Printed wiring board

Abstract

A printed wiring board comprising a first insulating layer and a through-hole conductor. The first insulating layer has a through-hole extending therethrough from a first surface of the first insulating layer to a second surface thereof opposite the first surface. The through-hole conductor comprises a portion located on the inner wall of the through-hole and having an opening area in a cross section parallel to the second surface that increases from the first surface side toward the second surface side.

Description

[Technical field]

[0001] The present disclosure relates to printed wiring boards. [Background technology]

[0002] Conventionally, a technique is known in which a waveguide extending in the thickness direction of a printed wiring board is used to transmit a signal from one side of the printed wiring board to the other side (for example, JP 2015-139042 A). Conventional waveguides have no change in diameter at each position in the thickness direction of the printed wiring board. Summary of the Invention

[0003] A printed wiring board according to one embodiment of the present disclosure includes: a first surface, a second surface opposite to the first surface, and From page 1 The above Through holes extending to the second surface and have A first insulating layer is provided. . The printed wiring board is a portion located on an inner wall of the through hole, the portion having an opening area in a cross section parallel to the second surface increasing from the first surface side toward the second surface side; Equipped with through-hole conductors . The printed wiring board includes a first conductor layer located on the second surface of the first insulating layer and electrically connected to the through-hole conductor, a resin filling a space surrounded by the through-hole conductor, a second insulating layer provided on the first conductor layer, and a plurality of via conductors penetrating the second insulating layer. The plurality of via conductors are electrically connected to the first conductor layer and are arranged to surround the second surface opening of the through-hole conductor on the second surface in a plan view toward the second surface. The through-hole conductor is located only on the inner wall of the through hole of the first insulating layer and is not located in the second insulating layer. [Brief description of the drawings]

[0004] [Figure 1] 1A and 1B are a plan view and a cross-sectional view of a printed wiring board according to a first embodiment. [Diagram 2] FIG. 11 is a plan view of a printed wiring board according to a first modified example. [Diagram 3] FIG. 11 is a plan view of another printed wiring board according to Modification 1. [Figure 4] FIG. 11 is a plan view of another printed wiring board according to Modification 1. [Diagram 5] FIG. 11 is a plan view of another printed wiring board according to Modification 1. [Figure 6] FIG. 11 is a plan view of another printed wiring board according to Modification 1. [Figure 7] FIG. 11 is a cross-sectional view of a printed wiring board according to Modification 2. [Figure 8] 11 is a cross-sectional view of another printed wiring board according to Modification 2. FIG. [Figure 9] FIG. 4 is a cross-sectional view of a printed wiring board according to a second embodiment. [Figure 10] 11A and 11B are a plan view and a cross-sectional view of a printed wiring board according to a third embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a printed wiring board according to a fourth embodiment. [Figure 12] FIG. 13 is a cross-sectional view of a printed wiring board according to a fifth embodiment. [Figure 13] FIG. 13 is a cross-sectional view of a printed wiring board according to a sixth embodiment. [Figure 14] 5A to 5C are cross-sectional views illustrating a method for manufacturing a printed wiring board. [Figure 15] 5A to 5C are cross-sectional views illustrating a method for manufacturing a printed wiring board. [Figure 16] 5A to 5C are cross-sectional views illustrating a method for manufacturing a printed wiring board. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Hereinafter, the embodiments will be described with reference to the drawings. However, for the sake of convenience, each of the drawings referred to below shows only the main components necessary for explaining the embodiments in a simplified form. Therefore, the printed wiring board 1 of the present disclosure may include any component not shown in each of the drawings referred to. Furthermore, the dimensions of the components in each drawing do not faithfully represent the dimensions and dimensional ratios of the actual components.

[0006] [First embodiment] As shown in Fig. 1, printed wiring board 1 according to the first embodiment includes a first insulating layer 11 and a through-hole conductor 20. In the following, the orientation of each part of printed wiring board 1 will be described using an XYZ orthogonal coordinate system in which the thickness direction of printed wiring board 1 is the Z direction. In addition, the surface of each layer constituting printed wiring board 1 facing the +Z direction will be referred to as the "upper surface," and the surface facing the -Z direction will be referred to as the "lower surface." Also, a view from the Z direction will be referred to as a "planar view."

[0007] The first insulating layer 11 is a plate-shaped member made of an insulating material. Hereinafter, the lower surface of the first insulating layer 11 will be referred to as the first surface S1, and the upper surface (the surface opposite to the first surface S1) will be referred to as the second surface S2. The first surface S1 and the second surface S2 are parallel to the XY plane. Hereinafter, a cross section parallel to the second surface S2 will be referred to as a "transverse cross section", and a cross section perpendicular to the second surface S2 will be referred to as a "longitudinal cross section".

[0008] The material of the first insulating layer 11 is not particularly limited as long as it has insulating properties. Examples of the material of the first insulating layer 11 include epoxy resin, bismaleimide-triazine resin, polyimide resin, polyphenylene ether (PPE) resin, phenol resin, polytetrafluoroethylene (PTFE) resin, silicon resin, polybutadiene resin, polyester resin, melamine resin, urea resin, polyphenylene sulfide (PPS) resin, and polyphenylene oxide (PPO) resin. Two or more of these resins may be mixed. In addition, the first insulating layer 11 may contain a fibrous base material such as glass cloth in order to increase the strength of the printed wiring board 1. In addition, the first insulating layer 11 may contain an inorganic filler such as aluminum hydroxide, silica, or barium sulfate, or an organic filler such as a phenol resin or a methacrylic resin.

[0009] The first insulating layer 11 has a through hole 111 penetrating from the first surface S1 to the second surface S2. An inner wall 112 of the through hole 111 has a shape of a side surface of a circular truncated cone. Therefore, the shape of the opening of the through hole 111 at the first surface S1, the opening at the second surface S2, and the opening at any cross section are all circular. Furthermore, the radius of the circle formed by these openings increases from the first surface S1 toward the second surface S2.

[0010] The through-hole conductor 20 is located on the inner wall 112 of the through hole 111 and extends from the first surface S1 to the second surface S2 along the inner wall 112. The through-hole conductor 20 has a substantially uniform thickness. Thus, the inner wall 203 of the through-hole conductor 20 has a shape of a side surface of a truncated cone, similar to the inner wall 112 of the through hole 111. The through-hole conductor 20 has a first surface opening 201 on the first surface S1 and a second surface opening 202 on the second surface S2 that are not blocked by other conductors. The first surface opening 201, the second surface opening 202, and the opening in any cross section of the through-hole conductor 20 are all circular in shape. The radius of the circle formed by these openings increases from the first surface S1 to the second surface S2 toward the second surface S2. Therefore, the through-hole conductor 20 has an opening area in a cross section that increases from the first surface S1 to the second surface S2. In addition, in any vertical section passing through the central axis of the through hole 111, the opening width in a direction parallel to the second surface S2 (opening width in the X direction in FIG. 1) increases (expands) from the first surface S1 to the second surface S2 toward the second surface S2. In addition, in any vertical section passing through the central axis of the through hole 111, the through-hole conductor 20 has a portion that is inclined with respect to a direction perpendicular to the second surface S2 (Z direction). More specifically, in the vertical section, the through-hole conductor 20 has a portion where the inner wall 203 is inclined with respect to a direction perpendicular to the second surface S2. From another perspective, the through-hole conductor 20 has a portion where the opening area in a cross section increases from the first surface S1 side toward the second surface S2 side. Through-hole conductor 20 may be, for example, a metal (plating layer) such as copper, nickel and / or gold formed on inner wall 112 of through hole 111 by plating.

[0011] The through-hole conductor 20 functions as a waveguide that propagates electromagnetic waves from the first surface opening 201 to the second surface opening 202 as shown by the white arrow in FIG. 1. The through-hole conductor 20 as a waveguide propagates electromagnetic waves with a wavelength λ that satisfies both λ / 2≦D1≦λ and λ / 2≦D2≦λ, where D1 is the diameter of the first surface opening 201 and D2 is the diameter of the second surface opening 202. By using this waveguide, electromagnetic waves can be transmitted in the +Z direction from the second surface opening 202 of the printed wiring board 1. Specifically, when an output terminal of an MMIC (monolithic microwave integrated circuit) that outputs electromagnetic waves such as microwaves or a connection pad electrically connected to the output terminal is disposed near the first surface opening 201, the electromagnetic waves output from the electrode can be guided to the second surface S2 side by the through-hole conductor 20 and transmitted in the +Z direction from the second surface opening 202.

[0012] In addition, electromagnetic waves incident on the second surface opening 202 from above the printed wiring board 1 can be guided to the first surface S1 side by the through-hole conductor 20 and received by being incident on the above-mentioned electrode from the first surface opening 201.

[0013] In this way, the cross-sectional opening area of ​​the through-hole conductor 20 increases toward the second surface S2 side, and thus a waveguide (feedhorn type waveguide) is obtained in which the opening diameter increases as the electromagnetic wave advances in the propagation direction when the electromagnetic wave is radiated from the second surface S2 side. Therefore, inside the through-hole conductor 20, the electromagnetic wave approaches a plane wave as it approaches the second surface S2, so that the electromagnetic wave radiated to the outside from the second surface opening 202 changes to a plane wave more gradually. Also, the opening diameter of the through-hole conductor 20 increases as the electromagnetic wave advances toward the second surface opening 202, so that the electromagnetic wave is less likely to be reflected inside the through-hole conductor 20 compared to a waveguide with a constant opening diameter. As a result, the signal transmission gain is improved compared to a conventional waveguide with a constant opening diameter. Moreover, during reception, the efficiency of convergence of electromagnetic waves entering the through-hole conductor 20 from the second surface opening 202 can be improved.

[0014] Furthermore, because inner wall 203 of through-hole conductor 20 is inclined with respect to the Z direction, an area is formed in which the electromagnetic wave moving from first surface S1 to second surface S2 gradually spreads during transmission. This makes it more difficult for reflection to occur inside through-hole conductor 20, further improving the transmission gain of the signal. Moreover, during reception, the efficiency of convergence of the electromagnetic waves incident on the through-hole conductor 20 from the second surface opening 202 can be further improved.

[0015] In other words, the printed wiring board 1 of the present embodiment is A first insulating layer, a through-hole conductor, and a through hole, the first insulating layer has a first surface and a second surface opposite the first surface; the through-hole conductor is located across the first surface and the second surface, and a portion surrounded by the through-hole conductor is a through hole; The through hole has a portion in which an opening area in a cross section parallel to the second surface increases from the first surface toward the second surface.

[0016] [Variation 1] Next, a first modification of the first embodiment will be described. Printed wiring board 1 according to the first modification differs from the above embodiment in that through-hole conductor 20 has an opening with an aspect ratio of more than 1 in cross section. Below, differences from the first embodiment will be described, and commonalities will not be described. The first modification may be combined with the second to sixth embodiments described later.

[0017] As shown in Fig. 2, in the through-hole conductor 20 of the printed wiring board 1 according to the first modification, the first surface opening 201, the second surface opening 202, and the opening in any cross section are rectangular and similar to each other. The areas of these rectangles increase from the first surface S1 toward the second surface S2. In addition, in any vertical section passing through the central axis of the through hole 111, the inner wall 203 is inclined with respect to the direction perpendicular to the second surface S2 (Z direction). Here, when the opening of the through-hole conductor 20 has a shape other than a circle, the central axis of the through hole 111 can be, for example, an axis passing through the center of gravity of the opening shape in the cross section (the same applies to Figs. 3 to 6 below). The portion of the inner wall 203 that is inclined with respect to the Z direction may be located either in the longitudinal direction (inner wall parallel to the X direction) or in the lateral direction (inner wall parallel to the Y direction) of the through-hole conductor 20. It is particularly preferable that the portion is located on the inner wall in the longitudinal direction.

[0018] The first surface opening 201 has a long side (major axis) with a length a1 and a short side (minor axis) with a length b1. The second surface opening 202 has a long side with a length a2 and a short side with a length b2. The through-hole conductor 20 in FIG. 2 propagates an electromagnetic wave with a wavelength λ that satisfies both λ / 2≦a1≦λ and λ / 2≦a2≦λ.

[0019] With this configuration, the range of electromagnetic wave wavelengths that can pass through can be widened by the amount that the major axis of through-hole conductor 20 is larger than the minor axis. Also, since the minor axis is relatively small, the electromagnetic field of the plane wave propagating through the waveguide tends to be oriented toward the major axis (X direction in FIG. 2), thereby improving the propagation efficiency.

[0020] 3, the cross-section of the opening of through-hole conductor 20 may be rectangular with curved corners 204. That is, corners 204 of the inner wall of through-hole conductor 20 may be curved and concave. According to this configuration, when transmitting and receiving a signal, the magnetic field (magnetic field lines) circulating around the current propagating in the Z direction through the through-hole conductor 20 is less likely to be reflected by the inner wall near the corner 204. This makes it possible to improve the transmission gain of the signal.

[0021] The shape of the opening in the cross section of through-hole conductor 20 is not limited to the rectangle shown in FIGS. 2 and 3, but may be any shape with an aspect ratio of more than 1. For example, as shown in FIG. 4, the through-hole conductor 20 may have an opening with a racetrack shape (an oval shape extending in the X direction) in cross section.

[0022] 5, the through-hole conductor 20 may have a dumbbell-shaped opening in cross section. Here, the dumbbell shape is a shape in which both ends on one side and the other side in the X direction are circular, and the central portion excluding these ends is band-shaped. In other words, the dumbbell shape is a shape in which two circular ends are connected by a band-shaped central portion whose width is narrower than the diameter of the circle.

[0023] 6, the through-hole conductor 20 may have a bowtie-shaped opening in cross section. Here, the bowtie-shaped opening has trapezoidal ends on both sides in the X direction, and a central portion excluding the ends is strip-shaped. The trapezoidal ends have a width in the Y direction that is wider the closer they are to the ends in the X direction.

[0024] The racetrack, dumbbell and bowtie shaped through-hole conductors 20 also provide the same effects as the rectangular through-hole conductors 20 .

[0025] [Modification 2] Next, a second modification of the first embodiment will be described. In the printed wiring board 1 according to the second modification, the cross-sectional shape of the through-hole conductor 20 differs from that of the above embodiment. Below, differences from the first embodiment will be described, and a description of commonalities will be omitted. The second modification may be combined with the first modification. The second modification may also be combined with the second to sixth embodiments described later.

[0026] 7, through-hole conductor 20 of printed wiring board 1 according to modification 2 has portion p1 whose cross-sectional opening area increases toward second surface S2 and portion p2 whose opening area is constant. Portion p1 is a portion of through-hole conductor 20 within a predetermined distance range from first surface S1, and portion p2 is a portion of through-hole conductor 20 excluding portion p1.

[0027] From another point of view, in any longitudinal section passing through the central axis of through hole 111, in portion p1, the opening width in the direction parallel to second surface S2 increases toward second surface S2. On the other hand, in any longitudinal section, in portion p2, the opening width in the direction parallel to second surface S2 is constant.

[0028] From another perspective, in an arbitrary vertical cross section passing through the central axis of through hole 111, in part p1, inner wall 203 is inclined with respect to the direction perpendicular to second surface S2 (Z direction). On the other hand, in an arbitrary cross section, in part p2, the inner wall surface is parallel to the Z direction. Alternatively, the portion p2 with a constant opening area may be located on the first surface S1 side, and the portion p1 with an increasing area may be located on the second surface S2 side.

[0029] In this way, it is sufficient that the through-hole conductor 20 has a portion in which the area of ​​the opening in the cross section increases from the first surface S1 side toward the second surface S2 side, and the area of ​​the opening in the cross section does not monotonically decrease toward the second surface S2.

[0030] 8, through-hole conductor 20 of printed wiring board 1 according to modification 2 may have portion p3 whose cross-sectional opening area decreases toward second surface S2, and portion p1 whose cross-sectional opening area increases toward second surface S2. Portion p3 is a portion of through-hole conductor 20 within a predetermined distance range from first surface S1, and portion p1 is a portion of through-hole conductor 20 excluding portion p3. According to the configuration of FIG. 8, reflection and convergence during transmission and reception can be averaged, so that the difference in signal propagation efficiency during transmission and reception can be reduced.

[0031] Second Embodiment Next, a second embodiment will be described. Printed wiring board 1 according to the second embodiment differs from the first embodiment in that it has a first conductor layer 21. Below, the differences from the first embodiment will be described, and the commonalities will not be described.

[0032] 9, the printed wiring board 1 according to the second embodiment has a first conductor layer 21 on the second surface S2 of the first insulating layer 11. The first conductor layer 21 is electrically connected to the through-hole conductor 20. The first conductor layer 21 is disposed so as to maintain the size of the second surface opening 202 of the through-hole conductor 20. In other words, the first conductor layer 21 is disposed so as not to block the second surface opening 202. The first conductor layer 21 may be provided only on a part of the second surface S2, for example, around the connection portion with the through-hole conductor 20.

[0033] The first conductor layer 21 may be, for example, a plating layer (copper, nickel, gold, or the like) formed by plating, a metal foil such as copper foil, a vapor deposition film, a sputtered film, etc. Among these, from the viewpoints of cost and mass productivity, it is preferable to use a copper plating layer and / or copper foil. The printed wiring board 1 is 1 Surface S 1 The first insulating layer 11 may also have a first conductor layer 21 electrically connected to the through-hole conductor 20. As the first insulating layer 11 having the first conductor layer 21, a printed board with copper foil on one side or copper foil on both sides may be used.

[0034] In this manner, according to the configuration having the first conductor layer 21 on the second surface S2, when an electromagnetic wave is radiated from the second surface S2 side through the through-hole conductor 20 during transmission, the electromagnetic wave (electromagnetic field) spreads along the first conductor layer 21 provided on the second surface S2, as shown by the dashed line in Fig. 9. This makes it possible to change the electromagnetic field radiated from the second surface S2 side through the through-hole conductor 20 into a wider and more stable plane wave. This makes it possible to increase the efficiency of emitting the electromagnetic wave into space. Furthermore, during reception, the efficiency of convergence of the received plane wave can be improved.

[0035] Third embodiment Next, a third embodiment will be described. Printed wiring board 1 according to the third embodiment differs from the second embodiment in that it has organic resin 40, second insulating layer 12, and a plurality of first via conductors 31. Below, the differences from the second embodiment will be described, and the commonalities will be omitted.

[0036] As shown in FIG. 10, the printed wiring board 1 according to the third embodiment includes an organic resin 40 (resin) filling a space surrounded by the through-hole conductor 20, a second insulating layer 12 provided on the first conductor layer 21, and a plurality of via conductors 31 penetrating the second insulating layer 12. Here, the space surrounded by the through-hole conductor 20 refers to a space surrounded by the inner wall of the through-hole conductor 20, the surface formed by the first surface opening 201, and the surface formed by the second surface opening 202. The plurality of via conductors 31 are electrically connected to the first conductor layer 21. In addition, the plurality of via conductors 31 are arranged outside the second surface opening 202 so as to surround the second surface opening 202 in a plan view toward the second surface S2. In FIG. 10, six via conductors 31 are provided to surround the periphery of the second surface opening 202 at equal intervals. The material of the via conductor 31 may be any of the materials exemplified above as the material of the first conductor layer 21, or may be the same as the material of the first conductor layer 21.

[0037] The organic resin 40 filled in the through hole 111 (through-hole conductor 20) is preferably at least one selected from epoxy resin (relative dielectric constant ε: 2.5 to 6.0), polyimide resin (relative dielectric constant ε: 4.8 to 4.9), polyamide resin (relative dielectric constant ε: 3.8 to 4.1), polyphenylene ether resin (relative dielectric constant ε: 2.8 to 2.9), etc. The organic resin 40 may be mixed with an inorganic filler.

[0038] The second insulating layer 12 may preferably be made of a liquid crystal polymer (dielectric constant ε: 3.5 to 3.6), PTFE (polytetrafluoroethylene, dielectric constant ε: 2.1), or cyclic olefin copolymer (dielectric constant: 2.7). In particular, the second insulating layer 12 may have a lower dielectric constant than the organic resin 40. The dielectric constant of the second insulating layer 12 and / or the organic resin 40 may be adjusted by changing the porosity of the second insulating layer 12 and / or the organic resin 40 or the content of the inorganic filler. In particular, an epoxy resin may be used for the organic resin 40, and a liquid crystal polymer may be used for the second insulating layer 12. The second insulating layer 12 may be made of the same material as the organic resin 40.

[0039] In this way, with the configuration having a plurality of via conductors 31, during transmission, after the electromagnetic wave reaches the first conductor layer 21 from the through-hole conductor 20, the spread of the electromagnetic wave as a plane wave is suppressed by the via conductors 31, and the directivity can be increased. Furthermore, during reception, the convergence efficiency of the plane wave can be increased.

[0040] Moreover, by configuring the second insulating layer 12 so that its relative dielectric constant is lower than that of the organic resin 40, the cutoff frequency can be increased during transmission when the electromagnetic waves are radiated from the through-hole conductors 20 toward the first conductor layer 21, so that electromagnetic waves in higher modes can be attenuated more. Furthermore, in the second insulating layer 12, which has a low relative dielectric constant, the wavelength of the electromagnetic waves during emission can be made wider.

[0041] [Fourth embodiment] Next, a fourth embodiment will be described. Printed wiring board 1 according to the fourth embodiment differs from the third embodiment in that it has a second conductor layer 22. Below, the differences from the third embodiment will be described, and the commonalities will not be described.

[0042] As shown in FIG. 11, the printed wiring board 1 according to the fourth embodiment includes a second conductor layer 22 on a second insulating layer 12. The second conductor layer 22 is electrically connected to a plurality of via conductors 31. The second conductor layer 22 has an opening 221 having an area smaller than that of the second surface opening 202 at a position surrounding the central axis 111a of the through hole 111 in a plan view. The shape of the opening 221 may be, for example, a circular shape. The shape of the opening 221 may be similar to the shape of the second surface opening 202. The material of the second conductor layer 22 may be any of the materials exemplified above as the material of the first conductor layer 21, or may be the same as the material of the first conductor layer 21. The second conductor layer 22 and the via conductors 31 may be integral with each other by being formed in a common process such as plating.

[0043] According to this configuration, during transmission, the directivity of the electromagnetic wave radiated in the +Z direction from the through-hole conductor 20 through the opening 221 can be increased by the via conductor 31 and the opening 221 of the second conductor layer 22, while improving the convergence efficiency. During reception, the side lobe portion of the electromagnetic wave can be reduced by passing through the opening 221 of the second conductor layer 22, so that the main lobe of the electromagnetic wave can be introduced into the through-hole conductor 20 with high efficiency. In this case, inside the through-hole conductor 20, the plane wave tends to be oriented in a direction perpendicular to the traveling direction of the electromagnetic wave (a direction parallel to the second surface S2). Also, the electromagnetic wave in a higher mode can be attenuated.

[0044] Fifth embodiment Next, a fifth embodiment will be described. The printed wiring board 1 according to the fifth embodiment corresponds to the printed wiring board 1 according to the fourth embodiment, in which components are added to the upper and lower surfaces thereof. Below, differences from the fourth embodiment will be described, and commonalities will be omitted.

[0045] As shown in FIG. 12, the printed wiring board 1 according to the fifth embodiment has a first conductor layer 21 electrically connected to the through-hole conductor 20 on the first surface S1 (lower surface) of the first insulating layer 11. A third insulating layer 13 is provided on the lower surface of the first conductor layer 21 on the first surface S1, covering the first surface opening 201 of the through-hole conductor 20. A third conductor layer 23 is provided on the upper surface (lower surface) of the third insulating layer 13. The third conductor layer 23 has a plurality of connection pads 231, 232 (connection portions) electrically connected to terminals of the MMIC 50 as an electronic component. Among them, the connection pad 231 is located at a position overlapping the central axis 111a of the through hole 111 in a plan view toward the first surface S1. That is, the position of the connection pad 231 is a position overlapping the central axis 111a. The connection pad 232 is electrically connected to the first conductor layer 21 on the first surface S1 by a via conductor 32 penetrating the third insulating layer 13. A fourth insulating layer 14 is provided on the lower surfaces of the third insulating layer 13 and the third conductor layer 23.

[0046] The material of the third insulating layer 13 and the fourth insulating layer 14 may be any of the materials exemplified above as the material of the second insulating layer 12, or may be the same as the material of the second insulating layer 12. The material of the via conductor 32 and the third conductor layer 23 may be any of the materials exemplified above as the material of the first conductor layer 21, or may be the same as the material of the first conductor layer 21. In addition, the via conductor 32 and the third conductor layer 23 may be integrated by being formed in a common process such as a plating process.

[0047] Further, a fifth insulating layer 15 is provided on the upper surface of the second conductor layer 22 to cover the opening 221 of the second conductor layer 22. A fourth conductor layer 24 is provided on the upper surface of the fifth insulating layer 15 in an area that covers the opening 221 in a plan view. The fourth conductor layer 24 functions as a patch antenna.

[0048] The material of the fifth insulating layer 15 may be any of the materials exemplified above as the material of the second insulating layer 12, or may be the same as the material of the second insulating layer 12. However, it is preferable that the relative dielectric constant of the second insulating layer 12 is lower than the relative dielectric constant of the organic resin 40, and that the relative dielectric constant of the fifth insulating layer 15 is lower than the relative dielectric constant of the second insulating layer 12. In particular, an epoxy resin may be used for the organic resin 40, a liquid crystal polymer may be used for the second insulating layer 12, and PTFE may be used for the fifth insulating layer 15. The material of the fourth conductor layer 24 may be any one of the materials exemplified above as the material of the first conductor layer 21, or may be the same as the material of the first conductor layer 21.

[0049] According to this configuration, the electromagnetic waves (high frequency signals) radiated from the terminals of the MMIC 50 can be guided from the connection pads 231 to the through-hole conductors 20 and transmitted in the +Z direction from the fourth conductor layer 24. Here, since the connection pads 231 are located on the central axis 111a of the through-holes 111, the electromagnetic waves radiated from the terminals of the MMIC 50 can be propagated linearly to the narrow through-hole conductors 20. Therefore, the transmission loss of the electromagnetic waves when they enter the through-hole conductors 20 from the MMIC 50 can be reduced. During reception, the electromagnetic waves passing through the through-hole conductor 20 from the fourth conductor layer 24 acting as a patch antenna can be transmitted to the MMIC 50 with a high convergence rate.

[0050] Sixth embodiment Next, a sixth embodiment will be described. Printed wiring board 1 according to the sixth embodiment differs from the first embodiment in that it has an inner layer conductor 25 inside first insulating layer 11. Below, the differences from the first embodiment will be described, and the commonalities will not be described.

[0051] As shown in FIG. 13, the printed wiring board 1 according to the sixth embodiment includes an inner layer conductor 25 inside the first insulating layer 11. The inner layer conductor 25 is electrically connected to the through-hole conductor 20. The inner layer conductor 25 is a plate-shaped conductor parallel to the second surface S2. The first insulating layer 11 may be configured by laminating a plurality of insulators in the Z direction, and the inner layer conductor 25 may be formed at the interface of any of the plurality of insulators. Furthermore, the inner layer conductor 25 may be provided in a plurality of layers.

[0052] The sixth embodiment may be combined with any of the second to fifth embodiments. That is, printed wiring board 1 of the second to fifth embodiments may have inner layer conductor 25 inside first insulating layer 11.

[0053] With such a configuration having the inner layer conductor 25, it is possible to reduce deformation of the waveguide including the through-hole conductor 20 when the first insulating layer 11 receives a load that may cause bending, etc. This makes it possible to reduce disturbance of the propagating electromagnetic wave, thereby obtaining a stable transmission gain (transmission efficiency).

[0054] [Method for manufacturing printed wiring board] Next, an example of a method for manufacturing printed wiring board 1 will be described with reference to Fig. 14 to Fig. 16. Here, the manufacturing method for printed wiring board 1 according to the fifth embodiment shown in Fig. 12 will be described as an example. The materials of each member listed in the manufacturing method below are examples and are not limited to these.

[0055] First, a printed circuit board is prepared having a first insulating layer 11 and a first conductor layer 21 formed on a first surface S1 and a second surface S2 of the first insulating layer 11. The first insulating layer 11 is, for example, a glass cloth (relative dielectric constant ε: 4.6) impregnated with epoxy resin, and the first conductor layer 21 is a copper foil.

[0056] Next, as shown in Fig. 14, a reamer-type drill, the diameter of which is smaller at the front end than at the rear end, is used to form through holes 111 in the printed circuit board. For shapes with corners such as rectangles, a smaller diameter drill is also used. By using a reamer-type drill, it is possible to form through holes 111 whose opening area increases toward the second surface S2.

[0057] 15, electroless copper plating and electrolytic copper plating are then performed to form through-hole conductors 20 on inner walls 112 of through holes 111. Note that first conductor layer 21 may also be formed in this process.

[0058] Next, as shown in FIG. 16, the space surrounded by the through-hole conductors 20 is filled with organic resin 40 of epoxy resin (relative dielectric constant ε: 4.3). In addition, liquid crystal polymer (relative dielectric constant ε: 3.5 to 3.6) is laid up on the first surface S1 side and the second surface S2 side of the structure filled with organic resin 40, respectively, and the structure in this state is heated and pressed in the Z direction (for example, 200°C, 2 hours). As a result, the liquid crystal polymer is melted once and then hardened, and as shown in FIG. 16, the second insulating layer 12 is formed on the second surface S2 side and the third insulating layer 13 is formed on the first surface S1 side. Thereafter, using a known film formation technique, etc., the via conductor 31, the second conductor layer 22, the fifth insulating layer 15, and the fourth conductor layer 24 are formed on the second surface S2 side, and the via conductor 32, the third conductor layer 23, the fourth insulating layer 14, and the MMIC 50 are formed on the first surface S1 side, completing the printed wiring board 1 shown in FIG. 12.

[0059] The specific details of the configuration, structure, positional relationship, shape, etc. shown in the above embodiment can be appropriately changed without departing from the spirit of the present disclosure. Furthermore, the configuration, structure, positional relationship, and shape shown in the above embodiment can be appropriately combined without departing from the spirit of the present disclosure. [Industrial Applicability]

[0060] The present disclosure can be used in printed wiring boards. [Explanation of symbols]

[0061] 1 Printed wiring board 10 Insulating layer 11 First insulating layer 111 Through hole 111a Center axis 112 Inner wall 12 Second insulating layer 13 Third insulating layer 14 Fourth insulating layer 15 5th insulating layer 20 Through-hole conductor 201 First side opening 202 Second side opening 203 Interior wall 204 Corner 21 First conductor layer 22 Second conductor layer 221 Aperture 23 Third conductor layer 231, 232 Connection pad (connection part) 24 4th conductor layer 25 Inner layer conductor 31, 32 Via conductor 40 Organic resin (resin) 50 MMIC (electronic components) S1 1st page S2 side 2

Claims

1. A first insulating layer having a first surface, a second surface opposite the first surface, and a through hole penetrating from the first surface to the second surface; a through-hole conductor located on an inner wall of the through hole, the through-hole conductor having a portion whose opening area in a cross section parallel to the second surface increases from the first surface side toward the second surface side; a first conductor layer located on the second surface of the first insulating layer and electrically connected to the through-hole conductor; a resin filling a space surrounded by the through-hole conductor; a second insulating layer provided on the first conductor layer; A plurality of via conductors penetrating the second insulating layer; Equipped with the plurality of via conductors are electrically connected to the first conductor layer and are arranged to surround second surface side openings of the through hole conductors on the second surface in a plan view toward the second surface, A printed wiring board, wherein the through-hole conductor is located only on the inner wall of the through hole of the first insulating layer, and is not located in the second insulating layer.

2. The second insulating layer is laminated continuously with the first insulating layer without any other insulating layer between them, the through-hole conductor is located in the first insulating layer and not in the second insulating layer; the plurality of via conductors are located in the second insulating layer and are not located in the first insulating layer; The printed wiring board according to claim 1 .

3. 3 . The printed wiring board according to claim 1 , wherein the through-hole conductor has an opening area that increases from the first surface toward the second surface.

4. 3. The printed wiring board according to claim 1, wherein in any cross section passing through a central axis of the through hole and perpendicular to the second surface, the through-hole conductor has an opening width in a direction parallel to the second surface that increases from the first surface to the second surface.

5. The printed wiring board according to any one of claims 1 to 4, wherein the through-hole conductor has a portion that is inclined with respect to a direction perpendicular to the second surface in any cross section passing through the central axis of the through hole and perpendicular to the second surface.

6. 6. The printed wiring board according to claim 1, wherein the through-hole conductor has an opening with an aspect ratio of greater than 1 in a cross section parallel to the second surface.

7. The printed wiring board according to claim 6 , wherein the through-hole conductor has an opening that has a rectangular, racetrack, dumbbell or bowtie shape in a cross section parallel to the second surface.

8. The printed wiring board according to claim 6 , wherein the through-hole conductor has an opening that has a rectangular shape with curved corners in a cross section parallel to the second surface.

9. 9. The printed wiring board according to claim 1, wherein the second insulating layer has a relative dielectric constant lower than the relative dielectric constant of the resin.

10. a second conductor layer on the second insulating layer; The second conductor layer is electrically connected to the plurality of via conductors. The printed wiring board according to any one of claims 1 to 9, wherein the second conductor layer has an opening having a smaller area than the second surface opening at a position surrounding the central axis of the through hole in the plan view.

11. a third insulating layer covering an opening on the first surface of the through-hole conductor; a third conductor layer provided on the third insulating layer; Equipped with the third conductor layer has a plurality of connection portions electrically connected to electronic components; The printed wiring board according to claim 10 , wherein at least one of the plurality of connection portions is located so as to overlap a central axis of the through hole in a plan view facing the first surface.

12. an inner layer conductor is provided inside the first insulating layer; 12. The printed wiring board according to claim 1, wherein the inner layer conductor is electrically connected to the through-hole conductor.

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