Wiring board

Abstract

This invention involves a first insulating layer (21) having a first surface (211) and a second surface (212) positioned on the opposite side from the first surface, a through-hole (20) penetrating the first insulating layer from the first surface to the second surface, a through-hole conductor (2a) positioned on the inner wall surface of the through-hole, a first wiring conductor (31) positioned on the first surface and electrically connected to the through-hole conductor, and a second wiring conductor (32) positioned on the second surface and electrically connected to the through-hole conductor. The through-hole conductor includes a first portion (2a1) positioned over the entire circumference of the inner wall surface, and a second portion (2a2) connecting the first portion and the first wiring conductor. The first portion has a first end portion located on the first surface side and a second end portion located on the second surface side in the thickness direction of the first insulating layer. The first end portion is located closer to the second surface side than the first surface in the thickness direction. The second portion is connected to a first region constituting part of the first end portion, and is positioned from the first region to the first surface in the thickness direction.

Description

wiring board

[0001] The present invention relates to a wiring board.

[0002] In order to electrically connect the upper and lower surfaces of the wiring board, at least one through-hole is formed in the core insulating layer of the wiring board, as described in Patent Document 1. A through-hole conductor is located inside the through-hole, and electrically connects the upper and lower surfaces of the wiring board via the through-hole conductor. As described in Patent Document 1, the through-hole conductor and a wiring conductor (e.g., a signal wiring conductor) are usually connected via a land on the surface of the core insulating layer.

[0003] Japanese Unexamined Patent Publication No. 58-23493

[0004] The wiring board according to the present disclosure includes a first insulating layer having a first surface and a second surface opposite the first surface, a through hole penetrating the first insulating layer from the first surface to the second surface, a through-hole conductor located on the inner wall surface of the through-hole, a first wiring conductor located on the first surface and electrically connected to the through-hole conductor, and a second wiring conductor located on the second surface and electrically connected to the through-hole conductor. The through-hole conductor includes a first portion located along the entire periphery of the inner wall surface and a second portion connecting the first portion and the first wiring conductor. The first portion has a first end located on the first surface side in the thickness direction of the first insulating layer and a second end located on the second surface side. At least the first end is located closer to the second surface than the first surface in the thickness direction. The second portion is connected to a first region that is a part of the first end and is located from the first region to the first surface in the thickness direction.

[0005] 2A is an explanatory diagram illustrating a wiring board according to an embodiment of the present disclosure. FIG. 2A is an enlarged explanatory diagram illustrating region X shown in FIG. 1, FIG. 2B is a perspective view illustrating an embodiment of a through-hole conductor, and FIG. 2C is a plan view of region A shown in FIG. 2A as viewed from the direction of arrow A. FIGS. 3A to 3H are explanatory diagrams illustrating an embodiment of a method for forming a through-hole conductor located in region X shown in FIG. 1. FIGS. 4A to 4D are explanatory diagrams illustrating an embodiment of a method for forming a through-hole conductor located in region Y shown in FIG. 1. Data showing simulation results of electrical characteristics for a wiring board according to an embodiment of the present disclosure. Data showing simulation results of electrical characteristics for a conventional wiring board. Data showing simulation results of electrical characteristics for a conventional wiring board.

[0006] As described in Patent Document 1, the land is positioned to surround the opening of the through hole. Therefore, the current (signal) flowing through the wiring conductor located on the surface of the core insulating layer branches to the left and right at the land. As a result, the branched signals collide when they converge, disrupting the signal flow and causing the signal to accumulate at the land, resulting in a localized increase in potential. When a signal accumulates at the land and the localized increase in potential occurs, subsequent signals are reflected, reducing signal transmittance. This reduction in signal transmittance is likely to occur in plated through holes (PTHs) located only on the inner wall surface of the through hole. Therefore, there is a demand for a wiring board that reduces signal reflection at plated through holes and improves signal transmittance.

[0007] The wiring board according to the present disclosure has a configuration as described in the section on means for solving the above problems, thereby reducing signal reflection at plated through holes and improving signal transmittance.

[0008] A wiring board according to an embodiment of the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is an explanatory diagram for describing a wiring board 1 according to an embodiment of the present disclosure. As shown in Figure 1, the wiring board 1 according to the embodiment includes an insulating layer 2, a conductor layer 3, and a solder resist 4.

[0009] In the wiring board 1, the insulating layer 2 includes a first insulating layer 21, a second insulating layer 22, and a third insulating layer 23. The first insulating layer 21 has a first surface 211 and a second surface 212 located on the opposite side of the first surface 211. The first insulating layer 21 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. These resins may be used alone or in combination of two or more.

[0010] In the wiring substrate 1, the first insulating layer 21 corresponds to a core insulating layer. There are no particular limitations on the thickness of the first insulating layer 21. When the first insulating layer 21 corresponds to a core insulating layer, the first insulating layer 21 may have a thickness of, for example, 10 μm or more and 1500 μm or less.

[0011] The first insulating layer 21 may contain a reinforcing material. Examples of reinforcing materials include insulating fabric materials such as glass fiber, glass nonwoven fabric, aramid nonwoven fabric, aramid fiber, and polyester fiber. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the first insulating layer 21 may have dispersed therein an inorganic insulating filler such as silica, barium sulfate, talc, clay, glass, calcium carbonate, or titanium oxide. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0012] Build-up layers, in which conductor layers 3 and insulating layers 2 are alternately stacked, are located on the first surface 211 and the second surface 212 of the first insulating layer 21. Each build-up layer has at least two conductor layers 3 and at least one insulating layer 2. Of the insulating layers 2 constituting the build-up layers, the insulating layer 2 in contact with the first surface 211 corresponds to the second insulating layer 22, and the insulating layer 2 in contact with the second surface 212 corresponds to the third insulating layer 23.

[0013] The insulating layer 2 constituting the build-up layer 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. These resins may be used alone or in combination of two or more.

[0014] The insulating layers 2 constituting the build-up layer may be made of the same resin or different resins. The insulating layers 2 constituting the build-up layer and the first insulating layer 21 may be made of the same resin or different resins.

[0015] The thickness of the insulating layer 2 constituting the build-up layer is not particularly limited. The insulating layer 2 constituting the build-up layer may have a thickness of, for example, 5 μm or more and 100 μm or less. The insulating layers 2 constituting the build-up layer may have the same thickness or different thicknesses.

[0016] The insulating layer 2 constituting the build-up layer may contain a reinforcing material. Examples of reinforcing materials include insulating fabric materials such as glass fiber, glass nonwoven fabric, aramid nonwoven fabric, aramid fiber, and polyester fiber. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the insulating layer 2 constituting the build-up layer may have dispersed therein an inorganic insulating filler 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.

[0017] The conductor layer 3 is not limited to a specific material as long as it is a conductor such as a metal. The conductor layer 3 is formed of, for example, a metal such as copper. The thickness of the conductor layer 3 is not particularly limited and is, for example, 1 μm or more and 70 μm or less. The "first wiring conductor 31" included in the conductor layer 3 is located on the first surface 211 of the first insulating layer 21 and is electrically connected to the through-hole conductor 2a described below. The "second wiring conductor 32" included in the conductor layer 3 is located on the second surface 212 of the first insulating layer 21 and is electrically connected to the through-hole conductor 2a described below. The conductor layer 3 includes a power supply conductor, a ground conductor, and a signal conductor. For example, the first wiring conductor 31 may be a "first signal wiring conductor," and the second wiring conductor 32 may be a "second signal wiring conductor."

[0018] Via-hole conductors 3a are located in the insulating layer 2 constituting the build-up layer, for electrically connecting the upper and lower surfaces of the insulating layer 2. The via-hole conductors 3a are located in via holes formed to penetrate the insulating layer 2. The via-hole conductors 3a are part of the conductor layer 3, and are made of a metal such as copper.

[0019] 1, a solder resist 4 may be positioned on the surface of the build-up layer. The solder resist 4 is made of a resin, such as an acrylic-modified epoxy resin. The solder resist 4 has openings for electrically connecting the conductor layer 3 to the electrodes of the element via solder 5. Examples of the element include a semiconductor integrated circuit element and an optoelectronic element.

[0020] A through-hole conductor 2a is located in the first insulating layer 21 to electrically connect the upper and lower surfaces of the first insulating layer 21. The through-hole conductor 2a is located in a through-hole 20 that penetrates from the upper surface to the lower surface of the first insulating layer 21. The through-hole conductor 2a is formed of a metal such as copper.

[0021] As shown in Fig. 2A, the through-hole conductor 2a is electrically connected to a first wiring conductor 31 located on a first surface 211 of the first insulating layer 21 and a second wiring conductor 32 located on a second surface 212 of the first insulating layer 21. Fig. 2A is an enlarged explanatory view for explaining region X shown in Fig. 1. The through-hole conductor 2a is located only on the inner wall surface of the through-hole 20.

[0022] In addition to the through-hole conductor 2a, resin 2b is located in the through-hole 20. The resin 2b is located so as to be surrounded by the through-hole conductor 2a. The resin 2b is a filling resin that fills the space surrounded by the through-hole conductor 2a. There are no limitations on the resin 2b, and examples include epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin. Two or more of these resins may be mixed together.

[0023] In wiring board 1, through-hole conductor 2a includes first portion 2a1, second portion 2a2, and third portion 2a3. The thickness of through-hole conductor 2a is set appropriately depending on the diameter of through-hole 20. For example, the thickness of through-hole conductor 2a may be approximately 1% to 30% of the radius of through-hole 20.

[0024] As shown in Fig. 2B, first portion 2a1 of through-hole conductor 2a has a first end portion 2a11 located on the first surface 211 side and a second end portion 2a12 located on the second surface 212 side in the thickness direction of first insulating layer 21. Fig. 2B is a perspective view showing one embodiment of through-hole conductor 2a. As shown in Fig. 2C, first portion 2a1 of through-hole conductor 2a is located around the entire inner wall surface of through hole 20. Fig. 2C is a plan view of region A shown in Fig. 2A as viewed from the direction of arrow A.

[0025] 2A and 2B , of first end 2a11 and second end 2a12, at least first end 2a11 is located closer to second surface 212 than first surface 211 in the thickness direction of first insulating layer 21. In other words, at least first end 2a11 is not flush with first surface 211 but is recessed from first surface 211.

[0026] 2A and 2B, second portion 2a2 of through-hole conductor 2a is connected to a first region that is a part of first end 2a11 of first portion 2a1. That is, unlike first portion 2a1, second portion 2a2 is not located along the entire inner wall surface of through-hole 20, as shown in FIG. 2B. Second portion 2a2 is located from the first region to first surface 211 in the thickness direction of first insulating layer 21.

[0027] As shown in FIG. 2A , the second portion 2a2 is in contact with the first wiring conductor 31. Specifically, the first wiring conductor 31 is in contact with the end of the second portion 2a2 opposite the first portion 2a1. Because the second portion 2a2 is not positioned along the entire inner wall surface of the through-hole 20, the current (signal) flowing through the first wiring conductor 31 does not branch to the left and right at the through-hole conductor 2a. This prevents the branched signals from merging, causing the flow to become turbulent and stagnate, as in the conventional case. As a result, reflection of the subsequent signal is reduced, and the signal transmittance is improved.

[0028] The length L1 of the second portion 2a2 is not limited. For example, when viewed from above, the direction in which the first wiring conductor 31 extends from the second portion 2a2 is defined as a first direction (D1 in FIG. 2C ), and the direction perpendicular to the first direction D1 is defined as a second direction (D2 in FIG. 2C ), the length L2 of the first wiring conductor 31 in the second direction D2 may be the same as the length L1 of the second portion 2a2. "The length L2 of the first wiring conductor 31 and the length L1 of the second portion 2a2 being the same" is defined not only as being completely the same, but also as being the same within a range of about ±10%. In other words, when the length L1 is 1, the length L1 and the length L2 are defined as being the same if the length L2 is 0.9 to 1.1.

[0029] If the length L2 of the first wiring conductor 31 and the length L1 of the second portion 2a2 are the same, the change in impedance is reduced. As a result, the transmission efficiency of the current (signal) flowing through the first wiring conductor 31 is further improved. The first wiring conductor 31 may be a first signal wiring conductor. In FIG. 2B , one second portion 2a2 is located at the first end portion 2a11. A plurality of second portions 2a2 may be located at the first end portion 2a11. A plurality of first wiring conductors 31 may also be located depending on the number of second portions 2a2.

[0030] As shown in FIG. 2A , a first recess 2b1 is located in the through hole 20, with the first end 2a11 as its bottom. Specifically, the first recess 2b1 is a recess whose wall surfaces are the resin 2b and the first insulating layer 21, and whose bottom is a region other than the first region of the first end 2a11. The shape of the bottom may be, for example, a C-shape in which a portion of a ring is cut off in a plan view. A portion of the second insulating layer 22 is located in the first recess 2b1. This structure reduces peeling of the second insulating layer 22.

[0031] In the wiring board 1 according to one embodiment, the through-hole conductor 2a includes a third portion 2a3. As shown in FIG. 2A , the third portion 2a3 is connected to a second region that is a part of the second end 2a12 of the first portion 2a1. That is, unlike the first portion 2a1, the third portion 2a3 is not located along the entire inner wall surface of the through-hole 20. The third portion 2a3 is located from the second region to the second surface 212 in the thickness direction of the first insulating layer 21.

[0032] 2A , the third portion 2a3 is in contact with the second wiring conductor 32. Specifically, the second wiring conductor 32 is in contact with the end of the third portion 2a3 opposite the first portion 2a1. Because the third portion 2a3 is not located along the entire periphery of the inner wall surface of the through-hole 20, the current (signal) flowing through the second wiring conductor 32 does not branch to the left and right at the through-hole conductor 2a. Therefore, the signal transmittance is improved compared to when the third portion 2a3 is not located.

[0033] The length of the third portion 2a3 is not limited. For example, when the direction in which the second wiring conductor 32 extends from the third portion 2a3 in a top view is defined as a third direction (the same direction as the first direction D1) and the direction perpendicular to the third direction is defined as a fourth direction (the same direction as the second direction D2), the length of the second wiring conductor 32 in the fourth direction may be the same as the length of the third portion 2a3. The definition of "same length" is as described above, and a detailed description thereof will be omitted.

[0034] If the length of the second wiring conductor 32 is the same as the length of the third portion 2a3, the change in impedance is reduced. As a result, the transmission efficiency of the current (signal) flowing through the second wiring conductor 32 is further improved. The second wiring conductor 32 may be a second signal wiring conductor. One or more third portions 2a3 may be located at the second end 2a12. Depending on the number of third portions 2a3, more than one second wiring conductor 32 may also be located.

[0035] A second recess 2b2 is located in the through hole 20, with the second end 2a12 as its bottom. Specifically, the second recess 2b2 is a recess whose wall surfaces are the resin 2b and the third insulating layer 23, and whose bottom is a region other than the second region of the second end 2a12. The shape of the bottom may be, for example, a C-shape in plan view, with a portion of a ring severed. A portion of the third insulating layer 23 is located in the second recess 2b2. This structure reduces peeling of the third insulating layer 23.

[0036] Next, one embodiment of a method for forming the through-hole conductor 2a will be described with reference to Figures 3A to 3H, which are explanatory diagrams for explaining one embodiment of a method for forming the through-hole conductor 2a located in region X shown in Figure 1.

[0037] First, as shown in Fig. 3A, through holes 20 are formed so as to penetrate the top and bottom surfaces of the first insulating layer 21. The size and number of the through holes 20 are set appropriately depending on the size of the wiring board 1 to be finally obtained, etc. The through holes 20 are formed using, for example, a drill, a laser, or a blast. If necessary, a desmear process or the like is performed to remove resin residue and the like.

[0038] 3B, conductors 30 are formed on the upper and lower surfaces of first insulating layer 21 and on the inner wall surfaces of through holes 20. Conductors 30 are formed by depositing a metal such as copper by plating such as electrolytic plating.

[0039] When the conductor 30 is formed by electrolytic plating, a seed layer may be formed on the upper and lower surfaces of the first insulating layer 21 and on the inner wall surfaces of the formed through-holes 20 before the electrolytic plating. The formation of the seed layer allows metal to be efficiently deposited by electrolytic plating. The seed layer is formed of a metal such as copper by, for example, electroless plating.

[0040] 3C, the resin 2b is filled into the through holes 20. The resin 2b is as described above, and a detailed description thereof will be omitted.

[0041] Next, as shown in Figures 3D and 3E, a resist 6 is formed to remove unnecessary portions of the formed conductor 30. Figure 3E is a plan view of region B shown in Figure 3D as viewed from the direction of arrow B. The resist 6 may be, for example, a dry film resist. The conductor 30 covered with the resist 6 is protected. The resist 6 may be formed to cover not only the conductor 30 to be protected but also part of the resin 2b. By forming the resist 6 to cover part of the resin 2b, the conductor 30 to be protected is less likely to be eroded during the etching process described below.

[0042] 3F, the conductor 30 not covered with the resist 6 is removed by etching. Not only the conductor 30 formed on the upper and lower surfaces of the first insulating layer 21 but also a portion of the conductor 30 formed on the inner wall surface of the through hole 20 is removed. The removed portions correspond to the first recess 2b1 and the second recess 2b2.

[0043] Next, as shown in Fig. 3G, the resist 6 is removed. After the resist 6 is removed, as shown in Fig. 3H, a second insulating layer 22 is formed on the first surface 211 of the first insulating layer 21 so as to cover the first wiring conductor 31. A third insulating layer 23 is formed on the second surface 212 of the first insulating layer 21 so as to cover the second wiring conductor 32. A portion of the second insulating layer 22 is located in the first recess 2b1, and a portion of the third insulating layer 23 is located in the second recess 2b2.

[0044] Next, another embodiment of a method for forming the through-hole conductors 2a will be described with reference to Figures 4A to 4D. Figures 4A to 4D are explanatory diagrams for explaining one embodiment of a method for forming the through-hole conductors 2a located in region Y shown in Figure 1. The through-hole conductors 2a located in region X are formed of a first portion 2a1, a second portion 2a2, and a third portion 2a3. On the other hand, the through-hole conductors 2a located in region Y are formed of the first portion 2a1 and the second portion 2a2, but do not include the third portion 2a3. As such, in the wiring board 1 according to one embodiment, the through-hole conductors 2a do not need to be formed of the first portion 2a1, the second portion 2a2, and the third portion 2a3, but only need to be formed of the first portion 2a1 and the second portion 2a2.

[0045] 3A to 3C, the through-hole conductor 2a formed of the first portion 2a1 and the second portion 2a2 is as shown up to the step of filling the through-hole 20 with the resin 2b, and a detailed description thereof will be omitted. After the step shown in FIG. 3C, a resist 6 is formed to remove unnecessary portions of the formed conductor 30, as shown in FIG. 4A. Unlike FIG. 3D, in FIG. 4A, the resist 6 is formed to prevent the third portion 2a3 from being formed, i.e., to form a land at one end of the through-hole 20.

[0046] Next, as shown in FIG. 4B , the conductor 30 not covered with the resist 6 is removed by etching. Not only the conductor 30 formed on the top and bottom surfaces of the first insulating layer 21, but also a portion of the conductor 30 formed on the inner wall surface of the through hole 20 is removed. The removed portion corresponds to the first recess 2b1. In other words, the second recess 2b2 shown in FIG. 3F is not formed in FIG. 4B .

[0047] Next, as shown in Fig. 4C , the resist 6 is removed. After the resist 6 is removed, as shown in Fig. 4D , a second insulating layer 22 is formed on the first surface 211 of the first insulating layer 21 so as to cover the first wiring conductor 31. A third insulating layer 23 is formed on the second surface 212 of the first insulating layer 21 so as to cover the second wiring conductor 32. A portion of the second insulating layer 22 is located in the first recess 2b1.

[0048] In this manner, the through-hole conductors 2a are formed in the wiring board 1. Next, the electrical characteristics of the wiring board 1 according to one embodiment were verified. Fig. 5 shows data showing the results of a simulation of the electrical characteristics of the wiring board 1 according to one embodiment of the present disclosure.

[0049] The simulation model used a first insulating layer 21 (corresponding to the core insulating layer, 6 mm square, 800 μm thick) made of epoxy resin, with a 25 μm thick copper layer provided on this first insulating layer 21 (core insulating layer) as the conductor layer 3. The diameter of the through-hole 20 was 120 μm, and the length L1 of the second portion 2a2 of the through-hole conductor 2a and the length L2 of the conductor layer 3 (first wiring conductor 31) connected to the second portion 2a2 were both 44 μm.

[0050] Insertion loss is a measurement of a signal that passes through an output terminal when a signal is input to an input terminal. The larger the dB value, the better the electrical characteristics, and typically a value of -5 dB or more is required at 140 GHz. Reflection loss is a measurement of a signal that is reflected back at the input terminal when a signal is input to the input terminal. The smaller the dB value, the better the electrical characteristics, and typically a value of -15 dB or less is required at 140 GHz. As shown in FIG. 5, for wiring board 1 according to one embodiment, the insertion loss at 140 GHz is -5 dB or more, and the reflection loss is -15 dB or less.

[0051] On the other hand, the electrical characteristics of a conventional wiring board in which the through-hole conductor does not have a specific structure like through-hole conductor 2a and the end of the through-hole conductor contacts the through-hole land were examined. Figures 6 and 7 show data showing the simulation results of the electrical characteristics of the conventional wiring board, along with the simulation results shown in Figure 5 (measured values ​​after applying the present invention). Figure 6 shows data showing the insertion loss, which indicates that the conventional wiring board is less than -5 dB at 140 GHz, failing to meet the required value. Figure 7 shows data showing the return loss, which indicates that the conventional wiring board is greater than -15 dB at 140 GHz, failing to meet the required value.

[0052] On the other hand, the wiring board 1 according to an embodiment of the present invention, as shown in FIG. 6, has a measured insertion loss of -5 dB or more at 140 GHz, which satisfies the required value. Furthermore, as shown in FIG. 7, the measured return loss at 140 GHz is -15 dB or less, which satisfies the required value. As described above, the wiring board 1 according to an embodiment satisfies the required values ​​for both insertion loss and return loss at 140 GHz, and has improved insertion loss and return loss compared to conventional wiring boards. Therefore, it can be seen that the wiring board according to the present disclosure has excellent electrical properties.

[0053] The embodiments of the present disclosure have been described above. However, the invention according to the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the present disclosure as shown in (1) below.

[0054] (1) A wiring board according to the present disclosure includes a first insulating layer having a first surface and a second surface opposite the first surface, a through hole penetrating the first insulating layer from the first surface to the second surface, a through-hole conductor located on the inner wall surface of the through-hole, a first wiring conductor located on the first surface and electrically connected to the through-hole conductor, and a second wiring conductor located on the second surface and electrically connected to the through-hole conductor. The through-hole conductor includes a first portion located along the entire periphery of the inner wall surface and a second portion connecting the first portion and the first wiring conductor. The first portion has a first end located on the first surface side in the thickness direction of the first insulating layer and a second end located on the second surface side. At least the first end is located closer to the second surface than the first surface in the thickness direction. The second portion is connected to a first region that is a part of the first end and is located from the first region to the first surface in the thickness direction.

[0055] The present disclosure further discloses the following embodiments (2) to (8).

[0056] (2) In the wiring board described in (1) above, a resin is further positioned in the through hole so as to be surrounded by the through-hole conductor. (3) In the wiring board described in (1) or (2) above, a second insulating layer is further positioned on the first surface and a third insulating layer is further positioned on the second surface. (4) In the wiring board described in any of (1) to (3) above, the through-hole conductor further includes a third portion connecting the first portion and the second wiring conductor. The second end portion is positioned closer to the first surface than the second surface in the thickness direction. The third portion connects to a second region of a part of the second end portion and is positioned from the second region to the second surface in the thickness direction. (5) In the wiring board described in (4) above, the first wiring conductor includes a first signal wiring conductor positioned on the first surface. The second wiring conductor includes a second signal wiring conductor positioned on the second surface. The first signal wiring conductor is connected to the second portion, and the second signal wiring conductor is connected to the third portion. (6) In the wiring board described in (5) above, when viewed from above, the direction in which the first signal wiring conductor extends from the second portion is defined as a first direction and the direction perpendicular to the first direction is defined as a second direction, the length of the first signal wiring conductor in the second direction is the same as the length of the second portion. When the direction in which the second signal wiring conductor extends from the third portion is defined as a third direction and the direction perpendicular to the third direction is defined as a fourth direction, the length of the second signal wiring conductor in the fourth direction is the same as the length of the third portion. (7) In the wiring board described in any of (3) to (6) above, a part of the second insulating layer is located in a first recess having walls formed by the resin and the first insulating layer and a bottom formed by a region other than the first region of the first end. (8) In the wiring board described in any of (3) to (7) above, a part of the third insulating layer is located in a second recess having walls formed by the resin and the first insulating layer and a bottom formed by a region other than the second region of the second end.

[0057] REFERENCE SIGNS LIST 1 wiring board 2 insulating layer 20 through hole 2a through hole conductor 21 first insulating layer 211 first surface 212 second surface 2a1 first portion 2a2 second portion 2a3 third portion 2a11 first end 2a12 second end 2b resin 2b1 first recess 2b2 second recess 22 second insulating layer 23 third insulating layer 3 conductor layer 30 conductor 3a via hole conductor 31 first wiring conductor 32 second wiring conductor 4 solder resist 5 solder 6 resist

Claims

1. A wiring board comprising: a first insulating layer having a first surface and a second surface located opposite the first surface; a through hole penetrating the first insulating layer from the first surface to the second surface; a through hole conductor located on an inner wall surface of the through hole; a first wiring conductor located on the first surface and electrically connected to the through hole conductor; and a second wiring conductor located on the second surface and electrically connected to the through hole conductor, wherein the through hole conductor includes a first portion located around the entire inner wall surface and a second portion connecting the first portion and the first wiring conductor, wherein the first portion has a first end portion located on the first surface side and a second end portion located on the second surface side in a thickness direction of the first insulating layer, at least the first end portion being located closer to the second surface than the first surface in the thickness direction, and the second portion being connected to a first region of a part of the first end portion and being located from the first region to the first surface in the thickness direction.

2. The wiring board according to claim 1, further comprising a resin positioned in said through hole so as to be surrounded by said through hole conductor.

3. The wiring board according to claim 1 or 2, further comprising a second insulating layer on said first surface and a third insulating layer on said second surface.

4. A wiring board as described in any one of claims 1 to 3, wherein the through-hole conductor further includes a third portion connecting the first portion and the second wiring conductor, the second end portion is located closer to the first surface than the second surface in the thickness direction, and the third portion is connected to a second region of a part of the second end portion and is located from the second region to the second surface in the thickness direction.

5. The wiring board according to claim 4, wherein the first wiring conductor includes a first signal wiring conductor located on the first surface, the second wiring conductor includes a second signal wiring conductor located on the second surface, the first signal wiring conductor and the second portion are connected, and the second signal wiring conductor and the third portion are connected.

6. The wiring board according to claim 5, wherein, in a top view, a direction in which the first signal wiring conductor extends from the second portion is defined as a first direction and a direction perpendicular to the first direction is defined as a second direction, and a length of the first signal wiring conductor in the second direction is the same as a length of the second portion; and, in a top view, a direction in which the second signal wiring conductor extends from the third portion is defined as a third direction and a direction perpendicular to the third direction is defined as a fourth direction, and a length of the second signal wiring conductor in the fourth direction is the same as a length of the third portion.

7. A wiring board according to any one of claims 3 to 6, wherein a portion of the second insulating layer is located in a first recess having wall surfaces of the resin and the first insulating layer and a bottom surface of an area other than the first area of ​​the first end.

8. A wiring board according to any one of claims 3 to 7, wherein a portion of the third insulating layer is located in a second recess having wall surfaces of the resin and the first insulating layer and a bottom surface of an area other than the second area of ​​the second end.

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