Wiring board

Abstract

To provide a wiring board that improves connection reliability between via wiring and a pad in a post-wall waveguide built-in in the wiring board.SOLUTION: A wiring board 1A incorporates a post-wall waveguide 1w in which an area surrounded by two opposing conductors 13c and 23c and first and second post walls 31 and 32 connecting the two conductors becomes a transmission path for an electromagnetic wave. The two conductors are disposed to face each other with n (n is a natural number greater than or equal to two) insulating layers 14 to 22 interposed therebetween. The first post wall and the second post wall have a configuration in which columnar portions 33 in which via wirings 15v to 23v penetrating respective insulating layers and pads 15p to 21p located between the via wirings are stacked are arranged at predetermined intervals in a first direction in which the electromagnetic wave is transmitted. In each of the first post wall and the second post wall, the pad is arranged in contact with an m-th insulation layer, and includes two or more connection pads that couples two or more via wirings arranged in the first direction in the m-th insulation layer.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] A technique called a post-wall waveguide has been proposed. The post-wall waveguide has, for example, conductor foils formed on the upper and lower surfaces of a dielectric block, side post walls, and a rear post wall. The side post walls and the rear post wall are formed of, for example, a plurality of metal pillars penetrating the dielectric block vertically, and both upper and lower end faces of the metal pillars are connected to the conductor foils (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is also possible to form a post wall by using a processing technique of a wiring board, for example, by a laminated structure of via wiring and pads.

[0005] However, since the post-wall waveguide is intended for confining electromagnetic waves and not for conducting electricity, there may be cases where no connection for flowing electricity is made to the via wiring or pads. In such cases, for example, even if cracks or peeling occur at the connection portion between the via wiring and the pads, it is difficult to detect them by checking electrical continuity.

[0006] The present invention has been made in view of the above points, and an object thereof is to improve the connection reliability between via wiring and pads in a post-wall waveguide built in a wiring board.

Means for Solving the Problems

[0007] This wiring board incorporates a post-wall waveguide in which the region enclosed by two opposing conductors and a first post wall and a second post wall connecting the two conductors serves as an electromagnetic wave transmission path. The two conductors are arranged opposite each other with an n-layer (n is a natural number of 2 or more) insulating layer in between. The first post wall and the second post wall have columnar portions in which via wirings penetrating each insulating layer and pads located between vertically adjacent via wirings are stacked and arranged at predetermined intervals in a first direction for transmitting electromagnetic waves. In each of the first post wall and the second post wall, the pads are arranged in contact with the m-th layer (m is a natural number of 1 or more and n-1 or less) insulating layer and connect two or more via wirings arranged in the first direction within the m-th layer insulating layer. discrete Includes two or more connecting pads. [Effects of the Invention]

[0008] According to the disclosed technology, the reliability of the connection between vias and pads can be improved in post-wall waveguides embedded in a wiring board. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view illustrating a wiring board according to the first embodiment. [Figure 2] This is a cross-sectional view illustrating a wiring board according to the first embodiment. [Figure 3] This figure illustrates the manufacturing process of a wiring board according to the first embodiment. [Figure 4] This figure illustrates a wiring board according to a modified example 1 of the first embodiment. [Figure 5] This figure illustrates a wiring board according to a modified example 2 of the first embodiment. [Figure 6] This figure illustrates a wiring board according to a modified example 3 of the first embodiment. [Figure 7] This figure illustrates a wiring board according to a modified example 4 of the first embodiment. [Figure 8] This is a diagram explaining the simulation. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the invention will be described below with reference to the drawings. In each drawing, the same reference numerals are used for identical components, and redundant explanations may be omitted.

[0011] <First Embodiment> [Overall structure of the wiring board] Figure 1 is a plan view illustrating a wiring board according to the first embodiment, where Figure 1(a) is a view below the insulating layer 24 in Figure 2, and Figure 1(b) is a view below the wiring layer 19 in Figure 2. Figure 2 is a cross-sectional view illustrating a wiring board according to the first embodiment, where Figure 2(a) is a cross-sectional view along line AA in Figure 1, and Figure 2(b) is a cross-sectional view along line BB in Figure 1.

[0012] In each drawing, for reference, mutually orthogonal X, Y, and Z axes are shown as needed. The direction parallel to the X axis is called the X direction, the direction parallel to the Y axis is called the Y direction, and the direction parallel to the Z axis is called the Z direction. However, these do not restrict the orientation of the wiring board 1 when it is used.

[0013] Referring to Figures 1 and 2, the wiring board 1 has a wiring layer 11, an insulating layer 12, a conductor 13c, an insulating layer 14, a wiring layer 15, an insulating layer 16, a wiring layer 17, an insulating layer 18, a wiring layer 19, an insulating layer 20, a wiring layer 21, an insulating layer 22, a wiring layer 23, an insulating layer 24, and a wiring layer 25. The wiring board 1 may have a solder resist layer on the insulating layer 24 that selectively exposes the wiring layer 25. The wiring board 1 incorporates a post-wall waveguide 1w. The post-wall waveguide 1w will be described later.

[0014] In this embodiment, for convenience, the wiring layer 25 side of the wiring board 1 in FIG. 1 is regarded as the upper side or one side, and the wiring layer 11 side is regarded as the lower side or the other side. Also, the surface on the wiring layer 25 side of each part is regarded as one surface or the upper surface, and the surface on the wiring layer 11 side is regarded as the other surface or the lower surface. However, the wiring board 1 can be used in an upside-down state or arranged at an arbitrary angle. In addition, the plan view means viewing the object from the normal direction of one surface of the insulating layer 24, and the planar shape means the shape of the object viewed from the normal direction of one surface of the insulating layer 24.

[0015] In the examples of FIGS. 1 and 2, the planar shape of the wiring board 1 is rectangular, and the wiring board 1 has two sides parallel to the X direction and two sides parallel to the Y direction in plan view. The thickness direction of the wiring board 1 is the Z direction.

[0016] In the wiring board 1, the wiring layer 11 is embedded on the lower surface side of the insulating layer 12. The lower surface of the wiring layer 11 is exposed from the lower surface of the insulating layer 12, and the upper surface and side surfaces of the wiring layer 11 are covered by the insulating layer 12. As the material of the wiring layer 11, for example, copper (Cu) or the like can be used. The wiring layer 11 may have a laminated structure of a plurality of metal layers. The thickness of the wiring layer 11 can be, for example, about 10 to 30 μm.

[0017] The insulating layer 12 is formed so as to cover the side surface and the upper surface of the wiring layer 11. The lower surface of the insulating layer 12 can be, for example, flush with the lower surface of the wiring layer 11. As the material of the insulating layer 12, for example, an insulating resin mainly composed of an epoxy resin or a polyimide resin can be used. The thickness of the insulating layer 12 can be, for example, about 20 to 40 μm. Here, the thickness of the insulating layer 12 refers to the distance from the upper surface of the wiring layer 11 to the upper surface of the insulating layer 12. The same applies to the thickness of the insulating layer hereinafter. The insulating layer 12 can contain a filler such as silica (SiO2).

[0018] The conductor 13c is a solid pattern formed on the upper surface of the insulating layer 12. The conductor 13c is, for example, rectangular in plan view. The material and thickness of the conductor 13c can be, for example, the same as those of the wiring layer 11.

[0019] The insulating layer 14 is disposed on the upper surface of the insulating layer 12 and covers the upper surface and the side surface of the conductor 13c. The material and thickness of the insulating layer 14 can be the same as those of the insulating layer 12, for example. The insulating layer 14 can contain fillers such as silica (SiO2).

[0020] The wiring layer 15 includes via wirings 15v filled in via holes 14x penetrating the insulating layer 14 and exposing the upper surface of the conductor 13c, and pads 15p formed on the upper surface of the insulating layer 14. The via wiring 15v can have an inverted frustum shape with a diameter on the wiring layer 17 side larger than that on the conductor 13c side. For example, the diameter on the wiring layer 17 side can be about 70 μm, and the diameter on the conductor 13c side can be about 50 μm. The wiring layer 15 is electrically connected to the conductor 13c exposed at the bottom of the via hole 14x. The material of the wiring layer 15 and the thickness of the pad 15p can be the same as those of the wiring layer 11, for example.

[0021] The insulating layer 16 is disposed on the upper surface of the insulating layer 14 and covers the upper surface and the side surface of the pad 15p of the wiring layer 15. The material and thickness of the insulating layer 16 can be the same as those of the insulating layer 12, for example. The insulating layer 16 can contain fillers such as silica (SiO2).

[0022] The wiring layer 17 includes via wirings 17v filled in via holes 16x penetrating the insulating layer 16 and exposing the upper surface of the pad 15p of the wiring layer 15, and pads 17p formed on the upper surface of the insulating layer 16. The via wiring 17v can have an inverted frustum shape with a diameter on the wiring layer 19 side larger than that on the wiring layer 15 side. The wiring layer 17 is electrically connected to the wiring layer 15 exposed at the bottom of the via hole 16x. The material of the wiring layer 17 and the thickness of the pad 17p can be the same as those of the wiring layer 11, for example.

[0023] The insulating layer 18 is positioned on the upper surface of the insulating layer 16 and covers the upper and side surfaces of the pads 17p of the wiring layer 17. The material and thickness of the insulating layer 18 can be the same as, for example, the insulating layer 12. The insulating layer 18 may contain fillers such as silica (SiO2).

[0024] The wiring layer 19 comprises via wiring 19v filled in via holes 18x that penetrate the insulating layer 18 and expose the upper surface of the pad 17p of the wiring layer 17, and a pad 19p formed on the upper surface of the insulating layer 18. The via wiring 19v can be in the shape of an inverted frustocone, where the diameter on the wiring layer 21 side is larger than the diameter on the wiring layer 17 side. The wiring layer 19 is electrically connected to the wiring layer 17 exposed at the bottom of the via hole 18x. The material of the wiring layer 19 and the thickness of the pad 19p can be the same as, for example, the same as those of the wiring layer 11.

[0025] The insulating layer 20 is positioned on the upper surface of the insulating layer 18 and covers the upper and side surfaces of the pads 19p of the wiring layer 19. The material and thickness of the insulating layer 20 can be the same as, for example, the insulating layer 12. The insulating layer 20 may contain fillers such as silica (SiO2).

[0026] The wiring layer 21 consists of via wiring 21v filled in via holes 20x that penetrate the insulating layer 20 and expose the upper surface of the pad 19p of the wiring layer 19, and a pad 21p formed on the upper surface of the insulating layer 20. The via wiring 21v can be in the shape of an inverted frustocone, where the diameter on the wiring layer 23 side is larger than the diameter on the wiring layer 19 side. The wiring layer 21 is electrically connected to the wiring layer 19 exposed at the bottom of the via holes 20x. The material of the wiring layer 21 and the thickness of the pad 21p can be the same as, for example, the same as those of the wiring layer 11.

[0027] The insulating layer 22 is positioned on the upper surface of the insulating layer 20 and covers the upper and side surfaces of the pads 21p of the wiring layer 21. The material and thickness of the insulating layer 22 can be the same as, for example, the insulating layer 12. The insulating layer 22 may contain fillers such as silica (SiO2).

[0028] The wiring layer 23 comprises via wiring 23v filled in via holes 22x that penetrate the insulating layer 22 and expose the upper surface of the pad 21p of the wiring layer 21, and a conductor 23c formed on the upper surface of the insulating layer 22. The via wiring 23v can be in the shape of an inverted frustocone, where the diameter on the wiring layer 25 side is larger than the diameter on the wiring layer 21 side. The conductor 23c is a solid pattern. The conductor 23c is, for example, rectangular in plan view. The shape and area of ​​the conductor 23c are, for example, the same as those of the conductor 13c. The wiring layer 23 is electrically connected to the wiring layer 21 exposed at the bottom of the via holes 22x. The material of the wiring layer 23 and the thickness of the conductor 23c can be, for example, the same as those of the wiring layer 11.

[0029] [Post-wall waveguide] As shown in Figures 1 and 2, the wiring board 1 incorporates a post-wall waveguide 1w, the region enclosed by two conductors 13c and 23c facing each other in the Z direction, and a first post wall 31 and a second post wall 32 connecting conductor 13c and conductor 23c, which serves as the electromagnetic wave transmission path 1t. In the example shown in Figures 1 and 2, the direction of electromagnetic wave transmission is the X direction. Note that the transmission path 1t is not limited to being straight; it may be curved, or a mixture of straight and curved sections may be present.

[0030] The two conductors of the wiring board according to the present invention are arranged opposite each other with an n-layer (n is a natural number of 2 or more) insulating layer in between. The first post wall and the second post wall are configured such that columnar portions, each consisting of via wiring penetrating the respective insulating layer and pads located between adjacent via wirings vertically, are arranged at predetermined intervals in the X direction for electromagnetic wave transmission.

[0031] In the example of the wiring board 1 shown in Figures 1 and 2, n=5, and the conductor 23c is positioned opposite the conductor 13c via insulating layers 14, 16, 18, 20, and 22. The columnar portion 33 is configured by sequentially stacking via wiring 15v, pad 15p, via wiring 17v, pad 17p, via wiring 19v, pad 19p, via wiring 21v, pad 21p, and via wiring 23v.

[0032] The first post wall 31 and the second post wall 32 face each other at a predetermined distance in the Y direction. The Y-direction pitch between the first post wall 31 and the second post wall 32 (the distance in the Y direction between the central axes of the via wirings facing each other in the Y direction) can be, for example, 0.82 mm. The X-direction length of each of the first post wall 31 and the second post wall 32 can be, for example, 5 mm.

[0033] In the first post wall 31 and the second post wall 32, the central axes of the via wirings 15v, 17v, 19v, 21v, and 23v constituting the columnar portion 33 are approximately coincident. The pitch of the columnar portion 33 in the X direction (the distance in the X direction between the central axes of adjacent via wirings in the X direction) can be, for example, 0.125 mm. The frequency of electromagnetic waves that can be transmitted through the transmission line 1t can be, for example, 150 GHz to 160 GHz.

[0034] In each of the first and second post walls of the wiring board according to the present invention, the pad includes at least two connecting pads that are arranged in contact with the m-th insulating layer (where m is a natural number between 1 and n-1) and connect two or more via connections arranged in the X direction within the m-th insulating layer. Preferably, each via connection within the m-th insulating layer is connected to one of the connecting pads.

[0035] In the example of the wiring board 1 shown in Figures 1 and 2, m=3. That is, in the wiring board 1, at each of the first post wall 31 and the second post wall 32, the pads of the wiring board 1 are arranged in contact with the third insulating layer 18 located between the conductor 13c and the conductor 23c, and include two connecting pads that connect four via wirings 19v arranged in the X direction within the insulating layer 18. The four pads 19p shown as a dot pattern in Figure 1(b) are the connecting pads. The width (Y direction) of the connecting pads can be, for example, 100 to 120 μm.

[0036] Furthermore, the wiring board 1 does not need to have insulating layers or wiring layers other than those constituting the post-wall waveguide 1w. In other words, the wiring board 1 itself may be the post-wall waveguide 1w.

[0037] Furthermore, the wiring board 1 may be mounted on or incorporate a semiconductor chip. This semiconductor chip is capable of, for example, transmitting and / or receiving electromagnetic waves transmitted through the transmission path 1t.

[0038] Thus, the wiring board 1 includes two or more connecting pads in each of the first post wall 31 and the second post wall 32 that are arranged in contact with at least one insulating layer and connect two or more via wirings arranged in the X direction that transmit electromagnetic waves within the insulating layer. This provides the following effects.

[0039] In other words, if a connecting pad is not present, stress is applied to the connection between the bottom surface of the via wiring and the top surface of the pad, making it prone to cracking, and these cracks may extend and lead to delamination. In contrast, when a connecting pad is present, as in wiring board 1, the stress is distributed by the connecting pad, making it less likely for cracks to occur. Furthermore, when a connecting pad is present, the contact area between the pad and the insulating layer increases compared to when a connecting pad is not present, resulting in an anchoring effect and increasing the connection strength between the via wiring and the pad.

[0040] These improvements enhance the reliability of the connections between vias and pads in the post-wall waveguide 1w embedded in the wiring board 1. Specifically, the structural strength of the first and second post walls, where defects are difficult to detect electrically, can be improved, thereby enhancing the overall reliability of the wiring board 1.

[0041] Furthermore, in the wiring board 1, each via wiring is connected to one of the connecting pads within the third insulating layer 18. In other words, there are no independent via wirings within the third insulating layer 18 that are not connected to adjacent via wirings. This further enhances the above-mentioned effect.

[0042] Furthermore, if only one connecting pad is provided within a single insulating layer in each of the first and second post walls to connect two or more via wirings arranged in the X direction that transmit electromagnetic waves, delamination is likely to occur, especially when the length of the connecting pad is long, due to the difference in elongation caused by the difference in thermal expansion coefficients between the connecting pad and the resin. For this reason, it is not preferable to provide only one connecting pad within a single insulating layer in each of the first and second post walls.

[0043] [Manufacturing method for wiring boards] Next, a method for manufacturing a wiring board according to the first embodiment will be described. Figure 3 is a diagram illustrating the manufacturing process of a wiring board according to the first embodiment. Here, an example of a process in which a layer structure is formed on only one side of the support is shown, but a process in which a layer structure is formed on both one and the other side of the support may also be used. The dashed lines C in each figure indicate the cutting positions when the wiring board is divided into individual pieces. In a cross-sectional view, the region located between adjacent dashed lines C is ultimately divided into individual pieces to form a single wiring board.

[0044] First, in the process shown in Figure 3(a), a support 300 is prepared, and a wiring layer 11, an insulating layer 12, and a conductor 13c are sequentially laminated on the support 300. The support 300 has a structure in which a carrier-attached copper foil 304 is laminated on one side of a core substrate 301. The core substrate 301 is, for example, a resin substrate with a thickness of about 0.7 mm and may have reinforcing members such as glass fibers. The carrier-attached copper foil 304 has a structure in which a thin foil 304a, for example, made of copper with a thickness of about 1.5 to 5 μm is attached in a peelable state to a thick foil (carrier foil) 304b made of copper with a thickness of about 10 to 50 μm, via a release layer (not shown). The thick foil 304b is provided as a support material to facilitate handling of the thin foil 304a.

[0045] The structure of the support 300 described above is merely an example and is not limited thereto. For example, instead of the core substrate 301, a laminate in which multiple prepregs are stacked may be used in the support 300. Alternatively, the support 300 may have a structure in which a copper foil 304 with a carrier is placed on one side of a glass substrate or metal substrate via a release layer.

[0046] To form the wiring layer 11 on the support 300, for example, a resist layer with openings in the area where the wiring layer 11 will be formed is formed on the upper surface of the carrier-attached copper foil 304 (the upper surface of the thin foil 304a) using a dry film resist or the like. Then, by an electroplating method using the carrier-attached copper foil 304, which is a metal layer, as the power supply layer, the wiring layer 11, which is an electroplated layer, is formed on the upper surface of the carrier-attached copper foil 304 exposed in the openings. The material and thickness of the wiring layer 11 are as described above. After that, the resist layer is peeled off and removed.

[0047] To form the insulating layer 12, for example, a semi-cured film-like insulating resin mainly composed of a thermosetting resin is prepared. Then, this insulating resin is laminated onto the upper surface of the carrier-attached copper foil 304 and cured under heat and pressure to form the insulating layer 12. Alternatively, instead of laminating with a film-like insulating resin, a liquid or paste-like insulating resin may be applied and then cured to form the insulating layer 12. The material and thickness of the insulating layer 12 are as described above. The conductor 13c can be formed using various wiring formation methods such as the subtractive method and the semi-additive method. The shape, material, and thickness of the conductor 13c are as described above.

[0048] Next, in the process shown in Figure 3(b), an insulating layer 14 is formed on the upper surface of the insulating layer 12 to cover the conductor 13c. The insulating layer 14 can be formed, for example, by the same method as the insulating layer 12. The material and thickness of the insulating layer 14 are as described above.

[0049] Next, in the process shown in Figure 3(c), via holes 14x are formed in the insulating layer 14, penetrating the insulating layer 14 and exposing the upper surface of the conductor 13c. The via holes 14x can be formed by a laser processing method using, for example, a CO2 laser, a YAG laser, or an excimer laser. After forming the via holes 14x, it is preferable to perform a desmear treatment to remove the resin residue adhering to the surface of the conductor 13c exposed at the bottom of each via hole 14x.

[0050] Next, in the process shown in Figure 3(d), a wiring layer 15 is formed on the insulating layer 14. The wiring layer 15 can be formed, for example, by a semi-additive method. Specifically, for example, a seed layer that continuously covers the upper surface of the insulating layer 14, the inner surface of the via hole 14x, and the upper surface of the conductor 13c exposed within the via hole 14x is formed by electroless copper plating or copper sputtering. Next, a resist layer having openings that match the shape of the wiring layer 15 is formed on the seed layer. Then, an electroplated layer is formed on the seed layer exposed within the openings by an electroplating method using the seed layer as a power supply layer. Next, after removing the resist layer, the seed layer exposed from the electroplated layer is removed by etching, and a wiring layer 15 is formed in which the electroplated layer is laminated on the seed layer. The wiring layer 15 consists of via wiring 15v filled in the via hole 14x and pads 15p formed on the upper surface of the insulating layer 14.

[0051] Next, the same process as in Figures 3(b) to 3(d) is repeated to sequentially form the insulating layer 16, via holes 16x, wiring layer 17, insulating layer 18, via holes 18x, wiring layer 19, insulating layer 20, via holes 20x, wiring layer 21, insulating layer 22, via holes 22x, and wiring layer 23. Furthermore, the insulating layer 24 and wiring layer 25 are formed in the same manner as in Figure 3(a).

[0052] Next, the support 300 is removed. To remove the support 300, first, the core substrate 301 and the thick foil 304b are mechanically peeled off from the thin foil 304a. Then, the thin foil 304a is removed by wet etching using, for example, an aqueous solution of ferric chloride, an aqueous solution of cupric chloride, or an aqueous solution of ammonium persulfate. After that, individual wiring boards 1 can be obtained by cutting along the dashed line C.

[0053] <Variations of the first embodiment> A modified example of the first embodiment shows a wiring board equipped with connecting pads of a different shape. In the modified example of the first embodiment, descriptions of components that are the same as those described in the previously described embodiment may be omitted.

[0054] Figure 4 illustrates a wiring board according to Modification 1 of the First Embodiment, where Figure 4(a) is a cross-sectional view corresponding to Figure 2(a), and Figure 4(b) is a plan view looking below the wiring layer 21 in Figure 4(a). The plan views looking below the wiring layer 19, below the wiring layer 17, and below the wiring layer 15 are the same as in Figure 4(b).

[0055] In the example of the wiring board 1A shown in Figure 4, the pads of the wiring board 1A are arranged in contact with each of the insulating layers from the 1st layer to the (n-1)th layer, and include two or more connecting pads that connect two or more via connections arranged in the X direction within each insulating layer. Here, n=5.

[0056] In other words, in the wiring board 1A, the pads of the wiring board 1A are located in contact with the first insulating layer 14, which is situated between conductors 13c and 23c, and include two connecting pads that connect two via connections arranged in the X direction within the insulating layer 14.

[0057] The two connecting pads placed in each insulating layer can be positioned in overlapping locations in a plan view. That is, the two connecting pads placed in each insulating layer can be arranged in a matrix in a cross-sectional view. In the example in Figure 4, the connecting pads are arranged in a 4x2 grid in a cross-sectional view. There may be three or more connecting pads placed in each insulating layer. Also, some or all of the connecting pads may connect three or more via connections.

[0058] Thus, the wiring board 1A includes two or more connecting pads that are positioned in contact with each insulating layer located between the conductor 13c and the conductor 23c, and that connect two or more via wirings arranged in the X direction for transmitting electromagnetic waves within each insulating layer.

[0059] This further enhances the stress distribution provided by the connecting pads and the connection strength between the via wiring and the pads due to the anchoring effect, compared to the wiring board 1. Therefore, the connection reliability between the via wiring and the pads in the post-wall waveguide 1w built into the wiring board 1A can be further improved compared to the wiring board 1.

[0060] Figure 5 illustrates a wiring board according to a modified example 2 of the first embodiment, where Figure 5(a) is a cross-sectional view corresponding to Figure 2(a), and Figure 5(b) is a plan view looking below the wiring layer 21 in Figure 5(a). The plan views looking below the wiring layer 19, below the wiring layer 17, and below the wiring layer 15 are the same as in Figure 5(b).

[0061] In the example of the wiring board 1B shown in Figure 5, the pads of the wiring board 1B in each of the first post wall 31 and the second post wall 32 are arranged in contact with each insulating layer located between the conductor 13c and the conductor 23c, and each insulating layer contains four connecting pads that connect two via connections arranged in the X direction that transmit electromagnetic waves. In the example in Figure 5, the connecting pads are arranged in a 4x4 grid in cross-sectional view. In the wiring board 1B, each via connection in each insulating layer is connected to one of the connecting pads. In other words, in the wiring board 1B, there are no independent via connections that are not connected to adjacent via connections.

[0062] This further enhances the stress distribution provided by the connecting pads and the connection strength between the via wiring and the pads due to the anchoring effect, compared to the wiring board 1A. Therefore, the connection reliability between the via wiring and the pads in the post-wall waveguide 1w built into the wiring board 1B can be further improved compared to the wiring board 1A.

[0063] Figure 6 illustrates a wiring board according to modification 3 of the first embodiment, where Figure 6(a) is a cross-sectional view corresponding to Figure 2(a), and Figure 6(b) is a plan view looking below the wiring layer 19 in Figure 6(a). The plan view looking below the wiring layer 15 is the same as in Figure 6(b). The plan views looking below the wiring layer 21 and below the wiring layer 17 are the same as in Figure 5(b).

[0064] In the example of the wiring board 1C shown in Figure 6, the pads of the wiring board 1C in each of the first post wall 31 and the second post wall 32 are arranged in contact with each insulating layer located between the conductor 13c and the conductor 23c, and each insulating layer contains three or four connecting pads that connect two via connections arranged in the X direction for transmitting electromagnetic waves. In the example of Figure 6, the connecting pads are arranged in a staggered pattern in cross-sectional view. In the wiring board 1C, there may be via connections that are not connected to adjacent via connections. There may be two or more connecting pads arranged in each insulating layer. In addition, some or all of the connecting pads may connect three or more via connections.

[0065] Thus, the connecting pads may be arranged in a staggered pattern in cross-section. In this case as well, the stress distribution by the connecting pads and the effect of increased connection strength between the via wiring and the pads due to the anchoring effect are further enhanced than in the wiring board 1. Therefore, the connection reliability between the via wiring and the pads in the post-wall waveguide 1w built into the wiring board 1C can be further improved than in the wiring board 1.

[0066] Figure 7 illustrates a wiring board according to modification 4 of the first embodiment, where Figure 7(a) is a cross-sectional view corresponding to Figure 2(a), and Figure 7(b) is a plan view looking below the wiring layer 21 in Figure 7(a). The plan view looking below the wiring layer 17 is the same as that of Figure 6(b). The plan views looking below the wiring layer 19 and below the wiring layer 15 are the same as those of Figure 5(b).

[0067] In the example of the wiring board 1D shown in Figure 7, insulating layers (insulating layers 16 and 20) in which all via wirings arranged in the X direction for transmitting electromagnetic waves are independent, and insulating layers (insulating layers 14 and 18) containing two or more connecting pads are alternately stacked. Two or more connecting pads are required to be placed on insulating layers 14 and 18. In addition, some or all of the connecting pads placed on insulating layers 14 and 18 may connect three or more via wirings.

[0068] Thus, the wiring board may have an insulating layer in which all via wirings arranged in the X direction for transmitting electromagnetic waves are independent. In this case as well, the stress distribution by the connecting pads and the effect of increased connection strength between the via wirings and pads due to the anchoring effect are further enhanced than in wiring board 1, so that the connection reliability between the via wirings and pads in the post-wall waveguide 1w built into wiring board 1D can be further improved than in wiring board 1.

[0069] [simulation] Focusing on plastic strain as one indicator to confirm the connection reliability between via wiring and pads, we simulated plastic strain for the wiring boards of Comparative Example, Example 1, and Example 2 using nonlinear static analysis with Abaqus 2021. Specifically, with a stress-free temperature of 210°C and an analysis temperature of 25°C, we simulated the maximum values ​​of plastic strain generated in the via wiring and pads.

[0070] All of the wiring boards in the Comparative Example, Example 1, and Example 2 were rectangular in shape, measuring 1.37 mm × 1.37 mm in plan view. Furthermore, as shown in Figure 8(a), all of the wiring boards had three insulating layers between opposing conductors. The wiring board in the Comparative Example had no connecting pads. The wiring board in Example 1 had the structure corresponding to Figure 5, with connecting pads linking two adjacent via connections arranged in a 2x4 grid, and no independent via connections. The wiring board in Example 2 had the structure corresponding to Figure 6, with connecting pads linking two adjacent via connections arranged in a staggered pattern, and independent via connections existed.

[0071] As shown in Figure 8(b), the simulation results of plastic strain showed that the maximum value of plastic strain in the wiring board of Example 1 was reduced by 5.33% compared to the wiring board of the comparative example. Furthermore, the maximum value of plastic strain in the wiring board of Example 2 was reduced by 2.74% compared to the wiring board of the comparative example.

[0072] In other words, it was confirmed that by providing connecting pads on the wiring board, plastic strain can be reduced compared to cases where connecting pads are not provided, and the reliability of the connection between via wiring and pads can be improved. Furthermore, it is expected that structures other than those in Examples 1 and 2 will also have a certain effect in reducing plastic strain if at least one connecting pad is provided compared to cases where no connecting pad is provided.

[0073] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. [Explanation of Symbols]

[0074] 1,1A,1B,1C,1D Wiring board 1t transmission route 1W Post-Wall Waveguide 11,15,17,19,21,23,25 wiring layer 12,14,16,18,20,22,24 Insulating layer 13c, 23c conductor 14x, 16x, 18x, 20x, 22x Beer Hall 15p, 17p, 19p, 21p pad 15V, 17V, 19V, 21V, 23V via wiring 31 First Post Wall 32 Second Post Wall 33 Columnar part 300 Support 301 Core board 304 Copper foil with carrier 304a thin foil 304b thick foil

Claims

1. A wiring board incorporating a post-wall waveguide in which the region enclosed by two opposing conductors and a first post wall and a second post wall connecting the two conductors becomes an electromagnetic wave transmission path, The two conductors are arranged facing each other with an n-layer (where n is a natural number of 2 or more) insulating layer in between. The first post wall and the second post wall are configured such that columnar portions, each consisting of via wiring penetrating the respective insulating layer and pads located between adjacent via wirings, are arranged at predetermined intervals in the first direction for transmitting electromagnetic waves. A wiring board in which, in each of the first post wall and the second post wall, the pad is arranged in contact with the m-th layer (where m is a natural number between 1 and n-1) of the insulating layer, and includes two or more discrete connecting pads that connect two or more via connections arranged in the first direction within the m-th layer of the insulating layer.

2. The wiring board according to claim 1, wherein each of the vias is connected to one of the connecting pads within the m-th insulating layer.

3. The wiring board according to claim 1 or 2, wherein the pads are arranged in contact with each of the insulating layers from the first layer to the (n-1)th layer, and include two or more connecting pads that connect two or more via connections arranged in the first direction within each of the insulating layers.

4. The wiring board according to claim 3, wherein the connecting pads are arranged in a matrix in a cross-sectional view taken parallel to the first direction and in the direction of lamination of the insulating layer.

5. The wiring board according to claim 4, wherein in each of the insulating layers, each of the via wirings is connected to one of the connecting pads.

6. The wiring board according to claim 3, wherein the connecting pads are arranged in a staggered pattern in a cross-sectional view taken parallel to the first direction and in the direction of lamination of the insulating layer.

7. The wiring board according to claim 1 or 2, wherein the insulating layer, in which all of the via wirings arranged in the first direction are independent, and the insulating layer, which includes two or more connecting pads, are alternately laminated.

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