Wiring board and mounting structure

Abstract

A wiring board according to the present disclosure includes: a core layer having a first surface and a second surface on a side opposite to the first surface; a first build-up layer positioned on the first surface and having a third surface on a side opposite to the first surface; a second build-up layer positioned on the second surface and having a fourth surface on a side opposite to the second surface; at least two first pads positioned on the third surface and at least two second pads positioned on the fourth surface; and a differential conductor connected to two first pads of the at least two first pads and two second pads of the at least two second pads.

Description

Wiring board and mounting structure

[0001] The present invention relates to a wiring board and a mounting structure using the same.

[0002] Conventionally, a wiring board for mounting electronic components and the like has pads for connecting electronic components located at the center of the upper surface (mounting area) of the wiring board and pads for external connection located on the lower surface of the wiring board, as described in, for example, Patent Document 1.

[0003] Japanese Patent No. 6034279

[0004] The wiring board according to the present disclosure includes a core layer having a first surface and a second surface on the opposite side of the first surface, a first build-up layer located on the first surface and having a third surface on the opposite side of the first surface, a second build-up layer located on the second surface and having a fourth surface on the opposite side of the second surface, at least two first pads located on the third surface and at least two second pads located on the fourth surface, and a differential conductor connected to two of the at least two first pads and two of the at least two second pads. The differential conductor has, in the first build-up layer, a pair of paired wirings located along each other and first lands each connected to the paired wirings, and, in the core layer, two through-hole conductors located side by side with each other. When a virtual straight line passing through the centers of the two through-hole conductors is defined as a first virtual straight line in a plan view, the paired wirings are located along the first virtual straight line with the first virtual straight line interposed therebetween. When a virtual straight line passing through the centers of the first lands each connected to the paired wirings is defined as a second virtual straight line in a plan view, the second virtual straight line is orthogonal to the first virtual straight line between the centers of the two through-hole conductors.

[0005] The mounting structure according to the present disclosure includes the above wiring board and an electronic component mounted on the wiring board.

[0006] This is an enlarged explanatory diagram illustrating a wiring board according to one embodiment of the present disclosure. This is an enlarged explanatory diagram illustrating the differential conductor in region X shown in Figure 1 (however, the core insulating layer, the first build-up insulating layer, and the second build-up insulating layer are omitted). This is an enlarged explanatory diagram illustrating the positional relationship between the paired wiring and the first land. This is an explanatory diagram showing the position of the first wiring. This is an enlarged explanatory diagram illustrating one embodiment of region Y shown in Figure 3 (however, the core insulating layer and the first build-up insulating layer are omitted, and only the essential parts are shown). This is an explanatory diagram illustrating the first and second openings surrounding the differential conductor. This is an enlarged explanatory diagram illustrating the positional relationship between the first pad and the second pad.

[0007] When transmitting signals between pads for connecting electronic components and pads for external connections, these pads may be connected by a pair of strip-shaped wiring (differential conductors), and signals may be transmitted through these differential conductors. When signals are transmitted through differential conductors, reflection loss or insertion loss becomes large for high-frequency signals. Therefore, high-frequency signals are not transmitted efficiently. Accordingly, this disclosure provides a wiring board that reduces reflection loss and insertion loss even for high-frequency signals, and transmits signals efficiently regardless of frequency.

[0008] A wiring board according to one embodiment of the present disclosure will be described with reference to Figures 1 to 7. Figure 1 is an enlarged explanatory diagram for illustrating a wiring board 10 according to one embodiment of the present disclosure. Specifically, Figure 1 shows the right half of a cross-sectional view of the wiring board 10. The wiring board 10 according to one embodiment includes a core layer 1, a first build-up layer 2, a second build-up layer 3, and a solder resist 4.

[0009] The core layer 1 includes a core insulating layer 11, a core conductor layer 12, and a through-hole conductor 13. The core insulating layer 11 is located approximately in the center of the thickness direction of the wiring board 10. The core insulating layer 11 is not particularly limited as long as it is made of an insulating material. Examples of insulating materials include resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin, as well as glass. Only one of these insulating materials may be used, or two or more may be used in combination.

[0010] The thickness of the core insulating layer 11 is not particularly limited and may be, for example, 400 μm or more and 1.2 mm or less.

[0011] The core insulating layer 11 may contain a reinforcing material. Examples of reinforcing materials include insulating fabrics such as glass fibers, glass nonwoven fabrics, aramid nonwoven fabrics, aramid fibers, and polyester fibers. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the core insulating layer 11 may contain dispersed inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0012] Core conductor layers 12 are located on both sides of the core insulating layer 11. The core conductor layer 12 is not particularly limited as long as it is made of a conductive material. Examples of conductive materials include metals such as copper. The thickness of the core conductor layer 12 is not limited and may be, for example, 15 μm or more and 25 μm or less. In Figure 1, the core conductor layer 12 is located on both sides of the core insulating layer 11, but it is sufficient if it is located on at least one side of the core insulating layer 11.

[0013] As shown in Figure 1, a through-hole conductor 13 is located in the core insulating layer 11 to electrically connect the upper and lower surfaces of the core insulating layer 11. The through-hole conductor 13 is located within a through-hole that penetrates from the upper surface to the lower surface of the core insulating layer 11. The through-hole conductor 13 is made of a metal such as copper.

[0014] The through-hole conductor 13 is connected to the core conductor layer 12 formed on both sides of the core insulating layer 11. The through-hole conductor 13 may be formed integrally with the core conductor layer 12. The through-hole conductor 13 may be located only on the inner wall surface of the through-hole, or it may be filled inside the through-hole. As shown in Figure 2, through-hole lands 121, which are part of the core conductor layer 12, may be located at both ends of the through-hole conductor 13. Figure 2 is an enlarged explanatory diagram for illustrating the differential conductor in region X shown in Figure 1.

[0015] As shown in Figure 1, the first build-up layer 2 is located on the first surface 1a of the core layer 1. The first surface 1a of the core layer 1 refers to the surface of the core conductor layer 12 in the portion where the core conductor layer 12 is located on the surface of the core insulating layer 11, and is an uneven surface. The first build-up layer 2 has a structure in which at least two first build-up insulating layers 21 and at least two first build-up conductor layers 22 are alternately stacked.

[0016] The first build-up insulating layer 21 is not particularly limited as long as it is made of an insulating material. Examples of insulating materials include epoxy resins, bismaleimide-triazine resins, polyimide resins, and polyphenylene ether resins. These resins may be used individually or in combination of two or more.

[0017] The first build-up insulating layers 21 may be made of the same resin or different resins. The first build-up insulating layers 21 and the core insulating layer 11 may be made of the same resin or different resins. The thickness of the first build-up insulating layers 21 is not particularly limited and may be, for example, 20 μm or more and 40 μm or less. The first build-up insulating layers 21 may have the same thickness or different thicknesses.

[0018] The first build-up insulating layer 21 may contain a reinforcing material. Examples of reinforcing materials include insulating fabrics such as glass fibers, glass nonwoven fabrics, aramid nonwoven fabrics, aramid fibers, and polyester fibers. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the first build-up insulating layer 21 may contain dispersed inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0019] A first build-up conductor layer 22 is located on the surface of the first build-up insulating layer 21. The first build-up conductor layer 22 is not particularly limited as long as it is made of a conductive material. Examples of conductive materials include metals such as copper. The thickness of the first build-up conductor layer 22 is not limited and may be, for example, 10 μm or more and 25 μm or less.

[0020] The first build-up conductor layers 22 may be made of the same metal or different metals. The first build-up conductor layers 22 and the core conductor layer 12 may be made of the same metal or different metals. The first build-up conductor layers 22 may have the same thickness or different thicknesses.

[0021] The first build-up insulating layer 21 has a first via-hole conductor 23 for electrically connecting the upper and lower surfaces of the first build-up insulating layer 21. The first via-hole conductor 23 is located within a via hole that penetrates from the upper surface to the lower surface of the first build-up insulating layer 21. The first via-hole conductor 23 is made of a metal such as copper. The first via-hole conductor 23 may be filled into the via hole or may be located only on the inner wall surface of the via hole. The first via-hole conductor 23 is part of the first build-up conductor layer 22.

[0022] As shown in Figure 1, the second build-up layer 3 is located on the second surface 1b of the core layer 1. The second surface 1b of the core layer 1 is the surface opposite to the first surface 1a of the core layer 1, and in the portion where the core conductor layer 12 is located on the surface of the core insulating layer 11, it refers to the surface of the core conductor layer 12 and is an uneven surface. The second build-up layer 3 has a structure in which at least two second build-up insulating layers 31 and at least two second build-up conductor layers 32 are alternately stacked.

[0023] The second build-up insulating layer 31 is not particularly limited as long as it is made of an insulating material. Examples of insulating materials include epoxy resins, bismaleimide-triazine resins, polyimide resins, and polyphenylene ether resins. These resins may be used individually or in combination of two or more.

[0024] The second build-up insulating layer 31 may be made of the same resin or different resins. The second build-up insulating layer 31 and the core insulating layer 11 may be made of the same resin or different resins. The second build-up insulating layer 31 and the first build-up insulating layer 21 may be made of the same resin or different resins. The thickness of the second build-up insulating layer 31 is not particularly limited and may be, for example, 20 μm or more and 40 μm or less. The second build-up insulating layer 31 may have the same thickness or different thicknesses. The second build-up insulating layer 31 may have the same thickness as the first build-up insulating layer 21 or different thicknesses.

[0025] The second build-up insulating layer 31 may contain a reinforcing material. Examples of reinforcing materials include insulating fabrics such as glass fibers, glass nonwoven fabrics, aramid nonwoven fabrics, aramid fibers, and polyester fibers. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the second build-up insulating layer 31 may contain dispersed inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0026] A second build-up conductor layer 32 is located on the surface of the second build-up insulating layer 31. The second build-up conductor layer 32 is not particularly limited as long as it is made of a conductive material. Examples of conductive materials include metals such as copper. The thickness of the second build-up conductor layer 32 is not limited and may be, for example, 10 μm or more and 25 μm or less.

[0027] The second build-up conductor layer 32 may be made of the same metal or different metals. The second build-up conductor layer 32 and the core conductor layer 12 may be made of the same metal or different metals. The second build-up conductor layer 32 and the first build-up conductor layer 22 may be made of the same metal or different metals. The second build-up conductor layer 32 may have the same thickness or different thicknesses. The second build-up conductor layer 32 may have the same thickness as the first build-up conductor layer 22 or different thicknesses.

[0028] The second build-up insulating layer 31 has a second via-hole conductor 33 for electrically connecting the upper and lower surfaces of the second build-up insulating layer 31. The second via-hole conductor 33 is located within a via hole that penetrates from the upper surface to the lower surface of the second build-up insulating layer 31. The second via-hole conductor 33 is made of a metal such as copper. The second via-hole conductor 33 may be filled into the via hole, or it may be located only on the inner wall surface of the via hole. The second via-hole conductor 33 is part of the second build-up conductor layer 32.

[0029] As shown in Figure 1, solder resist 4 may be located on the surfaces of the first build-up layer 2 and the second build-up layer 3. Solder resist 4 is made of resin, and examples of resin include acrylic-modified epoxy resin.

[0030] The first build-up layer 2 has a third surface 2c opposite to the first surface 1a of the core layer 1. At least two first pads 221 are located on the third surface 2c of the first build-up layer 2. The first pads 221 are part of the first build-up conductor layer 22 located on the outermost layer of the first build-up layer 2. Specifically, the first pads 221 are the first build-up conductor layer 22 exposed from an opening contained in the solder resist 4 located on the surface of the first build-up layer 2. The first pads 221 are located, for example, in the mounting area of ​​the wiring board 10.

[0031] The second build-up layer 3 has a fourth surface 3d opposite to the second surface 1b of the core layer 1. At least two second pads 321 are located on the fourth surface 3d of the second build-up layer 3. The second pads 321 are part of the second build-up conductive layer 32 located on the outermost surface of the second build-up layer 3. Specifically, the second pads 321 are the second build-up conductive layer 32 exposed from an opening contained in the solder resist 4 located on the surface of the second build-up layer 3.

[0032] The size (area) of the first pad 221 and the size (area) of the second pad 321 are not limited. For example, the sizes of the first pad 221 and the second pad 321 may be the same or different. For example, if the first pad 221 is smaller than the second pad 321, the first pad 221 may be a flip-chip attachment (FCA) and the second pad 321 may be a ball grid array (BGA).

[0033] A wiring board 10 according to one embodiment includes a differential conductor. The differential conductor is connected to any two first pads 221 and any two second pads 321. As shown in Figure 2, the differential conductor has a pair of paired wirings 22a located along each other and a first land 222 connected to each paired wiring 22a in the first build-up layer 2, and two through-hole conductors 13 located side by side in the core insulating layer 11.

[0034] The paired wiring 22a and the first land 222 are part of the first build-up conductor layer 22. The first land 222 is connected to the first via-hole conductor 23. To electrically connect the upper and lower surfaces of the first build-up insulating layer 21, the lands and the first via-hole conductor 23 are alternately connected toward the core layer 1. This structure ensures electrical connection in the thickness direction of the first build-up layer 2.

[0035] As shown in Figure 3, in a planar perspective view, if the first virtual line L1 is a virtual line passing through the centers of the two through-hole conductors 13, the paired wiring 22a is positioned along the first virtual line L1, flanking it. Figure 3 is an enlarged explanatory diagram illustrating the positional relationship between the paired wiring 22a and the first land 222. Furthermore, in a planar perspective view, if the second virtual line L2 is a virtual line passing through the centers of the first land 222 connected to each paired wiring 22a, then the second virtual line L2 is perpendicular to the first virtual line L1 between the centers of the two through-hole conductors 13. It is advantageous for the signal transmission efficiency to be improved if the first virtual line L1 and the second virtual line L2 are perpendicular to each other at the center between the two through-hole conductors 13. "Center" can be defined as the center of the circle in a planar view, for example, if the through-hole conductor 13 is cylindrical. "Perpendicular" means that the first virtual line L1 and the second virtual line L2 do not necessarily intersect at a 90-degree angle. In this specification, a first virtual line L1 and a second virtual line L2 are defined as "orthogonal" if they intersect at an angle of 90 degrees ± 5 degrees. With such a configuration, the wiring board 10 according to one embodiment reduces reflection loss and insertion loss even with high-frequency signals, and transmits signals efficiently regardless of frequency.

[0036] The paired wiring 22a is not limited as long as it is positioned along the first virtual line L1, flanking the first virtual line L1. For example, the paired wiring 22a may be positioned symmetrically with respect to the first virtual line L1 as the axis of symmetry in the portion where they are positioned flanking the first virtual line L1. Such a configuration reduces reflection loss and insertion loss, and allows for more efficient transmission of high-frequency signals.

[0037] The differential conductor may further have two first wirings 22b and a second land 223, as shown in Figures 2 and 4. Figure 4 is an explanatory diagram showing the location of the first wirings 22b. The two first wirings 22b are located on the first surface 1a side of the pair wirings 22a in the first build-up layer 2. The second land 223 overlaps with the through-hole conductor 13 in a planar perspective and is connected to the first wirings 22b. The first wirings 22b and the second land 223 are part of the first build-up conductor layer 22.

[0038] As shown in Figures 2 and 5, the first wiring 22b may be located in any first build-up conductor layer 22, as long as it is located on the first surface 1a side of the pair wiring 22a. Figure 5 is an enlarged explanatory diagram illustrating one embodiment of region Y shown in Figure 3. Figure 5 omits the core insulating layer 11 and the first build-up insulating layer 21, and only the essential parts are shown. When the first wiring 22b is located on the first surface 1a side of the pair wiring 22a, the change in impedance is reduced, and reflection loss and insertion loss are further reduced.

[0039] Regarding the statement "the second land 223 is located overlapping with the through-hole conductor 13 in a planar perspective view," it is not necessary for the second land 223 and the through-hole conductor 13 to completely overlap, specifically, for one to be completely encompassed within the range of the other. It is sufficient for the second land 223 and the through-hole conductor 13 to overlap at least partially.

[0040] The wiring width of the paired wiring 22a and the wiring width of the first wiring 22b are not limited. The paired wiring 22a may have a wiring width of, for example, 10 μm or more and 30 μm or less. The first wiring 22b may have a wiring width of, for example, 10 μm or more and 30 μm or less. The paired wiring 22a and the first wiring 22b may have the same wiring width. "Same wiring width" does not necessarily mean that the wiring widths are exactly the same. In this specification, as shown in Figure 4, for example, if the width of the paired wiring 22a is W (length in the direction perpendicular to the longitudinal direction of the paired wiring 22a), then the width of the first wiring 22b is defined as being in the range of 0.95 W or more and 1.05 W or less. When the paired wiring 22a and the first wiring 22b have the same wiring width, impedance mismatch is less likely to occur. Therefore, reflection loss and insertion loss are further reduced.

[0041] The first build-up layer 2 includes a first ground conductor 224, as shown in Figure 6. Figure 6 is an explanatory diagram illustrating the first and second openings 24 and 34 surrounding the differential conductor. The first ground conductor 224 is part of the first build-up conductor layer 22. The first ground conductor 224 has a first opening 24 surrounding the differential conductor in plan view.

[0042] The first opening 24 is not limited in shape as long as it can enclose the differential conductor. For example, as shown in Figure 6, the opening length of the first opening 24 may gradually increase from the third surface 2c to the first surface 1a in a cross-section in the thickness direction passing through the first virtual straight line L1. Having such a structure reduces impedance changes and further reduces reflection loss and insertion loss.

[0043] The second build-up layer 3 includes a second ground conductor 324, as shown in Figure 6. The second ground conductor 324 is part of the second build-up conductor layer 32. The second ground conductor 324 has a second opening 34 that surrounds the differential conductor in a plan view.

[0044] The second opening 34 is not limited as long as it can surround the differential conductor. For example, as shown in FIG. 6, the second opening 34 may have an opening length that gradually increases from the second surface 1b toward the fourth surface 3d in a cross section in the thickness direction passing through the first virtual straight line L1. By having such a structure, the change in impedance is reduced, and the reflection loss and insertion loss are further reduced.

[0045] In the wiring board 10 according to an embodiment, the through-hole conductor 13, the first pad 221, and the second pad 321 may be arbitrarily arranged. For example, the second pad 321 and the through-hole conductor 13 constituting the differential conductor may be positioned such that the center-to-center distance between adjacent second pads 321 is greater than the center-to-center distance of the through-hole conductors 13 constituting the differential conductor. By having such a configuration, it becomes easier to match the impedance and the transmission characteristics are improved.

[0046] As shown in FIG. 7, in the two first pads 221 and the two second pads 321 connected to the differential conductor, a virtual straight line passing through the center of the first pad 221 is defined as the third virtual straight line L3, and a virtual straight line passing through the center of the second pad 321 is defined as the fourth virtual straight line L4. The two first pads 221 and the two second pads 321 connected to the differential conductor may be positioned such that the third virtual straight line L3 is orthogonal to the fourth virtual straight line L4. "Orthogonal" means that the third virtual straight line L3 and the fourth virtual straight line L4 do not necessarily intersect at 90 degrees. In this specification, if the third virtual straight line L3 and the fourth virtual straight line L4 intersect at an angle of 90 degrees ± 5 degrees, it is defined as "orthogonal". Thus, when the arrangement directions of the first pad 221 and the second pad 321 are different from each other (orthogonal), the transmission characteristics are particularly improved by applying the differential conductor structure as disclosed herein.

[0047] In the wiring board 10 according to an embodiment, the method of forming the differential conductor is not limited. For example, at least one of plating and metal foil may be used to form a differential conductor having the above-described structure. Plating or exposure and development may be performed by known methods.

[0048] Next, the implementation structure according to the present disclosure will be described based on FIG. 1. The implementation structure according to one embodiment includes a wiring board 10 according to one embodiment and an electronic component 6 located in the mounting area of the wiring board 10.

[0049] In FIG. 1, a state where the wiring board 10 and the electronic component 6 are not connected is shown. The implementation structure according to the present disclosure can be obtained by connecting the first pad 221 (the first build-up conductor layer 22) exposed from the opening of the solder resist 4 located on the surface of the build-up layer and the electrode of the electronic component 6 via solder 5. Examples of the electronic component 6 include a semiconductor integrated circuit element and an optoelectronic element. In the implementation structure according to one embodiment, the electronic component 6 may also be connected to the second pad 321 (the second build-up conductor layer 32) of the wiring board 10 via solder 5. Alternatively, for example, a motherboard or the like may be connected to the second pad 321 of the wiring board 10 via solder 5.

[0050] As described above, the embodiments of the present disclosure have been described. However, the invention according to the present disclosure is not limited to the above-described embodiments, and various changes and improvements can be made within the scope of the present disclosure shown in the following (1) to (9).

[0051] (1) The wiring board according to the present disclosure includes a core layer having a first face and a second face on the opposite side of the first face, a first build-up layer located on the first face and having a third face on the opposite side of the first face, a second build-up layer located on the second face and having a fourth face on the opposite side of the second face, at least two first pads located on the third face and at least two second pads located on the fourth face, and differential conductors connected to two of the at least two first pads and two of the at least two second pads. The differential conductor has, on the first build-up layer, a pair of paired wirings located along each other and a first land connected to each paired wiring, and on the core insulating layer, two through-hole conductors located side by side. If, in a planar perspective, a virtual line passing through the centers of the two through-hole conductors is defined as the first virtual line, the paired wirings are located along the first virtual line, with the first virtual line in between. (1) In a planar perspective view, if a second virtual line is defined as a virtual line passing through the center of each first land connected to a pair of wirings, then the second virtual line is perpendicular to the first virtual line between the centers of the two through-hole conductors. (2) In the wiring board described in (1) above, the differential conductor has two first wirings and second lands located on the first surface side of the pair of wirings in the first build-up layer, overlapping with the through-hole conductors in a planar perspective view and connected to each of the first wirings. (3) In the wiring board described in (2) above, the first wirings have the same wiring width as the pair of wirings. (4) In the wiring board described in any of (1) to (3) above, the pair of wirings are positioned symmetrically with respect to the first virtual line as the axis of symmetry in the portions located on either side of the first virtual line. (5) In the wiring board described in any of (1) to (4) above, the first build-up layer includes a first ground conductor having a first opening that surrounds the differential conductor in a planar view. In a cross-section in the thickness direction passing through a first imaginary line, the opening length of the first opening gradually increases from the third surface toward the first surface. (6) In the wiring board described in any of (1) to (5) above, the second build-up layer includes a second ground conductor having a second opening that surrounds the differential conductor in a plan view. In a cross-section in the thickness direction passing through a first imaginary line, the opening length of the second opening gradually increases from the second surface toward the fourth surface.(7) In the wiring board described in any of (1) to (6) above, in a plan view, the distance between the centers of the second pads is greater than the distance between the centers of the through-hole conductors constituting the differential conductor. (8) In the wiring board described in any of (1) to (7) above, if a virtual line passing through the center of the first pad is defined as the third virtual line and a virtual line passing through the center of the second pad is defined as the fourth virtual line, then the third virtual line is perpendicular to the fourth virtual line. (9) The mounting structure according to the present disclosure includes the wiring board described in any of (1) to (8) above and electronic components mounted on the wiring board.

[0052] The wiring board and mounting structure according to this disclosure, having the above-described configuration, reduces reflection loss and insertion loss even for high-frequency signals, and enables efficient signal transmission regardless of frequency.

[0053] This disclosure can be used as a wiring board and mounting structure.

[0054] 1 Core layer 11 Core insulating layer 12 Core conductor layer 121 Through-hole land 13 Through-hole conductor 1a First side 1b Second side 2 First build-up layer 21 First build-up insulating layer 22 First build-up conductor layer 221 First pad 222 First land 223 Second land 224 First ground conductor 22a Pair wiring 22b First wiring 23 First via hole conductor 24 First opening 2c Third side 3 Second build-up layer 31 Second build-up insulating layer 32 Second build-up conductor layer 321 Second pad 324 Second ground conductor 33 Second via hole conductor 34 Second opening 3d Fourth side 4 Solder resist 5 Solder 6 Electronic components 10 Wiring board L1 First virtual line L2 Second virtual line L3 Third virtual line L4 Fourth virtual line

Claims

1. A core layer having a first surface and a second surface on the opposite side of the first surface; a first build-up layer located on the first surface and having a third surface on the opposite side of the first surface; a second build-up layer located on the second surface and having a fourth surface on the opposite side of the second surface; at least two first pads located on the third surface and at least two second pads located on the fourth surface; a differential conductor connected to two of the at least two first pads and two of the at least two second pads, wherein the differential conductor has, on the first build-up layer, a pair of paired wirings located along each other and a first land connected to each of the paired wirings; and on the core layer, two through-hole conductors located side by side, and in a planar perspective, if a virtual line passing through the centers of the two through-hole conductors is defined as a first virtual line, the paired wirings are located along the first virtual line, flanking the first virtual line. In a planar perspective view, if a second virtual line is defined as a virtual line passing through the center of the first land connected to each of the paired wirings, the wiring board is such that the second virtual line is perpendicular to the first virtual line between the centers of the two through-hole conductors.

2. The wiring board according to claim 1, wherein the differential conductor is located on the first surface side of the pair wiring in the first build-up layer, and has two first wirings and second lands that overlap with the through-hole conductors in a planar view and connect to each of the first wirings.

3. The wiring board according to claim 2, wherein the first wiring has the same wiring width as the paired wiring.

4. The wiring board according to any one of claims 1 to 3, wherein the paired wirings are positioned symmetrically with respect to the first virtual line in the portions that straddle the first virtual line.

5. The wiring board according to any one of claims 1 to 4, wherein the first build-up layer includes a first ground conductor having a first opening that surrounds the differential conductor in a plan view, and in a cross section in the thickness direction passing through the first virtual line, the opening length of the first opening gradually increases from the third surface toward the first surface.

6. The wiring board according to any one of claims 1 to 5, wherein the second build-up layer includes a second ground conductor having a second opening that surrounds the differential conductor in a plan view, and in a cross-section in the thickness direction passing through the first virtual straight line, the opening length of the second opening gradually increases from the second surface toward the fourth surface.

7. The wiring board according to any one of claims 1 to 6, wherein, in a plan view, the distance between the centers of the second pads is greater than the distance between the centers of the through-hole conductors constituting the differential conductor.

8. The wiring board according to any one of claims 1 to 7, wherein, when a virtual line passing through the center of the first pad is defined as the third virtual line, and a virtual line passing through the center of the second pad is defined as the fourth virtual line, the third virtual line is perpendicular to the fourth virtual line.

9. A mounting structure comprising a wiring board according to any one of claims 1 to 8 and an electronic component mounted on the wiring board.

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