Wiring substrate and mounting structure using the same

Abstract

To provide a wiring substrate in which cracks that occur in an insulating resin layer directly below an opening corner of a solder resist are reduced.SOLUTION: A wiring substrate according to the present disclosure includes a first insulating layer having a first surface, a first conductor layer located on the first surface and including electrode sections, and a solder resist positioned to cover the first surface and the first conductor layer. When viewed in plan view, the solder resist has an opening that exposes the entire electrode sections. The opening has a corner, and the first conductor layer is positioned directly below at least the corner.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure relates to a wiring board and a mounting structure using the same.

Background Art

[0002] For pads for mounting electronic components on a wiring board, there are, for example, two types: an NSMD (Non Solder Mask Defined) structure and an SMD (Solder Mask Defined) structure as described in Patent Document 1. Since solder is also joined to the side surface of the pad having the NSMD structure, the joining strength is improved. Conventionally, the opening of the solder resist for exposing the pad having the NSMD structure is arranged such that the opening edge is located on the insulating resin layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] In recent years, a highly filled filler resin has been adopted as the insulating resin layer. However, the highly filled filler resin has low toughness. Therefore, when the pad has an NSMD structure, the stress caused by the expansion and contraction of the solder resist tends to concentrate on the insulating resin layer directly under the opening corner of the solder resist. As a result, cracks are likely to occur in the insulating resin layer directly under the opening corner of the solder resist.

[0005] An object of the present disclosure is to provide a wiring board capable of reducing cracks generated in the insulating resin layer directly under the opening corner of the solder resist.

Means for Solving the Problems

[0006] The wiring board according to the present disclosure includes a first insulating layer having a first surface, a first conductor layer located on the first surface and including an electrode portion, and a solder resist located so as to cover the first surface and the first conductor layer. When viewed in plan, the solder resist has an opening that exposes the entire electrode portion. The opening has corners, and the first conductor layer is located at least directly below the corners.

[0007] The mounting structure according to the present disclosure includes the above wiring board and an electronic component connected to the electrode portion included in this wiring board.

Advantages of the Invention

[0008] By having a configuration as described in the section of means for solving the problems, the wiring board according to the present disclosure can reduce cracks generated in the insulating resin layer directly below the opening corners of the solder resist.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

MODE FOR CARRYING OUT THE INVENTION

[0010] A wiring board according to an embodiment of the present disclosure will be described with reference to FIGS. 1A to 1D. FIG. 1A is a plan view of a main part of a wiring board 10 according to an embodiment of the present disclosure. The wiring board 10 shown in FIG. 1A includes, for example, a core layer and a build-up layer.

[0011] The core layer is located substantially at the center in the thickness direction of the wiring board 10. The core layer includes a core insulating layer and a core conductor layer. The core insulating layer is not particularly limited as long as it is a material having insulating properties. Examples of the material having insulating properties include resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin. These resins may be used alone or in combination of two or more. The thickness of the core insulating layer is not particularly limited, and may be, for example, 0.1 mm or more and 2.0 mm or less.

[0012] The core insulating layer may contain a reinforcing material. Examples of the reinforcing material include insulating cloth materials such as glass fiber, glass non-woven fabric, aramid non-woven fabric, aramid fiber, and polyester fiber. The reinforcing material may be used alone or in combination of two or more. Further, inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide may be dispersed in the core insulating layer. The inorganic insulating fillers may be used alone or in combination of two or more.

[0013] The conductor layer for the core is located on the surface of the insulating layer for the core. The conductor layer for the core is not particularly limited as long as it is a material having conductivity. Examples of the material having conductivity include metals such as copper. The thickness of the conductor layer for the core is not particularly limited, and is, for example, 5 μm or more and 50 μm or less.

[0014] In the insulating layer for the core, through-hole conductors are located in order to electrically connect the upper and lower surfaces of the insulating layer for the core. The through-hole conductors are located in the through-holes penetrating the upper and lower surfaces of the insulating layer for the core. The through-hole conductors are formed of a metal such as copper, for example, similar to the conductor layer for the core. The through-hole conductors may be formed only on the inner wall surface, or may be filled in the through-holes. The through-hole conductors are connected to the conductor layer for the core on the surface of the insulating layer for the core.

[0015] The build-up layer is located on one or both sides of the core layer. The build-up layer has a structure in which at least one insulating layer for build-up and at least one conductor layer for build-up are laminated.

[0016] The insulating layer for build-up is not particularly limited as long as it is a material having insulating properties, similar to the insulating layer for the core. Examples of the material having insulating properties include resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin. These resins may be used alone or in combination of two or more.

[0017] The insulating layers for build-up may be the same resin or different resins. The insulating layer for build-up and the insulating layer for the core may be the same resin or different resins. The thickness of the insulating layer for build-up is not particularly limited, and may be, for example, 10 μm or more and 50 μm or less. The insulating layers for build-up may have the same thickness or different thicknesses.

[0018] The insulating layer for build-up may contain a reinforcing material. Examples of the reinforcing material include insulating cloth materials such as glass fiber, glass non-woven fabric, aramid non-woven fabric, aramid fiber, and polyester fiber. Only one type of reinforcing material may be used, or two or more types may be used in combination. Further, inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide may be dispersed in the insulating layer for build-up. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0019] The build-up conductor layer is not limited as long as it is a conductor such as a metal. Specifically, the build-up conductor layer is formed of a metal foil such as a copper foil, or a metal plating such as copper plating. The thickness of the build-up conductor layer is not particularly limited, and may be, for example, 5 μm or more and 25 μm or less.

[0020] In the insulating layer for build-up, via hole conductors are located to electrically connect the upper and lower surfaces of the insulating layer for build-up. The via hole conductors are located in via holes penetrating the upper and lower surfaces of the insulating layer for build-up. The via hole conductors are formed of, for example, a metal plating such as copper plating. The via hole conductors are connected to the build-up conductor layers located on both surfaces of the insulating layer for build-up. The via hole conductors may be filled in the via holes, or may be located only on the inner surface of the via holes.

[0021] As shown in FIGS. 1A and 1B, among the insulating layers (insulating layers for build-up) included in the wiring substrate 10, the insulating layer located on the outermost surface corresponds to the first insulating layer 1. FIG. 1B is an explanatory diagram showing a cross section when cut along line A-A shown in FIG. 1A. The first insulating layer 1 has a first surface 11. In the present specification, the "first surface 11 of the first insulating layer 1" means the surface farther from the central portion (core layer) of the wiring substrate 10, that is, the upper surface of the first insulating layer 1, among the two surfaces of the first insulating layer 1.

[0022] As shown in FIGS. 1A and 1B, among the conductor layers (conductor layers for build-up) included in the wiring board 10, the conductor layer located on the outermost surface, that is, the conductor layer located on the first surface 11 of the first insulating layer 1, corresponds to the first conductor layer 2.

[0023] The first conductor layer 2 includes an electrode portion 21. The electrode portion 21 is a conductor for electrically connecting the wiring board 10 and the electronic component. The electrode portion 21 can be defined as, for example, the two rectangular portions shown in FIG. 1A. Examples of the electronic component include surface-mounted passive elements such as chip capacitors and chip inductors, semiconductor integrated circuit elements, and optoelectronic elements.

[0024] A solder resist 3 is located on the outermost surface of the wiring board 10. Specifically, the solder resist 3 is located so as to cover the first surface 11 of the first insulating layer 1 and the first conductor layer 2. The solder resist 3 may be located on at least one surface layer of the wiring board 10. The solder resist 3 is formed of a resin, and examples of the resin include acrylic-modified epoxy resin.

[0025] An opening 31 is provided in the solder resist 3 for electrically connecting the electrode portion 21 and the electrode of the electronic component. That is, as shown in FIG. 1A, when viewed in plan, the solder resist 3 has an opening 31 that exposes the entire electrode portion 21. The opening 31 of the solder resist 3 has a polygonal shape such as a rectangular shape when viewed in plan, and includes a corner portion 31a and a side portion 31b.

[0026] The stress due to the curing shrinkage of the solder resist 3 tends to concentrate at the corner portion 31a of the opening 31. Therefore, in the first insulating layer 1, cracks are likely to occur at positions overlapping the corner portion 31a of the opening 31 of the solder resist 3.

[0027] In the wiring board 10, in the opening 31 of the solder resist 3, the first conductor layer 2 is located directly below the corner portion 31a. Therefore, even if stress due to the curing shrinkage of the solder resist 3 is concentrated, the first conductor layer 2 having relatively large toughness serves as a barrier, and the stress applied to the first insulating layer 1 is reduced. As a result, cracks generated in the first insulating layer 1 are reduced.

[0028] In FIG. 1A, in the first conductor layer 2 located directly below the corner portion 31a, the portion exposed in the opening 31 has a triangular shape. However, the shape of this portion is not limited to a triangular shape and may be any shape. The shape of this portion may be an L-shaped as shown in FIG. 1C, or may be a fan-shaped as shown in FIG. 1D. FIGS. 1C and 1D are enlarged explanatory views for explaining a modified example of the region W shown in FIG. 1A. As long as the first conductor layer 2 is located directly below the corner portion 31a, the stress applied to the first insulating layer 1 is reduced regardless of the shape of the exposed portion.

[0029] Next, a wiring board according to another embodiment of the present disclosure will be described with reference to FIGS. 2A to 2D. FIG. 2A is a plan view of a main part in the wiring board 20 according to another embodiment of the present disclosure. FIG. 2B is an explanatory view showing a cross section when cut along the line B-B shown in FIG. 2A. The wiring board 20 shown in FIG. 2A also includes, for example, a core layer and a build-up layer, similar to the wiring board 10. In the wiring board 20, the same members as those in the wiring board 10 are denoted by the same reference numerals, and detailed descriptions are as described above and will be omitted.

[0030] In the wiring board 10 shown in FIG. 1A, the first conductor layer 2 is located only directly below the corner portion 31a of the opening 31. On the other hand, in the wiring board 20 shown in FIG. 2, the first conductor layer 2 is located not only directly below the corner portion 31a of the opening 31 but also directly below the side portion 31b of the opening 31. That is, the first conductor layer 2 is located directly below the peripheral edge portion (corner portion 31a and side portion 31b) of the opening 31.

[0031] Also in the wiring board 20, since the first conductor layer 2 is positioned at least directly below the corner 31a of the opening 31, even if stress due to the curing shrinkage of the solder resist 3 concentrates, the first conductor layer 2 having relatively large toughness serves as a barrier. As a result, the stress applied to the first insulating layer 1 is reduced, and cracks generated in the first insulating layer 1 are reduced.

[0032] In FIG. 2A, in the first conductor layer 2 positioned directly below the corner 31a of the opening 31, the portion exposed in the opening 31 has an angular shape. However, the shape of this portion is not limited and may be any shape. The shape of this portion may have a curved shape as shown in FIG. 2C, or may be chamfered as shown in FIG. 2D. FIGS. 2C and 2D are enlarged explanatory views for explaining modified examples of the region X shown in FIG. 2A. If the first conductor layer 2 is positioned directly below the corner 31a, the stress applied to the first insulating layer 1 is reduced regardless of the shape of the exposed portion.

[0033] Next, a wiring board according to still another embodiment of the present disclosure will be described with reference to FIGS. 3A to 3D. FIG. 3A is a plan view of a main part of a wiring board 30 according to another embodiment of the present disclosure. FIG. 3B is an explanatory view showing a cross section when cut along the line C-C shown in FIG. 3A. The wiring board 30 shown in FIG. 3A also includes, for example, a core layer and a build-up layer, similar to the wiring board 10. In the wiring board 30, the same members as those in the wiring board 10 are denoted by the same reference numerals, and detailed descriptions are as described above and will be omitted.

[0034] In the wiring board 10 shown in FIG. 1A, the first conductor layer 2 is positioned directly below the corner 31a of the opening 31. This first conductor layer 2 is electrically connected to the electrode portion 21 and is derived from a grounding conductor positioned so as to surround the electrode portion 21. On the other hand, in the wiring board 30 shown in FIG. 3, although the first conductor layer 2 is positioned directly below the corner 31a of the opening 31, the first conductor layer 2 positioned directly below the corner 31a is not a conductor derived from a grounding conductor. In the wiring board 30, the first conductor layer 2 positioned directly below the corner 31a of the opening 31 is a dummy conductor 22. The dummy conductor 22 is included in the first conductor layer 2 and is not electrically connected to the electrode portion 21.

[0035] Also in the wiring board 30, since the dummy conductor 22 included in the first conductor layer 2 is located at least directly below the corner portion 31a of the opening 31, even if stress due to the curing shrinkage of the solder resist 3 is concentrated, the first conductor layer 2 having relatively large toughness serves as a barrier. As a result, the stress applied to the first insulating layer 1 is reduced, and cracks generated in the first insulating layer 1 are reduced.

[0036] In FIG. 3A, in the first conductor layer 2 located directly below the corner portion 31a, the portion exposed in the opening 31 has a triangular shape. However, the shape of this portion is not limited to a triangular shape and may be any shape. The shape of this portion may be an L-shaped as shown in FIG. 3C, or may be a fan-shaped as shown in FIG. 3D. FIGS. 3C and 3D are enlarged explanatory views for explaining a modified example of the region Y shown in FIG. 3A. As long as the first conductor layer 2 is located directly below the corner portion 31a, the stress applied to the first insulating layer 1 is reduced regardless of the shape of the exposed portion.

[0037] Next, a wiring board according to still another embodiment of the present disclosure will be described with reference to FIGS. 4A to 4D. FIG. 4A is a plan view of a main part of a wiring board 40 according to another embodiment of the present disclosure. FIG. 4B is an explanatory view showing a cross section when cut along the line D-D shown in FIG. 4A. The wiring board 40 shown in FIG. 4A also includes, for example, a core layer and a build-up layer, similar to the wiring board 40. In the wiring board 40, the same members as those in the wiring board 40 are denoted by the same reference numerals, and detailed description is as described above and will be omitted.

[0038] In the wiring board 10 shown in FIG. 1A, the first conductor layer 2 is positioned directly below the corner 31a of the opening 31. On the other hand, in the wiring board 40 shown in FIG. 4, although the first conductor layer 2 is positioned directly below the corner 31a of the opening 31, the corner 31a has a convex shape protruding in a direction away from the electrode portion 21. When the corner 31a has a convex shape, as shown in FIG. 4A, the first conductor layer 2 is positioned directly below the tip of the convex shape. Thereby, it becomes possible to increase the distance between the electrode portion 21 and the first conductor layer 2 of the corner 31a, and it becomes possible to improve the electrical insulation.

[0039] If the first conductor layer 2 is positioned directly below the corner 31a of the opening 31, the shape of the corner 31a is not limited, and as shown in FIG. 4A, it may have a convex shape. The tip of the convex shape may have an arc shape as shown in FIG. 4A, or may have an angular shape as shown in FIGS. 4C and 4D. FIGS. 4C and 4D are enlarged explanatory views for explaining a modified example of the region Z shown in FIG. 4A.

[0040] In the first conductor layer 2 positioned directly below the corner 31a, the shape of the portion exposed in the opening 31 is not limited and may be any shape. The shape of this portion may be a rounded shape as shown in FIG. 4A, an L-shaped shape as shown in FIG. 4C, or a valley shape as shown in FIG. 4D according to the shape of the tip of the convex shape. If the first conductor layer 2 is positioned directly below the corner 31a, the stress applied to the first insulating layer 1 is reduced regardless of the shape of the exposed portion.

[0041] The manufacturing method of the wiring boards 10, 20, 30, 40 according to the above-described embodiments is not limited. For example, when laminating the solder resist 3, the opening 31 of the solder resist 3 may be formed in accordance with the shape of each embodiment.

[0042] Next, in FIG. 5, the mounting structure 100 according to the present disclosure will be described. The mounting structure 100 according to one embodiment includes a wiring board 10 according to one embodiment and an electronic component E located in the mounting area of the wiring board 10. The wiring board 10 and the electronic component E are connected such that an electrode portion 21 located on the surface of the wiring board 10 and an electrode E1 of the electronic component E are connected via, for example, solder H. The electrode portion 21 is exposed from an opening 31 of a solder resist 3 located on the surface of the wiring board 10. Examples of the electronic component E include surface-mount passive elements such as chip capacitors and chip inductors, semiconductor integrated circuit elements, and optoelectronic elements. In the mounting structure 100 according to one embodiment, the electronic components E may be located on both sides of the wiring board 10. The electronic components E may be located on one surface, and, for example, a motherboard or the like may be located on the other surface.

[0043] The embodiments of the present disclosure have been described above. However, the invention according to the present disclosure is not limited to the above-described embodiments, and various changes and improvements can be made within the scope of the present disclosure shown in the following (1) and (5).

[0044] (1) The wiring board according to the present disclosure includes a first insulating layer having a first surface, a first conductor layer located on the first surface and including an electrode portion, and a solder resist located so as to cover the first surface and the first conductor layer. In a plan view, the solder resist has an opening that exposes the entire electrode portion. The opening has a corner portion, and the first conductor layer is located at least directly below the corner portion.

[0045] Regarding the embodiments of the present disclosure, the embodiments shown in the following (2) to (4) are further disclosed.

[0046] (2) In the wiring board according to (1) above, the first conductor layer is located directly below the peripheral edge portion of the opening of the solder resist. (3) In the wiring board according to (1) or (2) above, the first conductor layer includes a dummy conductor that is not electrically connected to the electrode portion, and the dummy conductor is located directly below the corner portion. (4) In the wiring board according to any one of (1) to (3) above, the corner portion has a convex shape protruding in a direction away from the electrode portion.

[0047] (5) The mounting structure according to the present disclosure includes the wiring board according to any one of (1) to (4) above and an electronic component connected to the electrode portion included in this wiring board.

Description of Reference Numerals

[0048] 1 First insulating layer 11 First surface 2 First conductor layer 21 Electrode portion 22 Dummy conductor 3 Solder resist 31 Opening 31a Corner portion 31b Side portion 10, 20, 30, 40 Wiring board

Claims

1. A first insulating layer having a first surface; A first conductor layer located on the first surface and including an electrode portion; A solder resist located so as to cover the first surface and the first conductor layer; Comprising; When viewed in plan view, the solder resist has an opening that exposes the entire electrode portion; The opening has a corner portion, and the first conductor layer is located at least directly below the corner portion; A wiring board.

2. The wiring board according to claim 1, wherein the first conductor layer is located directly below the peripheral edge of the opening of the solder resist.

3. The wiring board according to claim 1, wherein the first conductor layer includes a dummy conductor not electrically connected to the electrode portion, and the dummy conductor is located directly below the corner portion.

4. The wiring board according to claim 1, wherein the corner portion has a convex shape protruding in a direction away from the electrode portion.

5. A mounting structure including the wiring board according to any one of claims 1 to 4 and an electronic component connected to the electrode portion included in the wiring board.

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