Manufacturing method of wiring boards

Abstract

Providing high-quality wiring boards. [Solution] The method for manufacturing a wiring board according to the embodiment includes forming a laminate 1P including a core substrate 100 having a first surface 100f and a second surface 100s opposite to the first surface 100f, a first build-up portion 10 laminated on the first surface 100f, and a second build-up portion 20 laminated on the second surface 100s, and dividing the laminate 1P into a plurality of wiring boards. Dividing the laminate 1P includes forming a groove GB drilled in the thickness direction of the second build-up portion 20, and cutting the first build-up portion 10 and the core substrate 100 from the first build-up portion 10 toward the groove GB of the second build-up portion 20.

Description

Technical Field

[0006] , ,

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

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a wiring board including cutting a substrate having a metal layer and a resin layer formed on both surfaces (one surface and the other surface) of a glass substrate into a plurality of individual wiring boards along a dicing line using a dicing blade.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for manufacturing a wiring board disclosed in Patent Document 1, it is necessary to cut a glass substrate and metal layers and resin layers laminated on both surfaces of the glass substrate together with a dicing blade, and it is not easy to divide the wiring board. <​​​​​​​​​According to embodiments of the present invention, the laminate can be easily divided into multiple wiring boards. [Brief explanation of the drawing]

[0007] [Figure 1] A cross-sectional view showing an example of a wiring board manufactured by the wiring board manufacturing method of an embodiment of the present invention. [Figure 2A] A cross-sectional view showing an example of a manufacturing method for a wiring board according to an embodiment. [Figure 2B] A cross-sectional view showing an example of a manufacturing method for a wiring board according to an embodiment. [Figure 2C] A cross-sectional view showing an example of a manufacturing method for a wiring board according to an embodiment. [Figure 2D] A cross-sectional view showing an example of a manufacturing method for a wiring board according to an embodiment. [Figure 3A] A cross-sectional view showing an example of a manufacturing method for a wiring board according to an embodiment. [Figure 3B] A cross-sectional view showing an example of a manufacturing method for a wiring board according to an embodiment. [Modes for carrying out the invention]

[0008] A method for manufacturing a wiring board according to an embodiment of the present invention will be described with reference to the drawings. Figure 1 shows a cross-sectional view of wiring board 1, which is an example of a wiring board manufactured by the manufacturing method of the embodiment. Note that wiring board 1 is merely an example of a wiring board manufactured by the manufacturing method of the embodiment. For example, the laminated structure of the manufactured wiring board, and the number of conductor layers and insulating layers contained in the wiring board, may differ from the laminated structure of wiring board 1 in Figure 1, and the number of conductor layers and insulating layers contained in wiring board 1. Also, in the drawings referenced in the following description, certain parts may be enlarged to facilitate understanding of the disclosed embodiment, and the size and length of each component may not be depicted in the exact proportions between them.

[0009] The wiring board 1 is composed of a core substrate 100 and build-up sections 10 and 20, which are made up of insulating layers and conductive layers alternately laminated on both sides of the core substrate 100. The wiring board 1 has two main surfaces perpendicular to its thickness direction: one surface 1F and the other surface 1S opposite to the first surface 1F.

[0010] The core substrate 100 included in the wiring board 1 has a first surface 100f and a second surface 100s opposite to the first surface 100f. On the first surface 100f of the core substrate 100, a first insulating layer 11 and a first conductor layer 12 are alternately laminated to form a first build-up section 10. On the second surface 100s of the core substrate 100, a second insulating layer 21 and a second conductor layer 22 are alternately laminated to form a second build-up section 20.

[0011] In addition, with regard to the description of the wiring board manufactured by the manufacturing method of the embodiment, in the description of the components of the wiring board 1, the side closer to the core substrate 100 is referred to as "bottom," "inside," or "lower side" or "inside," and the side further from the core substrate 100 is referred to as "top," "outside," or "upper side" or "outside." The surface of each element constituting the wiring board 1 that faces the core substrate 100 is also referred to as the "bottom surface," and the surface that faces away from the core substrate 100 is also referred to as the "top surface."

[0012] The core substrate 100 has a through conductor 101 that penetrates the core substrate 100 in the thickness direction. The first insulating layer 11 constituting the first build-up section 10 has a first via conductor 13 that penetrates the first insulating layer 11 in the thickness direction and connects opposing conductors (either two first conductor layers 12 or one first conductor layer 12 and the through conductor 101) that are sandwiched between the first insulating layer 11. The second insulating layer 21 constituting the second build-up section 20 has a second via conductor 23 that penetrates the second insulating layer 21 in the thickness direction and connects opposing conductors (either two second conductor layers 22 or one second conductor layer 22 and the through conductor 101) that are sandwiched between the second insulating layer 21.

[0013] The through-conductor 101 is formed by filling a through-hole 101a formed in the core substrate 100 with a conductor. In the illustrated example, the end face of the through-conductor 101 in the extending direction is formed substantially flush with the surface of the core substrate 100, and constitutes the first surface 100f and the second surface 100s of the core substrate 100. The first via conductor 13 is formed by filling a through-hole 13a formed in the first insulating layer 11 with a conductor. The first via conductor 13 is integrally formed with the first conductor layer 12 that is in contact with the surface of the first insulating layer 11 opposite to the core substrate 100 through which the first via conductor 13 passes. The second via conductor 23 is formed by filling a through-hole 23a formed in the second insulating layer 21 with a conductor. The second via conductor 23 is integrally formed with the second conductor layer 22 that is in contact with the surface of the second insulating layer 21 opposite to the core substrate 100 through which the second via conductor 23 passes.

[0014] The core substrate included in the wiring board manufactured by the manufacturing method of the embodiment may be a glass substrate. The core substrate 100 of the illustrated wiring board 1 is formed using a glass substrate. As the glass material used for the glass substrate constituting the core substrate 100, for example, soda-lime glass, borosilicate glass, or alkali-free glass may be used. These glasses may contain elements such as magnesium, calcium, manganese, aluminum, lead, iron, chromium, potassium, sulfur, antimony, and boron as additives. In addition, the core substrate included in the wiring board may be a substrate containing materials other than glass, such as a silicon substrate, ceramic substrate, or resin substrate.

[0015] The first insulating layer 11 and the second insulating layer 21 are formed using any insulating resin. Examples of insulating resins include thermosetting resins such as epoxy resin, bismaleimide triazine resin (BT resin), or phenolic resin, and thermoplastic resins such as fluororesin, liquid crystal polymer (LCP), fluoroethylene fluorine (PTFE) resin, polyester (PE) resin, and modified polyimide (MPI) resin. The first insulating layer 11 and the second insulating layer 21 may contain inorganic fillers (not shown) such as silica and alumina. The first insulating layer 11 and the second insulating layer 21 may also contain reinforcing materials (core materials) such as glass fibers or aramid fibers.

[0016] Examples of conductors constituting the first conductor layer 12, the second conductor layer 22, the first via conductor 13, the second via conductor 23, and the through conductor 101 include copper and nickel, with copper being preferred. In the example shown in Figure 1, the first conductor layer 12, the second conductor layer 22, the first via conductor 13, the second via conductor 23, and the through conductor 101 are each shown as single layers, but they can be composed of a multilayer structure. The first conductor layer 12, the second conductor layer 22, the first via conductor 13, the second via conductor 23, and the through conductor 101 may have a multilayer structure including, for example, a metal foil layer (preferably copper foil), a metal film layer (preferably a copper film formed by electroless plating or sputtering), and a plating film layer (preferably an electrolytic copper plating film). For example, the first conductor layer 12, the second conductor layer 22, the first via conductor 13, the second via conductor 23, and the through conductor 101 may have a two-layer structure including a metal film layer and a plating film layer.

[0017] Each conductor layer (first conductor layer 12, second conductor layer 22) constituting the wiring board 1 is patterned to have a predetermined conductor pattern. The first conductor layer 12 constituting one side 1F of the wiring board 1 is formed in a pattern having a plurality of conductor pads 12fp. The second conductor layer 22 constituting the other side 1S of the wiring board 1 is formed in a pattern having a plurality of conductor pads 22sp.

[0018] The first build-up portion 10 that constitutes the wiring board 1 includes, on its outermost side, a solder resist layer 10Rf formed using, for example, a photosensitive polyimide resin or an epoxy resin. An opening 10Rfa is formed in the solder resist layer 10Rf, and the conductor pad 12fp is exposed from the opening 10Rfa. That is, one surface 1F of the wiring board 1 includes the surface of the solder resist layer 10Rf and the surface of the conductor pad 12fp exposed from the opening 10Rfa. The second build-up portion 20 that constitutes the wiring board 1 includes, on its outermost side, a solder resist layer 20Rs formed using, for example, a photosensitive polyimide resin or an epoxy resin. An opening 20Rsa is formed in the solder resist layer 20Rs, and the conductor pad 22sp is exposed from the opening 20Rsa. That is, the other surface 1S of the wiring board 1 includes the surface of the solder resist layer 20Rs and the surface of the conductor pad 22sp exposed from the opening 20Rsa.

[0019] One surface 1F of the wiring board 1 in the illustrated example is configured as a component mounting surface to which external electronic components are connected, and the conductor pad 12fp can be connected to the connection pads of external electronic components in the use of the wiring board 1. The other surface 1S of the wiring board 1 can be a connection surface that is connected to an external board when the wiring board 1 is mounted on an external board that is, for example, the motherboard of an arbitrary electrical device. In the use of the wiring board 1, the conductor pad 22sp can be connected to the connection pads of the external board.

[0020] As will be described in detail later, the single wiring board 1 in the illustrated example is formed by dividing a laminate including a plurality of wiring boards 1 and separating them into individual wiring boards 1. The side surface extending in the thickness direction of the wiring board 1 is a surface exposed by separating the laminate into individual wiring boards 1. In a plan view, each individual wiring board 1 has a rectangular shape, and in the above-described laminate, a plurality of wiring boards 1 are connected in a grid pattern. Here, "plan view" means looking at an object with a line of sight parallel to the thickness direction of the wiring board 1. As will be described in detail later, in the process of dividing a laminate in which a plurality of wiring boards 1 are connected into individual wiring boards 1, the groove formed in the second build-up portion 20 in the thickness direction facilitates the cutting of the core substrate 100.

[0021] In the illustrated wiring board 1, the side surface (groove side surface) GS of the second build-up portion 20 extending in the thickness direction of the wiring board 1 is recessed in the direction inside the wiring board 1 with respect to the side surface (cutting surface) CS of the core substrate 100 and the first build-up portion 10. The side surface (groove side surface) GS of the second build-up portion 20 and the side surface (cutting surface) CS of the core substrate 100 and the first build-up portion 10 do not overlap, and the shape in which the side surface of this second build-up portion 20 is recessed with respect to the side surfaces of the core substrate 100 and the first build-up portion 10 can be formed as a result of the process of separating the laminate, which will be described later.

[0022] Subsequently, referring to FIGS. 2A to 2D and FIGS. 3A to 3B, taking as an example the case where the wiring board 1 shown in FIG. 1 is manufactured, the manufacturing method of the wiring board according to the embodiment will be described. In addition, in each component formed in the manufacturing method of the wiring board described below, unless otherwise specified, the materials exemplified as the materials of the corresponding components in the description of the wiring board 1 in FIG. 1 can be used for formation. Further, in FIGS. 2A to 3B referred to below, the metal film layer and the plating film layer, which are components of each conductor layer, are not drawn, and each conductor layer is drawn as a single layer as in FIG. 1.

[0023] The manufacturing method of the wiring board of this embodiment includes forming a laminate including a core substrate and first and second build-up portions formed on both sides of the core substrate, and dividing the laminate into a plurality of wiring boards. Here, "laminated body" refers to a state in which a plurality of wiring boards to be divided into individual pieces by dicing or scribing are connected. First, Figures 2A to 2D will be shown to explain the formation of the laminate.

[0024] As shown in Figure 2A, a core substrate 100 is formed. In forming the core substrate 100, first, a glass substrate 100P is prepared, which may include, for example, soda-lime glass, borosilicate glass, or alkali-free glass. Through holes 101a are formed in the glass substrate 100P. In forming the through holes 101a, for example, a modified area may be formed in the glass substrate 100P at the location where the through holes 101a are to be formed by irradiation with laser light, and the through holes 101a may be formed by removing the modified area with, for example, an etching solution containing an aqueous solution of hydrogen fluoride. As the laser light that forms the modified area, helium-neon lasers, argon ion lasers, excimer lasers, and various YAG lasers may be used.

[0025] Next, the interior of the formed through-hole 101a is completely filled with a conductor, and the conductor is formed to completely cover two surfaces of the glass substrate 100P that are perpendicular to the thickness direction. In forming the conductor, a metal film layer (not shown) is formed on the inner wall surface of the through-hole 101a and on the two surfaces of the glass substrate 100P, for example by electroless plating, and then a plating film layer (not shown) is formed on the metal film layer by electroplating using the metal film layer as a power supply layer. A through-conductor 101 having the metal film layer and the plating film layer is formed, and the two surfaces of the glass substrate 100P are covered with a two-layer structure of conductors consisting of the metal film layer and the plating film layer. Subsequently, the conductor layers covering both sides of the glass substrate 100P are removed, for example by CMP (chemical mechanical polishing). As shown in Figure 2A, a core substrate 100 having a first surface 100f and a second surface 100s is formed.

[0026] The core substrate 100 that is formed includes a plurality of wiring board forming regions BA corresponding to a plurality of connected wiring boards 1 to be manufactured.

[0027] Next, as shown in Figure 2B, a first insulating layer 11 is laminated to cover the first surface 100f of the core substrate 100, and then a first conductor layer 12 is formed on top of the first insulating layer 11. Simultaneously with the formation of the first conductor layer 12, a first via conductor 13 is formed integrally with the first conductor layer 12. The first insulating layer 11 is laminated over a plurality of wiring board formation regions BA, and the first conductor layer 12 and the first via conductor 13 are formed in the plurality of wiring board formation regions BA. A second insulating layer 21 is formed to cover the second surface 100s of the core substrate 100, and then a second conductor layer 22 is formed on top of the second insulating layer 21. Simultaneously with the formation of the second conductor layer 22, a second via conductor 23 is formed integrally with the second conductor layer 22. The second insulating layer 21 is laminated over a plurality of wiring board formation regions BA, and the second conductor layer 22 and the second via conductor 23 are formed in the plurality of wiring board formation regions BA.

[0028] The first insulating layer 11 and the second insulating layer 21 can be formed by thermocompression bonding of a film-like insulating resin (e.g., epoxy resin) onto the surface (first surface 100f and second surface 100s) of the core substrate 100. A through-hole 13a is formed in the first insulating layer 11 at the position where the first via conductor 13 is to be formed, for example by irradiation with carbon dioxide laser light. The first conductor layer 12 and the first via conductor 13 are formed on the inner surface of the through-hole 13a and the upper surface of the first insulating layer 11 by electroless plating or sputtering, and by electroplating a plating film (not shown) using a plating resist with appropriate openings and using the metal film layer as a power supply layer. A through-hole 23a is formed in the second insulating layer 21 at the position where the second via conductor 23 is to be formed, for example by irradiation with carbon dioxide laser light. The second conductor layer 22 and the second via conductor 23 are formed by forming a metal film layer (not shown) on the inner surface of the through hole 23a and the upper surface of the second insulating layer 21 by electroless plating or sputtering, and by forming a plating film (not shown) by electroplating using a plating resist having appropriate openings and using the metal film layer as a power supply layer.

[0029] Next, as shown in Figure 2C, on the upper side of the first surface 100f of the core substrate 100, the same process as the formation of the first insulating layer 11 and the integral formation of the first via conductor 13 and the first conductor layer 12 described above is repeated a desired number of times to form a desired number of first insulating layers 11 and first conductor layers 12. Also, on the upper side of the second surface 100s, the same process as the formation of the second insulating layer 21 and the integral formation of the second via conductor 23 and the second conductor layer 22 described above is repeated a desired number of times to form a desired number of second insulating layers 21 and second conductor layers 22. The outermost first conductor layer 12 is formed in a pattern including a conductor pad 12fp. The outermost second conductor layer 22 is formed in a pattern including a conductor pad 22sp.

[0030] Next, as shown in Figure 2D, a solder resist layer 10Rf is formed over multiple wiring board formation regions BA on the outermost first conductor layer 12 and first insulating layer 11 on the first surface 100f side of the core substrate 100, having an opening 10Rfa that exposes the conductor pad 12fp. The formation of the first build-up section 10 is completed. On the outermost second conductor layer 22 and second insulating layer 21 on the second surface 100s side of the core substrate 100, a solder resist layer 20Rs is formed over multiple wiring board formation regions BA, having an opening 20Rsa that exposes the conductor pad 22sp. The formation of the second build-up section 20 is completed. The formation of a laminate 1P in which multiple wiring boards 1, each having one surface 1F and the other surface 1S opposite to the one surface 1F, are connected is completed.

[0031] Next, with reference to Figures 3A to 3B, the process of dividing the formed laminate 1P into individual wiring boards 1 will be described. In the manufacturing method of the wiring board of this embodiment, dividing the laminate includes forming a groove that penetrates the second build-up portion in the thickness direction, and cutting the first build-up portion and the core substrate from the first build-up portion toward the groove of the second build-up portion.

[0032] First, as shown in Figure 3A, grooves GB are formed along the boundary BD between the multiple wiring boards 1 in the laminate 1P, creating the second build-up portion 20 in the thickness direction. The grooves GB can be formed, for example, by irradiating laser light, such as a carbon dioxide laser, from the outside of the second build-up portion 20 toward the laminate 1P. The grooves GB may also be formed by cutting the second build-up portion 20 along the boundary BD using a blade, such as a diamond blade in which diamond abrasive grains are embedded in resin, which can be used for general dicing or scribing. The grooves GB can be formed over the entire rectangular periphery of each individual wiring board 1 in plan view.

[0033] In the illustrated example, the groove GB is formed as a groove that penetrates partway through the second build-up portion 20 in the thickness direction, and a portion of the second insulating layer 21 is exposed at the bottom surface of the groove GB. That is, the groove GB is formed such that a portion of the second insulating layer 21 remains as a thin layer. In this case, high precision in the thickness direction when forming the groove GB is not required, and the formation of the groove GB becomes easier. The thickness GBt (see Figure 1) from the bottom surface of the groove GB to the core substrate 100 is preferably smaller than the thickness 21t (see Figure 1) of one of the multiple second insulating layers 21 (for example, the second insulating layer 21 adjacent to the core substrate 100). For example, the thickness GBt from the bottom surface of the groove GB to the core substrate 100 can be 0.3 to 40 μm. The groove GB may penetrate the second build-up portion 20, and the second surface 100s of the core substrate 100 may be exposed at its bottom surface. Furthermore, when forming the groove GB with a laser as described above, in order to mitigate the damage the laser inflicts on the glass, a metal film layer formed by electroless plating or sputtering, which constitutes the second conductive layer 22, may be provided on the boundary BD between the bottom surface of the groove GB and the second surface 100s of the core substrate 100. In this case, the metal film layer may be exposed in the groove GB. The metal film layer formed by electroless plating or sputtering provided on the boundary BD is preferably a thin metal film of 1 μm or less and is in contact with the second surface 100s of the core substrate 100. Furthermore, the metal film layer may be covered by the bottom surface of the groove GB of the second insulating layer 21. Note that if the bottom surface of the groove GB is not flat, the thickness GBt from the bottom surface of the groove GB to the core substrate 100 can be the average value of values ​​measured at at least three locations in the width direction (left-right direction in Figure 1) of the groove GB.

[0034] Next, as shown in Figure 3B, the first build-up portion 10 and the core substrate 100 are cut along the groove GB, from the first build-up portion 10 toward the groove GB. For example, the dicing blade DB cuts the first build-up portion 10, the core substrate 100, and a portion of the second insulating layer 21 of the second build-up portion 20, and as the dicing blade DB reaches the bottom surface of the groove GB, the laminate 1P is broken down into individual wiring boards 1. The cutting of the first build-up portion 10 and the core substrate 100 can be performed by a cutting member capable of cutting the first build-up portion 10 and the core substrate 100 in the thickness direction, and the cutting member may be a dicing blade DB or another cutting member (cutter) such as a scriber.

[0035] In the manufacturing method of the wiring board of this embodiment, grooves GB are formed in the second build-up section 20 before the core board 100 and the first build-up section 10 are cut. Therefore, when the core board 100 is cut by a cutting member such as a dicing blade DB, stress is concentrated near the bottom surface of the pre-formed grooves GB. This stress concentration is thought to promote cutting near the bottom surface of the grooves GB, making it easier to cut the core board 100. Therefore, it becomes possible to easily divide the laminate 1P into multiple wiring boards.

[0036] In the illustrated example, as described above, the groove GB is formed as a groove that penetrates partway through the second build-up portion 20 in the thickness direction, and a portion of the second insulating layer 21 is exposed at the bottom of the groove GB. In this case, since a portion of the second insulating layer 21 remains as a thin layer, when the core substrate 100 is cut by a cutting member such as a dicing blade DB, it is thought that the second insulating layer 21 is cut due to stress concentration in the thin portion of the second insulating layer 21 after the cutting member has penetrated the core substrate 100. Therefore, it is thought that the laminate 1P can be easily divided into multiple wiring boards, and damage to the core substrate 100 is suppressed.

[0037] In the illustrated example, the width DBw of the cutting member (dicing blade DB in the embodiment) is smaller than the opening width GBw of the groove GB. In this case, even if the cutting member, such as the dicing blade DB, is misaligned in the width direction of the groove GB (left-right direction in Figure 3B), the cutting member is more likely to fit within the groove GB. Therefore, the core substrate 100 is less likely to be divided at an unintended position due to relative misalignment between the cutting member and the groove GB. However, the width DBw of the cutting member may be the same as the opening width GBw of the groove GB, or it may be larger than the opening width GBw of the groove GB.

[0038] In the illustrated example of a wiring board manufacturing method, the dicing blade DB continuously cuts the solder resist layer 10Rf and multiple first insulating layers 11 constituting the first build-up section 10, the core substrate 100, and the second insulating layer 21 constituting the bottom surface of the groove GB. When the core substrate 100 is exposed at the bottom surface of the groove GB, the dicing blade DB continuously cuts the solder resist layer 10Rf and multiple first insulating layers 11 constituting the first build-up section 10, as well as the core substrate 100. When a metal film layer is exposed at the bottom surface of the groove GB, the dicing blade DB continuously cuts the solder resist layer 10Rf, multiple first insulating layers 11 constituting the first build-up section 10, the core substrate 100, and the metal film layer.

[0039] As a result of cutting the core substrate 100 and the first build-up section 10, the manufacturing of the individualized wiring board 1 is completed, as shown in Figure 1. [Explanation of symbols]

[0040] 1 Wiring board 10. First Build-up Department 20. Second Build-up Department 11. Insulating layer (first insulating layer) 21. Insulating layer (second insulating layer) 12 Conductor layer (First conductor layer) 22 Conductor layer (second conductor layer) 13 Via conductor (first via conductor) 23 Via conductor (2nd via conductor) 100 core boards 101 Through-conductor 12fp conductor pad 22sp Conductor Pad BA wiring board formation area BD boundary DB Dicing Blade GB Groove

Claims

1. To form a laminate including a core substrate having a first surface and a second surface opposite to the first surface, a first build-up portion laminated on the first surface, and a second build-up portion laminated on the second surface, Dividing the aforementioned laminate into multiple wiring boards, A method for manufacturing a wiring board, including, Dividing the laminate includes forming a groove in the thickness direction of the second build-up portion and cutting the first build-up portion and the core substrate from the first build-up portion toward the groove of the second build-up portion.

2. A method for manufacturing a wiring board according to claim 1, wherein the core substrate includes a glass substrate.

3. A method for manufacturing a wiring board according to claim 1, wherein forming the laminate includes forming the first build-up portion to include a plurality of first insulating layers, and cutting the first build-up portion and the core substrate includes cutting the plurality of first insulating layers and the core substrate.

4. A method for manufacturing a wiring board according to claim 1, wherein forming the laminate further includes forming the first build-up portion including a solder resist layer, and dividing the laminate includes cutting the solder resist layer.

5. A method for manufacturing a wiring board according to claim 1, wherein forming the groove portion includes exposing the core substrate on the bottom surface of the groove portion.

6. A method for manufacturing a wiring board according to claim 1, wherein forming the laminate includes forming the second build-up portion to include a plurality of second insulating layers, and forming the groove includes exposing a portion of the plurality of second insulating layers on the bottom surface of the groove.

7. A method for manufacturing a wiring board according to claim 6, wherein the thickness from the bottom surface of the groove to the core substrate is 0.3 to 40 μm.

8. A method for manufacturing a wiring board according to claim 1, wherein the width of the cutting member for cutting the first build-up portion and the core board is smaller than the opening width of the groove portion.

9. A method for manufacturing a wiring board according to claim 1, wherein the groove side surface of the second build-up portion that defines a part of the groove portion does not overlap with the core substrate and the cut surface of the first build-up portion.

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