Wiring board and manufacturing method of wiring board

Abstract

To provide a wiring substrate and a manufacturing method of the wiring substrate, which improve connection reliability between wiring layers.SOLUTION: In a cross section including a center line C1 of an upper edge 413 of a via hole 412 in a plan view when an object is viewed from a normal direction of one surface of a core layer, in a wiring substrate, a front surface of a concave part 215 includes: a first point 11 located at an edge of the concave part; and a second point located on the center line. When a portion between the first point and the second point is approximated to a curve having only one inflection point 19, an angle θ1 of a first angle between a first line segment 21 connecting the first point and the third point 13 and a second surface is smaller than 90 degrees, an angle θ2 of a second angle between a second line segment 22 connecting the third point and a fourth point 14 and the first line segment is larger than 90 degrees, and an angle θ3 of the third angle between a third line segment connecting a fourth point and the second point and the second line segment is larger than 90 degrees. The third point is a point at which a curvature is maximized between the first point and an inflection point, and the fourth point is a point at which a curvature is maximized between the second point and the inflection point.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a wiring board and a method for manufacturing a wiring board. [Background technology]

[0002] Conventionally, when manufacturing a wiring board, an insulating layer covering a wiring layer is formed, a via hole is formed in the insulating layer, a desmear process is performed, and then another wiring layer is formed in the via hole and on the insulating layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-244127 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for improved connection reliability between wiring layers.

[0005] An object of the present disclosure is to provide a wiring board and a method for manufacturing a wiring board that can improve connection reliability between wiring layers. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, there is provided a semiconductor device including: a first wiring layer having a first surface on which a recess is formed; an insulating layer having a second surface opposite to the first surface and covering the first wiring layer; a via hole that overlaps the first wiring layer in a plan view and penetrates the insulating layer; and a second wiring layer that is formed on the insulating layer and contacts the first wiring layer through the via hole, wherein in a cross section including a center line of an upper edge of the via hole in a plan view, a surface of the recess includes a first point located on the edge of the recess and a second point located on the center line, and the first point and the second point on the surface of the recess are spaced apart from each other. is approximated to a curve with only one inflection point, a first angle between a first line segment connecting the first point and a third point and the second surface is smaller than 90 degrees, a second angle between a second line segment connecting the third point and a fourth point and the first line segment is larger than 90 degrees, a third angle between a third line segment connecting the fourth point and the second point and the second line segment is larger than 90 degrees, the third point is the point where the curvature is maximum between the first point and the inflection point, and the fourth point is the point where the curvature is maximum between the second point and the inflection point. [Effects of the Invention]

[0007] According to the disclosed technique, the connection reliability between wiring layers can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view illustrating a wiring board according to an embodiment; [Figure 2] 1A and 1B are diagrams mainly illustrating the positional relationship between via holes and recesses; [Figure 3] 4A to 4C are cross-sectional views mainly illustrating the shape of a recessed portion. [Figure 4] 1A to 1C are cross-sectional views (part 1) illustrating a method for manufacturing a wiring board according to an embodiment. [Figure 5] 10A and 10B are cross-sectional views (part 2) illustrating the method for manufacturing a wiring board according to the embodiment. [Figure 6] 10A to 10C are cross-sectional views (part 3) illustrating the method for manufacturing a wiring board according to the embodiment. [Figure 7]1A to 1C are cross-sectional views (part 1) illustrating a method for forming a via hole, a recess, and a wiring layer. [Figure 8] 10A and 10B are cross-sectional views (part 2) illustrating a method for forming a via hole, a recess, and a wiring layer. [Figure 9] 10A to 10C are cross-sectional views (part 3) illustrating a method for forming a via hole, a recess, and a wiring layer. DETAILED DESCRIPTION OF THE INVENTION

[0009] To improve the connection reliability between wiring layers, it is conceivable to form a recess on the surface of the wiring layer after forming a via hole, and then form another wiring layer by plating so that it penetrates into the recess. However, when the inventors of the present application manufactured a wiring board using this method, it became clear that the plating solution was not supplied to the edge of the recess, resulting in a gap in the recess. If a gap occurs in the recess, there is a risk that the connection reliability will not be sufficiently improved. Therefore, in order to make it less likely for a gap to occur in the recess, the inventors of the present application conducted further intensive research and came up with the following embodiment.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description may be omitted.

[0011] [Structure of wiring board according to embodiment] First, the structure of the wiring board according to the embodiment will be described. Fig. 1 is a cross-sectional view illustrating the wiring board according to the embodiment.

[0012] 1, a wiring board 1 according to the embodiment includes, for example, a core layer 100, a buildup layer 200 provided on one surface of the core layer 100, and a buildup layer 300 provided on the other surface of the core layer 100. The wiring board 1 may be a coreless substrate that does not include a core layer.

[0013] In this embodiment, for convenience, the buildup layer 200 side is referred to as the upper side or one side, and the buildup layer 300 side is referred to as the lower side or the other side, with the core layer 100 as the reference. The upper surface of each part is referred to as the one side or top surface, and the lower surface is referred to as the other side or bottom surface. However, the wiring board 1 can be used upside down or positioned at any angle. Furthermore, a planar view refers to viewing an object from the normal direction of one surface of the core layer 100, and a planar shape refers to the shape of the object viewed from the normal direction of one surface of the core layer 100.

[0014] The core layer 100 has an insulating substrate 111 in which a plurality of through holes 112 are formed, and a conductive layer 113 formed on the inner wall surface of the through holes 112. For example, the substrate is made of glass epoxy or the like, and the conductive layer 113 is made of copper (Cu) or the like. The core layer 100 may have a filler filled inside the conductive layer 113.

[0015] The buildup layer 200 has wiring layers 210, 230, and 250, insulating layers 410 and 420, and a solder resist layer 260. The buildup layer 300 has wiring layers 310, 330, and 350, insulating layers 510 and 520, and a solder resist layer 360. The insulating layer 410 is provided between the wiring layer 210 and the wiring layer 230 that are adjacent in the thickness direction, and the insulating layer 420 is provided between the wiring layer 230 and the wiring layer 250 that are adjacent in the thickness direction. The insulating layer 510 is provided between the wiring layer 310 and the wiring layer 330 that are adjacent in the thickness direction, and the insulating layer 520 is provided between the wiring layer 330 and the wiring layer 350 that are adjacent in the thickness direction. The insulating layer 410 includes the insulating layer 220 and the adhesion-promoting film 270, and the insulating layer 420 includes the insulating layer 240 and the adhesion-promoting film 280. The insulating layer 510 includes the insulating layer 320 and the adhesion-promoting film 370, and the insulating layer 520 includes the insulating layer 340 and the adhesion-promoting film 380.

[0016] The wiring layer 210 is formed on one surface of the core layer 100. The wiring layer 310 is formed on the other surface of the core layer 100. The wiring layers 210 and 310 are electrically connected to each other by the conductive layer 113. The material of the wiring layers 210 and 310 is, for example, copper (Cu). The thickness of the wiring layers 210 and 310 is, for example, about 10 μm to 30 μm.

[0017] The adhesion-promoting film 270 is formed on one surface and a side surface of the wiring layer 210. The adhesion-promoting film 270 covers one surface and a side surface of the wiring layer 210. The adhesion-promoting film 270 is formed from a material having two types of functional groups with different reactivities in one molecule. The material of the adhesion-promoting film 270 is, for example, a silane coupling agent or a titanium coupling agent. The thickness of the adhesion-promoting film 270 is, for example, about 3 nm to 8 nm.

[0018] In the silane coupling agent, the functional group that chemically bonds with an organic material such as a resin preferably contains an amino group, an epoxy group, a mercapto group, an isocyanate group, a methacryloxy group, an acryloxy group, a ureido group, or a sulfide group. The optimal functional group is selected depending on the type of resin that chemically bonds with the silane coupling agent.

[0019] In the silane coupling agent, the functional group that chemically bonds with inorganic materials such as metals preferably includes an azole group, a silanol group, a methoxy group, or an ethoxy group. The optimal functional group is selected depending on the type of metal that chemically bonds with the silane coupling agent.

[0020] The insulating layer 220 is formed on one surface of the core layer 100 so as to cover the wiring layer 210 and the adhesion-enhancing film 270. The material of the insulating layer 220 is, for example, an insulating resin whose main component is an epoxy resin or a polyimide resin. The thickness of the insulating layer 220 is, for example, approximately 30 μm to 40 μm. The insulating layer 220 may contain a filler such as silica (SiO2). The content of the filler in the insulating layer 220 can be appropriately set depending on the required coefficient of thermal expansion (CTE). The adhesion-enhancing film 270 improves the adhesion between the wiring layer 210 and the insulating layer 220. In other words, when the adhesion-enhancing film 270 is provided, higher adhesion can be obtained between the wiring layer 210 and the insulating layer 220 than when the wiring layer 210 and the insulating layer 220 are in direct contact with each other.

[0021] A recess 215 is formed on one surface of the wiring layer 210. A via hole 412 is formed in the insulating layer 410. The via hole 412 penetrates the insulating layer 410. That is, the via hole 412 penetrates the insulating layer 220 and the adhesion enhancing film 270. The via hole 412 overlaps the wiring layer 210 in a planar view and reaches the wiring layer 210. The via hole 412 overlaps the recess 215 in a planar view and is connected to the recess 215.

[0022] The wiring layer 230 is formed on one surface of the insulating layer 220. The wiring layer 230 includes via conductors in the via holes 412 and the recesses 215, and a wiring pattern on one surface of the insulating layer 220. The wiring pattern of the wiring layer 230 is electrically connected to the wiring layer 210 through the via conductors. The material and thickness of the wiring layer 230 are, for example, the same as those of the wiring layer 210.

[0023] The adhesion-enhancing film 280 is formed on one surface and a side surface of the wiring layer 230. The adhesion-enhancing film 280 covers one surface and a side surface of the wiring layer 230. The material and thickness of the adhesion-enhancing film 280 are the same as those of the adhesion-enhancing film 270, for example.

[0024] The insulating layer 240 is formed on one surface of the insulating layer 220 so as to cover the wiring layer 230 and the adhesion-enhancing film 280. The material and thickness of the insulating layer 240 are, for example, similar to those of the insulating layer 220. The insulating layer 240 may contain a filler such as silica (SiO2). The filler content in the insulating layer 240 is, for example, similar to that of the insulating layer 220. The adhesion-enhancing film 280 improves the adhesion between the wiring layer 230 and the insulating layer 240. In other words, when the adhesion-enhancing film 280 is provided, higher adhesion can be obtained between the wiring layer 230 and the insulating layer 240 than when the wiring layer 230 and the insulating layer 240 are in direct contact with each other.

[0025] A recess 235 is formed on one surface of the wiring layer 230. A via hole 422 is formed in the insulating layer 420. The via hole 422 penetrates the insulating layer 420. That is, the via hole 422 penetrates the insulating layer 240 and the adhesion enhancing film 280. The via hole 422 overlaps the wiring layer 230 in a planar view and reaches the wiring layer 230. The via hole 422 overlaps the recess 235 in a planar view and is connected to the recess 235.

[0026] The wiring layer 250 is formed on one surface of the insulating layer 240. The wiring layer 250 includes via conductors in the via holes 422 and the recesses 235, and a wiring pattern on one surface of the insulating layer 240. The wiring pattern of the wiring layer 250 is electrically connected to the wiring layer 230 through the via conductors. The material and thickness of the wiring layer 250 are, for example, the same as those of the wiring layer 210. An adhesion-enhancing film (not shown) may be formed on one surface and side surfaces of the wiring layer 250.

[0027] The solder resist layer 260 is formed on one surface of the insulating layer 240 so as to cover the wiring layer 250. An opening 261 is formed in the solder resist layer 260. The opening 261 penetrates the solder resist layer 260. The opening 261 overlaps with an electrode pad, which is part of the wiring layer 250, in a plan view, and reaches the electrode pad.

[0028] The adhesion-enhancing film 370 is formed on the other surface and side surfaces of the wiring layer 310. The adhesion-enhancing film 370 covers the other surface and side surfaces of the wiring layer 310. The material and thickness of the adhesion-enhancing film 370 are the same as those of the adhesion-enhancing film 270, for example.

[0029] The insulating layer 320 is formed on the other surface of the core layer 100 so as to cover the wiring layer 310 and the adhesion-enhancing film 370. The material and thickness of the insulating layer 320 are, for example, the same as those of the insulating layer 220. The insulating layer 320 may contain a filler such as silica (SiO2). The filler content in the insulating layer 320 is, for example, the same as that of the insulating layer 220. The adhesion-enhancing film 370 improves the adhesion between the wiring layer 310 and the insulating layer 320. In other words, when the adhesion-enhancing film 370 is provided, higher adhesion can be obtained between the wiring layer 310 and the insulating layer 320 than when the wiring layer 310 and the insulating layer 320 are in direct contact with each other.

[0030] A recess 315 is formed on the other surface of the wiring layer 310. A via hole 512 is formed in the insulating layer 510. The via hole 512 penetrates the insulating layer 510. That is, the via hole 512 penetrates the insulating layer 320 and the adhesion enhancing film 370. The via hole 512 overlaps the wiring layer 310 in a plan view and reaches the wiring layer 310. The via hole 512 overlaps the recess 315 in a plan view and is connected to the recess 315.

[0031] The wiring layer 330 is formed on the other surface of the insulating layer 320. The wiring layer 330 includes via conductors in the via holes 512 and the recesses 315, and a wiring pattern on the other surface of the insulating layer 320. The wiring pattern of the wiring layer 330 is electrically connected to the wiring layer 310 through the via conductors. The material and thickness of the wiring layer 330 are, for example, the same as those of the wiring layer 210.

[0032] The adhesion-enhancing film 380 is formed on the other surface and side surfaces of the wiring layer 330. The adhesion-enhancing film 380 covers the other surface and side surfaces of the wiring layer 330. The material and thickness of the adhesion-enhancing film 380 are the same as those of the adhesion-enhancing film 270, for example.

[0033] The insulating layer 340 is formed on the other surface of the insulating layer 320 so as to cover the wiring layer 330 and the adhesion-enhancing film 380. The material and thickness of the insulating layer 340 are, for example, the same as those of the insulating layer 220. The insulating layer 340 may contain a filler such as silica (SiO2). The filler content in the insulating layer 340 is, for example, the same as that of the insulating layer 220. The adhesion-enhancing film 380 improves the adhesion between the wiring layer 330 and the insulating layer 340. In other words, when the adhesion-enhancing film 380 is provided, higher adhesion can be obtained between the wiring layer 330 and the insulating layer 340 than when the wiring layer 330 and the insulating layer 340 are in direct contact with each other.

[0034] A recess 335 is formed on the other surface of the wiring layer 330. A via hole 522 is formed in the insulating layer 520. The via hole 522 penetrates the insulating layer 520. That is, the via hole 522 penetrates the insulating layer 340 and the adhesion enhancing film 380. The via hole 522 overlaps the wiring layer 330 in a plan view and reaches the wiring layer 330. The via hole 522 overlaps the recess 335 in a plan view and is connected to the recess 335.

[0035] The wiring layer 350 is formed on the other surface of the insulating layer 340. The wiring layer 350 includes via conductors in the via holes 522 and the recesses 335, and a wiring pattern on the other surface of the insulating layer 340. The wiring pattern of the wiring layer 350 is electrically connected to the wiring layer 330 through the via conductors. The material and thickness of the wiring layer 350 are, for example, the same as those of the wiring layer 210. An adhesion-enhancing film (not shown) may be formed on the other surface and side surfaces of the wiring layer 350.

[0036] The solder resist layer 360 is formed on the other surface of the insulating layer 340 so as to cover the wiring layer 350. Openings 361 are formed in the solder resist layer 360. The openings 361 penetrate the solder resist layer 360. The openings 361 overlap with the electrode pads, which are part of the wiring layer 350, in a plan view, and reach the electrode pads.

[0037] Here, the wiring layer 210, the adhesion enhancing film 270, the insulating layer 220, and the wiring layer 230 will be described in more detail. FIG. 2 is a diagram mainly illustrating the positional relationship between the via hole 412 and the recess 215. FIG. 3 is a cross-sectional view mainly illustrating the shape of the recess 215. FIG. 3 corresponds to a cross-sectional view taken along line III-III in FIG. 2.

[0038] 2 and 3, the recess 215 is formed in an upper surface 211, which is one surface of the wiring layer 210. The insulating layer 410 has a lower surface 411, which is the other surface. The lower surface 411 of the insulating layer 410 faces the upper surface 211 of the wiring layer 210. The upper surface 211 of the wiring layer 210 is an example of a first surface, and the lower surface 411 of the insulating layer 410 is an example of a second surface.

[0039] The via hole 412 has an opening 222 formed in the insulating layer 220 and an opening 272 formed in the adhesion enhancing film 270. The opening 222 may be a recessed portion having an inverted truncated cone shape. That is, the opening diameter at the upper end of the opening 222 may be larger than the opening diameter at the lower end. The opening 272 connects the opening 222 and the recess 215. The opening diameter of the opening 272 is larger than the opening diameter at the lower end of the opening 222. Furthermore, the opening diameter at the upper end of the recess 215 is larger than the opening diameter of the opening 272. Therefore, in a plan view, the opening 272 is located inside the upper end of the recess 215, and the lower end of the opening 222 is located inside the opening 272.

[0040] As will be described later, the recess 215 can be formed by wet etching. The surface of the recess 215, which is part of the upper surface 211, may have minute irregularities due to wet etching. In Figure 3 and other figures, the minute irregularities on the surface of the recess 215 are omitted. Figure 3 shows a cross section including the center line C1 of the upper edge 413 of the via hole 412 in a plan view. In this cross section, the surface of the recess 215 includes a first point 11 located on the edge of the recess 215 and a second point 12 located on the center line C1.

[0041] Furthermore, when the portion of the surface of recess 215 between first point 11 and second point 12 is approximated to a curve with only one inflection point, recess 215 includes a third point 13 where the curvature is maximum between first point 11 and inflection point 19, and a fourth point 14 where the curvature is maximum between second point 12 and inflection point 19.

[0042] The first angle between the first line segment 21 connecting the first point 11 and the third point 13 and the lower surface 411 of the insulating layer 410 is an acute angle, the second angle between the first line segment 21 and the second line segment 22 connecting the third point 13 and the fourth point 14 is an obtuse angle, and the third angle between the second line segment 22 and the third line segment 23 connecting the fourth point 14 and the second point 12 is an obtuse angle. That is, the angle θ1 of the first angle is smaller than 90 degrees, the angle θ2 of the second angle is larger than 90 degrees, and the angle θ3 of the third angle is larger than 90 degrees.

[0043] Thus, the surface of the recess 215 has, on both sides of the center line C1, a first inclined portion that gradually deepens from the first point 11 to the second point 12, a second inclined portion that steeply deepens from the first inclined portion, and a third inclined portion that gradually deepens from the second inclined portion. Roughly speaking, the first inclined portion corresponds to the portion between the first point 11 and the third point 13, the second inclined portion corresponds to the portion between the third point 13 and the fourth point 14, and the third inclined portion corresponds to the portion between the fourth point 14 and the second point 12.

[0044] The wiring layer 230 contacts the surface of the recess 215, the portion of the lower surface 411 of the insulating layer 410 exposed in the recess 215, the inner wall surface of the via hole 412, and one surface of the insulating layer 410. The wiring layer 230 has a seed layer 236 and a plating layer 237. The seed layer 236 directly covers the surface of the recess 215, the portion of the lower surface 411 of the insulating layer 410 exposed in the recess 215, the inner wall surface of the via hole 412, and one surface of the insulating layer 410. The plating layer 237 is provided on the seed layer 236. The seed layer 236 and the plating layer 237 are made of copper (Cu) or the like.

[0045] The insulating layer 410 has a first region 31 whose thickness is 2 μm or less based on the portion of the lower surface 411 exposed in the recess 215. The first region 31 has a second region 32 including the inner wall surface of the via hole, and a third region 33 connected to the second region 32 and located between the second region 32 and the first point 11 in a planar view. The second region 32 and the third region 33 include the insulating layer 220, and the third region 33 includes the adhesion-promoting film 270, but the second region 32 does not include the adhesion-promoting film 270. Therefore, when the insulating layer 220 includes a filler and the adhesion-promoting film 270 does not include a filler, the density of the filler in the second region 32 is higher than the density of the filler in the third region 33.

[0046] The wiring layer 230, the adhesion enhancing film 280, the insulating layer 240, and the wiring layer 250 are also stacked one upon another, similar to the wiring layer 210, the adhesion enhancing film 270, the insulating layer 220, and the wiring layer 230. The wiring layer 310, the adhesion enhancing film 370, the insulating layer 320, and the wiring layer 330 are also stacked one upon another, similar to the wiring layer 210, the adhesion enhancing film 270, the insulating layer 220, and the wiring layer 230. The wiring layer 330, the adhesion enhancing film 380, the insulating layer 340, and the wiring layer 350 are also stacked one upon another, similar to the wiring layer 210, the adhesion enhancing film 270, the insulating layer 220, and the wiring layer 230.

[0047] In the relationship between the wiring layers 210 and 230, the wiring layer 210 is an example of a first wiring layer, and the wiring layer 230 is an example of a second wiring layer. In the relationship between the wiring layers 230 and 250, the wiring layer 230 is an example of a first wiring layer, and the wiring layer 250 is an example of a second wiring layer. In the relationship between the wiring layers 310 and 330, the wiring layer 310 is an example of a first wiring layer, and the wiring layer 330 is an example of a second wiring layer. In the relationship between the wiring layers 330 and 350, the wiring layer 330 is an example of a first wiring layer, and the wiring layer 350 is an example of a second wiring layer.

[0048] [Method of manufacturing a wiring board according to an embodiment] Next, a method for manufacturing the wiring board 1 according to the embodiment will be described. Figures 4 to 6 are cross-sectional views illustrating the method for manufacturing the wiring board according to the embodiment.

[0049] 4(a), a laminate is prepared which includes a core layer 100, a wiring layer 210, and a wiring layer 310. The core layer 100 includes an insulating base material 111 having a through hole 112 formed therein, and a conductive layer 113.

[0050] 4(b), an adhesion-enhancing film 270 is formed on the upper surface and side surfaces of the wiring layer 210, and an adhesion-enhancing film 370 is formed on the lower surface and side surfaces of the wiring layer 310. The adhesion-enhancing films 270 and 370 are formed using, for example, a silane coupling agent.

[0051] To form the adhesion-promoting films 270 and 370 using a silane coupling agent, for example, the structure shown in FIG. 4(a) may be immersed in a diluted solution of the silane coupling agent. The adhesion-promoting film 270 may be formed by spraying the diluted solution of the silane coupling agent onto the upper and side surfaces of the wiring layer 210 of the structure shown in FIG. 4(a), and the adhesion-promoting film 370 may be formed by spraying the diluted solution of the silane coupling agent onto the lower and side surfaces of the wiring layer 310. The concentration of the diluted solution of the silane coupling agent is 0.1% to 10%, preferably 0.5% to 5%. At this stage, the thickness of the adhesion-promoting films 270 and 370 may be, for example, approximately 20 nm to 30 nm at their thickest points. This is followed by sequential washing with water, partial removal of the adhesion-promoting films 270 and 370 using a removal treatment solution such as an acidic solution, and drying. As a result, the adhesion-promoting films 270 and 370 with thicknesses of approximately 3 nm to 8 nm are obtained.

[0052] After the adhesion-enhancing films 270 and 370 are formed, as shown in FIG. 4( c), an uncured resin film is attached to one surface of the core layer 100 so as to cover the wiring layer 210 and the adhesion-enhancing film 270, and an uncured resin film is attached to the other surface of the core layer 100 so as to cover the wiring layer 310 and the adhesion-enhancing film 370. Next, these resin films are heat-treated and cured to form the insulating layers 220 and 320. The insulating layers 220 and 320 are made of insulating resin such as epoxy resin or polyimide resin. The insulating layers 220 and 320 may also be formed by applying a liquid resin. The insulating layers 220 and 320 are an example of a first insulating layer.

[0053] 5(a), a via hole 412 reaching the wiring layer 210 is formed in the insulating layer 410 (insulating layer 220 and adhesion enhancing film 270), and a via hole 512 reaching the wiring layer 310 is formed in the insulating layer 510 (insulating layer 320 and adhesion enhancing film 370). In addition, a recess 215 is formed on one surface of the wiring layer 210, and a recess 315 is formed on the other surface of the wiring layer 310.

[0054] Next, as shown in FIG. 5(b), a wiring layer 230 is formed, which includes via conductors in the via holes 412 and the recesses 215 and a wiring pattern on one side of the insulating layer 220, and a wiring layer 330 is formed, which includes via conductors in the via holes 512 and the recesses 315 and a wiring pattern on the other side of the insulating layer 320.

[0055] Here, a description will be given of a method for forming the via hole 412, the recess 215, and the wiring layer 230. Figures 7 to 9 are cross-sectional views illustrating an example of a method for forming the via hole, the recess, and the wiring layer.

[0056] First, as shown in FIG. 7(a), the insulating layer 410 (insulating layer 220 and adhesion-enhancing film 270) is processed with a laser to form an opening 222 in the insulating layer 220 and an opening 272X in the adhesion-enhancing film 270. The opening 222 penetrates the insulating layer 220, and the opening 272X penetrates the adhesion-enhancing film 270. The openings 222 and 272X are formed so as to overlap with the wiring layer 210 in a plan view. The insulating layer 220 and the adhesion-enhancing film 270 may be processed using a drill. The opening 222 is an example of a first opening.

[0057] Next, a desmear process is performed. As a result of the desmear process, as shown in FIG. 7(b), the portion of the adhesion-enhancing film 270 exposed in the opening 272X is wet-etched through the opening 222, and an opening 272 wider than the lower end of the opening 222 is formed in the adhesion-enhancing film 270. The opening 272 overlaps with the wiring layer 210 in plan view. In this way, a via hole 412 including the openings 222 and 272 is formed in the insulating layer 410. The wiring layer 210 is exposed from the via hole 412. A sodium permanganate solution, for example, is used for the desmear process. The opening 272 is an example of a second opening.

[0058] In processing using a laser or a drill, it is not necessary to form the opening 272X in the adhesion enhancing film 270. Even if the opening 272X is not formed, the opening 272 can be formed by desmearing through the opening 222.

[0059] 7(c), the wiring layer 210 is wet-etched through the openings 222 and 272 to form a recess 215 on the upper surface 211 of the wiring layer 210. For example, sodium persulfate is used for wet etching the wiring layer 210.

[0060] When forming the recess 215, since the opening 272 is formed in the adhesion-enhancing film 270, the wiring layer 210 is wet-etched over a wider area from the initial stage compared to when the opening 272 is not formed. That is, wet etching is more likely to occur in the thickness direction. Furthermore, in the portion where the adhesion-enhancing film 270 remains, the etchant is less likely to penetrate into the interface between the wiring layer 210 and the adhesion-enhancing film 270 compared to the interface between the wiring layer 210 and the insulating layer 220 when the adhesion-enhancing film 270 is not used. That is, wet etching is less likely to occur in a direction parallel to the top surface of the wiring layer 210. For these reasons, the recess 215 having the above-described cross-sectional shape is formed.

[0061] 8(a), a seed layer 236 made of copper or the like is formed so as to directly cover the surface of the recess 215, the portion of the lower surface 411 of the insulating layer 410 exposed in the recess 215, the inner wall surface of the via hole 412, and one surface of the insulating layer 410. The seed layer 236 can be formed by, for example, sputtering or electroless plating.

[0062] 8(b), a plating resist layer 238 is formed on the seed layer 236. Thereafter, the plating resist layer 238 is exposed to light and developed, thereby forming openings 239 in the plating resist layer 238.

[0063] Thereafter, as shown in FIG. 9(a), a plating layer 237 made of copper or the like is formed in the openings 239 of the plating resist layer 238 by electrolytic plating using the seed layer 236 as a plating power supply path.

[0064] 9(b), the plating resist layer 238 is removed. Furthermore, the seed layer 236 is removed by flash etching using the plating layer 237 as a mask. In this manner, the wiring layer 230 including the seed layer 236 and the plating layer 237 is formed.

[0065] The via hole 512 and the wiring layer 330 can be formed in the same manner as the via hole 412 and the wiring layer 230 .

[0066] After the wiring layers 230 and 330 are formed, as shown in FIG. 5( c), an adhesion-enhancing film 280 is formed on the upper surface and side surfaces of the wiring layer 230, and an adhesion-enhancing film 380 is formed on the lower surface and side surfaces of the wiring layer 330. The adhesion-enhancing films 280 and 380 can be formed in the same manner as the adhesion-enhancing films 270 and 370. Next, an insulating layer 240 is formed on the insulating layer 220 so as to cover the wiring layer 230 and the adhesion-enhancing film 280. Furthermore, an insulating layer 340 is formed under the insulating layer 320 so as to cover the wiring layer 330 and the adhesion-enhancing film 380. The insulating layers 240 and 340 can be formed in the same manner as the insulating layers 220 and 320. The insulating layers 240 and 340 are an example of a first insulating layer.

[0067] 6(a), a via hole 422 reaching the wiring layer 230 is formed in the insulating layer 420 (insulating layer 240 and adhesion-enhancing film 280), and a via hole 522 reaching the wiring layer 330 is formed in the insulating layer 520 (insulating layer 340 and adhesion-enhancing film 380). Also, a recess 235 is formed on one surface of the wiring layer 230, and a recess 335 is formed on the other surface of the wiring layer 330. Next, a wiring layer 250 is formed, which includes the via hole 422 and the via conductor in the recess 235 and a wiring pattern on one surface of the insulating layer 240, and a wiring layer 350 is formed, which includes the via hole 522 and the via conductor in the recess 335 and a wiring pattern on the other surface of the insulating layer 340.

[0068] The via hole 422, the recess 235, and the wiring layer 250 can be formed in the same manner as the via hole 412, the recess 215, and the wiring layer 230. The via hole 522, the recess 335, and the wiring layer 350 can be formed in the same manner as the via hole 412, the recess 215, and the wiring layer 230.

[0069] 6(b), a solder resist layer 260 is formed on the insulating layer 240, and a solder resist layer 360 is formed under the insulating layer 340. After that, an opening 261 is formed in the solder resist layer 260, and an opening 361 is formed in the solder resist layer 360.

[0070] In this manner, the wiring board 1 according to the embodiment can be manufactured.

[0071] In the wiring substrate 1, when the portion between the first point 11 and the second point 12 on the surface of the recess 215 is approximated by a curve with only one inflection point 19, the angle θ1 of the first angle is smaller than 90 degrees, the angle θ2 of the second angle is larger than 90 degrees, and the angle θ3 of the third angle is larger than 90 degrees. Therefore, when forming the plating layer 237, the plating solution easily wets and spreads to the edge of the recess 215, and the recess 215 is easily filled with the wiring layer 230 including the seed layer 236 and the plating layer 237. In other words, gaps are less likely to remain in the recess 215. This improves the connection reliability between the wiring layer 210 and the wiring layer 230.

[0072] In particular, when angle θ1 is 10 degrees or more and 40 degrees or less, angle θ2 is 120 degrees or more and 160 degrees or less, and angle θ3 is 120 degrees or more and 160 degrees or less, the plating solution is likely to wet and spread to the edge of recess 215 when forming plating layer 237.

[0073] It may be difficult to distinguish between the adhesion enhancing film 270 and the insulating layer 220 in the wiring substrate 1. Even in such a case, the presence of the adhesion enhancing film 270 can be estimated from the presence of the second region 32 and the third region 33, which have different filler densities.

[0074] The planar shape of the via hole does not have to be circular. If the planar shape of the via hole is not circular, the center of a circle obtained by approximating the planar shape of the via hole may be used as the center in plan view.

[0075] Between the formation of the recess 215 by wet etching and the formation of the seed layer 236, a roughening treatment may be performed on the surface of the recess 215.

[0076] Although the preferred embodiments have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0077] 1. Wiring board 11 1st point 12 Second point 13 Third point 14 4th point 19 Inflection Point 21 First Line 22 Second line segment 23 Third line segment 31 First area 32 Second area 33 Third area 210, 230, 250, 310, 330, 350 wiring layer 211 Top surface 215, 235, 315, 335 recesses 220, 240, 320, 340 Insulation layer 222 Opening 270, 280, 370, 380 Adhesion-enhancing membrane 272, 272X opening 410, 420, 510, 520 Insulation layer 411 Bottom surface 412, 422, 512, 522 Beer Hall 413 Upper edge

Claims

1. a first wiring layer having a first surface on which a recess is formed; an insulating layer having a second surface opposite to the first surface and covering the first wiring layer; a via hole that overlaps the first wiring layer in a plan view and penetrates the insulating layer; a second wiring layer formed on the insulating layer and in contact with the first wiring layer through the via hole; and In a cross section including a center line of an upper edge of the via hole in a plan view, The surface of the recess is a first point located on an edge of the recess; a second point located on the center line; Including, When a portion of the surface of the recess between the first point and the second point is approximated to a curve with only one inflection point, a first angle between a first line segment connecting the first point and the third point and the second plane is smaller than 90 degrees; a second angle between a second line segment connecting the third point and the fourth point and the first line segment is greater than 90 degrees; a third angle between a third line segment connecting the fourth point and the second point and the second line segment is greater than 90 degrees; the third point is a point where the curvature is maximum between the first point and the inflection point, The fourth point is a point where the curvature is maximum between the second point and the inflection point.

2. the first angle is equal to or greater than 10 degrees and equal to or less than 40 degrees, the second angle is equal to or greater than 120 degrees and equal to or less than 160 degrees, The wiring board according to claim 1 , wherein the third angle is equal to or greater than 120 degrees and equal to or less than 160 degrees.

3. In the cross section, The first region of the insulating layer has a thickness of 2 μm or less based on the portion of the second surface of the insulating layer exposed in the recess, a second region including an inner wall surface of the via hole; a third region connected to the second region and positioned between the second region and the first point in a plan view; and The wiring board according to claim 1 , wherein the density of the filler in the second region is higher than the density of the filler in the third region.

4. forming a first wiring layer having a first surface; forming an adhesion enhancing film covering the first wiring layer; forming a first insulating layer on the adhesion-enhancing film; forming a first opening in the first insulating layer, the first opening overlapping the first wiring layer in a plan view and penetrating the first insulating layer; wet-etching the adhesion-promoting film through the first opening to form a second opening in the adhesion-promoting film, the second opening penetrating the adhesion-promoting film and being wider than a bottom edge of the first opening; wet-etching the first wiring layer through the first opening and the second opening to form a recess on the first surface; forming a second wiring layer on the first insulating layer, the second wiring layer contacting the first surface through the first opening and the second opening; A method for manufacturing a wiring board having the above structure.

5. The method for manufacturing a wiring substrate according to claim 4 , wherein the adhesion enhancing film contains a silane coupling agent.

6. 6. The method for manufacturing a wiring board according to claim 4, wherein an acid solution is used for wet etching the first wiring layer.

7. 6. The method for manufacturing a wiring board according to claim 4, wherein a sodium permanganate solution is used for wet etching the adhesion-enhancing film.

8. the insulating layer, which is a laminate of the adhesion-enhancing film and the first insulating layer, has a second surface facing the first surface; In a cross section including a center line of an upper edge of the first opening in a plan view, The surface of the recess is a first point located on an edge of the recess; a second point located on the center line; Including, When a portion of the surface of the recess between the first point and the second point is approximated to a curve with only one inflection point, a first angle between a first line segment connecting the first point and the third point and the second plane is smaller than 90 degrees; a second angle between a second line segment connecting the third point and the fourth point and the first line segment is greater than 90 degrees; a third angle between a third line segment connecting the fourth point and the second point and the second line segment is greater than 90 degrees; the third point is a point where the curvature is maximum between the first point and the inflection point, 6. The method for manufacturing a wiring board according to claim 4, wherein the fourth point is a point where the curvature is maximum between the second point and the inflection point.

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