Wiring boards and mounting structures

Abstract

The present invention provides a wiring board that reduces crack formation and delamination of the conductor layer even under loads such as thermal stress. [Solution] The wiring board according to this disclosure includes an insulating layer having a first surface and a second surface located opposite to the first surface, a first groove recessed from the first surface toward the second surface and having a width of 10 μm or less, a second groove recessed from the first surface toward the second surface and having a width of 15 μm or more, and a conductor layer including a first wiring conductor and a second wiring conductor. The first wiring conductor is located in the first groove, and the second wiring conductor is located in the second groove. The first groove has a bottom surface or a first curved portion between the side surface and the bottom surface. The second groove has a bottom surface or a second curved portion between the side surface and the bottom surface. The minimum radius of curvature of the second curved portion is greater than the minimum radius of curvature of the first curved portion.

Description

Technical Field

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

Background Art

[0002] In a wiring board, the conductor layer may be located on the surface of the insulating layer or, as described in Patent Documents 1 and 2, may be located in a groove provided on the surface of the insulating layer. Embedded wiring in which the conductor layer is located in a groove provided on the surface of the insulating layer includes a portion having a relatively wide width and a portion having a relatively narrow width.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] In a wiring board having embedded wiring, cracks are likely to occur in the wiring board or the conductor layer having a relatively wide width is likely to peel off due to a load such as thermal stress.

[0005] An object of the present disclosure is to provide a wiring board in which the occurrence of cracks and the peeling of the conductor layer are reduced even under a load such as thermal stress.

Means for Solving the Problems

[0006] The wiring board according to this disclosure includes an insulating layer having a first surface and a second surface located opposite to the first surface, a first groove recessed from the first surface toward the second surface and having a width of 10 μm or less, a second groove recessed from the first surface toward the second surface and having a width of 15 μm or more, and a conductor layer including a first wiring conductor and a second wiring conductor. The first wiring conductor is located in the first groove, and the second wiring conductor is located in the second groove. The first groove has a bottom surface or a first curved portion between the side surface and the bottom surface. The second groove has a bottom surface or a second curved portion between the side surface and the bottom surface. The minimum radius of curvature of the second curved portion is greater than the minimum radius of curvature of the first curved portion.

[0007] The implementation structure relating to this disclosure includes the above-mentioned wiring board and electronic components mounted on the wiring board. [Effects of the Invention]

[0008] The wiring board relating to this disclosure has the configuration described in the section on means for solving the problem, thereby reducing the occurrence of cracks and delamination of the conductor layer even under loads such as thermal stress. [Brief explanation of the drawing]

[0009] [Figure 1] This is an explanatory diagram illustrating a wiring board according to one embodiment of the present disclosure. [Figure 2] Figure 1 is an enlarged diagram illustrating an example of the arrangement of conductor layers included in a wiring board. [Figure 3] Figure 2 is an explanatory diagram illustrating the cross-section when the line AA is used for cutting. [Figure 4] This is an explanatory diagram illustrating the minimum radius of curvature of the first curved section and the minimum radius of curvature of the second curved section. [Figure 5] Figures 5A to 5E are explanatory diagrams illustrating one embodiment of a method for forming the first and second wiring conductors. [Modes for carrying out the invention]

[0010] A wiring board according to one embodiment of the present disclosure will be described with reference to Figure 1. Figure 1 is an explanatory diagram for illustrating a wiring board 10 according to one embodiment of the present disclosure. The wiring board 10 according to one embodiment comprises a core layer and a build-up layer. The core layer includes a core insulating layer 1, a core conductor layer 2, and a through-hole conductor.

[0011] In the wiring board 10, the core layer is located approximately in the center of the thickness direction of the wiring board 10. The core layer includes a core insulating layer 1 and a core conductor layer 2, as described above.

[0012] The insulating layer 1 for the core is not particularly limited as long as it is made of an insulating material. Examples of insulating materials include resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin, as well as glass. Only one of these insulating materials may be used, or two or more may be used in combination. The thickness of the insulating layer 1 for the core is not particularly limited and may be, for example, 100 μm or more and 1.2 mm or less.

[0013] The core insulating layer 1 may contain a reinforcing material. Examples of reinforcing materials include insulating fabrics such as glass fibers, glass nonwoven fabrics, aramid nonwoven fabrics, aramid fibers, and polyester fibers. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the core insulating layer 1 may contain dispersed inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0014] Core conductor layers 2 are located on both sides of the core insulating layer 1. The core conductor layer 2 is not particularly limited as long as it is made of a conductive material. Examples of conductive materials include metals such as copper. The thickness of the core conductor layer 2 is not limited and may be, for example, 10 μm or more and 50 μm or less. In Figure 1, the core conductor layer 2 is located on both sides of the core insulating layer 1, but it is sufficient if it is located on at least one side of the core insulating layer 1.

[0015] As shown in FIG. 1, through-hole conductors are located in the core insulating layer 1. The through-hole conductors electrically connect the upper and lower surfaces of the core insulating layer 1. The through-hole conductors are part of the core conductor layer 2 and are located in through-holes that penetrate from the upper surface to the lower surface of the core insulating layer 1. The through-hole conductors are not particularly limited as long as they are made of a conductive material. Examples of conductive materials include metals such as copper. The through-hole conductors are connected to the core conductor layer 2 formed on both surfaces of the core insulating layer 1. The through-hole conductors may be located only on the inner wall surface of the through-hole or may be filled in the through-hole. The through-hole conductors may be made of the same metal as the core conductor layer 2 or may be made of a different metal.

[0016] The wiring board 10 according to one embodiment includes a core layer (core insulating layer 1 and core conductor layer 2), but the core layer is not an essential member. For example, a substrate called a coreless substrate does not include a core layer.

[0017] The build-up layers are located on the upper and lower surfaces of the core layer. The build-up layer has a structure in which an insulating layer 3 and a conductor layer 4 are laminated. In the build-up layer, the insulating layer 3 corresponds to the build-up insulating layer, and the conductor layer 4 corresponds to the build-up conductor layer. The simple descriptions of "insulating layer" and "conductor layer" are for the purpose of including embodiments in which the wiring board according to the present disclosure does not include a core layer as described above.

[0018] The insulating layer 3 has a first surface 3a and a second surface 3b. In this specification, "the first surface 3a of the insulating layer 3" means the surface farther from the center in the thickness direction of the wiring board 10 among the two surfaces of the insulating layer 3. "The second surface 3b of the insulating layer 3" means the surface opposite to the first surface 3a, that is, the surface closer to the center in the thickness direction of the wiring board 10. In the wiring board 10, the first surface 3a is the surface farther from the core insulating layer 1, and the second surface 3b is the surface closer to the core insulating layer 1.

[0019] The insulating layer 3 is not particularly limited as long as it is a material having insulating properties. Examples of materials 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 insulating layers 3 may be the same resin or different resins. The insulating layer 3 and the core insulating layer 1 may be the same resin or different resins. The thickness of the insulating layer 3 is not particularly limited, and may be, for example, 10 μm or more and 50 μm or less. The insulating layers 3 may have the same thickness or different thicknesses.

[0020] Inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide may be dispersed in the insulating layer 3. The inorganic insulating fillers may be used alone or in combination of two or more.

[0021] The conductor layer 4 is not particularly limited as long as it is a material having conductivity. Examples of materials having conductivity include metals such as copper. The conductor layer 4 may contain a seed layer 4a described later. The seed layer 4a is located on the surface of the insulating layer 3 in order to improve the adhesion of the conductor layer 4 to the insulating layer 3. The seed layer 4a contains, for example, metals such as nichrome, copper, titanium, and alloys thereof. When the seed layer 4a is located, the seed layer 4a is regarded as a part of the conductor layer 4. The thickness of the seed layer 4a is not limited, and may be, for example, 0.1 μm or more and 1 μm or less. The above-described core conductor layer 2 may also contain the seed layer 4a.

[0022] The insulating layer 3 contains via-hole conductors, which electrically connect the upper and lower surfaces of the insulating layer 3. The via-hole conductors are part of the conductor layer 4 and are located within via holes that penetrate the upper and lower surfaces of the insulating layer 3. The via-hole conductors are not particularly limited as long as they are made of a conductive material. Examples of conductive materials include metals such as copper. The via-hole conductors are connected to the conductor layer 4. The via-hole conductors may be filled inside the via holes or may be located only on the inner surface of the via holes. The via-hole conductors may be made of the same metal as the conductor layer 4 or of a different metal.

[0023] As shown in Figure 1, a solder resist 5 may be located on the surface of the wiring board 10. The solder resist 5 is made of resin, and examples of the resin include acrylic-modified epoxy resin. The solder resist 5 is provided with openings to electrically connect the conductive layer 4 located on the surface of the build-up layer to the electrodes of the electronic component 7 via solder 6. Examples of the electronic component 7 include semiconductor integrated circuit elements and optoelectronic elements.

[0024] As shown in Figure 2, the conductor layer 4 includes a first wiring conductor 41 having a relatively narrow wiring width and a second wiring conductor 42 having a relatively wide wiring width. Figure 2 is an enlarged explanatory diagram illustrating an example of the arrangement of the conductor layer 4 included in the wiring board 10 shown in Figure 1. The first wiring conductor 41 may be, for example, a signal conductor. The second wiring conductor 42 may be, for example, a ground conductor.

[0025] As shown in Figure 3, the first wiring conductor 41 is located in the first groove 31 contained in the insulating layer 3. Figure 3 is an explanatory diagram illustrating the cross-section when cut along the line AA shown in Figure 2. The first groove 31 is recessed from the first surface 3a to the second surface 3b of the insulating layer 3 and has a width of 10 μm or less. Therefore, the first wiring conductor 41 located in the first groove 31 also has a width of 10 μm or less.

[0026] As shown in Figure 3, the second wiring conductor 42 is located in the second groove 32 contained in the insulating layer 3. The second groove 32 is recessed from the first surface 3a to the second surface 3b of the insulating layer 3 and has a width of 15 μm or more. Therefore, the second wiring conductor 42 located in the second groove 32 also has a width of 15 μm or more.

[0027] The first groove 31 has a first curved portion 31a between its bottom surface or between its side surface and bottom surface. Figure 3 shows the first curved portion 31a located on the bottom surface of the first groove 31. The second groove 32 has a second curved portion 32a between its bottom surface or between its side surface and bottom surface. Figure 3 shows the second curved portion 32a located on the bottom surface of the first groove 31 and located between the side surface and bottom surface of the second groove 32.

[0028] As shown in Figure 4, in the wiring board 10, the second minimum radius of curvature r2, which is the minimum radius of curvature of the second curved section 32a, is larger than the first minimum radius of curvature r1, which is the minimum radius of curvature of the first curved section 31a. Figure 4 is an explanatory diagram for illustrating the minimum radius of curvature of the first curved section 31a and the minimum radius of curvature of the second curved section 32a. The radius of curvature is expressed as the reciprocal of the curvature, and the smaller the radius of curvature, the sharper the curve. The minimum radius of curvature of the first curved section 31a (first minimum radius of curvature r1) means the radius of curvature of the part of the first curved section 31a where the curve is sharpest. The minimum radius of curvature of the second curved section 32a (second minimum radius of curvature r2) means the radius of curvature of the part of the second curved section 32a where the curve is sharpest.

[0029] If the second minimum radius of curvature r2 is larger than the first minimum radius of curvature r1, the occurrence of cracks and delamination of the conductor layer 4 (first wiring conductor 41 and second wiring conductor 42) are reduced even when thermal stress or the like is applied. In other words, even if the first curved section 31a is a relatively sharp curve, if the second curved section 32a is a relatively gentle curve, the occurrence of cracks and delamination of the conductor layer 4 (first wiring conductor 41 and second wiring conductor 42) are reduced even when thermal stress or the like is applied. The radius of curvature is measured, for example, by taking an image of the cross-section in the depth direction of the first groove 31 or the second groove 32 using a metallurgical microscope or the like, and drawing an approximate circle on the first curved section 31a or the second curved section 32a from the image, as shown in Figure 4.

[0030] When a load such as thermal stress caused by the difference in thermal expansion coefficients between the insulating layer 3 and the conductive layer 4 is applied to the substrate, cracks are likely to occur in the insulating layer 3 starting from the curved portion, or delamination may occur between the insulating layer 3 and the conductive layer 4. The thermal stress caused by the difference in thermal expansion coefficients between the insulating layer 3 and the conductive layer 4 increases as the width of the conductive layer 4 increases. The thermal stress applied to the first curved portion 31a and the second curved portion 32a is concentrated as the first minimum radius of curvature r1 and the second minimum radius of curvature r2 are small, and is relieved as the first minimum radius of curvature r1 and the second minimum radius of curvature r2 are large.

[0031] As a result, for example, if the first minimum radius of curvature r1 and the second minimum radius of curvature r2 are the same, cracks and delamination due to thermal stress, etc., are more likely to occur as the width of the conductor layer 4 increases, and less likely to occur as the width of the conductor layer 4 decreases. Therefore, by making the minimum radius of curvature (second minimum radius of curvature r2) of the second curved portion 32a of the wide second wiring conductor 42 relatively large, the occurrence of cracks and delamination originating from the second curved portion 32a can be effectively reduced.

[0032] On the other hand, in grooves with a narrow width, such as the first groove 31, it is difficult to ensure sufficient depth while also making the curvature gentle. If the groove is too shallow, it becomes impossible to ensure sufficient thickness for the first wiring conductor 41, resulting in excessively high electrical resistance for the first wiring conductor 41. Therefore, in the wiring board 10, the first curved portion 31a of the narrow first groove 31 has a minimum radius of curvature that ensures sufficient depth to prevent the electrical resistance of the first wiring conductor 41 from becoming excessively high.

[0033] In the narrow first wiring conductor 41, the thermal stress generated is small. Therefore, even if the minimum radius of curvature of the first curved portion 31a (first minimum radius of curvature r1) is small, the risk of cracking and delamination is low. By reducing the first minimum radius of curvature r1, the depth of the first groove 31 can be secured, and the electrical resistance of the first wiring conductor 41 can be reduced. On the other hand, the minimum radius of curvature of the second curved portion 32a of the wider second groove 32 (second minimum radius of curvature r2) is made larger than the first minimum radius of curvature r1, thereby securing the depth of the second groove 32 and sufficiently reducing delamination of the second wiring conductor 42.

[0034] The minimum radius of curvature of the first curved portion 31a may be, for example, 1 μm or more and 2 μm or less. When the minimum radius of curvature of the first curved portion 31a is 1 μm or more and 2 μm or less, the thickness of the first wiring conductor 41 is sufficiently ensured, and the occurrence of cracks in the insulating layer 3 originating from the first curved portion 31a is further reduced.

[0035] The minimum radius of curvature of the second curved portion 32a may be, for example, 3 μm or more and 6 μm or less. When the minimum radius of curvature of the second curved portion 32a is 3 μm or more and 6 μm or less, the shielding effect on the adjacent first wiring conductor 41 is sufficiently exerted, and the stress is sufficiently distributed in the second curved portion 32a. As a result, delamination of the second wiring conductor 42 and the occurrence of cracks in the insulating layer 3 are further reduced.

[0036] The first grooves 31 may have the same width as long as they have a width of 10 μm or less, or they may have different widths. For example, the first grooves 31 may include narrow first grooves 311 having a width of less than 5 μm and wide first grooves 312 having a width of 5 μm or more and 10 μm or less.

[0037] If the first groove 31 includes a narrow first groove 311 and a wide first groove 312, the wide first groove 312 may be deeper than the narrow first groove 311. The depth of the first groove 31 and the second groove 32 refers to the length (depth) from the first surface 3a of the insulating layer 3 to the bottom surface closest to the second surface 3b.

[0038] The depth of the first groove 31 may be 5 μm or more and 15 μm or less. For example, the depth of the narrow first groove 311 may be 4 μm or more and 6 μm or less, and the depth of the wide first groove 312 may be 7 μm or more and 15 μm or less. The difference between the depth of the narrow first groove 311 and the depth of the wide first groove 312 may be, for example, 1 μm or more and 10 μm or less. If the wide first groove 312 is deeper than the narrow first groove 311, the electrical resistance of the first wiring conductor 41 in the wide first groove 312 will be reduced.

[0039] The second groove 32 may be deeper than the first groove 31, and the depth of the second groove 32 may be, for example, 12 μm or more and 20 μm or less. The second groove 32 has a wider width than the first groove 31, and the second groove 32 can be made deeper than the first groove 31.

[0040] The minimum radius of curvature of the first curved portion 31a in the narrow first groove 311 may be smaller than the minimum radius of curvature of the first curved portion 31a in the wide first groove 312. For example, the minimum radius of curvature of the first curved portion 31a in the narrow first groove 311 may be 1 μm or more and 1.5 μm or less, and the minimum radius of curvature of the first curved portion 31a in the wide first groove 312 may be 1.5 μm or more and 2 μm or less. The difference between the minimum radius of curvature of the first curved portion 31a in the narrow first groove 311 and the minimum radius of curvature of the first curved portion 31a in the wide first groove 312 may be, for example, 0.5 μm or more and 1 μm or less. If the minimum radius of curvature of the first curved portion 31a in the narrow first groove 311 is smaller than the minimum radius of curvature of the first curved portion 31a in the wide first groove 312, it becomes easier to ensure the depth of the narrow first groove 311.

[0041] Next, an embodiment of a method for forming the first wiring conductor 41 and the second wiring conductor 42 in the insulating layer 3 will be described with reference to Figures 5A to 5E. Figures 5A to 5E are explanatory diagrams illustrating an embodiment of a method for forming the first wiring conductor 41 and the second wiring conductor 42.

[0042] First, an insulating layer 3 is prepared as shown in Figure 5A. The insulating layer 3 is as described above, so a detailed explanation is omitted. When an inorganic insulating filler is dispersed in the insulating layer 3, the inorganic insulating filler may have an average particle diameter of 0.2 μm or less and a maximum particle diameter of 2 μm or less. The content of the inorganic insulating filler is not limited, and for example, it may be included in a proportion of 70% by mass or more. By including such an inorganic insulating filler in a proportion of 70% by mass or more, for example, the difference between the thermal expansion coefficient of the insulating layer 3 and the thermal expansion coefficient of the conductor layer 4 can be made smaller, and furthermore, the first groove 31 and the second groove 32 can be formed with greater precision. The insulating layer 3 may or may not contain a reinforcing material such as glass cloth. The first groove 31 and the second groove 32 can be formed with greater precision if the insulating layer 3 does not contain a reinforcing material.

[0043] Next, as shown in Figure 5B, a first groove 31 and a second groove 32 are formed in the insulating layer 3. Specifically, the first groove 31 and the second groove 32 are formed by irradiating the insulating layer 3 from the first surface 3a toward the second surface 3b with a laser. The depth of the first groove 31 and the second groove 32, and the first curved portion 31a and the second curved portion 32a are appropriately designed by adjusting the energy distribution of the laser light, focus, output, and number of shots. Examples of lasers include excimer lasers, YAG lasers, and carbon dioxide lasers.

[0044] After laser irradiation, the insulating layer 3 may be subjected to desmear treatment. Examples of desmear treatments include chemical desmearing and plasma desmearing.

[0045] The inclination angle θ of the inner wall surface of the first groove 31 and the inner wall surface of the second groove 32 is not limited and may be, for example, 75° or more and 85° or less. The inclination angle θ is the angle between the planar direction P of the insulating layer 3 and the inner wall surface of the first groove 31 and the inner wall surface of the second groove 32, as shown in Figure 5B.

[0046] After forming the first groove 31 and the second groove 32, a seed layer 4a is formed on the first surface 3a of the insulating layer 3, the inner wall surface of the first groove 31, and the inner wall surface of the second groove 32, as shown in Figure 5C. The seed layer 4a is formed, for example, by electroless plating and sputtering. When the seed layer 4a is formed by electroless plating, for example, copper is used. When the seed layer 4a is formed by sputtering, for example, nichrome, copper, titanium, and alloys thereof are used. The seed layer 4a has a thickness of, for example, 0.1 μm to 1 μm.

[0047] Next, an electroplated layer 4b is formed on the surface of the seed layer 4a, as shown in Figure 5D. The electroplated layer 4b is formed, for example, by electroplating copper. The electroplated layer 4b may be formed with a thickness that extends beyond the first groove 31 and the second groove 32, or it may be formed to extend beyond each of the first groove 31 and the second groove 32 with a thickness of 2 μm to 20 μm.

[0048] Next, as shown in Figure 5E, the unnecessary portion of the electroplating layer 4b is removed, the first wiring conductor 41 is formed in the first groove 31, and the second wiring conductor 42 is formed in the second groove 32. The unnecessary portion of the electroplating layer 4b is removed by polishing, for example, chemical mechanical polishing (CMP).

[0049] In CMP, the plated portions are preferentially polished, so the electroplated layers 4b located on the first groove 31 and the second groove 32 are more easily polished than the electroplated layer 4b located on the first surface 3a. Therefore, the surface of the first wiring conductor 41 located in the first groove 31 and the surface of the second wiring conductor 42 located in the second groove 32 may not be flush with the first surface 3a, but may be located within the first groove 31 and the second groove 32, respectively. In this way, if the surfaces of the first wiring conductor 41 and the second wiring conductor 42 are recessed from the first surface 3a, the adhesion of other insulating layers 3 located on the first surface 3a is further improved. The depth of the recess is not limited; for example, it may be between 0.2 μm and 2 μm from the first surface 3a.

[0050] After CMP, the surfaces of the first wiring conductor 41 and the second wiring conductor 42 may be subjected to a roughening treatment. Examples of roughening treatments include CZ treatment. By performing the roughening treatment, the adhesion of other insulating layers 3 located on the first surface 3a is further improved.

[0051] Next, the mounting structure according to this disclosure will be described with reference to Figure 1. The mounting structure 20 according to one embodiment includes a wiring board 10 according to one embodiment and an electronic component 7 located in the mounting area of ​​the wiring board 10.

[0052] Figure 1 shows a state in which the wiring board 10 and the electronic component 7 are not connected. By connecting the electronic component connection pad (part of the conductor layer 4) exposed from an opening in the solder resist 5 located on one surface of the wiring board 10 to the electrodes of the electronic component 7 via solder 6, a mounting structure 20 according to one embodiment is obtained. Examples of electronic components 7 include semiconductor integrated circuit elements and optoelectronic elements. In the mounting structure 20 according to one embodiment, electronic components 7 may also be connected via solder 6 to other pads (part of the conductor layer 4) exposed from openings in the solder resist 5 located on the other surface of the wiring board 10. Alternatively, a motherboard, for example, may be connected to other pads of the wiring board 10 via solder 6.

[0053] The embodiments of this disclosure have been described above. However, the invention relating to this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible within the scope of this disclosure as shown in (1) to (5) below.

[0054] (1) The wiring board according to the present disclosure includes an insulating layer having a first surface and a second surface located opposite to the first surface, a first groove recessed from the first surface toward the second surface and having a width of 10 μm or less, a second groove recessed from the first surface toward the second surface and having a width of 15 μm or more, and a conductor layer including a first wiring conductor and a second wiring conductor. The first wiring conductor is located in the first groove, and the second wiring conductor is located in the second groove. The first groove has a bottom surface or a first curved portion between the side surface and the bottom surface. The second groove has a bottom surface or a second curved portion between the side surface and the bottom surface. The minimum radius of curvature of the second curved portion is greater than the minimum radius of curvature of the first curved portion. (2) In the wiring board described in (1) above, the minimum radius of curvature of the first curved portion is 1 μm or more and 2 μm or less, and the minimum radius of curvature of the second curved portion is 3 μm or more and 6 μm or less. (3) In the wiring board described in (1) or (2) above, the first groove includes a narrow first groove having a width of less than 5 μm and a wide first groove having a width of 5 μm or more and 10 μm or less, wherein the wide first groove is deeper than the narrow first groove. (4) In the wiring board described in (3) above, the minimum radius of curvature in the narrow first groove is smaller than the minimum radius of curvature in the wide first groove. (5) The implementation structure relating to this disclosure includes a wiring board as described in any of (1) to (4) above, and an electronic component connected to the wiring board. [Explanation of Symbols]

[0055] 1. Insulating layer for core 2 Conductor layers for the core 3. Insulating layer 3a 1st page 3b 2nd side 31 First groove 311 Narrow 1st groove 312 Wide first groove 31a First curved section 32 2nd groove 32a Second curved section 4 Conductor layer 41 First Wiring Conductor 42 Second Wiring Conductor 4a Seed layer 4b Electrolytic plating layer 5 Solder Resist 6 Handa 7 Electronic Components 10 Wiring board 20 Implementation Structures r1 1st minimum radius of curvature r2 Second minimum radius of curvature

Claims

1. An insulating layer having a first surface and a second surface located opposite to the first surface, A first groove that is recessed from the first surface toward the second surface and has a width of 10 μm or less, A second groove that is recessed from the first surface toward the second surface and has a width of 15 μm or more, A conductor layer including a first wiring conductor and a second wiring conductor, Includes, The first wiring conductor is located in the first groove, and the second wiring conductor is located in the second groove. The first groove has a bottom surface or a first curved portion between the side surface and the bottom surface, The second groove has a second curved portion between the bottom surface or the side surface and the bottom surface, The minimum radius of curvature of the second curved portion is greater than the minimum radius of curvature of the first curved portion. Wiring board.

2. The wiring board according to claim 1, wherein the minimum radius of curvature of the first curved portion is 1 μm or more and 2 μm or less, and the minimum radius of curvature of the second curved portion is 3 μm or more and 6 μm or less.

3. The first groove includes a narrow first groove having a width of less than 5 μm and a wide first groove having a width of 5 μm or more and 10 μm or less. The wide first groove is deeper than the narrow first groove. The wiring board according to claim 1.

4. The wiring board according to claim 3, wherein the minimum radius of curvature in the narrow first groove is smaller than the minimum radius of curvature in the wide first groove.

5. A mounting structure comprising a wiring board according to any one of claims 1 to 4 and an electronic component connected to the wiring board.

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