Wiring board and method for manufacturing wiring board

Abstract

To provide a technology that can suppress the decline in magnetism of magnetic resin bodies with respect to conventional wiring boards.SOLUTION: A wiring board comprises a substrate layer with a plurality of through holes formed, a magnetic resin body that fills each of the through holes, through hole conductors that penetrate each of the magnetic resin body, and a through hole land covering the entire end face of each of the magnetic resin bodies.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a wiring board including a plurality of through-hole conductors and a method for manufacturing the same.

Background Art

[0002] Conventionally, as this type of wiring board, in order to increase inductance, a core substrate is provided with a magnetic resin body surrounding each through-hole conductor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0014] , FIG. 1)

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object is to provide a technique capable of suppressing a decrease in the magnetism of a magnetic resin body with respect to a conventional wiring board.

Means for Solving the Problems

[0005] A wiring board according to an aspect of the present disclosure includes a base material layer in which a plurality of through-holes are formed, a magnetic resin body filling each of the through-holes, a through-hole conductor penetrating each of the magnetic resin bodies, and a through-hole land covering the entire end face of each of the magnetic resin bodies.

[0006] A method for manufacturing a wiring board according to an aspect of the present disclosure includes: forming a plurality of through holes in a base material layer; filling the plurality of through holes with a plurality of magnetic resin bodies; forming through-hole conductors penetrating each of the magnetic resin bodies; and forming a conductive layer including through-hole lands connected to the through-hole conductors. The method for manufacturing a wiring board includes: forming a conductive film on the front and back of the base material layer; laminating an etching resist on the conductive film so as to cover the entire end face of the magnetic resin body as viewed from the lamination direction; and etching a portion of the conductive film laminated on the base material layer that is exposed from the etching resist to form the conductive layer.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0008] An embodiment of the present disclosure will be described with reference to FIGS. 1 to 8. As shown in FIG. 1, the wiring board 10 of the present embodiment has a core board 11 and first and second build-up layers 12A and 12B laminated on the front and back thereof.

[0009] The first and second build-up layers 12A and 12B have insulating layers 15 and conductive layers 20 that are alternately laminated, and a solder resist layer 17 is laminated on the outermost layer. The solder resist layer 17 is provided with a plurality of openings 17H corresponding to a plurality of pads 18 included in the conductive layer 20. A plurality of solder bumps 19 are provided on the plurality of pads 18.

[0010] The core substrate 11 includes, for example, an insulating layer 11K and conductive layers 13 laminated on both the front and back surfaces thereof. The insulating layer 11K has a plurality of body holes 11H, and the plurality of body holes 11H are filled with a plurality of magnetic resin bodies 40. The plurality of magnetic resin bodies 40 are composed of a magnetic resin 41 having a circular cross-section (see FIG. 3) and having magnetism.

[0011] The magnetic resin 41 is composed of a resin containing magnetic particles. The magnetic particles are, for example, iron oxide, nickel, nickel alloy, cobalt, or tin, and resins such as epoxy resin and phenol resin are used for the resin.

[0012] A through-hole conductor 31 is formed in each magnetic resin body 40. Each through-hole conductor 31 is formed, for example, on the inner surface of a through-hole 31H coaxial with the magnetic resin body 40, and a filling resin 31P is provided inside.

[0013] An inductor 34 including a part of these plurality of through-hole conductors 31 is formed on the core substrate 11. Specifically, the plurality of through-hole conductors 31 described above are arranged in a row at intervals, and relay wirings 33 that connect adjacent through-hole conductors 31 so that the plurality of through-hole conductors 31 are connected in series are alternately arranged on the front and back of the core substrate 11. Then, a rectangular wave-shaped inductor 34 that extends so as to sew the core substrate 11 on the front and back is formed by the plurality of through-hole conductors 31 and the plurality of relay wirings 33.

[0014] As shown in FIG. 3, the relay wiring 33 is formed on the conductive layer 13 described above, and has a through-hole land 33A and a connecting portion 33B that connects between the through-hole lands 33A. The through-hole land 33A has, for example, a circular shape coaxial with the magnetic resin body 40, and a via conductor 21 (see FIG. 1) is provided on the upper part thereof. The connecting portion 33B has a linear shape with a width sufficiently narrower than that of the through-hole land 33A. In FIG. 3, the width of the connecting portion 33B is smaller than the outer diameter of the through-hole land 33A. However, for example, the width of the connecting portion 33B may be the same as the outer diameter of the through-hole land 33A, and a configuration in which the boundary between the through-hole land 33A and the connecting portion 33B is not distinguishable may be employed.

[0015] In FIG. 1, an example is shown in which the inductor 34 extends linearly when viewed from the stacking direction. However, the inductor 34 may have, for example, a waveform, an annular shape, or a spiral shape when viewed from the stacking direction.

[0016] As shown in FIG. 1, a plurality of through-holes 32H are formed in a portion of the core substrate 11 where the magnetic resin body 40 is not provided, and through-hole conductors 32 having a filling resin 32P inside are formed in each of these through-holes 32H. In the example shown in FIG. 1, some of the through-hole conductors 32 are arranged on the extension line of the inductor 34 and are connected to the inductor 34 via the relay wiring 33.

[0017] As shown in FIG. 2, the conductive layer 13 including the relay wiring 33 has a structure in which a plating film 50 is laminated on a metal foil 11D (for example, a copper foil) laminated on the insulating layer 11K. The plating film 50 has six layers, namely, a first electroless plating film 51A, a first electrolytic plating film 51B, a second electroless plating film 52A, a second electrolytic plating film 52B, a third electroless plating film 53A, and a third electrolytic plating film 53B in order from the metal foil 11D side. Further, through-hole conductors 31 and 32 that cover the inner surfaces of the plurality of through-holes 31H and 32H are formed by the second electroless plating film 52A and the second electrolytic plating film 52B among these plating films 50.

[0018] Of the conductive layer 13, the first electroless plating film 51A and the first electrolytic plating film 51B are shielding plating for preventing the end face 40A of the magnetic resin body 40 from coming into contact with a desmear solution (for example, potassium permanganate). Also, the third electroless plating film 53A and the third electrolytic plating film 53B are cover plating for covering the filling resins 31P and 32P of the through holes 31 and 32.

[0019] Incidentally, in the present embodiment, as shown in FIGS. 2 and 3, the through-hole land 33A protrudes from the outer edge of the magnetic resin body 40, and the entire end face 40A of the magnetic resin body 40 is covered with the through-hole land 33A. In the examples shown in FIGS. 2 and 3, the outer diameter D1 of the magnetic resin body 40 is 350 μm or less, while the outer diameter D2 of the through-hole land 33A is larger than 350 μm (preferably, larger than 360 μm).

[0020] Also, in the present embodiment, as shown in FIG. 2, the end faces 40A of the plurality of magnetic resin bodies 40 are formed substantially flush with the surface of the metal foil 11D in the conductive layer 13. Thereby, the magnetic resin body 40 is covered with the plating film 50 that constitutes the through-hole land 33A at the end face 40A, and the end portion of the outer surface 40B is covered with the metal foil 11D that constitutes the through-hole land 33A. Note that the through-hole land 33A has a seven-layer structure having the metal foil 11D only at the outer edge portion, and an inner portion overlapping the magnetic resin body 40 in the stacking direction has a six-layer structure of only the plating film 50 having no metal foil 11D.

[0021] The wiring board 10 of the present disclosure is manufactured as follows. (1) A laminate 11S (corresponding to the "base material layer" of the present disclosure) in which metal foils 11D are laminated on both sides of the insulating layer 11K is prepared. As shown in FIG. 4A, a plurality of main body holes 11H (corresponding to the "plurality of through holes" of the present disclosure) are formed in the laminate 11S by, for example, drilling or the like, and are deburred and polished.

[0022] (2) As shown in FIG. 4B, the plurality of main body holes 11H are filled with a paste of magnetic resin 41 by vacuum printing. Then, both end faces on the front and back of the magnetic resin 41 are polished so as to be flush with the laminated plate 11S. Thereby, a plurality of magnetic resin bodies 40 having end faces 40A substantially flush with the metal foil 11D are formed.

[0023] (3) Next, an electroless plating process and an electrolytic plating process are performed, and a first electroless plating film 51A and a first electrolytic plating film 51B serving as shield plating are formed on both the front and back surfaces of the laminated plate 11S including the magnetic resin body 40 (see FIG. 4C).

[0024] (4) In forming the through holes 31H and 32H, first, a drilling process for forming the through hole 32H is performed. As shown in FIG. 5A, a through hole 32H is formed in the laminated plate 11S on which the first electrolytic plating film 51B is laminated, for example, by drilling or the like, and desmear treatment is performed. In this desmear treatment, smear is removed using a desmear solution (for example, potassium permanganate). At this time, since the end face 40A of the magnetic resin body 40 is covered with the first electroless plating film 51A and the first electrolytic plating film 51B formed in the step (3), it does not come into contact with the desmear solution.

[0025] (5) Next, a drilling process for forming the through hole 31H in the magnetic resin body 40 is performed. In the present embodiment, for example, the through hole 31H is formed by cutting such as drilling (see FIG. 5B). Then, desmear treatment is performed. In this desmear treatment, smear is removed not by the above-described desmear solution but by medium-pressure water washing or high-pressure water washing.

[0026] (6) Next, an electroless plating process and an electrolytic plating process are performed, and a second electroless plating film 52A and a second electrolytic plating film 52B are formed on the inner surfaces of the plurality of through holes 31H and 32H and on the first electrolytic plating film 51B (see FIG. 6A).

[0027] (7) As shown in FIG. 6B, the resin is filled in the through-hole conductors 31 and 32, and both end faces of the resin are polished so as to be flush with the second electrolytic plating film 52B, respectively. Thereby, the filled resins 31P and 32P are formed.

[0028] (8) Next, the electroless plating process and the electrolytic plating process are performed. Thereby, as shown in FIG. 6C, the third electroless plating film 53A and the third electrolytic plating film 53B are formed on the second electrolytic plating film 52B and on the exposed surfaces (end faces) of the filled resins 31P and 32P.

[0029] (9) Next, as shown in FIG. 7A, an etching resist 60 having a predetermined pattern is formed on the third electrolytic plating film 53B. At this time, when viewed from the stacking direction, the etching resist 60 has a size that covers the entire end face 40A of the magnetic resin body 40.

[0030] (10) An etching process is performed to remove the metal foil 11D, the first to third electroless plating films 51A to 53A, and the first to third electrolytic plating films 51B to 53B that are exposed from the etching resist 60, and then the etching resist 60 is removed. Thereby, as shown in FIG. 7B, a conductive layer 13 including the relay wiring 33 is formed on both the front and back surfaces of the insulating layer 11K, and the core substrate 11 is obtained.

[0031] At this time, in the present embodiment, since the entire end face 40A of the magnetic resin body 40 is covered with the first to third electroless plating films 51A to 53A and the first to third electrolytic plating films 51B to 53B, and the etching resist 60 has a size that covers the entire end face 40A of the magnetic resin body 40, the end face 40A of the magnetic resin body 40 does not come into contact with the chemical solution for the etching process. Further, in the present embodiment, since the etching resist 60 protrudes from the outer edge of the magnetic resin body 40 when viewed from the stacking direction, and the end portion of the outer surface 40B of the magnetic resin body 40 is covered with the metal foil 11D, the outer surface 40B of the magnetic resin body 40 also does not come into contact with the chemical solution for the etching process.

[0032] (11) Next, by the SAP method (Semi-Additive Process), the insulating layer 15 and the conductive layer 20 are alternately laminated, and the first and second build-up layers 12A and 12B are formed on both the front and back surfaces of the core substrate 11.

[0033] (12) As shown in FIG. 8A, a solder resist layer 17 is laminated on the outermost conductive layer 20. Next, as shown in FIG. 8B, openings 17H are formed at predetermined positions of the solder resist layer 17 by, for example, laser processing, photolithography processing, or the like. Then, pads 18 are formed on the portions of the outermost conductive layer 20 that are exposed from the solder resist layer 17 due to the openings 17H. Note that only the side of the first build-up layer 12A is shown in the figure.

[0034] (13) Solder bumps 19 are formed on the pads 18 of the first and second build-up layers 12A and 12B (see FIG. 1). Thus, the wiring substrate 10 is completed.

[0035] The description of the structure and manufacturing method of the wiring substrate 10 of this embodiment is as above. Next, the effects of the wiring substrate 10 will be described. According to the wiring substrate 10 of this embodiment, by covering the entire end face 40A of the magnetic resin body 40 with the through-hole land 33A, when the conductive layer 13 including the through-hole land 33A is formed by etching, the end face 40A of the magnetic resin body 40 is prevented from coming into contact with the chemical solution, and the components of the magnetic resin body 40 are prevented from eluting into the chemical solution. Thereby, a decrease in the magnetism of the magnetic resin body 40 can be suppressed more effectively than in the conventional case. Further, since the composition of the chemical solution during etching does not change, the quality of the wiring substrate 10 is stabilized.

[0036] Also, in this embodiment, since the through-hole land 33A protrudes from the outer edge of the magnetic resin body 40, even if, for example, the conductive layer 13 overlapping the outer edge portion of the etching resist 60 is removed, elution of the components of the magnetic resin body 40 into the chemical solution can be suppressed.

[0037] Furthermore, in the present embodiment, in addition to the end face 40A of the magnetic resin body 40, the outer face 40B is also covered with the metal foil 11D, so that the magnetic resin body 40 does not come into contact with the chemical solution during etching. Thereby, the magnetism of the magnetic resin body 40 can be stabilized.

[0038] [Other Embodiments] In the above embodiment, the outer edge of the through-hole land 33A protruded beyond the outer edge of the magnetic resin body 40. However, the present invention is not limited to this. For example, as shown in FIG. 9, the outer edge of the through-hole land 33A may be sized to substantially overlap with the outer edge of the end face 40A of the magnetic resin body 40.

[0039] In the above embodiment, the conductive layer 13 had the metal foil 11D, but a configuration without the metal foil 11D may be employed. In that case, for example, the plurality of magnetic resin bodies 40 are formed such that their end faces are substantially flush with the front and back surfaces of the insulating layer 11K. While the end face 40A is covered with the plating layer 50, the outer face 40B is covered with the insulating layer 11K, thereby achieving the same effect as in the above embodiment.

[0040] Although specific examples of the technology included in the claims are disclosed in this specification and the drawings, the technology described in the claims is not limited to these specific examples. It also includes various modifications and changes of the specific examples, as well as those obtained by extracting a part from the specific examples alone.

Description of Reference Numerals

[0041] 10 Wiring Substrate 11 Core Substrate 11D Metal Foil 11H Body Hole (Through-Hole) 11S Laminate (Base Material Layer) 13 Conductive Layer 31, 32 Through-Hole Conductor 33A Through-Hole Land 40 Magnetic Resin Body 40A End Face 40B Outer Face 50 Plating Film 60 Etching Resist

Claims

1. A base material layer in which a plurality of through holes are formed; A magnetic resin body filling each of the through holes; A through hole conductor penetrating each of the magnetic resin bodies; A wiring board including a through hole land covering the entire end face of each of the magnetic resin bodies.

2. The wiring board according to Claim 1, wherein an outer edge of the end face of the magnetic resin body and an outer edge of the through hole land are substantially overlapped.

3. The wiring board according to Claim 2, wherein the through hole land and the magnetic resin body are circular in plan view, and an outer diameter of the through hole land is substantially equal to an outer diameter of the magnetic resin body.

4. The wiring board according to Claim 1, wherein the through hole land projects beyond an outer edge of the magnetic resin body.

5. The wiring board according to Claim 4, wherein the base material layer includes an insulating layer and metal foils laminated on both front and back surfaces of the insulating layer, and each of the magnetic resin bodies has an end face flush with the metal foil and is covered with a plating film constituting the through hole land, and an outer surface thereof is covered with a metal foil constituting the through hole land.

6. The wiring board according to any one of Claims 1 to 5, wherein the through hole land includes an electroless plating film and an electrolytic plating film.

7. A plurality of through holes are drilled in a base material layer; the plurality of through holes are filled with a plurality of magnetic resin bodies; a through hole conductor penetrating each of the magnetic resin bodies is formed; a conductive layer including a through hole land connected to the through hole conductor is formed, and a manufacturing method of a wiring board including: a conductive film is formed on both front and back surfaces of the base material layer; an etching resist is laminated on the conductive film so as to cover the entire end face of the magnetic resin body as viewed from the lamination direction; a portion of the conductive film laminated on the base material layer that is exposed from the etching resist is etched to form the conductive layer.

8. The manufacturing method of a wiring board according to Claim 7, wherein the etching resist is formed so as to project beyond an outer edge of the magnetic resin body as viewed from the lamination direction.

9. The manufacturing method of a wiring board according to Claim 8, wherein as the base material layer, one in which metal foils are laminated on both front and back surfaces of an insulating layer is prepared, and the end faces of the plurality of magnetic resin bodies are formed to be flush with the metal foils on both front and back surfaces of the base material layer. The plurality of magnetic resin bodies are etched in a state where the end faces are covered with the conductive film including the electroless plating film and the electrolytic plating film, and the outer surfaces are covered with the metal foil.

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