differential wiring 124. The fourth differential wiring 120 corresponds to the first differential wiring 20 in the substrate 1, and includes a seventh wiring 120a and an eighth wiring 120b. The fifth differential wiring 122 corresponds to the second differential wiring 22 in the substrate 1, and includes a ninth wiring 122a and a tenth wiring 122b. The sixth differential wiring 124 corresponds to the third differential wiring 24 in the substrate 1, and includes an eleventh wiring 124a and a twelfth wiring 124b.

[0055] The arrangement of the ground vias and differential signal via pairs is the same as that of the substrate 1, and is denoted by the same reference numerals in the drawings. Furthermore, the fourth differential wiring 120 and the fifth differential wiring 122 are provided on the first signal layer 10a, and the sixth differential wiring 124 is provided on the second signal layer 10b. The substrate 5 is also common to the substrate 1 in this respect. However, the ground layer 40 disposed between the first signal layer 10a and the second signal layer 10b is common to the other ground layers 40, and only includes a first clearance region 601 (see FIG. 6(C)). Furthermore, the ground layer 40 disposed below the first signal layer 10a and the ground layer 40 disposed above the second signal layer 10b also only includes a first clearance region 601 (see FIG. 6(C)). In other words, the substrate 5 does not include a canopy portion 61, and the clearance portion 60 is formed only by the first clearance region 601.

[0056] The distance between each pair of wires in the fourth differential wiring 120, the fifth differential wiring 122, and the sixth differential wiring 124 is generally constant. Therefore, two wires, the seventh wiring 120a and the eighth wiring 120b, are arranged between the ground via 50f and the first signal via 30a. As a result, the distance between the seventh wiring 120a and the first signal via 30a is narrower than the distance R2 between the first wiring 20a and the first signal via 30a on the substrate 1. Therefore, crosstalk between the seventh wiring 120a and the first signal via 30a is more likely to occur on the substrate 5 than on the substrate 1.

[0057] As shown in FIG. 9 , in the substrate 5, the twelfth wiring 124b of the sixth differential wiring 124 faces a position overlapping with the clearance portion 60. This is because two wirings are arranged between the second signal via 30b and the ground via 50e, and as a result, the twelfth wiring 124b is close to the second signal via 30b. Furthermore, this is because the substrate 5 does not include an overhang portion 61. As a result, in the substrate 5, as shown in FIG. 10 , the tenth wiring 122b and the twelfth wiring 124b are directly opposed to each other in the clearance portion 60. Here, the tenth wiring 122b and the twelfth wiring 124b being directly opposed to each other means that the tenth wiring 122b and the twelfth wiring 124b are opposed to each other without the ground solid pattern 401 (see FIG. 6D ) being present between them. As a result, crosstalk between the fifth differential wiring 122 and the sixth differential wiring 124 is likely to occur.

[0058] Referring now to FIG. 11(A), which shows the results of the eye analysis of the substrate 1 of the embodiment, the eye-shaped opening width is W1 and the opening height is h1. Meanwhile, referring to FIG. 11(B), which shows the results of the eye analysis of the substrate 5 of the comparative example, the eye-shaped opening width is W0 and the opening height is h0. Comparing the respective dimensions, the opening width W1 > opening width W0 and the opening height h1 > opening height h0. While a detailed explanation of the eye analysis will be omitted here, the results of the eye analysis show that the larger the dimensions of the eye-shaped opening, the better the transmission characteristics and the higher the speed of signal transmission. Therefore, comparing the substrate 1 of the embodiment with the substrate 5 of the comparative example, it can be seen that the transmission characteristics of the substrate 1 are better.

[0059] This is thought to be because crosstalk was reduced by reducing electromagnetic wave interference between the differential wiring and the signal vias due to the wiring configuration of the substrate 1. Furthermore, it is thought that crosstalk was reduced because the provision of the overhanging portion 61 reduced electromagnetic wave interference between the differential wirings located above and below.

[0060] The reduced crosstalk and improved transmission characteristics enable accurate signal transmission even under conditions where signal speeds are increased. The substrate 1 of this embodiment can be applied to electronic devices that can be used in AI learning devices and electronic devices capable of high-speed calculations. The substrate 1 of this embodiment can enable accurate signal transmission even when high-speed signal transmission is performed in these electronic devices.

[0061] [effect] The effects of the substrate disclosed in this specification will be described below.

[0062] In the substrate 1 disclosed in this specification, the first wiring 20a of the first differential wiring 20 is disposed between the ground via 50f and the first signal via 30a. The second wiring 20b of the first differential wiring 20 is disposed on the opposite side of the first wiring 20a, with the ground via 50f in between. The ground via 50f is sandwiched between the first wiring 20a and the second wiring 20b. This allows the distance between the first wiring 20a of the first differential wiring 20 and the first signal via 30a to be widened, suppressing mutual electromagnetic wave interference between them and reducing crosstalk.

[0063] The first differential wiring 20 includes a fourth portion 202c that is continuous with a third portion 202b, where the first wiring 20a and the second wiring 20b sandwich the ground via 50f. In the fourth portion 202c, the distance between the first wiring 20a and the second wiring 20b varies depending on the position along the wiring path of the first differential wiring 20. The distance between the first wiring 20a and the second wiring 20b at the end opposite to the end that is continuous with the third portion 202b is narrower than the distance between the first wiring 20a and the second wiring 20b in the third portion 202b. The fourth portion 202c is continuous with a fifth portion 203, where the first wiring 20a and the second wiring 20b are parallel to each other. This allows the first wiring 20a and the second wiring 20b to pass between other ground vias. In the example shown in FIG. 2, the first wiring 20a and the second wiring 20b can pass between the ground via 50h and the ground via 50i.

[0064] The distance between the first wiring 20a and the first signal via 30a in the third portion 202b of the first differential wiring 20 is wider than the distance between the first wiring 20a and the ground via 50f in the third portion 202b. In other words, by arranging the first wiring 20a and the first signal via 30a at a distance from each other, crosstalk between them can be suppressed and reduced.

[0065] In the substrate 1, a first shielding ground layer 40a is disposed between a first signal layer 10a on which the second differential wiring 22 is formed and a second signal layer 10b on which the third differential wiring 24 is formed. The first shielding ground layer 40a includes a second clearance area 602 formed between a ground plane pattern 401 and the differential signal via pair 30. The first shielding ground layer 40a also includes an eave portion 61 that protrudes inward from the second clearance area 602. The eave portion 61 of the first shielding ground layer 40a is located between the second differential wiring 22 and the third differential wiring 24. This suppresses crosstalk between the second differential wiring 22 and the third differential wiring 24.

[0066] When the substrate 1 is viewed from the stacking direction, the overhanging portion 61 is formed in a range that covers the overlapping portion between the second differential wiring 22 and the third differential wiring 24. This effectively suppresses crosstalk between the second differential wiring 22 and the third differential wiring 24.

[0067] In the substrate 1, a second shielding ground layer 40b is disposed below the first signal layer 10a. The second shielding ground layer 40b has a second clearance area 602 and an eave portion 61, similar to the first shielding ground layer 40a. The second shielding ground layer 40b, together with the first shielding ground layer 40a, can suppress the leakage of electromagnetic waves emitted by the second differential wiring 22. This suppresses crosstalk between the second differential wiring 22 and the third differential wiring 24.

[0068] On the substrate 1, a third shielding ground layer 40c is disposed above the second signal layer 10b. The third shielding ground layer 40c has a second clearance area 602 and an eave portion 61, similar to the first shielding ground layer 40a. The third shielding ground layer 40c, together with the first shielding ground layer 40a, can suppress the leakage of electromagnetic waves emitted by the third differential wiring 24. This suppresses crosstalk between the second differential wiring 22 and the third differential wiring 24.

[0069] In the above embodiment, an example has been described in which the other signal lines provided in the first signal layer 10a are the second differential lines 22, and the other signal lines provided in the second signal layer 10b are the third differential lines 24. The other signal lines provided in the first signal layer 10a and the other signal lines provided in the second signal layer 10b do not necessarily have to be differential lines, and may be other forms of wiring.

[0070] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0071] 1...multilayer wiring board, 10a...first signal layer, 10b...second signal layer, 20...first differential wiring, 20a...first wiring, 20b...second wiring, 22...second differential wiring, 22a...third wiring, 22b...fourth wiring, 24...third differential wiring, 24a...fifth wiring, 24b...sixth wiring, 30...differential signal via pair, 30a...first signal via, 30b...second signal via, 40...ground layer, 40a, 40b, 40c...shielding ground layer, 401...ground solid pattern, 50a to 50j...ground via, 60...clearance portion, 61...eaves portion, 201 First portion, 202...enclosure portion, 202a...second portion, 202b...third portion, 202c...fourth portion, 100...electronic device, 101...electronic component, 601...first clearance area, 602...second clearance area

Claims

1. A multilayer wiring board having at least a first signal layer and a plurality of ground layers along a lamination direction, a first differential wiring provided on the first signal layer and including a first wiring and a second wiring; Another signal line provided on the first signal layer; a signal via extending along the stacking direction and electrically connected to the other signal line; a ground via extending along the stacking direction and electrically connected to the ground layer, the first differential wiring includes a first portion, a second portion continuous with the first portion, and a third portion continuous with the second portion, the first wiring being disposed between the ground via and the signal via adjacent to the ground via, the second wiring being disposed on the opposite side of the first wiring across the ground via, and the ground via being sandwiched between the first wiring and the second wiring; A multilayer wiring board comprising:

2. the other signal line provided on the first signal layer is a second differential line including a third line and a fourth line, the signal via is either a first signal via extending along the stacking direction and electrically connected to the third wiring, or a second signal via extending along the stacking direction and electrically connected to the fourth wiring; The multilayer wiring board according to claim 1 .

3. the first differential wiring further includes a fourth portion continuous with the third portion, and a fifth portion continuous with the fourth portion, the fifth portion having a narrower distance between the first wiring and the second wiring than the distance between the first wiring and the second wiring in the third portion; The multilayer wiring board according to claim 1 .

4. a distance between the first wiring and the signal via in the third portion is wider than a distance between the first wiring and the ground via in the third portion; The multilayer wiring board according to claim 1 .

5. further including another signal line provided on a second signal layer different from the first signal layer; Among the plurality of ground layers, the ground layer disposed between the first signal layer and the second signal layer is a shielding ground layer having a clearance region formed between the wiring of the ground layer and the signal via, and a canopy portion protruding toward the inside of the clearance region and positioned between the other signal line provided on the first signal layer and the other signal line provided on the second signal layer. The multilayer wiring board according to claim 1 .

6. the other signal line provided on the first signal layer is a second differential line including a third line and a fourth line, the other signal line provided on the second signal layer is a third differential line including a fifth line and a sixth line, the overhanging portion is located between the second differential wiring and the third differential wiring. The multilayer wiring board according to claim 5 .

7. the overhanging portion is formed in a range that covers an overlapping portion between the other signal line provided on the first signal layer and the other signal line provided on the second signal layer when the multilayer wiring board is viewed from the stacking direction. The multilayer wiring board according to claim 5 .

8. further including another signal line provided on a second signal layer different from the first signal layer; Among the plurality of ground layers, the ground layers arranged above and below the first signal layer are shielding ground layers each having a clearance region formed between the wiring of the ground layer and the signal via, and a canopy portion that protrudes inward from the clearance region and is positioned in a range that covers an overlapping portion between the other signal line provided on the first signal layer and the other signal line provided on the second signal layer when the multilayer wiring board is viewed from the stacking direction. The multilayer wiring board according to claim 1 .

9. the other signal line provided on the first signal layer is a second differential line including a third line and a fourth line, the other signal line provided on the second signal layer is a third differential line including a fifth line and a sixth line; The multilayer wiring board according to claim 8 .

10. further including another signal line provided on a second signal layer different from the first signal layer; Among the plurality of ground layers, the ground layers arranged above and below the second signal layer are shielding ground layers each having a clearance region formed between the wiring of the ground layer and the signal via, and a canopy portion that protrudes inward from the clearance region and is positioned in a range that covers an overlapping portion between the other signal line provided on the first signal layer and the other signal line provided on the second signal layer when the multilayer wiring board is viewed from the stacking direction. The multilayer wiring board according to claim 1 .

11. the other signal line provided on the first signal layer is a second differential line including a third line and a fourth line, the other signal line provided on the second signal layer is a third differential line including a fifth line and a sixth line; The multilayer wiring board according to claim 10.

12. a multilayer wiring board having at least a first signal layer and a plurality of ground layers along a lamination direction, the multilayer wiring board including: a first differential wiring provided on the first signal layer and including a first wiring and a second wiring; another signal line provided on the first signal layer; a signal via extending along the lamination direction and electrically connected to the other signal line; and a ground via extending along the lamination direction and electrically connected to the ground layer, the first differential wiring including: a first portion, a second portion continuous with the first portion, and a third portion continuous with the second portion, the first wiring being disposed between the ground via and the signal via adjacent to the ground via, the second wiring being disposed on the opposite side of the first wiring across the ground via, the first wiring and the second wiring sandwiching the ground via; an electronic component mounted on the multilayer wiring board; An electronic device comprising:

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