Wiring substrate with inductor function and its manufacturing method

Abstract

[Problem] To provide a wiring board with an inductor structure that has excellent insulation in the planar direction and excellent inductance characteristics by having a magnetic material present not only inside the conductor coil but also outside the conductor coil, and a method for manufacturing the same. [Solution] An inner layer substrate having first and second main surfaces and an opening formed penetrating between the first and second main surfaces, and A magnetic layer formed inside the above-mentioned opening, wherein a first through-hole is formed penetrating the first and second main surfaces thereof, and An insulator formed inside the first through-hole, wherein a second through-hole penetrating the insulator is formed, and An inductor comprising a first conductor pattern formed on a first main surface of the magnetic layer, a second conductor pattern formed on a second main surface of the magnetic layer, and a through-hole conductor formed inside the second through-hole and connecting the first conductor pattern and the second conductor pattern. A wiring board having an inductor function, including

Description

Technology Field

[0001] The present invention relates to a wiring board having an inductor function and a method for manufacturing the same. More specifically, it relates to a wiring board having an inductor structure formed inside and a method for manufacturing the same. Background Technology

[0002] Inductors are widely installed in high-performance electronic devices such as mobile phones, smartphones, and tablet PCs. When inductor components are mounted or embedded in a wiring board, for example, inductor components described in Patent Documents 1 and 2 can be used.

[0003] Recently, as electronic devices have been miniaturized, there is a demand for additional high functionality and miniaturization of the wiring boards used in these small devices. Regarding inductors, there is also anticipation for a technology that incorporates inductor structures directly into the wiring board, rather than using separate inductor components.

[0004] As a technique for creating and incorporating an inductor structure into a wiring board, for example, based on the method for manufacturing an inductor component of Patent Document 2, a method is conceived of using a magnetic sheet as an inner layer substrate and forming a solenoid-shaped conductor pattern on the magnetic sheet to form an inductor structure. In addition, as proposed in Patent Document 3, a method is also conceived of forming an inductor structure by housing a magnetic body in a part of an insulating substrate and forming a solenoid-shaped conductor pattern on the insulating substrate surrounding the magnetic body. Prior art literature

[0005] [Patent Document 1] Japanese Patent Publication No. JP 2016-197624 [Patent Document 2] Japanese Patent Publication No. JP 2014-116465 [Patent Document 3] Japanese Patent Publication No. JP 2016-39256 The problem to be solved

[0006] However, using a magnetic sheet as an inner layer substrate and forming a solenoid-shaped conductor pattern on the magnetic sheet results in insufficient insulation in the planar direction (direction of the main surface of the substrate) and makes it difficult to obtain the desired inductance characteristics.

[0007] Furthermore, in a method of forming a conductor pattern on a solenoid by housing a magnetic material in a portion of an insulating substrate and forming a through-hole conductor in the insulating substrate surrounding the magnetic material, the magnetic material exists inside the conductor pattern (conductor coil) on the solenoid but not outside the conductor coil, making it difficult to obtain the desired inductance characteristics.

[0008] The present invention provides a wiring board with an inductor structure that has excellent insulation in the planar direction and excellent inductance characteristics due to the presence of a magnetic material not only inside the conductor coil but also outside the conductor coil, and a method for manufacturing the same. means of solving the problem

[0009] The present invention includes the following contents.

[0010] [1] An inner layer substrate having first and second main surfaces, with an opening formed between the first and second main surfaces, and

[0011] A magnetic layer formed inside the above-mentioned opening, wherein a first through-hole is formed penetrating the first and second main surfaces thereof, and

[0012] An insulator formed inside the first through-hole, wherein a second through-hole penetrating the insulator is formed, and

[0013] An inductor comprising a first conductor pattern formed on a first main surface of the magnetic layer, a second conductor pattern formed on a second main surface of the magnetic layer, and a through-hole conductor formed inside the second through-hole and connecting the first conductor pattern and the second conductor pattern.

[0014] A wiring board having an inductor function including

[0015] [2] A wiring board described in [1], further comprising an insulating layer formed by bonding to a first main surface of an inner layer substrate and a first main surface of a magnetic layer, wherein a first conductor pattern is formed by bonding to the surface of the insulating layer on the first main surface of the magnetic layer.

[0016] [3] A wiring board described in [1] or [2], further comprising an insulating layer formed by bonding to the second main surface of the inner layer substrate and the second main surface of the magnetic layer, wherein a second conductor pattern is formed by bonding to the surface of the insulating layer on the second main surface of the magnetic layer.

[0017] [4] A wiring board described in [2] or [3] comprising a conductor layer formed by bonding to the surface of an insulating layer on at least one of the first and second main sides of an inner layer substrate.

[0018] [5] A wiring board described in any one of [1] to [4], in which the inner layer substrate is an insulating substrate.

[0019] [6] A wiring board described in any one of [1] to [4], in which the inner layer substrate is a circuit board.

[0020] [7] A method for manufacturing a wiring board having an inductor function, comprising the following processes (A) to (G).

[0021] (A) A process of preparing an inner layer substrate having first and second main surfaces, with an opening formed penetrating between the first and second main surfaces,

[0022] (B) A process of filling the interior of the above opening with a magnetic paste and heat-curing the magnetic paste to form a magnetic layer,

[0023] (C) A process for forming a first through-hole penetrating between the first and second main sides of a magnetic layer,

[0024] (D) A process of forming an insulator inside the first through-hole,

[0025] (E) A process of forming a second through-hole penetrating the insulator,

[0026] (F) A process of forming a through-hole conductor inside the second through-hole, and

[0027] (G) A process of forming a first conductor pattern and a second conductor pattern, respectively, on the first and second main surfaces of a magnetic layer, such that the first conductor pattern and the second conductor pattern are connected to a solenoid by a through-hole conductor.

[0028] [8] The method described in [7], in which the viscosity (25°C) of the magnetic paste is 20 to 250 Pa·s.

[0029] [9] After process (D),

[0030] (D-1) A process of forming an insulating layer by bonding to a first main surface of an inner layer substrate and a first main surface of a magnetic layer, and

[0031] (D-2) A process of forming an insulating layer by bonding to the second main surface of the inner layer substrate and the second main surface of the magnetic layer.

[0032] The method described in [7] or [8], which additionally includes at least one of the

[0033]

[10] In process (E), a second through-hole is formed through the insulating layer and the insulator, as described in [9].

[0034]

[11] The method described in [9] or

[10] further comprising the process of forming a conductive layer on the surface of an insulating layer on at least one of the first and second main sides of an inner layer substrate. Effects of the invention

[0035] According to the present invention, a wiring board having an inductor structure that has excellent insulation in the planar direction and excellent inductance characteristics by having a magnetic material present not only inside the conductor coil but also outside the conductor coil is provided, and a method for manufacturing the same. Brief explanation of the drawing

[0036] FIG. 1 is a schematic plan view showing an inductor structure portion of a wiring board in one embodiment of the present invention. Figure 2 is a schematic diagram (1) for explaining a method of manufacturing one embodiment of the present invention. Figure 3 is a schematic diagram (2) for explaining a method of manufacturing one embodiment of the present invention. Figure 4 is a schematic diagram (3) for explaining a method of manufacturing one embodiment of the present invention. FIG. 5 is a schematic diagram (4) for explaining a method of manufacturing one embodiment of the present invention. FIG. 6 is a schematic diagram (5) for explaining a method of manufacturing one embodiment of the present invention. FIG. 7 is a schematic diagram (6) for explaining a method of manufacturing one embodiment of the present invention. FIG. 8 is a schematic diagram (7) for explaining a method of manufacturing an embodiment of the present invention. FIG. 8 is also a schematic cross-sectional view of a wiring board (100) according to an embodiment of the present invention. FIG. 9 is a schematic diagram (8) for explaining a method of manufacturing one embodiment of the present invention. FIG. 10 is a schematic diagram (9) for explaining a method of manufacturing one embodiment of the present invention. FIG. 11 is a schematic diagram (10) for explaining a method of manufacturing one embodiment of the present invention. FIG. 12 is a schematic diagram (11) for explaining a method of manufacturing an embodiment of the present invention. FIG. 12 is also a schematic cross-sectional view of a wiring board (200) according to an embodiment of the present invention. FIG. 13 is a schematic diagram (12) for explaining a method of manufacturing one embodiment of the present invention. FIG. 14 is a schematic diagram (13) for explaining a method of manufacturing one embodiment of the present invention. FIG. 15 is a schematic diagram (14) for explaining a method of manufacturing an embodiment of the present invention. FIG. 15 is also a schematic cross-sectional view of a wiring board (300) according to an embodiment of the present invention. FIG. 16 is a schematic plan view showing an inductor structure portion of a wiring board in one embodiment of the present invention. Specific details for implementing the invention

[0037] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Furthermore, each drawing merely shows the shape, size, and arrangement of components in a schematic manner to enable an understanding of the invention. The present invention is not limited by the description below, and each component may be appropriately modified within the scope of not departing from the gist of the present invention. In the drawings used for the following description, the same components are indicated by the same reference numerals, and redundant descriptions may be omitted. Furthermore, the configuration according to the embodiments of the present invention cannot be said to be manufactured or used in the arrangement of the illustrated examples.

[0038] [Wiring board with inductor function]

[0039] The wiring board of the present invention has an inductor structure formed and incorporated inside and has an inductor function.

[0040] In the wiring board of the present invention, the inductor structure is characterized by including a through-hole conductor formed inside a through-hole penetrating an insulator as part of a solenoid-shaped conductor pattern (conductor coil). In the wiring board of the present invention, a magnetic layer is also formed around an insulator in the direction of the main surface of the board (i.e., a direction parallel to the main surface of the board), and as a result, a magnetic layer is also present on the outside of the conductor coil. In the wiring board of the present invention, an inner layer substrate is also formed to surround the magnetic layer in the direction of the main surface of the board, and as a result, the magnetic layer exists in a divided region in the direction of the main surface of the board. Furthermore, the conductor pattern forming the conductor coil together with the through-hole conductor is formed inside the region of the magnetic layer when viewed from a direction perpendicular to the main surface of the board, and as a result, when viewed from a direction perpendicular to the main surface of the board, the conductor coil as a whole exists inside the region of the magnetic layer. Since the magnetic layer is provided in a segmented region in the direction of the main surface of the substrate, the wiring board of the present invention has excellent insulation properties in the planar direction. In addition, since a conductor coil is provided within the region of the magnetic layer when viewed from a direction perpendicular to the main surface of the substrate, the wiring board of the present invention has a magnetic material present not only inside the conductor coil but also outside the conductor coil, thereby exhibiting excellent inductance characteristics. Furthermore, in the present invention, regarding the positional relationship between the conductor pattern (conductor coil) on the solenoid and the magnetic material, "inside of the conductor coil" refers to the inside of the tubular structure defined by the conductor coil, and "outside of the conductor coil" refers to the outside of the tubular structure defined by the conductor coil.

[0041] Structural features of the wiring board of the present invention will be explained with reference to FIG. 8 ( FIG. 12 and FIG. 15) and FIG. 1. In addition, details regarding the components shown in each figure will be described later, and it should be noted that this section describes structural features that require particular attention. FIG. 8 is a schematic cross-sectional view of a wiring board (100) according to an embodiment of the present invention. The wiring board (100) shown in FIG. 8 comprises an inner layer substrate (20) having an opening formed therein, a magnetic layer (22) having a first through-hole formed therein as a magnetic layer formed inside the opening, an insulator (24) having a second through-hole formed therein as an insulator formed inside the first through-hole, and a through-hole conductor (26) formed inside the second through-hole, and is characterized by including the through-hole conductor (26) formed inside the second through-hole penetrating the insulator (24) as part of a conductor coil. And the wiring board (100) has a magnetic layer in a divided region (region A in FIG. 8; divided by region B of the inner layer substrate) in the direction of the main surface of the substrate. FIG. 12 and FIG. 15 respectively show schematic cross-sectional views of wiring boards (200 and 300) according to another embodiment of the present invention in which an insulating layer (34) is formed by bonding to both main surfaces of the inner layer substrate (20). However, similar to the wiring board (100) shown in FIG. 8, a through-hole conductor (36, 46) formed inside a second through-hole penetrating the insulator is included as part of a conductor coil, and at the same time, the wiring board has a magnetic layer in a divided region (region A in FIG. 12 and FIG. 15; divided by region B of the inner layer substrate) in the direction of the main surface of the substrate.

[0042] Additionally, FIG. 1 is a schematic plan view showing an inductor structure part (10) of a wiring board according to one embodiment of the present invention (i.e., an inductor structure part (10) made and inserted into the wiring board). Symbols A and B in FIG. 1 correspond to regions A and B shown in FIG. 8 ( FIG. 12 and FIG. 15). Also, the cross-section when the wiring board is cut at the position indicated by the dotted line X1-X1 in FIG. 1 corresponds to the schematic cross-sectional view of FIG. 8 ( FIG. 12 and FIG. 15). The inductor structure (10) shown in FIG. 1 has a solenoid-shaped conductor pattern (conductor coil) composed of a first conductor pattern ("28," "38," and "48" in FIG. 8, FIG. 12, and FIG. 15) consisting of a through-hole land (28a) and a connection pattern (28b), a second conductor pattern ("29," "39," and "49" in FIG. 8, FIG. 12, and FIG. 15) consisting of a through-hole land (29a) (not shown in FIG. 1) and a connection pattern (29b), and a through-hole conductor ("26," "36," and "46" in FIG. 8, FIG. 12, and FIG. 15) within region A of the magnetic layer. As described above, the through-hole conductor is formed inside a second through-hole penetrating the insulator. As can be seen from FIG. 1, in the inductor structure (10), a magnetic material exists not only on the inner side of the conductor coil but also on the outer side of the conductor coil. Although the coil axis of the conductor coil shown in FIG. 1 extends in the vertical direction of FIG. 1, please note that a magnetic material exists in the axial outer region of the tube structure defined by the conductor coil and also in the lateral outer region.

[0043] In the present invention, a wiring board having the above structural features is realized by a novel method of forming an opening (first opening) in an inner layer substrate, forming a magnetic layer inside the first opening, forming a through hole (second opening) in the magnetic layer, forming an insulator inside the second opening, and also forming a through hole (third opening) in the insulator and forming a through hole conductor to form a desired conductor coil.

[0044] In one embodiment, the wiring substrate of the present invention is

[0045] An inner layer substrate having first and second main surfaces, with an opening formed penetrating between the first and second main surfaces, and

[0046] A magnetic layer formed inside the above-mentioned opening, wherein a first through-hole is formed penetrating the first and second main surfaces thereof, and

[0047] An insulator formed inside the first through-hole, wherein a second through-hole penetrating the insulator is formed, and

[0048] It includes an inductor comprising a first conductor pattern formed on a first main surface of the magnetic layer, a second conductor pattern formed on a second main surface of the magnetic layer, and a through-hole conductor formed inside the second through-hole and connecting the first conductor pattern and the second conductor pattern.

[0049] Hereinafter, embodiments of the wiring board of the present invention will be described with appropriate reference to drawings including FIGS. 8, 12, and 15. In addition, the details of each component constituting the wiring board can be understood more clearly by also considering the description in the [Method for manufacturing a wiring board having an inductor structure] section described later.

[0050] For convenience, in the following description, the first main surface of the inner layer substrate or magnetic layer is to represent the upper main surface of the inner layer substrate or magnetic layer illustrated, and the second main surface of the inner layer substrate or magnetic layer is to represent the lower main surface of the inner layer substrate or magnetic layer illustrated. Additionally, "the first (second) main surface of the magnetic layer" refers to the main surface within the region of the magnetic layer (region A in FIG. 1, FIG. 8, etc.), and "the first (second) main surface of the inner layer substrate" refers to the main surface within the region of the inner layer substrate (region B in FIG. 1, FIG. 8, etc.).

[0051] -Inner layer substrate-

[0052] In the wiring board of the present invention, as the inner layer substrate, a known inner layer substrate that can be used when manufacturing a wiring board may be used, and an insulating substrate or a circuit board may also be used.

[0053] An insulating substrate refers to a plate-shaped substrate having opposing first and second main surfaces and exhibiting electrical insulation properties. Examples of insulating substrates include glass epoxy substrates, polyester substrates, polyimide substrates, BT resin substrates, thermosetting polyphenylene ether substrates, glass substrates, ceramic substrates, etc. Cured prepreg may also be used as an insulating substrate. Cured prepreg refers to a cured product of prepreg. A prepreg is a sheet-like material comprising a thermosetting resin composition and a sheet-like fiber substrate, and can be formed, for example, by impregnating a thermosetting resin composition into a sheet-like fiber substrate.

[0054] A circuit board refers to a plate-shaped substrate having opposing first and second main surfaces and having patterned circuit wiring (interlayer wiring such as via wiring, through-hole wiring, and surface wiring, etc.; not shown in the drawings of this specification) on one or both of the first and second main surfaces. An inner layer circuit board of an intermediate product to which an insulating layer and / or a conductive layer must be additionally formed when manufacturing a wiring board is also included in the term "circuit board" as used in the present invention. The substrate (base substrate) used for the circuit board may be the insulating substrate mentioned above.

[0055] The thickness of the inner layer substrate is not particularly limited and may be determined according to the specific design of the wiring board being manufactured. For example, from the perspective of thinning the wiring board, the thickness of the inner layer substrate is preferably 2 mm or less, more preferably 1.5 mm or less, even more preferably 1.2 mm or less, 1.0 mm or less, or 0.8 mm or less. The lower limit of the thickness of the inner layer substrate is not particularly limited, but is preferably 50 μm or more, more preferably 60 μm or more, 80 μm or more, or 100 μm or more. When a circuit board is used as the inner layer substrate, it is suitable for the thickness of the base substrate of the circuit board to be within the above range.

[0056] When a circuit board is used as an inner layer substrate, the dimensions of the circuit wiring provided by the circuit board may be determined according to the specific design of the wiring board being manufactured. For example, the thickness of the surface wiring is preferably 40 μm or less, more preferably 35 μm or less, 30 μm or less, or 25 μm or less from the perspective of thinning the wiring board. The lower limit of the thickness of the surface wiring is not particularly limited, but is typically 1 μm or more, 3 μm or more, 5 μm or more, etc.

[0057] An opening (first opening) penetrating the first and second main surfaces is formed in the inner layer substrate (in FIG. 8, FIG. 12, and FIG. 15, region A corresponds to the opening of the inner layer substrate (20). The shape of the opening is not particularly limited and may be any shape, such as a rectangle, a circle, a roughly rectangle, or a roughly circle. In addition, the dimensions of the opening depend on the design of the inductor structure part, but for example, if the shape of the opening is rectangular, it is preferable to have a diameter of 5mm × 5mm or less, and more preferable to have a diameter of 3mm × 3mm or less, or 2mm × 2mm or less. In addition, if the shape of the opening is circular, it is preferable to have a diameter of 5mm or less, and more preferable to have a diameter of 3mm or less, or 2mm or less. The lower limit of the dimensions of the above opening depends on the dimensions of the inductor structure to be made, but in the case of a rectangular opening, it is usually acceptable to have a diameter of 0.5mm × 0.5mm or more, and in the case of a circular opening, it is usually acceptable to have a diameter of 0.5mm or more. When a circuit board is used as the inner layer substrate, the opening is formed in an area of ​​the circuit board where circuit wiring is not formed.

[0058] FIGS. 8, FIGS. 12, and FIGS. 15 show an inner layer substrate (20) having only one opening, but multiple openings may be formed at a predetermined interval from each other. When the inner layer substrate has multiple openings, their shapes and dimensions may be the same or different.

[0059] -Magnetic layer-

[0060] The wiring substrate of the present invention has a magnetic layer (22) formed inside an opening of an inner layer substrate (20).

[0061] The magnetic layer (22) is formed inside the opening of the inner layer substrate (20) such that, in a direction perpendicular to the main surface of the substrate (the thickness direction of the substrate), its first and second main surfaces correspond substantially to the first and second main surfaces of the inner layer substrate (20), respectively. That is, the magnetic layer is formed with a thickness substantially equal to that of the inner layer substrate, without protruding or being recessed from the inner layer substrate. The magnetic layer (22) is also formed by bonding with the inner layer substrate (20) inside the opening of the inner layer substrate (20).

[0062] The magnetic layer (22) is a layer made of a magnetic material, and its composition is not particularly limited. For example, the magnetic layer may be a cured layer obtained by curing a magnetic composition (also called "magnetic paste") containing magnetic powder and binder resin. Details of the magnetic paste will be explained in the section [Method for manufacturing a wiring board having an inductor function] described later.

[0063] The magnetic layer (22) has a first through-hole penetrating its first and second main surfaces. The first through-hole is also referred to as the "second opening" in relation to the opening (first opening) of the inner layer substrate (20).

[0064] In order to realize the desired conductor coil, the first through-holes are formed in the magnetic layer (22). For example, when the number of turns N of the conductor coil is 1, it is preferable to form 4 through-holes as shown in FIG. 1, and when the number of turns N is 2, it is preferable to form 6 through-holes as shown in FIG. 16. The number of first through-holes may be appropriately determined according to the desired design of the conductor coil. Also, please note that the schematic cross-sectional views shown in FIG. 8, FIG. 12, and FIG. 15 correspond to the cross-section when the wiring board is cut at the position indicated by the dotted line X1-X1 in FIG. 1, and that only 2 first through-holes are shown.

[0065] The shape of the first through-hole is not particularly limited and may be any shape such as rectangular, circular, approximately rectangular, or approximately circular. In addition, the dimensions of the first through-hole (second opening) and the pitch between the first through-holes are not particularly limited as long as the desired conductor coil design can be achieved in relation to the dimensions of the first opening.

[0066] From the perspective of realizing a wiring board with even better inductance characteristics, it is desirable to consider a through structure defined by a conductor pattern (conductor coil) on a solenoid and to determine the position of the first through hole so that a sufficient magnetic material exists in both the axial outer region and the lateral outer region. For example, when the diameter of the first through hole is denoted as D1, it is preferable that the distance between the center position of the first through hole and the inner layer substrate in the through axis direction of the conductor coil (up-down direction in FIG. 1 and FIG. 16) be 0.7D1 or greater, and more preferable that it be 0.8D1 or greater, 0.9D1 or greater, or D1 or greater. In addition, in the direction of the conductor coil's through-side (a direction perpendicular to the through-axis direction of the conductor coil; the left-right direction in FIG. 1 and FIG. 16), it is preferable that the distance between the center position of the first through-hole and the inner layer substrate is 0.7D1 or greater, and more preferable that it is 0.8D1 or greater, 0.9D1 or greater, or D1 or greater.

[0067] -Insulator-

[0068] The wiring board of the present invention has an insulator (24) formed inside the first through-hole of the magnetic layer (22).

[0069] It is preferable that the insulator (24) be formed inside the first through-hole of the magnetic layer (22) such that, in a direction perpendicular to the main surface of the substrate (the thickness direction of the substrate), its first and second main surfaces correspond substantially to the first and second main surfaces of the magnetic layer (22) (and the inner layer substrate (20)), respectively. That is, it is preferable that the insulator be formed with a thickness substantially equal to that of the magnetic layer, without protruding or being recessed from the magnetic layer. The insulator (24) is also formed by being bonded to the magnetic layer (22) inside the first through-hole of the magnetic layer. In addition, in the wiring board of FIG. 12 and FIG. 15 according to an embodiment in which an insulating layer (34) is formed by bonding to both main surfaces of an inner layer substrate (20), the insulating member derived from the insulator (24) formed in the first through-hole of the magnetic layer (22) and the insulating layer (34) are not distinguished, but as described later, the composition of the insulator (24) and the composition of the insulating layer (34) may be the same or different from each other.

[0070] The composition of the insulator (24) is not particularly limited as long as it exhibits electrical insulation properties. For example, the insulator may be a cured layer obtained by curing a resin composition (also called "insulating hole filling paste") containing an insulating resin. Details of the insulating hole filling paste will be explained in the section [Method for manufacturing a wiring board having an inductor function] described later.

[0071] The second through-hole is formed in the insulator (24) formed in the first through-hole of the magnetic layer (22). Accordingly, the number of the second through-hole may be equal to the number of the first through-hole. For example, when the number of turns N of the conductor coil is 1, as shown in FIG. 1, it is preferable to form four first through-holes, form an insulator in each of them, and form a second through-hole. When the number of turns N is 2, as shown in FIG. 16, it is preferable to form six first through-holes, form an insulator in each of them, and form a second through-hole. Also, please note that the schematic cross-sectional view shown in FIG. 8, FIG. 12, and FIG. 15 corresponds to the cross-section when the wiring board is cut at the position indicated by the dotted line X1-X1 in FIG. 1, and that only two second through-holes are shown.

[0072] The shape of the second through-hole is not particularly limited and may be any shape, such as rectangular, circular, approximately rectangular, or approximately circular. In addition, the dimensions of the second through-hole and the pitch between the second through-holes are not particularly limited as long as the desired conductor coil design can be achieved in relation to the dimensions of the first opening. For example, when the diameter of the first through-hole is D1, the diameter D2 of the second through-hole is preferably 0.8D1 or less, more preferably 0.7D1 or less, 0.6D1 or less, or 0.5D1 or less, and preferably 0.2D1 or more, more preferably 0.3D1 or more. If the diameter D2 of the second through-hole is within this range, the insulator surrounding the through-hole conductor has sufficient thickness, and a wiring board with even better inductance characteristics can be realized. In addition, it is suitable to determine the position of the second through-hole so that the pitch between the second through-holes is substantially the same as the pitch between the first through-holes.

[0073] In the present invention, a first through-hole is formed in a magnetic layer, an insulator is formed inside the first through-hole, and additionally, a second through-hole is formed in the insulator and a through-hole conductor is formed to form a solenoid-shaped conductor pattern (conductor coil), thereby realizing a wiring board having the aforementioned structural features.

[0074] -Inductor-

[0075] The wiring board of the present invention comprises a first conductor pattern (28, 38, 48) formed on a first main surface of a magnetic layer (22), a second conductor pattern (29, 39, 49) formed on a second main surface of the magnetic layer (22), and an inductor comprising a through-hole conductor (26, 36, 46) formed inside a second through-hole and connecting the first conductor pattern and the second conductor pattern.

[0076] In the present invention, the statement that the first conductor pattern is "formed on the first main surface of the magnetic layer" includes cases where the first conductor pattern is formed by bonding to the first main surface of the magnetic layer (directly), as well as cases where the first conductor pattern is formed by interposing another layer on the first main surface of the magnetic layer. The same applies to the statement that the second conductor pattern is "formed on the second main surface of the magnetic layer," and includes cases where the second conductor pattern is formed by interposing to the second main surface of the magnetic layer (directly), as well as cases where the second conductor pattern is formed by interposing another layer on the second main surface of the magnetic layer. Here, the other layer is not particularly limited as long as it does not impede the effects of the present invention, and, for example, an insulating layer may be used. Accordingly, in one embodiment, the wiring substrate of the present invention further comprises an insulating layer (34) formed by bonding to the first main surface of the inner layer substrate (20) and the first main surface of the magnetic layer (22), and a first conductor pattern (38, 48) is formed by bonding to the surface of the insulating layer (34) on the first main surface of the magnetic layer (22). In another embodiment, the wiring substrate of the present invention further comprises an insulating layer (34) formed by bonding to the second main surface of the inner layer substrate (20) and the second main surface of the magnetic layer (22), and a second conductor pattern (39, 49) is formed by bonding to the surface of the insulating layer (34) on the second main surface of the magnetic layer (22).

[0077] In the wiring board (100) shown in FIG. 8, a first conductor pattern (28) and a second conductor pattern (29) are formed by bonding to the first main surface and the second main surface of the magnetic layer (22), respectively. On the other hand, in the wiring boards (200, 300) shown in FIG. 12 and FIG. 15, the first conductor pattern (38, 48) is formed by bonding to the surface of the insulating layer (34) on the first main surface of the magnetic layer (22), and the second conductor pattern (39, 49) is formed by bonding to the surface of the insulating layer (34) on the second main surface of the magnetic layer (22).

[0078] The first conductor pattern and the second conductor pattern are connected by a through-hole conductor formed inside the second through-hole of the insulator, forming a conductor pattern (conductor coil) on a solenoid. By doing so, an inductor function is manifested.

[0079] The structure of the first conductor pattern is not limited as long as it can form a conductor coil together with the through-hole conductor and the second conductor pattern. For example, the first conductor pattern may consist of a through-hole land (28a) and a connection pattern (28b) connecting the through-hole lands to each other (Fig. 1). The second conductor pattern is likewise composed of, for example, a through-hole land (29a) and a connection pattern (29b) connecting the through-hole lands to each other (Fig. 1; through-hole land (29a) is not shown).

[0080] The structure of the through-hole conductor is not limited as long as it can form a conductor coil together with the first conductor pattern and the second conductor pattern. For example, the through-hole conductor may be a hollow cylindrical conductor (conformal through-hole conductor) formed by plating on the through-hole wall, or a cylindrical conductor (field through-hole conductor) with the inside of the through-hole filled with a conductor. If the through-hole conductor is a conformal through-hole conductor, the inside of the hollow cylindrical conductor may be filled with an insulator (27, 37, 47).

[0081] - Other Structures -

[0082] In the case where the wiring substrate of the present invention has an insulating layer (34) formed by bonding to at least one of the first and second main surfaces of an inner layer substrate (20) (Figs. 12 and 15), it may include a conductor layer (wiring layer; not shown) formed by bonding to the surface of the insulating layer.

[0083] The wiring board of the present invention may form a multilayer wiring by alternately forming an insulating layer and a conductor layer (wiring layer) on at least one of the first and second main surfaces of an inner layer substrate (20) (and a magnetic layer (22)). Regarding the specific design of the insulating layer, the wiring layer, and the multilayer wiring, known layer configurations or designs may be used when manufacturing the wiring board. For example, by using the wiring board shown in FIGS. 8, FIGS. 12, and FIGS. 15 as an inner layer circuit board and alternately forming an insulating layer and a conductor layer on the inner layer circuit board, it is possible to manufacture a wiring board having a multilayer wiring in which an inductor structure is formed.

[0084] Various types of semiconductor devices can be manufactured using the wiring board of the present invention. Semiconductor devices including such a wiring board can be suitably used in electrical products (e.g., computers, mobile phones, digital cameras, and televisions) and vehicles (e.g., motorcycles, automobiles, trams, ships, and aircraft).

[0085] [Method for manufacturing a wiring board having an inductor function]

[0086] The present invention also provides a novel method for manufacturing a wiring board having an inductor function.

[0087] The method of the present invention is,

[0088] Preparing an inner layer substrate with an opening formed therein,

[0089] Forming a magnetic layer inside the above opening,

[0090] Forming a first through hole in the above magnetic layer,

[0091] Forming an insulator inside the first through-hole,

[0092] Forming a second through-hole in the above-mentioned insulator and

[0093] It also includes forming a conductor pattern on both main surfaces of the magnetic layer and connecting through-hole conductors inside the second through-hole to form a solenoid-shaped conductor pattern. By doing so, it is possible to realize a wiring board having the aforementioned structural features, which have a magnetic layer in a segmented region in the direction of the main surface of the substrate and a solenoid-shaped conductor pattern (conductor coil) inside the region of the magnetic layer when viewed from a direction perpendicular to the main surface of the substrate.

[0094] Hereinafter, based on an embodiment for manufacturing a wiring board shown in FIGS. 8, 12, and 15, it will be described in detail with reference to the drawings.

[0095] In one embodiment, the method for manufacturing a wiring board having an inductor function according to the present invention comprises the following processes (A) to (G).

[0096] (A) A process of preparing an inner layer substrate having first and second main surfaces, with an opening formed penetrating between the first and second main surfaces,

[0097] (B) A process of filling the interior of the above opening with a magnetic paste and heat-curing the magnetic paste to form a magnetic layer,

[0098] (C) A process for forming a first through-hole penetrating between the first and second main sides of a magnetic layer,

[0099] (D) A process of forming an insulator inside the first through-hole,

[0100] (E) A process of forming a second through-hole penetrating the insulator,

[0101] (F) A process of forming a through-hole conductor inside the second through-hole, and

[0102] (G) A process of forming a first conductor pattern and a second conductor pattern, respectively, on the first and second main surfaces of a magnetic layer, such that the first conductor pattern and the second conductor pattern are connected to a solenoid by a through-hole conductor.

[0103] -Process (A)-

[0104] In process (A), an inner layer substrate is prepared having a first main surface and a second main surface, and an opening formed between the first and second main surfaces.

[0105] First, an inner layer substrate is prepared (Fig. 2). The inner layer substrate (20) has a first main surface (20a) and a second main surface (20b). The inner layer substrate (20) may be a known inner layer substrate that can be used when manufacturing a wiring board, or it may be an insulating substrate or a circuit board. The details of the inner layer substrate (20) are as described above. In addition, if the inner layer substrate (20) is a circuit board, it is not shown, but it should be noted that patterned circuit wiring (interlayer wiring such as via wiring, through-hole wiring, and surface wiring, etc.) is provided on one or both of the first and second main surfaces.

[0106] Secondly, an opening is formed in the inner layer substrate that penetrates between the first and second main surfaces (Fig. 3). As schematically shown in Fig. 3, an opening (21) that penetrates between the first and second main surfaces of the inner layer substrate can be formed at a predetermined location on the inner layer substrate (20). If the inner layer substrate (20) is a circuit board, it is preferable to form the opening (21) in an area of ​​the base substrate that does not have circuit wiring. The opening (21) can be formed by a known method, for example, using a drill, laser, plasma, etching medium, etc., taking into account the characteristics of the inner layer substrate (20) and the dimensions of the opening (21). In addition, the shape and dimensions of the opening (21) are as described above.

[0107] Although only one opening (21) is shown in FIG. 3, multiple openings (21) can be formed with a predetermined spacing between them. By forming multiple openings (21), it is possible to create and insert multiple inductor structures into the wiring board.

[0108] -Process (B)-

[0109] In process (B), a magnetic paste is filled into the interior of the opening, and the magnetic paste is heat-cured to form a magnetic layer.

[0110] The magnetic paste comprises (a) magnetic powder and (b) binder resin, and, if necessary, may additionally comprise (c) a dispersant, (d) a curing accelerator, and (e) other additives.

[0111] (a) Magnetic powder

[0112] As a magnetic powder, for example, pure iron powder; Mg-Zn ferrite, Fe-Mn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Cu-Zn ferrite, Mg-Mn-Sr ferrite, Ni-Zn ferrite, Ba-Zn ferrite, Ba-Mg ferrite, Ba-Ni ferrite, Ba-Co ferrite, Ba-Ni-Co ferrite, Y ferrite, iron oxide (III), iron oxide such as tri-iron tetraoxide; Examples include iron alloy-based metal powders such as Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy powder, Fe-Ni-Cr alloy powder, Fe-Cr-Al alloy powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, or Fe-Ni-Co alloy powder; and amorphous alloys such as Co-based amorphous.

[0113] Among these, the magnetic powder is preferably at least one selected from iron oxide powder and iron alloy metal powder. As the iron oxide powder, it is preferable to include ferrite containing at least one selected from Ni, Cu, Mn, and Zn. In addition, as the iron alloy metal powder, it is preferable to include iron alloy metal powder containing at least one selected from Si, Cr, Al, Ni, and Co.

[0114] As the magnetic powder, commercially available magnetic powders may be used. Specific examples of commercially available magnetic powders include "M05S" manufactured by Powdertec; "PST-S" manufactured by Sanyo Tokushu Seko; "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", "Fe-80Ni-4MoPF20F" manufactured by Epson Atomics; and "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", "KNI-109GS" manufactured by JFE Chemicals. Examples include "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", "S-2430" manufactured by Toda Kogyo Co., Ltd.; "JR09P2" manufactured by Nippon Chukagaku Kogyo Co., Ltd.; "Nanotek" manufactured by CIK Nanotech Co., Ltd.; "JEMK-S", "JEMK-H" manufactured by Kinsei Ematec Co., Ltd.; and "Yttrium iron oxide" manufactured by ALDRICH Co., Ltd. The magnetic powder may be used as a single type or in combination of two or more types.

[0115] It is preferable that the magnetic powder be spherical in shape. The value obtained by dividing the length of the major axis of the magnetic powder by the length of the minor axis (aspect ratio) is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. In general, it is easier to improve the relative permeability if the magnetic powder is flat rather than spherical. However, it is particularly preferable to use spherical magnetic powder, as this allows for lower magnetic loss and is also preferable from the perspective of obtaining a paste with desirable viscosity.

[0116] The average particle diameter of the magnetic powder is preferably 0.01 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, in terms of improving relative permeability. In addition, it is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less.

[0117] The average particle diameter of magnetic powder can be measured by a laser diffraction scattering method based on the Mie scattering theory. Specifically, the average particle diameter can be measured by creating a particle diameter distribution of magnetic powder on a volume basis using a laser diffraction scattering type particle diameter distribution measuring device and taking the central diameter as the average particle diameter. Preferably, the measurement sample can be a magnetic powder dispersed in water by ultrasound. As a laser diffraction scattering type particle diameter distribution measuring device, the "LA-500" manufactured by Horiba Sesakusho Co., Ltd. and the "SALD-2200" manufactured by Shimadzu Sesakusho Co., Ltd. can be used.

[0118] The specific surface area of ​​the magnetic powder is preferably 0.05 m² / g or more, more preferably 0.1 m² / g or more, and even more preferably 0.3 m² / g or more, in terms of improving relative permeability. In addition, it is preferably 10 m² / g or less, more preferably 8 m² / g or less, and even more preferably 5 m² / g or less. The specific surface area of ​​the magnetic powder can be measured by the BET method.

[0119] The content (volume%) of the magnetic powder is preferably 40 volume% or more, more preferably 50 volume% or more, and even more preferably 60 volume% or more, when the non-volatile component in the magnetic paste is defined as 100 volume%, in order to improve relative permeability and reduce the loss factor. The upper limit of the above content (volume%) is not particularly limited, but preferably can be 95 volume% or less, 90 volume% or less, etc.

[0120] The content (mass%) of the magnetic powder is preferably 70 mass% or more, more preferably 75 mass% or more, and even more preferably 80 mass% or more, when the non-volatile component in the resin composition is defined as 100 mass%, in order to improve relative permeability and reduce the loss factor. The upper limit of the above content (mass%) is not particularly limited, but preferably can be 99 mass% or less, 98 mass% or less, etc.

[0121] (b) Binder resin

[0122] The binder resin is not particularly limited as long as it is a resin capable of dispersing and bonding magnetic powder in a magnetic paste to form a magnetic layer.

[0123] Examples of binder resins include thermosetting resins such as epoxy resin, phenolic resin, naphthol resin, benzoxazine resin, active ester resin, cyanate ester resin, carbodiimide resin, amine resin, and acid anhydride resin; and thermoplastic resins such as phenoxy resin, acrylic resin, polyvinyl acetal resin, butyral resin, polyimide resin, polyamideimide resin, polyethersulfone resin, and polysulfone resin. As for the binder resin, it is preferable to use a thermosetting resin used when forming an insulating layer of a wiring board, and among these, epoxy resin is preferred. The binder resin may be used as a single type or in combination of two or more types.

[0124] Here, components that react with epoxy resin to cure magnetic paste, such as phenolic resin, naphthol resin, benzoxazine resin, active ester resin, cyanate ester resin, carbodiimide resin, amine resin, and acid anhydride resin, are collectively referred to as "curing agents."

[0125] The epoxy equivalent of the epoxy resin is preferably 50 g / eq. to 5000 g / eq., more preferably 50 g / eq. to 3000 g / eq., even more preferably 80 g / eq. to 2000 g / eq., and even more preferably 110 g / eq. to 1000 g / eq. By being within this range, the crosslinking density of the cured product becomes sufficient, allowing for the formation of a magnetic layer with low surface roughness. Additionally, the epoxy equivalent can be measured according to JIS K7236 and is the mass of a resin containing 1 equivalent of an epoxy group.

[0126] The weight average molecular weight of the epoxy resin is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. Here, the weight average molecular weight of the epoxy resin is the weight average molecular weight in polystyrene equivalent measured by gel permeation chromatography (GPC).

[0127] When epoxy resin and a curing agent are included as binder resins, the ratio of the epoxy resin to all curing agents is [total number of epoxy groups of the epoxy resin] : [total number of reactive groups of the curing agent], preferably in the range of 1:0.01 to 1:5, more preferably in the range of 1:0.5 to 1:3, and even more preferably in the range of 1:1 to 1:2. Here, "number of epoxy groups of the epoxy resin" refers to the sum of the values ​​obtained by dividing the mass of the non-volatile components of the epoxy resin present in the magnetic paste by the epoxy equivalent. Also, "number of active groups of the curing agent" refers to the sum of the values ​​obtained by dividing the mass of the non-volatile components of the curing agent present in the magnetic paste by the active group equivalent.

[0128] The content of the binder resin is preferably 1 mass% or more, 3 mass% or more, or 5 mass% or more, when the non-volatile component in the magnetic paste is defined as 100 mass%, in order to disperse and bind magnetic powder in the magnetic paste to form a magnetic layer. The upper limit is not particularly limited as long as the effects of the present invention are observed, but is preferably 25 mass% or less, 20 mass% or less, or 15 mass% or less.

[0129] (c) Dispersant

[0130] The magnetic paste may additionally contain a dispersant. By using a dispersant, the dispersibility of the magnetic powder can be improved.

[0131] Examples of dispersants include phosphate ester-based dispersants such as polyoxyethylene alkyl ether phosphoric acid; anionic dispersants such as sodium dodecylbenzenesulfonate, sodium laurylate, and ammonium salts of polyoxyethylene alkyl ether sulfate; and nonionic dispersants such as organosiloxane-based dispersants, acetylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, and polyoxyethylene alkylamide. Among these, anionic dispersants are preferred. One type of dispersant may be used alone, or two or more types may be used in combination.

[0132] The content of the dispersant is preferably 0.1 mass% or more, 0.2 mass% or more, or 0.4 mass% or more when the non-volatile component in the magnetic paste is 100 mass%, and the upper limit is preferably 5 mass% or less, 3 mass% or less, or 1 mass% or less.

[0133] (d) Curing accelerator

[0134] The magnetic paste may additionally contain a curing accelerator. By using a curing accelerator, the curing of the binder resin can be effectively promoted, thereby increasing the mechanical strength of the cured product. Examples of curing accelerators include amine-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. Regarding the curing accelerator, amine-based curing accelerators and imidazole-based curing accelerators are preferred, and imidazole-based curing accelerators are more preferred. The curing accelerator may be used alone or in combination of two or more types.

[0135] The content of the curing accelerator is preferably 0.1 mass% or more, 0.2 mass% or more, or 0.3 mass% or more, when the non-volatile component in the magnetic paste is 100 mass%, in order to obtain a magnetic paste exhibiting suitable viscosity. The upper limit is preferably 3 mass% or less, 2 mass% or less, or 1 mass% or less.

[0136] (e) Other additives

[0137] The magnetic paste may also contain other additives as needed. Examples of such other additives include, for instance, curing retardants such as triethyl borate, flame retardants, thickeners, defoaming agents, inorganic fillers (excluding magnetic powders), leveling agents, adhesion promoters, and resin additives such as coloring agents.

[0138] In terms of being able to sufficiently fill the opening of the inner layer substrate (and further form a desired magnetic layer), the viscosity (25°C) of the magnetic paste is preferably 20 Pa·s or more, more preferably 30 Pa·s or more, even more preferably 40 Pa·s or more, and typically 250 Pa·s or less, preferably 220 Pa·s or less, and more preferably 200 Pa·s or less. The viscosity can be measured by maintaining the temperature of the magnetic paste at 25 ± 2°C and using an E-type viscometer.

[0139] Filling the openings of the inner layer substrate with magnetic paste can be performed using methods such as filling the openings with magnetic paste through a squeegee, filling the openings with magnetic paste through a cartridge, filling the openings with magnetic paste by mask printing, roll coating, or inkjet methods. From the perspective of being able to fill without including voids, it is suitable to perform the filling of the magnetic paste under reduced pressure and in a vacuum state.

[0140] After filling the opening of the inner layer substrate with magnetic paste, the magnetic paste is heat-cured to form a magnetic layer. The heat-curing conditions of the magnetic paste vary depending on the composition or type of the magnetic paste, but the curing temperature is preferably 120°C or higher, more preferably 130°C or higher or 140°C or higher, and preferably 240°C or lower, more preferably 220°C or lower or 200°C or lower. The curing time is preferably 5 minutes or more, more preferably 10 minutes or more or 15 minutes or more, and preferably 120 minutes or less, more preferably 100 minutes or less or 90 minutes or less.

[0141] Before heat-curing the magnetic paste, a preheating treatment may be performed on the magnetic paste by heating it to a temperature lower than the curing temperature. For example, prior to heat-curing the magnetic paste, the magnetic paste may be preheated for at least 5 minutes (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes) at a temperature typically between 50°C and 150°C (preferably 60°C to 140°C, more preferably 70°C to 130°C).

[0142] In this way, a magnetic layer (22) is formed in the opening (21) of the inner layer substrate (20) (Fig. 4). Furthermore, it is suitable to remove the excess magnetic layer (22) protruding or attached to the inner layer substrate (20) by polishing and to flatten and smooth the magnetic layer (22) so that the magnetic layer (22) protrudes from the inner layer substrate (20). Thus, as schematically shown in Fig. 4, the magnetic layer (22) can be formed inside the opening (21) of the inner layer substrate (20) such that, in a direction perpendicular to the main surface of the substrate (the thickness direction of the substrate), the first and second main surfaces correspond substantially to the first and second main surfaces of the inner layer substrate (20), respectively. Examples of such polishing methods include buff polishing, belt polishing, and roll polishing. Examples of commercially available polishing devices include the NT-700IM buff polishing device and the #1500 ceramic roll polishing device manufactured by Hyokisah Ishii.

[0143] -Process (C)-

[0144] In process (C), a first through-hole is formed that penetrates between the first and second main sides of the magnetic layer.

[0145] In order to form a desired conductor coil, a plurality of first through holes (23) are formed in the magnetic layer (22) (Fig. 5). For example, when the number of turns N of the conductor coil is 1, it is preferable to form 4 through holes as shown in Fig. 1, and when the number of turns N is 2, it is preferable to form 6 through holes as shown in Fig. 16. The number of first through holes may be appropriately determined according to the desired design of the conductor coil. Also, please note that the schematic cross-sectional view shown in Fig. 5 corresponds to the cross-section when the wiring board is cut at the position indicated by the dotted line X1-X1 in Fig. 1, and that only 2 first through holes (23) are shown.

[0146] The first through hole (23) can be formed by a known method, for example, using a drill, laser, plasma, etching medium, etc., taking into account the characteristics of the magnetic layer (22) or the dimensions of the first through hole (23). In addition, the shape of the first through hole (23) is as described above, and the dimensions of the first through hole or the pitch between the first through holes are not particularly limited as long as the desired conductor coil design can be achieved in relation to the dimensions of the opening (21) of the inner layer substrate (20) (corresponding to the dimensions of the magnetic layer (22)).

[0147] In order to realize a wiring board with even better inductance characteristics, it is desirable to consider the through structure defined by the conductor pattern (conductor coil) on the solenoid formed in the process (G) described later, and to determine the position of the first through hole so that a sufficient magnetic material exists in both the axial outer region and the lateral outer region. For example, when the diameter of the first through hole is D1, it is desirable that the distance between the center position of the first through hole and the inner layer substrate in the through axis direction of the conductor coil (up-down direction in FIG. 1 and FIG. 16) is 0.7D1 or greater, and more desirable that it is 0.8D1 or greater, 0.9D1 or greater, or D1 or greater. In addition, in the direction of the conductor coil's through-side (a direction perpendicular to the through-axis direction of the conductor coil; the left-right direction in FIG. 1 and FIG. 16), it is preferable that the distance between the center position of the first through-hole and the inner layer substrate is 0.7D1 or more, and more preferable that it is 0.8D1 or more, 0.9D1 or more, or D1 or more.

[0148] -Process (D)-

[0149] In process (D), an insulator is formed inside the first through hole.

[0150] The process (D) is not particularly limited as long as an insulator can be formed inside the first through-hole. For example, an insulating hole filling paste containing an insulating resin may be filled into the first through-hole, and the insulating hole filling paste may be heat-cured to form an insulator.

[0151] The composition of the insulating hole filling paste is not particularly limited as long as it can be filled into the first through-hole and can form an insulator by heat curing. For example, the insulating hole filling paste comprises an insulating resin and, if necessary, may additionally include an inorganic filler (excluding magnetic powder), a curing accelerator, and other additives.

[0152] As for the insulating resin, the binder resin described for the aforementioned magnetic paste may be used, and the suitable type and properties are the same as those of the binder resin. The content of the insulating resin is preferably 1 mass% or more, 3 mass% or more, or 5 mass% or more, when the non-volatile component in the insulating hole-filling paste is 100 mass%. The upper limit of the above content is not particularly limited, but is preferably 90 mass% or less, 80 mass% or less, or 70 mass% or less.

[0153] Examples of inorganic fillers (excluding magnetic powders) include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, talc, clay, mica powder, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, silicas such as amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica are particularly suitable. In addition, spherical silica is preferred as the silica. The inorganic filler may be used as a single type or in combination of two or more types.

[0154] From the perspective of realizing sufficient filling capacity, the average particle diameter of the inorganic filler is preferably in the range of 0.01 μm to 4 μm, more preferably in the range of 0.05 μm to 2 μm, even more preferably in the range of 0.1 μm to 1 μm, and even more preferably in the range of 0.3 μm to 0.8 μm. The average particle diameter of the inorganic filler can be measured in the same way as described for the average particle diameter of the magnetic powder.

[0155] In terms of improving moisture resistance and dispersibility, it is preferable that the inorganic filler be treated with one or more surface treatment agents, such as aminosilane-based coupling agents, epoxysilane-based coupling agents, mercaptosilane-based coupling agents, alkoxysilane compounds, organosilazanan compounds, and titanate-based coupling agents.

[0156] The content of the inorganic filler is preferably 5 mass% or more, 10 mass% or more, or 20 mass% or more, when the non-volatile component in the insulating hole-filling paste is 100 mass%, and preferably 95 mass% or less, 90 mass% or less, or 80 mass% or less.

[0157] As for the curing accelerator and other additives, the same ones described in relation to the magnetic paste may be used.

[0158] The filling of the insulation hole filling paste into the first through hole or the heat curing of the insulation hole filling paste may be carried out by the same method and conditions as in process (B).

[0159] In this way, an insulator (24) is formed in the first through-hole (23) of the magnetic layer (22) (Fig. 6). Additionally, the insulator (24) is formed to protrude from the magnetic layer (22), and subsequently, any excess insulator (24) protruding or attached from the magnetic layer (22) is removed by polishing and flattened / smoothed. Thus, as schematically shown in Fig. 6, the insulator (24) can be formed inside the first through-hole (23) of the magnetic layer (22) such that, in a direction perpendicular to the main surface of the substrate (the thickness direction of the substrate), the first and second main surfaces correspond substantially to the first and second main surfaces of the magnetic layer (22), respectively. Polishing may be performed by the same method as described in relation to process (B).

[0160] -Process (E)-

[0161] In process (E), a second through-hole is formed that penetrates the insulator.

[0162] The second through-hole (25) is formed in the insulator (24) formed in the first through-hole (23) of the magnetic layer (22) (see FIG. 7; FIG. 5 and FIG. 6). Accordingly, the number of the second through-hole (25) may be equal to the number of the first through-hole (23). For example, when the number of turns N of the conductor coil is 1, as shown in FIG. 1, it is preferable to form four first through-holes, form an insulator in each of them, and form a second through-hole; and when the number of turns N is 2, as shown in FIG. 16, it is preferable to form six first through-holes, form an insulator in each of them, and form a second through-hole. Also, please note that the schematic cross-sectional view shown in FIG. 7 corresponds to the cross-section when the wiring board is cut at the position indicated by the dotted line X1-X1 in FIG. 1, and that only two second through holes (25) are shown.

[0163] The second through-hole (25) can be formed by a known method, for example, using a drill, laser, plasma, etching medium, etc., taking into account the characteristics of the insulator (24) or the dimensions of the second through-hole (25). In addition, the shape of the second through-hole (25) is as described above, and the dimensions of the second through-hole or the pitch between the second through-holes are not particularly limited as long as the desired conductor coil design can be achieved in relation to the dimensions of the first opening. For example, when the diameter of the first through-hole is D1, the diameter D2 of the second through-hole is preferably 0.8D1 or less, more preferably 0.7D1 or less, 0.6D1 or less, or 0.5D1 or less, and preferably 0.2D1 or more, more preferably 0.3D1 or more. If the diameter D2 of the second through-hole is within this range, an insulator of sufficient thickness exists between the magnetic layer and the through-hole conductor, contributing to further improvement of the inductance characteristics. In addition, it is suitable to determine the position of the second through-hole so that the pitch between the second through-holes is substantially the same as the pitch between the first through-holes.

[0164] -Process (F)-

[0165] In process (F), a through-hole conductor is formed inside the second through-hole.

[0166] Prior to forming the through-hole conductor, it is desirable to desmear the interior of the second through-hole or the surface of the substrate. As for the desmearing treatment, a known desmearing treatment that can be used when forming interlayer conductors in the manufacture of a wiring board may be performed, or either a dry or wet desmearing treatment may be performed. Examples of dry desmearing treatment include plasma treatment. In addition, examples of wet desmearing treatment include a method of performing swelling treatment with a swelling liquid, harmonization treatment with an oxidizing agent, and neutralization treatment with a neutralizing liquid in this order.

[0167] A through-hole conductor may be formed by plating a second through-hole. For example, a through-hole conductor may be formed by forming a plating seed layer by electroless plating, and then forming a metal layer on the plating seed layer by electrolytic plating.

[0168] The structure of the through-hole conductor is not limited as long as it can form a conductor coil together with the first conductor pattern and the second conductor pattern described below. For example, the through-hole conductor may be a hollow cylindrical conductor (conformal through-hole conductor) formed by plating on the through-hole wall, or a cylindrical conductor (field through-hole conductor) with the inside of the through-hole filled with a conductor.

[0169] When forming a conformal through-hole conductor as a through-hole conductor, the interior of the hollow cylindrical conductor may be filled with an insulator. The filling of the insulator may be carried out in the same manner as in process (D), or, for example, an insulating hole filling paste may be filled and the insulating hole filling paste may be heat-cured to form the insulator. Additionally, the insulator is formed to protrude from the second through-hole, and then the excess insulator protruding or attached from the second through-hole is removed by polishing and flattened / smoothed. The polishing may be carried out in the same manner as described in relation to process (B).

[0170] As conductor materials constituting the through-hole conductor, for example, one or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium may be used. The through-hole conductor may be composed of a single metal or an alloy, and as an alloy, for example, an alloy of two or more metals selected from the above group (for example, nickel-chromium alloy, copper-nickel alloy, and copper-titanium alloy) may be used.

[0171] -Process (G)-

[0172] In process (G), a first conductor pattern and a second conductor pattern are formed on the first and second main surfaces of the magnetic layer, respectively, such that the first conductor pattern and the second conductor pattern are connected to a solenoid by a through-hole conductor.

[0173] Prior to forming the first conductor pattern and the second conductor pattern, it is preferable to desmear the surface of the substrate. As for the desmearing treatment, a known desmearing treatment that can be used when forming circuit conductors in the manufacture of a wiring board may be performed, or either a dry or wet desmearing treatment may be performed. An example of the desmearing treatment is as described in process (F).

[0174] The first conductor pattern and the second conductor pattern may be formed using known conductor pattern (circuit conductor) forming techniques such as the subtractive method and the semi-additive method.

[0175] For example, in the subtractive method, unnecessary parts (non-circuit forming parts) of the plated conductor layer are selectively removed by etching, etc., to form a conductor pattern. The formation of a conductor pattern by the subtractive method may be carried out according to known procedures. For example, the formation of a conductor pattern by the subtractive method may be carried out by a method comprising: i) forming a plating seed layer on the surface of a substrate by electroless plating; ii) forming a conductor layer by forming a metal layer on the plating seed layer by electrolytic plating; iii) forming an etching resist (dry film) on the surface of the conductor layer; iv) forming a wiring pattern by exposing and developing the etching resist; v) removing the exposed conductor layer by etching; and vi) removing the etching resist.

[0176] In addition, in the semi-additive method, the non-circuit forming portion of the plating seed layer is protected by a plating resist, and a metal such as copper is thickly plated on the circuit forming portion by electrolytic plating, then the plating resist is removed, and the plating seed layer other than the circuit forming portion is removed by etching to form a conductor pattern. The formation of a conductor pattern by the semi-additive method may be carried out according to known procedures. For example, the formation of a conductor pattern by the semi-additive method may be carried out by a method comprising: i) forming a plating seed layer by electroless plating on the surface of a substrate; ii) forming a plating resist (dry film) on the surface of the plating seed layer; iii) exposing and developing the plating resist to form a wiring pattern; iv) electrolytic plating through the plating resist; v) removing the plating resist; and vi) removing the plating seed layer other than the circuit forming portion by etching.

[0177] As long as the first conductor pattern can form a conductor coil together with the through-hole conductor and the second conductor pattern, the structure (pattern) is not limited. For example, the first conductor pattern may consist of a through-hole land (28a) and a connection pattern (28b) connecting the through-hole lands to each other (Fig. 1). The second conductor pattern is likewise composed of, for example, a through-hole land (29a) and a connection pattern (29b) connecting the through-hole lands to each other (Fig. 1; through-hole land (29a) is not shown).

[0178] The first conductor pattern and the second conductor pattern are connected by a through-hole conductor to form a conductor pattern (conductor coil) on a solenoid. By doing so, an inductor function is manifested.

[0179] As described above, the fact that the first conductor pattern is formed "on the first main surface of the magnetic layer" includes cases where the first conductor pattern is formed by bonding to the first main surface of the magnetic layer (directly), as well as cases where the first conductor pattern is formed on the first main surface of the magnetic layer through another layer. The same applies to the fact that the second conductor pattern is formed "on the second main surface of the magnetic layer," and includes cases where the second conductor pattern is formed by bonding to the second main surface of the magnetic layer (directly), as well as cases where the second conductor pattern is formed on the second main surface of the magnetic layer through another layer.

[0180] In an embodiment (also referred to as the "first embodiment") in which the above processes (A) to (G) are carried out so that the first conductor pattern and the second conductor pattern are formed by bonding them to the first and second main surfaces of the magnetic layer, respectively, a wiring board (100) shown in FIG. 8 can be manufactured. In the wiring board (100) shown in FIG. 8, the first conductor pattern (28) and the second conductor pattern (29) are formed by bonding them to the first main surface and the second main surface of the magnetic layer (22), respectively.

[0181] On the other hand, the above processes (A) to (G) may be carried out such that the first conductor pattern and the second conductor pattern are formed on the first and second main surfaces of the magnetic layer, respectively, with another layer interposed therebetween. Hereinafter, such an embodiment is also referred to as the “second embodiment.” As for the other layer, it is not particularly limited as long as it does not impede the effects of the present invention, and for example, an insulating layer may be used.

[0182] Hereinafter, a second embodiment will be described based on a suitable form in which an insulating layer is used as another layer.

[0183] In a second embodiment, the method for manufacturing a wiring substrate of the present invention, after process (D),

[0184] (D-1) A process of forming an insulating layer by bonding to a first main surface of an inner layer substrate and a first main surface of a magnetic layer, and

[0185] (D-2) A process of forming an insulating layer by bonding to the second main surface of the inner layer substrate and the second main surface of the magnetic layer.

[0186] Includes at least one additionally.

[0187] Process (D-1) and / or process (D-2) are not particularly limited as long as they can form an insulating layer by bonding to the main surface of the substrate, and may be carried out by a known method that can be used when forming an insulating layer of a wiring board. For example, an insulating adhesive film having an insulating adhesive layer may be used to bond and laminate the insulating adhesive layer to the main surface of the substrate, and the insulating adhesive layer may be heat-cured to form an insulating layer.

[0188] For example, as shown in FIG. 9, both process (D-1) and process (D-2) may be carried out using an insulating adhesive film. In FIG. 9, an insulating adhesive film (50) is laminated on both main surfaces of a substrate obtained in process (D) (a substrate in which an insulator (24) is formed in the first through-hole of the magnetic layer (22) shown in FIG. 6). The insulating adhesive film (50) includes a support (51) and an insulating adhesive layer (52) formed by bonding to the support, and is laminated on both main surfaces of the substrate so that the insulating adhesive layer (52) is bonded to the main surface of the substrate.

[0189] As for the support (51), examples include a film made of plastic material, a metal foil, and a release liner, and a film made of plastic material and a metal foil are preferred.

[0190] When using a film made of plastic material, examples of plastic materials include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylics such as polycarbonate (PC) and polymethyl methacrylate (PMMA), cyclic polyolefins, triacetylcellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide.

[0191] When using a metal foil, examples of metal foils include copper foil and aluminum foil, and copper foil is preferred. As for the copper foil, a foil made of a single metal of copper may be used, or a foil made of an alloy of copper and other metals (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) may be used.

[0192] The thickness of the support is not particularly limited, but is preferably in the range of 5㎛ to 75㎛, and more preferably in the range of 10㎛ to 60㎛.

[0193] The composition of the insulating adhesive layer (52) is not particularly limited, and it is sufficient if the cured product has sufficient insulating properties. The insulating adhesive layer (52) may be composed of a resin composition that, for example, includes a thermosetting resin and, if necessary, additionally includes components such as a curing agent, an inorganic filler, a curing accelerator, a thermoplastic resin, an organic filler, and a flame retardant. Regarding the thermosetting resin, curing agent, inorganic filler, curing accelerator, and thermoplastic resin, the same as those described in relation to magnetic paste or insulating hole filling paste may be used. Regarding the insulating adhesive layer for forming an insulating layer of a wiring board, there are numerous reports, such as Japanese Patent Publication No. 2018-100421, Japanese Patent Publication No. 2017-171925, and Japanese Patent Publication No. 2016-20480, and in the present invention, these known insulating adhesive layers may be selected and used according to the desired characteristics.

[0194] The thickness of the insulating adhesive layer (52) depends on the specific design of the wiring board, but from the perspective of thinning, it is preferably 100 μm or less, more preferably 80 μm or less, even more preferably 60 μm or less or 50 μm or less. The lower limit of the thickness of the insulating adhesive layer (52) can typically be 5 μm or more, 10 μm or more, etc.

[0195] Lamination between the insulating adhesive film (50) and the substrate may be performed by a vacuum lamination method. In the vacuum lamination method, the heat pressing temperature is preferably in the range of 60°C to 160°C, more preferably in the range of 80°C to 140°C, the heat pressing pressure is preferably in the range of 0.098 MPa to 1.77 MPa, more preferably in the range of 0.29 MPa to 1.47 MPa, and the heat pressing time is preferably in the range of 20 seconds to 400 seconds, more preferably in the range of 30 seconds to 300 seconds. Lamination is preferably performed under reduced pressure conditions of 26.7 hPa or less. Lamination can be performed using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include the vacuum pressure type laminator manufactured by Meiki Sesakusho Co., Ltd. and the vacuum applicator manufactured by Nikko Materials Co., Ltd.

[0196] After lamination, the insulating adhesive layer (52) is heat-cured to form an insulating layer. The heat-curing conditions of the insulating adhesive layer (52) may be the same as the heat-curing conditions of the magnetic paste or the insulating hole-filling paste.

[0197] The support (51) may be peeled off before the thermal curing of the insulating adhesive layer, or peeled off after the thermal curing of the insulating adhesive layer. Alternatively, if a metal foil is used as the support (51), the first conductor pattern and the second conductor pattern may be formed using the metal foil without peeling off the metal foil. Below, the embodiments are divided into an embodiment in which the support is peeled off and an embodiment in which the conductor pattern is formed using the support metal foil.

[0198] -Effect of peeling off the support-

[0199] When the support (51) is peeled off, the substrate shown in FIG. 10 is obtained. In the substrate shown in FIG. 10, an insulating layer (34) is formed by bonding to the first and second main surfaces of the inner layer substrate (20) and the magnetic layer (22). Additionally, FIG. 10 does not distinguish between the insulating member derived from the insulator (24) (Fig. 9) formed in the first through-hole of the magnetic layer (22) and the insulating layer (34) obtained by the thermal curing of the insulating resin layer (52), but the composition of the insulator (24) and the composition of the insulating layer (34) may be the same or different.

[0200] After forming the insulating layer (34), it is preferable to perform process (E). In this embodiment, in process (E), a second through-hole (35) is formed that penetrates not only the insulator (24) but also the insulating layer (34) (see FIG. 11; FIG. 9 and FIG. 10). The number and dimensions of the second through-holes and the pitch between the second through-holes are as described above.

[0201] After forming the second through-hole, a through-hole conductor (36) can be formed inside the second through-hole (35) by performing process (F). Then, by performing process (G), a solenoid-shaped conductor pattern (conductor coil) can be formed by connecting the first conductor pattern (38), the second conductor pattern (39), and the through-hole conductor (36). In this way, a wiring board (200) shown in FIG. 12 can be obtained. In the wiring board (200), the first conductor pattern (38) is formed by bonding to the surface of the insulating layer (34) on the first main surface of the magnetic layer (22), and the second conductor pattern (39) is formed by bonding to the surface of the insulating layer (34) on the second main surface of the magnetic layer (22).

[0202] -Embodiment of forming a conductor pattern using a support metal foil-

[0203] When using a metal foil as a support (51), the first conductor pattern and the second conductor pattern may be formed using the metal foil without peeling off the metal foil.

[0204] In this embodiment, a substrate shown in FIG. 13 is obtained. In the substrate shown in FIG. 13, an insulating layer (34) is formed by bonding to the first and second main surfaces of the inner layer substrate (20) and the magnetic layer (22), and additionally, a support metal foil (51) is formed by bonding to the insulating layer (34). Also, in FIG. 13, as in FIG. 10, the insulating member derived from the insulator (24) (Fig. 9) formed in the first through-hole of the magnetic layer (22) and the insulating layer (34) obtained by the thermal curing of the insulating resin layer (52) are not distinguished, and the composition of the insulator (24) and the composition of the insulating layer (34) may be the same or different.

[0205] It is preferable to perform process (E) on such a substrate. In this embodiment, in process (E), a second through-hole (45) is formed that penetrates not only the insulator (24) but also the insulating layer (34) and the support metal foil (51) (see FIG. 14; FIG. 9 and FIG. 13). The number and dimensions of the second through-holes and the pitch between the second through-holes are as described above.

[0206] After forming the second through-hole, by performing process (F), a through-hole conductor (46) can be formed inside the second through-hole (45). Then, by performing process (G), the first conductor pattern (48), the second conductor pattern (49), and the through-hole conductor (46) can be connected to form a solenoid-shaped conductor pattern (conductor coil). In process (G), the first conductor pattern (48) and the second conductor pattern (49) may be formed using a conductor pattern forming technique such as a subtractive method or a semi-additive method (modified semi-additive method) using a support metal foil (51). For example, in the subtractive method, the unnecessary part (non-circuit forming part) of the support metal foil is selectively removed by etching, etc., to form the conductor pattern. For example, the formation of a conductor pattern by the subtractive method can be carried out by a method comprising: i) forming an etching resist (dry film) on the surface of a support metal foil; ii) exposing and developing the etching resist to form a wiring pattern; iii) etching and removing the exposed support metal foil; and iv) removing the etching resist. Additionally, in the semi-additive method, the support metal foil may be used as a plating seed layer to form a conductor pattern. For example, the formation of a conductor pattern by the semi-additive method can be carried out by a method comprising: i) forming a plating resist (dry film) on the surface of a support metal foil (plating seed layer); ii) exposing and developing the plating resist to form a wiring pattern; iii) electroplating through the plating resist; iv) removing the plating resist; and v) etching and removing the support metal foil other than the circuit forming portion.

[0207] In this way, a wiring board (300) as shown in FIG. 15 can be obtained. In the wiring board (300), a first conductor pattern (48) is formed by bonding to the surface of an insulating layer (34) on the first main surface of a magnetic layer (22), and a second conductor pattern (49) is formed by bonding to the surface of an insulating layer (34) on the second main surface of a magnetic layer (22).

[0208] The method for manufacturing a wiring board of the present invention may additionally include a process of forming a conductor layer by bonding it to the surface of the insulating layer when forming an insulating layer (34) by bonding it to at least one of the first and second main surfaces of an inner layer substrate (20) (Figs. 12 and 15). Accordingly, in one embodiment, the method for manufacturing a wiring board of the present invention additionally includes a process of forming a conductor layer on the surface of the insulating layer on at least one of the first and second main surfaces of an inner layer substrate.

[0209] The method for manufacturing a wiring board of the present invention may further include a process of forming an insulating layer and a conductor layer (wiring layer) alternately on at least one of the first and second main surfaces of an inner layer substrate (20) (and a magnetic layer (22)) to form a multilayer wiring. Regarding the specific design of the insulating layer, the wiring layer, and the multilayer wiring, known layer configurations or designs may be used when manufacturing a wiring board. For example, by using the wiring board shown in FIGS. 8, FIGS. 12, and FIGS. 15 as an inner layer circuit board and alternately forming an insulating layer and a conductor layer on the inner layer circuit board, it is possible to manufacture a wiring board having a multilayer wiring in which an inductor structure is formed.

[0210] [ Examples ]

[0211] The present invention will be described in detail below by presenting examples. However, the present invention is not limited to the examples shown below.

[0212] [Example 1]

[0213] 1-A. Preparation of an inner layer substrate with an opening

[0214] An inner layer substrate with a thickness of 0.8 mm ("MCL-E-705GL", copper foil etched-out product, manufactured by Hitachi Kasei Co., Ltd.) was prepared. A circular opening with a diameter of 1.4 mm was formed in this inner layer substrate using a drill. The opening was formed using a drill "ST" manufactured by Union Tool Co., Ltd. at a rotational speed of 46,000 rpm.

[0215] 1-B. Formation of the magnetic layer

[0216] A magnetic paste was vacuum printed into an opening with a diameter of 1.4 mm. The magnetic paste used was a material with a magnetic powder content of 90 mass%, a viscosity of 60 Pa·sec (measurement environment using an E-type viscometer at 25°C and 5 rpm), and a relative permeability of 7 @ 100 MHz. After vacuum printing, the magnetic paste was heat-cured by heating at 130°C for 30 minutes and then further heating at 145°C for 30 minutes to form a magnetic layer inside the opening. Subsequently, the surfaces of the inner layer substrate and the magnetic layer were polished to smooth them. Polishing was performed using a ceramic polishing roll #1500 manufactured by Hyokisah Ishii.

[0217] 1-C. Formation of the First Through-hole

[0218] A first through hole with a diameter of 0.3 mm was formed in a magnetic layer with a diameter of 1.4 mm using a drill. As shown in FIG. 1, four first through holes were formed (left-right pitch 0.6 mm; up-down pitch 0.5 mm). The first through holes were formed using a drill "UV" manufactured by Union Tool Co., under conditions of a rotational speed of 60,000 rpm.

[0219] 1-D. Formation of an Insulator

[0220] Insulating hole filling paste ("IR-10F", manufactured by San-Ei Kagaku Co., Ltd.) was vacuum printed into each of the first through-holes with a diameter of 0.3 mm. After vacuum printing, the insulating hole filling paste was heat-cured by heating at 110°C for 30 minutes and then heating at 150°C for 60 minutes to obtain an insulator inside the first through-hole. Subsequently, the surface of the insulator was polished to smooth it. Polishing was performed using a ceramic polishing roll #1500 manufactured by Ishii Hyokisah.

[0221] 1-D'. Formation of an insulating layer

[0222] Next, an insulating adhesive film ("ABF-GX92R", insulating resin layer thickness 30㎛, support PET, manufactured by Ajinomoto Fine Techno Co., Ltd.) was laminated on both sides of a substrate by vacuum lamination so that the insulating resin layer was bonded to the surface of the substrate. After vacuum lamination, the insulating resin layer was heat-cured by heating at 100°C for 30 minutes and then further heating at 180°C for 30 minutes to obtain an insulating layer.

[0223] 1-E. Formation of the Second Through-hole

[0224] A second through-hole with a diameter of 0.15 mm was formed in each of the 0.3 mm diameter insulators using a drill (n=4). The second through-hole was positioned so that its center coincided with the center of the first through-hole (0.3 mm diameter insulator). The second through-hole was formed using a Union Tool Corporation drill "NEU" at a rotational speed of 80,000 rpm.

[0225] 1-F. Formation of Through-hole Conductors

[0226] After desmearing the inside of the second through-hole and the surface of the substrate, electroless plating (thickness 0.7 μm) and electrolytic plating (thickness 22 μm) were performed, and through-hole conductors (conformal type) were formed in each of the second through-holes.

[0227] After forming the through-hole conductor, an insulating hole filling paste ("IR-10F", manufactured by San-Ei Kagaku Co., Ltd.) was vacuum printed onto each of the second through-holes. After vacuum printing, the insulating hole filling paste was heat-cured by heating at 110°C for 30 minutes and then heating at 150°C for 60 minutes to form an insulator. Subsequently, the surface of the insulator was polished to smooth it. Polishing was performed using a ceramic polishing roll #1500 manufactured by Ishii Hyokisah.

[0228] 1-G. Formation of conductor pattern on solenoid

[0229] After desmearing the surface of the substrate, electroless plating (thickness 0.7 μm) and electrolytic plating (thickness 22 μm) were performed to form a conductor layer. A dry film was laminated onto the conductor layer, and the dry film was patterned by exposure and development. Subsequently, a conductor pattern was formed using a ferric chloride etching solution by the subtractive method, and then the dry film was peeled off. The conductor pattern was formed on both sides of the substrate as shown in Fig. 1. That is, the surface conductor pattern of the substrate and the through-hole conductor were formed to be connected in a solenoid shape, thereby creating an inductor structure on the wiring board.

[0230] [Example 2]

[0231] 2-A. Preparation of an inner layer substrate with an opening

[0232] An inner layer substrate with a thickness of 0.8 mm ("MCL-E-705GL", copper foil etched-out product, manufactured by Hitachi Kasei Co., Ltd.) was prepared. A circular opening with a diameter of 1.4 mm was formed in this inner layer substrate using a drill. The opening was formed using a drill "ST" manufactured by Union Tool Co., Ltd. at a rotational speed of 46,000 rpm.

[0233] 2-B. Formation of the magnetic layer

[0234] A magnetic paste was vacuum printed into an opening with a diameter of 1.4 mm. The magnetic paste used was a material with a magnetic powder content of 90 mass%, a viscosity of 60 Pa·sec (measurement environment using an E-type viscometer at 25°C and 5 rpm), and a relative permeability of 7 @ 100 MHz. After vacuum printing, the magnetic paste was heat-cured by heating at 130°C for 30 minutes and then further heating at 145°C for 30 minutes to form a magnetic layer inside the opening. Subsequently, the surfaces of the inner layer substrate and the magnetic layer were polished to smooth them. Polishing was performed using a ceramic polishing roll #1500 manufactured by Hyokisah Ishii.

[0235] 2-C. Formation of the First Through-hole

[0236] A first through hole with a diameter of 0.3 mm was formed in a magnetic layer with a diameter of 1.4 mm using a drill. As shown in FIG. 1, four first through holes were formed (left-right pitch 0.6 mm; up-down pitch 0.5 mm). The first through holes were formed using a drill "UV" manufactured by Union Tool Co., under conditions of a rotational speed of 60,000 rpm.

[0237] 2-D. Formation of Insulators

[0238] Insulating hole filling paste ("IR-10F", manufactured by San-Ei Kagaku Co., Ltd.) was vacuum printed into each of the first through-holes with a diameter of 0.3 mm. After vacuum printing, the insulating hole filling paste was heat-cured by heating at 110°C for 30 minutes and then heating at 150°C for 60 minutes to obtain an insulator inside the first through-hole. Subsequently, the surface of the insulator was polished to smooth it. Polishing was performed using a ceramic polishing roll #1500 manufactured by Ishii Hyokisah.

[0239] 2-D'. Formation of an insulating layer

[0240] Next, an insulating adhesive film ("ABF-GX92-RCC", insulating resin layer thickness 30 μm, support copper foil, manufactured by Ajinomoto Fine Techno Co., Ltd.) was laminated on both sides of a substrate by vacuum lamination so that the insulating resin layer was bonded to the surface of the substrate. After vacuum lamination, the insulating resin layer was heat-cured by heating at 100°C for 30 minutes and then further heating at 180°C for 30 minutes to obtain an insulating layer.

[0241] 2-E. Formation of the Second Through-hole

[0242] A second through-hole with a diameter of 0.15 mm was formed in each of the 0.3 mm diameter insulators using a drill (n=4). The second through-hole was positioned so that its center coincided with the center of the first through-hole (0.3 mm diameter insulator). The second through-hole was formed using a Union Tool Corporation drill "NEU" at a rotational speed of 80,000 rpm.

[0243] 2-F. Formation of Through-hole Conductors

[0244] After desmearing the inside of the second through-hole and the surface of the substrate, electroless plating (thickness 0.7 μm) and electrolytic plating (thickness 22 μm) were performed, and through-hole conductors (conformal type) were formed in each of the second through-holes.

[0245] After forming the through-hole conductor, an insulating hole filling paste ("IR-10F", manufactured by San-Ei Kagaku Co., Ltd.) was vacuum printed onto each of the second through-holes. After vacuum printing, the insulating hole filling paste was heat-cured by heating at 110°C for 30 minutes and then heating at 150°C for 60 minutes to form an insulator. Subsequently, the surface of the insulator was polished to smooth it. Polishing was performed using a ceramic polishing roll #1500 manufactured by Ishii Hyokisah.

[0246] 2-G. Formation of conductor pattern on solenoid

[0247] After desmearing the surface of the substrate, electroless plating (thickness 0.7 μm) and electrolytic plating (thickness 22 μm) were performed to form a conductor layer together with a copper foil support. A dry film was laminated onto the conductor layer, exposed and developed, and the dry film was patterned. Subsequently, a conductor pattern was formed using a ferric chloride etching solution by the subtractive method, and then the dry film was peeled off. The conductor pattern was formed on both sides of the substrate as shown in Fig. 1. That is, the surface conductor pattern of the substrate and the through-hole conductor were formed to be connected in a solenoid shape, thereby creating an inductor structure on the wiring board.

[0248] [Example 3]

[0249] 3-A. Preparation of an inner layer substrate with an opening

[0250] An inner layer substrate with a thickness of 0.8 mm ("MCL-E-705GL", copper foil etched-out product, manufactured by Hitachi Kasei Co., Ltd.) was prepared. A circular opening with a diameter of 1.4 mm was formed in this inner layer substrate using a drill. The opening was formed using a drill "ST" manufactured by Union Tool Co., Ltd. at a rotational speed of 46,000 rpm.

[0251] 3-B. Formation of the magnetic layer

[0252] A magnetic paste was vacuum printed into an opening with a diameter of 1.4 mm. The magnetic paste used was a material with a magnetic powder content of 90 mass%, a viscosity of 60 Pa·sec (measurement environment using an E-type viscometer at 25°C and 5 rpm), and a relative permeability of 7 @ 100 MHz. After vacuum printing, the magnetic paste was heat-cured by heating at 130°C for 30 minutes and then further heating at 145°C for 30 minutes to form a magnetic layer inside the opening. Subsequently, the surfaces of the inner layer substrate and the magnetic layer were polished to smooth them. Polishing was performed using a ceramic polishing roll #1500 manufactured by Hyokisah Ishii.

[0253] 3-C. Formation of the First Through-hole

[0254] A first through hole with a diameter of 0.3 mm was formed in a magnetic layer with a diameter of 1.4 mm using a drill. As shown in FIG. 1, four first through holes were formed (left-right pitch 0.6 mm; up-down pitch 0.5 mm). The first through holes were formed using a drill "UV" manufactured by Union Tool Co., under conditions of a rotational speed of 60,000 rpm.

[0255] 3-D. Formation of Insulator

[0256] Insulating hole filling paste ("IR-10F", manufactured by San-Ei Kagaku Co., Ltd.) was vacuum printed into each of the first through-holes with a diameter of 0.3 mm. After vacuum printing, the insulating hole filling paste was heat-cured by heating at 110°C for 30 minutes and then heating at 150°C for 60 minutes to obtain an insulator inside the first through-hole. Subsequently, the surface of the insulator was polished to smooth it. Polishing was performed using a ceramic polishing roll #1500 manufactured by Ishii Hyokisah.

[0257] 3-E. Formation of the Second Through-hole

[0258] A second through-hole with a diameter of 0.15 mm was formed in each of the 0.3 mm diameter insulators using a drill (n=4). The second through-hole was positioned so that its center coincided with the center of the first through-hole (0.3 mm diameter insulator). The second through-hole was formed using a Union Tool Corporation drill "NEU" at a rotational speed of 80,000 rpm.

[0259] 3-F. Formation of Through-hole Conductors

[0260] After desmearing the inside of the second through-hole and the surface of the substrate, electroless plating (thickness 0.7 μm) and electrolytic plating (thickness 22 μm) were performed, and through-hole conductors (conformal type) were formed in each of the second through-holes.

[0261] After forming the through-hole conductor, an insulating hole filling paste ("IR-10F", manufactured by San-Ei Kagaku Co., Ltd.) was vacuum printed onto each of the second through-holes. After vacuum printing, the insulating hole filling paste was heat-cured by heating at 110°C for 30 minutes and then heating at 150°C for 60 minutes to form an insulator. Subsequently, the surface of the insulator was polished to smooth it. Polishing was performed using a ceramic polishing roll #1500 manufactured by Ishii Hyokisah.

[0262] 3-G. Formation of conductor pattern on solenoid

[0263] After desmearing the surface of the substrate, electroless plating (thickness 0.7 μm) and electrolytic plating (thickness 22 μm) were performed to form a conductor layer. A dry film was laminated onto the conductor layer, and the dry film was patterned by exposure and development. Subsequently, a conductor pattern was formed using a ferric chloride etching solution by the subtractive method, and then the dry film was peeled off. The conductor pattern was formed on both sides of the substrate as shown in Fig. 1. That is, the surface conductor pattern of the substrate and the through-hole conductor were formed to be connected in a solenoid shape, thereby creating an inductor structure on the wiring board. Explanation of the symbols

[0264] 10, 10': Inductor structure 20: Inner layer substrate 20a: 1st face 20b: The second week 21: Opening (1st opening) 22: Magnetic layer 23: 1st through hole (2nd opening) 24: Insulator 25, 35, 45: 2nd through-hole (3rd opening) 26, 36, 46: Through-hole conductors 27, 37, 47: Insulator (inside of conformal through-hole conductor) 28, 38, 48: First conductor pattern 28a: Through-hole land 28b: Connection pattern 29, 39, 49: Second conductor pattern 29a: Throughhole Land (not a city) 29b: Connection pattern 34: Insulating layer 50: Insulating adhesive film 51: Support body 52: Insulating resin layer 100, 200, 300: Wiring board

Claims

Claim 1 A wiring board having an inductor function comprising: an inner layer substrate having first and second main surfaces and an opening formed penetrating between the first and second main surfaces; a magnetic layer formed inside the opening, wherein a plurality of first through-holes are formed penetrating the first and second main surfaces; an insulator formed inside each of the first through-holes, wherein a second through-hole is formed penetrating the insulator; a first conductor pattern formed on the first main surface of the magnetic layer; a second conductor pattern formed on the second main surface of the magnetic layer; and a solenoid-shaped conductor pattern formed inside the second through-hole and comprising a through-hole conductor connecting the first conductor pattern and the second conductor pattern, wherein the solenoid-shaped conductor pattern is provided within the region of the magnetic layer when viewed from a direction perpendicular to the main surface of the wiring board. Claim 2 A wiring board according to claim 1, further comprising an insulating layer formed by bonding to a first main surface of an inner layer substrate and a first main surface of a magnetic layer, wherein a first conductor pattern is formed by bonding to the surface of the insulating layer on the first main surface of the magnetic layer. Claim 3 A wiring board according to claim 1, further comprising an insulating layer formed by bonding to a second main surface of an inner layer substrate and a second main surface of a magnetic layer, wherein a second conductor pattern is formed by bonding to the surface of the insulating layer on the second main surface of the magnetic layer. Claim 4 A wiring substrate according to claim 2, comprising a conductor layer formed by bonding to the surface of an insulating layer on at least one of the first and second main sides of an inner layer substrate. Claim 5 A wiring substrate according to claim 3, comprising a conductor layer formed by bonding to the surface of an insulating layer on at least one of the first and second main sides of an inner layer substrate. Claim 6 A wiring board according to claim 1, wherein the inner layer substrate is an insulating substrate. Claim 7 A wiring board according to claim 1, wherein the inner layer substrate is a circuit board. Claim 8 A wiring board according to claim 1, wherein the inner layer substrates have a plurality of openings formed at a predetermined distance from each other. Claim 9 delete Claim 10 In claim 1, the wiring board, wherein the insulator has a thickness substantially equal to the thickness of the magnetic layer. Claim 11 A wiring board according to claim 1, wherein, when the diameter of the first through-hole is D1, the diameter of the second through-hole D2 is 0.8D1 or less. Claim 12 A method for manufacturing a wiring board having an inductor function as described in any one of claims 1 to 8, 10, and 11, comprising the following processes (A) to (G): (A) a process of preparing an inner layer substrate having first and second main surfaces and having an opening formed penetrating between the first and second main surfaces; (B) a process of filling a magnetic paste into the opening and heat-curing the magnetic paste to form a magnetic layer; (C) a process of forming a plurality of first through-holes penetrating between the first and second main surfaces of the magnetic layer; (D) a process of forming an insulator inside each of the first through-holes; (E) a process of forming a second through-hole penetrating the insulator; (F) a process of forming a through-hole conductor inside the second through-hole; and (G) forming a first conductor pattern and a second conductor pattern, respectively, on the first and second main surfaces of the magnetic layer, the first conductor A method for manufacturing a wiring board, comprising a process of forming a pattern and a second conductor pattern so as to be connected to a solenoid by a through-hole conductor. Claim 13 The following processes (A) to (G): (A) a process of preparing an inner layer substrate having first and second main surfaces and having an opening formed penetrating between the first and second main surfaces; (B) a process of filling a magnetic paste into the opening and heat-curing the magnetic paste to form a magnetic layer; (C) a process of forming a plurality of first through-holes penetrating between the first and second main surfaces of the magnetic layer; (D) a process of forming an insulator inside each of the first through-holes; (E) a process of forming a second through-hole penetrating the insulator; (F) a process of forming a through-hole conductor inside the second through-hole; and (G) a process of forming a first conductor pattern and a second conductor pattern, respectively, on the first and second main surfaces of the magnetic layer such that the first conductor pattern and the second conductor pattern are connected in a solenoid manner by the through-hole conductor, comprising a method for manufacturing a wiring board having an inductor function. (D) After, (D-1) a process of forming an insulating layer by bonding to a first main surface of an inner layer substrate and a first main surface of a magnetic layer, and (D-2) a process of forming an insulating layer by bonding to a second main surface of an inner layer substrate and a second main surface of a magnetic layer, further comprising at least one of these steps. Claim 14 A method for manufacturing a wiring board according to claim 12, wherein the viscosity (25°C) of the magnetic paste is 20 to 250 Pa·s. Claim 15 A method for manufacturing a wiring board according to claim 13, wherein the viscosity (25°C) of the magnetic paste is 20 to 250 Pa·s. Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 A method for manufacturing a wiring board according to claim 13, wherein in process (E), a second through-hole penetrating an insulating layer and an insulator is formed. Claim 20 delete Claim 21 A method for manufacturing a wiring board according to claim 13, further comprising the process of forming a conductor layer on the surface of an insulating layer on at least one of the first and second main sides of an inner layer substrate.

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